fiat-cr42-db

FIAT CR.42 DB Fighter

By William Pearce

In late 1930s, FIAT developed the CR.42 Falco (Falcon), one of the last biplane fighter aircraft. The CR.42 was powered by an 840 hp (626 kW) FIAT A 74 RC38 radial engine. With good performance and excellent maneuverability, the CR.42 was one of the best biplane fighters ever built. However, frontline fighters had adopted new tactics in which speed controlled the fight, so the maneuverability of the biplane was traded for the speed of a monoplane. Looking to maximize a combination of speed and maneuverability, the Italian Air Ministry asked FIAT to re-engine the CR.42 with a 1,000 hp (746 kW) Daimler-Benz DB 601A engine. The resulting aircraft was designated CR.42 DB.

fiat-cr42-db

The FIAT CR.42 DB undergoing an engine run. Its Daimler-Benz DB 601 engine made the aircraft the fastest biplane ever built. However, its performance could not match contemporary monoplane fighters.

Some sources incorrectly list the DB 601-powered aircraft as the CR.42 B, which was a trainer built from a standard CR.42 by moving the engine forward, elongating the fuselage, and adding a second cockpit. Additionally, some sources claim the CR.42 DB’s engine was an Alfa Romeo RA 1000 RC41, which was a DB 601A built under license in Italy. However, the Alfa Romeo RA 1000 engine had not proceeded beyond initial testing by late 1941, after the CR.42 DB had already flown. It is unlikely that an untried RA 1000 test engine was installed in the CR.42 DB.

The FIAT CR.42 DB project was underway by early 1941. The aircraft was assigned serial number MM 469. In the span of a few weeks, a standard CR.42 was re-engined with the DB 601 power plant. Switching from a large, air-cooled, 14-cylnder radial engine to a long, liquid-cooled, V-12 engine necessitated many changes to the aircraft.

Like all CR.42s, the CR.42 DB consisted of a welded steel tube and alloy airframe. The fuselage was skinned in aluminum with the exception of the rear fuselage’s sides and bottom, which were covered with fabric. The wings and tail had a duralumin frame. The wings’ leading and trailing edges were aluminum, and fabric covered the rest of the surface. The horizontal and vertical stabilizers were aluminum-skinned. All control surfaces were had a duralumin frame and were covered in fabric.

FIAT CR42 DB right

The CR.42 DB with its lower wing removed. The removed bottom panel exposes some of the aircraft’s structure.

The entire front of the CR.42 DB was redesigned to accommodate the DB 601A engine and its radiator. The DB 601A was encased in a close-fitting, streamlined cowling. Positioned on the left side of the cowling was the engine’s air intake. Faired into the cowling’s upper deck were the blast tubes for the aircraft’s two 12.7 mm guns—each had 400 rounds of ammunition. A housing for the radiator was located under the engine. Scoops for oil coolers were placed in the wing roots of the lower wing (in the same location as a standard CR.42).

The CR.42 DB had the same 31.8 ft (9.70 m) upper and 21.3 ft (6.50m) lower wingspans as the standard CR.42, but those were the only specifications the two aircraft shared. The CR.42 DB was 1.8 ft (.54 m) longer at 28.9 ft (8.80 m). The aircraft was 507 lb (230 kg) heavier at an empty weight of 4,299 lb (1,950 kg). The CR.42 DB’s performance improved substantially over the standard CR.42. The CR.42 DB had a top speed of 323 mph (520 km/h) at 17,388 ft (5,300 m) and could climb to 16,404 ft (5,000 m) in 5:40. The aircraft had a ceiling of 34,777 ft (10,600 m) and a range of 715 mi (1,150 km). The standard CR.42 was 56 mph (90 km/h) slower, took an additional 1:40 to reach 16,404 ft (5,000 m), and had a 1,312 ft (400 m) lower ceiling.

FIAT CR42 DB color

This image shows the wing root scoop for the oil cooler and the induction scoop for the DB 601 engine. The CR.42 DB is shown at Caselle airfield in May 1941.

The CR.42 DB’s first flight was in March 1941, piloted by Commander Valentino Cus. The aircraft was delivered to the Centro Sperimentale (Experimental Center) at Guidonia Airfield (near Rome) for military tests in the summer of 1941. The CR.42 DB proved to be an exceptional aircraft; it was (and still is) the world’s fastest biplane. While not much slower than monoplane fighters then in service, the CR.42 DB’s speed could not be improved, whereas the speed of monoplane fighters would continue to increase as advancements were made.

Although an order for 150 aircraft was placed on 10 April 1941, series production was never started. The short supply of DB 601 engines available to Italy and the engine’s priority use in the more advanced Macchi MC.202 Folgore (Lightening) and Re.2001 Falco II (Falcon II) monoplane fighters left no DB 601s available for the CR.42 DB. Only one CR.42 DB was built. Some consideration was given to lengthening the CR.42 DB to 30.8 ft (9.38 m) and modifying it into a two-place training or reconnaissance aircraft. However, this project never proceeded beyond the initial design phase. Although the FIAT CR.42 DB was the pinnacle of biplane fighter performance, it was outclassed by frontline monoplane fighters as the era of biplane fighters came to an end.

FIAT CR42 P

The two-place, DB 601-powered CR.42. Some sources refer to the aircraft as the CR.42 R. However, the drawing appears to be labeled “R.42 P”. The “CR” stood for Caccia (Fighter) Rosatelli. Rosatelli was the aircraft’s designer, Celestino Rosatelli. Since the two-place aircraft was not a fighter, it makes sense that the “Caccia” designation would not be used.

Sources:
The FIAT Fighters 1930–1945 by Piero Vergnano (1969)
Italian Civil and Military Aircraft 1930–1945 by Jonathan W. Thompson (1963)
Aeronuatica Militare Museo Storico Catalogo Motori by Oscar Marchi (1980)
Tutti gli aerie del Re by Max Vinerba (2011)
– “Fantasmi di aerie e motori Fiat dal 1935 al 1945 (prime parte)” by Giovanni Masino Ali Antiche 106 (2011)
Fiat CR.42 Falco by Przemyslaw Skulski (2007)

Perrier-Cadillac 41-75 front

Perrier-Cadillac 41-75 Tank Engine

By William Pearce

As World War II started to gain momentum and become a global conflict, Australia realized that it was in a precarious position. In the war’s early years, Australia did not have an industry devoted to building war material, and the ability of other nations to supply war machines to Australia was in doubt. Australia realized that they would need to develop their own war equipment. In November 1940, Australia began developing its own tank, the Australian Cruiser Tank Mark I (AC1).

AC1 Clover leaf Cadillac

The “clover leaf” Cadillac drive system of the Australian Cruiser Tank Mark I. The rear engine (top of image) is not visible, but its long drive shaft can be seen passing between the other two engines. All three drive shafts connect to the transfer box (bottom of image).

The AC1 Sentinel was based on the United States M3 medium tank, but selecting a power plant for the AC1 proved to be a challenge. The M3 was powered by a 400 hp (298 kW) Wright R-975 radial engine, built under license by Continental Motors. But a continuous supply of R-975 engines, Guiberson diesel engines, or any powerful engines could not be assured to Australia. A solution was found in the unlikely form of a Cadillac V-8 engine originally used to power various coupes and sedans. The Australians referred to the engine as the Cadillac 75 because of its use in the Cadillac Series 75 sedan, but it was also used in the Series 70 and various Series 60 automobiles.

The Cadillac 75 engine had made its debut in 1936. It was a flat head (side valve) engine with the intake and exhaust valves located on the Vee side of the cylinder. The engine was a monobloc design with cylinder banks cast integral with the crankcase. The V-8 also incorporated hydraulic valve lifters for durability. The engine was designed to be built more economically than Cadillac’s V-12 and other V-8 engines. The Cadillac 75 engine had a 3.5 in (89 mm) bore, a 4.5 in (114 mm) stroke, and a displacement of 346 cu in (5.7 L). It produced 135 hp (101 kW) and weighed around 890 lb (404 kg).

Australian Cruiser Tank Mark III

The Australian Cruiser Tank Mark III (AC3) powered by the Perrier-Cadillac 41-75 engine. Only one AC3 was fully assembled, and that tank is currently preserved at the Australian War Memorial in Campbell, Australia. (Australian War Memorial image)

The Cadillac 75 engine was readily available for import to Australia, but its 135 hp (101 kW) output was insufficient to power the 28 ton (25.4 metric ton) AC1 tank. As a result, AC1 designers, Colonel W. D. Watson and A. R. Code, decided to use three engines to power the tank. Watson was a British tank engineer on loan to Australia, and Code was the Director of Australia’s Armored Fighting Vehicle Production. The three-engine power package developed for the AC1 tank became known as a clover leaf arrangement and was built by General Motors’ Holden subsidiary in Melbourne.

In the clover leaf configuration, engine “3” was situated toward the rear of the tank, and engines “1” and “2” were located amidships, side-by-side. The engines were completely independent of one another, each having its own radiator and drive shaft. However, engine “3” also drove the cooling fan from six pulleys mounted on its driveshaft. The drive shafts for all three engines extended forward to a common transfer box near the middle of the tank. From the transfer box ran the final output shaft that connected to the tank’s gearbox. The AC1 tank could be run on two or even one of the Cadillac 75 engines.

Perrier-Cadillac 41-75 front

Front view of the Perrier-Cadillac 41-75 engine illustrates the odd cylinder bank arrangement. Note the single output shaft and how each exhaust manifold collects exhaust from three cylinder banks. A water pump and generator are driven from a belt at the front of each engine section.

The clover leaf Cadillac power package produced 330 hp (246 kW) at 3,050 rpm and was somewhat successful, powering 65 AC1 tanks. However, the rear engine did experience occasional cooling issues as a result of unequal coolant flow. The clover leaf’s three drive shafts, remote transfer box, and separate cooling systems added weight and complexity. As the Australian Cruiser Tank Mark III (AC3) was being designed in 1941, engineer Robert Perrier sought to simplify the clover leaf Cadillac power package. Perrier, a Frenchman, had been sent to Japan by the French government in 1940 and had subsequently made his way to Australia as Japan entered the war.

The AC3 Thunderbolt was an improved AC1 with better armor protection and firepower. To increase the performance of the three Cadillac 75 engines, Perrier mounted them radially to a common crankcase made from steel plates welded together. One engine was mounted on top of the crankcase, and the other two were mounted about 60 degrees to the left and right of the top engine. This configuration resulted in a rather odd looking engine, with its lower cylinder banks some 210 degrees apart. The engine was known as the Perrier-Cadillac 41-75; it was a lighter, more compact power package than the clover leaf configuration.

Perrier-Cadillac 41-75 crankcase

Rear view of the triangular, welded-steel crankcase of the Perrier-Cadillac engine. The power from all three engine sections was combined at the rear of the engine, and a single output shaft passed though the large, circular openings in the crankcase.

The Perrier-Cadillac engine had a single cooling system with one radiator, but each engine section had its own water pump. The remaining engine accessories were separate and operated independently of one another. At the rear of the Perrier-Cadillac engine, the crankshaft of each engine section was coupled to a common combining gear. The individual engine sections could be decoupled from the combining gear. A drive shaft extended from the combining gear at the rear of the engine, through the crankcase, and out the front of the engine.

The single output shaft of the Perrier-Cadillac engine allowed the transfer box used in the AC1 tank to be omitted, saving space and weight. The single output shaft also decreased mechanical losses, enabling the Perrier-Cadillac to produce more power than the clover leaf package with its three-into-one transfer drive arrangement. The 24-cylinder Perrier-Cadillac 41-75 displaced 1,039 cu in (17.0 L) and produced 397 hp (296 kW). The engine weighed around 3,000 lb (1,360 kg).

Perrier-Cadillac 41-75 rear

Rear view of the 397 hp (296 kW) Perrier-Cadillac engine. Behind the cover at the center of the engine is where the individual engine sections are connected to the single output shaft.

While the Perrier-Cadillac engine worked well, it did not go into production. A number of AC3 tanks were being built, but only one of these was fully assembled. The further improved Australian Cruiser Tank Mark IV (AC4) design followed, and it also used the Perrier-Cadillac engine. By 1943, the supply of war equipment to Australia had not been greatly impacted by the war, and equipment was imported faster than it could be domestically built. Australian resources were better utilized on projects other than tanks, and the Australian Cruiser tank programs were cancelled. However, the imported tanks did not completely match the Australian Cruiser tank design requirements, nor did they eclipse the Australian Cruiser tanks’ performance.

As a side note, the Perrier-Cadillac 41-75 was not the only engine intended to power AC4. A new engine was under development; it was comprised of four air-cooled, four-cylinder de Havilland Gypsy Major engines mounted in an H configuration on a common crankcase. Starting in 1941, Gypsy Major engines were produced under license at General Motors’ Holden plant. With its 4.65 in (118 mm) bore and 5.51 in (140 mm) stroke, the Quad-Gypsy engine would have displaced 1,495 cu in (24.5 L) and produced 510 hp (380 kW) at 2,500 rpm. The 16-cylinder engine weighed around 1,500 lb (680 kg). The Quad-Gypsy engine was domestically-built, simpler, more powerful, and much lighter than the Perrier-Cadillac engine.

AC4 QuadGipsy engine

The 16-cylinder, QuadGipsy engine would provide around 510 hp (380 kW) for the Australian Cruiser Tank Mark IV. Lighter and more powerful that the Perrier-Cadillac, the engine would have been built in Australia by General Motors-Holden. Concealed in the shroud around the output shaft was a fan to force air through the cylinders’ cooling fins. Various accessories were mounted on top the engine.

While similar engine concepts, no direct relation has been found between the Perrier-Cadillac and the Chrysler A57 Multibank.

Sources:
Tanks Australian Cruiser Mark-1 Instruction Book (1943)
Australian Sentinel and Matildas (AFV Weapons 31) by Major James Bingham
The Role of Science and Industry (Australia in the war of 1939-1945) by D.P. Mellor (1958)
http://www.mheaust.com.au/Aust/Research/Sentinel/sentinelmk.htm
http://www.secretprojects.co.uk/forum/index.php/topic,8514.0/all.html
http://forum.worldoftanks.com/index.php?/topic/490738-inside-the-chieftains-hatch-ac-1-sentinel/

Martin-Baker MB3 runup

Martin-Baker MB3 Fighter

By William Pearce

By 1939, it was clear that the British Air Ministry would not order the Martin-Baker MB2 into production. James Martin (main designer) and Captain Valentine H. Baker had already been at work designing a new fighter aircraft—the MB3. Since the MB2 had proved to be a well-designed fighter, the British Air Ministry ordered three prototypes of the MB3 fighter on 16 June 1939. The new aircraft would be built under Specification F.18/39, issued to Martin-Baker in May 1939. The minimum requirements of Specification F.18/39 were a speed of 400 mph (644 km/h) at 15,000 ft (4,572 m), a ceiling of 35,000 ft (10,668 m), an endurance of 2.5 hours, and an armament of four 20 mm cannons. With the contract issued, Martin worked to finalize the MB3’s design.

Martin-Baker MB3 Denham guns

The nearly complete Martin-Baker MB3 in the summer of 1942 at Martin-Baker’s factory in Denham. The aircraft is not painted, and its six 20 mm cannons are installed. The cannons were removed before flight testing.

The timetable for completing the aircraft was rather optimistic for the relatively small Martin-Baker company. The original contract stated the first MB3 prototype was to be ready by 15 December 1939, with the two remaining aircraft completed by 15 February 1940. At this early stage, the aircraft was to be powered by a Rolls-Royce Griffon engine. By September 1939, it was apparent that the Griffon engine would not be available to Martin-Baker for some time. At the insistence of the Air Ministry, the Napier Sabre replaced the Griffon, and the entire aircraft was redesigned for the new engine. This resulted in a new contract that was somewhat delayed but ultimately signed on 11 August 1940. Britain was now fully involved in World War II, and Martin-Baker was inundated with other work of a higher priority. Therefore, completing the first MB3 took longer than anticipated. By the end of 1941, Martin-Baker was informed that there would be no production orders for the MB3, but the first prototype was so far along that it made sense to finish it.

Construction of the Martin-Baker MB3 followed the established company practice of using a tubular steel frame to make up the fuselage structure. The main wing spar was made of laminated steel, with the number of laminations decreasing near the wingtips. The rest of the wing structure formed a torsion box of extreme rigidity. The entire aircraft was covered with stressed aluminum skin, but many panels could be opened or removed for quick access to equipment and armament. The rudder was fabric-covered, but the rest of the control surfaces were skinned with aluminum.

Martin-Baker MB3 left

The MB3 during its brief flight testing career at RAF Wing. Note the retractable stirrup and fold-down door for cockpit entry.

The aircraft used pneumatically controlled split flaps and had spring loaded aileron gap seals to increase its roll rate and improve aerodynamics. The elevator also had gap seals. Fuel was carried in a fuselage tank in front of the cockpit. The aircraft’s fully retractable main landing gear had a wide track of 15 ft 5 in (4.7 m). The tailwheel retracted into an open well under the tail. The landing gear was lowered by gravity and raised by a pneumatic system, which was separate from the system that controlled the flaps.

Each wing housed three 20 mm cannons with 200 rpg, all installed outside of the aircraft’s main gear. The ammunition belts were installed parallel to the cannons; each bullet had to turn 90 degrees before being fed into the breach. This “flat-feed” ammunition system was patented by Martin. The cannon and ammunition arrangement made for a compact package that could be easily accessed and quickly serviced. With its six 20 mm cannons, the MB3 was one of the most heavily armed fighters of World War II.

Martin-Baker MB3 runup

This image of the MB3 running up gives a good view of the aircraft’s wide-track landing gear and the close-fitting cowling that covered the Sabre engine. Also visible are the under-wing scoops for the radiator and oil cooler.

The Rolls-Royce Vulture X-24 engine was also considered to power the MB3. The V-12 Griffon was initially selected because it was a far less complex power plant than the Vulture or Sabre. However, because the Sabre was more readily available than the Griffon and was favored by the Air Ministry, it was ultimately selected to power the MB3. The 2,020 hp (1,506 kW) Sabre II engine had 24 cylinders arranged in a horizontal H configuration and used sleeve valves. The engine drove a three-blade de Havilland propeller that was 14 ft (4.27 m) in diameter. Engine cooling was provided by a radiator installed in the right wing and an oil cooler installed in the left wing. The radiator ran from the wing root to the main gear, and the oil cooler was about half the size of the radiator. The scoops for the radiator and oil cooler extended about 5 in (127 mm) under the wings and were positioned between the gear wells and the flaps.

The MB3 had a 35 ft (10.7 m) wingspan and was 35 ft 4 in (10.8 m) long. The aircraft had a gross weight of 11,497 lb (5,215 kg). The MB3 had a top speed of 418 mph (673 km/h) at 20,000 ft (6,096 m). However, Martin claimed that Captain Baker had achieved 430 mph (632 km/h) at the same altitude, albeit without the drag that the six cannons would produce. At sea level, the aircraft was capable of 372 mph (599 km/h), and maximum cruising speed was 370 mph (595 km/h) at 15,000 ft (4,572 m). The MB3’s landing speed was 88 mph (142 km/h). The aircraft had a service ceiling of 35,000 ft (10,668 m) and a range of approximately 420 miles (676 km).

Martin-Baker MB3 rear

This rear view of the MB3 illustrates the aircraft’s fine fit and finish. The aileron and elevator gap seals can just be seen.

The first MB3 was given the serial number R2492. The aircraft was expected in March 1942 but was not completed until early August. The aircraft was trucked to Royal Air Force Station Wing (RAF Wing) in Buckinghamshire for flight testing. Surrounded by small fields and many trees, the small airbase of RAF Wing was not an ideal location for flight testing. Martin had objected to using RAF Wing, but the Air Ministry insisted.

Captain Baker was at the controls when the MB3 flew for the first time on 31 August 1942. The six wing cannons had been installed when the aircraft was built at Denham (near London) but were removed before the aircraft flew and were never reinstalled. Ballast had been added to simulate the weight of the cannons and their ammunition. Flight testing revealed that the aircraft had excellent maneuverability and handling characteristics. However, difficulty was experienced with the Sabre engine, and engine overheating issues troubled the MB3.

Martin-Baker MB3 right rear

Many sources claimed that the MB3 was fitted with a bubble canopy after its first flight. This belief stems from a doctored image of the MB3 with a bubble canopy meant to illustrate what the production version of the aircraft would look like. A bubble canopy was never installed on the MB3.

On 12 September 1942, the aircraft made its 10th flight. Captain Baker had just taken off when the engine seized, a result of a sleeve drive crank failure. Low to the ground and without any options, Captain Baker put the MB3 down in one of the many small fields lined with hedgerows and other obstacles surrounding RAF Wing. The aircraft clipped a pile of straw and crashed through a hedgerow at high speed. The MB3 cartwheeled, broke apart, and caught fire. Captain Baker was killed instantly.

The death of Captain Baker was a bitter blow for the Martin-Baker company. Martin took it especially hard; he had lost his friend in an aircraft powered by an engine he did not want to use and at a test site that he thought was inadequate. It was not long before Martin and the Martin-Baker company began work to improve aircrew safety and developed a series of ejection seats, which the company still manufactures today.

Martin-Baker MB3 with Captain V H Baker

Captain Valentine H. Baker poses with the MB3 shortly before a test flight. The engine seized on the MB3’s 10th flight, and Captain Baker was killed during the subsequent crash landing.

With the first MB3 prototype destroyed, Martin’s attention turned to the partially completed second prototype (R2496). Construction of the third prototype (R2499, or possibly R2500) was probably never started. Martin had already designed the MB3A, which was the production version of the MB3. The MB3A had a bubble canopy (that was never fitted to the prototype), and its cockpit was moved slightly forward to improve the pilot’s view over the wing. The MB4 had also been designed; it used a Bristol Centaurs engine in the same basic MB3 airframe. However, since the Air Ministry was finally willing to provide Martin-Baker with a Griffon engine and with the MB3’s performance now on par with existing aircraft, Martin sought to redesign the entire aircraft as the improved MB5 fighter. The Air Ministry was agreeable, and serial R2496 was reallocated to the MB5 aircraft in late 1943. The MB5 flew in 1944 and was another outstanding aircraft. However, the MB5 never went into production, and it was the last aircraft built by Martin-Baker.

Sources:
– “Martin-Baker Fighters,” by Bill Gunston, Wings of Fame Volume 9 (1997)
British Experimental Combat Aircraft of World War II by Tony Buttler (2012)
RAF Fighters Part 2 by William Green and Gordon Swanborough (1979)
The British Fighter since 1912 by Francis K. Mason (1992)
Interceptor Fighters of the Royal Air Force 1935–45 by Michael J. F. Bowyer (1984)
https://picasaweb.google.com/109207897425941419378/MartinBakerAircraft

Antoinette VII with 100hp V-16 engine paris 1909

Antoinette (Levavasseur) Aircraft Engines

By William Pearce

Léon Levavasseur was one of those rare geniuses of early aviation who designed and built engines as well as aircraft. In the early 1900s, Levavasseur gave up his career as an electrical engineer to focus on aviation. He needed funding to pursue his interests, so in August (some say July) 1902, Levavasseur approached industrialist and fellow Frenchman Jules Gastambide. Levavasseur had impressed and then befriended Gastambide when he repaired generators at one of Gastambide’s power plants. At the July meeting, Levavasseur outlined his plans for an aircraft of his design to be powered by a new engine that he was also designing. Levavasseur suggested the new enterprise should be named Antoinette, after Gastambide’s young daughter. Gastambide was interested but thought the engine should be built first, as no aircraft had yet flown. Levavasseur was agreeable, and with financial backing secured, he set to work on the new engine.

Antoinette IV 50hp V-8 Latham Levavasseur Camp Chalons 5 June 1909

An Antoinette mechanic (left), Hubert Latham (middle), and Léon Levavasseur (right) with an Antoinette IV aircraft powered by a 50 hp (37 kW) Antoinette V-8 at Camp de Châlons in early June 1909. At the event, Latham flew continuously for 1:07:37, setting a French endurance record. Note the condenser under the aircraft’s wing.

Levavasseur quickly returned to Puteaux (near Paris), France, and set up a shop to work on the new engine. On 28 August 1902, Levavasseur applied for a secret patent on his engine, which consisted of eight cylinders laid out in a Vee pattern, forming two banks of four cylinders. This patent application became public on 28 August 1903 and was granted French patent no 399,068 on 30 September 1904.

From 1902 through 1910, Levavasseur produced several different Antoinette engines, but they all used the same basic layout. Technically, the first time the “Antoinette” name was applied during the Levavasseur-Gastambide partnership was in 1905 when a series of boats were so named. It would not be until 1906 that the Société Anonyme Antoinette was officially incorporated.

All of Levavasseur’s engines consisted of individual, water-cooled cylinders arranged in a 90 degree Vee on an aluminum crankcase. The cylinders were staggered on the crankcase to facilitate the use of side-by-side connecting rods. With this arrangement, the connecting rods for each left and right cylinder pair attached to the crankshaft on the same crankpin. This allowed the engine to be much shorter than if each connecting rod had its own crankpin. The connecting rods were of a tubular design, and the pistons were made from cast iron.

Cody Antoinette 50hp V-8 Nulli Secundus 1907

A 1907 image of Samuel Cody with a 50 hp (37 kW) Antoinette V-8 in the framework of the “Nulli Secundus,” Britain’s first airship.

Each cylinder had one intake and one exhaust valve positioned on the Vee side of the cylinder. The intake valve was situated above the exhaust valve, creating an “F-head” or “Intake Over Exhaust” (IOE) cylinder head. The intake valve was atmospheric (automatic)—drawn open by the vacuum created in the cylinder as the piston moved down. The exhaust valve was actuated by a pushrod driven by the camshaft located in the Vee of the engine. The top of the cylinder’s combustion chamber was hemispherical, with a single spark plug positioned at its center.

The Antoinette engines used a primitive type of direct fuel injection. A belt-driven fuel pump at the rear of the engine fed fuel into a small reservoir (injector) located above each intake valve. When the intake valve opened, the suction that drew in air also pulled in fuel from the reservoir via a narrow, capillary passageway .008 in (.2 mm) in diameter. By manipulating the fuel pump, the pilot could exert a certain degree of fuel flow regulation. However, the system had some issues, and Antoinette engines had difficulty running at low rpm. In addition, the small passageways in the “injectors” easily became clogged by impurities in the fuel. These complications led some Antoinette operators to convert the engine to a carbureted induction system.

To cool a normal Antoinette engine, a belt-driven water pump at the rear of the engine provided water to an inlet at the base of each cylinder on the outer side of the engine. The water then passed up through the water jacket and along the cylinder barrel. The water exited the top of the cylinder on the Vee side of the engine, where it flowed into a common manifold for each cylinder bank. The water was then taken to a radiator or to a reservoir tank, as engine cooling was not critical on very short flights.

Antoinette 50hp V-8 London Science Museum

This 50 hp (37 kW) Antoinette V-8 engine is on display at the Science Museum in London and may have been used by Cody in 1908 for the first flight in Britain. Note the aluminum cylinder heads, brass water jackets, and copper water manifolds. The fuel distributor can be seen on each vertical intake pipe. (Warbird Tails image)

For lubrication, oil was taken from the crankcase and pumped through a pipe inside the crankcase, just above the camshaft. The pipe ran the length of the engine and was pierced with numerous small holes. Oil sprayed from the pipe, lubricating all of the engine’s internal components. Any components not in direct contact with an oil spray were lubricated by the oil mist created inside the crankcase.

Some (but not all) of the Antoinette engines had the ability to reverse their running. This was particularly helpful for braking and maneuvering in dirigibles. The camshaft was normally locked into its driving gear at the rear of the engine. With the engine stopped, the camshaft could be unlocked, rotated 90 degrees, and locked into a second position in its driving gear. One position was for normal (counter-clockwise) rotation, and the other was for reverse rotation (clockwise).

Antoinette engine ad V-16

Antoinette engine ad circa 1907 illustrating the lightness of the 220 lb (100 kg), 100 hp (75 kw) V-16 engine.

Each Antoinette engine was made to the highest standards in a shop that boasted of tolerances down to .0004 in (.01 mm). Another feature of all Antoinette engines was that their components were engineered to be just strong enough for their individual tasks. By designing parts with operating stresses in mind, all extra material could be eliminated, resulting in complete engines that were much lighter than their contemporaries. This design philosophy also had a drawback: engine reliability could suffer because parts were more easily overstressed, resulting in a failure. Antoinette engines were relatively specialized, and when one was in need of repair, it had to be shipped back to the factory.

The early Antoinette engines used open cylinder barrels made from cast iron. An aluminum cylinder head was bolted to the barrel. Each cylinder had a spun brass water jacket shrink-fitted to the cylinder head. The engine’s spark plugs were fired by a battery-powered ignition coil distributor.

Levavasseur’s first engine was running by the end of 1902, but efforts to improve the engine were undertaken throughout 1903. The engine was a V-8 with a 5.12 in (130 mm) bore and stroke. The engine’s total displacement was 842 cu in (13.8 L), and it produced 80 hp (60 kW). Initially, the engine weighed 346 lb (157 kg), but refinements brought the weight down to 320 lb (145 kg).

Antoinette V-16 engine display

An Antoinette V-16 engine possibly in storage at the Musée de l’Air et de l’Espace in Le Bourget, France. Note how the V-16 utilized all the same components as the V-8, with the exception of the crankcase, crankshaft, camshaft, and water manifolds. This engine has rather unusual exhaust stacks. (image source)

The 80 hp (60 kW) Levavasseur engine underwent a military test in March 1903 in which it produced 63 hp (50 kW). This output was derived by using a alternative power calculation method, and Levavasseur objected to the results. A little later, the engine was tested again, using another power calculation method. During this test, the engine registered an output of 82 hp (61 kW). The engine’s performance and Levavasseur’s ideas sufficiently impressed General Louis André, France’s Minister of War, who then provided 20,000 Francs of secret funds to Levavasseur for the construction of his airplane.

From July to September 1903, Levavasseur built his airplane in Villotran, France, which is why the aircraft became known as the Aéroplane de Villotran. The aircraft was powered by the 80 hp (60 kW) engine. Unfortunately, the aircraft proved incapable of flight. By 15 September 1903, Levavasseur had decided the aircraft was a failure; the engine was removed, and the aircraft was burned.

Antoinette V-24 marine engine

The 360 hp (268 kW) Antoinette V-24 marine engine of 1906. Unlike the V-16 engines, the V-24 appears to be comprised of V-8 engine sections. The engine is labeled as follows: A) air intake pipe; B) exhaust; C) cooling water outlet; D) aluminum cylinder head; E) steel cylinder covered with a brass water jacket sleeve; F and G) ignition distributors; H) spark plug; h) cylinder head bolts; I) fuel distributor to the intake valve; J) cooling water inlet; K) cylinder mounting bolt; P) engine mounting flange; S and T) gears for the ignition distributors; U) crankshaft gear; V) camshaft gear.

The Aéroplane de Villotran’s failure to fly, and the fact that no other aircraft had yet flown, made the concept of an aircraft engine seem futile. However, Levavasseur and Gastambide knew the engine held great potential and turned to motorboat racing as a way for the engine to prove its worth. From 1904 through 1906, Levavasseur’s engines powered a number of motorboats that achieved various distance speed records. It was to some of these motorboats that the “Antoinette” name was first given. In some cases, V-8 engines were coupled in tandem to create a more substantial power unit. By 1908, the Antoinette company had ended its support for motorboat racing and focused on using its engines only for aviation.

In 1904, while his engine was beginning to gain fame, Levavasseur designed other engines. Using the 80 hp (60 kW) V-8 as a foundation and maintaining the 5.12 in (130 mm) bore and stroke, Levavasseur designed V-16, V-24, and V-32 engines. Levavasseur believed that engines with many cylinders created frequent power pulses that smoothed out the engine’s operation and caused less stress on its internal components. The V-16 displaced 1,685 cu in (27.6 L) and produced 155 hp (116 kW). The V-24 displaced 2,527 cu in (41.4 L) and produced 225 hp (168 kW). The V-32 was most likely never built, but it would have displaced 3,370 cu in (55.2 L) and produced around 300 hp (224 kW).

Bleroit IX 50hp V-16 1908

A Bléroit IX aircraft under construction in 1908 with a 50 hp (37 kW) Antoinette V-16 installed in its frame. From left to right, the Bléroit mechanics are Louis Peyret, Louis Paragot, M. Pelletier, Alfred Bertrand, and Julien Mamet.

Levavasseur also varied the bore and stroke to make engines of different sizes and power. In 1905, Levavasseur built a V-8 Antoinette engine with a 3.15 in (80 mm) bore and stroke for aviation pioneers Ferdinand Ferber and Alberto Santos-Dumont. The engine displaced 196 cu in (3.2 L) and produced 24 hp (18 kW). The engine went through some refining and eventually weighed only 79 lb (36 kg). Another V-8 used a 4.13 in (105 mm) bore and stroke to displace 444 cu in (7.3 L). This engine produced 50 hp (37 kW) and weighed 176 lb (80 kg). The engine was approximately 32 in (.81 m) long, 24 in (.62 m) wide, and 22 in (.55 m) tall. A large V-8 was also built with a 7.87 in (200 mm) bore and stroke. Undoubtedly for marine use, this engine displaced 3,067 cu in (50.3 L), produced 200 hp (149 kW), and weighed 838 lb (380 kg).

In 1906, Levavasseur built a large V-24 Antoinette engine for marine use. The V-24 had a 5.91 in (150 mm) bore and stroke and displaced 3,882 cu in (63.6 L). The engine produced 360 hp (268 kW) and weighed some 1,322 lb (600 kg). Some sources say this engine was too heavy for the intended boat, which ended up sinking. The specifics of this incident have not been found.

Antoinette 50hp V-8 engine Krakow

A later model 50 hp (37 kW) Antoinette V-8 with an extended propeller shaft on display at the Muzeum Lotnictwa Polskiego in Krakow, Poland. Note the different lengths of the air intake pipes and that the water jackets are made from copper. (Alan Wilson image)

An Antoinette automobile made its debut in the 1906 Salon de l’Automobile in Paris, and some Antoinette engines were built for automotive use, these being a slightly different design and heavier than the aviation engines. Adams Manufacturing Company in London built a small number of the automotive engines under license for cars they were manufacturing.

By 1907, V-16 versions of the 3.15 in (80 mm) bore/stroke and 4.13 in (105 mm) bore/stroke engines were being built. The 3.15 in (80 mm) bore and stroke V-16 displaced 393 cu in (6.4 L), produced 50 hp (37 kW), and weighed around 143 lb (65 kg). The 4.13 in (105 mm) bore and stroke V-16 displaced 888 cu in (14.5 L), produced 100 hp (75 kW), and weighed 220 lb (100 kg). The 100 hp V-16 engine’s approximate dimensions were 55 in (1.40 m) long, 24 in (.62 m) wide, and 22 in (.55 m) tall.

Antoinette engines circa1907

The basic specifications of various Antoinette engines available circa 1907.

In addition to the V-16 engines listed above, Levavasseur offered Antoinette V-8 engines with five bore/stroke combinations. The V-8 engines had bores/strokes of 3.15, 4.13, 5.12, 5.91, or 7.87 in (80, 105, 130, 150, or 200 mm); the smallest two were mainly used for aviation.

It seems that around 1908 Levavasseur ceased experimenting with different engines and began working to refine the popular types. Levavasseur incorporated many changes to the Antoinette engines, but not all of the changes were applied at the same time. An elongated propeller shaft housing of approximately 12 in (.30 m) was cast integral with the crankcase. This feature made for a very aesthetically pleasing installation when the engine was used in an Antoinette aircraft. The battery-powered coil ignition was replaced by an accumulator and high-frequency distributor. A new one-piece, steel cylinder was used in which the cylinder head was integral with the cylinder barrel. This construction allowed for a higher compression ratio. New one-piece water jackets made of either brass or copper surrounded the new cylinders. The water jacket was unusual in that it was made by electrolytically depositing metal onto a wax mold that had been coated with graphite as a conductive material. The wax was then melted out, leaving a formed water jacket as thin as .04 in (1 mm). While this method of construction could yield perfect parts, it was expensive, and there was a high rejection rate because of irregularities in the water jacket wall.

Antoinette VII with 100hp V-16 engine paris 1909

Antoinette VII aircraft with a 100 hp (75 kW) V-16 engine displayed at the Salon de l’Aeronautique in 1909. Most sources indicate the condenser used aluminum tubes and copper side manifolds, details that this image seems to support.

By 1908, Levavasseur had perfected a zero-loss steam-cooling method for the Antoinette engines that were installed in Antoinette aircraft. The system used the same basic routing as the normal cooling system, but the water was allowed to boil in the water jackets. The steam was then collected and sent to a water separating tank. From the tank, the steam was sent though large condensers made of aluminum tubing with copper side manifolds. The condensers were positioned horizontally on each side of the aircraft. The steam condensed back to water and was routed back to the separating tank by a second pump. From the separating tank, the water was pumped back to the engine. The system condensed .26 gallons (1 L) of water per minute, and its capacity was 3.17 gallons (12 L). By reducing the amount of water needed, the steam-cooling method weighed less than conventional water-cooling.

Four Antoinette engines were displayed at the first Paris Salon de l’Aeronautique, starting in December 1908. A V-8 and V-16 were still offered with bores and strokes of 3.15 in (80 mm). However, the engines’ weights had increased to 93 lb (42 kg) for the V-8 and 165 lb (75 kg) for the V-16. The other two engines were a V-8 and V-16 with a bore of 4.33 in (110 mm) and a stroke of 4.13 in (105 mm). The V-8 engine displaced 487 cu in (8.0 L) and weighed 209 lb (95 kg). The V-16 engine displaced 974 cu in (16.0 L) and weighed 264 lb (120 kg). Some sources list the larger bore engines as producing 50 hp (37 kW) and 100 hp (75 kW) respectively. However, other sources give the outputs as 67 hp (50 kW) and 134 hp (100 kW). Note that the kW values (50 and 100) of the second figures match the hp values of the first figures. Possibly a printing error, the higher power figures have been found in fairly early publications and have been repeated a number of times over the years. The weight increases for all four engines were a result of strengthening components to increase Antoinette engine reliability.

Antoinette 50hp V-8 close up

A late model 50 hp (37 kW) Antoinette V-8 on display in the Musée de l’Air et de l’Espace. Note that this engine used brass water jackets; the piping and water manifolds were made from copper. (Aerofossile2012 image)

Alberto Santos-Dumont, Paul Cornu, Louis Blériot, Gabriel and Charles Voisin, Henri Farman, Léon Delagrange, Samuel Cody, and Hubert Latham are just some of the pioneers who used Antoinette engines to power their flying machines and themselves into the record books. Outside of the Wright brothers, almost all early aviation “firsts” were achieved in machines powered by an Antoinette engine. It was a 100 hp (75 kW) V-16-powered Antoinette aircraft that Latham flew during the aviation meet at Reims, France in August 1909 and for the Gordon Bennett Cup at Belmont Park, New York in October 1910.

With the success of the engine, Levavasseur began to focus entirely on building aircraft. From 1908 on, little engine development was undertaken to keep the Antoinette engines at the forefront of aviation. The Antoinette aircraft were built with the same spare-no-expense mentality as the engines, which resulted in them being priced far above the competition. To make matters worse, the aircraft proved to be a challenge to fly. At the same time, other engine manufactures closed the developmental gap, and the expensive Antoinette engines were no longer the coveted power plant they once were. These factors conspired to put the Antoinette company out of business in 1912.

Latham Antoinette VII 100hp V-16 NY 1910

Latham’s 100 hp (75 kW) V-16-powered Antoinette VII aircraft at Belmont Park, New York in October 1910 for the Gordon Bennett Cup. Note the length of the condenser, which extends some 13 ft (4 m) along the side of the aircraft.

While Levavasseur was most likely the first to build a V-8 engine, it is a near certainty that he was the first to create V-16 and V-24 engines. Very little information can be found regarding the V-24 marine engine. Some sources state that Levavasseur also built a V-32 intended for marine use, while other sources claim the engine did not proceed past the design phase.

Some sources state that Levavasseur also built V-12 and V-20 engines. These engines, especially the V-20, depart from Levavasseur’s known engine layout with a V-8 at its core. While no photographs of Levavasseur’s V-12 (or V-32) engine have been found, the V-20 engine does still exist (albeit as a table). The V-20’s cylinders, valves, and valve train do not match any other engine built by Levavasseur. There was a commonality of components and configuration from Levavasseur’s earliest engine of 1903 to his last of circa 1910. The components that make up the V-20, reportedly built in 1905, are unique to that engine and are not common with any other Levavasseur engine. This component incompatibility would lead some to conclude that the V-20 engine was not built by Levavasseur.

Antoinette VII with 50hp V-8 Musee du Bourge

An Antoinette VII aircraft with a 50 hp (37 kW) V-8 engine on display in the Musée de l’Air et de l’Espace. Note how well the engine fits into the aircraft and that the condensers appear to be made entirely of copper. For cooling, steam flowed from the top of the water jackets into a separation tank. The steam then flowed from the tank into the condenser, where it returned to water. The water was then pumped from the condenser into the bottom of the separation tank and back to the engine. (Pline image)

Levavasseur’s Antoinette engines were essentially the first commercially available aircraft engine and represented the pinnacle of performance in the early days of aviation. Just about every early European aviation pioneer’s first flight was powered by an Antoinette, but the engines’ reliability left much to be desired. While some changes were incorporated over the years, and their reliability did improve, the basic engine did not change much. Just before 1910, other engines (the Gnome rotary in particular) offered similar power for a similar weight but were often more reliable than the Antoinettes.

Note: Many sources give similar but completely different values for Antoinette engine dimensions, bores, strokes, and outputs. Some discrepancies can be attributed to numerous unit conversions being applied, and some of the power discrepancies can be attributed to the engines having different outputs at different rpms. Sadly, it seems that detailed specifics were not recorded in those early days of aviation; therefore, there can be no absolute certainty about the various Antoinette engine models or their histories.

V-20 engine

The V-20 engine as displayed at Le Manoir de l’Automobile et des Vieux Métiers in Lohéac, France. Regardless of the V-20’s origins, it seems rather inglorious for such machinery to be turned into furniture. However, the engine would have probably been scrapped long ago had it not found favor as a conversation piece. Apparently, its conversion to a table consisted of nothing more than bolting on legs to preexisting mounts, something that could easily be reversed for a more befitting display. (ZANTAFIO56 image)

Sources:
Bléroit: Herald of an Age by Brain A. Elliot (2000)
Les moteurs et aéroplanes Antoinette by Gérard Hartmann (13 August 2007) 7.4 MB pdf in French
The Art of Aviation by Robert W. A. Brewer (1910)
The Passion That Left the Ground by Stephen H. King (2007)
Vingt Cinq Ans d’Aéronautique française: 1907-1932 Tome 1 (1934)
– “The First Paris Aeronautical Salon: Engines for Aeroplanes” Flight (16 January 1909)
– “How Levavasseur Built his Light Motor” by Ferdinand Ferber The Automobile (28 March 1907)
– “Historie du moteur Antoinette” by Ferdinand Ferber l’Aérophile (15 February 1908)
– “Moteur à huit cylindres” French patent 339,068 by Léon Levavasseur (applied 28 August 1903)
– “Carbureter” US patent 878,297 by Léon Levavasseur (applied 16 may 1907)
– “Umsteuerungsvorrichtung für Mehrzylinder-Explosionskraftmaschinen” Austrian patent 25,610 by Léon Levavasseur (applied 14 September 1904)
Airplane Engine Encyclopedia by Glenn Angle (1921)
http://www.theaerodrome.com/forum/showthread.php?t=57838

Republic XP-69 side

Republic XP-69 Fighter

By William Pearce

In February 1940, the United States Army Air Corps (AAC) issued Request for Data R40-C to various engine and aircraft manufacturers. R40-C encouraged aircraft manufacturers to propose unorthodox aircraft capable of at least 450 mph (724 km/h), but preferably 525 mph (845 km/h), and to meet other requirements outlined in Type Specification XC-622. R40-C also asked aircraft engine manufacturers to develop new power plants. Initially, a total of 26 aircraft designs were submitted by six selected aircraft companies and included a mix of eight different engines from four engine companies. Republic Aviation’s entry carried the company designation AP-12.

Republic AP-12 Rocket

The AP-12 Rocket was Republic’s entry into the R40-C fighter competition. Note the mid-fuselage-mounted Wright R-2160 Tornado engine.

Like almost all of the other R40-C entries, the Republic AP-12 ‘Rocket’ was not a conventional aircraft. The AP-12 had a streamlined, cigar-shaped fuselage and utilized a tricycle undercarriage. The aircraft’s Wright R-2160 Tornado engine was placed behind the pilot. The engine’s extension shaft ran under the cockpit and drove a six-blade, contra-rotating airscrew at the front of the aircraft. Four machine guns were installed in the AP-12’s nose and fired through the propellers, and an additional machine gun was installed in each wing, outside of the propeller arc. A 20 mm cannon was installed in the nose of the aircraft and fired through the propeller hub.

After the AP-12 placed 13th out of the R40-C entries, Republic literally went back to the drawing board and created a new design, designated AP-18. The AP-18 possessed some of the same lines and used the same engine as the AP-12; however, the R-2160 engine was now installed in the nose of the aircraft. Republic submitted its AP-18 design to the AAC in July 1941 and was awarded a contract in December 1941 to produce two prototypes of the aircraft, designated XP-69 (it also carried the “Materiel, Experimental” project designation MX-162).

Republic XP-69 15-Sept-1941 inboard drawing

This XP-69 drawing dated 15 September 1941 clearly shows the Wright Tornado installed in the nose of the aircraft, with the turbosupercharger and its ancillary equipment mounted behind the cockpit. While the leading edge is distorted, the trailing edge shows the inner wing section perpendicular to the fuselage, then tapering toward the wing tip. This drawing was discovered in the National Archives by Kimble McCutcheon of the Aircraft Engine Historical Society.

The Republic XP-69 was an all-metal, high-altitude interceptor fighter with a conventional layout. The aircraft was powered by a 42-cylinder R-2160 engine that produced 2,500 hp (1,864 kW) at 4,600 rpm and was installed in a normal manner, without an extension shaft. The engine drove a 13 ft 8 in (4.17 m) diameter, six-blade, contra-rotating propeller built by Hamilton Standard. The turbosupercharger, intercoolers, radiator, and oil coolers were all positioned behind the cockpit. The scoop mounted under the cockpit brought in air for the radiator, oil coolers, intercoolers, and turbosupercharger via a complex series of ducts. The scoop also incorporated a boundary layer air bleed duct. Initially, four air exit doors were located under the fuselage, but the exits were later relocated, with two on each side of the XP-69 (the oil cooler was the lower exit and the intercooler the upper). However, radiator and boundary layer air as well as exhaust from the turbosupercharger exited from the bottom of the aircraft.

Most sources contend that the R-2160 engine was installed behind the XP-69’s cockpit. However, all of the equipment and associated ducting that was installed behind the cockpit left no room for anything else. In addition, a drawing dated 15 September 1941 found in the U.S. National Archives by Kimble McCutcheon clearly shows the Wright Tornado installed in the nose of the aircraft.

Republic XP-69 side

The Republic XP-69 model undergoing wind tunnel tests. Note the revised belly scoop and the air exits on the rear fuselage. The man pictured at the bottom of the photo gives some scale to the large size of the model, which was 3/4-scale. (image via Langley Memorial Aeronautical Laboratory / NASA)

The XP-69 utilized a pressurized cockpit in a fairly narrow fuselage, and its standard taildragger landing gear was fully retractable. The aircraft’s armament consisted of two .50 cal machine guns and one 37 mm cannon installed in each wing, outboard of the main landing gear. The machine guns had 320 rpg, and the cannons had 40 rpg. Some sources state an alternative armament installation consisted of six .50 cal machine guns in the wings and no cannons. Initially, the leading and trailing edges of the inboard wing sections were exactly perpendicular to the fuselage. This was later revised so that the wing’s taper was unchanged throughout its leading and trailing edges. Slotted flaps extended across about 50 percent of the wing’s trailing edge to help lower the heavy aircraft’s landing speed.

The XP-69 was a large aircraft with a wingspan of 52 ft (15.85 m), a length of 51 ft 8 in (15.75 m), and a height of 17 ft 3 in (5.26 m). The aircraft had a top speed of 450 mph (724 km/h) at 35,000 ft (10,668 m), an initial climb rate of 2,750 fpm (13.97 m/s), and a ceiling of 48,900 ft (14,905 m). Eight wing fuel tanks provided a total capacity of 386 gal (1,461 L), and a 114 gal (432 L) fuselage tank brought the aircraft’s total fuel capacity to 500 gal (1,893 L), which provided a maximum range of 1,800 miles (2,897 km). Wind tunnel tests were conducted with a 75 gal (284 L) drop tank under each wing of the aircraft. The XP-69 had an empty weight of 15,595 lb (7,074 kg), a gross weight of 18,655 lb (8,462 kg), and a maximum weight of 26,164 lb (11,868 kg).

Republic XP-69 top

Top view of the XP-69 model illustrates the aircraft’s relatively narrow fuselage and that its wings had a continuous taper. Note the 75 gallon drop tank mockups on the left of the image and the Douglas XB-19 model on the right. (image via Langley Memorial Aeronautical Laboratory / NASA)

A 1/20-scale XP-69 model was used for spin recovery tests, the results of which were generally satisfactory—although, recovery was problematic at 30,000 ft (9,144 m). A 3/4-scale model of the XP-69 was completed around June 1942 and began wind tunnel tests in August. The extensive tests were to analyze and evaluate the aircraft’s stability, controls, and cooling system and included fitting the model with 10 ft (3.0 m) diameter, contra-rotating propellers driven by two 25 hp (19 kW) electric motors in the fuselage. The tests indicated some longitudinal instability; the forecasted rate of roll was inadequate, and the estimated control forces for full aileron deflection were excessive. The XP-69 would utilize a control yoke, which would provide a certain degree of mechanical advantage over a control stick. Tests also revealed that the cooling system was not as efficient as expected and required some revision.

Construction of the first prototype began in November 1942 and incorporated changes shown necessary from the various wind tunnel experiments. While development of the XP-69 continued, the R-2160 engine was delayed with design issues that, in turn, would delay the aircraft. Also, a miscommunication had occurred: Republic thought the first engines would be capable of 2,500 hp (1,864 kW) at 4,600 rpm. In reality, the R-2160 would produce only 2,350 hp (1,752 kW) at 4,150 rpm; 2,500 hp (1,864 kW) was the engine’s developmental goal. The reduced power would inhibit the XP-69’s performance, and its 450 (724 km/h) mph top speed was already seen as optimistic.

Republic XP-69 flaps

The XP-69 model with its flaps fully deployed at 40 degrees. The slotted flaps extended aft and down. Note the air exits on the side of the fuselage. (image via Langley Memorial Aeronautical Laboratory / NASA)

Republic wanted to end work on the XP-69 and focus their resources on an alternative project. The company believed their AP-19 design (in a way, a Pratt & Whitney R-4360-powered P-47) held more potential and could fly sooner than the XP-69. The AP-19 (designated XP-72) was designed for and proposed to the AAC at the same time as the AP-18/XP-69. Since the AAC wanted an R-2160-powered fighter as soon as possible, Republic’s AP-18/XP-69 design was contracted, as it was the most appealing candidate. But now, with the engine issues affecting the XP-69, the XP-72 could no longer be overlooked as the superior aircraft. The XP-69 was cancelled on 11 May 1943, and two prototypes of Republic’s XP-72 were ordered on 18 June 1943. The Wright R-2160 Tornado was cancelled on 12 February 1944.

Note: Most sources list the XP-69’s wingspan as 51 ft 8 in (15.75 m) and its length as 51 ft 6 in (15.70 m). The dimensions given in this article, a 52 ft (15.85 m) wingspan and a 51 ft 8 in (15.75 m) length, come from two NACA reports from the 1940s.

Republic XP-69 nose

This image of the XP-69’s nose displays the propellers that were powered by two 25 hp motors for the wind tunnel tests. Also note the complex segmentation of the belly scoop inlet. (image via Langley Memorial Aeronautical Laboratory / NASA)

Sources:
Tornado: Wright Aero’s Last Liquid-Cooled Piston Engine by Kimble D. McCutcheon (2001)
U.S. Experimental & Prototype Aircraft Projects: Fighters by Bill Norton (2008)
American Secret Projects 1937–1945 by Tony Buttler and Alan Griffith (2015)
American Secret Pusher Fighters of World War II by Gerald H. Balzer (2008)
Stability and Control Tests of a 3/4-Scale Model of the XP-69 Airplane in the NACA Full-Scale Tunnel by Harold H. Sweberg (7 January 1943)
Compilation of Test Data on 111 Free-Spinning Airplane Models Tested in the Langley 15-Foot and 20-Foot Free-Spinning Tunnels by Malvestuto, Gale, and Wood (1947)
http://www.weakforcepress.com/tornado_errata.shtml
http://www.weakforcepress.com/XP-69/index.html
http://crgis.ndc.nasa.gov/historic/Test_139:_XP-69_3/4%E2%80%93scale_Model_%28Stability_and_Cooling%29

CAC CA-14A front

Commonwealth Aircraft Corporation CA-14/A Fighter

By William Pearce

In late 1941, the Australian aviation industry took stock of its resources and worked to create an indigenous fighter aircraft to defend against the Japanese. The result of this effort was the Commonwealth Aircraft Corporation (CAC) CA-12, CA-13, and CA-19 Boomerang fighters. In many respects, the Boomerang was an outgrowth of the CAC Wirraway general use aircraft. The Wirraway itself was a modified, licensed production version of the North American NA-16 (also referred to as NA-33) trainer. With a low top speed and poor altitude performance, the very maneuverable and rugged Boomerang found itself excelling in the ground attack role. In late 1942, The Australian War Cabinet and CAC sought to improve the Boomerang’s altitude performance by adding a turbosupercharger. This new aircraft was designated CA-14.

CAC CA-14 front

At first glance, the CAC CA-14 looks like a standard Boomerang fighter, but the aircraft’s unique turbosupercharger scoop can be seen on the side of the fuselage. Less noticeable modifications from a standard Boomerang include a new wing root fairing and a slightly enlarged tail.

The CA-14 was a standard CA-13 Boomerang that had been heavily modified to accommodate a turbosupercharger. Like all CA-13 Boomerangs, the CA-14 had a 1,200 hp (895 kW) Pratt & Whitney (P&W) R-1830 engine. The fuselage was built with a steel tube frame, and the wings and tail were built up from aluminum components. The wings housed four .303 machine guns and two 20 mm cannons. The tail, cowling, lower part of the fuselage, and in front of the cockpit were skinned with aluminum. All tail control surfaces were fabric-covered, and the ailerons were aluminum-skinned.

Unlike a normal Boomerang, the CA-14 had a new cowling that omitted the air intake scoop positioned above the engine on a standard Boomerang. A large scoop was added on the left side of the fuselage, next to the cockpit, and provided intake air for the engine and air for the turbosupercharger’s intercooler. Air exited the intercooler via an adjustable flap located on the right side of the upper fuselage, just behind the cockpit. The engine’s exhaust pipe was extended back along the right side of the fuselage to the turbosupercharger installed behind the cockpit. The General Electric (GE) B-2 turbosupercharger was from a Consolidated B-24 Liberator, and the Harrison intercooler was from a Boeing B-17 Flying Fortress; these parts were chosen because they were available, not because they were ideal. The fuselage was skinned with aluminum to just behind the turbosupercharger. Farther aft, the fuselage was wood-covered. A new, more streamlined fairing was installed on the wing’s leading edge. The fairing ran from the wing root to the fuselage, over the main gear wheel bays. The CA-14’s vertical stabilizer was slightly enlarged, and it used an 11 ft (3.35 m), three-blade, Curtiss propeller.

CAC CA-14 left side

The CA-14’s large scoop can be seen in this view. The scoop created turbulence that interfered with the aircraft’s tail. Pilot visibility was improved over the standard Boomerang by removing the engine intake scoop on the upper cowling.

The CA-14 was assigned serial number A46-1001 and first flew on 13 January 1943 piloted by Flt. Lt. John Holden. Its performance was on par with a standard Boomerang below 10,000 ft (3,048 m) but was superior above that altitude. At 28,000 ft (8,534 m), the CA-14 had a top speed of 354 mph (570 km/h) and a 1,400 fpm (7.1 m/s) rate of climb, while the standard Boomerang was 76 mph (122 km/h) slower at 278 mph (447 km/h) and could only climb at 450 fpm (2.3 m/s). The CA-14 had a 2,150 fpm (10.9 m/s) initial rate of climb and a ceiling of 36,000 ft (10,973 m), which was 2,000 ft (610 m) higher than a standard Boomerang’s ceiling. The CA-14 had the same 36 ft (10.97 m) wingspan and 25.5 ft (7.77 m) length as the Boomerang; however, it was some 400 lb (180 kg) heavier, at 8,095 lb (3,672 kg). The aircraft had a range of 930 miles (1,497 km).

Flight testing revealed directional instability and cooling issues with engine and turbosupercharger. The large scoop mounted on the side of the fuselage created turbulent air which interfered with the aircraft’s tail and caused some instability and buffeting. Starting in May 1943, the CA-14 was reworked to solve its issues and was redesignated CA-14A. Changes included adding a new, larger vertical stabilizer with an aluminum-skinned rudder and deleting the scoop from the aircraft’s fuselage. The engine cowling was reworked to provide better cooling, and a geared (3 to 1), 10-blade cooling fan was added behind the spinner. Air for the engine and intercooler was taken from the high-pressure area behind the cooling fan and internally ducted in the left side of the fuselage back to the turbosupercharger. A GE B-13 turbosupercharger and an AiResearch intercooler replaced the original units. The CA-14A was fitted with a three-blade Hamilton Standard or de Havilland propeller (sources disagree on which, but perhaps both propellers were tested), and its guns were removed. First flown around 26 July 1943, the CA-14A most likely achieved better performance than the CA-14; however, specifics have not been found. Sources indicate the CA-14A’s ceiling was in excess of 40,000 ft (12,192 m).

CAC CA-14 and CA-14A

A comparison of the CA-14 (top) and CA-14A (bottom), with its revised tail and cowling. The exit flap for the intercooler can bee seen in the upper fuselage, just behind the cockpit. The installation of the supercharger and its required accessories in the Boomerang’s small airframe was an impressive feat of engineering.

The ultimate goal of improving the Boomerang was to install a 1,450 hp (1,081 kW) P&W R-2000 engine and GE B-9 turbosupercharger in the aircraft. Originally, these changes were to be incorporated when the aircraft was rebuilt as the CA-14A. However, the United States was very reluctant to provide a license for supercharger production, and CAC’s production of licensed R-2000 engines encountered technical setbacks. The estimated speed of an R-2000-powered Boomerang was 286 mph (460 km/h) at sea level and 372 mph (599 km/h) at 27,000 ft (8,230 m). The aircraft’s rate of climb at sea level was 2,100 fpm (10.7 m/s) and 1,770 fpm (9.0 m/s) at 30,000 ft (9,144 m).

Based on the known performance of the CA-14 and the estimated performance of the R-2000-powered Boomerang, the Minister for Aircraft Production recommended that 120 R-2000-powered fighters be ordered. However, the Australian War Cabinet approved only 50 aircraft. With such a short production run, it was not worth the inevitable delays and required resources to upgrade Boomerang production to a new standard, especially with better performing fighters from the United States and Britain already arriving in Australia. As a result, the 50 aircraft were completed as CA-19 Boomerangs, which differed little from the CA-13s and CA-12s.

CAC CA-14A front

This view of the CA-14A displays its 10-blade engine cooling fan as well as its lack of armament. Undoubtedly, the aircraft’s performance was much improved, but its usefulness was in question since superior British and American aircraft were available in Australia. Note the Republic P-47 Thunderbolts in the background.

While the A46-1001 airframe was being designed and tested with its turbosupercharger, CAC looked to take the next step to enhance performance by fitting a 1,700 hp (1,268 kW) Wright R-2600 engine to an even more modified Boomerang. However, the availability of R-2600 engines to Australia was in question, and modifications to the Boomerang airframe would be substantial. It was deemed more practical to start development of a new aircraft with a 2,000 hp (1,491 kW) P&W R-2800 engine. Designated CA-15, this new aircraft would eventually fly, but with a Rolls-Royce Griffon V-12 engine and little resemblance to its initial design heritage.

The obsolete CA-14A continued to undergo flight testing and was used for high altitude weather observations, regularly flying at 40,000 ft (12,192 m). It was removed from service in 1946 and scrapped in 1947 (some sources say March 1949).

Note: The B-13 turbosupercharger was interchangeable with the B-2. Several sources state that CAC intended to install a B-9 turbosupercharger in the CA-14/A aircraft, but no GE references to a B-9 turbosupercharger have been found. Perhaps “B-9” was a typo or was a designation given to a licensed production or export model (like “B-10” for turbosuperchargers supplied to Britain).

CAC CA-14A left side

For the CA-14A, the large fuselage scoop was removed, and air to the turbosupercharger was delivered via an internal duct. The location of that duct can be discerned by the bulge running along the side of the fuselage

Sources:
Wirraway, Boomerang & CA-15 in Australian Service by Stewart Wilson (1991)
Wirraway to Hornet by Brian L Hill (1998)
Australia’s Lost Fighter: The CA-15 and its Demise by David Clark (2010)
http://www.australianflying.com.au/news/warbirds-the-turbo-interceptor-boomerang

Ford 15P front

Ford 15P Personal Aircraft

By William Pearce

Henry Ford was an absolute titan of industry. His ability to mass-produce the automobile made them affordable to the average citizen in the United States. Owning cars revolutionized the way people lived. On more than one occasion, Ford attempted to do the same thing with the airplane—create a simple, affordable, and easy-to-fly aircraft for the masses. The design of an inexpensive and mass-produced aircraft was referred to as a “flivver” plane. The Ford Motor Company’s last flivver aircraft was the 15P, and like previous attempts, it did not succeed.

Ford 15p mockup

Full-scale mockup of the Ford 15P from January 1935. With the exception of an unfaired tailwheel, the complete aircraft was very similar to the mockup.

Edsel Ford, Henry’s son, had an interested in aviation, and he helped finance William B. Stout’s founding of the Stout Metal Airplane Company in 1922. By 1924, Henry had joined Edsel to help the Stout Metal Airplane Company, and the Ford Motor Company (FMC) built an airport and factory for Stout in Dearborn, Michigan. In 1925, the FMC purchased Stout’s company, which became the Stout Metal Airplane Division of the Ford Motor Company. The Stout Division went on to create the famous Ford Tri-Motor transports.

The Great Depression had a large impact on the FMC and Stout Division. By 1932, Henry Ford had refocused his efforts on automobiles; aircraft production and development at FMC had virtually stopped. In November 1933, the Aeronautics Branch of the Department of Commerce challenged the aviation industry to develop an $800 aircraft that just about anyone could afford, fly, and maintain. This concept—a Model T of the air—mirrored that of Ford’s flivver plane attempts.

In early 1934, FMC had experimented with a flathead V-8 modified for aircraft use. Coinciding with this engine’s development was the design of the 15P aircraft by Harry Karcher and Gar Evans. A model of the 15P was built in September 1934, and a full-scale mockup was completed in January 1935. It is not clear if the main proponent of the 15P was Henry, who had a long-standing quest to make aircraft ownership possible for the average citizen, or Edsel, who had always been interested in aviation. In all likelihood, they probably both had an equal role. Regardless, construction of the 15P followed the mockup, and the aircraft was completed by early 1936.

Ford 15P rear aerofiles

Rear view of the Ford 15P displays the five air scoops that led into the engine compartment and the three rows of louvers that allowed the cooling air to exit. (image via Aerofiles.com)

The Ford 15P was a tailless, flying wing aircraft with the pilot and single passenger sitting side-by-side in a teardrop-shaped fuselage. The cockpit had dual controls and instrumentation in the center, making the aircraft easy to fly from either seat. Each seat in the cockpit was accessible by a hinged top hatch that opened up toward the center of the aircraft and a hinged side window that opened toward the front of the aircraft.

The fuselage was made of steel tubing and covered with aluminum sheeting. The wings had an aluminum structure, were fabric-covered, and each carried 15 gallons (57 L) of fuel. Along the wing’s trailing edge, flaps were positioned near the fuselage. Outboard of the flaps were drag rudders, and elevons (combination elevator and aileron) were at the wingtips. The 15P was supported on the ground by standard taildragger landing gear. The main gear was positioned under the wings and enclosed in large, streamlined fairings, which also housed a landing light. The castoring tailwheel was positioned at the extreme rear of the aircraft.

Directly aft of the firewall behind the pilot and passenger was the Ford flathead V-8 engine. Although engine specifics have not been found, the engine most likely had a 3.0625 in (77.8 mm) bore, a 3.75 in (95.3 mm) stroke, and displaced 221 cu in (3.62 L). The engine is noted as being virtually standard so that parts would be available from most Ford auto repair shops. Unique to the aircraft engine was its all-aluminum construction and that it produced 115 hp (86 kW) at 4,000 rpm. The engine drove an enclosed propeller shaft that ran between the pilot and passenger. Sources list the 15P as using a 6.5 ft (1.98 m) diameter, wooden Gardner propeller. However, photos appear to show a metal propeller.

Ford 15P engine

The flathead Ford V-8 in the 15P’s engine compartment. Note the fixed radiator or header tank at the rear of the compartment. Also note the hinged top and side panels for cockpit access. (image via The Aviation Legacy of Henry & Edsel Ford)

The engine cowling consisted of two panels that hinged up toward the center of the aircraft. Each panel had two air scoops, and another scoop was positioned between the panels on the aircraft’s spine. The radiator was positioned aft of the engine, and three rows of louvers were behind the radiator. Cooling air would enter the engine compartment via the five scoops and through an additional scoop positioned under the aircraft. Air would pass through the radiator and exit via the louvers at the rear of the aircraft. Some sources state the radiator was retractable and could extend below the aircraft; however, this would have added much complexity to what was supposed to be a simple aircraft. Instead, perhaps the ventral scoop could be extended to allow more airflow during ground running. The engine’s exhaust was expelled under the aircraft.

Very little information regarding the Ford 15P remains. The aircraft’s approximate specifications are a wingspan of 34 ft (10.4 m), a length of 14 ft (4.27 m), and a gross weight of 1,600 lb (726 kg). The 15P had an estimated top speed of 120 mph (193 km/h) and a maximum range of 500 miles (805 km).

The Department of Commerce assigned registration number X999E to the 15P on 29 November 1935. The date of the aircraft’s first flight has not been found. Reportedly, the 15P made several flights, all made by FMC’s head pilot, Harry Russell. Controlling the aircraft was problematic and an issue that was not solved before the plane was damaged in a landing accident. The damaged 15P was placed in storage and not repaired.

FMC ceased aircraft operations, closing the Stout Metal Airplane Division in 1936. Apparently, what remained of the 15P was stored until 1941 when Henry Ford requested that it be used as a basis for an autogyro-type aircraft. Ultimately, the autogyro aircraft never flew, and its design was deemed unworkable. Whatever was left of the 15P disappeared along with the autogyro.

Ford 15P front

This front view of the Ford 15P shows what appears to be a metal propeller. Note the air scoop and engine exhaust under the aircraft. (image via The Aviation Legacy of Henry & Edsel Ford)

Sources:
The Aviation Legacy of Henry & Edsel Ford by Timothy J. O’Callaghan (2000)
– “Ford Reviews Test of Flivver Plane,” The Cincinnati Enquirer (14 January 1936)
http://www.aerofiles.com/_ford.html
https://en.wikipedia.org/wiki/Stout_Metal_Airplane

FKFS Gruppen-Flugmotor A mockup copy

FKFS Gruppen-Flugmotor A, C, and D

By William Pearce

In 1930, German engineer Wunibald Kamm founded the FKFS (Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart or Research Institute of Automotive Engineering and Vehicle Engines Stuttgart). The FKFS was an organization that tried and tested new, inventive ideas in the field of automotive technology. However, it was not long before Kamm’s thoughts and some of the FKFS’s resources were directed toward aircraft engines.

FKFS Gruppen-Flugmotor A mockup copy

Crankcase mockup of the FKFS Gruppen-Flugmotor A with Hirth HM 512 cylinders. Visible on the side of the engine is a mockup of the axial supercharger. (Kevin Kemmerer image)

In mid-1938, Kamm was able to persuade Willy Krautter of Hirth Motoren to join the FKFS as head of the FKFS’s Special Engine Group. Krautter’s first project at FKFS was building FKFS’s first aircraft engine. The result was a flat, air-cooled, two-stroke, four-cylinder engine that displaced 31 cu in (.51 L) and produced 25 hp (18 kW). The engine was used in the Hirth Hi-20 MoSe motor glider. Next, Krautter designed an improved and updated version of the four-cylinder engine, but priorities had shifted with the outbreak of World War II. Inspired by an open request from the RLM (Reichsluftfahrtministerium or German Ministry of Aviation), the FKFS focused on designing much larger engines.

The RLM was interested in large, powerful engines for bombers being designed to reach targets in North America. Both Kamm and Krautter believed that air-cooled engines were overall superior for aircraft use, and they designed a 32-cylinder engine intended for the RLM. This radial engine had eight cylinder banks evenly spaced at 45 degree intervals around the crankcase. Each cylinder bank consisted of four inline, air-cooled cylinders and a single overhead camshaft. The cylinder proposed for the engine was designed by Krautter and was undergoing tests at the FKFS.

FKFS Gruppen-Flugmotor A crankcase copy

Two views of the Gruppen-Flugmotor A’s crankcase. In the left image, note the rear accessory drive housing with provisions to power the axial supercharger. Also note the large roller bearing in the nose case. In the right image, note the crankshaft and camshaft position for each engine section. Crankcase finning is also visible in both images. (Kevin Kemmerer images)

Building a new aircraft engine from scratch is a massive undertaking, so Krautter suggested grouping together existing, proven engines to quickly create a larger, more powerful unit. Kamm supported Krautter’s idea of a Gruppen-Flugmotor (Group Aircraft Engine), and the detailed design of such a power unit commenced in 1939. The first engine was known as the Gruppen-Flugmotor A (or just Motor A), and it utilized almost all of the components from four Hirth HM 512 engines (excluding their crankcases) to create a new 48-cylinder engine. Undoubtedly, Krautter’s experience at Hirth Motoren influenced his decision to use HM 512 parts.

The Hirth HM 512 was an inverted, air-cooled, V-12 engine. Its individual cylinders were arranged in two rows spaced at 60 degrees and attached under an elektron (magnesium alloy) crankcase. Four long studs held each cylinder to the crankcase, and the cylinders were staggered to allow the use of side-by-side connecting rods. Each cylinder was made of cast iron and had an aluminum cylinder head. In the Vee of the engine, one intake and one exhaust valve per cylinder were actuated by individual pushrods driven by a single camshaft. Each cylinder had two spark plugs—one on each side of the cylinder. The intake and exhaust manifolds were mounted to the outer sides of the cylinder banks. The HM 512 had a 4.13 in (105 mm) bore, a 4.53 in (115 mm) stroke, and a displacement of 729 cu in (11.9 L). The engine produced 450 hp (336 kW) at 3,100 rpm.

FKFS Gruppen-Flugmotor A complete copy

The complete 48-cylinder Gruppen-Flugmotor A. Note the intake manifolds leading from the axial supercharger to the two adjacent V-12 engine sections. The four Bosch magnetos are visible at the rear of the engine. (Kevin Kemmerer image)

For the Gruppen-Flugmotor A, an HM 512 crankshaft occupied each corner of the engine’s large, square-shaped, aluminum crankcase, and a camshaft was located at the apex of each corner. The cylinder banks for each engine section were on adjacent sides of the Gruppen-Flugmotor A’s crankcase. The two-piece aluminum crankcase was split horizontally and incorporated cooling fins on its exterior.

At the front of the Gruppen-Flugmotor A’s crankcase was a central combining gear that took power from each of the four crankshafts and transmitted it to a single propeller shaft. The crankshaft of each engine section could be decoupled from the combining gear if the engine section were damaged or to conserve fuel and increase an aircraft’s range. It was believed that the Gruppen-Flugmotor A’s economy could be increased up to 56% by decoupling two of the engine sections while cruising during a long-range flight.

FKFS Gruppen-Flugmotor A axial supercharger housing copy

The housing for an axial supercharger used on the Gruppen-Flugmotor A. Visible are the four stator rows. Each blade was inserted into a dovetail groove and held in place by a screw, visible on the outside of the housing. (Kevin Kemmerer image)

Another unusual feature of the Gruppen-Flugmotor A was its use of two axial superchargers that provided 11.6 psi (0.8 bar) of boost. The left and right sides of the engine each had one supercharger located between the cylinder banks. The axial superchargers had four stages (although photos appear to show three compressor stages and four stator rows) and were driven from the accessory section at the rear of the engine. Fuel was injected ahead of the superchargers and subsequently mixed with air. The air/fuel mixture was then fed to the cylinders via long induction manifolds. The engine’s four Bosch dual magnetos and other accessories were mounted to the rear of the engine.

The Gruppen-Flugmotor A had 48 cylinders with a 4.13 in (105 mm) bore and a 4.53 in (115 mm) stroke. The engine’s total displacement was 2,917 cu in (47.8 L). Unfortunately, most of the engine’s specifications have been lost, but it was around 6.07 ft (1.85 m) long and 4.27 ft (1.30 m) in diameter. The engine produced 1,970 hp (1,470 kW) at 3,200 rpm with manifold fuel injection. A switch to direct fuel injection was made by changing to Hirth HM 512 D cylinders that had an unused port in the cylinder head. With direct fuel injection, the Gruppen-Flugmotor A’s output was increased by 200 hp (150 kW) to 2,170 hp (1,620 kW). The engine was tested during 1941 and 1942, but test information has not been found. Photos indicate some trouble was encountered with the axial superchargers failing in dramatic ways. After the war, Krautter stated that the engine was capable of 2,400 hp (1,790 kW).

FKFS Gruppen-Flugmotor C

This drawing of the Gruppen-Flugmotor C illustrates how the engine design was a link between the Gruppen-Flugmotor A and D engines. Note the cooling fan and side-by-side connecting rods. (“Wunibald I. E. Kamm – Wegbereiter der modernen Kraftfahrtechnik” image)

As the Gruppen-Flugmotor A was proving the concept of a grouped-engine power unit, Kamm, Krautter, and the FKFS had already designed a larger, more powerful engine in 1941. Called the Gruppen-Flugmotor C (or Motor C), the 48-cylinder engine had the same basic layout as the earlier engine but used new components. An engine-driven cooling fan was employed to help minimize cooling drag, as both Kamm and Krautter felt the Gruppen-Flugmotor A’s cooling drag was excessive. The engine also had contra-rotating propeller shafts and two five-stage axial superchargers that provided 11.6 psi (0.8 bar) of boost.

FKFS Gruppen-Flugmotor D Cylinder copy

The 122 cu in (2.0 L) cylinder used on the Gruppen-Flugmotor D. The triangular cover conceals the camshaft drive for the valves. The baffle around the cylinder helped direct air to maximize cooling efficiency. (Kevin Kemmerer image)

The individual cylinders of the Gruppen-Flugmotor C were of Krautter’s maturing design, each having a capacity of 67 cu in (1.1 L). The cylinder had a hemispherical combustion chamber with two spark plugs and a port for direct fuel injection. The cylinder barrel and head were cast from aluminum as one piece, and the cylinder bore was chrome plated. A flange at the base of the cylinder attached it to the crankcase. Atop the cylinder was a housing for the intake and exhaust valves. The two valves were actuated via roller rockers by a single overhead camshaft, which served all the cylinders of one bank. Each camshaft was driven by a vertical shaft at the front of the engine.

The Gruppen-Flugmotor C had a 4.33 in (110 mm) bore, a 4.53 in (115 mm) stroke, and a total displacement of 3,201 cu in (52.5 L). The engine was 7.17 ft (2.185 m) long and 4.43 ft (1.35 m) in diameter. The Gruppen-Flugmotor C was forecasted to produce 3,500 hp (2,610 kW) at 4,000 rpm with the original 67 cu in (1.1 L) cylinders, but studies of larger 92 cu in (1.5 L) and 122 cu in (2.0 L) cylinders indicated outputs of 4,290 hp (3,200 kW) and 5,920 hp (4,415 kW), respectively. While some components of the Gruppen-Flugmotor C were built for testing, a complete engine was never built.

Seeing the potential of the Gruppen-Flugmotor C with 122 cu in (2.0 L) cylinders inspired Kamm and Krautter to create the Gruppen-Flugmotor D. Designed in 1943, the engine was very similar to the Gruppen-Flugmotor C, with 48 cylinders, a cooling fan, and contra-rotating propellers, but it used fork-and-blade connecting rods. The 122 cu in (2.0 L) cylinder was basically an enlargement of the 67 cu in (1.1 L) cylinder design. The Gruppen-Flugmotor D had four (one on each side of the engine) five-stage axial superchargers that provided 13.8 psi (0.95 bar) of boost.

FKFS Gruppen-Flugmotor D copy

Drawing of the 48-cylinder Gruppen-Flugmotor D. Note the cooling fan, contra-rotating propeller drive, and fork-and-blade connecting rods. One five-stage axial supercharger can be seen on the right side of the drawing. The engine was estimated to produce 5,920 hp (6,000 ps / 4,415 kW). (Kevin Kemmerer image)

The Gruppen-Flugmotor D had a 5.31 in (135 mm) bore and a 5.51 in (140 mm) stroke. The engine’s total displacement was 5,870 cu in (96.2 L), and it was forecasted to produce 5,920 hp (4,415 kW) at 4,000 rpm. Reportedly, a complete engine was ready for tests in April 1944, but the state of the war and the progress of jet engines rendered the Gruppen-Flugmotor D and its further development irrelevant. At the time, Germany was in need of interceptor fighters, not long-range bombers.

At war’s end, Kamm and Krautter were brought to the United States under Operation Paperclip, a program to extradite the best German scientists, engineers, and technicians and apply their skills and knowledge to further industries in the United States. The two men worked at Wright Field in Dayton, Ohio until they were released from their service. In the 1950s, Krautter founded his own engineering firm, the Wilkra Company, where he designed everything from engines for boats and motorcycles to lawn tractors and ski bikes.

Kamm 60-cylinder compound-diesel

The Kamm-designed 60-cylinder compound-diesel engine incorporating five V-12 engine sections around a central turbine. The engine’s concept was roughly similar to that of the Napier Nomad. (“Wunibald I. E. Kamm – Wegbereiter der modernen Kraftfahrtechnik” image)

For a time, Kamm worked with Krautter at Wilkra but returned to Germany in 1955. Kamm revisited the Gruppen-Flugmotor concept when he designed a 60-cylinder compound diesel-turbine engine. This engine consisted of five V-12 engine sections mounted around a central turbine. The V-12 engine sections were based on an extremely-high-output diesel engine Kamm had helped design while at the Stevens Institute of Technology in Hoboken, New Jersey in the early 1950s. The V-12s were air-cooled, two-stroke, loop-scavenged engines with side-by-side connecting rods. The turbine had a nine-stage axial compressor section, a combustion section, and a five-stage exhaust turbine section. High-pressure air from the compressor section would provide the incoming charge for the diesel engine. The diesel’s exhaust would be expelled into the exhaust section of the turbine. The turbine’s combustion section could run independently of the piston engine sections to increase the compound engine’s overall output. The engine’s bore and stroke were around 2.75 in (70 mm) and 4.5 in (114 mm), respectively, giving a total displacement of approximately 1,604 cu in (26.3 L). The 60-cylinder compound engine was designed to produce 2,950 hp (2,200 kW) without additional power from the turbine’s combustion section and 4,025 hp (3,000 kW) with the additional power. The engine would have had a low specific fuel consumption of .296 lb/hp/h (180 g/kW/h) and was forecasted to be 6.56 ft (2.00 m) long and 4.10 ft (1.25 m) in diameter. The 60-cylinder engine was never built.

Note: Kamm and Krautter’s Gruppen-Flugmotoren were not the first time that multiple engine sections were combined to create a large, powerful engine. In the 1920s, the French firm Bréguet created the Bréguet-Bugatti 32-cylinder Quadimoteurs in a similar but less complex fashion.

FKFS Gruppenmotor 48-Zyl copy

This drawing dated October 1943 depicts a 48-cylinder engine and lists its displacement as 37.6 L (2,294 cu in). The engine’s bore and stroke appear to be the same but are not listed on the drawing. A 100 mm (3.94 in) bore and stroke would give a displacement of 37.70 L (2,300 cu in). It is not clear how this engine fits into the overall history of the Gruppen-Flugmotoren, but its design is similar to the C and D engines. (Kevin Kemmerer image)

Sources:
– Correspondence with Kevin Kemmerer, grandson of Willy Krautter
Wunibald I. E. Kamm – Wegbereiter der modernen Kraftfahrtechnik by Jurgen Potthoff and Ingobert C. Schmid (2012)
– “Why Multicylinder Motorcycle Engines?” by W. Krautter, Design of Racing and High Performance Engines edited by Joseph Harralson (1995)
Aircraft Engines of the World 1944 by Paul H. Wilkinson (1944)
Engine-Transmission Power Plants for Tactical Vehicles by Emil M. Szten et. al. (1967)

Sud-Est SE 580 cowling

Sud-Est (SNCASE) SE 580 Fighter

By William Pearce

The state-owned French aircraft manufacturer SNCAM (Société nationale des constructions aéronautiques du Midi or National Society of Aircraft Constructors South) was formed in March 1937 when the Dewoitine firm was nationalized. Many Dewoitine personnel, including the company’s founder, Émile Dewoitine, continued to work for SNCAM. As a result, aircraft designed and built at SNCAM continued to bear the Dewoitine name.

Sud-Est SE 580 model

Wind tunnel model of the Sud-Est SE 580 complete with contra-rotating propellers.

In 1940, SNCAM began studies of a new fighter aircraft. The aircraft was based on a continuing design evolution that started with the Dewoitine D.520 production fighter and progressed through the D.551/552 pre-production fighters. SNCAM’s new fighter design was designated M 580.

The M 580 aircraft was a tractor design with conventional undercarriage. However, the power plant was unusual in that it utilized two Hispano-Suiza 12Z engines coupled in tandem and driving a coaxial contra-rotating propeller (similar to the Arsenal VB 10). The M 580 was designed by Robert Castello and Jacques Henrat, who had been very involved with previous Dewoitine fighter designs. Before much design work was completed, SNCAM was absorbed into SNCASE (Société nationale des constructions aéronautiques du Sud-Est or National Society of Aircraft Constructors Southeast) in late 1940.

With the SNCASE (often referred to as Sud-Est) takeover and the German occupation of France, the M 580 design languished during the war. Under Sud-Est, the aircraft was redesignated SE 580. Wind-tunnel tests were conducted in 1943, and the SE 580 design was changed to incorporate a new engine then under development. Gone was the tandem V-12 engine configuration, and in its place was a single 24-cylinder Hispano-Suiza 24Z engine. With much of France liberated in 1944, two SE 580 prototypes were ordered by the Ministère de l’Air (French Air Ministry). The Marine Nationale (French Navy) was interested in a navalized version designated SE 582 and ordered two prototypes in early 1945.

Sud-Est SE 580 HS 24Z

The SE 580 with open cowling revealing the 24-cylinder, 3,600 hp (2,685 kW) Hispano-Suiza 24Z engine.

Work on the SE 580 prototype was started first. The aircraft was of all-metal construction with fabric-covered control surfaces. The aircraft’s structure, especially the wings, followed basic Dewoitine design principals used in their earlier fighter aircraft. The SE 580 featured dive recovery flaps positioned under the wing and outside of the fully retractable main landing gear. Another unusual feature was that the incidence of the aircraft’s horizontal stabilizer was adjustable.

The smooth flow of the aircraft’s fuselage was interrupted by a large hump behind the cockpit. This structure housed the scoop that directed air through a radiator positioned horizontally in the aircraft’s rear fuselage. Cooling air entered a large opening just behind the cockpit, traveled down through the radiator, and exited the fuselage via a ventral flap. The intake also incorporated a slot for boundary layer air bleed. The radiator’s location in the center of the aircraft offered some inherent protection that was further enhanced by rear armor plating to protect against enemy fire.

Three fuselage fuel tanks and one fuel tank in each wing held a total of 660 gallons (2,500 L). A drop tank under the fuselage held an additional 79 gallons (300 L) of fuel. The SE 580’s Hispano-Suiza 24Z engine was an H-24 that was forecasted to produce 3,600 hp (2,685 kW). The 24Z would turn an 11.5 ft (3.50 m) diameter, six-blade, contra-rotating propeller.

Sud-Est SE 580 front

The supercharger intakes and numerous exhaust stacks interrupt the otherwise clean lines of the SE 580’s fuselage. The dorsal radiator scoop created a large blind spot for the pilot. One must wonder how cleanly air would flow into the scoop after being disrupted by the canopy.

The SE 580’s armament was quite substantial and consisted of a 30 mm cannon mounted between the engine’s upper cylinder banks and firing through the propeller hub. Each wing housed two 20 mm cannons and four 7.5 mm (or three 12.7 mm) machine guns. A hardpoint under each wing could accommodate a 1,102 lb (500 kg) bomb. A photo reconnaissance version would accommodate a vertical camera in the central fuselage.

The SE 580 had a 52.0 ft (15.86 m) wingspan and was 42.7 ft (13.0 m) long. The aircraft had an empty weight of 11,228 lb (5,093 kg) and a gross weight of 17,919 lb (8,128 kg). The SE 580 had a top speed of 373 mph (600 km/h) at sea level and 465 mph (749 km/h) at 30,512 ft (9,300 m). Its landing speed was 88 mph (141 km/h). The SE 580 could climb to 19,685 ft (6,000 m) in just over six minutes and had a theoretical ceiling of 44,619 ft (13,600 m). The aircraft’s maximum range was 1,709 miles (2,750 km).

By 1946, construction of the first SE 580 prototype was well underway, and a Hispano-Suiza 24Z engine was installed in the airframe. Unfortunately, problems with the 24Z engine resulted in its cancellation. The Arsenal 24H was selected as the replacement engine. The 4,000 hp (2,983 kW) 24H was also a 24-cylinder engine in an “H” configuration but had many differences when compared to the 24Z. The 24H was heavier and had a different propeller location; it used a single rotation, 12.1 ft (3.70 m) diameter, five-blade propeller. These differences required numerous, complex changes to the SE 580. The longer propeller was located 5.12 in (130 mm) lower on the engine and required changes to the aircraft’s landing gear and wings to maintain acceptable ground clearance. Wind-tunnel tests indicated further wing changes would be needed and that the engine had to be moved forward. In light of all the required changes, budgetary cutbacks, Sud-Est’s preoccupation with other projects, and the emergence of jet aircraft, the SE 580 was cancelled in 1947.

Sud-Est 580 rear

This rear view of the SE 580 shows the large radiator housing behind the cockpit. Note the cooling air exit flap under the fuselage.

SE 582 development trailed behind that of the SE 580; the French Navy was more interested in the Sud-Ost SO.8000, and Sud-Est was more focused on the SE 580. Changes needed to navalize the aircraft included incorporating an arrestor hook and folding wings. Construction of the SE 582 was limited to components that were shared with the SE 580, but it does not appear that any substantial part of the SE 582 was ever completed. The SE 582 had the same basic specification as the SE 582, except it was 712 lb (323 kg) heavier, at a gross weight of 18,631 lb (8,451 kg).

When Sud-Est abandoned the SE 580/582, the possibility of SNCAC (Société nationale des constructions aéronautiques du Centre or National Society of Aircraft Constructors Center) taking over the projects was discussed. However, the status of aviation could not be changed—the SE 580 and 582 were outdated, and existing aircraft already matched their performance. The first SE 580 prototype was never completed.

Sud-Est SE 580 cowling

SE 580 was a large aircraft, and its predicted performance equaled, but not bettered, existing aircraft then in service. Lack of available information about the aircraft, combined with its unique configuration and engine have made the SE 580 a curiosity for many aviation enthusiasts.

Sources:
Les Avions de Combat Francais 1944-1960 I – Chasse-Assaut by Jean Cuny (1988)
Les Avions Dewoitine by Raymond Danel and Jean Cuny (1982)
http://www.secretprojects.co.uk/forum/index.php/topic,4110.0.html
http://www.aviationbanter.com/showthread.php?t=76826

Arsenal 24H rear

Arsenal 24H and 24H Tandem Aircraft Engines

By William Pearce

In occupied France during World War II, the state-run manufacturer Arsenal de l’Aéronautique (Arsenal) was tasked with building the German Junkers Jumo 213 engine. The Jumo 213 was a liquid-cooled, inverted V-12 engine that displaced 2,135 cu in (35.0 L) and produced 1,750 hp at 3,250 rpm. After the war, Arsenal continued to develop the Jumo 213 and manufactured a 2,300 hp variant as the Arsenal 12H.

Arsenal 24H front 2

The Arsenal 24H was a 4,000 hp (2,983 kW), 24-cylinder engine that utilized many components originally designed for the Junkers Jumo 213 V-12. Note the centerline location of the single rotation propeller shaft.

During the war, Junkers contemplated building the Jumo 212, which was an H-24 engine utilizing many Jumo 213 components. While the Jumo 212 was not built, it was designed along the same lines as the Hispano-Suiza 24Y and 24Z engines. It is not known if Arsenal was inspired by the Jumo 212 or the Hispano-Suiza H-24 engines, but they created their own H-24 engine based on parts from the Arsenal 12H (which was originally based on the Jumo 213). Arsenal’s 24-cylinder engine was known as the 24H.

The Arsenal 24H was a vertical H engine with two cylinder banks mounted above the crankcase and two cylinder banks below. The two-piece aluminum crankcase was split vertically at its center. Covers on each side of the crankcase allowed access to the engine’s internals. While the cylinder blocks of the 12H were cast integral with its crankcase, the 24H used aluminum cylinder blocks that were separate. The detachable aluminum cylinder head featured two intake valves and one exhaust valve per cylinder. The valves for each cylinder bank were actuated by a single overhead camshaft driven by a vertical shaft at the rear of the engine.

Arsenal 24H side

Unlike the Jumo 213, the cylinder blocks of the 24H were detachable and not cast integral with the crankcase. Note the magnetos mounted atop the gear reduction housing. The fuel injection pumps are just visible above the top valve cover and and below the bottom valve cover.

Inside the crankcase were two crankshafts with enough horizontal separation to allow a shaft to pass between them. This feature would allow engines to be coupled in tandem. Each crankshaft served an upper and lower cylinder bank pair. The crankshafts had six throws and were supported by seven main bearings. Pistons with a compression ratio of 6.5 to 1 were attached to the crankshafts by fork-and-blade connecting rods.

Two single-stage, two-speed superchargers were at the rear of the engine and driven by a cross-shaft from the engine’s accessory section. The superchargers had automatic boost and speed control with a low speed of 6.90 times crankshaft speed and a high speed of 9.41 times crankshaft speed. The left supercharger supplied air to the upper cylinder banks, and the right supercharger supplied air to the lower cylinder banks. The intake manifolds incorporated an aftercooler and were situated between their respective cylinder banks. A fuel injection pump was positioned between the cylinder banks and above the intake manifold. The 24H engine also utilized water injection.

Arsenal 24H rear

On the 24H, the left supercharger fed air to the upper cylinder banks, and the right supercharger fed air to the lower cylinder banks. Note the large engine mounts on the side of the crankcase.

Each cylinder had two spark plugs which were positioned between the two intake valves and the single exhaust valve. The spark plugs were fired by two magnetos positioned at the front of the engine and above the propeller gear reduction housing. The propeller shaft was located on the engine’s centerline and incorporated a .4165 to 1 gear reduction. Although a contra-rotating gear reduction was designed, it is unclear if the unit was ever built, as all available images of the 24H show a single rotation propeller. The 24H and 12H shared cylinder heads, valve trains, most internal components, and many accessories, such as superchargers, fuel pumps, and magnetos.

The Arsenal 24H had a 5.91 in (150 mm) bore and a 6.50 in (165 mm) stroke. The engine’s total displacement was 4,270 cu in (69.98 L). With water injection and over-boosted at 11.0 psi (.76 bar), the 24H produced 4,000 hp (2,983 kW) at 3,250 rpm for takeoff. Without water injection, the 24H produced 3,500 hp (2,610 kW) at 3,250 rpm with 7.8 psi (.54 bar) of boost. The engine’s normal rating with low-speed supercharging was 3,200 hp (2,386 kW) at 3,000 rpm at 7,218 ft (2,200 m). With high-speed supercharging, the 24H had a normal rating of 3,000 hp (2,227 kW) at 3,000 rpm at 18,373 ft (5,600 m). The engine’s cruising power at 2,400 rpm was 2,200 hp (1,641 kW) at 9,843 ft (3,000 m) with low-speed supercharging and 2,000 hp (1,491 kW) at 17,060 ft (5,200 m) with high-speed supercharging. The 24H had a specific fuel consumption of .44 lb/hp/h (268 g/kW/h). The engine was 9.91 ft (3.02 m) long, 3.94 ft (1.20 m) wide, 4.92 ft (1.50 m) tall, and weighed 4,079 lb (1,850 kg).

Arsenal 24H SE 161 Languedoc cowling

Two 24H engines were installed in the inner positions on a Sud-Est SE 161 Languedoc. The tight cowling cannot hide the size of the large the 24H engine. Note the large radiator housing behind the engine. The lower exhaust row of the second 24H engine can be seen on the left side of the photo.

Detail design work of the 24H started in December 1945. By April 1946, the crankcase casting had been made and delivered to Arsenal. The engine was assembled in Arsenal’s factory in Châtillon (near Paris), France and was first run in May 1946. In November 1946, the 24H was exhibited at the Salon de l’Aéronautique (Air Show) in Paris. Issues with the Hispano-Suiza 24Z resulted in the Arsenal 24H being selected for the SNCASE (Sud-Est) SE 580 fighter. However, the SE 580 project was abandoned in 1947, and it does not appear that an Arsenal engine was ever installed. At least three 24H prototypes were built and run for a total of over 1,600 hours. The engine’s predicted performance of 4,000 hp (2,983 kW) was achieved on the test stand.

For flight testing, two 24H engines replaced the inner Pratt & Whitney R-1830 engines on a SNCASE (Sud-Est) SE 161/P7 Languedoc four-engine airliner. The engines were fitted with 10.5 ft (3.2m) diameter, metal, fully adjustable, five-blade propellers built by Ratier. The SE 161/P7 Languedoc with its 24H engines was flown for the first time in 1948. The engines performed well, but the relatively small propellers could not convert all of the 24H’s 4,000 hp (2,983 kW) to thrust. By the time the 24H had flown, the era of large piston aircraft engines was near its end. While the 24H was proposed for a few transports and flying boats (including eight engines used in the Latécorère Laté 182 and 184), new aircraft being built were designed with jet engines. There was no longer a need for a 4,000 hp (2,983 kW) engine, and the 24H was cancelled in 1950.

Arsenal 24H SE 161 Languedoc

The SE 161 Languedoc appearing in a semi-abandoned state. One of the 24H engines has been removed, but exhaust stains are still present behind the remaining engine. Perhaps the aircraft was just used for ground runs when this photo was taken. Note the German aircraft in the background.

Arsenal was experienced with pairing engines in tandem to drive coaxial contra-rotating propellers, and they applied the concept to the 24H engine. Arsenal had developed a drive system for the Arsenal VB 10 fighter using a Vernisse or homocinetic coupling to join sections of the rear engine’s propeller shaft. This coupling incorporated flexibly-mounted ball joints to accommodate deflection and vibration of the propeller shaft. For the 24H Tandem engine, the propeller shaft of the rear engine passed through the crankcase, between the crankshafts, and extended through the propeller shaft of the front engine. The rear engine drove the front propeller of the coaxial contra-rotating unit, while the front engine drove the rear propeller. The Arsenal 24H Tandem displaced 8,541 cu in (139.96 L) and had a takeoff rating of 7,200 hp (5,369 kW), with some sources stating 8,000 hp (5,966 kW). The engine’s normal rating was 6,000 hp (4,474 kW) at 3,000 rpm. With a 39 in (1.0 m) shaft between the engine sections, the Tandem 24H weighed 9,039 lb (4,100 kg). Some sources claim that a 24H Tandem was constructed and run. The engine was considered for a few aircraft, including four 24H Tandem engines used in the Sud-Est 1200 flying boat. Cancellation of the 24H prevented any further development of the Tandem engine.

Arsenal 24H Tandem

The 8,000 hp (5,966 kw) Arsenal 24H Tandem held some potential in a world of large transport aircraft and no jet engines. Fortunately for aviation, the jet engine proved to be both viable and revolutionary.

Sources:
Les Moteurs a Pistons Aeronautiques Francais Tome 2 by Alfred Bodemer and Robert Laugier (1987)
Jane’s All the Worlds Aircraft 1949-1950 by Leonard Bridgman (1949)
Aircraft Engines of the World 1951 by Paul H. Wilkinson (1951)
Junkers Flugtriebwerke by Reinhard Müller (2006)
Les Avions de Combat Francais 1944-1960 I – Chasse-Assaut by Jean Cuny (1988)
Latécorère: Les avions et hydravions by Jean Cuny (1992)
World Encyclopedia of Aero Engines by Bill Gunston (2007)