Yearly Archives: 2012

Napier Cub E66 engine

Napier Cub (E66) – First 1,000 hp Aircraft Engine

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By William Pearce

Early in 1919, Montague Napier, President of D. Napier & Son Ltd., decided that his company should focus entirely on aircraft engines. The company’s first aero-engine, the very successful 450 hp (336 kW) Lion, was in full production. Napier began to think about its replacement, or at least a complementary engine to diversify the product line. Napier approached the British Air Ministry with his new engine plans, and in September 1919, his company was awarded a contract to build six of these new engines at 10,000 GBP each.

Napier Cub E66 engine

The 1,000 hp (746 kW), 16-cylinder Napier Cub. Below the propeller gear reduction are the two duplex carburetors with an induction pipe leading to each cylinder bank.

What Napier had envisioned, and the Air Ministry purchased, was a large power plant of 1,000 hp (746 kW)—enough power for one engine to propel a large bomber aircraft. The engine was given the Napier designation E66 but was referred to as the Cub. Despite its diminutive name, the Cub was a much larger engine than the Lion. The Napier Cub was unlike any engine before or since.

The Napier Cub was a liquid-cooled, 16-cylinder engine with four banks of four cylinders arranged in an X configuration on an aluminum crankcase. The banks were not equally spaced: the angle between the top banks was 52.5 degrees; the banks on either side were angled at 90 degrees; and the angle between the bottom banks was 127.5 degrees. Reportedly, the engine was so arranged to relieve stress on the crankshaft and to ease the engine’s installation in aircraft.

Napier Cub E66 rear

The Napier Cub was the first aircraft engine to exceed 1,000 hp (746 kW). These rear views illustrate the cylinder bank angles, the four magnetos on the back of the engine, the housings for the camshaft drive, and the exposed valves.

The Cub used individual steel cylinders of a 6.25 in (158.75 mm) bore and 7.5 in (190.5 mm) stroke and were encased in separate welded-steel water jackets. The engine displaced 3,682 cu in (60.3 L). The Cub’s compression ratio was 5.3 to 1. The engine was 57 in (1.45 m) wide, 64.25 in (1.63 m) tall, 71.8125 in (1.9 m) long, and weighed 2,450 lb (1,111 kg).

Each of the Cub’s four connecting rods consisted of one master rod and three articulated rods. The pistons were aluminum and had two compression and two oil-scrapper rings. Each cylinder bank had a single overhead camshaft that was driven via a vertical shaft. The vertical shafts were at the rear of the engine and driven from the crankshaft. The overhead camshaft actuated four exposed valves per cylinder. The Cub had a 0.49 propeller gear reduction through the use of spur gears that raised the propeller shaft. The propeller shaft’s bearing arrangement allowed the engine to be used in either a tractor or pusher configuration.

Various parts of the Napier Cub: 1) Connecting rod assembly with one articulated rod attached to the bearing cap. 2) Four-throw crankshaft with roller bearings and spur reduction gear. 3) Propeller shaft with large spur reduction gear. 4) Two of the Cub's cylinders with the valve ports visible on the left cylinder and the water-cooling ports visible on the right cylinder.

Various parts of the Napier Cub: 1) connecting rod assembly with one articulated rod attached to the bearing cap; 2) four-throw crankshaft with roller bearings and spur reduction gear; 3) propeller shaft with large spur reduction gear; 4) two of the Cub’s cylinders with the valve ports visible on the left cylinder and the water-cooling ports visible on the right cylinder.

Dual ignition was provided by four magnetos geared off the rear of the engine. The single water circulation pump was located at the lower rear of the engine, was driven at 1.5 times camshaft speed, and had one outlet to supply each cylinder bank. Two duplex carburetors were located under the gear reduction at the front of the engine. Each carburetor fed two manifolds: one for an upper cylinder bank and the other for a lower bank.

The Napier Cub was first run in late 1920. It was the first aircraft engine to surpass the 1,000 hp (746 kW) mark, achieving 1,057 hp (788 kW) at 1,900 rpm during an early test. The second Cub engine built was first run in early 1922. That same year, the Cub was installed in a modified Avro 549 Aldershot I (J6852, the first prototype) and re-designated Aldershot II. The Aldershot was a long-range, heavy bomber bi-plane. It had a 68 ft (20.7m) wingspan, was 45 ft (13.7 m) long, and weighed around 6,200 lb (2,812 kg). The Cub-powered Aldershot II first flew on 15 December 1922, piloted by Bert Hinkler. The Aldershot II continued to fly for about four years before the Napier Cub was removed and another test engine (an 800 hp / 597 kW Beardmore Typhoon) was installed.

Napier Cub-powered Avro Aldershot II (J6852). This was the first Aldershot prototype, originally powered by a 650 hp Rolls-Royce Condor V-12 engine. To support the Cub, the aircraft had its main gear doubled to four wheels. After three years of Cub-power, the aircraft was re-engined with an 800 hp Beardmore Typhoon (straight-six semi-diesel).

Napier Cub-powered Avro Aldershot II (J6852). This was the first Aldershot prototype, originally powered by a 650 hp (485 kW) Rolls-Royce Condor V-12 engine. To support the Cub, the aircraft was strengthened and had its main gear doubled to four wheels. After two years of Cub-power, the aircraft was re-engined with an 800 hp (597 kW) Beardmore Typhoon.

A Napier Cub was also installed in both of the two Blackburn T.4 Cubaroos built. The Cubaroo was a long-range coastal defense bi-plane capable of carrying a 21-in (.533 m) torpedo or equivalent bomb load of 2,000 lb (907 kg). The aircraft had an 88 ft (26.8 m) wingspan, was 54 ft (16.5 m) long, and weighed 9,632 lb (4,396 kg) empty and 19,020 lb (8,709 kg) fully loaded. The Cubaroo was possibly the largest single-engine aircraft in its day. The first Cubaroo (N166) took to the air in the summer of 1924, piloted by P.W.S. ‘George’ Bulman. The aircraft was delivered to Martlesham Heath for flight trials in October 1924. Several engine failures were noted as well as a tendency for the engine to overheat during a high-power climb.

The second Cubaroo (N167) had a revised radiator and first flew in early 1925. Both Cubaroo aircraft were flown in various aviation displays and used for testing. N166 was damaged beyond repair in a landing accident on July 16, 1926. N167 continued to fly with Cub-power until 1927, when it was re-engined to test the 1,100 hp (820 kW) Beardmore Simoon.

The first Blackburn Cubaroo (N166) in flight. The 1,000 hp Cub seemed to be quite adequate for the aircraft.

The first Blackburn Cubaroo (N166) in flight. The 1,000 hp (746 kW) Cub seemed to be quite adequate for the large aircraft.

Another aircraft designed to use the Napier Cub was the Avro 556. With a wingspan over 95 ft (30 m), this aircraft was even larger than the Cubaroo, although intended for the same purpose of carrying a 21-in (.533 m) torpedo. This aircraft was never built; instead, the basic design was used for the twin Rolls-Royce Condor-powered Avro 557 Ava.

By June 1925, the concept of a single, large aircraft engine powering a very large aircraft fell to the wayside in favor of multiple engines, which gave some degree of enhanced safety. The Air Ministry lost its interest in the Napier Cub, and the world’s first 1,000 hp (746 kW) aircraft engine faded to obscurity.

The second Blackburn Cubaroo (N167) with the revised radiator to cool the Napier Cub.

The second Blackburn Cubaroo (N167) with the revised radiator to cool the Napier Cub.

Sources:
– Aerosphere 1939 by Glenn Angle (1940)
– Men and Machines by Wilson and Reader (1958)
– By Precision Into Power by Alan Vessey (2007)
– Avro Aircraft since 1908 by A J Jackson (1965/1990)
– Blackburn Aircraft since 1909 by A J Jackson (1968/1989)
– The British Bomber since 1914 by Francis Mason (1994)
– British Flight Testing: Martlesham Heath 1920-1939 by Tim Mason (1993)

Yokosuka (Kugisho) R2Y1 Keiun

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By William Pearce

Late in 1938, the Heinkel He 119 experimental high-speed reconnaissance aircraft was shown to a Japanese Naval delegation visiting Germany. The Japanese liked the speed and range of the He 119, and overall, were impressed by the aircraft. Based on the positive initial interest, the Japanese sent a group of technicians from the Yokosuka Naval Air Technical Arsenal (Yokosuka, also known as Kaigun Koku Gijutsusho or Kugisho) to Germany for a closer examination of the He 119. Eventually, Commander Hideo Tsukada was able to purchase two He 119 prototypes and a license to manufacture the aircraft in Japan.

The standard image of the Yokosuka R2Y1 Keiun. Speculation suggests the first scoop on the side of the aircraft provided cooling air for the engine's internal exhaust baffling, the second, larger scoop provided induction air for the normally aspirated Aichi [Ha-70] engine installed in the prototype, and the final two ports were for the engine's exhaust.

The standard image of the Yokosuka R2Y1 Keiun. Speculation suggests the first scoop on the side of the aircraft provided cooling air for the engine’s internal exhaust baffling, the second, larger scoop provided induction air for the normally aspirated Aichi [Ha-70] engine installed in the prototype, and the final two ports were for the engine’s exhaust.

The two He 119 prototypes were delivered via ship to Japan in 1941 (some say 1940). The aircraft were reassembled at Kasumigaura Air Field, and flight tests occurred at Yokosuka Naval Base. During an early test flight, one of the He 119s was badly damaged in a landing accident, and it is believed the other He 119 suffered a similar fate. Plans to produce the He 119 never moved forward, but the Japanese were still interested in a high-speed reconnaissance aircraft and felt the general configuration of the He 119 held promise.

Inspired by the Heinkel He 119, Yokosuka began to design an aircraft of a similar layout, known as the Y-40, in 1943. Headed by Commander Shiro Otsuki, the aircraft project was a pressurized, two-seat, unarmed, high-speed, reconnaissance aircraft of all-metal construction that featured tricycle retractable gear. The design was approved, and the Y-40 officially became known as the R2Y1 Keiun (Beautiful Cloud). The construction of two prototypes was ordered.

A good view of the R2Y1 where a radiator inlet can be seen under the wing and in front of the main gear. The ventral scoop was an intake for the turbocharger and intercooler but these were not installed on the prototype.

A good view of the R2Y1 where a radiator inlet can be seen under the wing and in front of the main gear. The ventral scoop was an intake for the turbocharger and intercooler but these were not installed on the prototype.

The R2Y1 had a 45.93 ft (14 m) wingspan and was 42.81 ft (13.05 m) long. The aircraft stood 13.91 ft (4.24 m) high, weighed 13,260 lb (6,015 kg) empty, and had a maximum weight of 20,725 lb (9,400 kg). The Keiun had an estimated top speed of 447 mph (720 km/h) at 32,810 ft (10,000 m) and a cruise speed of 288 mph (463 km/h) at 13,125 ft (4,000 m). Maximum range was an estimated at 2,240 mi (3,610 km). The pilot sat under a raised bubble-style canopy that was toward the extreme front of the aircraft. The radio operator/navigator occupied an area in the fuselage just behind and a little below the pilot.

The Keiun was powered by two 60-degree, inverted V-12 Aichi Atsuta 30 series engines, licensed-built versions of the Daimler-Benz DB 601. The engines were coupled together by a common gear reduction in a similar fashion as the DB 606. The resulting 24-cylinder power unit was known as the Aichi [Ha-70]. With a 5.91 in (150 mm) bore and 6.30 in (160 mm) stroke, the engine displaced 4,141 cu in (67.8 L) and was installed behind the cockpit and above the wings. The Aichi [Ha-70] engine was to be turbocharged and rated at 3,400 hp (2,535 kW) for takeoff and 3,000 hp (2,237 kW) at 26,247 ft (8,000 m). Without the turbocharger, the engine was rated at 3,100 hp (2,312 kW) for takeoff and 3,060 hp (2,282 kW) at 9,843 ft (3,000 m). The engine drove a 12.47 ft (3.8 m), six-blade propeller via a 12.8 ft (3.9 m) long extension shaft that ran under the cockpit. Engine cooling was achieved by radiators under the fuselage and inlets for oil coolers in the wing roots. A ventral air scoop was located behind the engine to provide induction air for the turbocharger and air for the intercooler.

The R2Y1 Keiun undergoing taxi tests in May 1945.

The R2Y1 Keiun undergoing taxi tests in May 1945.

By the fall of 1944, the direction of the war had changed, and Japan no longer needed a high-speed reconnaissance aircraft. The R2Y1 Keiun was all but cancelled when the design team suggested the aircraft could easily be made into a fast attack bomber. In addition, the Aichi [Ha-70] power plant would be discarded, and one 2,910 lb (1,320 kg) thrust Mitsubishi Ne 330 jet engine would be installed under each wing. A fuel tank would be installed in the space made available by the removal of the piston engine. This jet-powered attack bomber had an estimated top speed of 495 mph (797 km/h). The project was approved, and the new aircraft was designated R2Y2.

The decision was made to finish the nearly completed R2Y1 airframe and use it as a flight demonstrator to assess the flying characteristics of the aircraft. With pressurization, the turbocharger, and the intercooler omitted, the R2Y1 prototype was completed in April 1945 and transferred to Kisarazu Air Field for tests. Ground tests revealed that the aircraft suffered from nose-wheel shimmy and engine overheating.

Yokosuka R2Y1 Keiun taking off from Kisarazu Air Field for its first an only flight.

Yokosuka R2Y1 Keiun taking off from Kisarazu Air Field for its first an only flight.

Adjustments were made to overcome the issues, and the Keiun took to the air on 29 May 1945 (date varies by source and is often cited as 8 May 1945), piloted by Lt. Commander Kitajima. The flight proved to be very short because the engine quickly overheated, and a fire broke out in the engine bay. Lt. Commander Kitajima quickly returned to the field, and the R2Y1 suffered surprisingly little damage. On 31 May during a ground run to test revised cooling, the engine was mistakenly run at high power for too long and overheated. The engine was removed from the aircraft to repair the damage. The R2Y1 sat awaiting repair for some time before it was destroyed by Japanese Naval personnel to prevent its capture by American forces (some say it was destroyed in an Allied bombing raid). Because of the end of the War, the second R2Y1 prototype was never completed nor was the design work for the R2Y2.

The unfinished second R2Y1 prototype as seen at the end of WWII. Note the wing root and ventral intakes. The hole in the center of the bulkhead in the nose was for the propeller's drive shaft.

The unfinished second R2Y1 prototype as seen at the end of WWII. Note the wing root and ventral intakes. The hole in the center of the bulkhead in the nose was for the propeller’s drive shaft.

Sources:
– “Yokosuka R2Y1 Keiun: Japan’s mid-engined twin” Wings of Fame, Volume 12 (1998)
– Japanese Secret Projects by Edwin Dyer (2009)
– Japanese Aircraft of the Pacific War by Rene Francillon (1970/2000)
– Japanese Aero-Engines 1910–1945 by Mike Goodwin and Peter Starkings (2017)
– General View of Japanese Military Aircraft in the Pacific War by Airview (1956)
– Japanese Aircraft Performance & Characteristics TAIC Manual by Edward Maloney (2000)
– http://www.secretprojects.co.uk/forum/index.php/topic,15633.0/all.html

Heinkel He 119 V4 front

Heinkel He 119

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By William Pearce

In the 1930s, brothers Siegfried and Walter Günter were pushing the limits of aerodynamics as they designed aircraft for Heinkel Flugzeugwerke in Germany. Perhaps the ultimate expression of their aerodynamic beliefs was the Heinkel He 119. The Günter brothers and Ernest Heinkel envisioned the He 119 as an unarmed, high-speed reconnaissance aircraft or light bomber.

Heinkel He119 V1 side

Heinkel He 119 V1 prototype with the hastily installed radiator to augment the evaporate cooling system.

Work on the He 119 began in the summer of 1936 as a private venture funded by Heinkel Flugzeugwerke. The aircraft appeared to have a fairly standard layout as an all metal, low-wing monoplane with retractable gear. However, the very streamlined fuselage hid the He 119’s unorthodox power arrangement. To achieve the low-drag necessary for high-speed operations, the engine was buried in the fuselage, just behind the cockpit and above the wings. An enclosed drive shaft extended forward from the engine, through the cockpit, between the pilot and co-pilot, and to the front of the aircraft where it drove a 14 ft 1 in (4.30 m), metal, variable-pitch, four-blade propeller.

No engine produced the power needed for the He 119, so two Daimler-Benz DB 601 engines were placed side-by-side and coupled together through a common gear reduction. The DB 601 was a liquid-cooled, 12-cylinder, 60 degree, inverted Vee engine with a 5.91 in (150 mm) bore and 6.30 in (160 mm) stroke. When coupled, the 24-cylinder engine was known as the DB 606; it displaced 4,141 cu in (67.8 L) and produced 2,350 hp (1,752 kW). The inner banks of the DB 606 were pointed nearly straight down and exhausted under the aircraft. The side banks’ exhaust was expelled just above the He 119’s wings.

Daimler-Benz DB 606

The Daimler-Benz DB 606 engine was comprised of two DB 601 engines joined to a common gear reduction.

The DB 606 engine in the He 119 was to be cooled exclusively by surface evaporative cooling, where steam from the heated coolant was pumped under the skin of the wing’s center section. Here, the steam would cool and condense back into liquid. The liquid was then pumped back to the engine. However, during testing the system proved to be inadequate, and a radiator was added below the fuselage, just before the wings. The first prototype had a fixed radiator that was rather hastily installed. The subsequent prototypes included an improved radiator that was extended during low-speed operations but was semi-retracted into the fuselage as the aircraft’s speed increased.

The He 119’s cockpit formed the nose of the aircraft. The cockpit was entirely flush with the 48 ft 7 in (14.8 m) fuselage and was extensively glazed with heavily framed windows. The pilot and co-pilot accessed the cockpit by separate sliding roof panels. In the aft fuselage were provisions for a radio operator and a ventral bay for cameras. Another bay for either large cameras or a maximum of 1,200 lb (1,000 kg) of bombs was located in fuselage, just aft of the wing spar.

Heinkel He 119 nose radiator

A good view of the He 119’s glazed cockpit is provided in this image. Most sources state this aircraft is V4, but it possesses the exhaust ports of V1. Note the extended radiator.

The He 119 had a wingspan of 52 ft 6 in (16 m). To provide for proper ground clearance, conventional main landing gear would have been too long to fit in the inverted-gull, semi-elliptical wing. A telescoping strut was devised that would collapse as the gear retracted. This allowed the gear to fit within the wing and also extend to provide the needed ground clearance.

Heinkel kept the He 119 a secret during construction, and the first prototype (V1) flew in June 1937 with Gerhard Nitschke at the controls. Even with the bulk of the added radiator, the aircraft achieved 351 mph (565 km/h), which was faster than fighter aircraft of the day. This speed validated Heinkel and the Günter brothers’ position that the fast bomber did not need to be armed. However, when the aircraft was revealed to German officials, they insisted the aircraft be armed with upper and lower guns operated by separate gunners. German officials did allow the continued experimentation of the aircraft; at this point, the aircraft was officially designated He 119. The addition of the guns lowered the aircraft’s speed, and it appears that only the upper gun was included in other prototypes, housed under a sliding panel.

Heinkel He 119 V2 with windows in the rear fuselage for the radio operator.

Heinkel He 119 V2 with windows in the rear fuselage for the radio operator. Reportedly, this is the last He 119 built with the semi-elliptical wing.

It is at this point that sources disagree on the He 119’s history. One theory is that the second prototype (V2) first flew in September 1937, followed by the fourth prototype (V4) in October 1937. The He 119 V4 set a speed record on 22 November 1937 and was destroyed in a follow-up attempt on 16 December. A total of eight aircraft were built; the seventh (V7) and eighth (V8) were purchased by and subsequently shipped to Japan.

The other theory, supported by German Heinkel expert Dr. Volker Koos, is that the V1 was prepared (which included the installation of a new radiator as used on the subsequent prototypes) for the record flight. The V1 flew the record flight and crashed during the follow-up attempt. The first flight of V2 was in 1938, and V4 first flew in May 1940. Most likely, only four aircraft were built, and V2 and V4 were shipped to Japan.

Side view of the He 119 V3. The updated wing used on the V3 and all further He 119 aircraft can be seen as well as tail modifications to increase the seaplanes stability.

Side view of the He 119 V3. The updated wing used on the V3 and all further He 119 aircraft can be seen as well as tail modifications to increase the seaplane’s stability.

All sources agree that the He 119 carrying the registration D-AUTE made the record flights. The third prototype (V3) was first flown after V4 because V3 was built as a seaplane. All prototypes from V3 on were built with a new wing that had a straight leading edge and a slightly reduced span of 52 ft 2 in (15.9 m).

After careful examination of various photos, it appears that the He 119 registered at D-AUTE had the semi-elliptical wing as used on the first two prototypes. It also appears that the exhaust ports above the wing on V1 were unique and at an angle, with each port slightly higher (relative to the fuselage) than the port preceding it. All other He 119s had exhaust ports in a straight line relative to the fuselage. D-AUTE appears to have the ports as seen on V1. Based on the information available, it seems more likely that V1 did indeed make the record flights. Sadly, given the secrecy under which the He 119 was built, the propaganda subterfuge surrounding the record flights, and the destruction of German documents during World War II, the exact aircraft identities as well as the number built may never be definitively known.

Heinkel He 119 V3 b

The Heinkel He 119 V3 seaplane taxiing under its own power. This aircraft was to be used on an attempt to set a new 1000 km (621 mi) seaplane record, but such plans were cancelled after the other He 119’s crash.

Regardless of the specific airframe, on 22 November 1937, the He 119 set a world record for flying a payload of 1,000 kg (2,205 lb) over a distance of 1,000 km (621 mi). For propaganda purposes, the He 119 was labeled He 111U and also He 606. Due to weather, the He 119 was forced to fly lower than anticipated which reduced its airspeed. Even though the He 119 set the record at 313.785 mph (504.988 km/h), the speed was seen as a disappointment that did not represent the He 119’s true capabilities. Indeed, the record was broken about two weeks later by an Italian Breda Ba 88.

A follow-up flight to reclaim the record occurred on 16 December 1937.  With over half the distance flown and the He 119 averaging just under 370 mph (595 km/h), the DB 606 engine quit. The pilots, Nitschke and Hans Dieterle, attempted an emergency landing at Travemünde but hit a drainage ditch. The He 119 was destroyed; Nitschke and Dieterle were injured, but they survived. The engine failure was a result of a faulty fuel transfer switch. After the crash, Heinkel was ordered not to attempt any further record flights with the He 119.

Heinkel He 119 V4 front

Many sources identify this aircraft (D-ASKR) as the He 119 V2. Interestingly, the wing root intake for the supercharger and lower lip of the radiator do not match those found on other images of V2. The features do match those found on V3.

Other He 119 prototypes took over the test flights. He 119s with the new wing demonstrated a top speed of around 370 mph (595 km/h) and a range of 1,865 mi (3,000 km). Despite the floats, the He 119 V3 seaplane had a top speed of 354 mph (570 km/h) and a range of 1,510 mi (2,430 km). The V3 aircraft also had a ventral fin added to counteract the destabilizing effects of the floats. Unfortunately, the German authorities did not have any interest in producing the He 119 in any form because of its unorthodox features. Reportedly, some of the remaining aircraft served as test-beds for the DB 606 and DB 610 engines. The remaining He 119s in Germany were scrapped during World War II.

Late in 1938, the He 119 was shown to a Japanese Naval delegation that expressed much interest in the aircraft. In 1940 the Japanese purchased a manufacturing license for the He 119 along with two of the prototype aircraft. These aircraft were delivered via ship to Japan in 1941 (some say 1940). The aircraft were reassembled at Kasumigaura Air Field, and flight tests occurred at Yokosuka Naval Base. During an early test flight, one of the He 119s was badly damaged in a landing accident, and it is believed the other He 119 suffered a similar fate. While it was not put into production, the He 119 did provide the Japanese with inspiration for the Yokosuka (Kugisho) R2Y1 Keiun high-speed reconnaissance aircraft.

Heinkel He 119 V2 with the Japanese Naval delegation.

The Heinkel He 119 with the Japanese Naval delegation. The sliding roof panel for the pilot’s cockpit access can clearly be seen. Note the differences with the wing root intake and lower lip of the radiator compared to the D-ASKR aircraft.

Sources:
– “An Industry of Prototypes – Heinkel He 119”, Wings of Fame, Volume 12 by David Donald (1998)
– Warplanes of the Third Reich by William Green (1970/1972)
– http://www.whatifmodelers.com/index.php/topic,21627.0/
– http://forum.12oclockhigh.net/showthread.php?t=14198

Rolls-Royce Exe (Boreas) and Pennine Aircraft Engines

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By William Pearce

Arthur Rowledge was one of the most prolific designers of piston aircraft engine in history. In 1913 he joined Napier & Son where he designed the firm’s first aircraft engine, the Lion, in 1917. This engine went on to achieve great success and was even used during World War II, but Rowledge moved on to Rolls-Royce (R-R) in 1921. While at R-R, Rowledge was very involved with the Condor III, Kestrel, “R” Schneider, and Merlin engines. Rowledge also designed the air-cooled and sleeve-valve Exe and Pennine engines. These two engines were quite a departure from standard R-R practice and never made it to production status.

Side view of the Rolls-Royce Exe engine. The cylinder baffling in the image is of a simple construction when compare to the other engine image below. It appears to be the same baffling as seen on the engine installed in the Battle.

In the 1930s Rowledge became seriously ill and took a leave from R-R. During his recovery, R-R decided not to bring him back to the main engine development programs but to give him complete control of designing a new engine. This new engine was based on a 1,000 hp (746 kW) requirement from the Fleet Air Arm for shipboard aircraft use where air-cooling was preferred. The new engine was sanctioned in February 1935 and originally called Boreas, but the name was later changed to Exe.

The Exe engine had four banks of six cylinders in an X configuration. Each bank was 90 degrees from the next. The cylinders had a 4.225 in (107.3 mm) bore and 4.0 in (101.6 mm) stroke, for a total displacement of 1,346 cu in (22.1 L). The Exe had a two-speed, single-stage supercharger, and the compression ratio was 8 to 1. The engine weighed 1,530 lb (694 kg). The two spark plugs for each cylinder were fired by coil ignition rather than standard magnetos. A 0.358 gear reduction to the propeller was achieved through spur gears; their arrangement elevated the propeller shaft centerline above the crankshaft.

Clear view of the Rolls-Royce Exe and the baffling around each cylinder to direct air for proper cooling. The baffling appears to be an updated version compared to the image above. Also note how the spur reduction gear has elevated the propeller thrust line.

The sleeve-valves, undoubtedly inspired by Harry Ricardo, followed the established Burt-McCollum/Bristol practice. Each cylinder barrel had three intake ports and two exhaust ports. The sleeve itself had only four ports, one was shared as an intake and exhaust port. The drive cranks for the sleeve valves were driven via spiral gears from a shaft that ran along each side of the engine. A.A. Rubbra states that these shafts were driven from the propeller gear reduction. The single sleeve for each cylinder was sealed by the use of a junk head. The entire system proved to be quite reliable.

The connecting rods consisted of one master rod and three articulating rods. The big end was essentially a square with the master rod extending from one corner and the three articulated rods attached to each of the other corners. The big end was split and bolted together around the crankshaft via four bolts.

A specialized pressure air-cooling method was used. Cooling air entered the engine cowling below the spinner. The air was then fed into the upper and lower Vees. Baffles attached to the individual cylinders caught and directed the air through the cylinder’s cooling fins. The air passed from the upper and lower Vees into the side Vees and exited toward the rear of the engine cowling. Reportedly, the arrangement worked very well with minimal drag and no cooling issues. Induction manifolds delivered the air/fuel mixture to the cylinders through the top and bottom Vees. Exhaust from the cylinders was collected in manifolds on the side Vees.

A great image of the Exe installed in the Battle with the cowling removed. Note early version of the cylinder baffling.

The Exe was originally rated at 920 hp (686 kW) at 3,800 rpm. The engine was first run in September 1936, and it had completed a 40-hour development test by the end of 1937. The Exe first took to the air in a modified Fairey Battle (K9222) on 30 November 1938. This particular aircraft was owned by R-R and was modified at the R-R Flight Development Establishment at Hucknell. Exe engine development continued with very little trouble; however, the engine did suffer from excessive oil consumption. Ultimately the engine’s output was increased to 1,200 hp (895 kW) at 4,200 rpm, and continued development to 1,500 hp (1,119 kW) was planned.

A liquid-cooled version of the engine was also studied. A four cylinder test engine representing an X configuration was run in 1938. Each cylinder of the test engine had its own steel water jacket. The program progressed, and a complete liquid-cooled X-24 engine was built; this engine featured normal cast aluminum cylinder blocks with integral water jackets. Reportedly, this engine was run and tested but never flew.

Rolls-Royce Exe installed in Fairey Battle K9222. Note the cooling air intake under the spinner and exit by the exhaust stacks. The Exe-powered Battle continued to fly long after the engine was cancelled.

The Exe was originally intended to power the Fairey Barracuda torpedo-bomber and the production Fairey F.C.1 four-engine transport. With the start of World War II, top priority was given to developing and producing Merlin and Griffon engines. Ernest Hives, R-R General Works Manager, estimated that building 275 Exe engines would be the production equivalent of 1,200 Merlins. At his request, work on the Exe program was suspended in September 1939 and stopped completely by 1941. Development was also discontinued on the liquid-cooled engine. The Barracuda was switched to Merlin power, and the F.C.1 was never built.

As an indicator of the engine’s sound design and reliability, the Exe-powered Battle continued to fly until 1943, long after the Exe program was cancelled. In addition, R-R’s Exe-powered Battle flew at higher speeds than the standard Merlin-powered Battles.

The encouraging results from the Exe compelled a small design team to continue work on the air-cooled, sleeve-valve engine concept. Around June 1943, design work was accepted on what was essentially an enlarged Exe. The new engine project was known as the Pennine and was headed by Dr. Sprinto Viale.

Rolls-Royce Pennine engine shown without any exhaust stacks or spark plug leads. The cylinders look very similar to those used by Bristol. The ring of studs around the propeller shaft is where the annular cooling fan would attach.

The Pennine had the same layout as the Exe, with the exception of the propeller gear reduction. Rather than spur gears, which would raise the propeller shaft as on the Exe, the Pennine used epicyclic (planetary) gears that allowed the propeller shaft to be in-line with the crankshaft. A propeller gear reduction of .3 or .4 was used. In addition, an annular cooling fan was driven from the gear reduction at 1.03 times crankshaft speed. Illustrations done by Lyndon Jones show the drive shafts for the sleeve valves geared to the rear of the crankshaft rather than to the gear reduction. It is possible this deviation from the Exe’s design was a result of the aforementioned changes to the gear reduction. Design work on the engine was completed by September 1944.

Another change from the Exe that can be seen in the Jones illustration was the connecting rod arrangement. Rather than having a split big end, the Pennine utilized a one piece master connecting rod with three articulated rods. The crankshaft’s crankpins were bolted together through the one piece master rods.

The Pennine engine had a 5.4 in (137.2 mm) bore and 5.08 in (129 mm) stroke, giving a total displacement of 2,792 cu in (45.8 L); this was over twice the displacement of the Exe. With a dry weight of 2,850 lb (1,293 kg), the Pennine was 106 in (2.69 m) long, 37.5 in (.95 m) tall, and 39 in (.99 m) wide. The engine was equipped with a single stage, two speed supercharger that provided 12 psi (.83 bar) of boost at takeoff and combat power settings. The Pennine developed 2,750 hp (2,051 kW) at 3,500 rpm at sea-level and up to 2,800 hp (2,088 kW) under combat settings. A reliable 3,000 hp (2,237 kW) was thought to be easily obtainable with further development.

Pennine sectional view from Sectioned Drawings of Piston Aero Engines* by Lyndon Jones. Note the annular fan and sleeve valve drives.

Only one or two Pennine test engines were built; the first was finished on 31 December 1944. The engine was run on teststands during 1945, and an engine cowling was developed to maximize the efficiently of the pressurized air-cooling. While the engine ran well, the end of piston-powered military aircraft and civil airliners was on the horizon, with piston engines being supplanted by jet engines. Possible applications for the Pennine engine were the Fairey Spearfish torpedo bomber and the Miles X.11 airliner. Ultimately, the Spearfish was powered by a Bristol Centaurus. The Miles aircraft lost out to the Bristol Brabazon and was never built. Development of the Pennine was stopped in mid to late 1945.

A further engine study was made where two 16-cylinder power sections (using Pennine cylinders) of an X configuration were attached to a common crankcase. This arrangement made an X-32 engine and was known as the Snowden. A shaft from the midsection, between the two X-16 power sections, was to travel forward along the top and bottom Vees of the engine to a gear reduction that drove half of a coaxial contra-rotating propeller unit. This engine would have displaced 3,723 cu in (61.0 L) and produced 4,000 hp (2,983 kW). Some testing was done, but a complete engine was never built.

Rear view of the Pennine engine and cowling. Note the baffling for each individual cylinder and the circular front of the cowling for the annular cooling fan..

Sources:
– Rolls-Royce Piston Aero Engines — A Designer Remembers by A.A. Rubbra (1990)*
– Rolls-Royce Aero Engines by Bill Gunston (1989)
– British Piston Aero Engines and their Aircraft by Alec Lumsden (1994/2003)
– Major Piston Engines of World War II by Victor Bingham (1998/2001)
– Allied Aircraft Piston Engines of World War II by Graham White (1995)
– Sectioned Drawings of Piston Aero Engines by Lyndon Jones (1995)*
– Rolls-Royce — Hives, the Quiet Tiger by Alec Harvey-Bailey (1985)
– http://www.secretprojects.co.uk/forum/index.php?topic=5375.0
– “Rolls-Royce and the Sleeve Valve” by Phil Kennedy, New Zealand Rolls-Royce & Bentley Club Inc, Issue 07-3 2007 (pdf)
– http://en.wikipedia.org/wiki/Arthur_Rowledge

*Rolls-Royce Heritage Trust books that are currently in print and available from the Rolls-Royce Heritage Trust site.

Fokker F.XX Zilvermeeuw Transport

5 Replies

By William Pearce

In the never-ending quest for speed, KLM (Royal Dutch Airlines) asked the Fokker Aircraft Corporation to design an aircraft for its East Indies route that could fly some 35 mph (56 km/h) faster than the Fokker F.XVIII then in service. Fokker’s response was a trimotor design that could accommodate 12 passengers and three crew members. The new aircraft, the Fokker F.XX Zilvermeeuw (Herring Gull), was the last wooden aircraft and last trimotor built by Fokker. However, it was the first Fokker-built aircraft with retractable landing gear.

The Fokker F.XX: the pinnacle of the Fokker trimotors.

The Fokker F.XX was revealed on 20 December 1932. The aircraft was built under the direction of Marius Beeling and featured a fabric covered fuselage of steel tube construction. The fuselage used an elliptical cross section, another design-first for Fokker, who had used rectangular fuselages on their earlier aircraft. The F.XX’s high-wing had a wooden structure and was plywood covered. The plywood skin was omitted from the lower wing section running through the cabin so that more headroom was available for the passengers.

The aircraft was originally powered by three 650 hp (485 kW), nine-cylinder, air-cooled Wright Cyclone R-1820-F engines, all housed in NACA cowlings. One engine was in the nose of the aircraft, and the others were each in a nacelle suspended under each wing by struts. Later, KLM replaced the engines with more powerful 690 hp (515 kW) Wright Cyclone R-1820-F.2 engines. Metal, two-blade, ground-adjustable propellers were initially used. However, when the uprated engines were installed, metal Hamilton Standard propellers that were adjustable in-flight were used.

The Fokker F.XX under constructions in 1933.

The Fokker F.XX was 54.8 ft (16.7 m) long and had a span of 84.3 ft (25.7 m). The aircraft weighed 11,795 lb (5,350 kg) empty and 19,510 lb (8,850 kg) loaded. Range with full fuel was 1,056 mi (1,700 km), and range with full payload was 400 mi (645 km). The aircraft’s service ceiling was 21,650 ft (6,600 m). Maximum speed of the F.XX was 190 mph (305 km/h), and cruise speed was 155 mph (250 km/h).

The F.XX carried the Dutch registration PH-AIZ and made its first flight on 3 June 1933, piloted by Emil Meineche. For this first flight, the engine cowlings were omitted and the undercarriage was not retracted. During a test on 29 June 1933, it was found that heavy aileron vibration occurred as speed was increased. This phenomenon was solved by adding 70 lb (32 kg) of balance weights to the ailerons. Flight testing resumed on 11 August 1933.

The F.XX probably undergoing early flight tests with the large gear doors still installed and short engine nacelles.

It was also discovered that when the landing gear was deployed, the large door in front of each main wheel caused turbulence that resulted in severe vibrations of the tail section. The doors were reduced in size, but the problem persisted. Eventually, the doors were removed altogether. During the flight test program, the engine nacelles were lengthened to reduce drag. The flight test program, the airworthiness trials, and the acceptance flights were completed over the course of four months, encompassing 62 flights that totaled 37 hours in the air.

On 18 December 1933, the Fokker F.XX made its KLM debut on a special Christmas mail flight to the East Indies. The objective was to fly as fast as possible to the Dutch colonies in competition with another aircraft, the Pander S.4 Postjager, to inaugurate a special mail service.

Inflight image of the Fokker F.XX showing its graceful lines.

The Pander Postjager had departed earlier but was stranded in Italy because of an engine failure, leaving the Fokker F.XX poised to win the competition. However, engine trouble was experienced during a warm-up, and the F.XX was grounded. Work to repair the F.XX would take too much time, and KLM quickly prepared a Fokker F.XVIII for the Christmas flight. It was a disastrous public failure for the new F.XX, one from which it never fully recovered.

Although the F.XX was a more advanced design than earlier Fokker aircraft, the eminent arrival of twin-engine, low-wing, metal aircraft (like the Douglas DC-2) rendered it obsolete. In addition, the negativity surrounding the failed Christmas flight meant that there would no production contract for the Fokker F.XX. Quietly and shrewdly, Fokker Aircraft Corporation obtained manufacturing rights for the DC-2.

The F.XX with the gear doors removed and lengthened engine nacelles.

However, the F.XX’s reputation was boosted when KLM began using the aircraft on a fast London-Amsterdam-Berlin service starting 1 March 1934. On the Amsterdam-Berlin leg of the flight, the aircraft achieved an impressive average speed of 157 mph (253 km/h). Also in 1934, the F.XX flew 1,535 hours; this was nearly double KLM’s 850 flight hour average with the F.XVIII.

The F.XX was in service with KLM for only a few years. In September 1936, the aircraft was sold to Alain Pilain of France and registered as F-APEZ. Mr. Pilain represented the fictitious airline Air Tropique, which was a cover for another organization: the Société Française de Transports Aériens (SFTA). SFTA was a purchasing agent for the Spanish Republicans disguised as a French air transport service.

The Fokker F.XX in service with the Spanish Republicans and with a camouflage paint scheme as seen at Le Bourget, France in 1937.

SFTA flew the aircraft to Spain in October 1936, where it carried the governmental registration EC-45-E and was used in the Spanish Civil War. The F.XX was painted in a camouflaged scheme and used to transport various cargoes (including gold bullion and jewelry) between Spain and France.

It was not a very popular aircraft, especially after one of its Wright engines was replaced with a Walter-built Mercury engine from a Letov S-231 fighter, and at least one other engine was replaced with a Shvetsov M-25 engine from Polikarpov I-16 fighter. The engine changes resulted in a vicious yaw on takeoff. The F.XX served with the Republicans until early February 1938 when, piloted by Eduardo Soriano, it was destroyed in a crash near Barcelona at Prat de Llobregat Airport.

The following is a video of the Fokker F.XX Zilvermeeuw filmed in 1933 and uploaded by BeeldenGeluid.


Sources:
– “The Fokker F.XX,” Flight (5 October 1933)
– “Fokker’s Trimotors Go To War,” Air Enthusiast, No. 13 August–November 1980 by Gerald Howson
– Jane’s All the World’s Aircraft 1934 by C.G. Grey (1934)
– Aircraft of the Spanish Civil War 1936-1939 by Gerald Howson (1990)
– Fokker: Aircraft Builders to the World by Thijs Postma (1979/1980)
– http://www.dutch-aviation.nl/index5/Civil/index5-2%20F20.html

Curtiss H-1640 Chieftain Aircraft Engine

3 Replies

By William Pearce

In April 1926 the Curtiss Aeroplane and Motor Company initiated a design study for a 600 hp (447 kW), air-cooled aircraft engine. The engine was to have minimal frontal area while keeping its length as short as possible. Configurations that were considered but discarded were a 9-cylinder single-row radial, a 14-cylinder two-row radial, a 12-cylinder Vee, and a 16-cylinder X. The selected design was a rather unusual 12-cylinder engine that Curtiss referred to as a “hexagon” configuration. This engine was built as the Curtiss H-1640 Chieftain.

The Curtiss H-1640 Chieftain “hexagon” or “inline-radial” engine. The image on the left was taken in 1927; note “Curtiss Hexagon” is written on the valve covers. In front of each cylinder pair is the housing for the vertical shaft that drove the overhead camshafts. The image on the right was taken in 1932 and shows a more refined engine with “Curtiss Chieftain” written on the valve covers. Note the additional cooling fins surrounding the spark plugs. In both images, the baffle at the rear of each exhaust Vee forced cooling air into the intake Vee.

The Curtiss H-1640 was designed by Arthur Leak and Arthur Nutt. The Chieftain’s “hexagon” design was a combination of a radial and Vee engine. The intent was to combine the strengths of both engine configurations: the light and short features of a conventional radial with the narrow and high rpm (for the time) of a conventional Vee engine.

The Chieftain was arranged as if it were a 12-cylinder Vee engine cut into three sections, each being a four-cylinder Vee. The Vee engine sections were then positioned in a radial form 120 degrees apart (each cylinder bank being 60 degrees apart). The end result was a two-row, twelve-cylinder, inline radial engine. The H-1640 resembled a conventional radial engine except that the second cylinder row was directly behind the first.

An engine installation comparison of the air cooled Chieftain-powered XO-18 Falcon at left and a liquid-cooled D-12-powered Falcon at right. Note that while the Chieftain is a wider engine, it blends well with the fuselage and is shorter and not as tall as the Curtiss D-12.

Each four-cylinder Vee section had the cylinder exhaust ports on the inside of the Vee and the intake ports on the outside. Each inline cylinder pair had its own intake runner and dual-overhead camshafts that were enclosed in a common valve cover. The camshafts were driven via a single vertical shaft from the front of the engine. There were four valves per cylinder.

Cooling air was directed through each four-cylinder section’s exhaust Vee; here it met a baffle fitted to the rear of the engine and attached to the cowling. This baffle deflected the air and forced it to flow between the inline cylinders and behind the rear cylinder. The air then flowed into the intake Vee that was blocked off at the front. The air exited the cowling via louvers over the intake Vee.

The Curtiss O-1B Falcon that was redesignated XO-18 while it served as the test-bed for the Chieftain engine. Note the exposed valve covers and the exhaust stacks protruding through the engine cowling.

The pistons were aluminum and operated in steel cylinder barrels that were screwed and shrunk into cast aluminum cylinders with integral cooling fins. From U.S. patent 1,962,246 filed by Leak in 1931, it appears that the Chieftain’s connecting rods consisted of two halves that were bolted together. Each half was made up of one master rod and two articulating rods.

The H-1640 Chieftain had a bore of 5.625 in (143 mm) and a stroke of 5.5 in (140 mm), giving a total displacement of 1,640 cu in (26.9 L). The engine’s maximum diameter was 45.25 in (1.15 m). However, a special cowling was used, cut to allow the valve covers and exhaust stacks to protrude through, reducing the diameter of the cowling to 39 in (0.99 m). The engine was 52.3 in (1.33 m) long and weighed 900 lb (408 kg). The Chieftain had a 5.2 to 1 compression ratio and was rated at 600 hp (447 kW) at 2,200 rpm but developed 615 hp (459 kW). When the engine was pressed to 2,330 rpm, it produced 653 hp (487 kW). It was equipped with a centrifugal-type supercharger that allowed the engine to maintain sea-level power up to 12,000 ft (3,658 m). All Chieftain engines built were direct drive but geared versions had been planned. In addition, some design work on a four-row, 24-cylinder version of 1,200 hp (895 kW) had been done.

Side view of the Thomas-Morse XP-13 Viper with the Curtiss Chieftain engine and revised cowl. Not the louvers for the cooling air to exit the cowling.

Because the engine had an even number of cylinders per each row, a unique firing order was developed that alternated between the front and rear rows. When the engine was viewed from the rear, the cylinders were numbered starting with the cylinder bank at the 9 o’clock position and proceeding clockwise around the engine. The rear cylinder row had odd numbers, and the front cylinder row was even so that the rear cylinder of the cylinder bank at 9 o’clock was number 1 and the front was number 2. The firing order was initially 1, 10, 5, 7, 4, 11, 8, 3, 12, 2, 9, 6 but was later changed to 1, 10, 5, 2, 9, 11, 8, 3, 12, 7, 4, 6 in an effort to smooth out the engine.

The H-1640 Chieftain was first run in 1927 and flown in a modified Curtiss O-1B Falcon, redesignated XO-18, in April 1928. The Chieftain-powered test-bed aircraft was found to out-climb and have a higher ceiling than the standard liquid-cooled Curtiss D-12-powered Falcon. In addition, the top-speed of the two aircraft was the same, which was unheard of for that time period when liquid-cooled aircraft were faster than their air-cooled counterparts. However, the engine suffered cooling issues, and the aircraft was modified back to an O-1B in July 1930.

A comparison of the original cowling on the XP-13 at left and the updated cowling at right. The front of the cowling has been extended and angled out. The block-off plates in between the openings have been angled to funnel air into the enlarged openings.

Thomas-Morse also responded to the Army’s interest in using the Curtiss H-1640. The company’s Viper fighter prototype was built to use the Chieftain engine. This aircraft was tested at Wright Field in June 1929 and given the designation XP-13. Engine overheating was encountered, and a revised cowling was tried in an effort to provide adequate cooling for the H-1640. The new cowling had enlarged openings, and the blocked off sections were angled to force more air into the openings. However, over-heating persisted. The XP-13 was tested until September 1930, when a Pratt & Whitney R-1340C engine was installed and the aircraft redesignated XP-13A. Even though this engine was not as powerful, it was lighter and did not suffer the cooling issues present with the Chieftain. The XP-13A was found to be 15 mph (24 km/h) faster than the Chieftain-powered XP-13. Curtiss had planned to produce the Viper under the designation XP-14, but the H-1640 engine was lacking support so no aircraft were built.

Another Chieftain was installed in the Navy’s second Curtiss XF8C-1 prototype in 1930. The H-1640-powered aircraft was known as the Curtiss XOC3. It too suffered from engine over-heating. The Chieftain engine remained installed in the XOC3 until the aircraft was removed from the Navy’s inventory in April 1932.

Detail view of the revised cowling on the Chieftain-powered Thomas-Morse XP-13. The image on the left illustrates the angle of the block-off plates. Note the six, instead of eight, exhaust stacks of the upper cylinders. The last two stacks are combined and exit from a single stack aft of the cowling.

In October 1928, the Army ordered three Curtiss P-6 Hawk aircraft to be powered by the H-1640 engine and designated them XP-11. However, shortly after the order was placed, the engine’s cooling trouble became known and the engine’s development ceased. The aircraft were never built with the Chieftain engine.

A total of eight H-1640 engines were made with six going to the Air Corps and two to the Navy. While the Chieftain’s design may have been problematic, the event that directly led to its lack of support and ultimate abandonment was the merger of Curtiss Aeroplane and Motor Company with Wright Aeronautical in July 1929. After the merger, the liquid-cooled engines were provided by Curtiss and the air-cooled engines from Wright. There was no longer a need for the Chieftain, an air-cooled engine of rather dubious design. However, the concept of a hexagonal engine would be revisited with the Wright H-2120, and other hexagonal engines include the SNCM 137, the Junkers Jumo 222, and the Dobrynin series of aircraft engines..

Reportedly, at least one Curtiss H-1640 Chieftain survives and is in storage at the National Air and Space Museum’s Garber Facility in Silver Hill, Maryland.

The second Curtiss XF8C-1 re-engined with the H-1640 Chieftain and redesignated XOC3.

Sources:
– Modern Aviation Engines, Volume 2 by Victor Page (1929)
– “The Curtiss ‘Chieftain’ Engine,” Flight by Erik Hildeshim (14 June 1928)
– Dyke’s Aircraft Engine Instructor by A.L. Dyke (1929)
– Aerosphere 1939 by Glenn Angle (1940)
– Curtiss Aircraft 1907-1947 by Peter Bowers (1979/1987)
– American Combat Planes of the 20th Century by Ray Wagner (2004)
– Fighters of the United States Air Force by Dorr and Donald (1990)
– General Dynamics Aircraft and their Predecessors by John Wegg (1990)

Kawasaki Ki-78 (KEN III)

2 Replies

By William Pearce

In the 1930s, Japanese aviation began to make strides toward closing the technological gap with the Western World. In 1938, the Aeronautical Research Institute of the University of Tokyo, led by Shoroku Wada, began a high-speed aircraft research program. Gathering data on high-speed flight was the primary objective, but it was felt that an attempt on the 3 km absolute world speed record was an obtainable goal.

The nearly complete and unpainted high-speed research aircraft, the Kawasaki Ki-78. Note the radiator housing on the fuselage side.

The aircraft project was known as KEN III (for Kensan III or Research III) and incorporated numerous advanced features new to Japanese aircraft. Approval was given for the aircraft’s development and a full-scale wooden mockup was finished in May 1941. Because of the outbreak of World War II, the project was taken over by the Imperial Japanese Army and designated Ki-78. A production contract for two prototypes was awarded to Kawasaki, under the direction of Isamu Imashi. Construction of the first prototype began in September 1941 at Kawasaki’s plant at Gifu Air Field.

The Ki-78 was an all-metal, low wing monoplane of conventional layout. The small streamlined fuselage was made as narrow as possible and was 26 ft 7 in (8.1 m) long. The wings possessed a laminar flow airfoil with a span of 26 ft 3 in (8 m) and an area of 118.4 sq ft (11 sq m). To reduce landing speed and improve low-speed handling, the wings incorporated drooping ailerons along with a combination of Fowler and split flaps, which was a first for a Japanese aircraft. When the Fowler flaps were deployed, the split flaps opened simultaneously to a similar extent. When the flaps were fully deployed, the ailerons automatically drooped down 10 degrees.

Factory fresh and unpainted view of the Ki-78. The aircraft is missing its outer gear doors and there is no horn-balance on the elevator.

Power for the Ki-78 was provided by an imported Daimler-Benz DB 601A inverted V-12 engine driving a three-blade metal propeller. The engine was not a Kawasaki Ha-40, a licensed copy of the DB 601. The DB 601 had a 5.91 in (150 mm) bore and 6.30 in stroke (160 mm), giving a total displacement of 2,070 cu in (33.9 L). It produced 1,175 hp (876 kW) at 2,500 rpm. The engine was modified by Kawasaki with the addition of a water-methanol injection system (another Japanese first) to boot the power output to 1,550 hp (1,156 kW) for short periods. The Ki-78 carried 66 gal (250 L) of fuel and 16 gal (60 L) of water-methanol.

The freshly-painted Ki-78 running-up its DB 601A engine. Note the hinge in the outer gear door to account for extension of the gear strut.

The freshly-painted Ki-78 running-up its DB 601A engine. Note the hinge in the outer gear door to account for extension of the gear strut.

Engine cooling was provided by two radiators: one mounted on each side of the rear fuselage. The radiators had a wide air inlet protruding slightly out from the fuselage. Airflow through each radiator was controlled by an actuated exit door. In addition, within the fuselage a small 60 hp (45 kW) turbine drove a fan to further assist cooling. The aircraft stood 10 ft 7/8 in (3.07 m) tall and weighed 4,255 lb (1,930 kg) empty.

The Ki-78 first flew on 26 December 1942 and was found to be extremely difficult to fly at low speeds and had poor stall characteristics. The aircraft was heavier than the design estimates, which increased the wing loading. Even with the special flaps and drooping ailerons, takeoff and landing speeds were both high at 127 mph (205 km/h) and 106 mph (170 km/h) respectively. In addition, elevator flutter was experienced at the relatively low speed of 395 mph (635 km/h) but was subsequently cured by fitting a horn-balance to the elevator.

Rear view of the Kawasaki Ki-78 as found by American troops after the war. Note the flat tailwheel and missing cockpit glass, flight instruments, and starboard tire. This view also displays the radiator exit door and elevator horn-balance.

High-speed flight tests were started in April 1943, and during the Ki-78’s 31st flight on 27 December, the aircraft achieved its maximum speed of 434.7 mph (699.6 km/h) at 11,572 ft (3,527 m). This was considerably less than the program’s speed goal of 528 mph (850 km/h). A study showed that extensive airframe modifications were needed to improve the Ki-78 flight performance. Consequently, the project was officially terminated after the aircraft’s 32nd flight on 11 January 1944. Only one prototype was built.

The unique Ki-78 survived the war but was crushed by American forces at Gifu Air Field in 1945.

The sole Ki-78 being crushed by American forces at Gifu Air Field, after the war, in 1945.

Sources:
– World Speed Record Aircraft by Ferdinand Kasmann (1990)
– Japanese Aircraft of the Pacific War by Rene Francillon (1970/2000)
– General View of Japanese Military Aircraft in the Pacific War by Airview (1956)
– http://forum.axishistory.com/viewtopic.php?t=32870
– http://www.letletlet-warplanes.com/2008/06/04/the-kawasaki-ki-78-ken-iii-research-plane/

Bugatti 110P Racer top

Bugatti Model 100P Racer

12 Replies

By William Pearce

Ettore Bugatti was born in Milan, Italy on 15 September 1881. In 1909, he founded his own automobile company in Molsheim, in the Alsace region. The Alsace region was controlled by the German Empire until 1919, when control returned to France. The Bugatti race cars were incredibly successful in the 1920s and 1930s, collectively wining over 2,000 races. During that time period, Bugatti enjoyed seeing the small machines that bore his name defeat the larger and more powerful machines of his major rivals: the German vehicles from Mercedes-Benz and Auto Union.

Bugatti 110P Racer top

The elegant lines of the Bugatti 100P are well displayed in this image. (Hugh Conway Jr. image)

In 1936, Bugatti began to consider the possibility of building an aircraft around two straight eight-cylinder Bugatti T50B (Type 50B) engines, very similar to the engines that powered the Bugatti Grand Prix race cars. This aircraft would be used to make attempts on several speed records, most importantly, the 3 km world landplane speed record, then held by Howard Hughes in the Hughes H-1 Racer at 352.389 mph (567.115 km/h). Bugatti turned to Louis de Monge, a Belgian engineer, to help design the aircraft, known as the Bugatti Model 100P.

Bugatti 100P general arrangement drawing based off the original drawings by Louis de Monge. Note the arrangement of the power and cooling systems.

Before construction of the Bugatti 100P began, Germany demonstrated what if felt was its aerial superiority by setting a new 3 km world landplane speed record at 379.63 mph (610.95 km/h) in a Messerschmitt Bf 109 (V13) on 11 November 1937. Bugatti disliked Nazi-Germany and was very interested in beating their record. Bugatti and de Monge continued to develop the 100P for an attempt to capture the 3 km record from Germany.

The Bugatti 100P was one of the most beautiful aircraft ever built. With the exception of engine exhaust ports, the 25 ft 5 in (7.75 m) fuselage was completely smooth. The aircraft employed wood monocouque “sandwich” construction in which layers of balsa wood were glued and carved to achieve the desired aerodynamic shape. Hardwood rails and supports were set into the balsa wood to take concentrated loads at stress points, like engine mounts and the canopy. The airframe was then covered with tulipwood strips, which were then sanded and filled. Finally, the aircraft was covered with linen and doped. The Bugatti 100P stood 7 ft 4 in (2.23 m) tall and weighed 3,086 lb (1,400 kg).

The 100P had a 27 ft (8.235 m), one-piece wing that was slightly forward-swept. The wing had a single box spar that ran through the fuselage. The wing was constructed in the same fashion as the fuselage and housed the fully retractable and enclosed main gear. The wing featured a multi-purpose, self-adjusting flap system (U.S. patent 2,279,615). Both the upper and lower flap surfaces automatically moved up or down to suit the speed of the aircraft and the power setting (manifold pressure) of the engines. At high manifold pressure and very low airspeed, the flaps set themselves to a takeoff position. At low airspeed and low power, the flaps dropped into landing position, and the landing gear was automatically lowered. In a dive, the flaps pivoted apart to form air brakes.

Image of the nearly complete Bugatti 100P still under construction in Paris. The cooling-air inlet in the butterfly tail can be easily seen.

The Bugatti tail surfaces consisted of two butterfly units and a ventral fin at 120-degree angles (French patent 852,599). They were constructed with the same wood “sandwich” method used on the fuselage and wing. The tip of the ventral fin incorporated a retractable tail skid.  For cooling, air was scooped into ducts in the leading edges of the butterfly tail and ventral fin. The air was turned 180 degrees, flowed into a plenum chamber in the aft fuselage, and passed through a two section radiator (one section for each engine) located behind the rear engine. The now-heated air again turned 180 degrees and exited out the fuselage sides into a low pressure area behind the trailing edge of the wings. The high pressure at the intake and low pressure at the outlet created natural air circulation that required no fans or blowers (U.S. patent 2,268,183).

The two Bugatti T50B straight eight-cylinder engines were specially made for the 100P aircraft. The engine crankcases were made of magnesium to reduce weight, and each engine used a lightweight Roots-type supercharger feeding two downdraft carburetors. The T50B had a bore of 3.31 in (84 mm) and a stroke of 4.21 in (107 mm), giving a total displacement of 289 cu in (4.74 L). Twin-overhead camshafts actuated the two intake and two exhaust valves for each cylinder. The standard T50B race car engine produced 480 hp (358 kW) at 5,000 rpm. An output of 450 hp (336 kW) at 4,500 rpm is usually given for the 100P’s engines; however, de Monge stated the engines planned for the 100P were to produce 550 hp (410 kW) each. The engines were situated in tandem, behind the pilot. The front engine was canted to the right and drove a drive shaft that passed by the pilot’s right side. The rear engine was canted to the left and drove a drive shaft that passed by the pilot’s left side. The two shafts joined into a common reduction gearbox just beyond the pilot’s feet. The gearbox allowed each engine to drive a metal, two-blade, ground-adjustable Ratier propeller. Together, the two propeller sets made a coaxial contra-rotating unit. From the gearbox, the rear propeller shaft (driven by the front engine) was hollow, and the front shaft (driven by the rear engine) rotated inside it (U.S. patent 2,244,763).

Image of the two T50B engines in the Bugatti 100P while at the Ermeronville estate. Note the radiator at left , how the engines are canted within the fuselage, and how the exhaust ports on the front engine protrude through the fuselage.

Once the new design was finalized in 1938, construction of the 100P was begun at a high quality furniture factory in Paris. While construction proceeded, it was obvious that war would break out soon. France did not have any fighters that could match the performance of their German counterparts. The French Air Ministry felt the 100P could be developed into a light pursuit or reconnaissance fighter and awarded a contract to Bugatti in 1939. This fighter was to be equipped with at least one gun mounted in each wing, an oxygen system, and self-sealing fuel tanks. Most aspects of the fighter are unknown, but it is possible that it was larger than the 100P and incorporated 525 hp (391 kW) T50B engines installed side-by-side in the fuselage driving six-blade coaxial contra-rotating propellers with a 37-mm cannon firing through the propeller hub. Because of France’s surrender, the aircraft never progressed beyond the initial design phase.

The Bugatti 100P, finally in all its glory after being completely restored by the Experimental Aircraft Association. Note the fairing for the rear engine ‘s exhaust ports above the wing. (Hugh Conway Jr. image)

Bugatti’s contract included a bonus of 1 million francs if the 100P racer captured the world speed record which the Germans had raised to 463.919 mph (746.606 km/h) with a Heinkel He 100 (V8) on 30 March 1939 and raised again to 469.221 mph (755.138 km/h) with a Messerschmitt Me 209 (V1) on 26 April 1939. Bugatti and de Monge felt the 100P was capable of around 500 mph (800 km/h). In addition, a smaller version of the racer, known as the 110P, was planned; it featured a 5 ft (1.525 m) reduced wingspan of 22 ft (6.7 m). The 110P was to have the same engines as the 100P, but the top speed was estimated at 550 mph (885 km/h). However, other sources indicate these figures were very optimistic, and the expected performance was more around 400 mph (640 km/h) for the 100P and 475 mph (768 km/h) for the 110P.

The 100P was nearly complete when Germany invaded France. As the Germans closed in on Paris in June 1940, the Bugatti 100P and miscellaneous parts, presumably for the 110P, were removed from the furniture factory and loaded on a truck. The 100P was taken out into the country and hidden in a barn on Bugatti’s Ermeronville Castle estate 30 mi (50 km) northeast of Paris.

Bugatti 100P on display at the EAA AirVenture Museum in Oshkosh, Wisconsin. The cooling air exit slots on the left side of the aircraft can be seen on the wing trailing edge fillet. Also note the tail skid on the ventral fin.

Ettore Bugatti died on 21 August 1947 with the 100P still stashed away in Ermeronville. The aircraft was purchased by M. Serge Pozzoli in 1960 but remained in Ermeronville until 1970 when it was sold to Ray Jones, an expert Bugatti automobile restorer from the United States. Both Pozzoli and Jones offered the 100P to French museums but were turned down. Jones acquired the 100P with the intent to complete the aircraft; however, that goal could not be completed due to missing parts. Jones had the two Bugatti T50B engines removed from the airframe before everything was shipped to the United States. Dr. Peter Williamson purchased the airframe and moved it to Vintage Auto Restorations in Ridgefield, Connecticut in February 1971 to begin a lengthy restoration. Les and Don Lefferts worked on the project from 1975 to 1979. Louis de Monge was now living in the United States and assisted with some aspects of the restoration work before he passed away in 1977. In 1979, the unfinished 100P was donated to the Air Force Museum Foundation with the hope of having the restoration completed and the aircraft loaned to a museum for display. However, the aircraft sat until 1996 when it was donated to the Experimental Aircraft Association (EAA) in Oshkosh, Wisconsin and finally underwent a full restoration. The restored, but engineless, Bugatti 100P is currently on display at the EAA AirVenture Museum.

The original engines out of the Model 100P were reportedly not the final version of the engines intended for the actual speed record run. Both engines still exist and are installed in Bugatti automobiles. The front engine is installed in Ray Jones’ 1937 Type 59/50B R Grand Prix racer, and the rear engine is installed in Charles Dean’s 1935 Type 59/50B Grand Prix racer. Since January 2009, Scotty Wilson has led an international team, including Louis de Monge’s grand-nephew, Ladislas de Monge, to build a flying replica of the Bugatti 100P in Tulsa, Oklahoma. Piloted by Wilson, the Bugatti 100P replica flew for the first time on 19 August 2015. Tragically, Scotty Wilson was killed when the replica crashed during a test flight on 6 August 2016.

Bugatti 100P on display at the EAA AirVenture Museum in Oshkosh, Wisconsin. Simply one of the most beautiful aircraft ever built.

Sources:
– The Bugatti 100P Record Plane by Jaap Horst (2013)
– World Speed Record Aircraft by Ferdinand Kasmann (1990)
– Airplane Racing by Don Berliner (2009)
– The Classic Twin-Cam Engine by Griffith Borgeson (1979/2002)
– http://www.bugattiaircraft.com/kalempa.htm by Alex Kalempa
– http://www.airventuremuseum.org/collection/aircraft/2Bugatti Model 100 Racer.asp
– http://www.airventuremuseum.org/collection/aircraft/2Bugatti Model 100 Racer Facts.asp
– http://morlock68.pagesperso-orange.fr/bugatti.htm
– http://bugatti100p.com/
– http://en.wikipedia.org/wiki/Bugatti
– http://kfor.com/2016/08/06/historic-replica-airplane-the-bugatti-100p-crashes-near-burns-flat-pilot-and-designer-scotty-wilson-dies/

FIAT AS.6 Aircraft Engine (for the MC.72)

6 Replies

By William Pearce

For the 1929 Schneider Trophy Contest, Italy fielded a number of different aircraft and engine combinations. The end result was that none of their entries were developed enough be victorious, and Britain won the contest for the second time in a row. If the British were to win the competition in 1931, the Schneider Contest would be over, and Britain would retain permanent possession of the Schneider Trophy.

Side view of the FIAT AS.6 illustrating the engine’s length. In the middle of the engine at bottom, two water pumps can clearly be seen with coolant lines feeding the individual cylinders. Right behind the propeller hubs, one of the front engine section’s magnetos can be seen. The small pipes leading from the middle of the engine toward the rear engine section and from right behind the front engine section’s cylinder bank and toward the front engine are for the air starter.

To prevent a British victory in 1931, Italy focused on developing one aircraft and one powerplant for its Schneider efforts. Macchi Aeronautica was chosen to develop the airframe, and with the design talents of Mario Castoldi, the Macchi-Castoldi 72 (MC.72) was born. FIAT was tasked with developing an engine to power the MC.72 and defeat the British. Time was short for FIAT because the MC.72 would be designed around the engine.

As the FIAT engine team, led by Tranquillo Zerbi, began to develop a new powerplant, they quickly realized that there was not enough time to start from scratch; the engine that was to power the MC.72 would have to start from an existing engine. FIAT’s best powerplant at the time was the 1,000 hp (746 kW) AS.5 (Aviazione Spinto) V-12 engine. This engine was used in one of Italy’s 1929 Schneider racers, the FIAT C.29. The Italian team knew the engine would need at least 2,300 hp (1,715 kW) to win the 1931 Schneider Contest and began developing a supercharger, increasing the engine’s compression, and incorporating other enhancements to attempt to achieve the desired power. But even early on, Zerbi knew the AS.5 engine could not develop the power needed to defeat the British.

While working on the enhanced AS.5, a proposal was made to mount two AS.5 engines back-to-back, creating a V-24 engine. FIAT moved forward with the concept and called it the AS.6, but it was not as simple as bolting two AS.5 engines together. The AS.5 engine sections were not coupled together. They shared a common magnesium crankcase and an induction manifold, and there was only one throttle linkage. Everything else (the ignition, coolant, and oil systems) was independent for each engine section.

Rear view of the FIAT AS.6 showing the two four-barrel carburetors feeding the supercharger. Directly below the supercharger are fuel pumps and the two magnetos for the rear engine section.

A 0.60 gear reduction for the propellers would be driven from the back of each AS.5 engine section (middle of the V-24 power plant). A drive shaft would be taken from the gear reduction of each engine. These drive shafts would travel through the Vee of the front engine and to the nose of the aircraft.  The rear engine drove a 69.96 in (1.77 m) shaft inside the front engine’s 52.52 in (1.334 m) shaft. Via the drive shaft, each engine drove one pair of propellers that together made a coaxial contra-rotating unit; the front engine drove the rear propeller, and the rear engine drove the front propeller. Coaxial contra-rotating propellers allowed for a blade short enough to avoid sea spray and also cancelled out the torque of the engine.

The rear engine section powered a supercharger that supplied 6.5 psi (0.45 bar) of air to both engine sections through a manifold approximately 88.58 in (2.25 m) long. The supercharger took 250 hp (186 kW) to run and spun at 17,000 rpm. The propeller pitch was ground adjustable. The front and rear propellers were adjusted to different pitches to compensate for the supercharger’s drain on the second engine section (front propeller) and efficiency differences between the first and second set of blades. The metal propellers were 8.5 ft (2.59 m) in diameter.

A detailed view inside the FIAT AS.6. The propeller gear reduction and drive shafts can clearly be seen. Note the individual cylinders on the far side of the engine and how the two crankcase sections are joined in the middle.

The FIAT AS.6 was a liquid-cooled, 60-degree, V-24 engine. It used individual steel cylinders, each with a 5.4 in (138 mm) bore and 5.5 in (140 mm) stroke, giving a total displacement of 3,067 cu in (50.256 L). The engine had a maximum compression ratio of 7 to 1. Four valves per cylinder were actuated by dual-overhead camshafts. The AS.6 was 132.48 in (3.365 m) long, 27.64 in (0.702 m) wide, 38.43 in (0.976 m) tall, and weighed 2,050 lb (930 kg). The engine was started by compressed air fed from a distribution pump located on the gear reduction housing. The rear engine section was started first.

Each inboard camshaft was driven from a gear parallel to and smaller than the propeller reduction gear. The outboard camshaft was geared to the inboard camshaft. Oil and water pumps were gear driven from the crankshaft. Each bank of each engine section had its own water pump. Ignition for each engine section was provided by two magnetos. The rear engine section’s magnetos were crankshaft driven and located below the supercharger. The front engine section’s magnetos were located on top of the engine, near the propellers, and driven from the outer (front engine’s) propeller shaft. Each cylinder had two spark plugs installed perpendicular to its axis: one located below the intake valves and the other below the exhaust valves.

Sectional view of the FIAT AS.6 illustrating the propeller drive shafts. Note the gear drive for the camshafts at top, the oil and water pumps at bottom, the front engine section’s magnetos at front, and the supercharger and rear engine section’s magnetos at rear.

During development, the AS.6 engine suffered many technical difficulties. Issues were encountered with spark plugs, ignition, coolant flow, fuel metering, induction, exhaust valves, connecting rods, and supercharger drive, to name a few. Much time was spent to resolve the issues. By April 1931, the engine completed a one hour run, producing 2,300 hp (1,715 kW).

The AS.6 engine was installed in the first of five MC.72 aircraft (MM 177 to MM 181), and flight trials began in the summer of 1931. Almost immediately, a new and very dangerous problem was discovered: while in flight, the engine would backfire at high power and high speed. The cause of this issue was a bit of a mystery because the engine ran perfectly on the ground but not during flight. Even with the engine’s difficulties, the aircraft had attained a speed of 375 mph (604 km/h). To demonstrate the backfire phenomenon, Capt. Giovanni Monti flew the MC.72 (MM 178) for FIAT and Macchi engineers on 2 August 1931. Sadly, a backfire ignited the volatile air/fuel mixture in the long induction manifold and caused it to explode. The MC.72 crashed into Lake Garda. Monti was killed in the crash.

FIAT AS.6 engine being test run in a MC.72.

With the Schneider Contest one month away and the cause of the backfiring still unknown, the decision was made to withdrawal the AS.6-powered MC.72 from the race. The British would make an uncontested flight for the Schneider Trophy and retain it permanently. But the Italians had decided to make an attempt on the absolute world speed record on 13 September 1931, the same day as the Schneider race. On 10 September, Lt. Stanislao Bellini was making a practice run to exceed 394 mph (634 km/h), the fastest the MC.72 had flown, when the aircraft (MM 180) flew straight into rising terrain. Debris found some distance from the impact site indicated that there had been an in-flight fire or explosion. Subsequently, the MC.72 was withdrawn from flight status.

The vision of what the AS.6 and MC.72 could have been continued to stir in the minds of various officials, and a new record attempt was planned. Believing the backfire issue was fuel related, the Italians wanted the help of Rod Banks: the Britain who developed the special fuel used for Rolls-Royce’s R Schneider engine. Banks was closely associated with the British Schneider effort but was not employed by Rolls-Royce or Supermarine. In 1932, the British sent Banks to see what could be done to improve the AS.6 engine.

Rear view of a preserved FIAT AS.6 engine at the Centro Storico Fiat in Turin, Italy. (Gianni image)

Banks arrived to find the AS.6 engine producing 2,400 hp (1,790 kW), but not reliably. A special sprint version of the engine had produced 2,850 hp (2,125 kW), but only for one minute. One of the issues Banks discovered was that the Italians had not fully accounted for the ram effect of having air forced into the induction by the forward speed of the aircraft. The AS.6 ran well on the ground, but the 400+ mph (640+ km/h) air being rammed into the intake caused a lean condition. This lean condition led to a backfire that ignited the air/fuel mixture in the long induction.

Banks knew how Rolls-Royce had dealt with this issue. Rolls-Royce had used a Kestrel engine to run a blower that supplied ram air for the R engine being tested. Banks had the Italians use a similar set-up that provided ram air at 435 mph (700 km/h) into the AS.6’s intake. The AS.6 engine was tuned under these conditions and no longer backfired. The sprint engine was able to produce 2,850 hp (2,125 kW) for an hour.

Warrant Officer Francesco Agello and the FIAT AS.6-powered MC.72 after setting the 3 km absolute world speed record at 440.682 mph (709.209 km/h) on October 23, 1934.

Late in 1932, the MC.72 took to the air once more; the AS.6 engine now produced a reliable 2,400 hp (1,790 kW). On 10 April 1933, Warrant Officer Francesco Agello set a 3 km absolute world speed record at 423.824 mph (682.078 km/h) in MM 177. On 8 October 1933, LtCol. Guglielmo Cassinelli captured the 100 km speed record at 391.072 mph (629.370 km/h). On 21 October, Capt. Pietro Scapinelli won the Blériot Cup in MM 179 for flying in excess of 600 km/h for over half an hour. His actual speed over the 30 minute run was 384.799 mph (619.274 km/h).

A year later, an AS.6 sprint engine was installed in the MC.72 (MM 181). This engine produced 3,100 hp (2,312 kW) at 3,300 rpm; 11.5 psi (0.79 bar) of boost was provided by the supercharger spinning at 19,000 rpm. On 23 October 1934, Agello was again at the controls and upped the 3 km record to 440.682 mph (709.209 km/h)—Agello was the fastest man on earth. This speed has never been surpassed by a piston-powered seaplane.

The record-setting MC.72 (MM 181) and an AS.6 engine are on display in the Museo Storico dell’Aeronautica Militare in Vigna di Valle, Italy. Another AS.6 engine is on display at the Centro Storico Fiat (Fiat Historic Center) in Turin, Italy.

The FIAT AS.6 displayed alongside the MC.72 (MM 181) at the Museo Storico dell’Aeronautica Militare in Vigna di Valle, Italy.

Sources:
– The Schneider Trophy Story by Edward Eves (2001)
– Schneider Trophy Seaplanes and Flying Boats by Ralph Pegram (2012)
– Schneider Trophy Aircraft 1913-1931 by Derek James (1981)
– Schneider Trophy Racers by Robert Hirsch (1993)
– Jane’s All the World’s Aircraft 1935 by Grey and Bridgman (1935)
– Italian High-Speed Airplane Engines NACA Technical Memorandum No. 944 by C. F. Bona (1935/1940) 17.7mb pdf
– Technical Aspects of the Schneider Trophy and the World Speed Record for Seaplanes by Ermanno Bazzocchi (1971)
– Idrocorsa Macchi by Apostolo and Cattaneo (2007)
– I Kept No Diary by F.R. Banks (1978)

Bellanca 28-92 Trimotor

2 Replies

By William Pearce

The Bellanca 28-92 (construction no. 903) was developed by Giuseppe Bellanca in 1937 for Capt. Alexandru Papana. Papana was a Romanian Air Force pilot who planned to use the Bellanca on a long-distance good-will flight from New York to Bucharest. He named the aircraft Alba Iulia 1918 to commemorate the assembly of ethnic Romanian delegates who unified what is modern-day Romania at Alba Iulia, Transylvania in 1918. The aircraft carried the Romanian registration YR-AHA.

Alex Papana poses with the Bellanca 28-92. The Romanian registration can be seen on the wings but the name, “Alba Iulia 1918,” has yet to be applied. Note the propellers do not have spinners.

The Bellanca 28-92 was a low-wing, single-seat, trimotor design. The fuselage was of tubular steel construction and covered by aluminum back to the cockpit. Aft of the cockpit, the fuselage was covered with fabric. The wings and tail were plywood-covered, and the control surfaces were covered by fabric. The main undercarriage partially retracted into the rear of the wing engine nacelles, but the tailwheel did not retract.

Installed in each wing of the aircraft was a 250 hp (186 kW) Menasco C6S4 engine. The C6S4 Super Buccaneer was a direct drive, air-cooled, inverted, straight-six aircraft engine. The C6S4 was supercharged and displaced 544 cu in (8.9 L). Each C6S4 engine drove a 6 ft 6 in (1.98 m) diameter, two-blade, adjustable-pitch propeller.

The complete 28-92 with spinners and “Alba Iulia 1918” painted on the side. “YR” is painted on the tail, and the registration “YR-AHA” is repeated on the upper fuselage behind the cockpit..

A 420 hp (313 kW) Ranger SGV-770 engine was in the nose of the 28-92. The SGV-770 was an air-cooled, inverted, V-12 engine. The engine was supercharged, displaced 773 cu in (12.7 L), and had gear reduction for the 8 ft 3 in (2.51 m) diameter, two-blade, adjustable-pitch propeller.

All of the trimotor’s engines were hand cranked to start. The 28-92 had a fuel capacity of around 715 gallons (2,707 L). The aircraft had a span of 46 ft 4 in (14.1 m), a length of 28 ft 4 in (8.6 m), and weighed 4,700 lb (2,132 kg) empty. The 28-92 had a top speed of 285 mph (459 km/h) and a 3,000 mile (4,828 km) range at 250 mph (402 km/h) or a 4,160 mile (6,695 km) range at 200 mph (322 km/h). Landing speed was 75 mph (121 km/h).

Front view of the 28-92 trimotor illustrating the limited visibility from the cockpit while the aircraft was on the ground.

Papana was inexperienced with superchargers and inadvertently overboosted the engines during his first test flight in the trimotor. The incident led to a disagreement with Bellanca, and Papana cancelled his order for the aircraft. Since the 28-92 was complete and neither Papana nor the Romanian government paid for the aircraft, it remained at the Bellanca factory.

In 1938, Bellanca registered the aircraft in the United States as NX2433 and entered it in the Bendix Trophy cross-country race. Frank Cordova was the pilot for the race, and the trimotor flew as race number 99. Unfortunately, because of engine trouble, the aircraft did not finish the cross-country race. The Ranger engine in the nose quit, but Cordova continued to fly on the two Menasco engines for another 1,000 miles (1,609 km), landing in Bloomington, Illinois. A new rule for the 1938 races stated that no aircraft entered in the Bendix race could compete in the Thompson Trophy race, so the trimotor was returned to the Bellanca factory.

Bellanca 28-92 trimotor with Art Bussy at the controls for the 1939 Bendix race. The aircraft looked the same for the 1938 race except the race number was 99.

The 28-92 was again entered for the 1939 Bendix Trophy race, this time piloted by Art Bussy. Competing as race number 39, the aircraft finished second in the Los Angeles to Cleveland race with an average of 244.486 mph (393.462 km/h). Continuing on to New York, Bussy and the trimotor again finished second, averaging 231.951 mph (373.290 km/h) for the total distance from Los Angeles to New York.

Because of the start of World War II, all air races and record flights were put on hold. The Bellanca 28-92 trimotor was of little use during this time. The aircraft was eventually purchased by the Ecuadorian Air Force and served in South America from 1941 to 1945. Reportedly, the 28-92 was abandoned at a small airfield in Ecuador; a sad end for a unique aircraft.

Rear 3/4 view of the Bellanca 28-92 showing the aircraft’s clean lines.

*Sources disagree on what number the aircraft used for which year. Images reportedly from 1939 show number 39 on the fuselage, but it is possible that they are in error and race number 99 could have been used in 1939 and race number 39 used in 1938.

Sources:
– Aircraft of Air Racing’s Golden Age by Robert and Ross Hirsh (2005)
– The Air Racer by Charles Mendenhall (1994)
– Aerosphere 1939 by Glenn Angle (1940)
– Bellanca Specials 1925 – 1940 by Theo Wesselink (2015)
– Jane’s all the World’s Aircraft 1938 by Grey and Bridgman (1938)