Category Archives: Between the Wars

Fokker F.XX Zilvermeeuw Transport

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.

– “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)

Bugatti 110P Racer top

Bugatti Model 100P Racer

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.

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) by Alex Kalempa Model 100 Racer.asp Model 100 Racer Facts.asp

Bellanca 28-92 Trimotor

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.

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)