By William Pearce
Near the end of World War I, D. Napier & Son built one of the most outstanding aircraft engines of all time: the 12-cylinder Lion. Lion production continued through the 1920s and 1930s, and other Napier aircraft engines did not achieve a level of success anywhere near that of the Lion. In the 1930s, Major Frank Halford was the head aircraft engine designer at Napier and was working on H-type engines. Compared to contemporary aircraft engines, Halford’s new engines used a smaller cylinder bore and stroke and ran at a higher rpm. In the late 1930s, Halford’s latest engine was the Sabre—a sleeve valve engine with 24 cylinders of 5.0 in (127 mm) bore and 4.75 in (121 mm) stroke. The Sabre displaced 2,238 (36.7 L) and was capable of over 2,000 hp (1,491 kW) and speeds up to 4,000 rpm.
Napier wanted a way to demonstrate their new aircraft engine to the world. In its earlier days, the Lion had powered aircraft used to set world speed records. Since 1937, the Germans had held the landplane 3 km (1.86 mi) world speed record at 379.38 mph (610.55 km/h), and since 1934, the Italians had held the absolute 3 km (1.86 mi) world speed record at 440.682 mph (709.209 km/h). Napier felt a specially designed aircraft powered by a Sabre engine would be capable of setting a new speed record at over 480 mph (772 km/h), beating both the Germans and Italians. Not only would this achievement be great marketing, it would also bring the record back to Britain and embarrass Hitler’s Germany and Mussolini’s Italy.
Under lead designer Arthur E. Hagg, Napier laid out its racer design in mid-1938. Hagg previously designed the de Havilland DH.91 Albatross transport, and the two aircraft share some family resemblance. The racer’s sole purpose was to break the 3 km (1.86 mi) world speed record, and it was not intended as a testbed for the Sabre engine. The British Air Ministry was unwilling to financially support the project, but Lord Nuffield (William Richard Morris) stepped forward to independently fund the construction of two aircraft. In addition, a number of vendors donated parts and services or offered them at cost. Since Napier did not have the resources to construct the racer, the Heston Aircraft Company was selected to build the aircraft in late 1938. The Heston team was led by George Cornwall. The association between Napier and Heston gave the aircraft its popular name: the Napier-Heston Racer. The aircraft is also known as the Nuffield-Napier-Heston Racer, the Heston J.5 High-Speed Aircraft, and the Heston Type 5 Racer.
To expedite construction, the Napier-Heston Racer was built almost entirely of wood. The wing spars were made from compregnated wood of multiple laminations bonded with resin under high pressure. The fuselage frame and stringers and wing ribs were made of spruce. The wings and fuselage were covered with birch ply sheets. Split flaps were incorporated into the wings. The control surfaces had aluminum alloy frames and were covered with fabric. A variable-ratio control system was designed for the elevator. This system kept the elevator movements small when the control stick was near the neutral position. As the control stick was moved farther from neutral, the relative elevator movement became greater. This system was employed so that very precise elevator movements could be achieved at high speeds.
The Napier-Heston Racer was fitted with one of the first six Sabre I prototype engines, but its boost was increased. The standard Sabre I engine produced 2,000 hp at 3,700 rpm, but the racer’s engine produced 2,450 hp (1,827 kW) at 3,800 rpm. The racer had a 10 ft 9 in (3.28 m) diameter, metal, three-blade, de Havilland constant-speed propeller. Wing root intakes led to the engine’s supercharger. A radiator was housed in a duct under the aircraft. The radiator’s upper and lower surfaces were sloped back and formed a deep V in the duct. After air passed through the radiator, it was expelled under the horizontal stabilizer on both sides of the tail. A channel above the radiator skimmed off the turbulent boundary layer, allowing it to bypass the radiator. The wide-track (14.8 ft / 4.5 m) main gear retracted fully into the wings, and a small tail skid was incorporated into the fixed fin of the tail. After many layers of aircraft dope were applied, the fit and finish of the racer was near perfection.
Between the engine and fully enclosed cockpit was a 73 gallon (276 L) fuel tank. At full throttle, the aircraft’s endurance was only 18 minutes. The racer had a wingspan of 32 ft (9.75 m), a length of 24 ft 7 in (7.50 m), and a height of 11 ft 10 in (3.61 m). Its fully loaded weight was 7,200 lb (3,267 kg). All tolerances were kept to a minimum, and the racer was highly polished to remove any imperfections. The aluminum engine cowling had four bulges to allow clearance for the Sabre’s cylinder banks. The cowling sealed so tightly that small air vents were installed on the bulges to ensure that no combustible vapors built up in the engine compartment.
The first flight of a Sabre engine occurred on 31 May 1939. The engine was installed in a Fairey Battle flown by Chris Staniland. The Sabre-powered Battle had accumulated a number of hours before the special engine in the Napier-Heston Racer was first run on 6 December 1939. The racer was painted silver, with the registration of G-AFOK painted in dark blue. Taxi tests began on 12 March 1940 at Heston Airport. The engine and taxi test did not reveal any issues with control or engine cooling.
The Napier-Heston Racer’s first flight was delayed by weather but finally occurred on 12 June 1940. Squadron Leader G. L. G. Richmond was at the controls and flew the aircraft off from the 3,900 ft (1,189 m) grass field at Heston Airport. Reportedly, Richmond chose to make this flight without the canopy in place. Shortly after liftoff, the Sabre engine rapidly overheated, and Richmond tried to quickly bring the plane in for a landing. Sources disagree on exactly what happened next.
Some sources state that Richmond was preoccupied with the emergency and was also being scalded by the overheated cooling system. They claim that he may have experienced some difficulty mastering control of the variable-ratio elevator, as he had almost touched down after a steep approach when the aircraft rose sharply back into the air and stalled. Other sources point out that the racer did not exhibit any cooling issues during the numerous ground engine runs and that Richmond was scalded when the coolant pipes burst as a result of the hard landing after the stall. They contend that the aircraft’s elevator became ineffective as a result of low speed and that it was possibly in the wings’ turbulent airflow during the steep pitch up before the stall. While some sources state the Sabre engine seized, others report the ignition was on and the engine was running but that Richmond did not advance the throttle because of its overheated state.
Richmond’s flight in the Napier-Heston Racer was only about six minutes, and he never retracted the gear. After liftoff, he immediately brought the aircraft around for landing. Richmond’s actions indicate he felt something was wrong very early on. While a burst cooling pipe would explain the cooling issues and Richmond’s scalding, and control issues with the elevator would explain the odd altitude deviations in the aircraft’s final moments, the exact issues and sequence of events may never be known.
The end result was that the Napier-Heston Racer stalled about 30 ft (9 m) above the grass runway and hit the ground hard. The impact broke the landing gear, the left wing, and the rear fuselage just behind the cockpit. Fortunately, Richmond was able to walk away from the wreck. With the war against Germany underway, no attempt was made to repair the Napier-Heston Racer. The racer’s Sabre engine was not badly damaged. It was rebuilt and installed in a production Hawker Typhoon that was used during the war. Although the second racer, registered as G-AFOL, was around 60% complete, it was never finished. The Napier-Heston Racer project had cost Lord Nuffield £50,000 to £100,000.
Between the time the Napier-Heston Racer was conceived and its first flight, Germany had increased the absolute world speed record to 469.221 mph (755.138 km/h). However, the Chief Technician and Aerodynamicist at Heston Aircraft, R. A. Clare, had estimated that the Napier-Heston Racer could achieve a maximum of 508 mph (818 km/h) over the 3 km (1.86 mi) course. While the true capabilities of the racer will never be known, attempts have been made to create a flying replica. Due to the high cost of such a project and the extreme rarity of Sabre engines, for now, a Napier-Heston Racer replica remains just a dream.
– “The Napier-Heston Racer” by Bill Gunston Aeroplane Monthly (June 1976)
– “Napier-Heston Racer postscript” Aeroplane Monthly (August 1976)
– “A Co-operative Challenger” Flight (15 April 1943)
– “The Heston Napier Monoplane” by H. J. Cooper The Aero Modeller (August 1943)
– By Precision Into Power by Alan Vessey (2007)