Napier-Heston Racer

Constructed exclusively for an attempt at setting the World’s Landplane and Absolute Speed Record, the Nuffield-Napier-Heston J5 was originally conceived by A.E. Hagg of D Napier and Son in 1936. Financial arrangements for the patriotic venture were offered and provided for by Lord Nuffield (the industrialist, Robert Morris, of MG fame). The order for its general-arrangement and preliminary design work was begun in the spring of 1938 by the Heston Aircraft CO, LTD, Middlesex.

The Heston project design department, headed by Chief designer George Cornwall, was asked to design a super-fast aircraft intended to recapture the world’s air speed record, then held by the Germans. The racer’s design parameters were to be purposely designed around and powered by a top secret, specially built, blown version of a 24-cylinder, 2,450 HP liquid cooled Napier Sabre engine.

Napier Sabre engine

To ensure rapid construction and achieve a superfine finish, the Napier-Heston Racer was built almost entirely of wood, which in part was attributable to its beautiful lines. The racers weighed in at 7,200 lbs, of which approximately 40% was the dry weight of the specially prepared 2,450 HP Napier Sabre engine. The racer’s potential top speed had been reasonably placed at close to 500 mph If it had not been for the advent of World War II, the Napier Heston racer may have proven itself the fastest piston-powered aircraft of all time.

A rarebird indeed... regarded by many as the most beautiful design achievement in the history of piston-powered flight. Special attention was given by the designers to address the reduction of skin friction, cooling drag and the elimination of parasitic drag caused by a “leaky” engine cowling. The cockpit area was also given attention, besides having a low-pressure outside airflow system and being sealed, a one piece low profile persplex canopy was utilized for its aerodynamic qualities. Within the remarkable high-gloss finish of the aircraft, nearly 20 coats of hand-rubbed Titanine lacquer, could be found many ingenious aerodynamic features that bear mentioning. From the absorption of turbulent air at the mouth of the cooling duct, to the overall finish achieved to reduce parasitic drag through skin friction and other important airflow entries, especially the leading edge of the wings, no scratches more than “half a thousand of an inch” deep were allowed.

One of the innovative aerodynamic design features incorporated by Heston’s design group was the use of a multi-ducted belly scoop. For the first time in the design of aircraft, an attempt was made to control and clear turbulence from beneath the fuselage. The ducted scoop bled off coolant air and yet provided a separate uninterrupted path for boundary layer air to efflux on either side of the rudder, at the rudder post. This new design preceded a similarly designed type belly scoop used on the P-51 Mustangs for many years.

The wing of approximately straight taper form, had airfoil sections of the bi-convex type, symmetrical throughout the greater part of the span, with the maximum ordinate located unusually far back at 40% of the wing chord to delay the onset of shock-stall which was expected at higher speeds. A slight camber was given the tips to avoid tip stall characteristics. The thickness-chord ratio was 16.2% at the fuselage, 12.8% at the landing gear fulcrum, and 9% at the tips. The wing as a whole was aerodynamically “untwisted” and had a span of 32.04 feet, an area of 167.6 sq. ft., with a wing loading of 43.5 lbs. per sq. ft. High, but not considered bad for this type of aircraft. All control surfaces were mass-balanced and provided with mass-balanced trim tabs, the ailerons were of Frise type, none of the control levers or mass balances projected in the slipstream. As was mentioned before, all critical points, such as the leading edge of the wing, were polished until no surface scratches more than a depth of 0.0005 in. remained.

In December 1938, construction work commenced on two Napier-Heston prototype airframes side by side, in case there were problems with one or the other. The design followed the Air Registration Board’s formula for civil aircraft and were allotted the registration numbers, G-AFOK and G-AFOL respectfully, work progressed on each very rapidly. By the time war broke out on September 3, 1939, one aircraft, G-AFOK, was nearing completion while the second airframe, G-AFOL, was approximately 60% completed. The start of war effectively put an end to work on the second airframe, G-AFOL. However, work on G-AFOK was ordered to be completed and the engine was run-up, the first for a Napier Sabre engine in an aircraft, on December 6th, 1939 approximately one year after construction began.

Ground engine testing of the “Racer” prototype began on the 9th of February 1940, with Heston’s chief test pilot, Squadron Leader G.L.G. Richmond beginning successful vibration and taxiing tests on the 12 of March, 1940 and continuing them for several months. The “Racer” passed all phases of the ground taxiing tests and prolonged engine run-up, the newly designed aircraft seemed to have no faults.

It was decided to wait for perfect weather. Finally on June 12 1940, Richmond decided to test fly the Heston racer. He taxied out without the canopy. As the aircraft raced across Heston’s grass strip at full power, control and response was more than adequate. Then the racer hit a bad irregularity in the grassy surface very hard, causing the Heston to rotate prematurely into a very nose-high attitude. Thirty seconds or so after hitting the bump and full throttle and becoming airborne, the engine coolant temps went critical. Richmond found himself in an unfamiliar flight attitude in a new aircraft that employed a uniquely designed and sensitive flight control system, the landing gear down and no canopy. His first landing in the Heston was going to be hot.

Six minutes after opening the throttle, he had made a wide circuit at about 20 mph, throttled back, and set up for the landing approach. The ignition was not switched off and the DeHaviland-Hamilton constant-speed prop was not feathered. Witnesses say that he leveled out at about 30 ft, stalled, and “banged it” on, quite possibly because he was being scalded from below - there is speculation that an engine coolant pipe or fitting had fractured during the hard bump incident at takeoff. Whether the aircraft stalled or not, it arrived at the field at an excessive rate of descent, hit the ground hard, drove the landing gear through the wings, broke the tail, and ensued other major airframe damage before coming to rest. The pilot was scalded but not badly hurt, the Heston was a complete write-off.

The question since that fateful day has been: Would the purposely built Napier-Heston Racer have been capable of recapturing the world speed record? The racer never had a chance to do so because of the circumstances that occurred. It’s design is still regarded by many to have represented the pinnacle in powered flight.