Published on May 4, 2013
The key challenges of air racing are ones of weight, profile, horsepower and aerodynamic streamlining. In 1927, at the height of the international competition in the Schneider Trophy seaplace races, the British team tried a radical experiment. The idea was to mount the newly designed nine-cylinder Bristol Mercury radial engine, as air-cooled engines had a better horsepower/weight ratio than water-cooled, inline. Through the use of carefully designed aerodynamic fairings, the British hoped that the larger frontal profile of the radial could be streamlined into the fuselage, resulting in a lighter, more powerful and therefore faster racer.
So was born the revolutionary seaplane racing machine known as the Short Crusader which, on this date in aviation history, May 4, 1927, made its first flight. Despite the promise of the design, the Short Crusader would never race a single contest. Why and how that happened, however, is one of the tragedies of 1920s air racing history.
The Aircraft and Engine
Two British designers, Lieut.-Col. W. A. Bristow and W.G. Carter (the latter a former designer with the H. G. Hawker Engineering Co.), were independently tasked to develop the racing plane design by the Bristol Company, whose new radial engine was an extraordinary advancement over its past engine designs. Though smaller and lighter than any previous radial, the new Bristol Mercury could theoretically produce as much as 960 hp, though the company derated it for flight safety reasons to 808 hp. In response to the request, the two designers produced a stunningly streamlined concept. Early on, however, they realized that an established manufacturing facility was needed to actually produce the plane. Thus, in 1926, Short Brothers (Rochester & Bedford) Ltd. was approached with the project. Having garnered British Government funding for a single racing prototype based on the design and promise of the new engine, Short Brothers considered the manufacturing deal a welcome contract.
By early 1927, the seaplane racer had taken form as a low wing monoplane with streamlined wires for support. It had a medium airfoil wing and a fairly low wingspan for its size. Manufactured of spruce frames and stringers overlaid with a thin veneer of mahogany, the Short Crusader was extremely light and strong. The twin floats were designed especially for the Crusader, serving both as a fuel tank and for the traditional purposes of take off and landing from the water. The Short Crusader’s light weight and high horsepower compared well with the other two planes of the racing team, the Supermarine S.5 and the Gloster IV, both equipped with the Napier Lion VIIB inline engine, which boasted up to 900 hp, though much heavier due to the water cooling system.
The entire airplane and engine combined weighed less than earlier radial engines alone! Empty, the Short Crusader came in at 1,938 pounds and, with fuel and loaded at race weight, it totaled to just 2,712 pounds, only slightly more than the Supermarine S.5 and Gloster IVB racers weighed empty! For comparison, the S.5 weighed in at 2,680 pounds empty, giving it a fully loaded race weight o 3,242 pounds. The Gloster IV weighed 2,613 pounds empty and at race weight with a full fuel load came in at 3,305 pounds. As a result, both racers required more wing and, conversely, had to produce a lot more lift (and thus higher induced drag) to fly. On paper, the Short Crusader promised to be the race leader. The only remaining challenge was the engine’s large size, which produced excessive profile drag.
Thus, the chief aeronautical problem had to do with the challenge of developing fairings that would both cover and streamline the cylinder heads, which protruded out of the full circumference of the nose of the plane. This problem was made even more complex because the design had to ensure also that there was sufficient airflow over the cylinder heads for the air-cooled engine to avoid overheating at full power. An innovative “helmet” design was developed that wrapped each cylinder head in a unique streamlining cap. The term “helmets” was selected because each one appeared every bit like a Medieval jousting helmet with a pointed brow and eye slots for cylinder air cooling. The top cylinder’s helmet extended into a long spine that reached the cockpit and then continued to gracefully taper into the vertical stabilizer and rudder. Everything about the design was streamlined to the utmost. The fuselage even tapered to a point at the end of the tail. The Short Crusader’s design was revolutionary in all respects.
First Flights and Speed Trials
The first flight of the Short Crusader was completed by the Australian test pilot, Bert Hinkler. At the time, he was a known name in aviation circles, but not yet famous as he would be just a year later. Then, he would fly solo from England to Australia in record time, thereby catapulting himself into the public eye as a leading aviation pioneer and air racing pilot. In the Short Crusader, he took off and flew the plane for a short time, landing to report that it handled smoothly and easily. It was balanced, fast and gentle on the controls. The wing design, elliptical with a smaller chord at the root, was unique and performed well.
Critically, the plane had a tendency to “hunt” in yaw. This was a problem that Hinkler had created himself when, having seen the original design, thought that the vertical stabilizer was too small and therefore demanded it be increased before he would fly it. As it happened, the aeronautical engineers were right about their design. Hinkler’s modification was subsequently replaced with the originally designed tail and the problem was solved.
The plane was then turned over to the RAF, which assigned it to its dedicated Schneider Trophy racing team, the RAF High Speed Flight. Throughout the summer, the Short Crusader was put through its paces in familiarization flights and time trials at Felixstowe Air Station. All of the racing pilots reported that the plane was stable and easy to fly. They found it maneuverable in the turns and fast on the straights — however, time trials showed it to be consistently slower than both the Supermarine S.5 and, surprisingly, slower even than the biplane Gloster IV!
The Schneider Cup Race
The British arrived at the Lido, off the coast of Venice, in grand style with four Royal Navy destroyers and HMS Hermes. The planes were unloaded and prepared for the competition. Due to the unexpected slower speed of the Short Crusader in its time trials, the RAF racing team had elected to bring the plane primarily for practice and familiarization flights. Only in the event that the other racers failed or crashed would the Short Crusader make a showing. Thus, the plane was one of the first to be prepared for flight. It was uncrated and assembled hurriedly so that the RAF High Speed Flight could get started practicing the course.
The course would be off the beach at the Lido, starting quite near the seaplane station. The racers were to take off and fly a counter-clockwise set of seven laps of 50 kilometers in length each. The first leg of the triangular course was 11.4 km long with an obtuse angled turn into a 13.86 km leg that then reversed sharply for the final side of the irregularly shaped triangle, at 24.74 km in length. Thus, the total length of the course, on completion of the seven laps, was 350 km.
The first practice flight to be flown was by the High Speed Flight’s Flying Officer Harry M. Schofield. As Schofield lifted off, he kept the nose down and built up the speed to about 150 mph, keeping it just a couple of feet over the tops of the low waves. As he pulled back to start a curving climb out to the right, however, the Short Crusader banked instead to the left. Schofield reacted by pulling the stick farther over to the right, the correct reaction and one that came as second nature to a pilot of his experience. What he didn’t know was that the aileron control cables had been incorrectly assembled. They were crossed. Instead of correcting the roll to the left, his right aileron input rolled the plane further to the left. In the instant afterward, uncomprehendingly, he sharply rammed the stick over more to try to bring the wings level. This only sharpened the roll to the left, of course. Almost instantly, the plane rolled inverted and struck the water.
It was all over in less than a second. On hitting the water, the fuselage split in twain right at the cockpit, throwing Schofield completely out. The plane shattered apart as it came to a stop with a huge splash. Totally destroyed, the engine and heavier components sank while the wooden parts floated. A motorboat in the area sped to the scene and pulled Schofield out of the water. Incredibly, he was bruised and half-drowned but otherwise unharmed.
The accident ended the Short Crusader’s short life as an experimental seaplane racer. Its design had showed great promise, even if the plane hadn’t been able to compete in the Schneider Trophy races of 1927. The RAF team would select the Gloster IVB with its geared engine and narrower span biplane wings, as well as two of the Supermarine S.5s to compete in the 1927 race. As it would happen, the British prevailed that year, marking the beginning of the ascendency of the latest all-metal monoplane racer designed by R. J. Mitchell.
The victory with the Supermarine S.5 would bring the Schneider Trophy races to Calshot in England where the next generation of the Supermarine plane, the S.6, would take the prize as well. Finally, the Supermarine S.6B would win a third time in 1931, bringing the Schneider Trophy to Great Britain for all time to come and ending the seaplane races forever. The S.6B would not be the final iteration of the design series, however, as many of the lessons learned were applied into a later aircraft — the Supermarine Spitfire, Britain’s most famous plane that, along with the Hawker Hurricane, would bring victory in the Battle of Britain in 1940. Interestingly, the elliptical wing of the Short Crusader was carried forward, in a modified form, into the final design of the Spitfire.
Today’s Aviation Trivia Question
Other than the elliptical wing, were the other aerodynamic lessons learned from the Short Crusader applied to subsequent British fighter planes? If so, which?