P.A. feels a great interest in the performance of this vest-pocket pursuit ship because it is the outcome of a conference with Mr. Payne in our office and the original drawings were first published by us. Our faith in Mr. Payne and his design has been justified.
(From Popular Aviation, Probably 1934, Page 101)
By Vernon W. Payne
Webmaster Note: Please contact us if you know exactly when this article appeared… we believe it was sometime in 1934.
If anyone tells you that there is a keen looking little airplane at the airport, and you should see it, first ask them if it is a Knight Twister. If it is, you will not be disappointed.
It is not only keen looking but it is really small. Standing under the wing of a Stinson Monoplane it looks like a toy, but don’t let that fool you, for it means business when it is ready for flight.
At last we have exploded two time-worn theories, which are: (1) That a small biplane could never be built as stable or as efficient as a monoplane. (2) That small planes are tricky.
This little vest-pocket pursuit type of biplane has a top wing span of 15 feet, a lower wing span of 13 feet and an overall length of 11-1/2 feet, so you see that one important point in our favor of biplanes is the small housing space required.
The old criticism that small planes are tricky to fly, dates back to the World War when not so much was known about the proper location of the wings in relation to the center of gravity of the airplane. Many of these old-timers forget that aviation has advanced considerably since the war. We have many better wing sections that have been developed since the war.
We selected the N.A.C.A.-M6 wing section which is fairly fast but inherently stable. This means that when the ship dives, the center of pressure on the wings, moves forward and tends to bring the ship out of the dive. When the ship is stalled, the center of pressure moves back, tending to lift the trailing edge of the wing up, thereby bringing the ship out of the stall. This all helps to make a small ship a smooth flyer.
Many small ships were built with the RAF15 wing section, which has a great center of pressure movement which is hard for the average amateur to balance properly, therefore the result is a very unstable and tricky flying ship. Oftentimes these ships would pancake when the pilot tried to bring it in slow and found that the lift suddenly turned up missing. The RAF15 landed fast and lost its lift quickly near the stalled position.
Here’s Vernon W. Payne standing beside his latest product — the celebrated “Knight-Twister.” The efficiency of this little ship has been proved.
The M-6 wing section, which we use, can be stalled at a much greater angle of attack than the RAF15. This high angle of attack, when coming in for a three-point landing, helps to slow down the air pressure on the elevators and will force the tail skid into the ground, which acts like a dragging brake.
Well, fellows you should have seen this little ship perform. It is a honey in the air as well as on the ground. Let me tell you, if you want a picture see the ship immediately after making contact with the ground.
The biplane wings of this little ship, with the high amount of stagger, act as a large wet blanket. This is much the same as an air brake, deflecting the passing air sharply towards the ground. When the wings are close to the ground, the air is compressed, and this is what shortens the roll of the ship after landing.
Another thing that can be used to shorten the roll after landing, is the large tail surface. The Knight Twister has large elevators and if the stick is pulled back after making the landing, and when it is flying, you had better get a telescope, for it doesn’t hang around. It gets right out of sight.
Towing the “Knight-Twister” to the field. It is hardly larger than the small car but is infinitely faster.
We took a snap-shot of the ship after it took off, but there was only a fly-speck on the picture. The only pictures of value that are available were taken on the ground. We will get someone with a long distance movie camera to get the next action pictures and these will appear in an early issue of P. A.
The first trial flight was made with a propeller borrowed from a Klemm low-wing ship. This propeller, manufactured by Gardner Propeller Works, Chicago, was designed to fly a Klemm at 65 m.p.h. But it did better than we expected, for this flat angled propeller flew the Knight Twister at 100 m.p.h. This means that the light biplane has so little resistance that the propeller tried to run away with itself so that the engine turned up much too fast.
The Gardner brothers have successfully designed propellers for this ship for high speed and also for service. One propeller for racing at 150 m.p.h. The other is the service propeller which gives a better climb rate, or smaller take-off run, and a top speed of 135 m.p.h. with the Salmson A.D.9 engine.
Many of you have heard a Salmson engine when it was flying a Klemn low-wing and noticed that sort of whispering exhaust. It did not convince you of much power. Well, fellows, wait till you hear it in the nose of the Knight Twister for it has a powerful hum like a real pursuit ship.
To see this little ship pass you, bank and turn, dive, pull up and perform many maneuvers, makes you wish that you could get in and get hold of those controls for yourself.
The first landing was made very close to me, and being the first time a pilot ever flew this ship, he naturally flew it in hot — about 80 m.p.h. When he was close to the ground he tried for a three-point and, believe it or not, when the ship contacted with the ground, it appeared to stop right instantly. Even with the fast landing, I’ll bet it did not run 175 feet. The pilot, “Curley” Cushman, made several flights and found that the ship will make a perfect 3-point at 40 m.p.h. and not roll over 125 feet. You can therefore get into a very small field.
Both pilots, “Curley” Cushman and Fred Buchardt, claim this little ship to be the most stable little plane ever built. It was flown on a very windy day and it flew “hands-off.” The Knight Twister does not bob up and down in a breeze. It is not treacherous to fly, like so many of the little ships that were built for the last few races. The extra large tail and aileron control surfaces will bring it out of any spin or stunt.
The first flight tests were made with no engine N.A.C.A. cowl ring or wheel pants, so you can imagine what the great increase in speed will be with these fairings in place.
We intend to design a two-place having the same general proportions as the Knight Twister, but a little larger. The span will be about 25 feet and the overall length about 17 feet. The landing speed will be 30 to 35 m.p.h. and the top speed about 100 m.p.h., using 50 to 65 h.p.
We have changed the tail a little, making the rudder larger for easier taxying control. We also made the stabilizer and elevators larger to enable the pilot to get the tail off quicker, when taking off with a speed propeller that does not throw back enough blast for good control at take-off speeds. A climbing propeller will get the tail up very well.
In the original drawings of the Knight Twister we showed a stabilizer and elevators made of steel tubing, but the tail we actually used was made of spruce and plywood. The ailerons were also made of spruce and plywood instead of steel tubing.
The wings are of the cantilever type, spruce and plywood construction. We use one flying-wire to brace the wings, but the wings are strong enough to stand a crash landing while doing a complete cart-wheel without breaking a spar — believe it or not. In spite of their strength, the dead weight is only 1.1 lbs. per sq. ft. area.
The fuselage is of steel tubing, faired to a perfect elliptical cross-section, with spruce strips and plywood rings.
The landing gear, made like a fork, is of No. 1025 Aircraft steel tubing. It could be made lighter if made of alloy steel and heat treated, but some mechanic would have an opportunity to make a mistake and replace alloy steel with common low carbon. The result would be a weak landing gear, ready for a crash landing.
In engineering the Knight Twister, we kept safety uppermost in mind and you will notice that where the strain is greatest, we have an ample size of tubing. This little cloud buster will take it.
In a ship of this size, where the landing-gear is proportionately much larger than with a big ship, the wheel pants and other fairings will make a tremendous difference in the top speed and general performance. As it stands now, the landing-gear kicks up a tremendous disturbance in the air and correspondingly cuts down the speed with a given horsepower.
There are a few other little “bugs” to clean out, and then we believe that we will have the fastest little craft of its size and type that has yet been designed.
Chart of Aluminum and Aluminum alloys, circa 1934.