By G. A. Limbach, EAA 6911
Brussells 1, Belgium
The purpose of this article is to attempt to set the record straight on a very famous little homebuilt -- the "Knight Twister." From the time I was just a starry-eyed kid I always thought the "Knight Twister" was one of the most beautiful little airplanes ever. I still think so, and when the opportunity arose to buy one, I jumped at it. While I do not yet belong to the group which has built its own plane, please accept my comments as an enthusiastic member of the club.
A word about my background might help in evaluating this article. Uncle Sam taught me to fly as a Nav-Cad and I spent almost 15 years as an active Marine reservist, five on active duty. Almost all of my duties were with fighters. I spent six months with the Service Test Group at NAS Patuxent. I have flown many different airplanes, including about a dozen different fighter types. I had been out of flying for some time when the local flying club got me back in the air in a Stinson -- and then I had a chance to buy a "Twister," N13N.
A chat with Paul Poberezny brought home the fact that these little planes are very light on the controls -- very much subject to over-controlling. This was worthwhile information., and. being forewarned, I was careful of it. Bill Kahn of Milwaukee, Wis., from whom I bought the plane, was very helpful with his comments and suggestions. But, in the long run, if you want to fly this type of bird, you have to strap it on and go it on your own. And here's the story.
Before I agreed to buy my "Twister," I taxied it at relatively slow speeds for maybe five minutes. The tailwheel is mechanically rigged to the rudder without any springs and I noticed then that a slight rudder movement was sufficient for a pretty good turn on the ground. The plane is quite short and swings very easy. When I got serious about buying it I set out for more taxi runs.
Bill Kahn, who was selling it, was understandably getting nervous. My "Twister" had a 125 hp Lycoming. This engine has quite a lot of torque for such a little plane. Also, a previous owner had cracked it up an high speed taxi runs.
My first runs on the concrete strips were relatively slow; but, again I was struck with the sensitive rudder control. As I speeded up my runs, I purposely had her wander a little to get the feel of straightening her out. Frankly, I was beginning to chicken out. A chat with Bill resulted in my running pretty fast on one of the grass strips. It, got pretty bouncy and a little hairy out there, too, and I didn't get any happier. Bill was also concerned because of a left crosswind on the main runway adding to the torque.
After about 45 minutes of taxiing it the second time out, I thought I was ready for a real high speed run. I wanted to get the tail in the air -- and get the feel of approximate landing speed. This run gave me the thrill of my lifetime. When I cut the throttle, she turned so hard on the runway the tires screamed like a street racing hot-rod. The wings took turns going up and down, and the runway kept trying to, off both sides of my plane at once. I quit on that one, cut the engine and crawled out convinced that a man had to be shot full of luck to make many successful landings in a row with that crazy airplane. But I got out and looked at it, and it sure was pretty. I had given the man a check, so I agreed to his ferrying it to my field and I'd learn to fly it there.
| This is how the "Twister" looked in its more youthful days. It was built in November, 1952 by the team of Lowery & Roakes, and was financed by H. M. Dingley of Sky Harbor Flying Service in Auburn, Maine. Originally, it was powered by a 100 hp Lycoming, and then changed to a 140 hp Lycoming O-240-D2A. At the time this picture was taken, it was owned by E. Haeh of Great Falls, Mont., who had damaged it in high speed taxi runs. (Leo J. Kohn Photo) |
After many sleepless post-mortems, I knew I had it whipped. High speed taxi runs had to be the ultimate in difficulty with that plane. It had a lot of torque -- a heck of a lot for its size. To counteract this torque takes a lot of right rudder. While holding it straight under power, tail up, the plane was in a relatively hard, right-hand steering position, and the tailwheel is linked solidly to the rudder. Chop the throttle, the tailwheel drops, still cocked for a right turn, and "Hold her, Newt, she's headed for the barn!" In any real landing everything must be pointed straight ahead; if you don't land in a skid, just hold it and ride it out. Other people could fly them and I knew I could, too.
I went back to Milwaukee -- taxied her a little more -- just enough to be familiar with the sensitiveness and turned the bird loose.
With full power on take-off, there is that high torque, but the rudder is very ample to hold it. I find that lifting the tail high with positive forward stick keeps it on the ground longer and prevents it from trying to corkscrew in the air. Once airborne, my plane climbed away beautifully.
As mentioned, these planes are very sensitive to control forces. It rolls very quickly -- but even more so -- it is very, very sensitive longitudinally. If you put the nose down, she'll pick up speed very quickly, and on the first few flights it is difficult to keep it from bobbing at higher speeds. It does what the F-86 and FJ-2 pilots call the "Jay Cees!" After a few hours, however, you learn to guide it -- not manhandle it, and my "Knight Twister" was as honest a flying machine as I've ever flown.
Statistics on my plane first, then a discussion of its flight characteristics. The air speeds are approximated from checking with other airplanes in the air and calibrating my air speed indicator. I think they are about right.
My bird stalls at about 75 mph. In this attitude, the tailwheel is well below the main gear. Its best climb speed according to Vernon Payne's figures, and also by my time checks, is about 110 mph. At 2200 rpm, it will cruise at around 125 to 130 mph. At 2350 rpm it will cruise at about 140 mph. Top speed is about 165 mph at 2600 rpm. The metal prop is 66 inches in diameter -- 66 inch pitch. I've timed it from pushing the throttle forward on takeoff to 1500 feet straight ahead in one minute even, and to 3500 feet in 2 minutes, 20 seconds.
Stalls amaze me... the airplane doesn't want to stop flying. It stalls clean and just seems to drop. It gives ample warning through the stick shudder. I have stalled it in all sorts of odd angles and it just drops. I had naturally expected a real snap into a spin -- but it honestly doesn't. It does spin, but, since it is slightly tail heavy I avoided intentional spins. The few unintentional ones I've done have been fast -- but quick to pop out with normal corrective action. All in all, it's very honest in the air.
I've found the approach is best (I use 180 degrees, always turning fighter approach) at about 110 mph, slowing to 95 going over the fence. Touch-down is about 80. I have dropped it in from about 3 feet; I've bounced it on its wheels; I've landed almost every way you can, and in all types of fields from a 1300 foot taxi strip to 5000 feet of concrete. In over 70 hours of flying I made more than 125 landings. However, I can't say I found the right slot for consistently smooth landings. Nevertheless, it didn't seem to matter. The sensitive tailwheel controls gave me immediate and positive corrective action which worked very well. My plane has Cessna type gear, and it is very springy. I believe if I was building one, I'd use a more solid gear for better ground handling characteristics on concrete.
| Gus looks almost too big for the airplane as he climbs aboard. A 125 hp Lycoming is now mounted in the plane. (Leo J. Kohn Photo) |
A word of caution on landing approaches... the plane handles and flies well at much slower speeds, but its rate of descent without power in the lower speeds is pretty high and it won't flare out. I found this out the hard way, too.
For aerobatics I like to keep the speed up, with aileron rolls or barrel rolls at 140 mph or better. Slow rolls and hesitation rolls are done at 150 mph or better. Hesitation rolls are difficult to do well because it is so sensitive longitudinally, and let's face it -- it takes practice to be real sensitive while hanging on a belt. Loops are OK at 160; I feel better at 175 for Immelmans and Cuban Eights. For some reason it doesn't snap roll very well. It doesn't seem to want to snap, and since I didn't care for the maneuver, I didn't work very hard on it. Remember, this data is for my plane, and not for all "Twisters."
I have checked on one "Twister" in the area very carefully and have flown with another. I wouldn't give them house room with the smaller engines. I've flown wing on one, and with his 75-85 Continental running at 2500 rpm I was slowed to 2000 rpm and about 115 mph. In some of the turns I felt uncomfortable on his wing.
One hundred mph is no speed to be wrapped up in a "Twister" at low altitude. This is what should be avoided by "Twister" pilots just checking out. It will turn easy and roll to a steep bank. With its sensitive stick control, a novice can pull it back too tight, too quick -- kill whatever speed he has, and spin in. Remember, a tight turn increases the angle of attack, which increases the drag and kills speed.
All in all I was very fortunate. My "Twister" was everything I had hoped it would be. A real attraction at any fly-in, a ball far a quick half hour on my back, a kick to know that this little bird was mine. While I know two men who have very successfully flown them with only lightplane experience, I don't recommend a "Twister" for this group. However, if you have a good flight background in hot airplanes, put 125 horses in a "Twister" and I assure you, you will have the time of your life.
(ED. NOTE: Gus Limbach has been assigned overseas in the course of employment, and his present address is:
Clark Equipment International C/A
Browns Trailer Div., Auto Div.
Centre International Rogier
Brussells 1, BELGIUM)
Webmaster's Note: For more information about this aircraft and its specifications, please see the article High Powered Knight Twister in the January 1955 edition of Experimenter (page 12).