FLIGHT TESTS, STOLP STARLET

February 14 & 21, 1970
(Post-flight comments by the late Art Scholl)

This is a pilot report on the Stolp Starlet, N2300. I will try to express my personal opinion of what I felt when I walked up and looked at this airplane and then flew it.

As I watched construction of this aircraft, I have been very interested in its flight characteristics. It is probably one of the prettiest of all the little home-built airplanes I have ever seen, and I think its name is very appropriate … Starlet. Actually, it depicts a very slim, good-looking girl, but these lines just strike me as being very exceptional. Then you wonder, will these lines sacrifice some of its flying abilities.

Lou Stolp conducted the preliminary flights. He gave me a brief rundown on the aircraft, that they have had it up to 120mph, but no faster. The first thing in a test flight would be to find out what its dive characteristics are. This is very important in flight-testing any aircraft, because if you are trying some kind of acrobatic maneuver, and you have no idea what you could allow the aircraft to go to, you must know what your basic red line is on the aircraft. Then, in executing and starting maneuvers, if the maneuver does not turn out like you had planned, at least you know where your limits are as far as the red line is concerned.

Getting in the airplane, you find that it is a very comfortable position to be seated in. In fact, after flying you feel like you don’t want to get back out of it. After getting strapped in with the shoulder harnesses and belt, I found I could not reach down to the left to reach the flap handle, so the flights were done without the use of flaps. (Flaps on prototype only – currently deactivated.)

Taxiing is fairly easy, with very good visibility. Being a high-wing parasol, you can see left and right and straight down fairly easily. Ground handling seems fairly good after run up. On taxiing out to the runway, you find that it is a little sensitive. The stick movement is very small and yet, on the initial run for takeoff, you find that the pressures are very light. Although the stick is very efficient, you don’t have the feeling of over-controlling because the airplane is fairly stable. Directional control, though, is a little touchy on the initial roll.

Around 80mph, I pulled the aircraft off and climbed. Timing was, at this point 80mph, 1,200 feet per minute, sustaining the 80mph climb to about 2,000 feet. Climbing to 5,000 feet above the field, the dive tests were started. The aircraft was rolled over and dove to 130mph, the stick accelerated and then a pullout. The next one was 140; then 150. A surprising thing, as I reached speeds of 150 and 160mph, I noticed that in accelerating the stick, the aircraft tended to remain in any position that it was placed. In other words, the CP travel did not seem to be very excessive in either direction. Trim seemed just about right for me. This aircraft has a fixed stabilizer and I had no particular problems with the trim whatsoever.

Then, the dive testing continued, and reaching 180 and 190mph, again this sensation of putting the nose down and having the nose stay at the pitch angle that it was set at in accelerating the stick. I had no indication of any type of flutter whatsoever. And finally, the final dive speed was to be 220mph. To achieve this, I rolled over in a split “S” and started on down with about half throttle and immediately the air speed did build up to about 220mph, again hands off, accelerating the stick and no indication of any kind of flutter or bad characteristics. On pulling out this time, however, the air speed did go as high as 230mph. At this speed, I felt that there would be no need for anyone to dive or fly the airplane past 230, so the dive tests were stopped at 230mph.

Next came the spin and stall tests. I will check again on the flight today, but I think the stall speeds appeared to be indicating around 60mph. Let’s correct that to about 55 to 60mph without the use of flaps. On the first flight test, the spin test was started. I started out with a half turn spin to the right and half turn to the left. The spin to the left seemed about twice as fast as the one to the right. We finally ended up today’s testing with a full spin to the right, and a half turn to the left—still being a little cautious about the spin.

At this point, I wanted to check the center of pressure and CG travel before any further spin tests were conducted. Making the dive tests, I was doing a semi-wingover, hammerhead type turn, but not a real competitive hammerhead. The reason for this is, not knowing the spin characteristics, you would not like to have the airplane fall into a tail slide and then flip into a spin if the airplane had any bad characteristics in the spin. So, no real hammerheads were done at this time.

After being very satisfied with the dive tests, I headed back to the field and made a 160mph flyby, and then pulled up and came around to land. In landing, I was able to reach forward and put in one notch of flaps. The approach had to be done with a little power. I noticed that it did have a little faster sink rate than you would normally think of on landing. The flare was done with a little power and this felt very good, and it seemed to have real good characteristics for a 3-point landing. I noticed in trying wheel landings one would have to get used to the airplane to make good wheel landings.

On the next test flight a few days later, we were interested in seeing what the aircraft would do in spins … this was our main concern at this time. Again, climbing to 5,000 feet, the spin was started to the right. We worked up to 3 turns in each direction. I noted that the spin to the left is very fast, but it does stabilize without going flat and the spin recovery is remarkably fast. The spin to the right is somewhat slower. I allowed the airplane to go into a 5-turn spin to the right and found that after two turns, it stabilizes at a constant rate and the recovery, again, is very responsive.

At this time, knowing that the spin characteristics were excellent, I wondered how the aircraft would snap. Surprisingly, it reminded me of the Pitts in snapping characteristics because it was very fast, much greater than the Super or standard Chipmunk. The aircraft, again, would snap much faster to the left than to the right. After doing 1 and 1-1/2 and 2 turn snaps, I then tried loops, a loop with a snap on top, Cuban 8s and maneuvers such as this. This aircraft is not fitted with an inverted fuel system. So, no inverted flight was tried except for the Cuban 8, just momentarily holding inverted, and surprisingly the engine never sputtered or gave any problem with the negative G loadings that were momentarily imposed on it. I noticed that in the loop with the snap on top, the aircraft does slow down enough so that when you try to snap, you have to watch it because it does get quite mushy on top. It seems to want to snap very nicely at high speeds, which is typical of the Pitts in its snapping characteristics.

The next thing to find out was what kind of an angle the airplane will maintain inverted, even though the engine will quit. We were interested to see what kind of inverted flying characteristics it will have. Also, the hammerhead turns never were really tried. Going from a Pitts or a Chipmunk to a high-wing parasol is just a little different feeling, because you have very good visibility ahead and down, and in the hammerheads you have to watch the wing in getting the airplane perfectly vertical. Now, we want to know just how it pivots about its centerline to start on downhill in the hammerhead.

This is what surprised me because after this third flight, I find that I roll inverted and there is no control pressure feel. In fact, it is so light on pressure, you’re going to have to do what (Bob) Herendeen did with his Pitts. And that is, put some springs on it so that you know where neutral is, because you can shove forward on the stick and just push right on over. You have very little stick pressure whatsoever in any direction. There’s just no feeling of any stick pressure; it’s like it has hydraulic boosts in the controls. So, you want to build in a little stick pressure. So, you’ll probably want to put some bungee springs in there so that when you push the stick, you’ll feel a little pressure against the stick.

It is unusual to get an airplane design that flies like this, especially the airfoil. I find that there is very little difference between the feel of upright and inverted as far as stick pressures are concerned. And outside snapping … we only had on one flimsy belt, so I didn’t want to push too much outside. But I did dive at about a 30 degree angle down at 180 and pushed forward on the stick with very little stick pressure, but instantly to about 3 negative Gs to push up. And I felt that without power, I could have pushed it right over into an outside loop from the inverted position. But until we get a stronger belt in there, I don’t dare do that.

Then I wanted to try the outside snap, so from the inverted position I just touched the stick and rudder and snapped back to upright, with immediate recovery. And then on one of the outside snaps, I flew inverted and did an outside snap back to the inverted position again, very nicely. It did it real good. I’m very surprised at the snapping ability of the airplane. The rudder is most effective. Now, for instance, in a hammering turn, if you’re going to do a hammerhead and then a half roll straight down, the nose will pin right on a point. But if you push aileron in, the rate of roll is very slow. But pushing the nose on the point and hitting the rudder and aileron is a fantastic rate of roll, just right around and still staying on the point. So, the rudder is the most effective point of the airplane.

Now, when you are doing aerobatics, and I have to relate back to my Chipmunk, the Super Chipmunk was taken to Ft. Worth, Texas and I couldn’t get it to snap. So, Harold Krier flew it and he tried and tried, and he could get it to mush around into a little better snap than I go out of it. And when he landed, he said, “Art, there’s nothing wrong with the airplane; you’re going to have to learn how to fly it.” And yet we did modify certain things, but not significantly, and suddenly we got that airplane snapping very well, just like the Yak and Zlin. And yet, it is just techniques and learning to fly, and learning to fly a particular airplane. So here I have to say that, in all fairness, you have to learn to fly each individual airplane. Now, with this airplane, it was a pleasure to do snaps to the left and to the right, spins to the left and right, outside snap—everything came easy, which normally doesn’t in a new airplane that you don’t know. The only thing that was not a good competitive maneuver was the hammerhead turn.

The airplane goes to the vertical position very quickly and easily. It holds, it stalls, it pivots instantly right around its axis, but when it starts heading down it tucks under. It tucks under about 30 degrees, and with full backpressure on the stick, I can’t keep it from tucking under. And if this is the only complaint that I can find, this is pretty good because with a little technique of flying, maybe we can solve this problem. And if we can’t solve it by learning how to fly it, then there may be some aerodynamic things we can do to the airplane to try to get it not to tuck under … if you were looking for a competitive-type airplane. But all of the basic characteristics of the airplane, with the 108hp Lycoming in it, it seems that with that little power we have in it, you do have a fairly competitive airplane from the things that I can see from flying it.

Now, the landing. Let me explain this is only my third landing in it today. I came in at 90mph, throttled off, and a very slight flare at 90 and a real nice flare in floating and touchdown at 60, 3-point, and it seemed very straightforward on the landing. There is something I can’t quite pin down on the flaring of the airplane … the stick. I am probably getting to the point now that I understand why it felt funny on the first landing. I think it feels funny because everything is so well in balance, you don’t have the feel you should have, and with bungee cords on the stick, you might have the feel. And again, I have to go right back and say it flies very similar to the Pitts as far as the response that it has. And I know that Bob had to put bungees on his Pitts because of the controls being so easy that he didn’t have the feel. I think this is what bothered me on the first landing, not feeling any backpressure when you came back on the stick, and you might begin to wonder if the controls are working. Now, if we can get that double belt in there, we can try some of those outside maneuvers.

Without an inverted system, you are limited as to what you can check, but I was surprised at the way the airplane did respond. It seems it will fly very well inverted. The inverted characteristics felt the same as upright … I didn’t seem to find any difference. I could point the nose up and take my hands off and it would stay there. Or I could point it down and it would stay, the same as upright. I noted that when I did the dive testing and I put the nose down, I could take my hands off the controls and it would tend to stay in the position you put it in. Very stable as to if an amateur pilot that would be flying would make any kind of mistake inverted, immediately, the airplane wants to roll upright. Say you get too slow and you stall inverted—the airplane just flips upright. I noticed this when I came from a half of a loop to inverted flight and stopped it and then flew inverted. A couple of times I came up and purposely pushed it there and stalled it to see how it would feel in a stall, and as soon as it stalls it flips to the upright position. So, the airplane does have some real good characteristics as far as the amateur is concerned. You always look at what the guy is going to do in getting into trouble. Now one thing is, you could get into trouble if you didn’t have altitude and you were learning aerobatics without altitude, which you shouldn’t be doing anyhow. But, if that did happen close to the ground, you could very easily snap the airplane and head on downhill very easily.

Definitely, the airplane could very easily—if you were slow in turning from base to final and kicked rudder—it could snap upside down instantly. This is a characteristic of good aerobatic airplanes. You have to respect them and know that the airplane, if you kick rudder hard, it’s going to snap on you—I mean, it’s going to snap so fast. If you’ve got backpressure, it could snap and it wouldn’t give much of an indication. The thing to do to correct that—if a person is going to fly it as a regular airplane without doing aerobatics—the thing he would have to watch … you could put stops on the rudder so you wouldn’t have much rudder travel. That would stop it. You want elevator travel for flaring out for landing. It’s the backpressure stall—it’s very straightforward on stalling—you’re not worried about backpressure, you can stall it by pulling the stick back. It’s that rudder, a very efficient rudder on there, you just touch the rudder and it goes. And this is the only caution—the rudder control. The elevator will stall it straight ahead; it won’t fall left or right or roll on its back, but if you push the rudder in and stall it … then it will.

We flew today fully grossed. This airplane indicated 1,000 fpm climb all the way up and we were fully grossed with full wing tanks of fuel—a wing tank and fuselage tank were full. So, all of this aerobatic flying was done with full fuel on board. It has an electrical system and radio, and it’s probably loaded the most that you would get a Starlet loaded. Now, if you increased this horsepower and lightened up some of the weight on it, it would be a very, very good air show and competitive airplane. I guess Lou didn’t mean it to be that way, though. It should be real good with a 150, aerobatic-wise. The airplane feels very solid structurally. I don’t seem to worry at all about the tail or wings, as everything seems to be very solid. And in doing the aerobatics, you don’t have the feeling of anything flexing or giving, like you do in a lot of airplanes … a very solid feeling. Incidentally, one of the pleasures of flying this airplane is taxiing. It is a real thrill to taxi the airplane … it honestly is. You can see everywhere you are going because of the visibility. It has excellent visibility on the ground. You can taxi in between airplanes; turn around, and without taking up any room head back the other way. It’s fun just taxiing it.