Restoring the A-10D Mitchell Wing
SN# 275
By
Episode V
“Learning to
Fly the Wing With ‘Terrible’ Terry”
This Episode is
dedicated to the memory of Terry Thornton
Before I brought the A-10 back from Florida, I made a solemn promise to the previous owner that I would make the pilgrimage to Kansas and learn to fly it from the factory authorized test pilot and instructor Terry Thornton. I considered this to be sage advice, as the Mitchell Wing did not harbor a positive reputation among a large percentage of the ultralight pilots that I’d met. In fact, I’d been regaled with stories of friends of friends who knew guys who’d died or had near death experiences in the A-10. I’d also been advised that only an idiot would fly one. “Completely unstable,” they said. “Got no tail, ya know. Yaws all the time so ya can’t hold a decent course. Short coupled and pitch sensitive, they are. Make one mistake and they’ll tumble or spin! Got a vicious stall too. Can’t recover from it. Drop ya out of the sky like a lawn dart. Yes sir, the damn thing’s possessed. Pure evil, if ya ask me!” Of course, there were more severe indictments, including one that suggested alien abduction of A-10 owners, but I ignored those as mere hokum.
Now that the restoration of #275 was well underway I decided that it was time to make good on my promise and maybe, in the process, dispel some of the malevolence and doubt that had been lurking in the back of my mind. Rifling through the paperwork that came with the A-10, I found Terry Thornton’s phone number and made the call. There was no one home so I left a short message on the answering machine explaining my mission. The call was returned a few days later by a gravelly but enthusiastic voice that drawled, “Come on out, son. We’ll have more fun than the law allows, guaranteed! Oh, an’ you can drop that Mr. Thornton stuff. Call me ‘Terrible’ like everybody else.”
I was beginning to like this guy. And in the course of the conversation that followed, I explained my simpleminded learning philosophy based on advice from the previous owner. To wit, “Forget all the crap you’ve heard, keep an open mind and do what old Terry recommends. The guys who have the most trouble flying the Mitchell are the experienced guys who think they’re hotshots.” This brought a laugh from the other end of the phone line because it turned out that Thorton’s philosophy of flight instruction meshed quite well with this. As far as he was concerned flying the wing was no big deal. Once the theory was presented and understood, the flight instructor’s primary job was to keep the student alive long enough to make it happen in the physical sense. Logical.
And so it was that I made arrangements to fly to Kansas City, MO and then drive west to the tiny farming community of Culver, Kansas. It wasn’t easy to get the time off. In fact, if it hadn’t been for a sudden, unexpected business delay, I might not have had another opportunity for nearly a year. But, when the one-week opening in my schedule magically appeared, I headed west like a shot, hell-bent for flight time.
I rolled into the driveway of Terry’s Sunshine Inn late one sultry afternoon in August and was met by a short, pleasantly rounded individual that turned out to be none other than Terrible Terry himself. After I got settled in one of the rooms of his small bed and breakfast we walked to the hanger at the back of the property and I got my first view of the 1000’ grass strip that was “Culver International Airport”. I also became acquainted with Terrible Terry’s T-10 trainer that would lift us into the sky numerous times in the coming days. Unfortunately, flight opportunities were limited by the oppressive Kansas summer heat and humidity. All things considered, the density altitude must have ended up being close to the summit of Mt. Everest for most of the day and early evening. This left a narrow window of flyable conditions just after dawn. Thus it was that Density Altitude effects became the first subject of some thirty-six hours of ground school that would be part of the visit.
Terrible Terry, you see, besides being a CFI with thousands of hours in all sorts of aircraft, was also a bit of a scientist. He’d carefully measured the takeoff run of the T-10 and found it to be just short of 500 feet under most flyable conditions from a grass strip with two hefty passengers aboard. The power to weight ratio of the Rotax 503 powered T-10 is nearly the same, in fact, slightly higher than a 277 powered A-10. This makes their performance roughly the same when loaded at a similar percentage of gross weight. Therefore, unless you’re a featherweight and have a stiff headwind in the dead of winter, you’d better have 500+ feet of open space ahead of you before making any take-off attempts.
Another item for ground school was weight and balance. A great deal of the bad press given to the Mitchell Wing can generally be traced to improper placement of the CG. The recommended technique is to put the pilot in the seat with a full tank of fuel (2.5 gallons for the standard tank in the cockpit) and then measure the weight on each wheel. The nose wheel weight should be 17% to 22% of the total weight (i.e. total of all three wheels). Outside this range the wing’s performance tends to be “uncertain”. Pitch response quickens noticeably as the 17% mark is approached and is reserved for pilots with considerable time in the aircraft. The best place to begin for a “novice” Mitchell Wing pilot was a more docile 19%-20%. If a larger, non-standard fuel tank is installed its wise to check the weight and balance with the tank both full and empty to make sure the CG is still within the desired window. I asked where the actual CG was located and was told that the manuals didn’t say, but it seemed to be approximately three feet back from the nose of the wing (not the pod), probably in the vicinity of the pilot’s shoulders.
This bit of weight and balance knowledge went a long way toward explaining complaints of extreme pitch sensitivity. I remembered one individual who told me he had removed a diver’s weight belt from the nose of a newly acquired A-10 prior to his first and, it turned out, only flight. His experience with ultralights didn’t seem to involve much stress on weight and balance. “Aw hell, that shit don’t make no difference. I just fly ‘em.” Said he. Unfortunately, he didn’t connect the presence of the weight belt with a CG adjustment by the previous owner. He survived, but another black page was written in A-10 history.
The next little pearl of wisdom came during Terrible’s explanation of the Mitchell Wing’s control system. He pointed out that the Stabilators were activated through a mechanical mixer in order to provide roll and pitch. What the new pilot must understand is that full left and right deflection of the articulated upper portion of the joystick is available only when the stick is in the center (neutral) position. As the stick is moved fore and aft, the left and right deflection diminish, finally ending up at zero when fully forward or back. This diamond shaped response has been the bane of many, experienced, three-axis, General Aviation pilots who’ve come to expect aileron control to keep the wings level during the landing flare. The result is generally a ground loop and more fodder for the “A-10 is evil” myth.
The secret of control during landing is in the drag rudders. What the pilot must do is to learn to keep the wings level using short applications of the rudders. In fact, it’s quite possible for the average pilot to fly all day using only the rudders for turning, as they induce roll as well as yaw, and create a very acceptable, nearly coordinated turn. For many, the stick becomes primarily a pitch (speed) control with only occasional roll inputs required for rough air.
Armed with this new understanding we took to the air the following morning and I attempted to put theory into practice. It wasn’t at all what I’d expected. The first thing I learned was that it is very easy to over-control the T-10 with the rudders. This resulted in the nose wandering back and forth across the compass heading, much to my great annoyance. Back on the ground, after the first flight, I was convinced that the Mitchell Wing had to be the squirrelliest aircraft I’d ever flown. And if #275 behaved in the same fashion it wouldn’t be long till there was a FOR SALE sign hanging from the windshield. It wasn’t until well into my second hour of flight that I finally succeeded in getting the yaw under control. After that, it was fairly easy.
That first flight was also notable in that we did a few stalls. They were very unspectacular, quickly converting to a stable, mushing, sink. Terry warned, however, that an aggressive attempt to stand the wing on its “tail” could result in a tumble, thus the reason that the factory had large orange stickers inside the wing, within view of the pilot, warning against doing intentional stalls and spins. I had asked about spins the night before and was told that it took a great deal of effort to make the Mitchell Wing spin, but in the unlikely event that you did succeed, recovery was pretty much the same as with any other three-axis aircraft. Hmmm…I was beginning to think the reported homicidal demons must have vacated Terry’s T-10 due to boredom. The wing was definitely different, but it really wasn’t that hard to fly if you took the time to learn the proper techniques. And it must be flown all the time. This is not a hands-off kind of airplane. The pilot must constantly think ahead and does not relax until back on the ground with wheel chocks in place. The clean design also makes it remarkably fast and fuel efficient considering the small engine involved. With this in mind, I probably wouldn’t recommend it to a novice. On the other hand, it doesn’t take the skills of a Chuck Yeager either. I was, however, beginning to see how its fearsome reputation had evolved and that experienced pilots who tried to fly it like any other three-axis machine could be unpleasantly surprised.
Without a doubt, the most difficult thing for me to master during the time in Kansas was the landing. Ideally, you fly the T-10 to a point ten feet or so above the runway, round out and then, after ensuring that the wings are level using the rudders, cut the power and let it settle with a bit of a flare so that the main wheels touch first followed by the nose wheel, all in one smooth maneuver. I was warned to be very careful not to overstress the nose wheel assembly. Attempting a three point landing, high speed taxiing on rough terrain or slamming the nose down hard generally ends in some part of it being bent, torn or broken. This was especially true with the older, bicycle headset design. A moment’s reflection brought back the vision of #275’s torn assembly, which reinforced Terry’s advice.
Approach speed for the T-10 was 60-65 mph on the Halls wind speed indicator with the VSI showing no greater than about 200-300 ft/min down. The A-10 approach speed, I’m told, should be in the 45-50 mph range depending upon wind conditions, with a similar rate of descent. Controlling approach speed and descent rate from first entry into the pattern are extremely important. The Mitchell Wing gains speed quickly, and it does not lose speed as rapidly as other ultralights. It also likes to float in ground effect under certain conditions. Nevertheless, hard landings are not unusual if descent rate is not checked at exactly the right moment. Considering that I’d made hundreds of engineless landings in sailplanes using a very similar technique, the transition to the A-10 should have, in theory, been fairly easy. But, it wasn’t. Perhaps it was the fact that I hadn’t done it in quite awhile or maybe I’m just getting too old. Whatever the case, I had a great deal of difficulty developing the judgment required to get the T-10 softly to the ground, on the spot where I wanted it. Needless to say, there were plenty of go-arounds and considerable frustration on my part. It wasn’t until the last hour on the last day, at the end of nine flight hours for the week that things finally clicked and Terry wasn’t hovering over the stick and throttle when I brought it down.
Landing practice, by the way, was carried out at the tiny Minneapolis, Kansas airport using its single, paved runway. Local traffic was pretty much non-existent, except for an occasional takeoff by the resident crop-duster. Thus the only witnesses to my extended learning curve were some thoroughly bored cattle. There was one interesting point here. On more than one day, we encountered steady crosswinds of near 90 degrees, often gusting in the 10-15 mph range. Besides some additional rudder input to stay centered on the runway, the crosswind made very little difference in the way the T-10 handled during landing. I was beginning to appreciate the lack of a tail.
We also encountered some very rough air while flying the landing pattern. This was generally turbulence due to thermals as the day advanced toward noon and was always worst on the crosswind leg over a neighboring plowed field. Aggressive use of the rudders and the roll authority of the stabilators were often required to maintain control. The strength and consistent performance of the aluminum wing was a great comfort under these conditions.
The only maneuver that I was unable to try was the simultaneous deployment of both rudders to lose altitude quickly in the event of a too high approach. Unfortunately, the T-10 rudder pedal arrangement doesn’t allow for independent deployment of the rudders. The only information I have is from the previous owner who did use the technique once, after being pushed too high on approach by a series of local thermals. He said it was quite effective, but a bit scary. Evidently, due to the sweep of the wing and the placement of the rudders, the nose tends to lift as the rudders are applied. This can be a bit disconcerting as the speed will drop and plane will appear to be headed for a stall. Therefore, the pilot must be ready to apply forward stick to correct for this as the rudders are simultaneously applied. I did ask about doing a slip with the A-10 and found out that the cross control maneuver could be done. But, with no tail, the side profile of the Mitchell Wing did not offer much drag to make it effective.
It was here Minneapolis and at Culver that I learned about the ground handling characteristics of the wing. During taxi, the turn radius was nothing to brag about, yet the steerable nose wheel system did do its job quite well. A quirk I discovered was that the pilot cannot see the wingtips from the cockpit. Dihedral is introduced at the outer wing sections that lifts the tips out of sight. This and the long wingspan can make maneuvering in close proximity to buildings or other aircraft a bit hairy for the new Mitchell Wing pilot. On a rough field the wing also has a tendency to rock due to the suspension, which can place the tips uncomfortably close to the ground. Taxiing can thus require some extra care and forethought as well as lots of practice.
I also found that visibility in the upward direction is severely limited by the large wing overhead. One must maneuver on the ground, making slow turns, to ensure the pattern is clear on uncontrolled fields before takeoff. This is a familiar requirement for a variety of high wing General Aviation and Ultralight aircraft and not unique to the design. By the same token, vigilance in the air is also mandatory, as what’s above you will be obscured.
Takeoffs were similar to other three-axis ultralights with a tricycle landing gear. The only exception might be in the long run required to get airborne. The recommended technique was to keep the stick slightly forward of neutral until enough ground speed had been gained to “pop” the wing off the deck with a quick back movement of the stick. I found that when the T-10 was ready to fly the nose would get light and begin to “chatter” with a slight loss of lateral control. After learning to recognize this it became fairly easy to leave the runway and then gain airspeed for the climb-out. The climb rate of the 503-powered T-10 was not exactly stunning with the two of us in the cockpit, but certainly adequate. What the A-10 will do with its 277 is yet to be seen.
There were also some interesting, if minor, design changes Terry had introduced that I discovered while doing preflights. Several of them I decided to import for my A-10. The first is to add an aluminum doubler strip to the outside web of the rudder hinge assembly. The purpose of this is to help prevent the kind of cracking I encountered on #275. Next is the addition of turnbuckles in the rudder control cables where they emerge from the pod and connect to the wing. In concert with the turnbuckles, he used screw-adjustable rudder stops on the wing tip shrouds in place of the fixed rubber pads. This change eliminated the need to rivet aluminum tabs to the aft edges of the rudders, which are then bent to trim the ship in yaw. As for pitch, I was advised that the stabilator adjustment angles shown in the video were to be considered only a starting point. Further adjustment is often required. The T-10, for example, needed quite a bit more “up” than recommended. Terry had also pop-riveted a small aluminum tab to the left stabilator for fine adjustment. What #275 will require for trim and optimum control will have to await the first test flights.
An item not imported, but one I considered, was Terry’s addition of a Lexan window in the Stits covering on top of the wing center section. On one flight it revealed the presence of a National Guard Chinook helicopter transiting above us. Neither of us had detected its approach. Obviously more visibility is a good thing. In pursuit of this, I learned that on some of the earlier A-10s the factory used Mylar film instead of fabric on the upper center section of the wing. This was discontinued, however, to keep heat buildup to a minimum during the summer. The doped and painted fabric was also more resistant to the effects of ultraviolet radiation. The T-10’s windshield, I noted, was also much higher than the one on my A-10. Still, this did not keep me from getting whacked in the face by a large flying insect during one of the landings. As a result, I will definitely be wearing a helmet with a face shield in #275 and may cut the new windshield about three inches taller. The final thing I took a liking to was the long brake lever in the T-10, which made me glad that I had dumped the tiny, two finger, red brake handle in favor of a long custom unit on my A-10.
I also took careful note of the instrumentation on the T-10. The most trustworthy airspeed indicator on board was a Halls Brothers Wind Speed meter (0-80 mph) clamped to one of the forward diagonals. I gained new respect for this device after watching the standard aircraft ASI on the instrument panel produce some pretty bizarre readings while in flight. My suspicion was a problem with the pitot line or perhaps the ASI itself needed to be replaced. Nevertheless, the Halls always functioned. Terry advised he’d discovered the Halls tended to be less accurate at the higher speeds, producing readings a few miles per hour faster than your actual speed. Still, that’s not a bad thing when you’re approaching Vne. The other instrument that proved useful was the Vertical Speed Indicator, especially during final approach. Therefore, I now have a 2 ¼” VSI on my list of things to be crammed into the limited space on my own panel.
Then too, there were a number of human factors related to the design that I became intimately aware of as the flights progressed. First is the fact that at 6’3”, 220 lbs, it’s a real bitch to get in and out of the cockpit. Being a dwarf has its good points with the T-10, or the A-10. I’ve eased this situation slightly by the installation of the factory “lift kit” which raises the wing another few inches above the cockpit. Besides a bit more head room for the helmet, it also makes entry and exit a hair less than a contortionist act. Once seated, however, the cockpit in the A-10, although tight, is fairly comfortable. Not so with the T-10 seat which grew very uncomfortable after an hour of flying. The new seat cover on #275 will therefore have more padding than the old one. Another annoyance was constantly banging my shins on the bottom of the T-10’s instrument panel when operating the rudders. The rudder pedals themselves were rather awkwardly placed and lacked enough fore and aft adjustment for any real comfort in operation. I’d noted the same problem on my A-10 and remembered one other pilot telling me that he often ended up with knots in his calf muscles after long flights. Unfortunately, I have not been able to come up with a redesign remedy for this. I also learned quickly that, once strapped in, it was very difficult to reach the instrument panel for such mundane things as zeroing the altimeter, flipping switches, etc. Therefore, my instrument panel design and layout will require some serious thought.
Back on the outside again, the low wing was a real pain for anyone doing refueling or contemplating a recoil start of the engine on the T-10. I had toyed with the idea of removing the electric starter from my A-10 to save weight. But this vaporized after watching Terrible Terry crouched under the wing trying to get a good pull on the occasionally stubborn 503 without getting too near the spinning prop. While most of the early A-10s did have a recoil start handle placed over the pilot’s left shoulder for starting while seated, I was not enthralled with the idea. At my age, the less stress on these old bones and shrinking muscles the better. So, the starter will stay. I’ll just move the battery forward as part of the ballast for a good CG.
As for refueling, the seven-gallon, custom tank in the T-10 occupied most of the volume under the seats, extending forward into the floor area of the cockpit. The fuel filler cap was also located here, which meant that any spilled fuel ended up drizzling down to the floor and then aft out of the open rear of the T-10 pod. Although the design appeared quite safe, I was very glad that the tank on my A-10 would be on the back of the seat, keeping any fuel spills outside the cockpit. I would also revisit the orientation of the tank’s fuel filler to see if I could make it less of a backbreaker.
There were other benefits from the trip, too. Beyond being a CFI with considerable experience in all sorts of aircraft, Terrible Terry is, to say the least, a unique individual and one of the most interesting people I’ve ever met. How many guys do you know that own a dirigible? He’s also a four star chef with an amazing repertoire capable of destroying anyone’s diet with a single meal. And, I found out that I loved Kansas. Tornados be damned. The locals were great. Coming from the aero-phobic East, I was amazed to find that the neighbors considered it downright unfriendly if you flew by them in the fields without a tip of the wing or passing low enough for a hearty wave. I can still remember the return waves, the smiling faces and the tractor lights flashing their greeting. The flat prairie heartland is a wonder of visibility, and emergency landing areas are as near as the ever present open fields below you. I understand now why barnstorming was such a popular activity out here.
The bottom line in all this is that the time and money spent in learning the ways of the wing were priceless for me, especially in terms of confidence and safety. Thus the reason I strongly recommend that anyone intending to own or operate an A-10, or T-10, make it a point to contact Ameriplanes for reference to an authorized instructor.
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