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STALL CHARACTERISTICS IN A VariEze
(From CP28, Page 4, April, 1981)
I just wanted to drop you a note telling you of the first flight of VariEze N60SD My bird is equipped with an 0-200 Continental, wing cuffs, speed brake, full instrumentation and a Cessna alternator. I am planning on installing a lightweight alternator.
Sunday morning 2/22/31 was clear, calm and cold, a perfect day for taxi aid flight tests. Bruce Tuttle flew his VariEze N95BC down from Ogden and was on hand for help with initial setup and check out of my new bird. Another builder, John Wall, was also very helpful.
Bruce and I discussed the procedure I would be going through starting with low speed taxi tests, high speed taxi tests and runway flight. All went per plan until I attempted my first runway flight. I had accelerated to 80 mph and pulled the power off and with pitch up command it lifted off and went unexpectedly to 50 feet. I could see that I would not want to attempt a landing on the remaining runway and so after only a slight period of indecision I added power and climbed out.
That first lift off and flight came somewhat unexpectedly and I was immediately filled with apprehension about landing. This was where all my practice in a Cessna 172 and Mooney 231 would have to pay off. I brought it around the pattern at 100 mph on downwind, 90mph on base and 80mph on final. I approached low with slight power and crossed the numbers with the runway visible over the nose. Then I chopped all power and it sank unexpectedly fast and my reaction was to pull up elevator, which wiped out my view of the runway and I found myself feeling for it for a nose high landing. Not too graceful but I got it down on the mains and then dropped it on the nose pretty hard.
The roll out was exhilarating. It was the first opportunity that I had to think about what had just happened. We checked the plane out for landing damages (none) and then it was off again. All in all the first flights were so successful that I logged 6.1 hours that day including about one hour flown by Bruce, & some formation flights alongside his Eze. My wife, Diane rode with him and took some air to air pictures. I also flew some long orbits within my restriction area getting the feel of the plane.
No slow flight was attempted but I did investigate high cruise. I got 160 mph: indicated at 8000 ft. straight and level which trued out at 181 mph (no wheel pants, no spinner and no nose gear covers) at 2800 rpm.
The only flight problem was a slight left banking tendency. It flew ball-centered with no yaw trim. Roll rate was fantastic, with the rudders it was really quick. Stick forces were roughly equivalent for" pitch and roll and very comfortable.
I ended up the day doing touch and gos, working on my technique. I found that it was best to carry a slight amount of power and fly it onto the runway. A Cessna-style flare always resulted in a nose-high, high sink rate landing and so I soon learned not to do it that way. As the sun was dropping low I reluctantly had to call it a big day and put my new toy away.
The aircraft is everything I had dreamed of and more. It made the 23 months construction period seem like nothing compared to the pay off in fantastic performance and pride of building and flying my own airplane.
Thank you is just not enough to say to you for providing this fantastic design for me, and others who have a little ambition and a big dream.
I hope to fly off the restrictions in about a month and one of my first cross country flights will be to Mojave to show you the plane and thank you in person.
Thanks again and I'll be seeing you soon.
Shirl's initial stall tests were,
done with nose-ballast as required to bring the cg into the center of the first
flight box. Stall characteristics were correct - a stable trim at full-aft stick.
He then removed his nose ballast, which resulted in a cg of approximately 101,
about 1 inch forward of the aft limit. The stall characteristics at that cg were not
desirable. He reported that an excessive angle-of-attack could be reached using only
a few degrees of elevator travel, and the aircraft would roll-off on the right wing before
full-aft-stick was reached, particularly when stalled at low power.
When he reported these characteristics to us, we asked him to recheck cg because those characteristics normally occur only when the cg is aft of the aft limit. We also asked him to check, the contour of his wings for any inconsistency that could cause premature stalling. He did, and was unable to find anything wrong. Shirl and Diane flew into Mojave last week, their first long trip in their new VariEze. Dick and Mike flew it, evaluating the entire flight envelope. N60SD is an excellent flying machine with good roll rate and control harmony. Its stall characteristics, however, are not how a VariEze should be. Instead of the stable trim condition normally obtained at full-aft-stick, N60SD behaved as if it wanted to drop a wing unless the pilot carefully controlled ailerons and rudder. Also, the nose seemed to trim to, a higher angle than the prototype, N4EZ.
Remembering that these were the characteristics, that existed with N4EZ when it was tested at a cg aft of the aft limit, we were convinced that Shirl had done his weight and balance incorrectly. So, we rolled out the platform scales and lifted N60SD onto them. The mystery, however, still existed when the numbers were all calculated - we obtained the same cg that Shirl had reported. We measured the planform dimensions and confirmed that his airplane seemed to be built accurately. It must be that his airplane does have some difference in incidence or contour of the wing or canard, however, we did not determine this.
When Shirl and Diane left, all we could tell them was to go ahead aid install 12 lbs of permanent ballast in front of the battery to keep the cg forward of station 100, thus resulting in the desirable, stall characteristics that VariEzes should have.
The purpose of telling you this story is to reiterate to all builders that they cannot assume that each airplane is identical to our prototype. We have learned that variations are to be expected, since these airplanes not come out of one mold in one factory. Thus each manufacturer should star this test program at the most conservative condition (center of first-flight box cg, for example). Then, as described in the Owners Manual, open the envelope slowly, carefully, and safely. Place the limits on your individual aircraft where they belong rather than assume they are identical to the limits used for N4ez