aerosiam
Joined: 26 May 2008
Posts: 59
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 Posted: Sat Feb 28, 2009 8:12 pm Post subject: Aileron control problem |
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When our Allegro 2000 was delivered, our ailerons seemed unusually stiff.
On the ground, the ailerons were light but became progressively stiffer at speed to the point where it took about a 3 pound pull to move the stick off center at 110 knots.
We had no point of comparison but after some very helpful emails from Thom Riddle, it was clear that the Allegro should have light ailerons. Although it is normal for stick forces to increase with speed, ours felt excessive and unnatural.
We removed the wings and stripped down the aileron control system and found 2 problems.
1. There is a long 8 foot pushrod from the bellcrank in the middle of the wing which extends all the way into the cabin . It has a 2 triple nylon wheel bearings. One is near the wing strut and the other at the wing root.
The pushrod showed wear from only one point from each bearing. From the top on the wing bearing and from the bottom on the root bearing. This suggested the rod was bending in a vertical ‘S’ and starting to jam on the bearings. Moving the ailerons increased the load and would account for the stiffness.
2. A rod in the cabin attaches to the triangular bellcrank and passes thru 2 nylon bushings one of which is in a tube welded to a flange and attached to the bulkhead near the top seat belt attachment points. (see photo). It looks like the factory had not welded the flange correctly. It was misaligned quite badly and appeared to show attempts to bend it to fit. The rod missed the bellcrank by about an inch.
We replaced the long pushrods with a stronger tube and used spacers to correctly align the flange. Now the ailerons are very light and feel normal. I can only assume that the factory used the wrong spec pushrod on our Allegro or there is a third set of bearings missing which seems unlikely.
To check your plane, remove the clevis pin from the long pushrod where it meets the short red pushrod. The ailerons should move freely. Remove the clevis pin under the right hand luggage tray. The stick and bellcrank should move freely individually.
If the wing pushrod is bending, it will be visible in flight. The photo clearly shows the ailerons at cruise speed bending up to lie flush with the reflexed flaps (therefore 4.5 degrees) and way above the tip fairings.
Although we had problems with our ailerons, we have solved them and I like the system. I like an all-pushrod setup and the wing bellcrank, for example, appears solid and well anchored to the spar. The large ailerons are light and powerful and make the Allegro agile for a long wing plane.
We have flown 150 hours with the Allegro including a 2000 mile round trip from Thailand to Malaysia and we really like the airplane. It is very comfortable to fly with pleasant handling and is easy to land. It is a great cross country plane with lots of luggage space. We have the long range tanks and even with the 100hp, the range and endurance is excellent.
Paul
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