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Jack asked:
I'm having Kenney Wheel Fairings installed on my 1947 - 415C Ercoupe. The A&P is concerned about the way the instructions say to jack the plane up. Do you know the proper way to jack up my plane?
Jack,
My Alon has the spring steel gear legs on it, and when I had the wheel pants on the plane, I had to take the weight completely off of the gear leg in order to get the wheel pant off over the tire. In order to do this, I removed the wing tie down ring, and used a large area washer (about 2 inch diameter), a few regular diameter thick washers, and a bolt that would screw into the tie down ring hole. I then used a jack on the head of the bolt to jack the wing. The large area washer spread the load out onto the surface of the lower spar capstrip, through the wing skin. It is important NOT to let the load of the airplane be handled by the threads of the bolt, because these threads are just threaded into a steel nutplate, and that nutplate is riveted onto the upper surface of the flange of the bottom capstrip (if that makes any sense).
The point is that if you just screw a bolt into the hole, and let the weight of the plane be transmitted to the nutplate, the two small rivets that hold the nutplate in place may (and probably will) fail. These rivets are not strong enough and are not designed for supporting the load of the airplane in the upward direction. The force must be applied only to the capstrip. Use the washers, and tighten the bolt down good so that the only force felt by the nut plate is the torque of the bolt forcing it tightly against the cap strip. (Don't over do it, just make it tight.) The bolt head is only to center the jack on, and to transmit the load to the large area washer, which transmits the load to the cap strip. A flat piece of 3/16ths inch thick steel about 2 inches wide and 6 or 8 inches long would do an even better job of distributing the load, in place of the large area washer.
Of course, if the jack slips on the bolt head while you have it jacked up in this manner, the jack will punch a big hole in the wing, in which case you never heard of me, and I never told you anything about all this!
I would only jack one wing at a time like this, and only support it this way long enough to get some other support under the center section as described below. The plane will not be very stable while supported in this manner.
The Alon Service Manual says to jack the plane at the main spar "inboard" of the wing tie down ring, and then place a padded support under the wing center section inboard of the landing gear leg. I think the reason that they said to jack it inboard of the tie down ring is because a short distance outboard of the wing tie down ring, the heavy aluminum lower capstrip ends, and the remainder of the outer spar is made from parts that are not as strong as the cap strip.
As always, check with your licensed mechanic before using any of this info. I'm not a licensed mechanic, so take this info for what it's worth.
Best Regards,
Wayne DelRossi
Alon N5618F
Hours logged since restoration: 119.6
Wayne DelRossi
Alon N5618F
Hours logged since restoration: 119.6
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