by Art Mattson, A.M.R.&D. Inc. reprinted from Pipers mag. Nov. 1995
PROPER RIGGING of the flaps and ailerons can change your PA-28 from a "Doggie" airplane to a much improved airplane. However, improper rigging on your PA-28 can rob you of six to eight mph in cruse, and decrease your rate of climb at the same time. Many of the people with whom I’ve discussed rigging have gotten back to me, stating how much better their airplane performed after rigging to neutral. A lot of FBO’s know how to change the rigging. If the airplane has a heavy left wing, they lower the left flap. But, amazingly, they do not check to see if the plane is rigged properly in the first place. The important fact that is overlooked is the airplane should be rigged to neutral and then flown before any adjustments are made. THE MOST POORLY RIGGED PA-28 OUT THERE IS THE CHEROKEE 140. So please, you 140 owners pay attention!! Pipers’s Service Manual shows how to make a rigging tool. This is very simple to do. All you need is a piece of aluminum angle or channel that is 1.5 inches by 1 inch by 31.5 inches long. This piece must be straight! Measure 13.25 inches from one end of the tool and drill and tap a hole for a 1/4 by 20 ( 20 threads per inch) or 1/4 by 28 ,one inch long bolt. Thread the bolt through the base of the angle or channel until it extends 3/8 of an inch out the other side. ( You can also use a 3/8-inch spacer and a 3-foot straight edge as a substitute.*) Now you go to the airplane. The flap is checked at the outboard end on the underside of the wing. The end of the protruding bolt is placed on the rear spar. The short end of the tool should line up with the trailing edge of the flap. The long end should go forward parallel with the ribs. The tool should not touch any rivets or screw heads. Neutral rigging of the flap is achieved when the short end of the tool touches the trailing edge of the flap, the bolt touches the rear spar, and the long end touches the underside of the wing skin all at the same time. Now match the bottom of the aileron with the bottom of the flap, thereby achieving neutral rigging for the aileron. This is the best way to fly your airplane. LEARN TO LOAD AND MANAGE FUEL PROPERLY. When flying by yourself ,use the left fuel tank first. After rigging your airplane to neutral, you should fly alone with an even fuel load. The airplane should have a slightly heavy left wing when flying under these conditions. If not, this is a strong indication that something is wrong; bent wing tip, poorly installed wheel fairing, bent flap or aileron, etc. FIND THE PROBLEM AND FIX IT!! It is extremely important that the rigging be very close, as 1/16 of an inch will make a difference. For example, we had a customer come in to have Met- CO -Aire wingtips installed. He complained of having a heavy right wing when flying alone with even fuel, completely opposite of what would be expected. When checking the rigging, we found both the left aileron and flap were 1/8 " lower than the right. We rigged to neutral by raising the left flap and aileron to match the right wing, and the condition was corrected.
RIGGING YOUR AIRCRAFT PROPERLY IS QUITE SIMPLE, AND WELL WORTH THE EFFORT!
*(If substituting a 3/8" spacer and 3’ straight edge, the spacer goes on the rear spar. Line up one end of the straight edge with the trailing edge of the flap, then run the straight edge over the spacer, parallel to the ribs.)