Mechanics race to reduce cost of Piper rudder AD
An airworthiness directive affecting thousands of high-wing Piper aircraft has stoked the creativity of vintage Piper enthusiasts, particularly those with airframe and powerplant certification, who headed to their workshops to devise solutions that reinforce rather than replace.
The final rule on the AD, released February 13 and effective March 20, requires the replacement of rudders with rudder posts made from 1025 carbon steel on the affected aircraft with rudders that have posts made from 4130 low-alloy steel. The rule also allows alternative methods of compliance, or AMOCs which, with FAA approval, could ease the anticipated strain on the supply of replacement rudders.
The various vintage Piper communities, which include short-wing, J-series, and Super Cub-specific groups, are buzzing with relatively economical approaches to repairing, reinforcing, and replacing the 1025 rudder posts that might gain FAA approval.
Carruthers said he is writing a proposal to the FAA for approval of his method, which involves removing the rudder and reaming the rudder post to the top to remove weld penetrations that cause irregularities to the post’s interior diameter. Once the inside of the post has been machined back to roundness, Carruthers plans to insert a 4130 tube inside the existing rudder post, along with corrosion inhibitors.
This revised assembly would essentially be a press fit and would require “some persuasion” from a mallet, Carruthers said, but the inner tube would also be held in place by the tailwheel hardware. The reaming process would remove minor corrosion, he added. Best of all, the procedure would be done without removing the rudder’s covering.
Carruthers and other pilots and A&Ps are resigned to dealing with what could be a drawn-out submission and evaluation process for AMOC applications. “The FAA is going to be inundated with AMOCs,” said Carruthers, who flies a PA–22 Tri-Pacer. He at least hopes to be close to the head of the line. “We are in the process of writing it now.”
For rudder suppliers, and there are not many, the prospect of AMOCs could be more help than competitive hindrance. The FAA estimates about 6,500 of the affected aircraft, which were built before the company switched to 4130 posts in 1974, are still in service and have not had their original rudders replaced previously.
“We welcome any AMOCs that the FAA approves,” said Jim Dyer, owner and president of Univair Aircraft Corp., a longtime supplier to the high-wing Piper fleet. Dyer, who flies a J–3 and a Super Cub, explained that all the rudders in his inventory are “spoken for” and his two seasoned welders capable of assembling new rudders can work only so quickly.
“It takes a couple of hours to assemble a rudder, and welders can get burned out if they do the same thing all day,” Dyer said. AMOC approval would reduce the strain on his operation, which is already busy.
Given that the AD allows a period of two to 10 years to comply, depending on the aircraft’s horsepower and rudder design, mass groundings of Piper aircraft does not seem likely. The next few years could be somewhat hectic, though, as owners search for parts and mechanics try to squeeze a few more customers into their shops. The effort is worthwhile for fans of tube-frame, fabric-covered high-wing Pipers, many of whom would not consider owning a riveted aluminum aircraft.
Carruthers said members of his short-wing community are motivated to comply with the AD because they want to keep their aircraft flying, even beyond their lifetime. “I have grandkids and I would like my airplane to be around for them,” he said.
