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On Tuesday the EAA and EAA Vintage Aircraft Association filed comments on the FAA's Airworthiness Directive affecting most high-wing vintage Piper aircraft, claiming it is too broad and is flawed. The AD requires 1025 carbon steel rudders to be replaced with new, 4130N low-alloy steel rudders, affecting an estimated 31,000 aircraft. The EAA and VAA propose the AD be rescinded and more data be collected before any follow-up action is taken.RELATED STORY:FAA extends comment period for Piper aircraft rudder replacement AD
The proposed AD was published in October as a result of two crashes involving Piper planes caused by broken rudder posts that structurally failed above the upper hinge in flight. This AD was also issued in response to an Airworthiness Concern Sheet from Sept. 4, 2020 when the FAA became aware of five additional broken rudder incidents as far back as 1979. Depending on the mile, the affected planes would be required to replace the rudder posts within two, three or five years. The FAA estimates this will impact 30,992 planes on the U.S. registry and cost U.S. operators $92,976,000.
After the AD was issued, other groups like the AOPA and Short Wing Piper Club urged the FAA to extend the comment period from Nov. 20 to Feb. 20, which the FAA complied with. The groups said the proposed ruling was controversial and could drive substantial costs. Many of the comments have cited concerns over the scale of the AD and the possible inaccurate estimated cost for replacement. Some comments asked for the removal of lower-horsepower aircraft from the list and shifting focus to higher-powered aircraft.Aft view of PA-12 accident plane and the plane's fractured rudder post, from NTSB docket
The EAA and VAA have taken issue with the broad scope of the AD and the required replacement action. With a replacement requirement of two to five years depending on the aircraft model, the groups said that at the current production rate, replacing the rudders would take 75 years. The comments recommend that the FAA rescind the AD and collect more data from the community before any follow-on action. The VAA performed an extensive engineering study to analyze the applicability of the AD to the various models and proposed an alternate inspection and repair technique that does not require a new rudder. Rather than an AD, the EAA proposed the FAA issue a Special Airworthiness Information Bulletin.
"The combination of the small number of occurrences, coupled with the extensive modifications of the two aircraft discussed in the AD, combined with the limited and incomplete information provided for the five other instances, and the resulting safe landing of all aircraft involved, EAA feels that the proper course of action for the FAA is to withdraw this proposed AD and to issue a Special Airworthiness Information Bulletin," the EAA comments said.
The comments note that there are no Service Difficulty Reports or NTSB incident or accident reports on any aircraft proposed to be covered by the AD. The groups claim there is no evidence that either the operational or maintenance history of the aircraft which was used to support the determination that there is an unsafe condition in an entire fleet was investigated or addressed. The NTSB report documented the failure of the rudder posts on two modified seaplanes in Alaska, as well as five other cases over 44 years. The aircraft documented in the report had aftermarket 160-hp engines and rudder-mounted beacon lights, which the two groups say likely altered the stress on the rudder posts. The comments note that the incidents the FAA's AD relies heavily on have not led to subsequent additional damage, loss of aircraft, injury or life.NTSB images of cracked rudder from PA-14 accident plane, from NTSB Docket
The groups state that the proposed AD does not include documented issues other than the examples of the modified PA-12 and PA-14, yet it applies to nearly all high-wing Piper models. Both of the aircraft had significant modifications and one had field approval for a higher horsepower engine. The modifications, coupled with the higher hp engine and installation of lights on top of the rudder assembly, likely contributed to the issue. The EAA requests that any airworthiness action be limited to the airframes with modifications, operating environments and/or histories found to be hazardous through a data-driven assessment.
The EAA supports an investigation of all alternatives to the complete rudder replacement. One repair technique suggested by other commenters is the removal and replacement of the rudder post, which can be completed by a competent metalworker. The VAA's report describes a periodic inspection technique and a minimally invasive and economical way to reinforce the rudder post internally. The repair method achieves an equal level of safety to the replacement of a rudder without a re-cover required. The EAA supports a major reduction in the scope of the AD but urges the FAA to consider all and any possible and practical means to ensure safety. "EAA believes this AD is flawed in regulatory process, scope, and requirements. It is based on limited data, the required action is not possible in the timeframe required, the affected models list is vast, and the action required is excessive," the comments conclude. "We urge the FAA to withdraw this AD and collect additional data before embarking on any further airworthiness action. If such action is warranted, it must be targeted and practical."