The Federal Aviation Administration (FAA) has issued a final airworthiness directive (AD) requiring the replacement of rudders on specific Piper series aircraft.
âTwo non-fatal accidents in Anchorage, Alaskaâ
But Alaska operations are not the same thing as flying in the lower 48.
Restrict the AD to Alaska.
Wait okay so if the thing that theyâre replacing has nothing to do with the two documented failures⌠then how are the failures being addressed or are they not related or like what happened with that
Aircraft do move around. The automotive industry tried that. Doing regional recalls. Ahh, cars donât just stay in one state or areaâŚ
Agree⌠âletâs act before we thinkâ must be a motto somewhere in the hallowed halls of the FAA.
There are actually seven known incidents that were considered regarding this part; gonna guess that there are many more that were discovered and repaired.
Anyone remember the Cessna control column issue? I ultrasonically tested a mess of them, including some âin stockâ at a repair shop, and also xrayed them. Half of them were below spec, with a visible corrosion line, at which point it would break if left alone.
Iâm just saying that in Alaska specifically that there are more rough field operations and THAT puts a lot more stress on a taildraggerâs rudder/rear-wheel assembly (and the rudder post).
It seems a bit dumb to make the majority of people who operate off of soft grass strips doing gentle Sunday flying have to replace non-fatigued perfectly good parts.
From these emotional comments it sounds like no one even read the AD first. There were over 300 comments submitted and addressed by the FAA. I suggest you go read them.
So now you have state-specific aircraft? What happens to a plane that spent 50 years in Alaska flying off of gravel and now is in Maryland? Does it magically get cured by moving to a horse farm with nice soft well tended grass? What if I want to fly to Alaska from here, do I stop in Seattle and get a new rudder on the way?
When a 737 lost a chunk of the fuselage because it did a lot of short hops in a humid salt water environment, did ONLY 737s that lived on tropical islands get inspected or was it all of them?
Besides for that, these airplanes are mostly older than anyone flying them, they were not made to last 100 years with no issues.
The FAA determined that corrosion and fatigue will accelerate the failures over time as the strength of the rudder is continually compromised due to the combined effects of corrosion and fatigue. Furthermore, many of the approximately 31,000 airplanes are not currently in service (currently there are about 13,000 active airplanes in the fleet)âand many of these airplanes already have rudder assemblies made from 4130N low-alloy steel installed. Therefore, as the rudder post failures have accumulated over time, the number of active airplanes with rudder assemblies made from 1025 carbon steel has decreased. Given that more rudder post failures are occurring within a shrinking fleet size indicates that the failure is occurring more frequently as corrosion progresses and fatigue cycles accumulate.
It seems like much of the fleet already has had this repair or maybe the planes are scrapped, we seem to be getting down to the remaining ones with original steel that are failing more and more.
Exactly Joe. The AD touches on that fact as well.
State specific? Why not?
Since BOTH failures were on aircraft operated in Alaska, then yes.
Rough fields and skis and floats all put abnormal stress on the structure of the tail post/rudder. When those operations are the norm where this happened then limit the AD to that area. All other areas just get inspections.
Is there a law I donât know about to keep track of what states airplanes have been in and for how long?
This seems like a total paperwork nightmare. How long do you get in Alaska? Does just landing there once put you over the limit? We all know salt water is enormously corrosive. Should there be special ADs for coastal seaplanes that donât apply to seaplanes in Minnesota or Wisconsin? Note that no 737 owners got away with âI fly long trips between low humidity airports no where an ocean so no ADs for meâ.
Should Cessnas that spend their lives on a ramp in Florida marinating in salty humid air have different ADs than Arizona Cessnas?
Do we REALLY need to wait for a fatal accident here and then get interested in rudders coming off?
Do we really need a forced replacement when an inspection has proven to be sufficient?
Do we really need a change in material when the original design metal lasts 70 years?
Well if they want to use inferior steel for another 70 years I guess they can, but the price difference between the old and new steel is probably about $3 or so. There is an AMOC in there somewhere too.
The 70 year thing is key. DC-3s and BE-18s didnât need their wing spars Xârayed back in 1939, but they do now. The planes are OLD. Chalk Airlines decided they knew better than the FAA as to what ADs should apply to their airplanes. The result was fatal for the airline and the passengers.
" They(the FAA) disagreed that missing equipment required by either STC or TCDS had anything to do with the only two documented failures." OK, so what was the missing equipment? Judging by the time-to-comply matrix chart, engine power and the presence of the aftermarket beacon are main factors in fatigue onset. The weight of the beacon is causing increased rudder flutter, exacerbated by increased speed. The rudder must flutter a little even at lower power and with no beacon because those planes get the most time-5 years to replace. Mass-loading the rudder with a beacon adds weight and slows down the flutter. The problem is physicsâŚfrequency and amplitude are inversely proportional. Given a fixed energy, slow down the frequency (flutter), and the amplitude (flutter) must increase. In this case, itâs the amplitude that is causing fatigue.
Do we really need a forced replacement when an inspection has proven to be sufficient?
The AD addresses the inspection option. Page down to: section D, âRequests Regarding Repetitive Inspectionsâ. TL;DR: Repetitive Inspections are not always physically or economically practical.
But if you think otherwise . . . the AMOC (Alternative Means Of Compliance) option (which the Short Wings club is pursuing) remains open.
Do we really need a change in material when the original design metal lasts 70 years?
Probably not. But if the AD is correct in establishing the need for fleet wide replacement, then it hardly makes sense to not upgrade. Is the replacement steel more expensive than the original?
Iâd suspect that a difference in the material cost of the rudder post is pretty damâ small as compared to the $3K replacement cost.
The FAA is a big bureaucracy full of entirely fallible humans. Humans donât like to be wrong or embarrassed, especially in bureaucracies. Thatâs where professional image factors into promotion and selection, right?
So once this thing was announced, the chance of somebody backing off their initial position regardless of evidence or discussion was slim. Hopefully we get better success with AMOCs. There are some feasible solutions that have been suggested by Koerner Aviation and some others. Discussions here and elsewhere help that AMOC process along.