FAA Failure #119

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PagoBay

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Mike Busch / Savvy Aviation discusses a 15 year history of fatal accidents and emergency landings attributable to an oil filter gasket.
May not apply to your airplane, but may apply to someone you know.

For those who are short of time, an key paragraph....
It turns out that the NTSB has been bugging the FAA for 18 months to address this problem, but to date the FAA has been non-responsive. Finally, on November 30, 2020, the NTSB issued a formal Safety Recommendation asking the FAA to issue an Airworthiness Directive (AD) against these F&M/Stratus/Tempest oil filter adapters requiring repetitive inspections of these adapters to ensure that they are properly installed, have not come loose from vibration, and have not chewed up their gaskets. The NTSB also issued a one-page NTSB Advisory to bring this problem to the attention of aircraft owners and their mechanics. There are five different variations of the F&M/Stratus/Tempest adapter, designed to retrofit full-flow spin-on oil filters for just about every model of Continental engine that came from the factory with an oil pressure screen rather than an oil filter.

 

Turd Ferguson

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There have been 11 GA accidents since 2004 due to aftermarket oil filter adapters (that's 11 accidents over 16 yrs). Yes, all hands on deck! Lets get out the fire trucks and get this ember quenched out ! !
This is majoring in minutia.
 

Mad MAC

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There have been 11 GA accidents since 2004 due to aftermarket oil filter adapters (that's 11 accidents over 16 yrs).
As always that's just the accidents that got reported.

In the unlikely event they have sold 10,000 units that's a 1 in 1000 failure rate which is pretty excessive.

As always how bad is too bad is the difficult bit, i know one mod that got pulled after 2 failures, unfortunately there were only 3 examples in service.
 

Victor Bravo

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I have this filter adapter (F&M, O-300 / Cessna 172) and I know exactly what they're talking about. It's NOT the gasket for the oil filter, it's the gasket between the adapter and the original oil screen housing on the back of the engine. Tightening the spin-on filter very easily causes the entire unit to also rotate on the axis of the main engine attachment, and this gasket is what gets loose and starts leaking.

It takes a dedicated careful effort to loosen/tighten the spin-on filter without moving the entire unit's "clock" position on the engine.
 

Turd Ferguson

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As always that's just the accidents that got reported.

In the unlikely event they have sold 10,000 units that's a 1 in 1000 failure rate which is pretty excessive.
All malfunctions and defects related to this aeronautical product as discovered in the field should have been reported, not just those that result in accidents. It's required by FARs. That 1 in a 1000 failure rate should be verifiable with info from the database.

At the end of the day, the NTSB is not the FAA's boss. It's nice that they make all these recommendations as some of them are useful but the overall level of safety the NTSB would like to see would wipe out most of aviation. The FAA accepts that various aviation activities have varying levels of risk -- see FAA Safety Continuum.
 

Dan Thomas

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It should get the AD. The FAA issued an AD against a similar Cessna-designed adapter for the 470s and 520s used in their airplanes. The locknut could come loose and then the vibration would get the whole thing moving and it would tear up the threads. Cessna Aircraft Company Engine Oil Filter Adapter

The original screens were small, light, short affairs that the threads were designed to retain quite adequately. Then supposedly bright people came up with a much bigger, heavier, overhung load that causes lots of trouble, including any loosening created when the filter is removed or installed. What could possibly go wrong??

One of the hassles with the adapters addressed in this thread is the use of a gasket. Like so much else in aviation, gaskets (including those silly copper crush gaskets) are still being used, even on brand-new engines, while all the rest of transportation industries use O-rings of various compositions to seal stuff far more effectively. Done it for decades. Only in the last 20 years or so have I seen modern synthetic O-rings apearing in fuel systems on new airplanes. Still using Buna O-rings (WWII stuff) in landing gear oleos and a lot of other places.

For my money I would get a firewall-mounted remote oil filter. The hoses to the adapter on the engine don't stress the original oil filter housing so much that way. AIRWOLF REMOTE MOUNTED OIL FILTERS - CONTINENTAL | Aircraft Spruce Canada Shoot, if it was for a homebuilt, I would just machine my own. I would also incorporate a relief valve in it to allow bypass when the oil in the filter and hoses is really thick when starting up in the cold weather. Or install a Vernatherm in it. Much better.
 
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Wanttaja

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At the end of the day, the NTSB is not the FAA's boss.
And in my opinion, this is a good thing.

Almost ten years ago, the NTSB performed an in-depth study of homebuilt aircraft accidents. The study itself was excellent, but many of us would have objected if the FAA tried to implement some of the recommendations.

- Applicants for airworthiness certificates would be required to document fuel testing, and submit a test report to the FAA for approval.
- Applicants have to develop a formal plan for testing, and submit it to the FAA for approval
- Applicants would have to develop an aircraft flight manual, and submit it to the FAA for approval
- FAA would be required to review and re-approve aircraft operating limitations every time the aircraft is registered or re-registered (e.g., every three years)

Note that none of the activities above are bad... fuel system testing IS a good idea, as are developing a plan for flight testing and for an aircraft flight manual. But the NTSB wanted to insert the FAA into the process by requiring the builder generate formal documents and require FAA approval prior to issuing an airworthiness certificate. This would have been a major change in the homebuilt world.

Ron Wanttaja
 

4redwings

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Mike Busch knows his stuff. A bad design is a bad design regardless of anyone's opinion of the NTSB. And of course there were more incidents than those that were reported. The OP was right to bring it to everyone's attention, and for that, I thank him.
 

Riggerrob

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The company that builds the adapter has instructions for installing and maintaining the product and even put it in a service bulletin. Unfortunately, the prevalent attitude in GA is "if it's not an AD we don't have to comply" so the NTSB wants it to become an AD. Sometimes you can be your own worst enemy.
Agreed!
I have heard FAA certified parachute riggers say that "no AD means that I don't have to do that inspection." Then I remind them that the FAA quit issuing AD for parachutes well back in the last century.
I also remind parachute riggers that they are still legally bound to follow the manufacturers' instructions.
 

Victor Bravo

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Agreed!
I have heard FAA certified parachute riggers say that "no AD means that I don't have to do that inspection." Then I remind them that the FAA quit issuing AD for parachutes well back in the last century.
I also remind parachute riggers that they are still legally bound to follow the manufacturers' instructions.
Not to mention that they have people's lives in their hands, and should do everything at as high a level of quality as they can.
 

PagoBay

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Mike Busch was there already. Here is the concluding paragraph of the article.
Although frequent inspection—hopefully mandated by an AD—increases the chances of catching this problem before it becomes catastrophic, we think these adapters are fundamentally flawed. While we definitely recommend retrofitting an oil filter to any piston aircraft engine not so equipped, we would feel a lot more comfortable with a remote-mounted filter (e.g., the Airwolf) that has the filter firmly secured to the firewall and not subject to engine vibration.
 

Dan Thomas

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Mike Busch was there already. Here is the concluding paragraph of the article.
Although frequent inspection—hopefully mandated by an AD—increases the chances of catching this problem before it becomes catastrophic, we think these adapters are fundamentally flawed. While we definitely recommend retrofitting an oil filter to any piston aircraft engine not so equipped, we would feel a lot more comfortable with a remote-mounted filter (e.g., the Airwolf) that has the filter firmly secured to the firewall and not subject to engine vibration.
One of the more sketchy setups, in my view, was the bolt-on adapter for the O-200. This one:

1607616203807.png

1607616231795.png

It's installed on the oil cooler pad. The oil cooler looked like this:

1607616504221.png

Now, oil coolers are light, made of thin metal that transfers heat quickly, and they don't contain much oil. An aircraft spin-on filter isn't light (it's made of thicker steel than an auto filter, and has denser media) and contains a lot of oil, and this adapter sticks it out quite a ways. Vibration is going to stress that little mounting. It's not just the mounting tabs; it's the threads in the aluminum case that have to take the constant yanking every time the engine fires. I think the load on the mounting will be considerably higher than the cooler would impose.

But that's just an eyeball-engineering opinion. And that opinion comes about from some real-world problems. A few years ago an AD was issued on an adapter fitting installed on the IO-550K engine. I remember looking at that thing (in a Cessna Corvalis) and wondering when vibration would break the little nipple supporting all that stuff--the fitting, some hoses (turbo oil) and an oil pressure switch. I didn't have long to wait. One airplane (a Cirrus) did lose all its oil after that thing failed, and the FAA issued an AD on the heels of a critical service bulletin issued by Continental. The stuff looks like this:

1607618115070.png

You're looking at it from the rear and to the left. The axis of the fitting is forward/aft. It fits under the oil cooler, a good distance from the crankshaft axis, so it gets shaken up and down every time the engine fires. This is the result:

Cirrus SR22T, N857SW, registered to WG Aviation LLC and operated by a private individual: Accident occurred November 03, 2015 near Drake Field Airport (KFYV), Fayetteville, Washington County, Arkansas

1607618636776.png
 
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Victor Bravo

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BUT, the other side of the coin is that (even Mr. Busch would agree) every place where there is a connection, a fastener, a fitting, a hose, etc. etc. is a place where something can leak, crack, or start working it's way loose.

Steel-braid oil hoses that are vibrating back and forth have been known to saw into an engine mount, or the movement puts put cyclical loads on something, etc.

So adding a remote filter, and the associated three feet of hose, 8 or 16 AN fluid fitting parts, the mounting bracketry, etc. also comes with its own set of risks.

I'm not saying a remote filter is unsafe at all, I'm simply saying that a remote filter also comes with a different set of risks that has to be considered.
 

Dan Thomas

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BUT, the other side of the coin is that (even Mr. Busch would agree) every place where there is a connection, a fastener, a fitting, a hose, etc. etc. is a place where something can leak, crack, or start working it's way loose.

Steel-braid oil hoses that are vibrating back and forth have been known to saw into an engine mount, or the movement puts put cyclical loads on something, etc.

So adding a remote filter, and the associated three feet of hose, 8 or 16 AN fluid fitting parts, the mounting bracketry, etc. also comes with its own set of risks.

I'm not saying a remote filter is unsafe at all, I'm simply saying that a remote filter also comes with a different set of risks that has to be considered.
That effect is well-known. Oil coolers are often firewall-mounted, with sizeable hoses (#8) running to them. The fuel line in many airplanes is a half-inch medium pressure steel braid hose, same stuff as oil lines, and it can yank at the fuel strainer. One has to provide enough hose, and enough curl or bend in the hose, to allow the engine to vibrate and move without stressing the firewall stuff. I have found hoses--fuel hoses, especially, made too short. Some mechanics will make hoses and disregard either the length of the original or the part number of the original, which often has the length as part of the number. I've also found aluminum fittings used where steel was specified by the manufacturer, and that presents another serious risk. Aluminum fittings will fatigue and fail far sooner than steel.

I've had owners exclaim at the amount of movement of a Lycoming on its Dynafocal mounts when I've started or stopped it with the cowl off for a leak check. An amazing amount of movement.
 

Dan Thomas

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So when you change the filter who's not inspecting the **** thing? Duh. . . Can't regulate lazy. What a nothing burger.
But it's common. The Cessna oil filter adapter AD specifies that torque seal paint be applied to the locknut, and that seal is to be inspected at every oil change. I've found those things without the torque seal, meaning that the last several guys that changed the oil and filter paid absolutely no attention to the AD or the inspection.
 
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