strut replacement documentation

[astjp2]

Re: strut replacement documentation

Dave, if you were building the 1.5" axle gear I would be interested....but I want good brakes.

[Garry Crookham]

Re: strut replacement documentation

The PMA alone is not enough.

I have to disagree. If the strut has a PMA and is listed in the PMA holders eligibility list then it can be installed as a minor alteration. I believe the Airframes struts require an STC because they are considerably larger than original.

[Guest]

Re: strut replacement documentation

I have to disagree. If the strut has a PMA and is listed in the PMA holders eligibility list then it can be installed as a minor alteration. I believe the Airframes struts require an STC because they are considerably larger than original.

Hi Garry,

I would not have called it an alteration but rather just a repair/replacement.

However regardless of what it is called I agree that it is not major but a minor and is a "logbook" entry.

Dave R.

[Garry Crookham]

Re: strut replacement documentation

There really is no end to the ambiguity and recursion is there?

Dave R

I agree. That makes it hard for an airplane owner to figure all of this out. And yes, 14CFR Part 1 does define "minor repairs and alterations."

[Nefj40]

Re: strut replacement documentation

AA struts are STC'd. The front struts are 4 inches across where the Tcraft struts are 3 inches. The rears are the same as the originals. Weight wise the AA fronts are lighter but the rears are heavier so it come out awash. Weights where done on a certified UPS scale.

[Guest]

Re: strut replacement documentation

I agree. That makes it hard for an airplane owner to figure all of this out. And yes, 14CFR Part 1 does define "minor repairs and alterations."

Yes it does, thanks.

After I wrote my p.s. I looked in part 1 and found the definition so I deleted my wrong p.s.

I suspect but don't know that the PMA for a part needed for an STC does not have an eligibility list or if it does the only thing on the list is the STC.

Dave R

[Guest]

Re: strut replacement documentation

AA struts are STC'd. The front struts are 4 inches across where the Tcraft struts are 3 inches. The rears are the same as the originals. Weight wise the AA fronts are lighter but the rears are heavier so it come out awash. Weights where done on a certified UPS scale.

Hi Dave,

In the '80s during the Dorothy Feris Taylorcraft years they used the ~4" wide struts on the F21s or whatever they were making then.

At that time I lived near an airplane salvage yard and got a lot of Taylorcraft parts for a rebuild aroung 1991.

One of the parts was a front strut and it was ~4" wide, I still have some of it. Was great for making sleeves.

Dave R

[Nefj40]

Re: strut replacement documentation

I wasn't aware that they had used a 4" strut in the past. I think it was already mentioned, but I'm just guessing that AA is using the same strut material for all their struts, Piper etc. One thing that surprised me way all the rust in my fronts even though they past inspection four years ago. The rears seemed empty but you could tip the fronts up and down and hear a ton of rust rattling back and forth.

[PA1195]

Re: strut replacement documentation

One claim I've heard (and that I tend to believe) is that the struts now sold by Airframes were designed first for Pipers. There have been many instances when wing snow loads or strong winds from the rear of the plane have collapsed OEM rear struts. The goal was to offer stronger material (type; thickness; size?) that would better resist compression loads. That technology was then passed to the Taylorcraft parts. I was told this by Lee Budde who designed the originals, sold the Airframes business, and now is a principal in this aviation enterprise: https://www.airforms.biz

Gary

[Guest]

Re: strut replacement documentation

I forgot to mention this part.

While I am sure they used 4" because I saw it I suspect that there is no way to prove it because Taylorcraft Corp. does not and will not share drawings.

So any drawing that was in use in the '80s or '90s is not available for examination.

They may have made just a few planes like that. I recall someone from the factory telling during that time that they had to try different strut cross sections due to lack of availability of the desired type.

At this moment I just remembered why I was in those discussions. A friend flew his Taylorcraft to Texas, he moved there, and ground looped it.

He needed a strut asked me to help find one.

Dave R

[hangarb7]

Re: strut replacement documentation

[original poster]

I was following until I hit this message..."...but there still needs to be approval to install it. The PMA alone is not enough. The airframes struts have a PMA, that is the approval to build them, they also have an STC because they are not the OEM."

Wag Aero struts are tagged with the PMA. But according to this, do I still do a 337 since they are not the OEM? It sounds like some folks did not have a 337 completed.

Jack D

[Guest]

Re: strut replacement documentation

[original poster]

I was following until I hit this message..."...but there still needs to be approval to install it. The PMA alone is not enough. The airframes struts have a PMA, that is the approval to build them, they also have an STC because they are not the OEM."

Wag Aero struts are tagged with the PMA. But according to this, do I still do a 337 since they are not the OEM? It sounds like some folks did not have a 337 completed.

Jack D

Hi Jack,

That statement has been contested by a couple of people.

Read Garry Crookham's posts.

Tell your A&P to talk to the FSDO.

I said this is no place to get direction.

Dave R

[Guest]

Re: strut replacement documentation

Per Garry's post just look at the eligibility list on the pages below. I assume that you got them from WagAero. If not go to the where you got them and do the same.

https://www.wagaero.com/taylorcraft-sealed-front-lift-strut-assembly.html

https://www.wagaero.com/taylorcraft-sealed-rear-lift-strut-assembly.html

No 337, just a log entry. I say repair and replace, Garry says alteration. Either one works and both are log book only, no 337.

Dave R

[3Dreaming]

Re: strut replacement documentation

If you are going to build a part for a airplane to sell, and you are not the manufacturer or building it under a TSO you need a PMA.

The part you build can be approved as a direct replacement part, which just requires a log book entry. The best I can tell Univair and Wag Aero struts are examples of this.

You can also build a part that can be installed under a STC, which requires that you complete a form 337. This is the way Alaska Airframes does their struts.

Both are FAA/PMA approved parts. I am not really sure why Alaska Airframes chose a different route for approval from the other two.

[PA1195]

Re: strut replacement documentation

"You can also build a part that can be installed under a STC, which requires that you complete a form 337. This is the way Alaska Airframes does their struts.
Both are FAA/PMA approved parts. I am not really sure why Alaska Airframes chose a different route for approval from the other two."

Because of the major change (?) from OEM strut dimensions, weight, strength, and possibly material noted previously, perhaps this is why.

"Product" refers to the aircraft.

"Major Change": Change to an aircraft, engine, or propeller which appreciably affects weight, balance, strength, reliability, operational characteristics, airworthiness characteristics, power, noise characteristics, or emissions.

5. Who Needs A PMA?
a. General Requirements. Title 14 of the Code of Federal Regulations
(14 CFR) § 21.303(a) requires any person producing replacement or modification parts for sale for installation on a type-certificated product to get a PMA. A PMA is a combined design and production approval for replacement parts. Also we may use a PMA for the production of modification parts from supplemental type certificates (STC). The prior STC approves the design and installation of these modification parts in products. However, if any replacement part alters a product by introducing a major change, then 14 CFR § 21.113 requires an STC for the approval of these parts. See FAA Order 8110.4, Type Certification, for STC procedures.

Gary