Strut angle conundrum

[Dick Smith]

Re: Strut angle conundrum

Dave, That's not an easy language to learn. I have a nephew that spends a lot of time in China...he speaks English, Mandarin and Spanish. I admire your efforts. Dick

[Dick Smith]

Re: Strut angle conundrum

They did have defective fuselage jig for a period of years.

They discovered it in the early '80s.

It had spent time in a salvage yard prior to that and it was assumed to have been ok before being in the yard. Mrs. Feris told me that.

However it may have be defective even before it got to the yard??

If such a thing had any bearing on this then a stream of serial numbers would have 8 degree struts.

No moon here just rain, I could still be luny though.

Dave R

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Just thinking out loud! There are a lot of F-19's in Alaska. Probably most of them. If perchance some of the Ferris F-19's were built using the jig referenced in the above quote and they built their struts to fit these particular fuselages...and some of these planes wound up in Alaska...and Airframes Alaska happened to obtain a set of these "adapted" struts to reference while building their jig for approved struts...??? What are the chances? Again, just thinking out loud. Dick

[Robert Lees]

Re: Strut angle conundrum

How does the PMA system work in the USA?

Take any old set of struts, build a jig from them, make some parts from that jig, use approved materials + some test data and then sell them with FAA blessing?

Where does the design approval come from?

Just asking,
Rob

[Dick Smith]

Re: Strut angle conundrum

Rob, This is via Wikipedia: https://en.wikipedia.org/wiki/Parts_...turer_Approval

I'm heartened by the fact that my second set of struts and the 10 sets you bought all fit just fine...and that a procedure has been provided to detect a possible range of variation!
My old bird will be 70 years old next year and I'm tickled pink, since the problem found a solution! Looking forward to your swinging through Alaska during one of your Oshkosh forays. Dick

[Guest]

Re: Strut angle conundrum

How does the PMA system work in the USA?

Take any old set of struts, build a jig from them, make some parts from that jig, use approved materials + some test data and then sell them with FAA blessing?

Where does the design approval come from?

Just asking,
Rob

I am aware of cases when a used part was copied (i.e. reverse engineered).

I suspect this particular event occurred in the 60's or 70's and I also suspect that some fabricators are given a much wider and easier path to approval based on history and good ole boy status. It goes like that everywhere.

So I think that your assessment is very nearly correct for some institutions.

I began an approval about 5 years ago for a landing gear frame and gave up when the MIDO guy told me that I needed to get permission from the airplane TC holder. The TC holder was defunct as far as I recall. That is an outrageous requirement that I suspect is only applied to discriminate. I could be wrong.

My opinion is that it is a half-a$$ed system.

I get FAA/PMA parts from well known fabricators that clearly don't fit into the assembly that they are supposed to go in and also do not meet drawing specs and I have to be modify the part to use it.

Also get FAA/PMA parts that are made to the drawing but quality control is so bad that I do 100% inspection and send bad ones back.

Dave R.

[Robert Lees]

Re: Strut angle conundrum

Wikipedia is not a definitive source of course. Any old Tom Dick or Harry can edit it (not that I'm suggesting this is the case here).

Having as little confidence in the FAA oversight of the airworthiness system as I do, I still wonder where the design approval comes from in the case of strut angles? The original drawings and or TCDS would be appropriate, in my book. Or did someone seeking PMA approval make these angles up?

Genuine question.

Rob

[Robert Lees]

Re: Strut angle conundrum

....

I get FAA/PMA parts from well known fabricators that clearly don't fit into the assembly that they are supposed to go in and also do not meet drawing specs and I have to be modify the part to use it. ....

Dave R.

I've had that with PA22 gear legs from Univair for sure, so I sympthasise.

Rob

[Dick Smith]

Re: Strut angle conundrum

Dave, I think you pretty well hit the nail on the head! Dick

[astjp2]

Re: Strut angle conundrum

I would have to follow the same quality controls (drawings, software, calibrations, manufacturing specs, etc) and drug program standards as Boeing or Airbus if I had a PMA for anything that I create, that is why there I don't get one.

[PA1195]

Re: Strut angle conundrum

If a set of struts had the 8* offset the question to be answered is were they factory original installations? Who would know? Who has prints?

Anyway here's pics of four T's taken today. First is my AA left strut, the next two are on F-19's/unknown vintage, and last is on a 1946 BC12D-85. All the planes have a straight rear wing line looking across the fuselage:

[Guest]

Re: Strut angle conundrum

If a set of struts had the 8* offset the question to be answered is were they factory original installations? Who would know? Who has prints?

Anyway here's pics of four T's taken today. First is my AA left strut, the next two are on F-19's/unknown vintage, and last is on a 1946 BC12D-85. All the planes have a straight rear wing line looking across the fuselage:

Hi Gary,

Thanks for the pictures.

They all look like the 2 degree style design don't they?

Dave R

I could be wrong, maybe the black strut is an 8 degree one.

[Guest]

Re: Strut angle conundrum

I would have to follow the same quality controls (drawings, software, calibrations, manufacturing specs, etc) and drug program standards as Boeing or Airbus if I had a PMA for anything that I create, that is why there I don't get one.

Hi Tim,

It is hard to believe that scheme is universally enforced after getting many FAA/PMA parts that don't meet the drawing dimensions of the PMA holder.

Dave R

[PA1195]

Re: Strut angle conundrum

Good eye Dave...yes the black strut #3 did look offset to the rear more than the others. It's an F-19 as is #2. Don't know if they have been replaced previously but it is what it is now. Maybe download the pics and do a measurement from them to approximate the angle?

I talked to Jason at Airframes (1-907-331-4480) as I know someone here that talked about replacing his struts before next summer. Jason said they sell maybe a couple of 8* offset struts a year, but it was rare and in a minority. He didn't offer a % of struts sold. He noted the range in the wing is variable and they have seen from 0-10* offset in the spar attach fitting, and attributed the range to the fitting in the wing being offset, rather than the fuselage. For 0-4* use their 2*; for more use the 8*. One fellow had steel doublers over the spar at the strut fitting and they had a hard time fitting a strut to that particular application.

Gary

[Dick Smith]

Re: Strut angle conundrum

Tribe, I need to make a correction...I noticed when reading through my initial comment (#24) on the strut issue, that I said it was the "lower" ends of the front struts that I "flipped" and bolted together side by side...when looking at the pictures Gary posted, I realized I should have said "Upper" end of the front struts. Sorry about that screwup!! The principle still works, but it was incorrect. I edited the entry and corrected it! Dave, I caused you to use my erroneous words when you quoted me in your comment (#25). Sorry about the error. Dick

[N96337]

Re: Strut angle conundrum

I've had that with PA22 gear legs from Univair for sure, so I sympthasise.

Rob

I've had that with 99.9% of anything from them!
John