Strut Airworthiness Directive (AD) (merged VI)

[flyguy]

Re: Strut Airworthiness Directive (AD) (merged III)

Robert,
Most of my Mil experience was with electronic components and electro-mechanical stuff.
What with being out of the business (retired) my resources are about the same as anyone else.
I suspect it is a specification for a group of lubricating liquids. Maybe listed under NAS?
I'll look/ask around.
DC

[flyguy]

Re: Strut Airworthiness Directive (AD) (merged III)

Re: Mil-C-52: I looked around on the net some and my best guess at this time is that it is a spec that has been superceded several times over, but is still referenced by some manufacturers.
DC

[crispy critter]

Re: Strut Airworthiness Directive (AD) (merged I)

Fellow Taylorcraft owners,

MODERATORS, FEEL FREE TO MOVE THIS THREAD TO THE LOCATION BEST SUITED.

For starters let me introduce myself. I am a Sr. Manufacturing Engineer for the premier high end domestic bicycle manufacturer. The scope of my work involves manipulating a host of tubing materials…. aluminum, 4130 steel, titanium, and of course carbon. We have a very complete and extensive testing department. In questioning some of my fellow engineers, test engineers and QC employees who regularly use ultrasonic and eddy current testing in their job descriptions, they unanimously thought that NEITHER would be an effective method of determining if varying degrees of corrosion existed inside a closed tube structure. Always the skeptic, I set out to prove or disprove the use of Ultrasonic testing as a capable way of testing for strut corrosion. I borrowed our very portable PANAMETRICS MODEL 22 ULTRASONIC THICKNESS GAGE for the weekend. I taught myself the use and calibration of the unit and proceeded to test the LH front strut on my 1938 Taylorcraft Model BF. I set out to neither advocate nor condemn the use of Ultrasonic equipment, only to educate myself in the use and applicability in our strut dilemma. I intentionally set up a series of test parameters that are easily duplicated for STRUTS ON THE AIRCRAFT should results prove useable.

Here are the FACTS relevant to my testing.

-Testing done over the timeframe of 08/18/07 to 08/19/07 at 70degrees and 70% relative humidity.
-Tests completed on what I believe to be an ORIGINAL pre-war Taylorcraft strut. Ellipse dimensions as indicated….major axis 3.000”, minor axis 1.310” (over painted surfaces).
-Panametrics Model 22 unit calibrated per pg. 4.3 of Manual # 910-019B.
Calibration sample .181”/.338”. mild steel.
-Unit set to read in .xxx” (three decimal place…. thousandths)
-Paint thickness sample removed from strut as measured with micrometer…approx .003” as mic’d (3) times in (3) different locations.
-Couplant fluid used was provided by manufacturer.
-Transducer calibration was rechecked and recorded at each row end (54 times total during test)
-(8) individual readings were also taken along the approx neutral axis of the remaining full length of strut at 12” intervals up to the extreme outboard end(wing attach).


I set out by removing the paint from the bottom surface of the lower portion of the LH front strut. I then layed out a grid pattern of approx ½” squares on both the upper (painted) and lower (unpainted) surfaces. Grids were labeled A1 thru G-27. Some areas were not conducive to measurements with the probe such as welds and extreme trailing edges. In total I took 291 readings on this strut using the grid layout as a template.

Preliminary findings indicate extremely consistent metal thickness the entire length of the strut, with the lower 12” averaging .038” +.003/-.002 over 137 readings. I have not run the statistical analysis on my findings yet but have satisfied myself that the Ultrasonic unit is an excellent tool for determining metal thickness on what I believe to be a very intact and un-corroded strut. Findings over the painted surface yield a thickness of .041” +.003/-.001 over 154 readings. These latter reading are consistent with the sample paint thickness of .003”. Another observation that I made during the testing included the following: “ratting derbis” as removed thru the upper wing attach hole amounted to nearly a half teaspoon and consisted almost entirely of weld scale and chips as a result of ( I believe) drilling the upper attach fitting at the point of manufacture.

I would like to duplicate this test on a KNOWN CORRODED strut end. Can someone (Kevin M,, Mike R.?) PLEASE hacksaw off and send me the lower 24” or so of some known defective, corroded struts as soon as possible! Should results of this further testing prove conclusive in identifying internal corrosion, I would advocate same to the FAA . Please reply to forum, e-mail (rockriverrifle “at” hotmail.com) or call me evenings at 920-648-three four six nine to discuss or make suggestions to continue testing.

THIS COULD RESULT IN A VERY USER FRIENDLY, FAIRLY QUICK, ON PLANE TEST METHOD FOR OUR TAYLORCRAFT FLEET.

Sorry for the delayed reply Mike,I've been in the hospital since saturday morning. I'll pick a couple that are bad and send ya....one front and one aft. PM me with your snail mail address or email me at [email protected]

[robbie]

Re: Strut Airworthiness Directive (AD) (merged III)

Kevin

Hope everything is OK with you.

[waltermrich]

Re: Strut Airworthiness Directive (AD) (merged I)

Below is the comment I posted on the docket, after following Rob's instructions. Anyone who wishes to use any part of what I wrote for the purpose of leaving their own comment is free to do so. I strongly agree that it is quite important for all of us to leave a comment.

----------------------

I am an owner/operator of the type of aircraft affected by this AD. I believe that several important and potentially mitigating factors have not been adequately considered during the preparation of this AD.

On the TECHNICAL side, I do not believe there is any greater history of Taylorcraft aircraft being lost due to failure of the wing struts than on any other similar type. The recent tragic loss of a Taylorcraft has been reliably reported as NOT being a failure of the strut. It appears that the AD was based on a Service Bulletin from the TC holder, and this SB was positioned and written with the specific intent to create sales of replacement struts.

The SB bypassed more than one FAA approved method of compliance (such as the Piper strut style punch test, X-ray inspection, Borescope inspection). When the FAA upgraded this SB to an AD, it appears (to those of us "on the street") that these other methods of inspection had been overlooked without cause.

For example, the punch test inspection allowed by the Piper strut AD appears to provide a safe and easy method, and to my knowledge there has been no need for the FAA to amend the Piper AD due to ineffectiveness of this inspection. SEVERAL qualified engineers or inspectors (both in and not in our owner's club) have voiced their opinion that X-ray will give a superior visual depiction of any corrosion inside the strut, yet X-ray is not permitted in this AD.

There is also a simple and valuable option of drilling an inspection hole near the lower end of the strut and performing a visual inspection with a small diameter fiber optic viewing device. This would yield a direct, clear verification of the type and amount of corrosion or moisture inside the strut. Yet this was not permitted as part of the AD.

The AD also does not address the fact that three or four separate sizes, wall thicknesses, and steel alloys were and are approved for struts on this aircraft. Struts are approved with as little as ( I believe) .035 and as much as .049 wall, from 1020 mild steel to 4130, and varying major and minor outside dimensions. As such, an .049 wall 4130 strut of a larger size can obviously tolerate a deeper or worse level of corrosion than a thin wall mild steel strut... but none of this has been addressed in the AD.

I believe I can speak for the vast majority of owners when I say nobody wants to fly with corroded or dangerous struts, but I also believe that a majority of owners believe that 1) this AD was created too hastily and with not enough consideration for acceptable methods of inspection, and 2)the AD was far too hasty because the recent crash was reportedly not a wing strut failure.

On the BUSINESS side, there are also non-technical factors which the FAA should have considered because there is a POSSIBILITY that the FAA has been used as an unwitting tool in what may ultimately be a marketing gimmick.

First, The current Type Certificate holder has a public history of questionable business practices involving his ability to manufacture and sell aircraft or parts for this aircraft. It was made public that (during bankruptcy proceedings that were just a few months before this AD was created) he claimed something to the effect that he was positioned for a large increase in business related to an upcoming Service Bulletin requiring the replacement of hundreds of wing struts. When asked publicly by myself and others in our type club what the statistics were on inflight strut failures on Taylorcrafts, there was no answer from the TC holder.

It was no surprise that the SB issued by "the factory" was little more than an order form for thousands of dollars in new struts. Although not _technically_ germane to this AD issue, the current TC holder is known to have removed airworthy used parts from one customer's aircraft and sold them as new replacement parts to another customer without the knowledge of the aircraft owner... to make a quick profit selling replacement parts. What IS germane to the AD issue is that when the TC holder lobbied the FAA to issue an AD, the FAA may not have taken all the mitigating technical and "business practices" factors into account, and may have not realized that (in the opinion of many Taylorcraft owners)the TC holder was hoping to use the FAA and the AD process as the marketing division for his parts department.

In short, for many of us it appears that "General Motors has convinced the DOT to recall thousands of trucks and force the owners to buy new $1000 transmissions, because the brakes failed on a truck recently and caused an accident"

If I do not have my facts correct on any or all of this please feel free to let me know which facts I have mistaken.

However I do wish to point out that the FAA/NTSB should have taken the time to communicate with the Taylorcraft community at the beginning and during the creation of this AD. The internet would have facilitated a very efficient and instant dialog between all concerned parties in this matter. There is a very active exchange of information and many highly qualified people that participate, as well as a large sampling of Taylorcraft owners and operators that SHOULD have been part of the discussion.

It appears that there are several valid factors that would mitigate this AD to one degree or another. The FAA should reconsider how this AD is written, and allow additional methods of inspection, and re-focus the AD so that it deals with the part of the airframe that DID fail and cause a crash.

William M. Berle
N29544 s/n 2387
Canoga Park, CA

That was an excellent response, please do not give up

[crispy critter]

Re: Strut Airworthiness Directive (AD) (merged III)

Kevin

Hope everything is OK with you.

Thanks Robbie....the Doc says all will be fine but have to be worked on a little bit next week.

[Robert Lees]

Re: Strut Airworthiness Directive (AD) (merged III)

Fellow Taylorcraft owners,
...
...
THIS COULD RESULT IN A VERY USER FRIENDLY, FAIRLY QUICK, ON PLANE TEST METHOD FOR OUR TAYLORCRAFT FLEET.

Mike, have you contacted the FAA on this very important test, or posted it on the DOT website? Could it be feasible to reproduce the test with the FAA witnessing it?

[flyguy]

Re: Strut Airworthiness Directive (AD) (merged III)

For four struts. A days labor at $100/hr. And having to find someone somewhere who has the equipment and a acceptable rating to use it? Then do it every 24 months. Think I'll pass on that one.
DC

[flyguy]

Re: Strut Airworthiness Directive (AD) (merged III)

In reference to the strut fitting: You would think while checking for cracks and bad welding someone would perhaps catch gross corrosion.

47-16-03 TAYLORCRAFT: (Was Mandatory Note 11 of AD-700-1: Mandatory Note 12 of AD-699!@#$!1; and Mandatory Note 13 of AD-696-3.) Applies to All Models BC, BF, and BL Series Aircraft.

Compliance required immediately.

Inspect wing strut attachment fittings on lower fuselage longerons for cracks or evidence of poor weld. If cracks or defects are found, the fitting should be replaced or reinforced.


DC

[barnstmr]

Re: Strut Airworthiness Directive (AD) (merged III)

I was speaking with Andrew McAnaul yesterday, and mentioned the very sound work by Mike Cushway. I called inviting him to participate with me Friday with an NDT specialist in San Antonio as we plan to inspect my struts using various NDT methods. I was pitching to Andrew the case for owners developing alternate criteria for inspecting struts on-wing. In response, he said that the FAA wants the struts to be removed for the inspection, emphasizing this allows the inspector to notice if there are any loose debris inside the struts rattling around (as an indicator of rust). He also said that removal of the strut allows the inspector better access to the wing attach fitting and the FAA wants these inspected also. In fact, he said... "you'll need to cut the fabric away from the wing attach fitting to gain proper access to inspect it."

I have two observations about the FAA on this.

1) I thought this was an odd position to take, since the strut AD makes no mention of the wing attach fitting inspection. We understand that there is a separate AD in the mill for this, but that is a totally separate issue. It seems that Andrew is mixing apples and oranges... strut inspection-vs-attach fitting inspection.

2) Also, the strut AD makes no mention of the "rattle" inspection, either. The mindset of the "rattle" inspection takes all of the technologically advanced NDT methods (eddy current, ultrasonic, radiology) and throws them out the window as if they are not good enough. We must also listen for a rattle? I just don't understand. Either the FAA should adopt these high-tech methods, or not. I do not see the point in speak about requirements over the phone that do not match up to the published requirements in the A.D.

Confused and Frustrated by the FAA once again.

[Robert Lees]

Re: Strut Airworthiness Directive (AD) (merged III)

The "rattle" inspection will not disclose anything if, in the past, the struts have corroded and then been sloshed with oil.

[barnstmr]

Re: Strut Airworthiness Directive (AD) (merged III)

By the way....

Mr McAnaul declined the invite. He is unavailable on Friday.

[Ragwing nut]

Re: Strut Airworthiness Directive (AD) (merged III)

By the way....

Mr McAnaul declined the invite. He is unavailable on Friday.

Of course he isn't going to show up. They don't work that way.

It sounds like he is talking out of both sides of the mouth and doesn't have a clue to really what he is talking about. I guess I won't call him now as it seems it would be almost a garuntee I would get into a arguement over his severe lack of knowledge on the subject of Taylorcrafts

Mike

[Buell Powell]

Re: Strut Airworthiness Directive (AD) (merged III)

I agree with Robert about the rattle being not a true indicator of bad struts. I know of pair of front struts that were presumed to be bad because when turning from end to end you could hear something inside rattleing and detect rust particles. The struts were not used and later cut open close to the lower end and the walls of the struts were perfectly sound. The pieces that were loose were pieces of slag from welding the end fittings on.

[Ragwing nut]

Re: Strut Airworthiness Directive (AD) (merged III)

I agree with Robert about the rattle being not a true indicator of bad struts. I know of pair of front struts that were presumed to be bad because when turning from end to end you could hear something inside rattleing and detect rust particles. The struts were not used and later cut open close to the lower end and the walls of the struts were perfectly sound. The pieces that were loose were pieces of slag from welding the end fittings on.

There is a big difference between slag and rust sounds. Slag has a harder tone as it is a bigger piece of metal and it sounds like a couple pieces inside. Rust sounds more like a bunch of sand in the struts. And as mentioned above, if the struts have been oiled recently, you can throw that test out the window.

Mike