DOCUMENTATION

EMAIL LISTS

EVENTS

FORMATION & FAST

FORMS

KEEP'EM FLYIN!

Background Info

Memos to Members

LINKS

MERCHANDISE

How to Order

MEMBERSHIP

Address Change

Application

Information

MEMBERS ONLY

Help with Login

Information

Login

Member Database

Memos to Members

MENTOR MONITOR

PHOTOS

RESOURCES

T-34 ASSOCIATION

Board of Directors

T-34 MENTOR

For Sale

S/N Lists & Webpages

Tail Cracks

Cracks have been found in tail spars on four T-34s.

G-264

Harold Wilson’s T-34A (S/N 264, N7132C) was one with a crack indication found in the RH Horizontal Spar on 5/19/05 in Houston at his shop. The indication was very small and located on the forward spar, lower fastener row, most inboard fastener. He had another Horizontal Stabilizer available which passed the inspection and was installed. He will be sending the unit with the anomaly to Tim Roehl at GAMI for further study. It was unclear whether it was even a crack, but maybe some anomaly left as a result of the bushings being pressed in during original manufacture. These holes are not highly loaded and would not be the ones expected to crack from fatigue loading. The horizontal did have the 0.100 reinforcements on the flanges. (A "thin" spar. See this page for details.)

G-30

The crack indication on Craig Muller’s T-34A (S/N G-30, N134BS) was larger: 3/16-1/4” emanating from the RH aft spar, lower row, second from the most inboard on the aft face. This one did not have the 0.100 reinforcements on the flanges. (A "light" spar. See this page for details.)
 

G-779

The crack indication on Robert Irwin’s T-34A (S/N G-779, N4002F) was 0.03 - 0.06 inches long emanating from the RH forward spar, lower row, most inboard fastener, aft face. This one did have the 0.100 reinforcements on the flanges. 

G-37

The tail of Dan Thomas' T-34A, G-37, has what appears to be a crack. Looking at the pictures below it is pretty easy to say "crack" and move on. Since this is the first tail to be found with an "inclusion" since the "Get'em Flyin'" AMOC was released, a lot of people have been taking a closer look at it.

Click on any picture to see a blow up of that shot.

This left horizontal stabilizer is not from G-37. I put it here to give you an idea of what we are looking at on G-37.

Here is a close-up of the front spar on the above left horizontal stab (again, not from G-37). I have put a line where the crack is located -- follow the red arrow. (Oops. No blow up of this picture.)

Here is a close up of the crack on G-37.

Here is another view of the same crack. Up is down in this case.

Dan Thomas reports:

The bad news is that we found a crack in the forward spar of the left hand horizontal stabilizer. The crack is in the lower, most outboard fastener hole. It is approximately a quarter inch long. It is a vertical crack at the 6 o'clock position.
 
Dave Miller invited me to participate in the inspection and I used the probe around this hole. I found what I thought to be a scratch. When Larry inspected it he said, "That's a crack." To double check, he put dye penetrant on it. The dye penetrant did not show a crack. At that point we thought we might have a deep scratch. We got another mechanic to attempt to take out the scratch by burnishing the surface. It didn't come out and only made the crack more evident on the eddy current test and under magnification. It's a crack.
 
My airplane has NOT been abused since I bought it on October 1, 1997. I seriously doubt that the previous owner, who flew it about 50 hours a year for 17 years abused it either.
 
George Braly tells me that the crack we found is in the logical place for a crack if one is to occur. It is in a different location, however, than the cracks found on N141SW.
 
...Something very important about my left horizontal stabilizer. It does not have the 0.100 inch stiffener in the C channel in either the front or rear spar. My left horizontal stabilizer is one of the so called "light" spars. (See this page for a description of the three types of tails.)
 
Dave is shipping the horizontal stabilizer to Jud so he can replace the spar and have Stan Ray look at the crack. We want to make very sure this is not a false positive. I don't think it is and neither does Dave Miller. Larry Schultz, a very experienced NDT inspector, is sure it is a crack.
 
I believe there are four important points in the above information: (1) there is a crack in a non-air combat T-34 horizontal stabilizer, (2) that stabilizer has an unknown number of hours on it, (3) a dye penetrant test does not show the crack, and (4) it was found in a “light” spar without doubler plates.
 

--

After Stan Ray had a look at the spar he wrote to Jud Nogle:

Jud

I have conducted several tests on this spar at no expense to the T-34 association. The following are the tests and observations.

I have conducted a radiographic (x-ray) test of the spar per Mil-453C with a cross reference of Mil-1907 as an acceptance standard. I have used the most sensitive film available which is a Agfa D-2 with a source to film distance of 18 in. and exposure factor of 5 minutes. I have processed the film using acceptable and approved techniques. The film was read under approved conditions and the results showed no linear inclusions.

This spar also was subjected to an Ultrasonics inspection using ASTM 317 as a guide. The instrument that was used was a Nova 810 with a 15 Mhz transducer, this machine has a calibration due date of 30 April 2006.This inspection showed no relevant erosion to the spar through out this spar.

I have also conducted a Liquid Penetrant inspection of this spar and it was conducted per T-34 Spar Corp Inspection procedure 3506. This indication showed as a dark line when viewed under a 10x glass and a black light during the process of PT. This is not the proper footprint of a crack. I found no relevant indications

I have also conducted an Eddy current inspection per T-34 Spar Corp Inspection Procedure TSC 3505 and S&S Testing Eddy Current Procedures and found the following. As the eddy current probe was moved over the suspected inclusion area the signal made a loop and the trace line stopped half the way back down the trace. The speed at which the probe was moved over the inclusion area was increased and there was an indication that resembled a crack indication.   Conclusion: I am not prepared at this time to either agree or disagree with the findings of my colleagues. I cannot approve or disapprove their findings.

J. Stanley Ray. S&S Testing NDT Level III  

Dan concludes with the following:

If that is not a superior effort to get at the truth, I don’t know what is. We will take one more step with the spar. It is a destructive test that will slowly dissect the metal to see what the defect really is. Whether the defect is a metallurgical anomaly or a crack, that spar will never be put on another airplane.