Re: TA Bolts...an end?

[tobyp@xxxx]

Les - As I suggested in my previous posting, a survey of the 'fleet' 
would be a grand idea. All we need is some guidance on how to 
accomplish it. As far as your figures are concerned, if the 
percentage of "imperfect" bolts (whatever that means) is as high as 
50%, we have a great deal of "worrying" to do. Keep in mind my 
perspective ... on one car (mine) I had one break completely, and the 
other was significantly bent. And, when we looked at another small 
group of cars, over 1/3 of the bolts were bent. As I mentioned in my 
first post on this subject, I am an engineer on the Boeing 747 
program. Do you remember the crash of a 747 freighter in Amsterdam 
in the early 90's? It was only the second crash of a 747 that was 
attributed to failure of the fuse pins that attach the engine pylons 
to the wing. The fuse pins are fancy bolts that hold together 
critical joints ... that had no reliable structural redundancy. With 
only two catastrophic failures in a fleet of almost 1000 airplanes, 
the Boeing Company undertook a program to redesign the fuse pins and 
pylon attachments, and this program ultimately cost the company over 
$1 Billion. I was the Principal Lead Engineer given the 
responsibility of the new fuse pin design, and my own concept layouts 
for a redesigned pylon attachment were used as the basis for the new 
design that was ultimately implemented. My point is that well over 
$1 Billion was spent over a short period of years because of two 
failures that were attributed to cracking and corrosion of the fuse 
pins, in a joint that was not originally designed with the level of 
fail-safety and structural redundancy that is currently state-of-the-
art. In addition to the people on the List who said that they had 
experienced failures of the TAB, I know of at least one PNDC member 
who also had the misfortune of a total fracture. Luckily, it 
happened at low speed going over a bump. My fractured bolt happened 
during routine inspection, and the lab later confirmed that it was 
90% cracked through when I tried to check the torque on it. It would 
have failed on the trip home from the tech session if I had not 
discovered it when I did. Am I worried about this entire situation? 
Damn right! If you aren't, then I will pray for you.

Toby Peterson VIN 2248
Winged1 


--- In dmcnews@xxxx, Les Huckins <jhuckins@xxxx> wrote:
<snip>
Secondly, actual bolt failure is a very tiny percentage (less than 
5%), of course if yours should be one that fails you immediately go 
to 100%. Final figure is that a very high percentage of bolts are 
not perfect should you inspect them, best guestimate I can get is 30% 
to 50%.
<snip>