AIRCRAFT QUALITY BOLTS

Excellent point!

Hi - FWTW, I just cut this from a 737 accident report...Engine mounts on Boeing jetliners are a major safety issue. I have always maintained that I would make a poor aircraft designer because my planes would be too heavy to fly. At one time I was a liaison at the Grumman plant at Calverton, Long Island and it was after Grumman had been asked by the Navy to design an F-111 version for them. They built three with each lighter and after the third the Navy said it was still too heavy and Grumman said okay, we are not going to build it any lighter so forget it. So there are aircraft design engineers out there that may think like me, but only somewhat, I agree. I worked for Douglas Aircraft and their philosophy was, build it light, and then beef it up where required later. Thanks,

Bob Lowe

That was Ed Heinemann's philosophy.

There were a few problems with the original A-4 Skyhawk as a result. Mostly systems stuff . . .

These first four aircraft were really challenging. They weighed some 9800# empty and everything seemed to go wrong on test flights. During these early flights test pilots discovered that the speed brakes cracked in a high speed dive, the metal flange alongside the vertical tail peeled back in high speed runs and the slats tended to hang up resulting in violent accelerated stalls. In addition, the oil pressure gage was a simple flip/flop gage, with barber poles the only indication of pump/oil failure.

On the other hand, once the teething problems were ironed out it was one hell of an attack airplane.

It was reported that the wing had an infinite fatigue life - even if flown at full combat weight and max Gs.

This was essentially how the Navy got out of accepting the General Dynamics F-111, except they tidied it all up in "wind over the deck" calculations.

But that is fairly typical of most airplanes and the manufacturer issues a fix. When I worked on DC-3 gun ships in Vietnam there were still Technical Compliance Orders being issued on aircraft that were close to 30 years old.

Hey John B - You mentioned Puff...I use to watch Puff in action just south of DaNang in 67-68...maybe we there at the same time. And TO's..I initiated a few TO's while working for Douglas.

Bob Lowe

Aircraft parts are manufactured and tested to specifications which depend on their use. So 'aircraft quality' only means that they conform to some specification and QA processes are in place to ensure that they do.

An 'aircraft quality' bolt may not be any stronger than a typical hardware store grade one. But you can be fairly certain that they all meet the spec.

I arrived back in the States and the first TV I saw had pictures of

5th Special Forces fighting their Tet '68 offensive about a block from the house I had lived in, in Nha Trang :-)

But actually the Gunny Birds were a horror to maintain. We had one ship that after a couple of missions the mini guns started to "list". The "Tin Benders" lifted a panel in the floor and the formers and brackets that supported the floor were corroded and failing. We ripped the floor out and re-built it but that bird was out for nearly a month. I have no idea where the A.F. got those things but one, I checked, was as old as I was :-)

The squadron's brag was that if we got there before Charley had gotten through the wire then it was a done deal - we never lost a camp or a fort. I used to eat in the 5th S.F. NCO mess as a guest based on that.

In the airplane fixing business "Aircraft Quality" is a meaningless term, or at least I never saw the term used in more then 20 years of working on the things. What would be specified was something like Bolt, AN 64-23, fiber self locking nut, AN 23-24, washer, AN

23-405.\, or maybe Bolt, internal wrenching, P.N. 23-12345.

Yes, agreed. That 'Aircraft Quality' statement always equates to some snake oil marketer peddling off crap.

Erik

I live in the Seattle area where everybody either works at, worked at, or knows someone who works at Boeing. "Aircraft Quality" is used around here a lot. For example, I was in a local bike shop once and they had a fancy new frame hanging from the ceiling that was "Aircraft Quality T6" So I asked the guy which alloy the frame was made from and he tells me "It says right there, T6" . I told him that T6 was a temper designation, not an alloy. He said then that he knew aluminum and that T6 was an aircraft quality aluminum alloy. Then he said that they also had cranks made from "Billet Alloy". Which was also "Aircraft Quality". I just bought the light I went in for and left. Eric

You could have argued that "T-6" was actually a marine alloy as it is, so often, used to designate the masts and spars of sail boats :-) And, I've always wondered about the "billet" designation. The advert writer could have equally used "ingot" which has, sort of, an association with gold bars :-)

I assumed that 'billet' meant the part had been machined from bar stock instead of stamped or forged.

jsw

You need to refresh your memory on aluminum alloys. As I remember all the marine alloys are five thousand and something.

Dan

Thanks for all of the info and where to find more...I worked all of my life in the aircraft field but never with nuts and bolts...I was always in the electronics part. We did get retrofit 'kits' sometimes but someone else made them up. The first plane I flew in was a Tri Motored Ford and the last was a Stearman PT-17 with 70 years in between. My first operation squadron in the Air Force was made up of B-17's and C-47's and after that since 66 I worked for NAVAIR and NAESU, sorry for the acronyms. I don't know about the proper use of Billet 'designation' but I do know when I worked at the Douglas, El Segundo Plant, truck loads of aluminum alloy 'billets' would come in every day. I just looked in a reference book and it says, under Aluminum Types: Class T6, Solution heat-treated and then artificially aged. Common class. Now I have to find out what is 'artificially aged'. Is this some kind of freezing and warming process?

But they will be used in the T6 condition - which is about the hardest AND toughest an aluminum alloy can be - Solution Heat trested and artificially aged..

But spars are most often 6061 or 6063. Which just goes to show that "marine," "aircraft," and "surgical" don't have much meaning when it comes to materials.

But not applicable to the 5xxx alloys, which are strengthened by cold working, not heat treating.

Haven't read all this yet. So maybe helpful, maybe not. But it ought to keep you out of trouble for a while... :)