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Author Topic: U/C casting X-rays, TNS 165  (Read 146 times)

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Offline Tim Watson

  • Posts: 43
  • Country: gb
U/C casting X-rays, TNS 165
« on: Wednesday November 22, 2017, 17:27:38 UTC »
Does anyone have a suggestion for a firm that can do this?  Preferably in Southern or Eastern England.

Offline qe45 - (Skytrade)

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Re: U/C casting X-rays, TNS 165
« Reply #1 on: Thursday November 23, 2017, 09:33:38 UTC »
Try Brinkley ??

Offline alant

  • Posts: 19
  • Country: gb
Re: U/C casting X-rays, TNS 165
« Reply #2 on: Friday November 24, 2017, 08:48:26 UTC »
Brinkley are very good.

Offline Tim Watson

  • Posts: 43
  • Country: gb
Re: U/C casting X-rays, TNS 165
« Reply #3 on: Sunday December 03, 2017, 13:24:04 UTC »
Many thanks. Brinkley is an excellent suggestion!
Tim

Offline munkrevival

  • Posts: 16
Re: U/C casting X-rays, TNS 165
« Reply #4 on: Friday December 08, 2017, 18:45:40 UTC »
Just curious, what results have these inspections produced? Are cracks found often? Are certain production years more likely to have had a run of weaker parts than other years?

Offline Nigel Stevens

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  • Country: fr
Re: U/C casting X-rays, TNS 165
« Reply #5 on: Saturday December 09, 2017, 14:02:13 UTC »
Munkrevival, at the risk of starting a polemic, here are my thoughts.  I do not know the extend to which cracking is found. What is not stated in the TNS is why the cracking is important. As far as I know there has never been a situation where the undercarriage leg became loose or fell out, let alone cases caused by casting cracking. The castings may crack but so what. There are lots of aeroplanes flying around with cracks in the structure. In fact if you look at what happens where there are accidents, such as ground loops, where the gear leg takes the impact, the casting destroys the spar, but the gear leg remains firmly attached to the casting.  One wonders therefore about the true value of this TNS, and I'm intentionally phrasing this politely! It is another element that make the aeroplane expensive to maintain. Perhaps that is part of the story.
Nigel

Offline john henderson

  • Posts: 254
  • Country: gb
Re: U/C casting X-rays, TNS 165
« Reply #6 on: Saturday December 09, 2017, 18:21:17 UTC »
We have much bitter experience of this TNS and its consequences. Nigel is quite correct that as the casting is riveted solidly top and bottom and to the spar and the adjoining ribs each side.

The cracks BAC were concerned about were age embrittlement cracking running vertically up and down the tube that connects the two heavy section load spreaders at the top and bottom. apparently you are allowed one or more cracks provided they do not penetrate beyond the tube section. radial cracking is not acceptable. I agree with Nigel that even if it cracks all the way to the top or bottom it ain't going anywhere and neither is the undercarriage leg.  i know of no case of structural failure resulting from cracked castings 

Note the undercarriage leg is only fastened to the top of the casting by a single stud that has a split pinned nut accessible through the cover on top of the wing.  The leg is held in location by a serrated bush that matches a similar bush on the leg (again at the top). Any side or fore and aft loads are taken initially be the top mounting and if the leg deflection is sufficient (hopefully never!), eventually by the lower spreader which note has a diameter about 6mm greater than the leg. This clearance is required to allow the serrated collar on the leg to pass through when the leg is being removed.

Therefore, (my teacher told me not to start a paragraph with therefore!), the loads incurred by the leg are transmitted from the top casting into the upper wing structure and then onwards through the surrounding area and also downwards through the tube section of the casting to the lower spreader and surrounding wing area.

Or aircraft was involved in an accident whereby whilst travelling backwards at slow speed down an embankment (don't ask!), the port leg was stopped by a concrete block. the result was to place an aft load onto the undercarriage, which I am sure was never envisaged at the design stage. This caused a ripple across the top surface of the wing.  The CAA inspector rightly asked for the wing to be stripped, the casting to be removed and inspected and the spar to be checked for damage or distortion. We did this and had the casting Xrayed. there was no change from the previous Xray which had showed a vertical crack approximately 4.5 inches long.

We put the aircraft wing and the aircraft back together (a lengthy and expensive process), including a new tiebar, re wiring, recovering, a bare metal repaint, etc.  After two years and about to apply for the new C of A, we discovered that the Xray was due again even though we had not flown!  This time the Xray disclosed a radial crack running around the top of the casting for about two inches. it reflected exactly the shock load applied by the U/C to the casting when the rearward motion of the aircraft suddenly ceased.  Why it did not show or was not picked up on the previous post accident Xray i have no idea!  This meant stripping the wing again, and replacing the casting with a new one! I won't describe the anguish this caused. It also meant re-fabric for a second time for that wing! Had I had a box of matches and a can of petrol to hand then, the story might have ended there!

The plus side is that the port wing now requires no Xrays. The starboard wing has to be done every few years in accordance with the TNS.  As there has been no propagation since about 1985, like Nigel I question the need to Xray the thing so often or indeed at all.  If the aircraft was being used for flying training with students planting the thing firmly on the ground 20 or 30 times a day it might be different. 

Incidentally, I have several old material U/C castings removed from wings, both port and starboard if anyone is in desperate need.  They are probably cracked but serviceable and don't underestimate the work required to change them, but it can be done.


john h

Offline Dick Gower

  • Posts: 268
  • Country: au
Re: U/C casting X-rays, TNS 165
« Reply #7 on: Wednesday December 13, 2017, 23:08:03 UTC »
That story brings tears to my eyes John!  What tenacity!
I have a copy of the famous March, 1992 BAe letter stating "It would be a correct interpretation that the casting would be serviceable even if split in two".  Happy to copy it to anybody who needs it.

I wonder whether it might be worth an approach to the LAA on this.
Dick Gower
Melbourne,
Australia.

 

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