Metal fatigue checks

Here’s examples of the old way. Comet 1 fuselages at Farnborough C1970 by the water tanks.

If you look at some of the early 747 and 737 you will see dirty great bands rivetted down the side of the fuselages with cut outs for the windows, this was a scheme added to high houred ( pressure cycles) fuselages to alleviate cracking around windows.

see as an example one of the 737 ad’s ( Airworthines Directives)

http://ad.easa.europa.eu/ad/US-2011-08-51

This one was a biggie, during repainting in the past, tools had been used on 737 skins when applying or removing decals and paint that scored the metal, which can lead to fatique cracking
several 737’s I know of were written off and scrapped because of it!!

again see

http://ad.easa.europa.eu/ad/US-2010-26-06

just open the PDF to read them, for more issued by EASA see

http://ad.easa.europa.eu/search/simple/result/

Again as said they come from experience and feedback to the manufacurer from failures in service or accidents, the old HS125 we used to do a complete xray of the wings, it can show up corrosion etc, BBMF Spits have a similar procedure I believe.

This is another URL which claims a wider and more complex customer base

This is another URL which claims a wider and more complex customer base and product and service range

http://www.ihsesdu.com/cgi-bin/ps.pl?sess=unlicensed_1110807060546gnv&t=gen&p=home&fwd_t=null&fwd_p=null

Take a look at the following site, it gives a short description of the different inspection techniques available!

http://www.aircraftndt.com/

Having watched a documentary on the DH Comet it set me thinking how modern airliners are monitored for metal fatigue…..is it based on destructive testing at the prototype stage or some sort of constant monitoring…..?:confused:

Back in the 60’s when I was an apprentice, I got talking to a chap who was
putting a big water tank together in a school.
Turned out that he worked on the tank they tested the Comet in.

Watching a programme on Discovery a few years ago, they showed the wings of the 777 being tested to destruction.
They also do extensive testing on the B-52s. Taking the wingtips up and down 15 – 20ft then doing X-Rays.

Indeed. It certainly didn’t happen to the Boeing 707 or Tu-104 when they also entered service in the 1950s.

What’s sad is the Comet disasters didn’t “have” to happen.
Everything that would have prevented it was already known.

There were many works dealing with the design of pressure vessels dating back to the 1800s.

Great info JT442, thanks mate….I take it that The comet DID revolutionise the aircraft industry, but for very different reasons than was predicted 🙁

Agreed, both. Non destructive testing requirements are often determined by the results of the destructive testing and some rather large-brained individuals who can calculate the average life-span of a particular metallic structure due to its properties…

NDT in the field ranges from basic visual checks with a torch and a mk.1 eyeball, to Eddy Current, dye penetrant, even x-rays.

Boeing 737-500’s have a problem with cracking in the wing roots apparently, and this would have been picked up initially by eye, recorded, monitored, followed by fleet inspections and a fleet wide recommendation to inspect at certain intervals.

Just remember that the Comet accidents highlighted key things about metal fatigue that were not known at the time….

For the constant monitering is visual combined with NDT checks at certain intervals….if so how is the NDT carried out….I have seen NDT on the Vulcan using a type of X ray, is it similar to that ?

Both.