Allowable, Scratches, Nicks & Dents
Allowable, Scratches, Nicks & Dents
(OP)
I need to specify the allowable damage for a new airframe. These are usually in terms of scratches, nicks and dents in terms of length (or diameter), depth of the damage type.
I'd like some advice on how one goes about setting the parameters for this kind of damage in the Structural Repair Manual.
I look forward to your input.
Thank you in advance.
I'd like some advice on how one goes about setting the parameters for this kind of damage in the Structural Repair Manual.
I look forward to your input.
Thank you in advance.





RE: Allowable, Scratches, Nicks & Dents
RE: Allowable, Scratches, Nicks & Dents
RE: Allowable, Scratches, Nicks & Dents
RE: Allowable, Scratches, Nicks & Dents
Allowable damage is where when a certain scratch is blended and calculated for the new net cross section stress and can still withhold its strength (including fatigue) up to the required life of the aircraft.
Fly-by would be when no possibility of immediate repair can be done. Therefore a much worst damage compared to allowable damage. But for fly-by, the a/c need not be checked for fatigue life since the a/c cannot be flown again without proper repair. Therefore cannot be used for preexisting (fly-by) damage.
Try FAR 25. It has some requirements for structural repairs.
RE: Allowable, Scratches, Nicks & Dents
RE: Allowable, Scratches, Nicks & Dents
RE: Allowable, Scratches, Nicks & Dents
I'm amazed that this topic is still receiving attention after all this time. In 2001 I was working in a foreign country and had to establish some "unique" criteria for that particular, new airframe. These criteria were for inclusion in the SRM. I had to establish such criteria without launching into a huge DT analysis program similar to the one US reference SRM I had. The crux of the issue in most of these SRMs is: just how severe can such "minor" damage be and merely be "dressed out" without reinforcement and/or repair action being taken.
So, Highness, yes it was for a new all-metal aircraft in the military trainer class. I had seen how other high performance aircraft manufacturers had determined their criteria, which seemed like an overkill for the program I was working on.
I was hoping to receive some advice from someone who had done such work on airframes before the problem was "beaten to death" using massive amounts of FE and DT analyis on every region of the airframe. Believe it or not there was life before computerized structural analysis came along, and most companies provided very good guidelines for their airframes.
Regards,
Ed.
RE: Allowable, Scratches, Nicks & Dents
Was just interested as I browsed this interesting site with 'loads' of aircraft structural data. I'm an aircraft structural engineer at thé major european airline. Before I worked with Boeing in Seattle and Fokker in Amsterdam on ..... SRM's as a structural repair engineer. Hence my interest. I've worked on allowable damage and repair sections of Fokker 28/70/100 SRM's and Boeing 737NG SRM's so I'm familiar with specifying (and designing) allowable damage and repair data for new as well as in-service aircraft, working closely together with the manufacturer's engineering departments and representatives of the authorities for approval of these data.
Regards,
Pim aka Highness
Aircraft Structures Engineer
RE: Allowable, Scratches, Nicks & Dents
RE: Allowable, Scratches, Nicks & Dents
I am working in calculations of allowable damages in a curved panel (fuselage skin) for SRM. The problem is that I don't know how evaluate the damage/hole in the post-buckling effect. Does anybody have an idea?
Thanks in advance