Certification Basis -Thrust Reverser Structure

[MNLiaison]

I reviewed an STC for a thrust reverser that finds compliance to Federal Avaiation Regulations Part 33 "Airworthiness Standards: Aircraft Engines" with the original type certifcate being the engine.

Is this typical for the thrust reverser to be certified to Part 33?

I always assumed it was certified to Part 25 but it appears that I am incorrect.

Any insight into this would be greatly appreciated.

 

[rb1957]

i'd think it would be reasonable to consider a thrust reverser to be part of the engine rather than the airframe.

refer subpart F, para 33.97 "Thrust Reversers", but this says pretty much squat.

i'd've thought that they would need a TSO ...

 

[rb1957]

a quick scan couldn't find a TSO (surprising since they have TSOs for the pilot's coffee cup), and in FAR25 found only 25.933 (and 25.934 which points to 33.97) ...

 

[SWComposites]

I think TRs and the rest of the nacelles are certified to the structural requirements of Part 25. Perhaps you should ask the cognizant DER or FAA ACO.

 

[bf109g]

It might be that this engine was certified with the thrust reverser as part of the complete engine design. SWComposites is correct in saying that the nacelles are typically certified with the aircraft structure.

STC's are never known to be in error, right?

 

[MNLiaison]

Thanks to everyone for the input. This could be a "special" case for this engine but I would have thought that certification is a standard procedure and you just can't pick which FAR to show compliance to. This will definitely require some more research to fully appreciate the difference.

Thanks again.

 

[rb1957]

isn't the biggest thing about a thrust reverser design is it's interaction with the rest of the airplane (in operation how does the deflected exhaust affect the flight control surfaces, systems to make the TR inoperative, ...). so that would suggest FAR25.

but maybe the STC in question is only a minor change to the TR already installed on the plane (rather than installing one) ? which would suggest FAR33 ??

 

[MNLiaison]

Found out it's duel certified, Part 25 and Part 33...defies logic doesn't it! I love the ACO's and their uniform policy.

 

[RPstress]

Interesting. One we did recently (about six or seven years ago) was just to Part 25. Presumably for what we were doing that enveloped Part 33.