Natit

Obviously aircraft have a certain amount of hours left remaining on say an engine or prop before an overhaul, but is there a set minimum before these are replaced or does it change for aircraft type and engine type etc?

Also, is there a maximum no. of hours an airframe can have before its deemed unusuable?

Sorry if these questions are really obvious, but I'm not really up to speed on maintenance procedures, especially when it comes to these types of things.

Thanks in advance

N

scrambler

The quick answer is Yes.

Engines and Props have overhaul times usually set by the manufacturer of the component. These may be changed by the use they are subjected to also. An example may be an engine fitted to an aerobatic aircraft has a reduced time due to the potential increased stresses over its life.

Other components may have reduced time due to regulators such as the R22 rotor blades.

Airframes and other components may be time limited

Torres

Your first question is difficult to understand. I think you are referring to the component TBO (Time Between Overhaul) period? If the TBO on an engine or prop is (for example) 2,000 hours, then the engine or prop must be overhauled prior to, by, or at 2,000 hours TIS (Time In Service). Similarly, other components may be life restricted by either hours or cycles; e.g. the starter/generator, fuel nozzels, hot sections etc on certain PT6 turbines are life limited.

I am not aware of a maximum number of hours at which an airframe (in total) is "unserviceable". However, components of an airframe may be "lifed" - e.g. a maximum number of pressurisation cycles on a Beech King Air (after which the fuselage requires modification or retiring), or maximum number of hours on an Islander wing (think it is 26,000 hours?). Cessna 400 series wings were limited to 8,500 hours (again from memory) before the spar cap required replacement (Australia only).

Looking at Scramblers post, reminds me that an R22 helicopter is "lifed" at 2,000 hours, after which all components require overhaul.

Natit

Thanks for your answer scrambler.

Also, my apologies Torres, I was indeed referring to the TBO times that you see published with aircraft sales etc.. Thanks for your post also.

N

P.S Editted - I answered my own question. Thanks guys