How is Max Structural Cruising Speed determined?

TripleSticks

TripleSticks

Well-Known Member
I've been looking for a technical answer for the question "How is Max Structural Cruising Speed determined?" for just a few minutes because I want to put it in to a flight plan that I am developing (getting ready to take my initial cfi exam). I feel like I should know the answer to this question but either it's something that was never discussed during training or all the studying I have been doing has clouded my head with so much junk that I forgot.

Anyway.... Any help would be appreciated.

Thanks,
John
 
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You know... just like they test the max weight for bridges... Keep driving a heavier and heavier truck over it till it breaks, then build a new one the same way.

For the airplane, they just fly faster and faster until it breaks, then build a new one...
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(obviously kidding
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Really , I think it's just an engineering calculation with too many omegas and phis for me to really know.
 
Yeah, it pretty much has to do with load factors, tensile strength, torsion, type of materials used, etc. You end up with a chart that has load factors and airspeeds on it.
 
I believe small aircraft are certified under FAR part 23 and Transport Category aircraft are certified under part 25. If you look on the FAA website, you can find the information you are looking for.

Many of the speeds used for certification are determined using the V-G diagram. You have probably seen these if you have read about Maneuvering speed. I think that Max structural cruising speed is also determined using this diagram, by subjecting the aircraft to vertical gust of a certain intensity (it may be 30 feet per second). Where the line for the acceleration caused by the gust crosses the top or the bottom of the 'envelope' is what determines max structural cruising speed. If you read part 23 they will no doubt have lots of math equations for this as well.
 
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