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Aeroplane Mass Ratio - Gust Envelope

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Aeroplane Mass Ratio - Gust Envelope

Old 9th Apr 2021, 03:20
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Aeroplane Mass Ratio - Gust Envelope

Dear fellow PPRuNers,

Would someone be able to give me a leg up regarding the aeroplane mass ratio μ in CS 25.335 (d)(1) (see below)?

K_g = 0.88 μ / (5.3 + μ)

I fully understand that the gust load factor is based on a notional sharp-edged gust, and therefore needs correction for a more realistically shaped gust and load alleviation from the tailplane. Unfortunately, I can't get my head around the rationale behind μ, and the textbooks usually just mention K_g without further explanation.

Any hint would be greatly appreciated.

Last edited by hvogt; 9th Apr 2021 at 04:48.
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Old 9th Apr 2021, 06:53
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This may help https://apps.dtic.mil/dtic/tr/fulltext/u2/a380634.pdf
NACA TECHNICAL NOTE 1976 SUMMARY OF INFORMATION RELATING TO GUST LOADS ON AIRPLANES
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Old 9th Apr 2021, 07:31
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Originally Posted by David J Pilkington
This may help https://apps.dtic.mil/dtic/tr/fulltext/u2/a380634.pdf
NACA TECHNICAL NOTE 1976 SUMMARY OF INFORMATION RELATING TO GUST LOADS ON AIRPLANES
Thank you for the link.
Saved on my phone for a future brain aneurysm.

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Old 10th Apr 2021, 08:36
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Originally Posted by David J Pilkington
This may help https://apps.dtic.mil/dtic/tr/fulltext/u2/a380634.pdf
NACA TECHNICAL NOTE 1976 SUMMARY OF INFORMATION RELATING TO GUST LOADS ON AIRPLANES
Many thanks, David.
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Old 10th Apr 2021, 19:02
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For future reference, the gust alleviation factor in its current form was suggested by

Pratt, NACA Technical Note 2964, Washington, June 1953.
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