Testing to establish Vne

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geosnooker2000

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Mar 30, 2019
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Somerville, TN
So according to 23.335 ( I believe), it's all very cut and dried when you are designing to establish a base.
Design Cruising Speed (Vc) = 33 * Sqrt (wing loading)
Design Dive Speed (Vd) = 1.4 * Vc
Never Exceed Speed (Vne) = 0.9 * Vd
Then it says to flight test to expand the envelope further.
So am I correct in assuming that to increase Vne, that you MUST test to find a Vd, and then multiply that by .9 to establish a new Vne?

Example: FAR calcs yield for a hypothetical -

@2200 max TOw
Vc = 32' span’* 4.5’ chord = 144 sf (wing loading = 15.28) Sqrt = 3.9
Vc = 33* 3.9
Vc = 129 knots (148mph)

Vd = 1.4* 129
Vd = 180.8 (208 mph)

Vne = 0.9 *180.8
Vne = 163 (187mph)

If one wanted to increase the Vc to 170mph, one MUST put the plane in a dive to 238mph during a flight test? I mean, I realize the E-AB world theoretically has no "must", but ... best practices?
 

Marc Zeitlin

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Dec 11, 2015
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Tehachapi, CA
Yep.

And because it's a flutter test, you need to rap the stick and rudder pedals in all directions as well, and do each rap at the highest altitude at which you believe you could ever achieve those numbers.

Scariest **** thing you'll ever do in an airplane. Pretty much why almost nobody flutter tests their E-AB aircraft. They should, but they don't.
 

N804RV

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Jun 9, 2013
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423
Location
Mount Vernon, WA
Yep.

And because it's a flutter test, you need to rap the stick and rudder pedals in all directions as well, and do each rap at the highest altitude at which you believe you could ever achieve those numbers.

Scariest **** thing you'll ever do in an airplane. Pretty much why almost nobody flutter tests their E-AB aircraft. They should, but they don't.

I read a book not long ago, can't find it now. But, it was a memoir of a test pilot who was a contemporary of Lindberg and specialized in dive testing because, as he put it, "no one else wanted to do it".

Excellent book, wish I could remember the name of the pilot, or title of the book. His descriptions of dive testing some of those old military birds is hair-raising!
 
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