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#1
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Vne
I know that Vne can vary with altitude but does it also vary with aircraft weight?
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#2
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Vne
At 18:49 09 November 2019, jp wrote:
I know that Vne can vary with altitude but does it also vary with aircraft weight? Yes |
#3
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Vne
Ehhhhhhh no. In our very sub supersonic world Vne is based on how fast the molecules actually go over the wing, which is the contributing factor to flutter. That's Vne, more specifically, it's given as a True Air Speed because that's the actual speed against molecules. Now what DOES change is the indicated speed for Vne, since IAS is a function more of HOW MANY molecules are getting rammed into the pitot tube. It's important to know those numbers as you descend out of wave. Vne as marked on the gauge red line is invalid up at the higher altitudes. Flying out west up high it may be more like 110kts indicated when the TAS is actually at redline.
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#4
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Vne
Hmmm, I thought Vne Is basically a guess by the FAA that 10% below Vd is safer than 5% below Vd. Vne = 0.9 X Vd (FAR/JAR 23), dive speed Vd determined emperically and is a function of design cruising speed Vc.
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#5
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Vne
Haven't read that, would be an interesting one though. I'd always been under the impression Vne is a flutter protection speed. That's why it's a TAS that doesn't change with weight like Va. Wouldn't be surprised if it was from some old math though.
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#6
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Vne
On Sunday, November 10, 2019 at 7:02:57 AM UTC-8, Echo wrote:
Haven't read that, would be an interesting one though. I'd always been under the impression Vne is a flutter protection speed. That's why it's a TAS that doesn't change with weight like Va. Wouldn't be surprised if it was from some old math though. I always thought Vne was an operational limit to airworthiness, usually derived from the flutter speed. Also that flutter speed was an odd power function of altitude (because it varies somewhat with density but not as fast as IAS, therefore TAS is safe). Also that it is an oscillatory phenomena which depends on the stiffness, mass, and forcing function - so practically does depend on weight (or at least mass), particularly of the wings but secondarily the fuselage. But that function would be way too complicated to put on the placard or even into regulations so no change is assumed. I also didn't think it was required to air test flutter speed anymore, but could be calculated with mass, stiffness, and CFD codes. |
#7
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Vne
Also I don't think the FAA is responsible for the manufacturers testing and certification necessarily, especially when they're overseas. I mean, they really had strong oversight in the 737 max....
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#8
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Vne
At 18:49 09 November 2019, jp wrote:
I know that Vne can vary with altitude but does it also vary with aircraft weight? Yes |
#9
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Vne
Onlynif over max weight and with an engineering order. Within the certified weight range, it stays the same.
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#10
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Vne
Charlie Quebec wrote on 11/9/2019 12:53 PM:
Onlynif over max weight and with an engineering order. Within the certified weight range, it stays the same. It may depend on the glider, particularly gliders that carry ballast in the wings. My guess is pilot weight would have such a small effect, it would not mentioned in the operating handbook. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
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