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  #11  
Old 09-24-2021, 07:21 AM
sailvi767 sailvi767 is offline
 
Join Date: Sep 2010
Location: Charlotte NC
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Many certified manufacturers have similar limits where you can use IAS up to a specific altitude. Above that you revert to TAS. VNE is a combination of flutter margin and structural strength. Flutter margin is generally a true airspeed function. Structural issues are IAS related. Itís quite common to have a aircraft where structural failure will occur before flutter. In that case IAS is the appropriate measure for VNE. From everything posted here it sure appears that Vans is comfortable with flutter limits up to 16,000 PA and 136 knots indicated.
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  #12  
Old 09-24-2021, 01:58 PM
rgmwa rgmwa is offline
 
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Yes, but the POH doesn’t make this very clear. Also the big step change in the speed limit switching between IAS and TAS at 16,000’ is hard to understand. I’d be interested to know how that’s derived. Not that it’s much of a limitation since I’d probably have passed out well before I got that high anyway.
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  #13  
Old 09-24-2021, 04:25 PM
sailvi767 sailvi767 is offline
 
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If you climb at 136 knots TAS will exceed 136 knots as soon as you lift off. The difference grows as you climb but it starts at liftoff or even before if your airport is not at sea level and itís not a standard day.
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  #14  
Old 09-24-2021, 08:04 PM
rgmwa rgmwa is offline
 
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Well just to keep things simple, I'm going to say that Vne for my plane is 136KTAS. If that means that according to the POH, my safety margin increases as I go higher that's a good thing. Then I only have to look at one speed readout and it doesn't matter if the margin magically disappears at 16,001' for no apparent reason while I’m on my way to a new altitude record. Anyway, since I can only get to 136 kts in any system of measurement in a dive, if I'm forced to descend at an angle somewhat less than vertical, I can live with that too. I'll just enjoy the view for a bit longer.
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Last edited by rgmwa : 09-24-2021 at 08:28 PM.
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