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## Vref calculation

Can anyone tell me the formula to calculate the Vref speed?
I think that is based in Vso speed, but i dont remember... :-roll

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Pedro

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## RE: Vref calculation

[font size="1" color="#FF0000"]LAST EDITED ON Mar-17-03 AT 04:53PM (EST)[/font][p]Vref = 1.3 * Vso

Matt

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## RE: Vref calculation

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Pedro

Portugal

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## RE: Vref calculation

Vref=1.3 Vso is a good rule of thumb for small GA aircraft. However, different aircraft use different methods of determining Vref, based upon things such as weight, wind, or fuel load. For example...the MD-80 at 110,000lbs Vref is 128Kts + 5 + 1/2 the wind gust factor while the T-38 uses 155kias +1 kt per 100lbs of fuel greater than 1000lbs. The FAA actually has requirements for Vref that are set out in FAR Part 23 and 25 (according to how the aircraft is certified) as well.

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## RE: Vref calculation

I'm going to have to display my ignorance here and ask you to define Vso? Also, Brad, very interesting to see the precise formulae, but I'm curious why the MD-80 isn't just 133kts + 1/2 gust factor (mathematically the same as 128kts + 5 + 1/2 the gusts)?

Thanks :-)

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## RE: Vref calculation

Vs0 is stall speed in a clean configuration.

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