Vref calculation

**lonepilot** · 03-17-2003, 04:45 PM

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

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Pedro

Portugal

**MKaprocki** · 03-17-2003, 04:53 PM

[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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**lonepilot** · 03-17-2003, 05:19 PM

Thanks for your quick answer, Matt ;-)

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Pedro

Portugal

**OStateFlyer** · 03-17-2003, 05:26 PM

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.

Brad

**lsdunch** · 03-19-2003, 12:48 AM

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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