just got the captain flight manual set , nice stuff. deep.

i need some help with vref .

what is vref 40 ?

i am familiar with the take off v speeds and the idea of v2 + xx

but i have never been familiar with vref 40 or vref 40 + 70 as is in the flight crew training manual.

appreciate the help. thanks

V_ref is the reference speed for the aircraft dependent upon weight and flap position. See, for example, FCOM1 at page 500 for the 737-600 table. I think it's based on 1.3 x stall speed.

 

If V_ref 40 + 70 is specified (say for a no-flap landing), it means that you should work out what the Vref would ordinarily be for your current weight at flaps 40, and add 70 knots.

 

cheers,

 

jeff

Vref 40 is actually 1.25x stall @40. I think it was because at flaps 40 approach, engines are in higher N1 and more responsive.

 

Vref is used normally as a basis for approach speed.

appreciate the help , thanks.