Manoeuvre speed
 

Could someone tell me exactly how minimum flap manoeuvre speed is defined? I know it's the yellow hockey stick on my PFD (737-7), but what exactly does minimum flap manoeuvre speed give you? I know it's based on VREF and therefore increases with weight. But does it give you a safe bank angle (e.g. 40)? Can you go below that speed if you restrict your turns to 15 degree bank? I've searched the 737 FCOM and Googled it for a while and just can't find the answer. Thanks!

P

AFAIK, the flap-speed schedule will in all normal cases allow at least 40 degrees of bank prior to the onset of stick shaker and it is based on an increment over V ref as you say, thus adjusting for weight. This provides a margin for 15 degrees of overshoot beyond 25 degrees of bank. Somewhere in your company docs will be a table showing the Vref increments

Thanks, it's good to know that I was on the right track! No luck finding the increments in my company docs so far (even though it's CDs and you can search the contents). If anybody knows what they are on the 700, please share!

P

Boeing 737-700 QRP PI.10.4

Many thanks! Definitely the down side of having your manuals on CDs, you can't really sit down and flick through them to get a good idea of where everything is...

P

Be careful not to confuse the FLAP MANUEVER SPEED in QRH PI 10.4 (which also shows as labelled green line) and the MINIMUM MANEUVER SPEED which is the yellow hockey stick. They are different things.

The minimum maneuver speed will (i believe) provide a 0.3 margin above the stick shake (i.e. you can pull 1.3 g to the shake at that speed, which happens to be about 40 deg bank in a level turn).

That may be another 'RTFQ' for me! I had assumed the Q referred to the minimum speed at which you should fly at a particular flap setting.

Thanks Rivet gun, I was about to go back to this thread to ask BOAC if he had not confused the two speeds (the old RTFQ, as he said) but you had already done the job for me.

All clear now!

Thanks gentlemen

P

In a holding pattern yesterday so tried putting some numbers to this. Stick shake speed (low speed barber pole) was 160 kts in straight and level flight. Minimum manouvre speed (hockey stick) was 182 Kts.

Now if the theory is correct the minimum manouver speed should be (sqrt 1.3) times the stick shake speed in straight flight, so it seems to be correct.

In the turns the hockey stick remains at 182 but the barber pole increases. At 30 deg bank the barber pole speed is multiplied by a factor of sqrt (1/cos 30) = 172 kts. In theory if you pulled 1.3 g the barber pole and hockey stick would be coincident.

Good work! Makes it easier to grasp any concept when you have a visual demonstration of it.

Now I just need to find a way to trigger the training captain to ask me the question :-)

Thanks again

P