View Full Version : B737ng @(Alpha) speed
737ngpilot
15th Jan 2010, 21:34
Anybody know what the parameter are to get an @ speed
hvogt
15th Jan 2010, 22:01
What exactly do you mean by alpha speed?
Are you talking about min speed reversion - 1.3 Vs? Not 'alpha' - that does not 'exist' on the 737
737ngpilot
16th Jan 2010, 01:58
Sorry for the confusion.
Under speed limiting( flashing A)-minimum speed.....in the MCP IAS/Mach display.
We call this Alpha speed on our property. The question is what is the bases for this speed.
Apparently this speed is a secret as Boeing does not divulge the math behind it.
Capt Chambo
16th Jan 2010, 06:21
From the NG's FCOM 4.20.22:-
Minimum Speed Reversion
The AFDS and A/T do not control to a speed which is less than minimum speed for the current flap configuration. This speed is approximately 1.3 Vs. Minimum speed, FMC speed, or selected speed, whichever is higher, becomes the AFS commanded speed. If actual speed becomes equal to or slightly less than the minimum speed, the underspeed limiting symbol appears in the MCP IAS/Mach Display, and if operating in the V/S mode, the AFDS reverts to LVL CHG. The AFDS will also revert to LVL CHG from VNAV PTH, except when flying a level segment.
The AFS commands a speed 5 knots greater than minimum speed. Reaching a speed 5 knots greater than minimum speed reactivates normal MCP speed selection control. The AFDS commands nose down pitch to increase airspeed if the thrust levers are not advanced. When actual speed becomes 5 knots greater than minimum speed, the underspeed limiting symbol disappears.
The A/P disengages and the F/D command bars retract when in a LVL CHG climb with a command speed equal to minimum speed and a minimum rate of climb cannot be maintained without decelerating.
Minimum speed reversion is not available when the A/T is OFF.
Apparently this speed is a secret as Boeing does not divulge the math behind it. - Hmm! I wish all 'secrets' were that obvious - excuse me, but are you for real Sir? Do you not have a "drivers' handbook" for the model? AKA an Ops Manual? Are you 'operating' without knowing what all the lights and captions mean?
Would you consider 'expanding' your profile a little?
737ngpilot
17th Jan 2010, 00:11
I was in an discussion with our engineering about this and they claim min speed is more complex than 1.3 vso. That's were I was going with this.
This speed is approximately 1.3 Vs.- they are correct, hence the wording. Is it important?