B737ng @(Alpha) speed
Thread Starter
Joined: Aug 2007
Posts: 59
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From: USA
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.
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.
Joined: Feb 2004
Posts: 398
Likes: 0
From: Omicron Persei 8
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.
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.
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
Originally Posted by 737ng
Apparently this speed is a secret as Boeing does not divulge the math behind it.
Would you consider 'expanding' your profile a little?
Last edited by BOAC; 16th January 2010 at 09:59.
