Turb switch
Joined: Oct 2009
Posts: 1,270
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From: UK
Hi The Cav,
I don't know about the Classic, but the L1011 had an autopilot TURB mode (PFM). It worked really well and prevented large pitch excursions whilst chasing small deviations in altitude.
Pity AF447 didn't have one fitted.
"Turbulence mode provides pilot-assisted, constant attitude flight through turbulent air. The autopilot control authority is reduced in order to soften its response to attitude changes caused by the turbulence.
Turbulence is an autopilot mode only and cannot be selected unless an autopilot is engaged. The TURB mode may be selected any time either autopilot is in CWS or CMD and A/L TRACK or GO AROUND is not established. The TURB light will illuminated indicating mode selection. Verification of mode engagement is accomplished by checking for TURB legend on in both AFCS MODES annunciators. When turbulence is selected while the autopilot engage lever is in the CMD position, the solenoid held lever drops from CMD to CWS. This action essentially cancels all other modes.
No other mode can be selected while the turbulence mode is engaged. The turbulence mode can only be released by pressing the TURB switch a second time or by disengaging the autopilot. Either of these actions then, is a prerequisite to resuming normal autopilot-controlled flight after a turbulence encounter.
If a flight director is also on when turbulence is selected, its command bars will be biased out of view but no FD warning flag will appear. When TURB is canceled, the command bars will return if the FD switch was left on but it will have a new reference. The new reference is the attitude existing at the time of TURB cancellation since all previous modes were canceled when TURB was selected."
I don't know about the Classic, but the L1011 had an autopilot TURB mode (PFM). It worked really well and prevented large pitch excursions whilst chasing small deviations in altitude.
Pity AF447 didn't have one fitted.
"Turbulence mode provides pilot-assisted, constant attitude flight through turbulent air. The autopilot control authority is reduced in order to soften its response to attitude changes caused by the turbulence.
Turbulence is an autopilot mode only and cannot be selected unless an autopilot is engaged. The TURB mode may be selected any time either autopilot is in CWS or CMD and A/L TRACK or GO AROUND is not established. The TURB light will illuminated indicating mode selection. Verification of mode engagement is accomplished by checking for TURB legend on in both AFCS MODES annunciators. When turbulence is selected while the autopilot engage lever is in the CMD position, the solenoid held lever drops from CMD to CWS. This action essentially cancels all other modes.
No other mode can be selected while the turbulence mode is engaged. The turbulence mode can only be released by pressing the TURB switch a second time or by disengaging the autopilot. Either of these actions then, is a prerequisite to resuming normal autopilot-controlled flight after a turbulence encounter.
If a flight director is also on when turbulence is selected, its command bars will be biased out of view but no FD warning flag will appear. When TURB is canceled, the command bars will return if the FD switch was left on but it will have a new reference. The new reference is the attitude existing at the time of TURB cancellation since all previous modes were canceled when TURB was selected."
Last edited by rudderrudderrat; 7th September 2011 at 12:30. Reason: copied text from http://l1011project.blog spot.com/2011/07/l-1011-autoflight-turbulence-mode-22-20.html
Joined: Apr 2008
Aviation Qualifications: ATPL
Posts: 836
Likes: 101
From: uk
It was used if the cabin crew told us that the passengers would not sit down when the seat belt signs were switched on. Selecting it produced computor generated turbulence through the auto-pilot, which got progressively more pronounced until they were all strapped in, when it could be switched off.
Joined: Jul 2007
Posts: 812
Likes: 19
From: uk
CAV: If I remember correctly, it continued the nav/heading part of the autopilot but the pitch had to be controlled through the pitch wheels. ie. the A/P would not try to hold the altitude - this was done with the pitch wheels.
Joined: Sep 2006
Posts: 68
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From: UK
There is a little more info at the b737.org site
Automatics - An illustrated guide to the different MCP's & autopilots used on the 737
Automatics - An illustrated guide to the different MCP's & autopilots used on the 737
Joined: Oct 2009
Posts: 1,270
Likes: 0
From: UK
Hi Zorin_75,
If they had a "TURB" mode, it would have maintained wings level and an attitude they selected. They then could let go of the stick and simply set the power.
It was a very basic autopilot mode which only required attitude information.
How could it have helped them?
It was a very basic autopilot mode which only required attitude information.
Joined: May 2011
Posts: 131
Likes: 0
From: here
If they had a "TURB" mode, it would have maintained wings level and an attitude they selected. They then could let go of the stick and simply set the power.
It was a very basic autopilot mode which only required attitude information.
It was a very basic autopilot mode which only required attitude information.
Joined: Jan 2008
Posts: 463
Likes: 8
From: FL 600. West of Mongolia
Concorde had a TURB autopilot mode also. I can never remember it being used much, if at all. Probably similar to the Classic/L1011 concept, the idea was that the aircraft maintained pitch and heading hold (the basic engage modes) but with reduced gain to prevent large axis excursions.
Best regards
Dude
Best regards
Dude
