Deselect speed (autothrottle) on B737
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First let me just say; you are up way to early for a sundaymorning.
Ok, let me give it a try (not knowing if you are a bit familiar with the 737 or are even a pilot).
One way of getting rid of the autothrottle is to disconnect it completely. Speedprotection (autothrottle will come back when the speed falls below selected speed to maintain the that speed) is not available as well as Autothrottle GoAround thrust in case of TOGA selection.
The other way to get rid of Autothrottle is to deselect it on the MCP, and yes, in this case all the above is still available (as displayed by 'ARM' in the FMA).
Hope this sheds some light.
Who needs a coffee..
Ok, let me give it a try (not knowing if you are a bit familiar with the 737 or are even a pilot).
One way of getting rid of the autothrottle is to disconnect it completely. Speedprotection (autothrottle will come back when the speed falls below selected speed to maintain the that speed) is not available as well as Autothrottle GoAround thrust in case of TOGA selection.
The other way to get rid of Autothrottle is to deselect it on the MCP, and yes, in this case all the above is still available (as displayed by 'ARM' in the FMA).
Hope this sheds some light.
Who needs a coffee..
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If you press the Auto-throttle speed button, auto-throttle speed mode is de-selected and it falls into 'Arm'. This means you have manual thrust control back but auto-ga thrust capability if you hit toga and low speed protection if you get too slow. I thinks its a good way to do manual flight but there are drawbacks. If it is gusty, the low speed protection can keep kicking in which is annoying. Also, I heard a story that a crew once upon a time got too slow in the flare and the low speed protection kicked in causing a tail-strike (with the pitch up moment). I can't see this myself but who knows. When I close the throttles, I hold them closed to avoid such occurences. Hope this helps.
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Hi,
If the A/T is working on MCP speed, push "Speed" on the MCP panel. You will get the A/T in "ARM" mode.
EDIT : Whoops did not notice previous reply
If the A/T is working on MCP speed, push "Speed" on the MCP panel. You will get the A/T in "ARM" mode.
EDIT : Whoops did not notice previous reply
Last edited by I-2021; 6th May 2007 at 10:24.
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http://www.pprune.org/forums/showthread.php?t=235512
and
http://www.pprune.org/forums/showthread.php?t=10958
and this from MY latest copy of the 737FCTM
<To simplify thrust setting procedures, autothrottle use is recommended during takeoff and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged.>
<The autothrottle ARM mode is normally not recommended because its function can be confusing. The primary feature the autothrottle ARM mode provides is minimum speed protection in the event the airplane slows to minimum maneuvering speed. Other features normally associated with the autothrottle, such as gust protection, are not provided. The autothrottle ARM mode should not be used with Non-Normal checklists. Some malfunctions that affect maneuvering speeds cause the autothrottle to maintain a speed above approach speed.>
and
http://www.pprune.org/forums/showthread.php?t=10958
and this from MY latest copy of the 737FCTM
<To simplify thrust setting procedures, autothrottle use is recommended during takeoff and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged.>
and
<The autothrottle ARM mode is normally not recommended because its function can be confusing. The primary feature the autothrottle ARM mode provides is minimum speed protection in the event the airplane slows to minimum maneuvering speed. Other features normally associated with the autothrottle, such as gust protection, are not provided. The autothrottle ARM mode should not be used with Non-Normal checklists. Some malfunctions that affect maneuvering speeds cause the autothrottle to maintain a speed above approach speed.>
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.. and, if you just wanted a very vanilla flavoured answer .. it's a bit like being in a motor car with cruise control on ... pressing the brake pedal puts you back to manual throttle. In the aircraft, there are various switches similar to the brake pedal which do the same thing. All the other considerations are add-ons.
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Thanks for the replies. So if you push the speed button on the MCP, while he light is illuminated, you will deselect speed, light will go out and A/T engages in ARM mode.
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it's easier hand flying using manual thrust levers because of the pitching effect of thrust changes. Far easier to set a fixed thrust, fly the correct profile, and see what happens to the speed.
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Well you say manufacturers recommendations; a Boeing instructor pilot told me that he is completely pro the deselect speed, for the obvious advantages stated above.
He did say that the FCTM does not openly recommend it due to the "lowest common denominator" aspect that leads to the statement about "may cause confusion".
ie the lawyers at Boeing have seized control of the FCTM and they can't recommend anything slightly controversial.
He did say that the FCTM does not openly recommend it due to the "lowest common denominator" aspect that leads to the statement about "may cause confusion".
ie the lawyers at Boeing have seized control of the FCTM and they can't recommend anything slightly controversial.
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Rainboe you state: 'This is the standard airline recommended procedure in the UK'.
With which companys for example?
I did some B737 training in Uk and also the training Captains in my airline in Europe trained other companys also. Speed ARM was never taught or advised. The system was not designed to be used like that!!!
Have to agree totally with A37575 : 'In the case of the 737 series, if you are going to hand fly the aircraft other than take off and initial climb, then switch of the auto-throttle system altogether'.
With which companys for example?
I did some B737 training in Uk and also the training Captains in my airline in Europe trained other companys also. Speed ARM was never taught or advised. The system was not designed to be used like that!!!
Have to agree totally with A37575 : 'In the case of the 737 series, if you are going to hand fly the aircraft other than take off and initial climb, then switch of the auto-throttle system altogether'.
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Funny, I use it, but some of the older captains when i have called 'speed off' have said no A/T off, doesn't really bother me either way but funny how it seems to be the older boys who dont use it..hmm something to ponder...or not!!!
It seems to be something that BA, and DFO's who are ex BA or have been BA trained do.
I have done a B737 NG course in Seattle, and 3 renewals with Alteon and never has it been offered as an SOP. In fact the IP's required us to operate as per the manual which BOAC has quoted.
I have done a B737 NG course in Seattle, and 3 renewals with Alteon and never has it been offered as an SOP. In fact the IP's required us to operate as per the manual which BOAC has quoted.
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Telstar - I think that accident is not pertinent to this discussion as it was a manual approach flown with auto-throttle engaged? It does, however, re-inforce the Boeing advice on not doing that!
Certainly BA (on the 737) - and current airline - 'teach' the 'armed' mode for manual landings. In both it is pretty well an 'SOP', if unwritten. In BA it was even 'encouraged' for the last few hundred feet of a s/engine approach to give a/throttle g/a (and very useful that was in the sim where you always go round
) - despite the Boeing FCTM 'restriction'.
I have seen the disruption of a landing in 'armed' (from the RHS). The main problem will occur in that rare event when the HP flies the correct approach speed (instead of around +15 ), and particularly at F40 where 1.3Vs can be v v close to Vref+5. IF the HP then starts a flare a bit early (ie above 27'RA) and the a/t kicks in as designed as the speed (correctly) washes off towards Vref-5, you can get the traditional 'fly-past' until it is sorted.
Personally my preference is for a/t off for manual flying and push hand forward for g/a.
Certainly BA (on the 737) - and current airline - 'teach' the 'armed' mode for manual landings. In both it is pretty well an 'SOP', if unwritten. In BA it was even 'encouraged' for the last few hundred feet of a s/engine approach to give a/throttle g/a (and very useful that was in the sim where you always go round
) - despite the Boeing FCTM 'restriction'.I have seen the disruption of a landing in 'armed' (from the RHS). The main problem will occur in that rare event when the HP flies the correct approach speed (instead of around +15
), and particularly at F40 where 1.3Vs can be v v close to Vref+5. IF the HP then starts a flare a bit early (ie above 27'RA) and the a/t kicks in as designed as the speed (correctly) washes off towards Vref-5, you can get the traditional 'fly-past' until it is sorted. Personally my preference is for a/t off for manual flying and push hand forward for g/a.
See para 2.1.
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Ok just to clarify all: I am saying for manual flight, of course, the A/T should be off. I agree with 'A37575' and 'BOAC' in what they said, and the examples they gave.
As for manual flight, with the A/T in the ARM mode, well 'Rainboe', you do have a valid point - with using 'TOGA- it's useful and prevents inadvertent overboosting or overthrust and one of the pilots having to attend to thrust at a time when the gear and flap are being raised very close to the ground.'
Of couse this is really the only advantage in this procedure of using the ARM mode.
It can make life easier during a go-around, but NOT always!! Be careful.
'Rainboe', I guess we could come to a compromise and say, leave it in ARM, then during the flare disconnect it altogether. But one fine day, you will get a new pilot pushing the wrong button on the throttle levers, and instead of disconnecting they will advance. Or the other way around - if left in the ARM mode, the throttles kicking in during the flare as the aircraft gets to slow.
As a Training Captain on this aircraft, teaching new pilots on type, who are still trying to understand the autoflight systems, I have found it a lot more simple and easier for them, to encourage the A/T to be completely OFF when manual flying. If a go-around is necessary, then PF pulls back on the yoke and at the same time coordinates the application of go-around thrust, where after the PM confirms it has been set correctly or re-adjusts it.
For experienced pilots like yourself, who understand its limitations, then if you feel comfortable, use the ARM mode.
Thats all I can say.
As for manual flight, with the A/T in the ARM mode, well 'Rainboe', you do have a valid point - with using 'TOGA- it's useful and prevents inadvertent overboosting or overthrust and one of the pilots having to attend to thrust at a time when the gear and flap are being raised very close to the ground.'
Of couse this is really the only advantage in this procedure of using the ARM mode.
It can make life easier during a go-around, but NOT always!! Be careful.
'Rainboe', I guess we could come to a compromise and say, leave it in ARM, then during the flare disconnect it altogether. But one fine day, you will get a new pilot pushing the wrong button on the throttle levers, and instead of disconnecting they will advance. Or the other way around - if left in the ARM mode, the throttles kicking in during the flare as the aircraft gets to slow.
As a Training Captain on this aircraft, teaching new pilots on type, who are still trying to understand the autoflight systems, I have found it a lot more simple and easier for them, to encourage the A/T to be completely OFF when manual flying. If a go-around is necessary, then PF pulls back on the yoke and at the same time coordinates the application of go-around thrust, where after the PM confirms it has been set correctly or re-adjusts it.
For experienced pilots like yourself, who understand its limitations, then if you feel comfortable, use the ARM mode.
Thats all I can say.
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Ok just to clarify all: I am saying for manual flight, of course, the A/T should be off. I agree with 'A37575' and 'BOAC' in what they said, and the examples they gave.
As for manual flight, with the A/T in the ARM mode, well 'Rainboe', you do have a valid point - with using 'TOGA- it's useful and prevents inadvertent overboosting or overthrust and one of the pilots having to attend to thrust at a time when the gear and flap are being raised very close to the ground.'
Of couse this is really the only advantage in this procedure of using the ARM mode.
It can make life easier during a go-around, but NOT always!! Be careful.
'Rainboe', I guess we could come to a compromise and say, leave it in ARM, then during the flare disconnect it altogether. But one fine day, you will get a new pilot pushing the wrong button on the throttle levers, and instead of disconnecting they will advance. Or the other way around - if left in the ARM mode, the throttles kicking in during the flare as the aircraft gets to slow.
As a Training Captain on this aircraft, teaching new pilots on type, who are still trying to understand the autoflight systems, I have found it a lot more simple and easier for them, to encourage the A/T to be completely OFF when manual flying. If a go-around is necessary, then PF pulls back on the yoke and at the same time coordinates the application of go-around thrust, where after the PM confirms it has been set correctly or re-adjusts it.
For experienced pilots like yourself, who understand its limitations, then if you feel comfortable, use the ARM mode.
Thats all I can say.
As for manual flight, with the A/T in the ARM mode, well 'Rainboe', you do have a valid point - with using 'TOGA- it's useful and prevents inadvertent overboosting or overthrust and one of the pilots having to attend to thrust at a time when the gear and flap are being raised very close to the ground.'
Of couse this is really the only advantage in this procedure of using the ARM mode.
It can make life easier during a go-around, but NOT always!! Be careful.
'Rainboe', I guess we could come to a compromise and say, leave it in ARM, then during the flare disconnect it altogether. But one fine day, you will get a new pilot pushing the wrong button on the throttle levers, and instead of disconnecting they will advance. Or the other way around - if left in the ARM mode, the throttles kicking in during the flare as the aircraft gets to slow.
As a Training Captain on this aircraft, teaching new pilots on type, who are still trying to understand the autoflight systems, I have found it a lot more simple and easier for them, to encourage the A/T to be completely OFF when manual flying. If a go-around is necessary, then PF pulls back on the yoke and at the same time coordinates the application of go-around thrust, where after the PM confirms it has been set correctly or re-adjusts it.
For experienced pilots like yourself, who understand its limitations, then if you feel comfortable, use the ARM mode.
Thats all I can say.