B737 EFIS "Speed Off"
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B737 EFIS "Speed Off"
I have had the chance to fly 737s EFIS for various airlines and one specific difference in SOPs is about pressing the MCP "Speed" button off on final in order to bring the A/T in an "ARM" status mode. Some people pretend you have to be out of your mind to act so and others say you have to be out of your mind not to act so...Very disturbing. Some people simply cut the A/T out as soon as they've returned to the Manual mode.
I find arming the A/T vs keeping the A/T on (MCP SPD mode) on final very comfortable and still safe because you still have a chance to have the A/T recovering a situation when the speed would fall below the set MCP speed. And I find this technique safer and more comfortable than keeping the "full" A/T on as you don't have to fight the moving A/T.
I have tried and find documentation regarding this topic and could not retrieve anything relevant. Anyone could feed me with more info such as Boeing recommendations or other official docs ? Thanks.
I find arming the A/T vs keeping the A/T on (MCP SPD mode) on final very comfortable and still safe because you still have a chance to have the A/T recovering a situation when the speed would fall below the set MCP speed. And I find this technique safer and more comfortable than keeping the "full" A/T on as you don't have to fight the moving A/T.
I have tried and find documentation regarding this topic and could not retrieve anything relevant. Anyone could feed me with more info such as Boeing recommendations or other official docs ? Thanks.
Boeing recommend against this because of the possibilit of uncommanded auto-throttle activation near the runway and resultant chance of tail-strike or long touchdown.
That being said, it was SOP at Ansett for many years with no problems.
That being said, it was SOP at Ansett for many years with no problems.
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Some airlines encourage it because if you need to go around then you just press the TOGA buttons and the throttles will set themselves, but as others have said views differ on the matter.
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So, I understand there is no sharply-cut answer on this matter. Arguments are going to go on and on... Actually, I'm getting a bit fed up with this subject between 737-pilots. Whatever your view or feeling, you are bound to be someone's nerd at some point (sigh)...
Can anyone give names of airlines in favor of 1/ A/T ARM 2/ Full A/T 3/ No A/T at all, when switching to manual ? When you give big names, that tends to make points of view much more nuanced...
If only Boeing could impose a clear order.
Can anyone give names of airlines in favor of 1/ A/T ARM 2/ Full A/T 3/ No A/T at all, when switching to manual ? When you give big names, that tends to make points of view much more nuanced...
If only Boeing could impose a clear order.
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Boeing makes it clear.
U cannot land with the AT engaged. It would simply increase thrust to maintain speed...causing a low level flyby in the landing config.
They also say, if the AP is off, the AT should not be engaged.
Now i don,t remember wx or not it's explicitly stated, but it's safer to fly the approach with the AT armed, since the pushing the TOGA swiches in this setup wil initiate the GA sequence. Same thing on the 777. Flying with the AT OFF, it can be stalled, however, if u fly the approach with the AT ARMED, it will "wake up" to prevent a stall.
U cannot land with the AT engaged. It would simply increase thrust to maintain speed...causing a low level flyby in the landing config.
They also say, if the AP is off, the AT should not be engaged.
Now i don,t remember wx or not it's explicitly stated, but it's safer to fly the approach with the AT armed, since the pushing the TOGA swiches in this setup wil initiate the GA sequence. Same thing on the 777. Flying with the AT OFF, it can be stalled, however, if u fly the approach with the AT ARMED, it will "wake up" to prevent a stall.
Last edited by Check Airman; 20th Jul 2006 at 21:17.
Check,
That is not correct. We used to land with A/T ON, A/P Off all the time. If the A/T is on at 26'RA, it goes into RETARD just like in an autoland. This procedure actually had the advantage that you only needed a 5kt additive to VREF regardless of wind, so was useful onto limiting runways.
That is not correct. We used to land with A/T ON, A/P Off all the time. If the A/T is on at 26'RA, it goes into RETARD just like in an autoland. This procedure actually had the advantage that you only needed a 5kt additive to VREF regardless of wind, so was useful onto limiting runways.
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Until Boeing came out clearly with the recommendation to turn it off when flying manually, my personal preference was to "deselect speed" (i.e. leave it armed) until below 100 feet, then click it off for the landing. As a devotee of Vref+5 under almost all conditions, it helped silence nervous co-pilots who wanted another 10 knots for mum and the kids on every approach! Even one as inept as I was not likely to need any further low speed protection from the 100 ft point. Autoland was the only time I left it on below 100 ft.
But now Boeing have become more definitive in advising against leaving it armed when flying manually, so who am I (or you) to go against this? It doesn't take long to get used to the idea of being responsible for one's own low speed control, after all many of us never saw an autothrottle before the B737 and managed worse aircraft quite well without it for many years.
Airlines going against Boeing's advice really should be required to put a waiver in their manuals to say that while they acknowledge the manufacturer, they know better (which in some very large airlines with a huge amount of experience with the aircraft type could be the case). And that they accept full responsibility for any variations. The real problem for line pilots arises when they come up against check pilots who insist on their own stuff which is not in the manuals. Tricky, because if they won't put it in the manual, you probably should not be doing it.
But now Boeing have become more definitive in advising against leaving it armed when flying manually, so who am I (or you) to go against this? It doesn't take long to get used to the idea of being responsible for one's own low speed control, after all many of us never saw an autothrottle before the B737 and managed worse aircraft quite well without it for many years.
Airlines going against Boeing's advice really should be required to put a waiver in their manuals to say that while they acknowledge the manufacturer, they know better (which in some very large airlines with a huge amount of experience with the aircraft type could be the case). And that they accept full responsibility for any variations. The real problem for line pilots arises when they come up against check pilots who insist on their own stuff which is not in the manuals. Tricky, because if they won't put it in the manual, you probably should not be doing it.
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MAS
As a co-pilot on the 737 some years back the proc used to be armed mode.
Now as a capt, the sop has been changed to All off when manual.
I still prefer the armed mode, untill 50' or so, it dosent take much to switch it off, just a click from the tumb.
Having flown diff type's of aircraft now, i prefer it on, especially in the ops we do with all this tropical wx and all.
As a co-pilot on the 737 some years back the proc used to be armed mode.
Now as a capt, the sop has been changed to All off when manual.
I still prefer the armed mode, untill 50' or so, it dosent take much to switch it off, just a click from the tumb.
Having flown diff type's of aircraft now, i prefer it on, especially in the ops we do with all this tropical wx and all.
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No... Pushing TOGA with the A/T disengaged will result in F/D popping up and commanding a G/A without any increase in thrust. If the A/T is left armed then its a different ball game. Problem is, you may get the low speed protection kicking in at 30' with the intent of recovering a slighty low speed, but at 27' it forgets all about that and retards the thrust levers (ouch). Thats why some folks above have talked about removing it at 50-100'.
Me? I leave it in all the way. If the low speed protection does anything below 100' then it goes.
Me? I leave it in all the way. If the low speed protection does anything below 100' then it goes.
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From my Boeing FCTM, page 1.35, AFDS Guidelines, Autothrottle use:
"Autothrottle use is recommended during take off and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged."
"Autothrottle use is recommended during take off and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged."
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Originally Posted by Wizofoz
Check,
That is not correct. We used to land with A/T ON, A/P Off all the time. If the A/T is on at 26'RA, it goes into RETARD just like in an autoland. This procedure actually had the advantage that you only needed a 5kt additive to VREF regardless of wind, so was useful onto limiting runways.
That is not correct. We used to land with A/T ON, A/P Off all the time. If the A/T is on at 26'RA, it goes into RETARD just like in an autoland. This procedure actually had the advantage that you only needed a 5kt additive to VREF regardless of wind, so was useful onto limiting runways.
