Throttle procedures for Landing
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Throttle procedures for Landing
Hello,
I read an old topic in "spectators balcony" section on Throttle Procedure for Boeing Landings which has made me curious.
If I try to summarize.
On Boeing the philosophy is:
1. Hand-flying: fly with manual throttle.
2. Precision approaches:
Automatic landing are done with A/T engaged.
In case of A/T unserviceability, autoland can be realized with manual throttle control.
3. On 737 Classic and NG and 757:
approach and landing can be realized A/T armed (for engagement in MCP SPD I suppose) and manual control of throttle.
=>this is realized with AP disconnect so only in non-precision approaches or in CAT 1, isn't it ?
Do I have well understood?
This makes me wondering on other points.
4. Generally speaking, is the RETARD mode related to autoland ?
I mean, even if you do an approach CAT2 with A/T engaged but without autoland available (failure on AP system design), do pilots have to disengaged A/T to do the RETARD or is the A/T design to RETARD anyway ?
(I realize that a general answer to my question may be difficult due to link to the design of aircraft series.
Is it possible to compare Boeing A/T philosophy and Airbus A/T philosophy for the RETARD ?)
5. Then, what about the call-out “RETARD” ? With Boeing A/T, retard is automatically done. So is there only a call-out done by PNF when hand-flying or an auto call-out in both manual and auto-fly ?
I read an old topic in "spectators balcony" section on Throttle Procedure for Boeing Landings which has made me curious.
If I try to summarize.
On Boeing the philosophy is:
1. Hand-flying: fly with manual throttle.
2. Precision approaches:
Automatic landing are done with A/T engaged.
In case of A/T unserviceability, autoland can be realized with manual throttle control.
3. On 737 Classic and NG and 757:
approach and landing can be realized A/T armed (for engagement in MCP SPD I suppose) and manual control of throttle.
=>this is realized with AP disconnect so only in non-precision approaches or in CAT 1, isn't it ?
Do I have well understood?
This makes me wondering on other points.
4. Generally speaking, is the RETARD mode related to autoland ?
I mean, even if you do an approach CAT2 with A/T engaged but without autoland available (failure on AP system design), do pilots have to disengaged A/T to do the RETARD or is the A/T design to RETARD anyway ?
(I realize that a general answer to my question may be difficult due to link to the design of aircraft series.
Is it possible to compare Boeing A/T philosophy and Airbus A/T philosophy for the RETARD ?)5. Then, what about the call-out “RETARD” ? With Boeing A/T, retard is automatically done. So is there only a call-out done by PNF when hand-flying or an auto call-out in both manual and auto-fly ?
Last edited by airfriend; 12th Feb 2010 at 12:17.
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Wow, that's quite a complicated post! This is my understanding.
Boeing
Manual Landing: At some point during the approach the Autopilot is disconnected so that the aircraft can be hand flown. It is possible to hand-fly the aircraft with the A/T still engaged (most company SOPs don't recommend this). It is normal practice to disconnect the A/T shortly after disengaging the Autopilot for a full hand-flown approach and landing.
Autoland: The Autopilot and A/T remain engaged. During the rollout, the autothrottle will automatically retard the thrust levers to idle.
Exact procedures depend on company SOPs (Standard Operating Procedures) and there are also subtle differences between aircraft type.
For example: Double clicking the A/T Disc switch on the 737 classic disconnects and disarms the A/T. During a go-around the pilot must manually advance the thrust levers. On the 744, double clicking the A/T Disc switch disengages the A/T but it remains armed and will engage in THR REF if the TOGA switches are pressed.
I'm not very familiar with Airbus FBW systems, but this is my understanding.
Airbus
For a manual landing it is normal practice to use the A/T for speed control. The thrust levers remain at the CLB gate and the FADEC controls thrust to maintain speed. During the rollout the GPWS calls "RETARD RETARD" and the thrust levers are manually closed. The same applies during an autoland, except that the autopilot is coupled of course???
Somebody feel free to jump in and clarify!
Boeing
Manual Landing: At some point during the approach the Autopilot is disconnected so that the aircraft can be hand flown. It is possible to hand-fly the aircraft with the A/T still engaged (most company SOPs don't recommend this). It is normal practice to disconnect the A/T shortly after disengaging the Autopilot for a full hand-flown approach and landing.
Autoland: The Autopilot and A/T remain engaged. During the rollout, the autothrottle will automatically retard the thrust levers to idle.
Exact procedures depend on company SOPs (Standard Operating Procedures) and there are also subtle differences between aircraft type.
For example: Double clicking the A/T Disc switch on the 737 classic disconnects and disarms the A/T. During a go-around the pilot must manually advance the thrust levers. On the 744, double clicking the A/T Disc switch disengages the A/T but it remains armed and will engage in THR REF if the TOGA switches are pressed.
I'm not very familiar with Airbus FBW systems, but this is my understanding.
Airbus
For a manual landing it is normal practice to use the A/T for speed control. The thrust levers remain at the CLB gate and the FADEC controls thrust to maintain speed. During the rollout the GPWS calls "RETARD RETARD" and the thrust levers are manually closed. The same applies during an autoland, except that the autopilot is coupled of course???
Somebody feel free to jump in and clarify!
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I like to keep the A/T in on landing on the Boeing because it will give you speed protection.You can use the throttles manually like if it was disconnected, but when they are disconnected if you dont keep an eye on the speed you can get close to the stalling speed and drop out the sky.
With the A/T in, if the speed did get close to the stalling speed the throttles will automatically push forward giving extra thrust.
With the A/T in, if the speed did get close to the stalling speed the throttles will automatically push forward giving extra thrust.
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Lockheed L1011 TriStar (yes, I know, not a Boeing, nevertheless)...
Autothrust fully approved for both manual and automatic approach/land (autoland)...or, manual thrust for both manual landings or..auto.
NO restrictions.
A superior design that is the best in the business.
First flown forty years ago, this year.
Autothrust fully approved for both manual and automatic approach/land (autoland)...or, manual thrust for both manual landings or..auto.
NO restrictions.
A superior design that is the best in the business.
First flown forty years ago, this year.
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Will the A/T automatically reduce to idle while flaring, if you have A/T engaged during a manual landing?
If it does I guess it's coupled to the the radar altimiter, like during autoland. Or how else can it know when to retard the throttles...?
If it does I guess it's coupled to the the radar altimiter, like during autoland. Or how else can it know when to retard the throttles...?
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Will the A/T automatically reduce to idle while flaring, if you have A/T engaged during a manual landing?
Thrust reduction begins at 50 feet, and autothrust automatically trips off at 5 feet radio height.
Not on the 757 / 767 MYID.
If you leave the AT on with the AP disconnected and hand fly the AT will simply try to maintain the speed you have selected in the MCP.
This can lead to a rather long float as you approach touchdown and need to reduce power the AT will simply try to maintain your speed, maintaining or even adding power.
Not good and I have had to remind a few people over the years of this as I realise what they are trying to do !
Of course, on a full Autoland with AT and AP engaged the AT will reduce to idle in the flare.
If you leave the AT on with the AP disconnected and hand fly the AT will simply try to maintain the speed you have selected in the MCP.
This can lead to a rather long float as you approach touchdown and need to reduce power the AT will simply try to maintain your speed, maintaining or even adding power.
Not good and I have had to remind a few people over the years of this as I realise what they are trying to do !
Of course, on a full Autoland with AT and AP engaged the AT will reduce to idle in the flare.
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On the 737 it will start to reduce thrust to idle with an RA indicating 27' or below, as has been shown in the THY accident. No matter if the AP is on or not, both systems operate on their own and are not directly related to each other. FMA indication is "RETARD" and it will stay in this mode until the aircraft switches into ground mode.
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We had this discussion many years ago on a B737-300 fleet:
Is it ok to deselect speed mode when switching off the autopilot for a manual landing to have the autothrottle speed protection available or switch off the autothrottle completely?
The question was asked to Boeing and Boeing answered that it is NOT recommended to deselect the autothrottle speed mode and it IS recommended to completely switch off the autothrottle. (B737-300)
The reason given by Boeing was that with the autothrottle in ARM there is a high risk for a tailstrike upon autothrottle intervention in a gust condition during flare when flying manual.
I recommend to check your flightcrew training manual for the recommended manufacturers procedure and if there is any doubt or someone thinks to reinvent the wheel, ask your airplane manufacturer for his opinion.
Just my 2 cents...
Is it ok to deselect speed mode when switching off the autopilot for a manual landing to have the autothrottle speed protection available or switch off the autothrottle completely?
The question was asked to Boeing and Boeing answered that it is NOT recommended to deselect the autothrottle speed mode and it IS recommended to completely switch off the autothrottle. (B737-300)
The reason given by Boeing was that with the autothrottle in ARM there is a high risk for a tailstrike upon autothrottle intervention in a gust condition during flare when flying manual.
I recommend to check your flightcrew training manual for the recommended manufacturers procedure and if there is any doubt or someone thinks to reinvent the wheel, ask your airplane manufacturer for his opinion.
Just my 2 cents...
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So the key word there is 'GUST Conditions'....now I can see boeings view on the matter and agree with them because of the pitch/power couple it has.
But what about in CAVOK conditions?? It shouldn't be a problem then right? There was an incident down at bournemouth I believe where a 737 on approach reached the stalling speed and had to go around and the sticker shaker was going off, If they had the AT in and speed off then that problem wouldn't have came along due to the automatic increase in thrust.
At the end of the day you will be following your company SOP's so just do that.
But what about in CAVOK conditions?? It shouldn't be a problem then right? There was an incident down at bournemouth I believe where a 737 on approach reached the stalling speed and had to go around and the sticker shaker was going off, If they had the AT in and speed off then that problem wouldn't have came along due to the automatic increase in thrust.
At the end of the day you will be following your company SOP's so just do that.
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Speed deselect is not a recommended mode of operation in the standard FCOM, but it is in boeing issued company tailored ones provided the correct training and SOP around it is used. We do it that way now for over 18 years both in classics and NGs without one single tailstrike. In fact the average tailstrike margin on the -800 is much higher than it is on the airbus fleet.
Especially during flare i do not really see the problem as the autothrust is in flare retard mode below 27' anyway and doesn't try to keep any speed. Above that it will intervent when the speed drops of course.
Anyway, operate according to your company SOPs, but dont switch off your airmanship and common sense, in doubt just switch everything off and fly it manually, allways works best.
Especially during flare i do not really see the problem as the autothrust is in flare retard mode below 27' anyway and doesn't try to keep any speed. Above that it will intervent when the speed drops of course.
Anyway, operate according to your company SOPs, but dont switch off your airmanship and common sense, in doubt just switch everything off and fly it manually, allways works best.
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411A do you think that is possible to find any ?
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411A is not the only old guy on the plant to love the L1011..in fact I loved the C47 just as much.
On the L1011 I flew the auto throttles could freeze and no warning was generated if the throttle drive motor failed.
If this occurred coupled to the glide path... the pitch attitude increasing was the first indication shortly followed by increasing loss of IAS... that is if the last throttle position was not delivering sufficient thrust.
I recall this silent failure combined with lack of pitch and IAS scaning caused an expensive tail strike and rear bulkhead fracture on an auto approach followed by a late auto pilot disconnect for a manual landing.
Thankfully when this drive motor failed combined with a flap lock out due poor maintenance after an all night red eye at 6.00am on a LHR Cat3 I had luckily seen it demonstrated before,and combined with BA L1011 pitch awareness training so I was ready for it. I feel for the crews who have not had this training and are faced with similar type pitch / power problems.
On the L1011 I flew the auto throttles could freeze and no warning was generated if the throttle drive motor failed.
If this occurred coupled to the glide path... the pitch attitude increasing was the first indication shortly followed by increasing loss of IAS... that is if the last throttle position was not delivering sufficient thrust.
I recall this silent failure combined with lack of pitch and IAS scaning caused an expensive tail strike and rear bulkhead fracture on an auto approach followed by a late auto pilot disconnect for a manual landing.
Thankfully when this drive motor failed combined with a flap lock out due poor maintenance after an all night red eye at 6.00am on a LHR Cat3 I had luckily seen it demonstrated before,and combined with BA L1011 pitch awareness training so I was ready for it. I feel for the crews who have not had this training and are faced with similar type pitch / power problems.
