Autoland without autothrottle on 737
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Autoland without autothrottle on 737
Good evening.
I've got a terrible doubt: is the boeing 737 capabol of autolanding WITHOUT autothrottle engaged?
Thanks in advance.
I've got a terrible doubt: is the boeing 737 capabol of autolanding WITHOUT autothrottle engaged?
Thanks in advance.
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the systems are separate:the autopilot will do the flare while the a/t will retard the thrust. Each one can fail independent of the other: no FLARE engaged,or no RETARD.
You'll have to monitor and take over manually in each case.
Even if you're manually flying,while a/t controlls the speed (not indicated by Boeing) ,you'll see the a/t retarding thrust at 27'.
You'll have to monitor and take over manually in each case.
Even if you're manually flying,while a/t controlls the speed (not indicated by Boeing) ,you'll see the a/t retarding thrust at 27'.
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I thought they had to work in synergy...
What if the pilot closes the throttle too early?
Will it try to compensate for that?
What if the pilot does not close the throttle at all?
What if the pilot closes the throttle too early?
Will it try to compensate for that?
What if the pilot does not close the throttle at all?
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What if the pilot closes the throttle too early? -----> It'll stall 
Will it try to compensate for that?------> No
What if the pilot does not close the throttle at all? -------> IT will Float
Somedays you'd wish you had AT
Will it try to compensate for that?------> No
What if the pilot does not close the throttle at all? -------> IT will Float
Somedays you'd wish you had AT
My company allows you to continue a Cat IIIa approach with an autothrottle failure. PNF calls 25ft RA for throttles to be closed.
I had to do one for real several years ago after the autothrottle could not handle stiff thrust levers on the approach. I just closed them the way I had seen it happen on other autolands or in the sim and it worked fine.
I had to do one for real several years ago after the autothrottle could not handle stiff thrust levers on the approach. I just closed them the way I had seen it happen on other autolands or in the sim and it worked fine.
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Quite a number of experienced 737 captains I know reduce thrust to idle earlier than the AT does, and avoid float by doing this. I have done so myself, by retarding the levers at about 35ft. This technique works well, in my experience, but there may be circumstances (eg significant headwind component, forward CG) in which it could bite you in the backside.
The float in a 'normal' 737 autoland is quite extreme, and uses lots of runway. Why? The aircraft was never designed to autoland, but the feauture was bolted on. The autopilot isn't properly capable of autoland, and relies upon the trim bias applied. This has all sorts of implications, none of them good!
The float in a 'normal' 737 autoland is quite extreme, and uses lots of runway. Why? The aircraft was never designed to autoland, but the feauture was bolted on. The autopilot isn't properly capable of autoland, and relies upon the trim bias applied. This has all sorts of implications, none of them good!
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KIT ,he,he,... I suspect you're a bus pilot....
Not designed to autoland,heh....not like ....
Smart,retard thrust at 35',then low on speed...hard landing....close to a tailstrike.....indeed some 'experienced' captains
.....
If you want so hard to avoid float just do single engine 'autoland'...he,he...
'The autopilot isn't properly capable of autoland, and relies upon the trim bias applied. This has all sorts of implications, none of them good".....how did you come to this 'experienced' conclusion my friend?
Not designed to autoland,heh....not like ....
Smart,retard thrust at 35',then low on speed...hard landing....close to a tailstrike.....indeed some 'experienced' captains
.....If you want so hard to avoid float just do single engine 'autoland'...he,he...
'The autopilot isn't properly capable of autoland, and relies upon the trim bias applied. This has all sorts of implications, none of them good".....how did you come to this 'experienced' conclusion my friend?
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Alex,
Just through autolanding various models of 737 for a number of years. Sorry if that's not good enough.
It's a 'slow cut' from 35ft, by the way, and I wouldn't do it every day.
So, you believe that it was designed for autoland?
and it doesn't rely on trim bias?
I think YOU'RE the one who looks like the 'Bus pilot...
For UK CAA ops, there's no problem autolanding without AT, unless your company imposes more restrictive requirements. OEI autoland is not permitted (but might just be possible, given APU, favourable conditions, and 'switched on' crew).
Heh heh...
LEM,
Boeing advise an additional 1000ft LDR increment to make up for the float, which you say, isn't there.
Just through autolanding various models of 737 for a number of years. Sorry if that's not good enough.
It's a 'slow cut' from 35ft, by the way, and I wouldn't do it every day.
So, you believe that it was designed for autoland?
and it doesn't rely on trim bias?
I think YOU'RE the one who looks like the 'Bus pilot...
For UK CAA ops, there's no problem autolanding without AT, unless your company imposes more restrictive requirements. OEI autoland is not permitted (but might just be possible, given APU, favourable conditions, and 'switched on' crew).
Heh heh...
LEM,
Boeing advise an additional 1000ft LDR increment to make up for the float, which you say, isn't there.
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Yes, but that's more about certificated landing disctance, I think, than the actual behaviour.
I haven't done hundreds of autolands, what I'm saying is in my experience there is no significant additional float.
But since every airplane behaves slightly differently, maybe that is more noticeable on others...
Btw,
doesn't make sense.
Autolanding depends on electronics, not the piece of metal.
Electronics were bolted on as on every other airplane.
You say that.
We've been discussing this in another thread at lenght, and it appears, from various sim experiences, that NOT.
Although nobody is 100% sure until we don't try in the real machine.
I haven't done hundreds of autolands, what I'm saying is in my experience there is no significant additional float.
But since every airplane behaves slightly differently, maybe that is more noticeable on others...
Btw,
The aircraft was never designed to autoland,
Autolanding depends on electronics, not the piece of metal.
Electronics were bolted on as on every other airplane.
and relies upon the trim bias applied.
We've been discussing this in another thread at lenght, and it appears, from various sim experiences, that NOT.
Although nobody is 100% sure until we don't try in the real machine.
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No doubt the aircraft knew it was you, and that it ought to behave! Anyhow, I'm glad your comprehensive flight test programme went so well!!!
Now, you said: .
The aircraft wasn't designed to autoland, because when most of the designing was done, autolanding wasn't part of the scenery...
The reliance upon trim bias makes up for an autoflight system that can't cope with the auto-go-around without biasing the trim beforehand, as it's not capable of controlling the aircraft in pitch - it runs out of authority. No, this is not true for all WaB conditions, of course, but is a decent rule of thumb. The electronics will only change the flight path as far as the bits they're controlling will allow them to, and the hydraulics and other bits on the 737 can't cope as well as they're Toulousean colleagues can.
If you want to try disabling the trim system, in some way the FCCs and other bits can't sense, and then autolanding it, it will probably work. But then, try an auto-go-around, and you'll get close to stalling it, at precisely which point, the APs will disconnect...
Now, you said: .
Autolanding depends on electronics, not the piece of metal.
The reliance upon trim bias makes up for an autoflight system that can't cope with the auto-go-around without biasing the trim beforehand, as it's not capable of controlling the aircraft in pitch - it runs out of authority. No, this is not true for all WaB conditions, of course, but is a decent rule of thumb. The electronics will only change the flight path as far as the bits they're controlling will allow them to, and the hydraulics and other bits on the 737 can't cope as well as they're Toulousean colleagues can.
If you want to try disabling the trim system, in some way the FCCs and other bits can't sense, and then autolanding it, it will probably work. But then, try an auto-go-around, and you'll get close to stalling it, at precisely which point, the APs will disconnect...
Last edited by Kit d'Rection KG; 21st Feb 2005 at 21:37.
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Kit : the reason for the nose up trim is to avoid any handling dificulties in case of a/p disconect.The plane will have a nose up moment in case of a/p disconnect,which will help the pilot in case of G/A decision.
Also,for a failure- disconect bellow 30' ,the plane will flare by itself. Otherwise,when a/t retard thrust,you'll have a nose down moment,maybe a chance for 3 point landing.
The autopilot will have to reset this nose up trim,folowing a G/A ,before single channel can be engaged.
So,see ,this bias trim is not here cause the plane is not 'calculated' for autoland,is here to help the pilot in case of accidental disengagement of the a/p.
The point about systems,hydraulics,etc...is pure b..
,for your info almost all the planes have the same hyd press -around 3000 psi (except the 380-hygher press,around 5000 psi ,I guess)
The pitch thing my friend _loss of authority...,again b .
No trim ,so a less nose up trimming-why you think the plane will stall
in case of G/A?
Trim or not trim the a/p will have the same commands,nose up 15 deg,then after sufficient Vs ,follow the speed for flap.
Again,the tolouse remark -you a bus one.
And the fact about plane designed to autoland... ,I guess you're not a pilot.Sorry.
We can talk for hours about aerodynamic,design,wings,etc...there is no plane designed (or not) to autoland.Point.
What about the 380,or 747 ,are thouse designed to autoland?
.....As I said,you're not a pilot!
Brgds....
Also,for a failure- disconect bellow 30' ,the plane will flare by itself. Otherwise,when a/t retard thrust,you'll have a nose down moment,maybe a chance for 3 point landing.
The autopilot will have to reset this nose up trim,folowing a G/A ,before single channel can be engaged.
So,see ,this bias trim is not here cause the plane is not 'calculated' for autoland,is here to help the pilot in case of accidental disengagement of the a/p.
The point about systems,hydraulics,etc...is pure b..
,for your info almost all the planes have the same hyd press -around 3000 psi (except the 380-hygher press,around 5000 psi ,I guess)The pitch thing my friend _loss of authority...,again b
.No trim ,so a less nose up trimming-why you think the plane will stall
in case of G/A?Trim or not trim the a/p will have the same commands,nose up 15 deg,then after sufficient Vs ,follow the speed for flap.
Again,the tolouse remark -you a bus one.
And the fact about plane designed to autoland...
,I guess you're not a pilot.Sorry.We can talk for hours about aerodynamic,design,wings,etc...there is no plane designed (or not) to autoland.Point.
What about the 380,or 747 ,are thouse designed to autoland?
.....As I said,you're not a pilot!Brgds....
This topic, like in some related threads, lacks definitive knowledge. Whilst I don’t know the 737 in detail, but in the auto-landing aircraft that I do know extremely well there are many factors that have to be considered in order to maintain the required safety levels in comparison with a manual landing. This includes control authority, trim range and rate, and airframe systems – hydraulics, etc. Lack of auto-throttle is just one consideration.
I doubt that any aircraft uses trim bias to enable a landing after an autopilot failure, and as for helping a GA, well 737 pilots report that a manual GA is complicated by the trim bias.
JAR-AWO 123 “Automatic throttle control” requires -
An automatic landing system must include automatic control of throttles to touchdown unless it can be shown that:
(1) Aeroplane speed can be controlled manually without an excessive workload in conditions for which the system is to be certificated;
(2)With manual control of throttles the touchdown performance limits of JAR-AWO 131(c) are achieved; and
(3)The touchdown performance is not critically affected by reasonable errors in speed control.
For inf: Para 131 ‘touchdown performance’ requires that it is improbable that the touchdown is beyond the end of the touchdown zone lighting, 900 m (3000 ft) from threshold;
LEM Glib comments implying that an extra 1000 ft on landing distance doesn’t matter because it is certificated distance, are irresponsible. Although this may be within your limited experience; you may wish to consider acquiring more experience, but hopefully not at the expense of an overrun. You would benefit from reading UK AIC 11/98 “Landing performance of large transport aeroplanes”, which identifies long landings due to float as a contributor to overruns.
I doubt that any aircraft uses trim bias to enable a landing after an autopilot failure, and as for helping a GA, well 737 pilots report that a manual GA is complicated by the trim bias.
JAR-AWO 123 “Automatic throttle control” requires -
An automatic landing system must include automatic control of throttles to touchdown unless it can be shown that:
(1) Aeroplane speed can be controlled manually without an excessive workload in conditions for which the system is to be certificated;
(2)With manual control of throttles the touchdown performance limits of JAR-AWO 131(c) are achieved; and
(3)The touchdown performance is not critically affected by reasonable errors in speed control.
For inf: Para 131 ‘touchdown performance’ requires that it is improbable that the touchdown is beyond the end of the touchdown zone lighting, 900 m (3000 ft) from threshold;
LEM Glib comments implying that an extra 1000 ft on landing distance doesn’t matter because it is certificated distance, are irresponsible. Although this may be within your limited experience; you may wish to consider acquiring more experience, but hopefully not at the expense of an overrun. You would benefit from reading UK AIC 11/98 “Landing performance of large transport aeroplanes”, which identifies long landings due to float as a contributor to overruns.
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comments implying that an extra 1000 ft on landing distance doesn’t matter because it is certificated distance, are irresponsible. Although this may be within your limited experience; you may wish to consider acquiring more experience, but hopefully not at the expense of an overrun.
my alleged statement about "extra distance doesn't matter" comes right out of your imagination.
We were talking about observed behaviour, not about requirements.
What I observed in my experience is that the airplane doesn't float at all.
Also the second part of your comment about my alleged tendency to overrun is pure horsedump.
You would benefit from reading UK AIC 11/98 “Landing performance of large transport aeroplanes”, which identifies long landings due to float as a contributor to overruns.
...LEM