B737 - Use of 2 APs on Cat 1 Approach
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B737 - Use of 2 APs on Cat 1 Approach
I have heard it suggested recently that some guys like to arm the 2nd AP at GS capture during a Cat 1 approach when it is considered unlikely that they'll 'get in' in order to have the AP remain engaged for the Go Around..
(It's pretty shabby the way the 737 just drops the AP when you press TOGA on a 1 AP approach - why Boeing thought it was a good idea to massively increase the flightdeck workload at such a critical point is highly questionable).
At first hearing it sounded like a good idea, however..... on 2 AP approach, the stabilizer gets trimmed nose up at 400ft so a decsion to 'land' at Cat 1 minima, followed by an AP disconnect for the manual landing will leave the pilot handling an aircraft with unusual NU trim at a point when he wants to be heading for the TDZ....
Any thoughts / experiences?
If your PF wanted to do this, would you consider he was making good use of available resources or a potentially dangerous deviation from SOPs?
(It's pretty shabby the way the 737 just drops the AP when you press TOGA on a 1 AP approach - why Boeing thought it was a good idea to massively increase the flightdeck workload at such a critical point is highly questionable).
At first hearing it sounded like a good idea, however..... on 2 AP approach, the stabilizer gets trimmed nose up at 400ft so a decsion to 'land' at Cat 1 minima, followed by an AP disconnect for the manual landing will leave the pilot handling an aircraft with unusual NU trim at a point when he wants to be heading for the TDZ....
Any thoughts / experiences?
If your PF wanted to do this, would you consider he was making good use of available resources or a potentially dangerous deviation from SOPs?
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The trim isn't a problem if you're aware of it.
Grasp the wheel firmly, press the button, then a half second of trim and you're back in business.
Bear in mind that even though the runway may be man land, and you are doing a cat one approach with a cat1 decision height, you may be able to leave the a/p connected to a later radio height.
That few seconds extra after seeing the lights and before going manual can make all the difference to the landing as the A/p tends to track nicely down the middle on calm claggy days, giving you a chance to build up a better visual perspective.
I've seen too many people see the lights then disconnect and instinctively duck under for a better view, only to find the ground coming up to meet them.
Grasp the wheel firmly, press the button, then a half second of trim and you're back in business.
Bear in mind that even though the runway may be man land, and you are doing a cat one approach with a cat1 decision height, you may be able to leave the a/p connected to a later radio height.
That few seconds extra after seeing the lights and before going manual can make all the difference to the landing as the A/p tends to track nicely down the middle on calm claggy days, giving you a chance to build up a better visual perspective.
I've seen too many people see the lights then disconnect and instinctively duck under for a better view, only to find the ground coming up to meet them.
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buttline, I think the answer is fairly straightforward.
If this is a procedure set out in your company's SOP's which all have been trained for, then fine.
However, if it's not, then it's a deviation from SOP's with all the problems that will ensue if something goes wrong.
Seat1APlease, it's all very well saying the nose up trim can be easily dealt with until someone doesn't deal with it and it causes a problem, if it's not a company SOP. Long landing, short wet runway for example?
If you are trained to do a manual go-around from a Cat 1 approach, and it's in the SOP's, then that's what should be done.
The other point about leaving the A/P engaged below DA is irrelevant to the question (with all due respect), as you can do this with only one A/P engaged anyway.
SOP's are SOP's.
If this is a procedure set out in your company's SOP's which all have been trained for, then fine.
However, if it's not, then it's a deviation from SOP's with all the problems that will ensue if something goes wrong.
Seat1APlease, it's all very well saying the nose up trim can be easily dealt with until someone doesn't deal with it and it causes a problem, if it's not a company SOP. Long landing, short wet runway for example?
If you are trained to do a manual go-around from a Cat 1 approach, and it's in the SOP's, then that's what should be done.
The other point about leaving the A/P engaged below DA is irrelevant to the question (with all due respect), as you can do this with only one A/P engaged anyway.
SOP's are SOP's.
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Lem, I fully agree, SOP's don't cover everything. But they should cover major areas of the operation like how to do an approach and go-around, and what configuration of automatics is permissable!
The question wasn't specifically about the landing, it was about the go-around.
However, I agree with you, an autoland could be done in this instance when weather is close to CAT 1 minima. Of course, the crew must now ensure they are both fully aware of what calls are to be made etc. And if LVP's are not in force or the ILS is only CAT 1, they mustn't make the mistake of being suckered into thinking they have full CAT 11/CAT 111 protection. Very easy to slip below CAT 1 DA with nothing seen and both autopilots engaged.............................
The question wasn't specifically about the landing, it was about the go-around.
However, I agree with you, an autoland could be done in this instance when weather is close to CAT 1 minima. Of course, the crew must now ensure they are both fully aware of what calls are to be made etc. And if LVP's are not in force or the ILS is only CAT 1, they mustn't make the mistake of being suckered into thinking they have full CAT 11/CAT 111 protection. Very easy to slip below CAT 1 DA with nothing seen and both autopilots engaged.............................
Last edited by Maximum; 29th Apr 2004 at 23:22.
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I just started my line training on the 737-800 and i must admit having flown Dash8's and then the ERJ-145 i found the 73 a bit dissapointing as far as technology is concerned.
I can understand though why Boeing made it that way and as we all know is due to type comonality with the previous 73's.
But yes i agree totally that its silly that the a/c can't cope with a single a/p go-around.
I say what a waste of a potentially brilliant a/c.
I can understand though why Boeing made it that way and as we all know is due to type comonality with the previous 73's.
But yes i agree totally that its silly that the a/c can't cope with a single a/p go-around.
I say what a waste of a potentially brilliant a/c.
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It is not surprising to read these posts because they demonstrate how automation has not only blunted pure flying ability but it also encourages a mental fear where suddenly it becomes almost a Mayday situation to execute a normal two engine GA using autothrottle, FD and hands on the stick handling.
I believe that the purpose of the two autopilot approach was strictly for a Cat 2 or 3 autoland or GA. With a DH of 100 or 50RA, it is understandable that a full automatic pilot GA was perceived as a safer bet than a manual GA.
But to consider that a normal manually flown GA with autothrottle and FD is overloading the crew is stretching incredulity a bit too far. Even a simple GA on full raw data and nil automatics should be straight forward to any pilot trained to an average ccompetency. If the pilot is not competent to fly such a manaoeuvre then it would seem good use is not being made of the simulator.
Why are people so apprehensive of a GA in other than Cat 2 or Cat 3 weather, that they have to have to rely on the full automatics as if it was their life. GA are certainly a lot less stressful than landing in a 30 knot crosswind and you don't read too many scare stories about crosswind landings.
Countless trees have been felled to provide the paper for articles on the dangers of total blind reliance on automation. Yet airline ops management continue stumble along the way of total automation as the only way to ensure safe flying.
Even had a new pilot in the simulator talking about raw data braking. He meant manual (non-automatic braking) which to him was almost a PAN situation.
I believe that the purpose of the two autopilot approach was strictly for a Cat 2 or 3 autoland or GA. With a DH of 100 or 50RA, it is understandable that a full automatic pilot GA was perceived as a safer bet than a manual GA.
But to consider that a normal manually flown GA with autothrottle and FD is overloading the crew is stretching incredulity a bit too far. Even a simple GA on full raw data and nil automatics should be straight forward to any pilot trained to an average ccompetency. If the pilot is not competent to fly such a manaoeuvre then it would seem good use is not being made of the simulator.
Why are people so apprehensive of a GA in other than Cat 2 or Cat 3 weather, that they have to have to rely on the full automatics as if it was their life. GA are certainly a lot less stressful than landing in a 30 knot crosswind and you don't read too many scare stories about crosswind landings.
Countless trees have been felled to provide the paper for articles on the dangers of total blind reliance on automation. Yet airline ops management continue stumble along the way of total automation as the only way to ensure safe flying.
Even had a new pilot in the simulator talking about raw data braking. He meant manual (non-automatic braking) which to him was almost a PAN situation.
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Hey Hudson,
I know what you mean, but I'm not quite sure how you got all of that from these posts! Maybe a bit unfair?
Having said that, in general terms I agree there are some these days who seem very shy about just going back to basics and flying the aeroplane.
Now that tickled me! 
It is not surprising to read these posts because they demonstrate how automation has not only blunted pure flying ability but it also encourages a mental fear where suddenly it becomes almost a Mayday situation to execute a normal two engine GA using autothrottle, FD and hands on the stick handling.
Having said that, in general terms I agree there are some these days who seem very shy about just going back to basics and flying the aeroplane.
Even had a new pilot in the simulator talking about raw data braking. He meant manual (non-automatic braking) which to him was almost a PAN situation.
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Hudson,
Sounds like you spend a lot of time in the sim these days.
When you're doing a complicated perfomance limited GA near high ground (several turns involved) in bad weather Cat1 minima on the 5th sector of a 6 sector day with a colleague who's on the last of an 8 day stint of earlies with no break and you've just got back from 10 days holiday things are a little different.
Not a competancy issue - of course we can handle it. However, I think a good operating crew know when they are tired and seek to minimize their workload as much as possible. Getting the best out of the machine and crew when under pressures of time and fatigue is the name of the game.
For every pilot/operator who you believe relies on the automatics too much, I reckon there's another one who throws the automatics away too quickly because he/she doesn't understand how to get the best out of them.
Sounds like you spend a lot of time in the sim these days.
When you're doing a complicated perfomance limited GA near high ground (several turns involved) in bad weather Cat1 minima on the 5th sector of a 6 sector day with a colleague who's on the last of an 8 day stint of earlies with no break and you've just got back from 10 days holiday things are a little different.
Not a competancy issue - of course we can handle it. However, I think a good operating crew know when they are tired and seek to minimize their workload as much as possible. Getting the best out of the machine and crew when under pressures of time and fatigue is the name of the game.
For every pilot/operator who you believe relies on the automatics too much, I reckon there's another one who throws the automatics away too quickly because he/she doesn't understand how to get the best out of them.
Last edited by buttline; 4th May 2004 at 22:11.
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Buttline. I sympathise with your obvious workload and a dog tired crew. However, rather than be forced to fall back on all the bells and whistles that automation provides because you are that fatigued, would you not think it a safer option not to accept the flight if your fatigue is that serious. Isn't there a regulation somewhere that says you have a duty of care not to fly fatigued?
Apart from that, in my book any pilot proud of his profession should be equally competent at both hand flying skills and automation skills. Pure flying skills are absolutely vital in this profession. Automation is not much help if you find yourself upside down in a severe thunderstorm.
If you are apprehensive of raw data skills, then It would suggest that there is something fundamentally wrong with your training department.
Apart from that, in my book any pilot proud of his profession should be equally competent at both hand flying skills and automation skills. Pure flying skills are absolutely vital in this profession. Automation is not much help if you find yourself upside down in a severe thunderstorm.
If you are apprehensive of raw data skills, then It would suggest that there is something fundamentally wrong with your training department.
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and, Buttline, try to imagine the need to fly manually when you are that tired because of equipment failure.
That's why pilots must train themselves regularly to be always ready, in case....
That's why pilots must train themselves regularly to be always ready, in case....
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Many good questions and topics here guys!
(1) Can you fly CAT 1 autoland even if it is not in your SOP?
B737 SOPs are based on Boeing's Manuals, which are written under the assumption that the user has had previous multi–engine jet aircraft experience and is familiar with basic jet airplane systems and basic pilot techniques common to airplanes of this type. Therefore, the operations manual does not contain basic flight information that is considered prerequisite training.
(2) B737 Autoland is not restricted to CAT II & III only.
(3) Just tried to disconnect dual autopilots at low altitude in the plane (not sim). The nose up force was barely noticeable and did not cause a problem at medium weights in classic and NG.
(1) Can you fly CAT 1 autoland even if it is not in your SOP?
B737 SOPs are based on Boeing's Manuals, which are written under the assumption that the user has had previous multi–engine jet aircraft experience and is familiar with basic jet airplane systems and basic pilot techniques common to airplanes of this type. Therefore, the operations manual does not contain basic flight information that is considered prerequisite training.
(2) B737 Autoland is not restricted to CAT II & III only.
(3) Just tried to disconnect dual autopilots at low altitude in the plane (not sim). The nose up force was barely noticeable and did not cause a problem at medium weights in classic and NG.
Last edited by 80/20; 6th May 2004 at 14:01.
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Why should you not do an AUTOLAND CAT I?. Is it neccassary to
write it in the SOP that you can do it?. Or is it better to write
you can`t?. If you restrict your operation by regulating everything
then you have no flexibility in common sense cases. I hope it
helps. We have dual channel APP in all CAT I and CAT II cases.
To disconnect the AP is really not a big deal. You know what you
expect when you push the button to continue manualy. We have
the HUD in all of our NG`s and that helps as well to allign the AC
in the slot and put her on the spot. The saving of fuel and brakes
pays for itself allone as you are able to fly the speed more
accurate and gate even flare guidance. It takes you a few times
until you get used to it but then you can grease her on as well.
The logic behind is that the HUD to point you to the Centerline
and the touch down zone.
NG
write it in the SOP that you can do it?. Or is it better to write
you can`t?. If you restrict your operation by regulating everything
then you have no flexibility in common sense cases. I hope it
helps. We have dual channel APP in all CAT I and CAT II cases.
To disconnect the AP is really not a big deal. You know what you
expect when you push the button to continue manualy. We have
the HUD in all of our NG`s and that helps as well to allign the AC
in the slot and put her on the spot. The saving of fuel and brakes
pays for itself allone as you are able to fly the speed more
accurate and gate even flare guidance. It takes you a few times
until you get used to it but then you can grease her on as well.
The logic behind is that the HUD to point you to the Centerline
and the touch down zone.
NG
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Why should you not do an AUTOLAND CAT I?.
Buttline's original question was actually about the go-around situation by the way.
As for SOP's, the only point I was making was that all crews should be aware of how to operate and what is considered good operating practice by the airline, in lets face it, what is a very common area of the operation - an approach down to CAT 1 minima. I'm sure we've all flown for airlines where the SOP's are less than clear, and every single pilot has their own way of doing something. Not a good situation.
I'll also re-state, though not a problem in itself, if the crew perform an autoland in actual CAT 1 conditions, using a CAT 1 ILS without LVP's in force, then they must be aware that they only have CAT 1 protection. ie, the possibility of a deviation off the centreline below 200' must be expected more than on a CAT 2 or 3 approach.
Now before everyone starts shouting, I know that the crew will be visual below DA/DH, and can monitor the A/P performance, so basically no problem. However we are talking of the case of actual CAT 1 limits, so marginal vis etc. So a slightly different situation to a normal practice autoland. A kind of subtle environmental capture can occur, because the viz is fairly low, where the crew forget they don't have the LVP protection they would normally have on a CAT 2/3 approach, and are therefore taken more by surprise if the aircraft starts drifting off the centreline.
Not a huge problem on the whole, as it usually works out fine, but just a small point I've seen some people not being entirely aware of.
