B737 Autoland capability in 1 ch only
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B737 Autoland capability in 1 ch only
Hello you insightful fellow aviators 
I was wondering if you could enlighten me regarding some rumours I have heard about the “hidden” capability for the 737 to be able to do a normal autoland (as in Dual channel) with only one channel engaged.
Our OM-B clearly states that (Classics) “The Autopilot should not be engaged in Single Channel below 50 feet AGL”…Haven’t found this limitation in Boeings FCOM/FCTM though…
Nevertheless, I do have a couple of chaps at work who tell me that the 737 autolands "just as well" in Single Channel also, so should you absolutely need it one day, this is just a “nice to know” thing.
Boys and girls what say you?
I was wondering if you could enlighten me regarding some rumours I have heard about the “hidden” capability for the 737 to be able to do a normal autoland (as in Dual channel) with only one channel engaged.
Our OM-B clearly states that (Classics) “The Autopilot should not be engaged in Single Channel below 50 feet AGL”…Haven’t found this limitation in Boeings FCOM/FCTM though…
Nevertheless, I do have a couple of chaps at work who tell me that the 737 autolands "just as well" in Single Channel also, so should you absolutely need it one day, this is just a “nice to know” thing.
Boys and girls what say you?
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I haven't flown the 737 for about 10 years, but I seem to recall that the autopilot would indeed go through the motions to autoland single channel, and indeed single engine. IIRC the problem is that they have not been demonstrated/certified.
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The autoland function is build into both autopilots,but due to the FAA requirements the autoland is not certified in single channel use.The touchdown is not guaranteed to happen in the touchdown zone using Sch,and you should try ,it in the sim sometimes.It's not so precise like a dual channel flare,a bit hesitating,I think.
I won't try it in real life,you'll have no crosscheck of the autopilot during most critical part of landing,no backtrim at 400',Raltimeters crosscheck,...and you are not authorized to do it.
We do something else here,on every ILS app ,we select both AP on.When sure of landing ,disconnect ,and land manually.If any doubts,for ex late clearance,if bellow 400',leave it on and autoland.
If you think you'll gone need autoland on Sch,I suggest Go around and select both Ap on the second app,or divert somewhere where you can legally land.Simple as that.
Fly safe
I won't try it in real life,you'll have no crosscheck of the autopilot during most critical part of landing,no backtrim at 400',Raltimeters crosscheck,...and you are not authorized to do it.
We do something else here,on every ILS app ,we select both AP on.When sure of landing ,disconnect ,and land manually.If any doubts,for ex late clearance,if bellow 400',leave it on and autoland.
If you think you'll gone need autoland on Sch,I suggest Go around and select both Ap on the second app,or divert somewhere where you can legally land.Simple as that.
Fly safe
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Topslide ,if you've already read the related topic you've seen that I thought the same ,that the 737 won't autoland sch.
Since then I've talked to a B company test pilot,also I've checked the maintainance manuals,and did it on the sim.Also I know of one landing done in the real plane at ,autoland on sch...done allright.
I've said before the main reason for not being allowed to do it ,and the "no flare available on sch" is that the 737 is not approved by the CAA to autoland Sch,and I don't know any other plane being allowed to do it.
Also lack of trim at 400,no cross monitor of the AP,systems,no precision during flare. And ,indeed, 'FLARE' is not available,and it won't appear on the FMA.
Since then I've talked to a B company test pilot,also I've checked the maintainance manuals,and did it on the sim.Also I know of one landing done in the real plane at ,autoland on sch...done allright.
I've said before the main reason for not being allowed to do it ,and the "no flare available on sch" is that the 737 is not approved by the CAA to autoland Sch,and I don't know any other plane being allowed to do it.
Also lack of trim at 400,no cross monitor of the AP,systems,no precision during flare. And ,indeed, 'FLARE' is not available,and it won't appear on the FMA.
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one outopilot on MEL-one more reason to check very carefull the weather -metars,tafs,metars history.I would'nt dispatch with one a/p u/s if any chance for a cat 2-3 app.And we are talking about the 737,not 777,so a shor-medium flight .You should be able to predict the weather with a high degree of accuracy for sucha short period.If in a situation like you said-cat 2 ,I'll go for manual land,instead of sch autoland..Keep in mind that in case of fire many of the systems or instruments are prone to fail ...
If cat3 in force...I'll try it also manually....yrs ago we did a lot of blind landings (curtain on the PF side) with alt calls from PM-in can be done right to touchdown,no problem.
We can imagine a lot more scenarios,but you have to avoid getting yourself in the corner by any means..
brgds
If cat3 in force...I'll try it also manually....yrs ago we did a lot of blind landings (curtain on the PF side) with alt calls from PM-in can be done right to touchdown,no problem.
We can imagine a lot more scenarios,but you have to avoid getting yourself in the corner by any means..
brgds
We had a Sim detail which brught this out. the senerio was dispatch with one A/P U/S (Quite ok by the MEL) than thick cockpoit smoke making it virtuallu impossible to see out (happened to Value-jet).
A single A/P Approach and autoland was the best soution.
Topslide, it's silly to suggest that ANY capability the aircraft has, whether certified or not, should not be understood and available in an emergeny as per above.
A single A/P Approach and autoland was the best soution.
Topslide, it's silly to suggest that ANY capability the aircraft has, whether certified or not, should not be understood and available in an emergeny as per above.
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Interesting, I have flown down to below 200ft on 1 ch and did not observe the stabiliser trim moving to the nose up position as normally happens when conducting a 2 ch auto-land. So I would have to wonder if the aircraft would flare properly during landing... Also if a go-around was required the auto-pilot would disengage if only operating on one channel when TOGA was engaged.
We had a Sim detail which brught this out. the senerio was dispatch with one A/P U/S (Quite ok by the MEL) than thick cockpoit smoke making it virtuallu impossible to see out (happened to Value-jet). A single A/P Approach and autoland was the best soution.
Topslide, it's silly to suggest that ANY capability the aircraft has, whether certified or not, should not be understood and available in an emergeny as per above.
Topslide, it's silly to suggest that ANY capability the aircraft has, whether certified or not, should not be understood and available in an emergeny as per above.
Simulators are good tools for exploring the ‘what if’s’ of human behaviour, deciding what should be done in difficult circumstances etc. Pilots should not seek to outthink the manufacturer or the certification standard of the aircraft, thus always operate within the limitations of the manufacturers documentation.
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Tried it in the B737-500 sim today.
Indeed a very nice autoland, and tried it with one engine inop also.Performed the same as if both autopilots were engaged.
Normal flare as well. Touchdown point accurate as well.
Indeed a very nice autoland, and tried it with one engine inop also.Performed the same as if both autopilots were engaged.
Normal flare as well. Touchdown point accurate as well.
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737 never performed a kiss autoland anyway when i flew it!
The aircraft does not know how to do anything else except autoland as that's what it's designed, BUT NOT CERTIFIED, to do.
The sim does it, and that has all the same bits and software programming as the aircraft.
The aircraft does not know how to do anything else except autoland as that's what it's designed, BUT NOT CERTIFIED, to do.
The sim does it, and that has all the same bits and software programming as the aircraft.
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same true for me. in my first 737 sim session, when we actually got "of the ground" the TRI demonstrated a S-CH autoland. "so that's nice to know for you guys, just in case u ever need it".
it's a shame it's not in the books. at least they could put it there, under "possible, but not certified"
it's a shame it's not in the books. at least they could put it there, under "possible, but not certified"
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I am not a 737 man.....
But reading the above, its very apparent whats going on.
The 737 will autoland on sch. But boeing under no circumstances want airlines flying their a/c round with the intentions of carrying out a sch autoland, hence they have discouraged it within their manuals....and have even gone to the extreme as to say it will not work.
I am pretty sure there are still airlines further afield who would be daft enough to contemplate this if flying MEL.
Sounds a bit harsh I know, but there are a lot of 737's out there being flown by airlines ALL OVER the world. Some of them with not so flawless safety records!!
P.s. If its there, then yes you should know about it, could save your bacon one day!! Although I am sure the CAA/AAIB would love to hear about it......
But reading the above, its very apparent whats going on.
The 737 will autoland on sch. But boeing under no circumstances want airlines flying their a/c round with the intentions of carrying out a sch autoland, hence they have discouraged it within their manuals....and have even gone to the extreme as to say it will not work.
I am pretty sure there are still airlines further afield who would be daft enough to contemplate this if flying MEL.
Sounds a bit harsh I know, but there are a lot of 737's out there being flown by airlines ALL OVER the world. Some of them with not so flawless safety records!!
P.s. If its there, then yes you should know about it, could save your bacon one day!! Although I am sure the CAA/AAIB would love to hear about it......
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I would suggest that aircraft are not certified to autoland on one autopilot because thay cannot be relied on to do it safely and consistantly. They are certainly not fail passive in that situation.
snip
One has to also ask the question, how would you ever get yourself into the situation where you would even consider doing it?!!
snip
One has to also ask the question, how would you ever get yourself into the situation where you would even consider doing it?!!
. They aren't certified to do so for obvious reasons; no failsafe. Even if they could be relied on for safety and consistency, as with everything else in aviation, they need to have redundancy, need to be fail safe. Thats why its possible, not legal.Thats also a very good question, it'd be one bad day if it resulted in a single channel autoland!
Pilots should not seek to outthink the manufacturer or the certification standard of the aircraft, thus always operate within the limitations of the manufacturers documentation.
Try telling Al Hanes, the guy who flew the DC10 with no hydraulics that, or the DHL crew who did something similar recently. Do the manufacturers certify their aircraft to be landed safely after fuel exhaustion? Well we're up to one from each that has!!
Of course I'll fly within the certified limits- right up to the point it's going to kill me. THEN I'd like to know what the aircraft CAN do, not just what it's certified to do.
And the 737 CAN land on one A/P. I may never use that knowledge, but it's still nice to know!
Do not assume
Wizofoz In the DC-10 and A 300 accidents the crew had no choice. In many of the situations quoted for the use of single autoland there could be a choice which the crew needs to make with knowledge of all of the facts.
You make the assumption that the aircraft will behave in exactly the same way as the simulator. Very few training simulators have ‘real’ aircraft equipment, thus the system functions are replications of the autopilot hardware / software as well as the sensor inputs – rad alt, ILS, airspeed, attitude.
One post reports that trim-up is not available during aircraft single system operations, thus the flare performance is most unlikely to be the same even if it works. Without trim-up you may not have adequate protection against a ‘no-flare’ failure or low altitude autopilot disconnect.
In such situations with only one channel you might find yourself with fewer options than in a DC-10 or A 300.
I am more concerned about the underlying principle where pilots fail to distinguish between simulated and real aircraft capability. If pilots believe that they can do anything in the simulator - approved or not, then there is the risk of developing a Macho culture – I can do anything attitude, which spills over to normal operations.
The other concern is how easily individuals form absolute truth – the 737 ‘CAN’ … etc. CRM training should be teaching us not to rush to conclusions, seek all information to confirm the current understanding, and retain healthy scepticism of what you or others believe.
Don’t bet on anything in aviation.
You make the assumption that the aircraft will behave in exactly the same way as the simulator. Very few training simulators have ‘real’ aircraft equipment, thus the system functions are replications of the autopilot hardware / software as well as the sensor inputs – rad alt, ILS, airspeed, attitude.
One post reports that trim-up is not available during aircraft single system operations, thus the flare performance is most unlikely to be the same even if it works. Without trim-up you may not have adequate protection against a ‘no-flare’ failure or low altitude autopilot disconnect.
In such situations with only one channel you might find yourself with fewer options than in a DC-10 or A 300.
I am more concerned about the underlying principle where pilots fail to distinguish between simulated and real aircraft capability. If pilots believe that they can do anything in the simulator - approved or not, then there is the risk of developing a Macho culture – I can do anything attitude, which spills over to normal operations.
The other concern is how easily individuals form absolute truth – the 737 ‘CAN’ … etc. CRM training should be teaching us not to rush to conclusions, seek all information to confirm the current understanding, and retain healthy scepticism of what you or others believe.
Don’t bet on anything in aviation.
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Then again, on our fleet of 737-800's we have to disconnect the autopilot by 1000' agl and land using our "Heads Up Display" which allows us to go down to 600 RVR... and we actually hand fly the landing and touchdown/rollout.
The first time you land hand flying at 600 RVR you think this is crazy, but after about 2 approaches, the HUD makes it very, very capable and comfortable.
Pat
The first time you land hand flying at 600 RVR you think this is crazy, but after about 2 approaches, the HUD makes it very, very capable and comfortable.
Pat