B737 Classic- A/T de-select speed
Thread Starter
Always nice to start a thread that get's an interesting discussion going!
Definitely agree the practice has it's advantages IF it is applied with rigorous caveats (Not used with non-normal configs, not used in gusty conditions etc.).
That is where the problem can lie, and it largely comes down to the ethos of the operator- strictly prescriptive or open to different techniques.
Spent the last decade with the former, and now am working for the latter- and probably need to adjust my thinking accordingly!
Definitely agree the practice has it's advantages IF it is applied with rigorous caveats (Not used with non-normal configs, not used in gusty conditions etc.).
That is where the problem can lie, and it largely comes down to the ethos of the operator- strictly prescriptive or open to different techniques.
Spent the last decade with the former, and now am working for the latter- and probably need to adjust my thinking accordingly!
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The airliner I flew for did not have this procedure. I kind of love it though...not for low speed protection but for go around.
I always had my hands on throttle when flying manually and found my self overriding it occasionally when I did not like what it was doing.
I always had my hands on throttle when flying manually and found my self overriding it occasionally when I did not like what it was doing.
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This is a terrific discussion for people like me, newly typed in the NG at this late stage of life (don’t get me started…). I really like the airplane, brings back enough 727 memories to last me and is so antithetical to the Airbus that I am practically gleeful. However, our training department, as is the case in many settings, lives in a stovepipe, enjoying life without the slightest notion of how any airplanes actually work other than their own. For us more senior, less flexible types, coming off years of 767/757/MD80 operations, the nuance of the 737 has been challenging. Wouldn’t hurt if the manuals were slightly more informative, but maybe that’s just me…
I started out getting chastised for pickling off the A/T at 100 feet…”we don’t do that…” “Do what?” “Disengage the autothrottle…” “What? Why?” “We just don’t…”
We had a bit of discussion about the “technique” of deselecting speed and leaving the autothrottle in ARM. As others have pointed out, this is frowned upon. Interestingly enough, if I understand it correctly, that is exactly what will happen at VNAV disconnect, which will occur at the end of the approach. This could be some distance from the runway. In any event, VNAV disconnect will leave the A/T in the ARM mode exactly as would deselecting the speed mode. I think.
If I’ve got this right, not only does the A/T arm mode give you alpha floor protection, but it also is armed for go-around (below 2000 feet, etc., etc.) Hence the wonderful ability to get autothrust during the FD-only go-around following the VNAV disconnect with no runway in sight.
The only drawback I could see to deselecting speed mode is that one has to reach up and push the correct button without smashing your cheek on the HUD combiner while peering around trying to find said button. On the other hand, as I was told I would, I’m not sure I see any real advantage over just leaving the A/T active and manually overriding it as needed.
RAT 5, "who ever thought that using the flap lever to drive the speed bug on GA was good idea. Duh!" is the best explanation of that gimmick that I've heard. Apparently I was supposed to figure that out by osmosis.
I started out getting chastised for pickling off the A/T at 100 feet…”we don’t do that…” “Do what?” “Disengage the autothrottle…” “What? Why?” “We just don’t…”
We had a bit of discussion about the “technique” of deselecting speed and leaving the autothrottle in ARM. As others have pointed out, this is frowned upon. Interestingly enough, if I understand it correctly, that is exactly what will happen at VNAV disconnect, which will occur at the end of the approach. This could be some distance from the runway. In any event, VNAV disconnect will leave the A/T in the ARM mode exactly as would deselecting the speed mode. I think.
If I’ve got this right, not only does the A/T arm mode give you alpha floor protection, but it also is armed for go-around (below 2000 feet, etc., etc.) Hence the wonderful ability to get autothrust during the FD-only go-around following the VNAV disconnect with no runway in sight.
The only drawback I could see to deselecting speed mode is that one has to reach up and push the correct button without smashing your cheek on the HUD combiner while peering around trying to find said button. On the other hand, as I was told I would, I’m not sure I see any real advantage over just leaving the A/T active and manually overriding it as needed.
RAT 5, "who ever thought that using the flap lever to drive the speed bug on GA was good idea. Duh!" is the best explanation of that gimmick that I've heard. Apparently I was supposed to figure that out by osmosis.
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Just make sure you have correct terminology and thought process:
A/P engaged and A/T connected...OK
A/P disengaged and A/T disconnected...OK
A/P disengaged and A/T switch selected on...NO
A/P disengaged and A/T DESELECTED (so in ARM)...WHY NOT (reversion mode in case PF stuffs up, for safety)
Yes G/A thrust (as well as FD guidance) provided after TOGA selected. 1 click 1000-2000fpm ROC, 2 clicks full G/A thrust...lots of grunt and lots of fun!
A/P engaged and A/T connected...OK
A/P disengaged and A/T disconnected...OK
A/P disengaged and A/T switch selected on...NO
A/P disengaged and A/T DESELECTED (so in ARM)...WHY NOT (reversion mode in case PF stuffs up, for safety)
Yes G/A thrust (as well as FD guidance) provided after TOGA selected. 1 click 1000-2000fpm ROC, 2 clicks full G/A thrust...lots of grunt and lots of fun!
2 clicks full G/A thrust...lots of grunt and lots of fun!
The demo is simple. Have the student manually approach in the full flap landing configuration. At 100 feet direct him to go around with full power while simultaneously asking him to remove his hands clear of the control wheel. Ask him to observe the rate of pitch up and pitch up angle. Freeze the simulator as the pitch up passes 45 degrees and point out that the aircraft will keeping on pitching up under full power until it stalls.
If ever a demonstration convinces the student the need to actively control the pitch attitude during a low altitude full power go-around in the 737, this demo should do the trick. A picture is worth a thousand words.
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The most powerful flying control in the 737 is the stabilizer. Why that most powerful control is hidden behind two little switches on the yoke is Boeing’s business, but the fact that it is, has claimed lives (TK1951 et al). Conversely, automating that control in the way the French did, and making it transparent to the crew, is also deadly (AF447).
The stab is sized to cope with the full power go-around under the least favourable circumstances, down to approximately Vref-5 KIAS. Below that speed, control is not assured, and a reduction of thrust is necessary.
Each time I look at the tail I compare the size and range of movement of the elevators, and the size and range of movement of the stab, and remind myself of that.
Regarding the OP’s question: The autothrottle was not designed to ‘wake up’ and provide low speed protection during landing. The fact that it does something reminiscent of the envelope protection of other designs doesn’t make it fit for that purpose, as the manufacturer cautions. I’m not a fan of blind acceptance of manufacturer’s guidance, but in this case, I stick with what Boeing say.
The stab is sized to cope with the full power go-around under the least favourable circumstances, down to approximately Vref-5 KIAS. Below that speed, control is not assured, and a reduction of thrust is necessary.
Each time I look at the tail I compare the size and range of movement of the elevators, and the size and range of movement of the stab, and remind myself of that.
Regarding the OP’s question: The autothrottle was not designed to ‘wake up’ and provide low speed protection during landing. The fact that it does something reminiscent of the envelope protection of other designs doesn’t make it fit for that purpose, as the manufacturer cautions. I’m not a fan of blind acceptance of manufacturer’s guidance, but in this case, I stick with what Boeing say.
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...but it will "wake up" on a dark night, scud-running min wx approach at 600 ft if the PF's scan rate fails and he allows the speed to approach the stall
...and it will provide G/A thrust upon TOGA for a go-around (which of course the PF will back up anyway and not forget!)
...and it wont have any effect on an approach unless, once again, the PF's scan rate fails and he allows the speed to approach the stall
Looks like a lot of good stuff for redundancy/safety.
Cheers.
...and it will provide G/A thrust upon TOGA for a go-around (which of course the PF will back up anyway and not forget!)
...and it wont have any effect on an approach unless, once again, the PF's scan rate fails and he allows the speed to approach the stall
Looks like a lot of good stuff for redundancy/safety.
Cheers.
Thread Starter
Wellll......
Gald, it's interesting that you mentioned it not being a good idea to have A/P off, A/T on- I agree entirely, but you might recall that this was ALSO a practice used at our erstwhile employer (in fact, BOTH our previous mutual employers!)
I took that with me to Blighty, and it almost bit me in the arse, demonstrating it to an F/O onto a short runway on a Greek Island, the supposed advantage being you could carry the minimum 5kt additive regardless of wind.
For reasons unknown, the A/T decided not to go into "retard" at the appropriate RAD ALT, instead INCREASING thrust to try and keep VAPP.
One of them "the time I probably should have gone-round but didn't" moments!!!!
My point being, the old automatics in the classic-slug can be a bit unpredictable, so I'm still a little wary of having them on in ANY mode near the ground.
Gald, it's interesting that you mentioned it not being a good idea to have A/P off, A/T on- I agree entirely, but you might recall that this was ALSO a practice used at our erstwhile employer (in fact, BOTH our previous mutual employers!)
I took that with me to Blighty, and it almost bit me in the arse, demonstrating it to an F/O onto a short runway on a Greek Island, the supposed advantage being you could carry the minimum 5kt additive regardless of wind.
For reasons unknown, the A/T decided not to go into "retard" at the appropriate RAD ALT, instead INCREASING thrust to try and keep VAPP.
One of them "the time I probably should have gone-round but didn't" moments!!!!
My point being, the old automatics in the classic-slug can be a bit unpredictable, so I'm still a little wary of having them on in ANY mode near the ground.
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There must be someone with a conduit into the Boeing B737 development department who can ask 'the horse's mouth' and relay the words of wisdom to us all: the technical reasons, not just a "we haven't thought about it too much so think it's not for best......"
There are other 'not recommended' techniques mentioned which I've not fully understood the thinking behind. I've tried their use in the sim and they worked fine and made life easier in an engine failure case; and I failed, via the in-house tech dept, to find out the reasoning. The tech dept wasn't interested and so didn't pursue the issue, just forbade it.
There are other 'not recommended' techniques mentioned which I've not fully understood the thinking behind. I've tried their use in the sim and they worked fine and made life easier in an engine failure case; and I failed, via the in-house tech dept, to find out the reasoning. The tech dept wasn't interested and so didn't pursue the issue, just forbade it.
Last edited by RAT 5; 19th Nov 2017 at 08:30.
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Welll...right back at ya!
Our second mutual had many quirks for many reasons in the overall operation, the first somewhat more SOP orientated....with relatively good to great training IMHO.
I honestly have no recollection of split active auto modes - ie A/P off but A/T on, that's always a no no and only takes seeing someone in the SIM pushing and pulling the yoke (manual flight) and the A/T (auto) advancing and retarding in response to the pitch changes and the whole thing just getting worse...and worse...very untidy.
It was always:
- "deselect speed" (A/T in ARM/redundancy mode so NOT active), then
- "disconnect autopilot".
End up with Manual flight, Manual thrust, Alpha floor protection available and Go Around thrust available via TOGA.
Beautiful....as only Boeing can!
Cheers.
PS: once we've sorted A/T ARM we can talk about the magnificence that is CWS!
Our second mutual had many quirks for many reasons in the overall operation, the first somewhat more SOP orientated....with relatively good to great training IMHO.
I honestly have no recollection of split active auto modes - ie A/P off but A/T on, that's always a no no and only takes seeing someone in the SIM pushing and pulling the yoke (manual flight) and the A/T (auto) advancing and retarding in response to the pitch changes and the whole thing just getting worse...and worse...very untidy.
It was always:
- "deselect speed" (A/T in ARM/redundancy mode so NOT active), then
- "disconnect autopilot".
End up with Manual flight, Manual thrust, Alpha floor protection available and Go Around thrust available via TOGA.
Beautiful....as only Boeing can!
Cheers.
PS: once we've sorted A/T ARM we can talk about the magnificence that is CWS!
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...but it will "wake up" on a dark night, scud-running min wx approach at 600 ft if the PF's scan rate fails and he allows the speed to approach the stall
...and it will provide G/A thrust upon TOGA for a go-around (which of course the PF will back up anyway and not forget!)
...and it wont have any effect on an approach unless, once again, the PF's scan rate fails and he allows the speed to approach the stall
Looks like a lot of good stuff for redundancy/safety.
Cheers.
...and it will provide G/A thrust upon TOGA for a go-around (which of course the PF will back up anyway and not forget!)
...and it wont have any effect on an approach unless, once again, the PF's scan rate fails and he allows the speed to approach the stall
Looks like a lot of good stuff for redundancy/safety.
Cheers.
4 eyes should be sufficient to have all these wonderful protections for about 40 seconds (let’s assume You disconnect the automatics at 500ft or so).
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B737C525
Quite correct, my apologies for incorrect terminology: Minimum Speed Reversion is what I should have written.
sonicbum
Well in some operations/cultures in those 40 seconds the PM will probably have to set a missed approach heading, set a missed approach altitude, de-select and re-select Flight Directors whilst (maybe) responding to various other PF directives and random ATC comms.
His actions may not be limited to solely monitoring instruments and calling deviations.
Easy enough for both PF and PM to get distracted at inconvenient times, another case of "beautiful SIM script" Vs "all hell breaking loose" at times in the real world.
Surely a bit of redundancy isn't going to DECREASE safety?
Quite correct, my apologies for incorrect terminology: Minimum Speed Reversion is what I should have written.
sonicbum
Well in some operations/cultures in those 40 seconds the PM will probably have to set a missed approach heading, set a missed approach altitude, de-select and re-select Flight Directors whilst (maybe) responding to various other PF directives and random ATC comms.
His actions may not be limited to solely monitoring instruments and calling deviations.
Easy enough for both PF and PM to get distracted at inconvenient times, another case of "beautiful SIM script" Vs "all hell breaking loose" at times in the real world.
Surely a bit of redundancy isn't going to DECREASE safety?
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B737C525
Quite correct, my apologies for incorrect terminology: Minimum Speed Reversion is what I should have written.
sonicbum
Well in some operations/cultures in those 40 seconds the PM will probably have to set a missed approach heading, set a missed approach altitude, de-select and re-select Flight Directors whilst (maybe) responding to various other PF directives and random ATC comms.
His actions may not be limited to solely monitoring instruments and calling deviations.
Easy enough for both PF and PM to get distracted at inconvenient times, another case of "beautiful SIM script" Vs "all hell breaking loose" at times in the real world.
Surely a bit of redundancy isn't going to DECREASE safety?
Quite correct, my apologies for incorrect terminology: Minimum Speed Reversion is what I should have written.
sonicbum
Well in some operations/cultures in those 40 seconds the PM will probably have to set a missed approach heading, set a missed approach altitude, de-select and re-select Flight Directors whilst (maybe) responding to various other PF directives and random ATC comms.
His actions may not be limited to solely monitoring instruments and calling deviations.
Easy enough for both PF and PM to get distracted at inconvenient times, another case of "beautiful SIM script" Vs "all hell breaking loose" at times in the real world.
Surely a bit of redundancy isn't going to DECREASE safety?
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This discussion began with a question about the 737-3/400. I can only speak to the 737-800, although I believe there is great similarity in the autoflight systems.
Regarding alpha floor protection, the Boeing FCOM states: “alpha floor protection automatically engages the A/T when armed.” Can’t be much plainer than that. That said, this reminds me a bit of my insurance company claiming that they will cover the damage to a rental car. Haven’t tested it yet to see what actually happens when I crash the rental car…and I have no intention of testing the alpha floor.
Minimum speed reversion appears to be a mix of pitch and power controls to return the airplane to a speed above whatever the minimum speed is. Alpha floor is not defined anywhere except in the above statement, but appears to only an A/T mode.
Regarding the split in automation, my strong opinion coming off the 767/757 and MD80 before that was autopilot off, autothrottles off. I still prefer to fly that way for all of the reasons cited above, and have often invoked Boeing’s admonition on this topic. However, in 2006 Boeing’s Captain Mike Bryan produced a presentation at their annual operators’ forum which questioned that premise. He showed quite a bit of flight test data indicating a much better and more precise speed control in gusty crosswinds, etc. with autothrottles on during manual flight.
Unfortunately, in 2008, my access to Boeing’s operator forums and associated presentations was summarily cut off (airline folded). So I don’t know what else they may have done with this issue…perhaps some of the other graybeards on this forum might. BUT…regardless of personal tastes and historical recommendations, I am now required to manually fly a CAT III approach using the HUD…with the autothrottles on through the touchdown. So it’s a little hard to support the notion that there is something inherently unsafe about splitting the automation.
Regarding the retard action in the flare, I certainly can see Wizofoz’s experience on the Greek island happening. We were drilled on the importance of manually closing the throttles during the flare…except during the aforementioned CAT III…even if they are active. The primary issue here seems to be the relationship between landing with power and tailstrikes.
Centaurus’s description of the pitch up during go-around is a bit alarming, because despite the ground school guys talking about the second TOGA push, etc., nobody ever demonstrated that in the sim. I can recall disconnecting the A/P on the MD80 during a couple of real world go-arounds because I was pretty sure the A/P had entered the low-level loop mode. This is a something to be aware of for sure.
Regarding alpha floor protection, the Boeing FCOM states: “alpha floor protection automatically engages the A/T when armed.” Can’t be much plainer than that. That said, this reminds me a bit of my insurance company claiming that they will cover the damage to a rental car. Haven’t tested it yet to see what actually happens when I crash the rental car…and I have no intention of testing the alpha floor.
Minimum speed reversion appears to be a mix of pitch and power controls to return the airplane to a speed above whatever the minimum speed is. Alpha floor is not defined anywhere except in the above statement, but appears to only an A/T mode.
Regarding the split in automation, my strong opinion coming off the 767/757 and MD80 before that was autopilot off, autothrottles off. I still prefer to fly that way for all of the reasons cited above, and have often invoked Boeing’s admonition on this topic. However, in 2006 Boeing’s Captain Mike Bryan produced a presentation at their annual operators’ forum which questioned that premise. He showed quite a bit of flight test data indicating a much better and more precise speed control in gusty crosswinds, etc. with autothrottles on during manual flight.
Unfortunately, in 2008, my access to Boeing’s operator forums and associated presentations was summarily cut off (airline folded). So I don’t know what else they may have done with this issue…perhaps some of the other graybeards on this forum might. BUT…regardless of personal tastes and historical recommendations, I am now required to manually fly a CAT III approach using the HUD…with the autothrottles on through the touchdown. So it’s a little hard to support the notion that there is something inherently unsafe about splitting the automation.
Regarding the retard action in the flare, I certainly can see Wizofoz’s experience on the Greek island happening. We were drilled on the importance of manually closing the throttles during the flare…except during the aforementioned CAT III…even if they are active. The primary issue here seems to be the relationship between landing with power and tailstrikes.
Centaurus’s description of the pitch up during go-around is a bit alarming, because despite the ground school guys talking about the second TOGA push, etc., nobody ever demonstrated that in the sim. I can recall disconnecting the A/P on the MD80 during a couple of real world go-arounds because I was pretty sure the A/P had entered the low-level loop mode. This is a something to be aware of for sure.
Last edited by Mansfield; 19th Nov 2017 at 12:23.
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He showed quite a bit of flight test data indicating a much better and more precise speed control in gusty crosswinds, etc. with autothrottles on during manual flight.
That is not what I would have expected. I found on gusty automatic ILS's the A/T was a little sluggish and they gave a large thrust input which resulted in a trim change etc. etc. It was always lagging behind the a/c. On the other hand in manual flight, the inbuilt human sensors were operating ahead of the a/c and trends, and making gentle corrections much sooner with less power/pitch couple trim problems. Given that, on a gusty day, Vref usually had some add-on, I'd set a datum thrust and let the speed bounce up/down and leave N1% alone. My 'floor' was Vref not MCP speed. And quite often, if there was a smart reduction in speed you could sometimes sense it was about to be reversed and so did very little. I'm not sure the A/T was good at anticipation.
That is not what I would have expected. I found on gusty automatic ILS's the A/T was a little sluggish and they gave a large thrust input which resulted in a trim change etc. etc. It was always lagging behind the a/c. On the other hand in manual flight, the inbuilt human sensors were operating ahead of the a/c and trends, and making gentle corrections much sooner with less power/pitch couple trim problems. Given that, on a gusty day, Vref usually had some add-on, I'd set a datum thrust and let the speed bounce up/down and leave N1% alone. My 'floor' was Vref not MCP speed. And quite often, if there was a smart reduction in speed you could sometimes sense it was about to be reversed and so did very little. I'm not sure the A/T was good at anticipation.
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RAT 5, that is exactly what I would have expected. I can't post the powerpoint, but essentially he shows quite a bit more dynamic N1 variation with the autothrottles OFF vs. ON. In the one test condition that he cites airspeed data for, he shows an average of Vref+9 and a max of Vref+20 (with A/T on and bug set at Vref+5), compared to an average of Vref+18 with a max of Vref+31 (with A/T off and bug set at Vref+12 for wind additives).
I cannot yet speak from any experience on this ship, but like you, I have always found that I could do quite nicely with manual throttles. I don't know what my actual profiles would have looked like, but to me, running the throttles is just part of that pilot stuff. However, if nothing else, I think Bryan's argument is that the recommendation to turn A/T off when A/P is off probably can't be sustained for any good reason. Nothing in the Boeing manuals says we can't go all manual like we have always done. But the main argument that I have heard from our training folks is that with A/T off, you must add the wind additives to Vref+5, whereas with A/T on, you do not need to do this. Apparently, this is some kind of revelation...although I could swear it's been in the Boeing manuals since the beginning of time.
Now that I think about it, I think I smell the TALPA people around somewhere...
I cannot yet speak from any experience on this ship, but like you, I have always found that I could do quite nicely with manual throttles. I don't know what my actual profiles would have looked like, but to me, running the throttles is just part of that pilot stuff. However, if nothing else, I think Bryan's argument is that the recommendation to turn A/T off when A/P is off probably can't be sustained for any good reason. Nothing in the Boeing manuals says we can't go all manual like we have always done. But the main argument that I have heard from our training folks is that with A/T off, you must add the wind additives to Vref+5, whereas with A/T on, you do not need to do this. Apparently, this is some kind of revelation...although I could swear it's been in the Boeing manuals since the beginning of time.
Now that I think about it, I think I smell the TALPA people around somewhere...
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I started my B737 life in an operator that actively used A/T in 'speed off' mode on a manual approach. No issues, ever, despite coming from an utter dinosaur of a smaller jet.
I continued with another operator, a few years later, where the same practice was common place. Never any issues there, initially, and we flew plenty of challenging trips, and not a few go arounds which were non-events, using an A/T Armed/speed off setting. Then the training department started to change its culture, and along with protracted wordy briefings came the dictate that 'speed off' was not only no longer to be used, but was expressly forbidden. Why? Because Boeing said it Must Never be used. Oddly, training manuals didn't really reflect this, and after many queries from folks who'd never had any issues with 'speed off', a supporting 'memo' was supplied which quoted an extract from Boeing. The exact words were curious, and the main gist being that while Boeing 'does not recommend...', this had been interpreted as 'Boeing recommends do not...', and thus Boeing 'forbids...'
I moved on through several different types and operators for a few years, including one 737 operator where their go-around SOP had the PF reengaging the A/T, and the PM checking that it had been reengaged-
Here's the mouth music-
but found myself back on a B737 in Europe after 6 years, with a company that happily encouraged the use of 'speed- off', but also accepted A/T off if preferred. And so life continued for a short period of time until some folks from a Golden-harp operation took over a UK located/EI AOC, and all of a sudden, an edict was passed that clearly stated that A/T MUST be turned off, and that 'speed-off' must NEVER be used, and as further fact supporting this, an extract of a Boeing statement was issued as part of a flying notice. The old familiar words 'Boeing does not recommend...' being interpreted to state 'Boeing recommends do not...' and that the use of 'speed-off' is expressly forbidden (ostensibly, by Boeing). Along with this came an implied threat that anything else would be seen as a deliberate breach of SOP.
I'm now with another operator where this very same 'interpretation' of the by now familiar Boeing memo exists, but with a caveat that it doesn't apply if there is appropriate training in place to cover the use of 'speed-off'
I've seen plenty of notes and ops manual entries, etc, where the recommendation of completely turning off the autothrottle when flying manually is concerned, and I've seen plenty of extracts quoted regarding the 'Boeing does not recommend' or similar. But if Boeing really did forbid its use, why would there be a caveat about the training of its use? Why would the system still allow its selection (..or deselection)?
To me, it strikes me that a rigid, but flawed, interpretation of a memo addressing a 'general' technique has led to an equally rigid and somewhat flawed SOP and a degradation of the operation.
but that's just me.
I continued with another operator, a few years later, where the same practice was common place. Never any issues there, initially, and we flew plenty of challenging trips, and not a few go arounds which were non-events, using an A/T Armed/speed off setting. Then the training department started to change its culture, and along with protracted wordy briefings came the dictate that 'speed off' was not only no longer to be used, but was expressly forbidden. Why? Because Boeing said it Must Never be used. Oddly, training manuals didn't really reflect this, and after many queries from folks who'd never had any issues with 'speed off', a supporting 'memo' was supplied which quoted an extract from Boeing. The exact words were curious, and the main gist being that while Boeing 'does not recommend...', this had been interpreted as 'Boeing recommends do not...', and thus Boeing 'forbids...'
I moved on through several different types and operators for a few years, including one 737 operator where their go-around SOP had the PF reengaging the A/T, and the PM checking that it had been reengaged-
Here's the mouth music-
PF: 'go-around, flap-15, set go-around thrust' (PF sets A/T switch)
I'm now with another operator where this very same 'interpretation' of the by now familiar Boeing memo exists, but with a caveat that it doesn't apply if there is appropriate training in place to cover the use of 'speed-off'
I've seen plenty of notes and ops manual entries, etc, where the recommendation of completely turning off the autothrottle when flying manually is concerned, and I've seen plenty of extracts quoted regarding the 'Boeing does not recommend' or similar. But if Boeing really did forbid its use, why would there be a caveat about the training of its use? Why would the system still allow its selection (..or deselection)?
To me, it strikes me that a rigid, but flawed, interpretation of a memo addressing a 'general' technique has led to an equally rigid and somewhat flawed SOP and a degradation of the operation.
but that's just me.
Join Date: Jun 2000
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Lance, I think you've come across some folks who think they know everything & don't have the time or interest to question or consider what they don't think has any necessity. Sadly they are happy to either live in the dark or reinvent the wheel.
