FLCH
Capn B: In those immortal words of the redheaded dingbat from the otherside of the continent; "please explain"
What is it that you consider I am "defending"
Are you talking about my first post, or the second.
Maui
What is it that you consider I am "defending"
Are you talking about my first post, or the second.
Maui
The second, Maui...
Although I'm surprised that you say you prefer FLCH for arrivals given you (the PF) has no control whatsoever over the descent rate that results from using FLCH, as the Thais have shown on two occasions in Melbourne.
Although I'm surprised that you say you prefer FLCH for arrivals given you (the PF) has no control whatsoever over the descent rate that results from using FLCH, as the Thais have shown on two occasions in Melbourne.
Gender Faculty Specialist
Well that's not quiet accurate either. In FLCH the aurothrottle is in arm. It's not a terribly difficult thing to add a bit of thrust or take a bit off thus varying your vertical speed.
Capn. B
I started to respond but finger trouble and other activities got in the way. Chesty has partly covered what I intended.
Your claim that, in FLCH you have no control over V/S is totally erroneous. In FLCH you have total control over V/S, but not as “a set and forget”.
On a short descent (2-2.5 minutes rings a bell, but I would not swear to it), the auto throttle will reduce to accommodate as far back as idle. Once it gets to idle, or if the descent is going to be for a longer period, the auto throttle, as designated on the FMA, will go into HOLD. This means “I can no longer achieve what you want with my limited parameters, you sort it out and I will stay in standby” i.e. “your thrust levers”. When approaching the selected altitude, the autopilot will raise the nose in an ALT CAP mode and the auto throttle will wake up and set the appropriate power for the selected airspeed.
During the descent, which will have the IAS nailed, you may vary the ROD by use of ; increased speed if you have no limitations or by increased drag from the boards if you are speed limited.
I reiterate, you have total control of both airspeed and V/S, but you have to control it, no fancy dial to set.There are many places outside the free open spaces of Western Australia, where speed control is paramount. Places where if you fail to adhere to speed restrictions you will massively screw up the traffic flow. c.f. LAX “reduce to 210 knots THEN descend to……….”
Try running over designated speed into any one of dozens of busy places and you run the risk of immediate sanctions, such as spitting you out into a hold.
Speed in a lot of places is paramount. But that all relates to my first post.
You claim that my second post is indefensible and “a stupid idea period”.
As you don’t identify which you think is indefensible lets look at it point by point.
Why would you reset to missed approach altitude before you have captured G/S?
Well, why would you? If you have a clearance to an altitude, and a clearance to conduct the ILS, the altitude is a hard limit until you have established on the G/S. Is it not a prudent thing to do, to set the limiting altitude until that limit is removed by intercepting the G/S? If you don’t there is a possibility that you will bust the altitude restriction. I reckon there is a pretty good chance that your FCOM will tell you that this is the way to do it.
Why would you ignore the flight director without making some compensation for what is inevitable?
If you want to go manual fine, I would encourage it, (too much reliance on misunderstood automatics). But once off auto, for pity’s sake fly the aeroplane. If the Flight director is giving a cue, why not assess it as a valid data input, to be assessed along with all other inputs. There are occasions when it is valid and appropriate to look through the F/D but in doing so you must keep situational awareness, when the F/D says to you “you are not doing what you asked me to do” do you really want to go down this path’?
Why would you not invoke airmanship and awareness?
Another indefensible statement???
Is it not a reasonable assumption that, before disengaging the autopilot, the brain should be engaged?
Indefensible ? As Mr McEnroe said “you cannot be serious.
The problems with automatics arise when people try to do things differently to that which was designed, and/or, do things with little or no understanding of how it works.
For a lot of that, our training organisations and regulators must take a lot of the blame.The good part of it all is that in most circumstances, if you follow the FCOM you will be safe.
But you already know that so why the aggressive response.
BTW, do you still have an IAS hold on the 717? Genuine question.
Maui
I started to respond but finger trouble and other activities got in the way. Chesty has partly covered what I intended.
Your claim that, in FLCH you have no control over V/S is totally erroneous. In FLCH you have total control over V/S, but not as “a set and forget”.
On a short descent (2-2.5 minutes rings a bell, but I would not swear to it), the auto throttle will reduce to accommodate as far back as idle. Once it gets to idle, or if the descent is going to be for a longer period, the auto throttle, as designated on the FMA, will go into HOLD. This means “I can no longer achieve what you want with my limited parameters, you sort it out and I will stay in standby” i.e. “your thrust levers”. When approaching the selected altitude, the autopilot will raise the nose in an ALT CAP mode and the auto throttle will wake up and set the appropriate power for the selected airspeed.
During the descent, which will have the IAS nailed, you may vary the ROD by use of ; increased speed if you have no limitations or by increased drag from the boards if you are speed limited.
I reiterate, you have total control of both airspeed and V/S, but you have to control it, no fancy dial to set.There are many places outside the free open spaces of Western Australia, where speed control is paramount. Places where if you fail to adhere to speed restrictions you will massively screw up the traffic flow. c.f. LAX “reduce to 210 knots THEN descend to……….”
Try running over designated speed into any one of dozens of busy places and you run the risk of immediate sanctions, such as spitting you out into a hold.
Speed in a lot of places is paramount. But that all relates to my first post.
You claim that my second post is indefensible and “a stupid idea period”.
As you don’t identify which you think is indefensible lets look at it point by point.
Why would you reset to missed approach altitude before you have captured G/S?
Well, why would you? If you have a clearance to an altitude, and a clearance to conduct the ILS, the altitude is a hard limit until you have established on the G/S. Is it not a prudent thing to do, to set the limiting altitude until that limit is removed by intercepting the G/S? If you don’t there is a possibility that you will bust the altitude restriction. I reckon there is a pretty good chance that your FCOM will tell you that this is the way to do it.
Why would you ignore the flight director without making some compensation for what is inevitable?
If you want to go manual fine, I would encourage it, (too much reliance on misunderstood automatics). But once off auto, for pity’s sake fly the aeroplane. If the Flight director is giving a cue, why not assess it as a valid data input, to be assessed along with all other inputs. There are occasions when it is valid and appropriate to look through the F/D but in doing so you must keep situational awareness, when the F/D says to you “you are not doing what you asked me to do” do you really want to go down this path’?
Why would you not invoke airmanship and awareness?
Another indefensible statement???
Is it not a reasonable assumption that, before disengaging the autopilot, the brain should be engaged?
Indefensible ? As Mr McEnroe said “you cannot be serious.
The problems with automatics arise when people try to do things differently to that which was designed, and/or, do things with little or no understanding of how it works.
For a lot of that, our training organisations and regulators must take a lot of the blame.The good part of it all is that in most circumstances, if you follow the FCOM you will be safe.
But you already know that so why the aggressive response.
BTW, do you still have an IAS hold on the 717? Genuine question.
Maui
You claim that my second post is indefensible and “a stupid idea period”.
Fair enough pilots was supposed to be able to fly, but why oh why would you design the ATS like that?
As for your smart-arsed comment re WA, spare me the Big Jet Airways warries.
BTW, do you still have an IAS hold on the 717? Genuine question.
Capn. B
Please make up your mind. In response to my question, you said it was the second post that was “a stupid idea, period”. With the dubious nature of your assertion queried, you are now claiming reference to the first post.
I have no problem and no shame in defending a sound design that when used in accordance with the FCOM, and proven SOP’s, is a good and reliable bit of kit.
I do however, have difficulties with any person who, whether through ignorance or deliberate will, fails to follow those procedures, and gets themselves into strife.
In the case of the former, the training/checking establishment should have a case to answer.
In the case of the latter; if you want to venture into test pilot territory, be aware of the risks, and it’s all on your head when it bites you.
Your comment regarding stall and A/T non response is, to the best of my knowledge and experience, without foundation or substance. When operated in accordance with FCOM the A/T will wake up when required.
If you are aware of a circumstance where an A/T will not/has not woken up, having followed FCOM procedure and approved SOP’s, please enlighten us.
You, as an experienced aviator, would be aware of many things occurring that invoke the question “why would he/she do that”.
“Because he/she CAN”, is not an appropriate rationale.
How far do you expect the manufacturers to go, to cover all possibilities of deliberate or ignorant mishandling?
Would we ever have a new aircraft, with an industry philosophy of full idiot proofing.
The query re the 717 was because I understood that you operate one, and I am curious to know whether or not the IAS hold function was carried over from the MD80 series.
Maui
Please make up your mind. In response to my question, you said it was the second post that was “a stupid idea, period”. With the dubious nature of your assertion queried, you are now claiming reference to the first post.
I have no problem and no shame in defending a sound design that when used in accordance with the FCOM, and proven SOP’s, is a good and reliable bit of kit.
I do however, have difficulties with any person who, whether through ignorance or deliberate will, fails to follow those procedures, and gets themselves into strife.
In the case of the former, the training/checking establishment should have a case to answer.
In the case of the latter; if you want to venture into test pilot territory, be aware of the risks, and it’s all on your head when it bites you.
Your comment regarding stall and A/T non response is, to the best of my knowledge and experience, without foundation or substance. When operated in accordance with FCOM the A/T will wake up when required.
If you are aware of a circumstance where an A/T will not/has not woken up, having followed FCOM procedure and approved SOP’s, please enlighten us.
You, as an experienced aviator, would be aware of many things occurring that invoke the question “why would he/she do that”.
“Because he/she CAN”, is not an appropriate rationale.
How far do you expect the manufacturers to go, to cover all possibilities of deliberate or ignorant mishandling?
Would we ever have a new aircraft, with an industry philosophy of full idiot proofing.
The query re the 717 was because I understood that you operate one, and I am curious to know whether or not the IAS hold function was carried over from the MD80 series.
Maui
Last edited by maui; 18th Mar 2019 at 05:20.
Your comment regarding stall and A/T non response is, to the best of my knowledge and experience, without foundation or substance.
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For those of us engineers I suggest thinking about all pitch axis control as a matter of managing energy.
- Kinetic energy is that associated with speed
- Potential energy is that associated with altitude
The throttles and speedbrakes are used to add, maintain, or reduce energy.
The elevators are used to apportion energy between speed (kinetic) and vertical path (potential).
At all times you want to make sure you know who is minding the store with regard to both energy and how that energy is divided between speed and path.
FLCH is a way to use the elevator to control speed while the throttles / speedbrakes are fixed with extra energy going into climb or decaying energy coming from descent.
One of the keys with any transition mode of the autopilot (FLCH being one) is understanding what the next transition will be as the climb or descent clearly cannot go on indefinitely.
- When we get to a target altitude or path (such as glideslope), who takes over speed control and who takes over path control (i.e., automation modes that will engage)?
- If my target altitude or the glideslope is such that I am already above it and climbing or below it and descending, what happens next?
I'm not a pilot, so those who sit in Row 0 are the experts on the details of operating autopilot and autothrottle modes on specific airplanes, certainly not me. I just offer this as a bit of physics side thought that might bring clarity to some.
- Kinetic energy is that associated with speed
- Potential energy is that associated with altitude
The throttles and speedbrakes are used to add, maintain, or reduce energy.
The elevators are used to apportion energy between speed (kinetic) and vertical path (potential).
At all times you want to make sure you know who is minding the store with regard to both energy and how that energy is divided between speed and path.
FLCH is a way to use the elevator to control speed while the throttles / speedbrakes are fixed with extra energy going into climb or decaying energy coming from descent.
One of the keys with any transition mode of the autopilot (FLCH being one) is understanding what the next transition will be as the climb or descent clearly cannot go on indefinitely.
- When we get to a target altitude or path (such as glideslope), who takes over speed control and who takes over path control (i.e., automation modes that will engage)?
- If my target altitude or the glideslope is such that I am already above it and climbing or below it and descending, what happens next?
I'm not a pilot, so those who sit in Row 0 are the experts on the details of operating autopilot and autothrottle modes on specific airplanes, certainly not me. I just offer this as a bit of physics side thought that might bring clarity to some.
Capn. B
Asiana 214 is hardly an appropriate case to respond to my question.
(following in itallics, extracts from NTSB AAR 14/01 with my bolding and underlining).
You stated;
“You are defending the Boeing design feature that allows the ATS to stay asleep as the aircraft stalls.”
The aircraft did not stall, but anyway;
They were in FLCH and below 100 feet. The auto thrust behaved as advised.
Refer to the underlined part of my question.Having failed to follow SOP, the bigger question is “why did the crew not intervene to avoid”?
Mode awareness anyone!
Three factors any of which, would probably have averted the incident viz. Inappropriate mode selection, unstable approach procedure, and proper recycling of the F/D switches.
None of these were in Boeings control.
The aeroplane didn’t do anything that wasn’t documented, or should be unexpected.
I reiterate my previous statement:
In the meantime;
“If you are aware of a circumstance where an A/T will not/has not woken up, having followed FCOM procedure and approved SOP’s, please enlighten us."
Maui
Asiana 214 is hardly an appropriate case to respond to my question.
“If you are aware of a circumstance where an A/T will not/has not woken up, having followed FCOM procedure and approved SOP’s, please enlighten us.”
You stated;
“You are defending the Boeing design feature that allows the ATS to stay asleep as the aircraft stalls.”
The aircraft did not stall, but anyway;
Note: When the pitch mode is FLCH or TOGA, or the airplane is below 400 feet above the airport on takeoff, or below 100 feet radio altitude on approach, the autothrottle will not automatically activate.
The same student stated that another instructor had provided similar information during another 777 ground school class attended by the PF and advised students that they should not use FLCH to descend after crossing the FAF.
The flight crew's difficulty in managing the airplane's descent continued as the approach continued. In an attempt to increase the airplane's descent rate and capture the desired glidepath, the pilot flying (PF) selected an autopilot (A/P) mode (flight level change speed [FLCH SPD]) that instead resulted in the autoflight system initiating a climb because the airplane was below the selected altitude. The PF disconnected the A/P and moved the thrust levers to idle, which caused the autothrottle (A/T) to change to the HOLD mode, a mode in which the A/T does not control airspeed. {But the elevators do} The PF then pitched the airplane down and increased the descent rate. Neither the PF, the pilot monitoring (PM), nor the observer noted the change in A/T mode to HOLD.
The FLCH SPD pitch mode is used to change flight level, and, just as with the V/S mode, the pilot may use this mode to climb or descend to the altitude set in the MCP. However, in this mode, the elevator commands from the AFDS maintain the MCP target speed, while the climb or descent rate (vertical speed) is controlled by an increase or decrease in thrust through A/T control or manual pilot control.
The flight crew did not consistently adhere to Asiana's SOPs involving selections and callouts pertaining to the autoflight system's mode control panel. This lack of adherence is likely the reason that the PF did not call out "flight level change" when he selected FLCH SPD. As a result, and because the PM's attention was likely on changing the flap setting at that time, the PM did not notice that FLCH SPD was engaged.
During the accident flight, after the A/P was disconnected, the PM loosely followed Asiana's informal practice, which was to turn both flight directors (F/Ds) off and then turn the PM's F/D back on when conducting a visual approach. However, the two F/D switches were not both in the off position at the same time. If they had been, the A/T mode would have changed to speed mode and maintained the approach speed of 137 knots. In addition, during a visual approach, F/D pitch and roll guidance is not needed and can be a distraction.
The PF's faulty mental model of the airplane's automation logic led to his inadvertent deactivation of automatic airspeed control.
More manual flight for Asiana pilots. Asiana's automation policy emphasized the full use of all automation and did not encourage manual flight during line operations. . If the PF had been provided with more opportunity to manually fly the 777 during training, he would most likely have better used pitch trim, recognized that the airspeed was decaying, and taken the appropriate corrective action of adding power.
The National Transportation Safety Board (NTSB) determined that the probable cause of this accident was the flight crew's mismanagement of the airplane's descent during the visual approach, the PF's unintended deactivation of automatic airspeed control, the flight crew's inadequate monitoring of airspeed, and the flight crew's delayed execution of a go-around after they became aware that the airplane was below acceptable glidepath and airspeed tolerances. Contributing to the accident were (1) the complexities of the autothrottle and autopilot flight director systems that were inadequately described in Boeing's documentation and Asiana's pilot training, which increased the likelihood of mode error;……….
None of these were in Boeings control.
The aeroplane didn’t do anything that wasn’t documented, or should be unexpected.
I reiterate my previous statement:
if you want to venture into test pilot territory, be aware of the risks, and it’s all on your head when it bites you.
“If you are aware of a circumstance where an A/T will not/has not woken up, having followed FCOM procedure and approved SOP’s, please enlighten us."
Maui
Last edited by maui; 19th Mar 2019 at 03:06.
They were in FLCH and below 100 feet. The auto thrust behaved as advised.
At 200ft, the IAS was ~118, with a Vref of 132.
Originally Posted by Maui
having followed FCOM procedure and approved SOP’s
An autothrottle that doesn't wake up even when you're almost 20kts below Vapp is stupidly designed. Period. Stop defending the indefensible.
An interesting comment from one of the NTSB board members:
Data point number two comes in the form of an FAA test pilot. In 2010, this pilot was flying a Boeing 787 on a test flight when he was alarmed to see that the autothrottle did not maintain speed while in FLCH and HOLD. The autothrottle logic on the 787 is essentially the same as the 777, and this pilot had 500 hours in the 777. Why would an experienced FAA test pilot not understand this system logic if it was that clear? He raised his concern throughout the FAA certification chain. Officials with EASA also became concerned. As a result, Boeing added additional and clearer guidance in the Boeing 787 manuals regarding this system logic. But for the Boeing 777—an airplane with the same basic system—nothing was done.
As for using FLCH during an approach...
Capn.B
At last, I think I have identified the source of your angst. It is based on a misconception.
Simply not correct.
If you refer to the NTSB report 1.6.3.4 on pages 26 and 27, you will see a list of the circumstances in which the A/T will wake up out of HOLD. Hopefully this will allay your concern.
The basic premise of my comments was that if you follow the FCOM and SOP’s you will not get into any situation where the A/T will not wake up. What is difficult about that.
Approach 101.
If you follow FCOM and SOP’s, and If you have not yet captured the G/S you will have an altitude at or below your current level set.
Upon reaching that altitude the A/T WILL wake up and maintain ALT and SPD.
Upon transition to G/S, you may then select minima briefly then M/A alt.
This assumes you have the approach set up in your FMC and you are cleared to do so.
The aircraft will fly the profile both vertically and horizontally.
All that is required for you to do now is to configure and set speed as appropriate.
FLCH is no longer active once you capture the G/S or capture the platform ALT.
You are not in FLCH for the approach.
In the case of a visual approach, you can do all the same if you have and active ILS to help, or you can do it in VNAV or V/S if you have a published approach in the FMC.
Given that you are now in VMC you could also look out the window, and, heaven forbid, you could even fly manually in which case you should deal with the flight directors as described in the previous post.
If you are below the G/S when you select FLCH AND do not set a lower ALT you will get to the situation that you deem to be dangerous, and be in breach of FCOM and SOP.
I agree it is dangerous.
To my mind it is plain f..king stupid and beyond comprehension.
It is against FCOM and SOP’s.
Why would you do it?
As it is the only occasion that the A/T will leave you to determine your own fate, why is Boeing vilified for not putting in an idiot filter.
I repeat the challenge: If you know of any incident in this regard that has occurred after the crew have complied with FCOM and SOP’s, please tell us.
I am at a loss as to how any of this is relevant.
Are you suggesting that because you have these safety systems, you can forget about proper procedures, and just rely on the systems to keep you alive?
Good luck with that one.
Where do you want the donations sent in lieu of floral tribute.
It will only do what it is told to do. If you have set it up, and operate it as designed, follow FCOM and SOP, this question does not arise.
Even if you turn it OFF it will wake up at low speed, but if it sent into HOLD, by PF either directly or indirectly, it will do exactly that HOLD, until you tell it otherwise or it meets a selected altitude. (insert upon rereading; perhaps you misunderstand the meaning of HOLD. It relates to the autothrottle status, it does not indicate that it {auto thrust}will hold your speed. It is saying "your thrust sort it out yourself")
With regard to the FAA test pilot quote, you will note that just guidance material was made clearer. They didn’t see a need to change the hardware/software. And even test pilots screw it up on occasions.
I don’t believe I have ever advocated that.
You seem to have a flea in your ear about the 777 and possibly Boeing, I hope this will relieve the itch.
As a post script:
I spent a considerable amount of time thrashing around Asia/South East Asia./EuropeI/Pacific and US, I often commented to colleagues that I was amazed that despite the plethora of 777’s in service throughout those areas, for new and small airlines, with many crews with limited experience, there were very few serious incidents, and at that stage no accidents. That in itself, to my mind, is testimony to the integrity of the design.
By the way you still haven’t answered my question about the 717 IAS HOLD.
Maui
At last, I think I have identified the source of your angst. It is based on a misconception.
Red Herring. If in FLCH and HOLD, it looks to me like it will never automatically activate.
If you refer to the NTSB report 1.6.3.4 on pages 26 and 27, you will see a list of the circumstances in which the A/T will wake up out of HOLD. Hopefully this will allay your concern.
The basic premise of my comments was that if you follow the FCOM and SOP’s you will not get into any situation where the A/T will not wake up. What is difficult about that.
Approach 101.
If you follow FCOM and SOP’s, and If you have not yet captured the G/S you will have an altitude at or below your current level set.
Upon reaching that altitude the A/T WILL wake up and maintain ALT and SPD.
Upon transition to G/S, you may then select minima briefly then M/A alt.
This assumes you have the approach set up in your FMC and you are cleared to do so.
The aircraft will fly the profile both vertically and horizontally.
All that is required for you to do now is to configure and set speed as appropriate.
FLCH is no longer active once you capture the G/S or capture the platform ALT.
You are not in FLCH for the approach.
In the case of a visual approach, you can do all the same if you have and active ILS to help, or you can do it in VNAV or V/S if you have a published approach in the FMC.
Given that you are now in VMC you could also look out the window, and, heaven forbid, you could even fly manually in which case you should deal with the flight directors as described in the previous post.
If you are below the G/S when you select FLCH AND do not set a lower ALT you will get to the situation that you deem to be dangerous, and be in breach of FCOM and SOP.
I agree it is dangerous.
To my mind it is plain f..king stupid and beyond comprehension.
It is against FCOM and SOP’s.
Why would you do it?
As it is the only occasion that the A/T will leave you to determine your own fate, why is Boeing vilified for not putting in an idiot filter.
I repeat the challenge: If you know of any incident in this regard that has occurred after the crew have complied with FCOM and SOP’s, please tell us.
What's the TCAS, EGPWS, Takeoff Config Warning system for then? Or for that matter ABS in your car?
Are you suggesting that because you have these safety systems, you can forget about proper procedures, and just rely on the systems to keep you alive?
Good luck with that one.
Where do you want the donations sent in lieu of floral tribute.
An autothrottle that doesn't wake up even when you're almost 20kts below Vapp is stupidly designed. Period. Stop defending the indefensible.
Even if you turn it OFF it will wake up at low speed, but if it sent into HOLD, by PF either directly or indirectly, it will do exactly that HOLD, until you tell it otherwise or it meets a selected altitude. (insert upon rereading; perhaps you misunderstand the meaning of HOLD. It relates to the autothrottle status, it does not indicate that it {auto thrust}will hold your speed. It is saying "your thrust sort it out yourself")
With regard to the FAA test pilot quote, you will note that just guidance material was made clearer. They didn’t see a need to change the hardware/software. And even test pilots screw it up on occasions.
As for using FLCH during an approach.
Frankly it was my preferred (non STAR) mode for descent prior to G/S capture (from above), particularly when operating in a speed controlled environment.
As a post script:
I spent a considerable amount of time thrashing around Asia/South East Asia./EuropeI/Pacific and US, I often commented to colleagues that I was amazed that despite the plethora of 777’s in service throughout those areas, for new and small airlines, with many crews with limited experience, there were very few serious incidents, and at that stage no accidents. That in itself, to my mind, is testimony to the integrity of the design.
By the way you still haven’t answered my question about the 717 IAS HOLD.
Maui
Last edited by maui; 20th Mar 2019 at 01:03.
FCeng84
Congratulations. An excellent observation and summary. I hope it gives a lot of aviators food for thought.
Unfortunately there are a lot in the industry who assume that others have done all thinking for them, and rely implicitly on the automatics. Our training these days leaves a lot to be desired. A significant amount of training is on a need to know basis. The nice to know aspects that will stimulate critical thinking are scarcely available.
Maui
Congratulations. An excellent observation and summary. I hope it gives a lot of aviators food for thought.
Unfortunately there are a lot in the industry who assume that others have done all thinking for them, and rely implicitly on the automatics. Our training these days leaves a lot to be desired. A significant amount of training is on a need to know basis. The nice to know aspects that will stimulate critical thinking are scarcely available.
Maui
