CaptainLars

Trying to follow TCAS instructions...

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Hi,

the following happened to me when climbing out of Sheremetyevo 06L using the 777 freighter:

At approximately 2000ft, I got a traffic warning (in yellow). I looked out of the window and couldn't see anything. A few seconds later, I got the red traffic alert, the system telling me to descent, which I did, of course. Then "increase descent". At the end I descended with up to 5500ft/min and picked up a lot of speed, 335kts. Of couse, since the alarm silenced, I wanted to climb again, and that worked... 5500ft/min climb, the speed slowly coming down to 250kts again.

However, I didn't want to climb that fast, instead I would have preferred to do a more gentle climb, reducing power perhaps. But this was impossible. I pressed the yoke hard down, all the way, but the plane did not react, only to lateral input. I also wanted to reduce power, since we were so awefully fast, and I feared for the structural integrity of the plane (I think I even used speedbrakes in one moment), but this was impossible, too, and it wasn't possible to disconnect the Autothrottle.

So I guess that I met the Flight Envelop Protection. Is it correct that the plane behaves that way? I would have expected such behaviour in an Airbus, not in a Boeing. Would it have been possible to take *more* control of the aircraft by deactivating Flight Director and switching A/T totally off? A/P wasn't on after all.

I'd appreciate any input on this situation... tbh, it was a bit scary! :ohmy:

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When you changed from climb to descent you didn't describe the actions you took.  Did you cancel autopilot?  What about thrust mode?  How do you disconnect A/T?  Never necessary to deactivate FD.... it is not flying only guiding.

Give a scenario where I was climbing through 2000 feet, probably clean with N1 thrust and speed pitch (VNAV SPD) and had to descend, I would disconnect A/T and A/P then pull power off then nose down and keep the speed under control using speedbrakes if necessary until clear of alarm.  First rule of flying is fly the airplane first.

I have controller buttons programmed to disconnect A/P and A/T. 

I don't like AI traffic, very unrealistic, and never had this happen but I bet it woke you up.

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As a general point: a TCAS RA should never be a violent manoeuvre and it would be unusual that such a high rate of descent would be necessary. All that is necessary is to keep the VSI in the green region and/or pitch smoothly to avoid the red region on the PFD. -5500 fpm at 2000ft is not a place I would like to be!

Step 1 on receiving a TCAS RA is to disconnect both autopilot and autothrottle (FDs can stay on but must not be followed in pitch until clear of conflict). Can you normally disconnect the A/T in flight?

I'm afraid I don't know enough about the B777 flight control/protection systems to answer the rest of your question, sorry! 

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14 hours ago, CaptainLars said:

Hi,

the following happened to me when climbing out of Sheremetyevo 06L using the 777 freighter:

At approximately 2000ft, I got a traffic warning (in yellow). I looked out of the window and couldn't see anything. A few seconds later, I got the red traffic alert, the system telling me to descent, which I did, of course. Then "increase descent". At the end I descended with up to 5500ft/min and picked up a lot of speed, 335kts. Of couse, since the alarm silenced, I wanted to climb again, and that worked... 5500ft/min climb, the speed slowly coming down to 250kts again.

However, I didn't want to climb that fast, instead I would have preferred to do a more gentle climb, reducing power perhaps. But this was impossible. I pressed the yoke hard down, all the way, but the plane did not react, only to lateral input. I also wanted to reduce power, since we were so awefully fast, and I feared for the structural integrity of the plane (I think I even used speedbrakes in one moment), but this was impossible, too, and it wasn't possible to disconnect the Autothrottle.

So I guess that I met the Flight Envelop Protection. Is it correct that the plane behaves that way? I would have expected such behaviour in an Airbus, not in a Boeing. Would it have been possible to take *more* control of the aircraft by deactivating Flight Director and switching A/T totally off? A/P wasn't on after all.

I'd appreciate any input on this situation... tbh, it was a bit scary! :ohmy:

TCAS RA memory item is 

AP off and A/THR off

if you only disconnect A/P during initial climb out, your Thrust setting would still be in CLB thrust at that stage. 

Therefore with the pitch down command and the thrust at CLB thrust setting, your speed and rate of descend will run away very quickly. 

Once the TCAS is gone, your airplane had already carried a lot of overspeed from the previous nose down maneuver, if you raise you nose to back to you original climb out attitude ~8-9deg, you will get 5000+ ft rate of climb and it is normal. 

 

If you follow the TCAS memory item (which is manual thrust + manual flying) it would prevent you from getting into the scenario you experienced. 

 

Airbus TCAS RA memory item is autopilot off and FD off. This way the A/THR will be in SPD model, therefore would try to maintain the target airspeed of the airplane regardless of pitch command. 

 

When i I first came to the 777 from the airbus, I had once questioned why the 777 could not fly the TCAS RA maneuver in the Airbus way i.e switch off the FD only and force the A/THR mode into SPD mode.

Obviously the answer was Boeing needs to align TCAS RA memory items across all the Boeing aircrafts including the older 744 and 767 which used to have a policy of "manual flying must couple with manual thrust" 

 

 

 

 

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18 hours ago, downscc said:

When you changed from climb to descent you didn't describe the actions you took.  Did you cancel autopilot?  What about thrust mode?  How do you disconnect A/T?  Never necessary to deactivate FD.... it is not flying only guiding.

Give a scenario where I was climbing through 2000 feet, probably clean with N1 thrust and speed pitch (VNAV SPD) and had to descend, I would disconnect A/T and A/P then pull power off then nose down and keep the speed under control using speedbrakes if necessary until clear of alarm.  First rule of flying is fly the airplane first.

I have controller buttons programmed to disconnect A/P and A/T. 

I don't like AI traffic, very unrealistic, and never had this happen but I bet it woke you up.

I didn't have A/P engaged, so I immidiately followed the TCAS instructions. At first I didn't switch off A/T, only later. I have a button of my hardware throttle unit mapped to the A/T disengage button on the simulator throttles that I usually use for disconnecting A/T upon approach.

 

17 hours ago, skelsey said:

As a general point: a TCAS RA should never be a violent manoeuvre and it would be unusual that such a high rate of descent would be necessary. All that is necessary is to keep the VSI in the green region and/or pitch smoothly to avoid the red region on the PFD. -5500 fpm at 2000ft is not a place I would like to be!

Step 1 on receiving a TCAS RA is to disconnect both autopilot and autothrottle (FDs can stay on but must not be followed in pitch until clear of conflict). Can you normally disconnect the A/T in flight?

I'm afraid I don't know enough about the B777 flight control/protection systems to answer the rest of your question, sorry! 

Yes, at 2000ft I was still climbing. It was a curve that led me back to 2000ft at the end of the manoeuvre.

 

6 hours ago, Driverab330 said:

TCAS RA memory item is 

AP off and A/THR off

if you only disconnect A/P during initial climb out, your Thrust setting would still be in CLB thrust at that stage. 

Therefore with the pitch down command and the thrust at CLB thrust setting, your speed and rate of descend will run away very quickly. 

Once the TCAS is gone, your airplane had already carried a lot of overspeed from the previous nose down maneuver, if you raise you nose to back to you original climb out attitude ~8-9deg, you will get 5000+ ft rate of climb and it is normal. 

 

If you follow the TCAS memory item (which is manual thrust + manual flying) it would prevent you from getting into the scenario you experienced. 

 

Airbus TCAS RA memory item is autopilot off and FD off. This way the A/THR will be in SPD model, therefore would try to maintain the target airspeed of the airplane regardless of pitch command. 

 

When i I first came to the 777 from the airbus, I had once questioned why the 777 could not fly the TCAS RA maneuver in the Airbus way i.e switch off the FD only and force the A/THR mode into SPD mode.

Obviously the answer was Boeing needs to align TCAS RA memory items across all the Boeing aircrafts including the older 744 and 767 which used to have a policy of "manual flying must couple with manual thrust" 

Thank you very much for your detailed insight, and for confirming what Dan and Simon said.

 

What I see from your answers is that my "mistake" was not to disengage A/T right away and not using speedbrakes enough. Of course, the biggest fault was just trusting the ATC takeoff clearance when the aircraft on the parallel runway had just received T/O clearance, too.

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Right. 

Put it this way, the Boeing Memory items says very clearly the TCAS RA action is AP of + A/T off.

 

so I guess you were right, it would be your "mistake" for not disconnecting the A/T immediately after disconnecting the AP. 

 

But it unlike the real airplane where the A/T disconnect switch is placed at a very convenient location for quick disconnect of the A/T. There will inevitably delays in Flight sim. And this is not your fault unless you have a Boeiny style throttle quadrant. 

 

Just like I have mentioned above if you have a climbing attitude of 8-9deg with 85% N1 (usual CLB thrust settings), and you get a Descend RA command, the pitch change will be quite dramatic and any delay to pull back the thrust will lead to an overspeed. 

 

I didnt mentioned anyway about overspeed recovery in my post. So I did not comment on your use of speedbrake. 

 

If you try to replicate the same scenario again and the TCAS RA, see if you can effectively control the speed by taking out the A/T asap. 

There was an event similar to what you had encountered actually had happened to one of our company 777 takin off from SFO a few years back. 

They were climbing out from 28L and there was a VFR traffic crossing their flight path at ~3000ft which generated a descend and subsequent level off RA.

they too had a slight over speed due to a late disconnect of the A/T. 

 

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5 hours ago, Driverab330 said:

There was an event similar to what you had encountered actually had happened to one of our company 777 takin off from SFO a few years back. 

They were climbing out from 28L and there was a VFR traffic crossing their flight path at ~3000ft which generated a descend and subsequent level off RA.

they too had a slight over speed due to a late disconnect of the A/T. 

You mean this one?

 

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Not this one, but very similar.

This is a known problem for SFO for allowing VFR traffic into the departing corridor of a big international airport. 

 

 

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The good (since educating) thing about this is that I had recorded this event and now managed to form a video out of this that I uploaded to Youtube. Also I didn't know how to use the clock I think... Line-up is at 4:20, the traffic aural starts at 5:57.

 

Unfortunately, I deleted the corresponding savegame, but nonetheless I'll try to recreate that situation with your input in mind.

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On 16.9.2017 at 9:50 PM, CaptainLars said:

 

So I guess that I met the Flight Envelop Protection. Is it correct that the plane behaves that way? I would have expected such behaviour in an Airbus, not in a Boeing. Would it have been possible to take *more* control of the aircraft by deactivating Flight Director and switching A/T totally off? A/P wasn't on after all.

I'd appreciate any input on this situation... tbh, it was a bit scary! :ohmy:

 

The 777 is not a big friend of getting crashed and it will stay between spexific limits as soon as the pilot lets it. But, other than on an Airbus you are able to go into overspeed or even stall the airplane. You can disarm the autorhrottoes on the MCP and you can turn off the primary flight computers on the overhead panel. Bit that is nothing you would ever do to avoid a collision. Turn of the AP and the AT and do what TCAS tells you, but still use your brain, all above on Flightsim. --> the other aircraft is going to fly straight on, it will do nothing to avoid the crash 😆

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Well do you not have a reflex?

As soon as i need to fly THAT maneuver i would automatically disengage the A/T and pull them full back o.O i wonder that you could even achieve this descent rate with N1 at 92% and flaps 5.

In that situation a use of speedbrakes would even make sense for recovery.

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I'm so glad you would automatically do that, especially after having read the recommendations here.

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1 hour ago, CaptainLars said:

I'm so glad you would automatically do that, especially after having read the recommendations here.

:laugh:

after all the autopilot is nothing else than a  regulating control unit. It takes given values and corrects them with actions to come back to a specific target. When you are fast and pitching down it will pitch up and reduce throttle. The 777 has some protection systems, but, as this aircraft is really huge and heavy with some insanely huge engines, it is incredibly slow in doing anything. I have learnt to fly on a c172 that was equipped with a simple autopilot that mostly refused to do what you want it to do and most of the time it was overcorrecting. So as soon as you weren‘t absolutely sure about this evil part of automation you disconnected it and flew the aircraft with your brain and muscles. And that is exactly what you do on a triple 7 or an A330 when your in doubt of any action your AP is doing. Switch off any automation immediately and correct the situation manually. You are not as precise as those autopilots, but you are a lot faster and a lot more intelligent... :cool:

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On 10/2/2017 at 3:11 AM, CaptainLars said:

I'm so glad you would automatically do that, especially after having read the recommendations here.

Yes i definitely do that?! who the word not allowed rushes with climb thrust in 3000 feet altitude to the ground??

Further would a decrease in thrust reduce your pitch angle dramatically... You should normally never go above +30 or -10 degrees....

The only reason would be a stall recovery or maybe a windshear escape procedure....

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10 hours ago, 30K said:

Yes i definitely do that?! who the word not allowed rushes with climb thrust in 3000 feet altitude to the ground??

Further would a decrease in thrust reduce your pitch angle dramatically... You should normally never go above +30 or -10 degrees....

The only reason would be a stall recovery or maybe a windshear escape procedure....

I didn't rush to the ground, infact I tried to level off first, but the TCAS system kept advising me to descend. I thought that the A/T would be able to reduce thrust sufficiently on its own, but honestly, with the TCAS system urging me to descend because of another aircraft being about to land on the cockpit roof within a matter of seconds, I didn't think about the A/T.

 

On 2.10.2017 at 4:33 AM, Ephedrin said:

:laugh:

after all the autopilot is nothing else than a  regulating control unit. It takes given values and corrects them with actions to come back to a specific target. When you are fast and pitching down it will pitch up and reduce throttle. The 777 has some protection systems, but, as this aircraft is really huge and heavy with some insanely huge engines, it is incredibly slow in doing anything. I have learnt to fly on a c172 that was equipped with a simple autopilot that mostly refused to do what you want it to do and most of the time it was overcorrecting. So as soon as you weren‘t absolutely sure about this evil part of automation you disconnected it and flew the aircraft with your brain and muscles. And that is exactly what you do on a triple 7 or an A330 when your in doubt of any action your AP is doing. Switch off any automation immediately and correct the situation manually. You are not as precise as those autopilots, but you are a lot faster and a lot more intelligent... :cool:

Thank you for your comment, much appreciated.

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Well, two months later I think I did right. You can expect from an A/T to decrease speed in such a situation. I think that it's a bit less than perfectly programmed. Probably a bug. Of course, I have learned from this incident and am prepared now.

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3 hours ago, CaptainLars said:

Well, two months later I think I did right. You can expect from an A/T to decrease speed in such a situation. I think that it's a bit less than perfectly programmed. Probably a bug. Of course, I have learned from this incident and am prepared now.

It is absolutely, categorically not a bug, and I have to say I'm perplexed as to how you've reached that conclusion when several of us, including someone who flies the aeroplane for real, have  already explained to you that it's your technique at fault and not the aeroplane.

The AFDS is in THR REF | VNAV SPD for the climb. In this mode, you get climb thrust and pitch for the selected airspeed. If you do not follow the flight directors in manual flight, bad things happen. Why would you expect the A/T to reduce thrust when it's in a mode which gives you a fixed climb thrust?

As mentioned before, there is a reason why Boeing tell you to disconnect the A/T and A/P as a first response to a TCAS RA. You can try and second-guess the manufacturer's procedures if you like, but it generally doesn't end well because they usually have a good reason for telling you to do something! 

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Lars,

I think you fall victim to a logically fallacy, to be honest. No, not ment to sound rude.

Change your persective think about what exactly happens there:

the pilot has pressed the toga switches and told the airplane to set take off power.  The airplane is in TO mode which means it will give you take off thrust as calculated and set on the engine rating page in the FMS. As the flight directors (the brain of your a/c) are activated and vnav and lnav modes are armed it will also position the FD bars somewhere centered for lateral and somewhere around 15 deg nose up for vertical navigation. This is ment to be followed! Why? Because this is the pitch were your speed will match or reach the speed that is entered on your mode control panel in the SPD window. The airplane will do nothing else, this is simply the take off mode. It does not avoid mountains, trees or other airplanes. All it does is give you the correct pitch for your take off weight, config and thrust. If you don’t pitch up to match the FD, you will speed up and if you pitch up too much you will become too slow. 

Now you engage your autopilot and the airplane will soon change its mode to hold max climb power allowed as by your settings in the FMS and it will pitch down to match the speed restriction in the SPD window or the FMS as both are inputs for the flight computers, nothing else. Likely it will go for 250kts. Remember: throttle is set for climb power, pitch makes the speed. This is the mode that your aircraft is in. It can not do anything else as it wasn‘t designed to do anything else than this.

Now an other airplane crosses your way and the TCAS gives out an RA (resolution advisory) like decend, decend now! Normally your TCAS would communicate with the other plane‘s TCAS and I doubt yours would want you to decend when you are climbing with 3000fpm but this is a quite dumb PC simulator AI. Important about this is, that this RA is NOT coupled to your airplane‘s flight computers or autopilot system. But it is coupled to the speakers that alert you. If you now switch off your autopilot and push the nose down roughly the brain of your aircraft (the Flight director) is STILL in take off or climb mode, you have done nothing to change that. So it will keep setting climb power. It doesn’t know what you are doing and more important: it doesn’t care. To come back to idle thrust you have to switch off this stubborn system as you are the only one who is responsible of the controls who knows what is going on. And this means just every system that manipulates your controls: AP and AT. 

 

But (and this is probably the most important thing now): as this is something that is very likely never to happen in real life (tcas telling you to decend when your in initial climb) I personally use to completely ignore any RA in this phase of flight. Same on final. There MIGHT be something like this happening in real life that a C172 crosses your glide path or your initial climb, but in P3D most likely a 737 is sitting on your shoulders or landing the opposite direction. And I don‘t give a sh... about this AI behaviour. ;)

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8 minutes ago, Ephedrin said:

There MIGHT be something like this happening in real life that a C172 crosses your glide path or your initial climb

Like this.

 

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20 hours ago, skelsey said:

The AFDS is in THR REF | VNAV SPD for the climb. In this mode, you get climb thrust and pitch for the selected airspeed. If you do not follow the flight directors in manual flight, bad things happen. Why would you expect the A/T to reduce thrust when it's in a mode which gives you a fixed climb thrust?

 

15 hours ago, Ephedrin said:

Lars,

I think you fall victim to a logically fallacy, to be honest. No, not ment to sound rude.

Change your persective think about what exactly happens there:

the pilot has pressed the toga switches and told the airplane to set take off power.  The airplane is in TO mode which means it will give you take off thrust as calculated and set on the engine rating page in the FMS. As the flight directors (the brain of your a/c) are activated and vnav and lnav modes are armed it will also position the FD bars somewhere centered for lateral and somewhere around 15 deg nose up for vertical navigation. This is ment to be followed! Why? Because this is the pitch were your speed will match or reach the speed that is entered on your mode control panel in the SPD window. The airplane will do nothing else, this is simply the take off mode. It does not avoid mountains, trees or other airplanes. All it does is give you the correct pitch for your take off weight, config and thrust. If you don’t pitch up to match the FD, you will speed up and if you pitch up too much you will become too slow. 

No offense taken, you are not sounding rude. I think I had or perhaps I still have  fragmentary knowledge of the Flight Director system and it's interaction with the A/T. I think that my faulty idea might come from the MS Default aircraft as they were in FSX. I started flightsimming with FS95 and continued with FS98, FS2000, FS2004 and FSX. Those birds were very simplistic and easy to handle. They had no VNAV or FLCHG, only VSPEED, and when you descended, the automatic reduced your thrust setting. Thank you for the very good explanation.

 

20 hours ago, skelsey said:

It is absolutely, categorically not a bug, and I have to say I'm perplexed as to how you've reached that conclusion when several of us, including someone who flies the aeroplane for real, have  already explained to you that it's your technique at fault and not the aeroplane.

I have reached this conclusion since myself and other people, who are, contrary to me, real world T7 Captains as per their own statement, have the impression that the pitch handling of this bird might be not exactly as it is in reality. Further, I have the purely subjective impression that the A/T has a tendency to set too much thrust, often more than needed (which can be a feature, and doesn't have to be a bug).

 

20 hours ago, skelsey said:

As mentioned before, there is a reason why Boeing tell you to disconnect the A/T and A/P as a first response to a TCAS RA. You can try and second-guess the manufacturer's procedures if you like, but it generally doesn't end well because they usually have a good reason for telling you to do something! 

I have searched the FCOM 1 and 2, the FCTM and the QRH and I did not find the line where it says that I should immediately disconnect A/P and A/T. It is logical to me to disconnect A/P, it just was not logical to me to disconnect A/T, too. Could you point me to the line where it says that you have to disconnect A/T?

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36 minutes ago, CaptainLars said:

I have searched the FCOM 1 and 2, the FCTM and the QRH and I did not find the line where it says that I should immediately disconnect A/P and A/T. It is logical to me to disconnect A/P, it just was not logical to me to disconnect A/T, too. Could you point me to the line where it says that you have to disconnect A/T?

Manoeuvres section of the QRH, "Traffic Avoidance":

Quote

Pilot Flying
If maneuvering is required, disengage the autopilot and disconnect the autothrottle. Smoothly adjust pitch and thrust to satisfy the RA command.
Follow the planned lateral flight path unless visual contact with the conflicting traffic requires other action.

 

36 minutes ago, CaptainLars said:

No offense taken, you are not sounding rude. I think I had or perhaps I still have  fragmentary knowledge of the Flight Director system and it's interaction with the A/T. I think that my faulty idea might come from the MS Default aircraft as they were in FSX. I started flightsimming with FS95 and continued with FS98, FS2000, FS2004 and FSX. Those birds were very simplistic and easy to handle. They had no VNAV or FLCHG, only VSPEED, and when you descended, the automatic reduced your thrust setting. Thank you for the very good explanation.

As you say, the issue stems from your understanding of the autothrottle system. The FCOM has more detail, but fundamentally the A/T has various modes. Some (like THR REF and IDLE) are fixed thrust modes, others (like SPD) are modes in which the A/T will modulate thrust in order to maintain a target speed. Because V/S mode is a "speed on thrust" mode, the autothrottle will revert to SPD mode as soon as it is selected. However, in a "speed on pitch" mode like VNAV SPD, or FLCH you will get a fixed thrust mode like THR or THR REF (or, conversely, IDLE in the descent). In these modes the AFDS targets a pitch to maintain speed and therefore if you fly away from the FD commands, as I say, Bad Things May Happen (like an overspeed if you under-pitch in a climb, or a stall if you over-pitch in descent with IDLE -- this is what happened to Asiana at SFO).

The really important thing to remember is that the A/P is just muscle. The FD is the "brains" and either the A/P follows it when it is engaged or you as the human follow it when the A/P is out -- your choice, but it is still the FD that is calling the shots as far as modes are concerned.

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6 hours ago, skelsey said:

Manoeuvres section of the QRH, "Traffic Avoidance":

Thanks, I had searched for "TCAS". :blush:

 

6 hours ago, skelsey said:

As you say, the issue stems from your understanding of the autothrottle system. The FCOM has more detail, but fundamentally the A/T has various modes. Some (like THR REF and IDLE) are fixed thrust modes, others (like SPD) are modes in which the A/T will modulate thrust in order to maintain a target speed. Because V/S mode is a "speed on thrust" mode, the autothrottle will revert to SPD mode as soon as it is selected. However, in a "speed on pitch" mode like VNAV SPD, or FLCH you will get a fixed thrust mode like THR or THR REF (or, conversely, IDLE in the descent). In these modes the AFDS targets a pitch to maintain speed and therefore if you fly away from the FD commands, as I say, Bad Things May Happen (like an overspeed if you under-pitch in a climb, or a stall if you over-pitch in descent with IDLE -- this is what happened to Asiana at SFO).

The really important thing to remember is that the A/P is just muscle. The FD is the "brains" and either the A/P follows it when it is engaged or you as the human follow it when the A/P is out -- your choice, but it is still the FD that is calling the shots as far as modes are concerned.

What about HOLD? I figure that in VNAV or FLCH with A/T in HOLD, I control my rate of descent by manual throttle input. More thrust results in a less steep descent, and less thrust in a steeper descent because the aircraft is trying to meet the target speed with the thrust that I apply, am I right? When I initiate a descent, the aircraft first goes into IDLE and then in HOLD.

Thank you for the clarification about A/T and F/D, it's much appreciated.

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12 hours ago, 30K said:

 

Please read the forum rules, since you seem to be such an avid reader.

Btw, I never heard "Retard" in a Boeing...

Edited by n4gix
Removed quote of now hidden post.

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18 hours ago, CaptainLars said:

What about HOLD? I figure that in VNAV or FLCH with A/T in HOLD, I control my rate of descent by manual throttle input. More thrust results in a less steep descent, and less thrust in a steeper descent because the aircraft is trying to meet the target speed with the thrust that I apply, am I right? When I initiate a descent, the aircraft first goes into IDLE and then in HOLD.

Correct, I use this technique often in the NGX and B744 but less so in the 777.  I prefer using the FPA to set up a controlled descent (I'll much prefer this to V/S, which is something I've been taught to avoid).  Many arrivals have a descent profile of about 2.4 - 2.8 deg and when you find that sweet spot it makes everything happen very smoothly.

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5 hours ago, downscc said:

Correct, I use this technique often in the NGX and B744 but less so in the 777.  I prefer using the FPA to set up a controlled descent (I'll much prefer this to V/S, which is something I've been taught to avoid).  Many arrivals have a descent profile of about 2.4 - 2.8 deg and when you find that sweet spot it makes everything happen very smoothly.

OK, thank you for your input.

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