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morph10

Flight director off during approach (747)

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Again, we see people guessing - and guessing incorrectly. The manuals are there for a reason.

FCOM V2 4-10-15

737

APP switch light extinguishes after localizer and glideslope capture.

After localizer and glideslope capture, APP mode can be disengaged by:
• pushing a TO/GA switch
• disengaging autopilot(s) and turning off both F/D switches
• retuning the VHF NAV receiver.

747

APP mode can be terminated prior to
localizer or glide slope capture by pushing
the APP switch a second time, or by
selecting LOC, LNAV or VNAV modes to
override APP mode.

APP mode will also disengage if localizer is
captured and different roll mode is selected.
If the glideslope only has been captured,
selection of a different pitch mode will
disengage the APP mode.
If TO/GA is selected, or the flight directors
are selected OFF at any time, APP mode
will disengage.

777 (incomplete extract - other options exist!)

The approach mode deselects:
• by pushing APP when above 1,500 feet radio altitude
• with localizer captured and glideslope armed, by selecting heading select
(HDG SEL) or heading hold (HDG HOLD)
[Option – GS capture not inhibited before LOC capture]
• with localizer armed and glideslope captured, by selecting any other pitch
mode except VNAV
• after localizer and glideslope are captured, by selecting TO/GA mode

 


Paul Smith.

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2 hours ago, Paul_Smith said:

I do not care 'who' tells me something, I care if what they tell me can be verified.

This.

Bothers me to no end how people will get on my case for asking for verification. "Oh, you just don't want to admit you're wrong."

No - quite the opposite - I want to know without question that I am, and specifically why.

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Kyle Rodgers

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sorry, but this is getting funny now:

 

Bertie stated this (wich seems to be a religious statement to some people😞

1) By pushing the APP switch a second time before LOC and G/S capture.

2) By selecting TOGA after LOC and G/S capture.

3) By disengaging the A/P and turning off both FD's after LOC and G/S capture.

4) By selecting a pitch mode other than VNAV when the G/S is captured and the LOC is armed.

5) By selecting a roll mode other than LNAV when the LOC is captured and the G/S is armed.

6) By selecting LOC mode when the LOC is captured and the G/S is armed (this then becomes a localiser approach).

7) By selecting LNAV, VNAV or LOC before the localiser and glideslope are captured.

 

meanwhile the "scientific approach" of others gives us this:

747

APP mode can be terminated prior to
localizer or glide slope capture by pushing
the APP switch a second time, or by
selecting LOC, LNAV or VNAV modes to
override APP mode.

APP mode will also disengage if localizer is
captured and different roll mode is selected.
If the glideslope only has been captured,
selection of a different pitch mode will
disengage the APP mode.
If TO/GA is selected, or the flight directors
are selected OFF at any time, APP mode
will disengage.

 

 

I still have to find the mistake in Berties "opinion"....(the 1500 ft thing cant be it, because he was talking only about the 744)

 

 

 

 

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9 hours ago, Paul_Smith said:

I am sure Bertie won't be offended when I say I prefer the scientific approach to the religious one. I do not care 'who' tells me something, I care if what they tell me can be verified. Bertie isn't right just because he flies one, Bertie might be right if he quotes the section of the manual that you can then go and verify for yourself. This is *his* checklist, it is not the FCOM. One example of the difference is the importance of passing 1500AGL as this involves changing modes and behaviors. This is not very clear in the FCOM (it is improved upon in the 777 FCOM) but is not mentioned at all in Berties list.

Gents,

First of all, Kyle is quite right in what he has said to Paul, who apparently doesn't believe a word I or anyone else says, unless we quote verbatum from a 744 manual.  I am not going to do that, because I have listed what Boeing states are the 'actual' methods for disconnecting APP Mode in a 744 with the AFDS engaged.  Read them carefully and it should become obvious they apply after the MCP APP button has been pressed and not only when the aircraft is fully coupled on an ILS approach (i.e. with LOC and G/S Green annunciated on the FMA's). 

Secondly, there has been a lot of discussion (hot air?) about what happens on the 737,777 compared say to the 744, but what seems to have been forgotten is what happens to the various systems and annunciations during the various stages of the approach, because they will also change.  it is a nonsense for any of us to compare how the AFDS systems work on one aircraft type with another and expect them to operate in exactly the same way. The same aircraft manufacturer will often make changes and improvements over time between different aircraft models and even on the same aircraft type.  For example, the original B747 had only two analogue autopilots whereas the 747-400 and the latest 747-8 all have three digital autopilots and so, although the basic operational philosophy may be very similar with two autopilots engaged, to compare the actual operation of the analogue version with the digital one would be the rather like comparing chalk with cheese.

Third,  I didn't mention what happens differently passing 1,500ft AGL when the aircraft is fully coupled on an ILS approach, because this wasn't part of the original question.  Nothing changes as far as disconnecting the APP mode is concerned, because in practise you either press one of the TOGA buttons and fly a missed approach,  or you disconnect the autopilot(s), turn off the Flight Directors and fly the aircraft manually - it's as simple as that! 

Paul, if you really want to know exactly what happens during a 744 Autoland when passing 1,500 ft on an ILS approach, then I suggest you get qualified on the real aircraft.  You will discover that the AFDS system carries out what is sometimes referred to as a Platt test, the rudder channel engages and the electrics split automatically, so that each autopllot is powered from its own electrical source.  All three autopiots engage and either LAND 3, or LAND 2, or NO LAND, is annunciated; although this can sometimes occur as late as 500ft AGL (if not a Go-around must be flown).  Any one of these three FMA annunciations will determine what Autopilot serviceability you have and therefore what Autoland limits you should use (i.e. below 1,000ft AGL) for that approach and also what reversion limits you have, if any.  I could go into a lot more detail but this isn't the right PMDG forum for the 744, so I hope my short 'scientific approach' here is helpful, even if this explanation isn't a direct quote from any Boeing manual! LOL

Happy Autolands!

Edited by berts
typo
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Bertie Goddard

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11 hours ago, berts said:

First of all, Kyle is quite right in what he has said to Paul, who apparently doesn't believe a word I or anyone else says, unless we quote verbatum from a 744 manual. 

Funny that, I read what Kyle wrote quite differently. I took it to mean that he was as tired as I am of people who say "Believe me, I know these things" and fail to offer any support for their beliefs. Perhaps he is more of a diplomat then I thought. 

Lots of things weren't part of the original question, which hasn't actually been answered yet. The original question was :

On 2/1/2019 at 11:43 PM, morph10 said:

Would love to know does the flight director get turned off during approach (before landing) in case of a go around? As I am aware that you cannot turn off the approach button on go around when flight directors are still engaged.

And the answer is no, the flight directors do not get turned off in the case of a go around initiated by pressing the TO/GA button while on approach mode. According to the FCOM, TO/GA mode commands the pitch angle required for go around and the bank angle required to maintain ground track (at time of engagement) both of which will be shown by the flight director. I am not actually sure what effect pressing TO/GA has on autothrottle behavior. I would have thought that it changes to THR limit in CLB setting but I can't find an explicit statement in the FCOM to that effect while the section on the IAS window says it is not blanked when TO/GA mode is selected suggesting Speed control might be left completely to the PF! I am sure a RW pilot will be along soon to clarify this detail.


Paul Smith.

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42 minutes ago, Paul_Smith said:

Funny that, I read what Kyle wrote quite differently. I took it to mean that he was as tired as I am of people who say "Believe me, I know these things" and fail to offer any support for their beliefs. Perhaps he is more of a diplomat then I thought. 

Lots of things weren't part of the original question, which hasn't actually been answered yet. The original question was :

And the answer is no, the flight directors do not get turned off in the case of a go around initiated by pressing the TO/GA button while on approach mode. According to the FCOM, TO/GA mode commands the pitch angle required for go around and the bank angle required to maintain ground track (at time of engagement) both of which will be shown by the flight director. I am not actually sure what effect pressing TO/GA has on autothrottle behavior. I would have thought that it changes to THR limit in CLB setting but I can't find an explicit statement in the FCOM to that effect while the section on the IAS window says it is not blanked when TO/GA mode is selected suggesting Speed control might be left completely to the PF! I am sure a RW pilot will be along soon to clarify this detail.

Iam  sure  Bert  will be able answer  this  

Edited by pete_auau

I7-800k,Corsair h1101 cooler ,Asus Strix Gaming Intel Z370 S11 motherboard, Corsair 32gb ramDD4,    2  ssd 500gb 970 drive, gtx 1080ti Card,  RM850 power supply

 

Peter kelberg

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2 hours ago, Paul_Smith said:

I am not actually sure what effect pressing TO/GA has on autothrottle behavior. I would have thought that it changes to THR limit in CLB setting but I can't find an explicit statement in the FCOM to that effect

FCOM page  4.10.19 states the following about the TOGA switch for the 744 :

PUSH (On approach with flaps out of up or glideslope captured)

- activates A/T in THR mode with GA reference thrust limit displayed

- selects TO/GA roll and pitch modes

- second push - activates A/T in THR REF mode

......

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9 hours ago, Sekkha said:

FCOM page  4.10.19 states the following about the TOGA switch for the 744 :

PUSH (On approach with flaps out of up or glideslope captured)

- activates A/T in THR mode with GA reference thrust limit displayed

- selects TO/GA roll and pitch modes

- second push - activates A/T in THR REF mode

......

Basically yes, but just to be clear:-

During an ILS approach in the 744 when the Flaps are away from UP, or at Glideslope capture, TOGA mode becomes ARMED in pitch and roll (although this mode is not annunciated).  The Thrust Reference Limit changes to G/A and TOGA will remain armed until 2 seconds after the aircraft passes below 5ft RA.  A single push of a TOGA switch during the approach will ENGAGE the TOGA Mode and the AFDS will control the aircraft's pitch to maintain the greater of the selected or current airspeed.  However, if the airspeed is increasing above the initial target for more than 5 seconds then the target airspeed becomes the current airspeed up to a maximum speed shown in the IAS/MACH window + 25kts.  At the same time the Thrust Ref will change to THR and the A/T will increase engine thrust up to the THR Ref Limit in order to achieve a 2,000ft/min rate of climb. 

When this 2,000ft/min climb rate is established the Autothrottle will maintain it by simply adjusting the thrust until the AFDS captures the selected G/A altitude.  At ALT capture the pitch mode changes to ALT and two autopilots will drop out automatically, leaving the first A/P in CMD engaged in TOGA roll mode until another mode is selected.  It is worth bearing in mind that the Autothrottle will remain operating in an unannunciated thrust hold at the current power setting until another SPD mode is selected, or until the maximum speed is reached.

As has already been mentioned, the Flight Directors normally remain on throughout an ILS approach and go-around.  However, this is not always the case during the Go-around, because in order to terminate TOGA mode when the aircraft is still below 400ft RA it is necessary to disconnect the autopilot(s) and turn OFF both Flight Directors. Above 400ft RA then a different roll or pitch mode selection can be made, although doing so will again result in autopilot dropout leaving a single A/P channel in CMD. Another interesting thing happens in the 744 when the FD's are already switched OFF for the approach, because pushing a TOGA switch with the airspeed above 80 kts and the flaps away from UP results in the command bars being displayed automatically. 

13 hours ago, Paul_Smith said:

I am not actually sure what effect pressing TO/GA has on autothrottle behavior.  ........................... I am sure a RW pilot will be along soon to clarify this detail.

I am sure a RW pilot will know this and be along soon to clarify this detail, eh, Paul?  

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Bertie Goddard

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Try to argue on the facts without the personal jabs here and there.

Disagreements are frustrating, yes, but arguments are won with facts. This is a fact.


Kyle Rodgers

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9 minutes ago, scandinavian13 said:

Try to argue on the facts without the personal jabs here and there.

Disagreements are frustrating, yes, but arguments are won with facts. This is a fact.

Although alternatively.... 

Discussions are won with facts, arguments are won by shouting louder and for longer than your opponent, until the truth is buried and forgotten. 

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Russell Gough

Daytona Beach

FL

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4 minutes ago, sloppysmusic said:

Although alternatively.... 

Discussions are won with facts, arguments are won by shouting louder and for longer than your opponent, until the truth is buried and forgotten. 

haha - there's some truth to this.

A little Orwellian this early in the morning though, no?

"He who controls the past, controls the future; and he who controls the present, controls the past."


Kyle Rodgers

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3 minutes ago, scandinavian13 said:

haha - there's some truth to this.

A little Orwellian this early in the morning though, no?

"He who controls the past, controls the future; and he who controls the present, controls the past."

The doublethink is strong in some of these threads! 

😶

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Russell Gough

Daytona Beach

FL

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14 hours ago, berts said:

I am sure a RW pilot will know this and be along soon to clarify this detail, eh, Paul?

No worries Bert, Manolo already referenced the relevant part of the FCOM.


Paul Smith.

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16 hours ago, berts said:

At ALT capture the pitch mode changes to ALT and two autopilots will drop out automatically, leaving the first A/P in CMD engaged in TOGA roll mode until another mode is selected.  It is worth bearing in mind that the Autothrottle will remain operating in an unannunciated thrust hold at the current power setting until another SPD mode is selected, or until the maximum speed is reached.

As has already been mentioned, the Flight Directors normally remain on throughout an ILS approach and go-around.  However, this is not always the case during the Go-around, because in order to terminate TOGA mode when the aircraft is still below 400ft RA it is necessary to disconnect the autopilot(s) and turn OFF both Flight Directors. Above 400ft RA then a different roll or pitch mode selection can be made, although doing so will again result in autopilot dropout leaving a single A/P channel in CMD.

And just to continue this line of discussion... who (Bertie excluded!) can see the trap Boeing laid here for the unwary? 🙂


Simon Kelsey

sig_FSLBetaTester.jpg

 

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