Flight director off during approach (747)

[Paul_Smith 92]

A disturbing number of accidents in the real world have been caused because pilots did not understand what their systems were trying to tell them. We have had posters here flatly contradicting each other about the meanings of indicators while saying *exactly* the same thing. Instead of arguing your opinions, why don't you simply quote the manual? It might mean you would have to actually read it again and there is a risk that you might just learn something you didn't know before, but hey, what is life without a little risk?

Approach mode *can* be disconnect by pressing the APP button a second time, but only if certain other conditions are satisfied. Those conditions vary between different aircraft. Approach mode can be changed or disabled in other was as well, and yes, there are ways to turn the Approach mode off without disconnecting the FD's *if* certain other conditions are satisfied.  However, if you are on an approach that is going wrong, which is the usual time when you might want to turn approach mode off, and you *don't* know what those conditions are, or what your systems are telling you, then you will probably crash and burn and kill everybody on board, but hey, as I said, what is life without a little risk?

[berts 97]

8 hours ago, Paul_Smith said:

A disturbing number of accidents in the real world have been caused because pilots did not understand what their systems were trying to tell them. We have had posters here flatly contradicting each other about the meanings of indicators while saying *exactly* the same thing. Instead of arguing your opinions, why don't you simply quote the manual?

You are quite right, Paul. 

My previous post not only describes the importance of relying on the FMA annunciations to inform the pilots what the AP/FD system is doing, but it also lists the different ways APP Mode can be deactivated on the real B744; so why not try each one out for yourself in the QOTS II B744 and see for yourself?

[Paul_Smith 92]

Read the actual manual.

[Sekkha 15]

23 hours ago, Paul_Smith said:

 We have had posters here flatly contradicting each other about the meanings of indicators while saying *exactly* the same thing. Instead of arguing your opinions..

arent you doing exactly this ?

1 hour ago, Paul_Smith said:

Read the actual manual.

didnt Bertie list exactly the conditions which  the manual states ?

anything wrong about what he said ?

why continue arguing here ?

Edited February 5, 2019 by Sekkha

[Ephedrin 418]

On 2/3/2019 at 11:59 PM, berts said:

Sorry, but this is simply not how it works, because the white light in the 744's MCP APP switch will remain on whenever the Approach Mode is active.

The  "language" of the Autopilot/Flight Director system (AFDS) is always determined using the FMA annunciations in each pilot's PFD and not by the lights in the MCP's buttons.  Pushing the APP switch arms/selects the AFDS in LOC and G/S modes and the white APP switch light will stay illuminated until the APP mode is deactivated in one of these possible ways:-

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.

Yes, if the Flaps are not UP and the airspeed is >80kts and they get even more interesting when TOGA is pressed a second time!

 

I'm actually completely confused right now. I've always been completey sure about that when approach mode is entered you can't deactivate it anymore except by turning off the FD or engaging TOGA. Therefore I've never really paid attention to the MCP once I was on the ILS. I've read about this so many times just here in the PMDG forum (at least I'm also "sure" about this 😕 ) so I've never questioned this. 

Now, after your answer, I checked back in the sim with the 737 and the 777 (I don't have any 767 or 757 anymore) and it's actually the 737 only, that shows that behaviour: Once LOC and GS are captured you can't switch off app mode anymore by pressing any MCP button. You have to recycle the FD or press TOGA. 

In the 777 however you can disengage APP all the time, it simply switches over to HDG HOLD and VS with the present vertical speed selected. 

I don't need to try the 744 now, you've already made it clear..

 

So I think there has been any finding when designing the 737NG, which came after the 744 and 777, that has resulted in this "new" behaviour of the MCP/FD? Does someone know how it works on the 737 Classic?

Edited February 5, 2019 by Ephedrin

[Sekkha 15]

3 minutes ago, Ephedrin said:

: Once LOC and GS are captured you can't switch off app mode anymore by pressing any MCP button.

thats the same on the 744, but the light stays on

[Ephedrin 418]

Just now, Sekkha said:

thats the same on the 744, but the light stays on

yep... so first you couldn't disengage APP anymore, then you could (777) and then again you couldn't, but the light turned off. 

So.. as the 787 shares a type rating with the 777 I suppose you can turn it off again? 747-8 too? or not? 

red thread - negative report... That's actually a completely confusing aircraft design. 

[vc10man 732]

9 minutes ago, Ephedrin said:

I'm actually completely confused right now.

That makes two

[Paul_Smith 92]

 

31 minutes ago, Sekkha said:

arent you doing exactly this ?

didnt Bertie list exactly the conditions which  the manual states ?

anything wrong about what he said ?

why continue arguing here ?

I am not the one expressing opinions.

No, Bertie did not list the conditions in the manual.

Yes, there is something wrong with the opinions Bertie expressed. And there is something wrong with Marc's opinion of how things work, and there is something wrong with your opinion of how things work, but you don't need my opinion on it when you can just RTFM for yourself. 

The manual will tell you how Approach mode works for the aircraft you are on, but instead of asking how you disengage it, you should seriously consider when and why you might want to disengage it, and what it is you want to be able to do that requires it to be disengaged.

 

[Ephedrin 418]

4 minutes ago, Paul_Smith said:

And there is something wrong with Marc's opinion of how things work

that's not an opinion. That's false knowledge. My opinion right now is "unlogical and inconsequent aircraft design". But that wonÄt help anyone who finds himself in the situation to decide to go around or not to go around and what's done then.

Sure, everything is written in those manuals. And I agree with you, that buttons should be reviewed in the manuals, it would be faster and more definitive than writing in a forum. However questions like these have often led to good discussions from which people can learn a lot, all above when the actual pilots jump in.. Bertie is one of those flying the 747 for a living. When he states those conditions we can be quite sure that they are correct.

I personally am thankful right now that Marcus brought that topic up, otherwise I would have sticked with that wrong information. Now I will definitely go back to the FCOMs and FCTMs and look up those topics. Please, calm down a bit. 

[skelsey 765]

58 minutes ago, Ephedrin said:

yep... so first you couldn't disengage APP anymore, then you could (777) and then again you couldn't, but the light turned off. 

So.. as the 787 shares a type rating with the 777 I suppose you can turn it off again? 747-8 too? or not? 

red thread - negative report... That's actually a completely confusing aircraft design. 

It's not that confusing when you break it down.

The exact FCOM text, so that we are all on the same page, states:

Quote

Approach mode can be disarmed before localizer or glideslope capture by:

• pushing approach switch a second time, or

• selecting LOC, LNAV, or VNAV

Approach mode deselects:

• with localizer captured and glideslope armed, by selecting another roll mode other than LNAV; selecting LOC mode initiates a localizer approach

• with glideslope captured and localizer armed, by selecting another pitch mode other than VNAV

• after localizer and/or glideslope are captured, by selecting TO/GA mode or disengaging autopilot and positioning both F/D switches off

In other words:

Are both LOC AND GS annunciated in green on the FMA?

If so, the your only way out is TO/GA or turning everything off.

Are only one of LOC or GS annunciated in green on the FMA?

If so then you can cause APP mode to be deselected by selecting an alternative roll and/or pitch mode.

Are neither of LOC or GS annunciated in green on the FMA?

Then you can disarm APP mode by pressing the APP button again or selecting LOC, LNAV or VNAV.

You are not 'locked in' until both LOC and GS annunciate green.

[Ephedrin 418]

1 minute ago, skelsey said:

You are not 'locked in' until both LOC and GS annunciate green.

Hi Simon,

Yes, that's the part that has always been my understanding. Additionally what I THOUGHT (and what has been a topic before in other threads, possibly only in the 737 forum, I don't know) was that this lock was followed by an extinction of the button light on the MCP. So: a light means you can turn it off with this button. Nothing else made sense to me as only the FMA gives definite mode announciations. You can't read the mode from the MCP, you can only see what has been pressed. 

However, now I see that this obviously doesn't work with the 747 and 777. What I find so irritating is: In the 744 (first flight 1989) the APP mode is locked with no indication about this locking process, in the 777 (1993) you can turn it off by just pressing the APP button on the MCP during an ILS approach and end up in the most simple MCP modes available (HDG and VS) and then in the 737NG (1997) you can't leave the mode again but you have the indication about that lock as the light extiguishes. Maybe the 777 locks the mode too when LAND3 is entered, I'll try that out. 

[Sekkha 15]

44 minutes ago, Paul_Smith said:

 

I am not the one expressing opinions.

No, Bertie did not list the conditions in the manual.

Yes, there is something wrong with the opinions Bertie expressed. And there is something wrong with Marc's opinion of how things work, and there is something wrong with your opinion of how things work, but you don't need my opinion on it when you can just RTFM for yourself. 

The manual will tell you how Approach mode works for the aircraft you are on, but instead of asking how you disengage it, you should seriously consider when and why you might want to disengage it, and what it is you want to be able to do that requires it to be disengaged.

 

when the manual states, just as an example , "the light will extinguish" and somebody says "the light will not stay on" , then he is not expressing an opinion ,

but of course, that is just my personal opinion about what an opinion is, and what not.....and might be different from your opinion about that. :)

 

Edited February 5, 2019 by Sekkha

[vc10man 732]

A real Learning Curve herein, culling different posts

[Paul_Smith 92]

22 minutes ago, Ephedrin said:

Bertie is one of those flying the 747 for a living. When he states those conditions we can be quite sure that they are correct.

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.