AT and FD behaviour with the FD switches OFF

[emerydc8]

Hopefully Peter can chime in here, but let me describe a scenario on the 767 and see if you think it might apply on the 744 too. On the 767, VNAV is (unfortunately) not a full-time feature. So on a go-around when you get to 1000', you have to set your speed (Vref30+80), press CLB thrust (on the thrust mode select panel), retract flaps, then press FLCH just as you pass Vref30+80.

On my first FTD, I got the callouts a bit out of sequence and asked for FLCH right after I called for setting speed to Vref30+80, but before retracting the flaps and getting to the bugged speed. FLCH  definitely grabbed the speed I was doing (about Vref30+15) instead of the speed that was bugged.

[Hardy Heinlin]

Modifications discussed in this thread are now available in PSX 10.1.1-beta19:

http://aerowinx.com/board/index.php?topic=4020.0


Regards,

|-|ardy

[John H Watson]

and asked for FLCH right after I called for setting speed to Vref30+80, but before retracting the flaps and getting to the bugged speed. FLCH  definitely grabbed the speed I was doing (about Vref30+15) instead of the speed that was bugged.

Looking at my 767 books... it just says

"Speed initialises to current speed".

My 747-400 books say:

If VNAV was not engaged, the display shows the higher of present airspeed or
present MCP speed.

In a 767 AMM for another operator, it says...

(It doesn't mention what happens with the airspeed window is blank.)

For airplane effectivity WWW~XXX, if the speed window is blank, the window opens to current speed when FLCH is pushed. But, for airplane effectivity YYY~ZZZ, if the window is blank, the window opens to  target FMC speed. This AMM doesn't say what will happen if the window is open.

[emerydc8]

Maybe Peter can check this out if he doesn't already know.

Thanks for the updates, Hardy! Great work!

Jon

[Britjet]

Hardy,

I see that beta 1.1.149 refers to the GA Limit being locked when inboard flaps are at landing position. That wasn't the case - I could change out of the mode using the FMC...
Peter.

[Hardy Heinlin]

Now I'm confused, Peter. Are you really meaning "landing flaps" now? Or just "flaps out"?

You wrote ...

Approach - with CLB selected as Thrust Limit - selecting flaps 1 - EICAS limit changes to GA, but this can be modified in the FMC page.
I didn't get chance to try landing Flap in isolation but my guess would be that it would be the same as GS capture which changed (previously selected) CLB mode to GA, and was locked - could not be changed - in FMC.

Select Flap 1 - EICAS thrust limit changes to GA. But this CAN be changed to another mode in FMC, unlike the GS capture case.

|-|ardy

[Britjet]

Sorry Hardy - my second visit to the sim was indeed selecting Landing Flap - not flaps 1 as I indicated.
To confirm - selecting landing Flap gives GA if it wasn't already - but this can still be changed.
Peter.
Sorry for the confusion - it's bedlam in the sim trying to do this and land at London City while pointing out landmarks, pulling the GPWS cbs to avoid 'OBSTACLE OBSTACLE' as we go past Canary Wharf towers and still get the speed brakes back in and gear down after the guest has lost control etc etc ;-)

[jtsjc1]

Sorry Hardy - my second visit to the sim was indeed selecting Landing Flap - not flaps 1 as I indicated.
To confirm - selecting landing Flap gives GA if it wasn't already - but this can still be changed.
Peter.
Sorry for the confusion - it's bedlam in the sim trying to do this and land at London City while pointing out landmarks, pulling the GPWS cbs to avoid 'OBSTACLE OBSTACLE' as we go past Canary Wharf towers and still get the speed brakes back in and gear down after the guest has lost control etc etc ;-)

That's why they pay you guys the big bucks!  Thanks for teaching us something every day Peter and Hardy.

[Britjet]

Maybe Peter can check this out if he doesn't already know.

I don't, Jon, and I will. I don't have any 747 sessions in the near future but might try it on 777 on Thurs.
Peter

[Hardy Heinlin]

Sorry for the confusion - it's bedlam in the sim trying to do this and land at London City while pointing out landmarks, pulling the GPWS cbs to avoid 'OBSTACLE OBSTACLE' as we go past Canary Wharf towers and still get the speed brakes back in and gear down after the guest has lost control etc etc ;-)

No need to be sorry, Peter. It's a wonder that you can check so many things at all.


Thanks!

|-|ardy

[emerydc8]

No need to be sorry, Peter. It's a wonder that you can check so many things at all.

+1. Thanks, Peter!

Jon

[Britjet]

How does this sound for a "test"

On VNAV initial climb out - once accel is commanded by VNAV, select FLCH. Observe speed window.
Reselect VNAV and intervene at higher then current speed. Select FLCH. Observe speed window.

Select V/S and select a higher than current speed. Select FLCH. Observe speed window.
All while whistling "The flower duet" and serving in-flight refreshments, naturally...
Peter

[Hardy Heinlin]

Both the test and the whistling sounds good :-)


Thanks!

|-|ardy

[andrej]

How does this sound for a "test"

....

All while whistling "The flower duet" and serving in-flight refreshments, naturally...

Peter,

could you make a selfie of that? Or will F/O take care of that?

Cheers,

[Jeroen Hoppenbrouwers]

All while whistling "The flower duet" and serving in-flight refreshments, naturally...

Tut tut ... while serving light in-flight refreshments.


Hoppie

[Britjet]

How does this sound for a "test"

On VNAV initial climb out - once accel is commanded by VNAV, select FLCH. Observe speed window.
Reselect VNAV and intervene at higher then current speed. Select FLCH. Observe speed window.

Select V/S and select a higher than current speed. Select FLCH. Observe speed window.
All while whistling "The flower duet" and serving in-flight refreshments, naturally...
Peter

I've just tried this in RB211 747.
In each case selecting FLCH made no difference - the window opened at the previously bugged speed each time.
Peter.

[Hardy Heinlin]

Maybe FCC version specific ...


|-|ardy

[osss]

Sorry for late answer. Some of this features I experienced at FFS.
All of them are described in FCOM. Due to copyright I can't reproduce any part of FCOM but I'll give page references. And yes, I saw all discussion. Just to make things clear

Just to be sure that I understand what you mean, let me recheck each point:

1. You mean, when both FD switches are off, and TOGA is pushed on the ground above 50 KIAS, the TO/GA roll and pitch modes should be displayed? -- In PSX, and on the real 744, as far as I know, the TO/GA switch is inoperative above 50 KIAS until after lift-off.

FCOM 747-400 vol. 2 Pages: 4.10.17 and 4.20.3

A/T operation but not TO/GA is inhibited from 50 kts to 400' altitude. Pushing TO/GA switch above 80 kts activates FD with FD switch positioned off. There is no any references to air/ground mode.

BTW 400 feet ALTITUDE. Does it mean MSL or RA? I do not know how it works in Aerowinx, just reference: during acceleration through 100 kts FMC remembers altitude as a reference point for acceleration height, LNAV, VNAV, A/T activation etc.. page 4.20.9

2. You mean, when both FD switches are off, and TOGA is pushed on the ground before reaching 50 KIAS, and roll and pitch modes are blank, the A/T mode should change from THR REF to HOLD when passing 65 KIAS, even though the TOGA modes are not armed? I don't know if this is correct, but you may be right.

That is how it works at FFS. A/T and A/P works independently.

There is another undocumented feature. At least I did not find any prove to such behaviour in manuals. It is a kind of popular catch. Usually trainees are told about during briefing, forget about and face it several times during session. So here is the scenario (just for fun):

Visual patterns with F/D off.
A/T is used to set T/O thrust.
At 65 knots A/T goes to HOLD mode.
During the pattern the pilot flying (PF) uses manual thrust and FORGETS to disconnect A/T.
On base leg PF asks for landing flaps (25 or 30).
With the flaps at landing position G/A thrust reference sets, A/T mode becomes THR REF and PF turning on final suddenly has G/A power

3. In PSX, the FMC applies the G/A thrust reference logic only when the FMC is in ACT DES; this is to avoid unwanted thrust reference changes when a TO or CLB thrust reference is set (TO provides the same power as GA anyway, and CLB only activates when the initial departure phase is over; why would you request such a time limited, critical thrust setting higher than CLB or CON at high and safe altitudes?). -- But you may be right regarding landing flaps or G/S engagement resetting the GA reference, even when not in ACT DES. But I don't think this is possible while a TO reference is in use. Pushing the TO/GA switch will just remove TO derates, and will not change to GA; I think this has been proven in the BA sim a couple of weeks ago.

4. You wrote: "The reference thrust limit should be locked in GA when flaps are in landing position or glideslope is captured. But is it possible to change it to any other." -- I don't understand the last sentence. Can the pilot change the thrust reference, or is it locked in GA? You may be right; it may change to GA when changing to flap 25 or 30, or when changing to G/S pitch mode, but once GA is set, it can certainly be changed again by the pilot.

During visual patterns FMC is not used usually and meaningless cruise level is set, for example, FL100.. So there is no ACT DES and so on. But as I told before thrust reference sets to G/A. Page 4.20.14

Page numbers can vary with different revisions of FCOM. But all mentioned above can be easy found on adjacent pages.

Stan

[John H Watson]

A/T operation but not TO/GA is inhibited from 50 kts to 400' altitude. Pushing TO/GA switch above 80 kts activates FD with FD switch positioned off. There is no any references to air/ground mode.

For info: The only reference I found to the "auto F/D on above 80kts" in my 744 Engineering training manuals was in the Go Around sub-chapter, not in the T/O sub-chapter.

F/D Auto On Function
The FCC has a F/D auto-on function which causes F/D commands to
show for this mode when the TO/GA switch is pushed with airspeed
more than 80 knots. This function gives F/D go-around commands
with windshear protection without the crew selection of F/D on with
the MCP switches.

Of course, it's reasonable to assume that the aircraft is not capable of flying at 80kts, but if you are experiencing windshear and stalling, you have to set a fairly low trigger value.

[Hardy Heinlin]

Hi Stan,

thanks for your reply. I already modified a few details last week.

BTW 400 feet ALTITUDE. Does it mean MSL or RA? I do not know how it works in Aerowinx, just reference: during acceleration through 100 kts FMC remembers altitude as a reference point for acceleration height, LNAV, VNAV, A/T activation etc.. page 4.20.9

This is also modeled in PSX since the very first version. It is barometric altitude recorded when passing 100 kt.
See Aerowinx Operations manual, page 142.

There is another undocumented feature. At least I did not find any prove to such behaviour in manuals. It is a kind of popular catch. Usually trainees are told about during briefing, forget about and face it several times during session. So here is the scenario (just for fun):

Visual patterns with F/D off.
A/T is used to set T/O thrust.
At 65 knots A/T goes to HOLD mode.
During the pattern the pilot flying (PF) uses manual thrust and FORGETS to disconnect A/T.
On base leg PF asks for landing flaps (25 or 30).
With the flaps at landing position G/A thrust reference sets, A/T mode becomes THR REF and PF turning on final suddenly has G/A power

This is so unusual; we can't be sure that all full flight sims will behave like this, and that this is intentional, or maybe a bug in the original FMC/FCC code which might be resolved meanwhile. So I won't make any modifications in that area for now :-)


Regards,

|-|ardy