Amber Band on Takeoff, Prior to Flap Retraction

[emerydc8]

Hi Peter,

I happened to notice that the amber band (min. man. speed) on the speed tape is displayed in PSX on takeoff, prior to the first retraction of flaps. I think this is inconsistent with my FCOM. Can you check your FCOM to see if it mentions anything about this?

Minimum Maneuvering Speed
Top of amber bar indicates minimum maneuvering speed. This airspeed provides:

1.3g maneuver capability to stick shaker below approximately 20,000 FT
1.3g maneuver capability to low speed buffet (or an alternative approved maneuver capability as preset by maintenance) above approximately 20,000 FT

Displayed with first flap retraction after takeoff.

I probably would have never noticed this, except I was going through the profile for Atlas's takeoff stall and it points out that if you do the stall at your takeoff flap setting (flaps 10 at Atlas), you have no reference to the amber band (there is none until you start retracting flaps). So you don't know what is a "safe maneuvering speed" where you can consider the maneuver complete and engage the A/P and A/T.

You can't really use the bug speed either because when you reach your acceleration height of 1000', the bug speed ratchets up to five knots less than your existing flap placard speed. So, to deal with this, the check airmen recommended using the flaps 5 maneuvering speed as a safe maneuvering speed where you can re-engaged the A/P and A/T and continue the departure using VNAV and LNAV.

How did you guys deal with this at BA?

Thanks,
Jon D.

[John H Watson]

KLM also appears to show no amber band before first flap retraction (as seen clearly in this video at around 21~22 minutes )

https://www.youtube.com/watch?v=s30vpsVtt3I

[emerydc8]

Thanks for the video, John. It looks like the amber band showed up after he selected flaps 5 at 22:33 into the video. That would comport with my FCOM, since he took off at flaps 10 (the accel. height speed was 240 knots (flaps 10 placard speed minus 5 knots)).

[G-CIVA]

You get a great view of the Amber Band appearing during a Flap 20 departure in this footage of a TNT 400ER .... as Flap 10 is selected ...

https://youtu.be/FjwNNYvpO3c

& just catch it in this ex Great Wall now Cargo Air Lines 400ER ...

https://youtu.be/v8xFaJ_-Re4

[Britjet]

Hi Jon,

How did we deal with it? I think we just tried to avoid stalling after take-off:-)
I can't really see how this would arise unless you encountered windshear, which would be an entirely different procedure of course.
The red stick-shake margin is still there of course. I don't really see how the manoeuvre capability is relevant in this case - if you are trying to avoid a stall at low altitude the absolute priority is the stick-shaker margin which is of course dynamic and g-related, whereas the manoeuvre margin indication is simply based on weight and flap and does not change.
The best way to avoid a stall is to stay below the PLI indications. I would have thought that if you had a stall scenario that using the flap bug speeds to initiate normal departure modes would be a pretty low priority.
I will try and check the indication next time I am in the sim, though.

Peter

[emerydc8]

Thanks for the videos, Steve -- right at 5:25 in the first video.

Peter, I think these guys took a few sentences out of the FCTM and ran with it. For simulator purposes the stall maneuver itself is nothing -- it's what happens after the stall recovery is complete that has been complicated. They want to see you continue what you were doing with the automation after you reach a "safe maneuvering speed." During a landing stall or clean stall, that would be the bug speed. But on a takeoff stall, the bug speed moves at acceleration height, so you can't use that to mark the end of the stall and the point where you would begin to re-engage the automation. Also, in the Level-D sim and the real plane, you don't have any amber band to use because you haven't begun to retract the flaps. So, amber band + 20 is not usable for a safe maneuver speed either.

They use the flaps 5 maneuvering speed for this instead.

Here's the statement from the FCTM:

Completion of the Recovery
Upon completion of the maneuver, recover to the command speed, adjust thrust as needed, and follow previous instructions (e.g. heading, altitude). Re-engage the autopilot and autothrottle in accordance with normal procedures.

The landing/ILS stall is even more complex. After you recover to your bug speed, this is what they want to see:

Press TO/GA and call, "go-around, flaps 20."
At positive climb call "gear up."
At 250' above the base altitude and aircraft in trim call "left A/P to command."
At 400' above the base altitude call "LNAV."
At 1000' above base altitude call "VNAV, toggle the  A/T arm switch."
Maintain the altitude assigned by the instructor/ATC.
Retract flaps on schedule. 

What ever happened to the old days when they just wanted to see you recover back to a safe maneuvering speed and then the maneuver was over?

[cagarini]

Just out of curiosity...

How does recovery from stall work, on takeoff, in the 744 ? Do you actually train that in the Level-D sim ?

Is it "easy" to recover from such a situation ? 

[emerydc8]

Yes, this is tested in the Level-D sim at Atlas. Here's a video I did, but I'm reluctant to call it a "tutorial," considering that Peter has set the bar so high and his videos are so much more polished. https://youtu.be/DZ3JukL1imw

If you'd like to give it a try, here's the situ I used. https://drive.google.com/file/d/0B-WRh0Hf7VdZME1DUnBmVTdjTHc/view?usp=sharing

[cagarini]

Thx for the video. Looks very good!

Does the stall in PSX closely mimic what you have in the Level_D sim. Is it so abrupt there as well ?

[emerydc8]

Honestly, I don't know, because I've never done this in the Level-D sim. This is something that Atlas does. In PSX, I did notice a very abrupt break on the stall, requiring almost full aft elevator to keep the nose from dropping below the horizon after initially unloading. I'll have to ask a friend of mine who just went through their training program if it's really this abrupt in their sim. At that light weight, and with max power, I would have thought the pitching moment would have helped offset the tendency for the nose to drop. In our Level-D sim, the pitching moment is significant enough that you can easily get yourself into a secondary stall when you jam the power up there. We don't do this type of takeoff stall at my airline, so it's a new maneuver to me too. I was just following what's in a manual that one of their check airmen wrote as a supplement for training.

I was hoping Peter could try this situ and see if he thinks the abrupt stall break here is representative of the Level-D sim.

[John H Watson]

In G-CIVA's video, https://youtu.be/FjwNNYvpO3c

What test does the captain do at 6:37 which generates an EICAS Caution?

[G-CIVA]

John, I think he just disconnects the A/T ... judging by the indications on FMA ...

[emerydc8]

This is the landing stall as done with the ILS at flaps 30. I'm not sure why the G/S FMA gets a line through it as the speed bleeds down to the red worm of death, so I had to hand fly it and ignore the F/D pitch command just prior to the stick shaker (the AFDS commands a descent below the G/S and I'm not sure it should). https://youtu.be/c7vOMy7IJ_s

The recovery was much more tame than on the takeoff stall. I just talked to a friend who is a 747 classic fleet standards captain and asked him about whether it breaks this hard on the takeoff stall in the classic (it's been so long I can't remember). He said that if it was a deep stall then it would, but if you initiated recovery as soon as you got the stick shaker you could pretty much power out of it without losing much altitude. I am wondering if the stick shaker in PSX is activating a bit late on the takeoff stall, because by the time it does activate, it already seems to be in a deep stall where the nose is dropping on its own.

Here's the situ for the landing stall if you want to give it a try:

https://drive.google.com/file/d/0B-WRh0Hf7VdZZUZVUGhldlB0S0E/view?usp=sharing

[Hardy Heinlin]

(the AFDS commands a descent below the G/S and I'm not sure it should)

It doesn't exactly command a descent, it just commands alpha protection. If it would continue aiming at the G/S path, it would command a stall. The AFDS will never command a stall. Why should it do it? It always goes into alpha protection, even when V/S, G/S, or ALT was engaged where the elevator is not an airspeed controller initially.

When alpha protection is active, the pitch command bar is removed, as it would be contradictory to the original mode, and I guess it would otherwise confuse the pilot.


|-|ardy

[emerydc8]

I see the section in my FCOM under Flight Envelope Protection and it says, "AFDS speed protection is provided through the elevators in the following pitch modes: VNAV SPD, FLCH SPD, or TO/GA."

Is alpha-speed protection referring to the same thing as flight envelope protection?

Also, in the Level-D sim at Atlas, they leave the A/T arm toggle switch on and just disconnect the A/T with the thumb switch in order to set up for the stall. There is no A/T wakeup on the Level-D sim like there is on PSX. The call on the missed approach is actually to "cycle the A/T arm switch" to get it re-engaged in THR REF mode.

They leave the A/P on for the stall as well. Somehow it doesn't drop below the G/S. So there is the additional task of disconnecting the A/P on the recovery.

 Post recovery from the ILS stall:
o PF: When recovered to the bug speed, execute a go around:
 TO/GA push (twice if desired): Go around flaps 20. Manually advance the throttles.
 At 250' above the base altitude and aircraft in trim: XXX Auto-pilot command.
 At 400' above the base altitude: Heading select or LNAV. VNAV or FLCH may be selected if needed.
 At 1000' above the base altitude: VNAV or FLCH, set speed XXX.
 VNAV mode. The pitch mode is VNAV SPD; select the autothrottle switch down and up. THR REF
is activated for the climb. The reference thrust limit changes to CLB. The speed bug will increase
automatically to the clean maneuvering speed or 250 knots, whichever is higher.
 FLCH mode. The pitch mode is FLCH SPD; select the autothrottle switch down and up. THR is
activated for the climb. Set speed as desired.
 Maintain the altitude designated by the instructor/ATC.
 Retract flaps on schedule.

[Hardy Heinlin]

Speed protection is airspeed protection.

Alpha protection maintains stick shaker speed to avoid stalling, and to keep the terrain closure rate as low as possible at the given thrust setting.

Re A/T wake-up: See other thread :-)


|-|ardy

[emerydc8]

That's something I didn't know. So, you can disconnect the A/T and pull the power to idle in ALT and it will actually descend when it gets right above the stall? Do you have any material about this?

I'd like to show it to all the guys who like to start lecturing any time someone does a climb in V/S mode about having no speed protection and you could actually stall the airplane.

[Hardy Heinlin]

I have no material at hand at the moment ... I'm sorry ...

[emerydc8]

Okay, thanks.

Re A/T wake-up: See other thread :-)

I thought we decided that there is no A/T wakeup on the 744 like there is the 777. If you click the A/T off with the thumb switch on an ILS, you should be able to stall the airplane and they won't wake up.

http://aerowinx.com/board/index.php?topic=2597.msg35900#msg35900

[Hardy Heinlin]

Yes, the next PSX update will come later this year ...