B744 Autothrottle on Manual Landing

[NSEU]

Originally Posted by JammedStab

I doubt the autothrottle has any idea how whether the autopilot is engaged or not so it just does its thing as usual.

As I said earlier, the idle retard command actually comes from the AFDS (according to the engineering manuals). One would hope that the AFDS knew if it was engaged or not

Cheers

[JammedStab]

Originally Posted by NSEU

As I said earlier, the idle retard command actually comes from the AFDS (according to the engineering manuals). One would hope that the AFDS knew if it was engaged or not

Cheers

Thanks,

Obviously your manuals have more details than our manuals. But the real question would be, is there any difference in autothrottle operation based on the use of the autopilot and if so, why.

[cf6-80c2b5f]

That pretty much restates my original question in a more concise way. So far, we've got peole saying it behaves the same as the autoland and people saying it stays in SPD until anywhere from 25' RA to a few seconds after touchdown, then the autothrottle FMA goes blank -- no IDLE. CCA said he even got the AUTOTHROTTLE caution when it went from SPD to blank after touchdown. It is appalling that Boeing doesn't explain this better.

[BBK]

Re the Boeing manuals it's just a thought but maybe they're written to give pilots the necessary info not answer hypothetical questions?

[cf6-80c2b5f]

It's a "hypothetical question" until it causes an accident, like the Asian 777 in SFO. If you're happy being ignorant about this, you can always skip this string. Thanks again for your valuable input.

BTW, regarding your prior post:

I'd never heard of FLCH trap until the Asiana crash and as someone else mentioned it might be an issue on the 777 and 748 but not the 744 although I'm happy to be corrected but it doesn't ring any bells and I've read the FCOMs a few times.

This demonstrates how poorly Boeing writes its manuals. You've read them a few times and you still don't know whether the FLCH trap applies to the 744? I can tell you without hesitation that it does.

[BBK]

Two questions for you Cf6, why do want to know so badly what happens in this situation which, in my company, shouldn't occur anyway.

In your considered opinion is FLCH an appropriate mode for final approach.

rgds

BBK

PS Oh and I word searched "FLCH trap" in the FCTM and Vol 1/2 of the FCOM and no results.

PPS I believe the Asiana crash may have something to do with the aircraft's speed decaying to something like Vref minus 17!

[cf6-80c2b5f]

BBK:

I'm not sure why you feel compelled to police the forum for questions that you believe are inappropriate simply because "in [your] company, [it] shouldn't occur anyway." Really, you should probably refrain from clicking on this thread if it bothers you that much. So far, your posts have demonstrated that you have nothing of value to add to it.

Of course, FLCH isn't appropriate on final approach, but it was pressed and it resulted in a crash. Most crashes are due to something that shouldn't occur.

The "FLCH trap" was coined by the investigators and attorneys after the Asiana crash. If you did the same thing in the 744, the logic would react the same way.

[BBK]

Calm down dear! (sorry English joke)

CF6 just to refresh your mind this is what I wrote originally. I thought it was polite enough.

"I think it's great that people can post questions and discuss the answers. I'm always ready to learn which is why I read this thread so nothing wrong with that.
However, your question was, in my humble opinion, not so much hypothetical but unrealistic. You may disagree but I'll explain my reasoning......

.....Hope that helps. "

I certainly don't intend to "police" this forum or any other and I'm at a loss why you think so as I only asked why your keen interest. Just idle curiosity. I assume, from what you have written, you are not flying the 744 so thought your comment about the "appalling" Boeing manuals a little odd. I reiterate that using FLCH on the final approach is not a good idea nor is losing control due to stalling on short finals.

Anyway, I consulted said manuals and found the following:

"The flare maneuver brings the airplane to a smooth automatic landing touchdown. The flare mode is not intended for single autopilot or flight director only operation.

Flare arms when LAND 3 or LAND 2 annunciates. At approximately 50 feet radio altitude, the autopilots start the flare maneuver. FLARE replaces the G/S pitch flight mode

During flare: • at 25 feet radio altitude, the autothrottle retards thrust levers to idle • IDLE replaces the SPD autothrottle flight mode annunciation • at touchdown, the FLARE annunciation no longer displays, and the nose lowers to the runway."

I still think manual flight and manual thrust works just fine as did my trainers some of whom have flown the 400 since the 90s.

BBK

Ps exception I've just remembered might be a Cat3A with a dual FMC failure.

[cf6-80c2b5f]

The flare mode is not intended for single autopilot or flight director only operation.

Flare arms when LAND 3 or LAND 2 annunciates. At approximately 50 feet radio altitude, the autopilots start the flare maneuver. FLARE replaces the G/S pitch flight mode

During flare: • at 25 feet radio altitude, the autothrottle retards thrust levers to idle • IDLE replaces the SPD autothrottle flight mode annunciation • at touchdown, the FLARE annunciation no longer displays, and the nose lowers to the runway."

There have been reports on this thread that are contrary to the above, unless you take the first sentence as meaning that none of the description that follows the first sentence applies to a manual landing. Check out CCA's post.

I do fly the 744, but I have been out on a medical leave. As I dug into the FMC logic with time to kill, I realized how little I really knew about how it would behave under certain circumstances. When I dug further, it became apparent that my peers were equally clueless. The answers I have received on this forum confirm that it is not just limited to my peers at my airline. We have first-hand testimony from one pilot that it will go from SPD to IDLE and another guy saying that IDLE never happens -- it just goes from SPD to a blank FMA. How could there be such a discrepancy from 744 to 744 with nothing written in the manuals to explain it? Anyway, thanks for the input.

[BBK]

CF6

Just goes to show one shouldn't jump to conclusions and happy to stand corrected. On reflection I wrote my penultimate post after a long night flight so maybe it wasn't as well phrased as it could have been.

Anyway, as you will know very well there are lots of things going behind the scenes with the AFDS that are not annunciated eg runway alignment. I can't offer an explanation for the discrepancies other than maybe they're are different modification states of the FMC perhaps. When you get into how waypoints are coded in the FMC and things like "on approach logic" 'tis a dark art indeed. Anyway, anything I can add I'm sure you would know as a fellow operator so I'll leave it at that.

BBK

[cf6-80c2b5f]

Thanks, BBK. You may very well be right about the different modification states. Whether it was a delivery option from the factory or a subsequent modification, it would be interesting to know the background on this. But like you said, it's a dark art, and at this point most of the engineers who initially worked on the 744 are probably long retired.