Warnings on landing

[GodAtum]

Whenever I do a manual landing, I get CONFIG SPOILER and CONFIG FLAPS warnings on touchdown. ANyone know why?

[Hardy Heinlin]

Takeoff power set for rollout.

[GodAtum]

Interesting. On touchdown I pull back the throttle levers to idle reverse though.

[Hardy Heinlin]

Are your levers operative? Are you checking the EICAS?

A video or a situ file may help.

[GodAtum]

yes the EICAS shows the thrust go to idle. I will try and save a situ file on my next flight. My landing is a bit bumpy which might cause something?

[Gary Oliver]

Hardy,

We have seen this happen a few times too only in recent versions (sorry I cannot pin point which one)... I'll see if I can dig a video evidence out from the Simfest stream for you.

We see it when going from Reverse to forward Idle, the thrust levers definitely still in their 'detent' at idle.

Although of course it could be us injecting a momentary large thrust lever angle, but I doubt it.

Cheers
Gary

[Hardy Heinlin]

Page 543 (new manual) has the details. It's about #2 & #3 thrust (actual thrust), not thrust lever position. However, your reverser levers may return to forward idle too early which retracts the reversers on the engines, and which is a factor in the alert logic as well.

The only modification in a recent version: The spool down time is now longer.

Maybe your hardware goes to forward mode too quickly, before the engines have spooled down below takeoff power.

Normally you return to reverse idle at 80 kt, and to forward idle at 60 kt. Do you set forward idle immediately and directly?


Regards,

|-|ardy

[Gary Oliver]

Hardy,

You are indeed correct.  Time for another memo to the crew from the standards captain for that one.

Cheers
G

[Hardy Heinlin]

I can't reproduce this problem with the mouse or keyboard. The transit of the reverser sleeves takes a couple of seconds, and in that short period of time I can't keep the thrust in the takeoff power range.


|-|

[Britjet]

Standards Captain here LOL..
80kts for selecting reverse idle, but the forward idle selection can be left until 20kts.
It is likely that if you select forward idle at 60kts this will give you a slight "bump" of forward thrust, so best to delay it.
Out of interest Hardy I have never seen a CONFIG Warning on the real aircraft or in the sim caused by cancelling reverse too early. Many times, particularly in the sim, pilots will cancel reverse to idle far too early (because the sim reverse thrust levers tend to be looser than the real ones due to constant use) but we still don't get a CONFIG, even though the thrust is quite high. This suggests to me that it might be a function of thrust lever position, but you obviously have good information to the contrary..
Peter

[Hardy Heinlin]

I have never seen a CONFIG warning in PSX either, caused by cancelling reverse too early.

I don't know why it happens in Gary's sim.

Theoretically it's impossible. I can't reproduce it.

If it would be thrust lever position instead of EEC thrust data, that would explain Gary's problem (signal peaks in  networked lever position data). But PSX and the real 744 uses EEC thrust data of #2 & 3 for this alert type. You can test it in PSX, it will demonstrate it clearly.


|-|ardy


(In some airlines they say 60 kt for forward idle because at that time, after 80 kt, the thrust is usually at idle. Depends on the autobrake setting, of course ...)

[Hardy Heinlin]

Aha, I have never seen this because I didn't use RR engines. Now with RR models selected I can reproduce it.

I guess the definition of "takeoff thrust" in this alert category is a hair too low for the RR model.

In PSX, for config alerts, N1 takeoff thrust is defined as follows:

GE 75.0 %
PW 66.5 %
RR 66.7 %

(Values are taken from maintenance manuals; they are not invented by me.)

When you directly select forward idle after max reverse thrust, the reversers will be retracted at the time when the engine spools through ca. 70 % N1.

I think for the RR I'll increase the threshold from 66.7 to 73.0. Or I'll implement a time delay.

I'll keep it as is. If you select forward idle while reverse thrust is in takeoff range, the alert is a good alert; it tells you that your action is wrong.

A pause of just 1 second between rev idle and fwd idle is already sufficient to avoid the alert. To get the alert you really need to slam the levers fully down from max reverse. Who does that on the real aircraft, Peter? :-)

Or the reverser transit time is too short by some milliseconds. But it's based on real-world observations. And why should Boeing set this crossing point so tight and sensitive for the alert inhibit?

P.S.: In my opinion, it makes sense to use actual thrust instead of lever position. If your actual forward thrust is in takeoff range and you are not configured for takeoff, you are in trouble, no matter what your current thrust lever position is. E.g. there could be a reverser malfunction and you expect reverse thrust while you're actually getting forward thrust.

[Gary Oliver]

Aha, I have never seen this because I didn't use RR engines. Now with RR models selected I can reproduce it.

Thanks Hardy

[cavaricooper]

Hardy-

Reading all this with interest as I normally only fly RR airframes, and have yet to get this EICAS warning.

There is so much knowledge within this fora....

Thanks- C

[Britjet]

As I said - you can get pilots, usually in the sim, going from full reverse to fwd idle in one quick movement - it depends on how stiff the reverser levers are. They <try> to gently edge them forward toward rev idle, but then the lack of stiffness causes them to go straight through to fwd idle. They don't do it intentionally.
There is still no CONFIG Warning.
Peter

[Hardy Heinlin]

Are the amber REV flags still displayed at 67% N1 on BA aircraft?

[Britjet]

I don't know. I can check later in the week..

[Hardy Heinlin]

Thank you, Peter.

That nuisance alert is now inhibited in PSX update 10.10:

http://aerowinx.com/board/index.php?topic=4191.0


Regards,

|-|ardy

[United744]

I thought the CONFIG alert was engine thrust AND thrust lever angle derived? Ergo, if you have high thrust on an engine, but thrust lever at idle, no CONFIG alert.

I don't see the alert in the sim, but I use the toggle for reverse, as well as waiting for near-idle thrust before selection of forward idle.

[John H Watson]

I thought the CONFIG alert was engine thrust AND thrust lever angle derived? Ergo, if you have high thrust on an engine, but thrust lever at idle, no CONFIG alert.

Concerning Takeoff Config, there is no mention of thrust lever position in the maintenance manual, only N1. The Classic was different (a microswitch was activated with the thrust levers in a certain position).

744 Landing config and Speedbrake Alert are different also.