Slow slats retraction

[Robert3512 21]

https://imgur.com/a/i3gLg

So, I was retracting flaps and slats from 10 to UP, and I'm pretty sure that the slat retraction from 1 to UP doesn't take nearly 2 minutes IRL, does it? The flaps retracted on schedule. I have no failures in the PMDG > FAILURES section active.

[Ephedrin 418]

I‘m not sure about the leading edge flaps but the trailing edge flaps are fed by the outboard engines hydraulic systems. And since No4 is shut down... 

[Budbud 227]

The Flaps primary annouciation and the extended flaps display indicate that the flaps control has dropped to secondary mode (electric). The extension and retractation in this mode is slower than in first mode (hydraulic/pneumatic).

I'm not sure that the engine 4 shut is the only reason for the degraded situation because even with the engine-driven pump 4 off, you should still have the demand pump available to supply the hydraulics system 4.

 

1 hour ago, Robert3512 said:

The flaps retracted on schedule. I have no failures in the PMDG > FAILURES section active

Can you please post a screenshot of the lower EICAS Hydraulics page (I'm suspecting a issue with the configuration of the hydraulics here)?

Edited February 23, 2018 by Budbud

[Ephedrin 418]

1 hour ago, Budbud said:

I'm not sure that the engine 4 shut is the only reason for the degraded situation because even with the engine-driven pump 4 off, you should still have the demand pump available to supply the hydraulics system 4.

I‘m absolutely no 747 expert but I would guess that the main supply engine down and the other 3 at idle, left flaps retracting too, this would slow everything too much down... but a professional answer would be helpful :D

[Budbud 227]

Actually, the OP is talking specifically about the slat retraction. Slats are pneumatically powered by the bleed air in primary mode and electrical powered in secondary mode. But I cannot find in the FCOM whether one engine failure could affect the slat retraction rate.

Also the QRH specifies for Flaps primary to plan for additional time for flap operation. I guess the first to know here is the reason for the flaps primary annunciation to identify which flap group or slat group is affected.

Edited February 23, 2018 by Budbud

[Ephedrin 418]

Oups, ok then I understand why I couldn‘t find LE Flaps on the hydraulics scheme.. lol. 

During my easter holiday I plan to go into the Jumbo‘s system a bit deeper. ^^ as the J41 flights are delayed... 

[Robert3512 21]

So, to address a few questions:

I don't have a screenshot of the HYD page, but I can describe it. Everything is normal except the no. 4 engine pump which is off, as the no. 4 engine is shut down. Flaps retracted normally, it's just the slats that are exceptionally slow, which is kind of weird as I'd expected the whole flap/slat system to revert to secondary mode.

[Budbud 227]

5 minutes ago, Robert3512 said:

Everything is normal except the no. 4 engine pump which is off, as the no. 4 engine is shut down

Are you talking about the demand pump selector knob (AUX/OFF/AUTO) to OFF? In any case, even with engine 4 failure, the demand pump 4 should remain to AUTO and the engine-driven pump 4 switch should remain pushed in. 

If the demand pump 4 is off, that explain the flaps primary annunciation on the upper EICAS.

But anyway, whatever hydraulic pump is off, I see no connection to the extended time need to retract the slats since they are powered by the bleed air and not the hydraulics.

 

Edited February 23, 2018 by Budbud

[Robert3512 21]

Oh yes, I didn't touch the DEM and ENG pump switches. DEM remained on AUTO with no lights and ENG remained on ON with a PRESS light.

[kevinh 409]

Eng 4 demand pump is pneumatic so with idle engine bleed pressure might not be able to keep up with flap hydraulic demands. FLAPS PRIMARY is annunciated. The screen shot shows the LE system in secondary mode. The LE slats switched to electric drive hence the very slow operation.

Edited February 23, 2018 by kevinh

[Budbud 227]

1 minute ago, kevinh said:

With FLAPS PRIMARY detected the LE slats will switch to electric drive, hance the slow operation.

Flaps primary indicates that any one of the LE or TE device has an issue. But I didn't know that it triggered systematically the LE control to go to secondary mode. Then in that case it makes sense.

However the demand pump 4 has nothing to do with the LE since in the primary mode, they are pneumatically powered by the bleed air pressure, but a lack of pressure in system 4 could trigger the flaps primary I guess which would led in turn to swith the LE to secondary mode.

Robert, did you have a HYD PRESS [DEM/SYS/ENG] annunciation at any time before the flaps primary?

[scandinavian13 5,192]

I'm not sure what the issue is here.

All I'm seeing is "I'm treating the aircraft in a manner that is non-standard, putting it in a non-standard state, but expecting it to behave in a standard fashion."

This isn't a default aircraft.

[iwebber 207]

6 hours ago, Robert3512 said:

slat retraction from 1 to UP doesn't take nearly 2 minutes IRL, does it?

Yup, with the electric backup system.

Had it recently (bleed or duct issue, I forget which) MEL said it was OK to take it for a few days/sectors, so we were on backup slats. It’s a very long 2 minutes.

HTH

Ian Webber

[kevinh 409]

7 minutes ago, Budbud said:

Flaps primary indicates that any one of the LE or TE device has an issue. But I didn't know that it triggered systematically the LE control to go to secondary mode. Then in that case it makes sense.

I had edited my post to clarify what I meant. The LE system is in secondary mode, it isn't clear why though.

Edited February 23, 2018 by kevinh

[kevinh 409]

3 minutes ago, scandinavian13 said:

I'm not sure what the issue is here.

All I'm seeing is "I'm treating the aircraft in a manner that is non-standard, putting it in a non-standard state, but expecting it to behave in a standard fashion."

This isn't a default aircraft.

I don't think anyone else has suggested anything like that, Kyle. People are just trying to figure out the reason why things have happened as they have.