Hydraulics Problem/Question

[Guest A32X]

Hello,With the engines not running, and both the left and right isolation valve switches off I can power hydraulic systems 1 and 4. Is this normal behavior? (I have the 744Pax only.)Paul

[Qavion 19]

As you have suspected, it's not normal behaviour. Anyone else seeing this? I'm running the 744F and it's ok. Regards.Q>

[Guest threedeltamax]

Isolation Valve Switches?

[Qavion 19]

"Isolation Valve Switches?"Left / Right Bleed Isolation Valves (on the Pneumatics panel)Cheers.Q>

[Guest flightgamer]

Read the Systems manual....Remember RTFM ;)

[Qavion 19]

"Remember RTFM"You've lost me.... Do you think the ADP's WILL work with the bleed valves CLOSED?If so, how?Or did you simply misread the original message?Cheers.Q>

[Guest D17S]

No APU/ All engines running / 1&4 engine bleed off / 2&3 engine bleeds on / cross bleeds iso / ADP SELECTED "ON" / 1 & 4 ADPs run. ADP sw back to "AUTO."Shut down 1&4 engines / EDP pressures drop / ADPs come online.So far so good. ADPs will run from any manifold pressure source. Schematically, it looks like the iso valves are between the engines, but they're not. They isolate (split) the wings. BTW, The question sounds funny. With no air on the airplane ("all engines shut-down" . . . and we assume no APU), we're considering that ANY pneu valve position will cause an ADP run . . . or to not run? That'd be one magical valve! There appears to be a bit more to the story,

[Qavion 19]

"("all engines shut-down" . . . and we assume no APU"Actually, WE didn't. I assumed the APU to be running or an alternative source of air available (I'm not going to insult the intelligence of the original poster by thinking otherwise).Note that on the 767, the wing isolation valves can be closed, but the air from the APU can still get to the wings. However, the 744 is designed differently.There is another scenario. APU running and suppling bleed, but not electrics. If the engines were shut down, there would be no electrical power source for the bleed isolation valves, so even if you did push the wing isolation switches, the valves would remain in the original OPEN position.Hopefully, the original poster will comment further.Cheers.Q>

[Jet Tech 31]

Gents,I think if you look closely at the Pnuematic Synoptic page you might see the External Air is connected and these connection points are outside of the Pnue Isolation valves allowing air to run the ADP even with the isolation valves closed. The Ground Air is ON by default whenever the External Power is available and can be deselected in the PMDG menu if desired. (but you will lose your external power as well)RegardsPaul Gollnick :-cool Technical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.comhttp://www.precisionmanuals.com/priv/img/forum/sig_pmdg.jpg

[Qavion 19]

Paul, on a 744, all three ground air supply connectors are delivered to the centre section of the manifold. That's why "EXT AIR" appears on the Pneumatic synoptic in the centre.PMDG's latest version of the 744 is working correctly.Cheers.Q>

[Guest hangar744]

Hi Qavion,I'm sure you meant two (instead of three).Cheers,delcom

[Qavion 19]

"I'm sure you meant two (instead of three)."Maybe, maybe not... :(

[Guest hangar744]

Very nice photograph indeed. To be honest...I've never seen a "triple" config like this before. Can't even find any info or documentation about this "modification".Conclusion: all those years spent on the type and I still discover new things.Thanks Q.Cheers,delcom

[Qavion 19]

"Conclusion: all those years spent on the type and I still discover new things."Same here (part of the fun of being an engineer ;))I have a quote in my training manuals saying that only two connectors are fitted to CF6-powered aircraft. However, the Thai Airways Boeing Maintenance Manual shows 3 connectors (and I believe all their aircraft have CF6 engines).Cheers.Q>

[Guest hangar744]

At this stage I don't see the relation between the number of connectors and engine variants. If there's any at all. I do FD on all three configs for several operators...sometimes the differences are incredible, indeed. I'm sure there is a SB747-21-xxxx describing this modification in great details. For some reason I think no 744 has ever left Seattle with three ground service connectors.Requesting permission to print your little attachment. I'd like to show it to my colleagues. I can already hear them (the stubborn ones): "Yeah right, photoshop, huh?" ;-)thx in advance Qavion.regards,delcom