Powering down the 777

[leewan]

Hi,
While powering down a 777, I noticed on the overhead panel that the Eng 1 & 2 Main generator(IDG) pushbuttons had the "OFF" amber light illuminated even after the APU shutdown and all power was gone. The batts were off, ADIRU off, emer light off and no ext power. The whole cockpit was dark except these two buttons. So, what was powering these two pushbuttons ? These happened to me once before. I waited for abt 3 mins and it was still on. Any idea ?

[Piper19]

I don't know the 777 (yet), but following your explanation it can only be something like a hot battery bus. (batt switch is for "battery bus" only if the 777 follows normal Boeing philosophy). the hot battery bus is hotwired to the battery without switch in between.

[Fargoo]

The voice of reason BEETOO-1 above knows so much yet fails to share his wisdom with us.
The Off lights are controlled by their respective GCUs and indicate that the GCB is open. I've seen the same phenomenon on the 777 but don't have much time on the type and don't see them very often so have never found out the definitive answer to your question.
I'll ask around and see if anyone can remember and get back to you. :ok:

[QF22]

Gday All
I will have a bash at it !
The ELMS HOT BATT LATCH RELAY in P310 keeps ELMS powered for 90 secs after the BATT is switched off. This allows APU door to close, also DRIVE LIGHTS remain illuminated and brake accumulator indicates pressure.
In flt the relay ensures P310 EEU remains powered to control stby pwr if RAT is deployed
I am a mere mechanical mortal, I am sure some Avionics genious will give a better explanation.
Cheers !

[leewan]

Thanks for the insight Matmax, QF22 and Fargoo.
First of all, this is not a defect that warrants reading up the AMM etc, etc and clearing the defect. Just an interesting observation I saw while powering down T7s.
I am a A&C person and reading wiring diagrams is like reading a foreign language to me. I have tried asking my avionics buddies and as usual, they are just too busy to help me out. Just like how busy they are that they can't open cowlings, open up panels etc ,etc.Thought I could get someone to explain to me in simpler terms in here.
Hope that answers your Qs, Beetoo. Your arrogance and know it all truly astounds me. If you know something, share your knowledge and say it out. If not, then just shut the :mad: up. Your high handed and stuck up "advice" is not required here!

Gnd Eng, I truly agree you can learn more abt the a/c learning and reading it up yourself. That's what i did everytime when i came across something unusual and it gives you alot of confidence to work on it the next time and understand the a/c better. Unfortunately, this was complicated electrical and just looking at a wiring diagrams induces migraine in me.:)

[Jetdoc]

I fully agree with you Leewan. I hope you continue to post more questions in this forum.
Beetoo, maintenance personnel should be able to ask questions without fear. It would be nice to show some professionalism in this forum. Its not all about learning on your own. We can all share our knowledge and experience to everyones benefit.
This forum can be an excellent resource for people to use to learn and we should keep it that way.

[Fargoo]

Gday All
I will have a bash at it !
The ELMS HOT BATT LATCH RELAY in P310 keeps ELMS powered for 90 secs after the BATT is switched off. This allows APU door to close, also DRIVE LIGHTS remain illuminated and brake accumulator indicates pressure.
In flt the relay ensures P310 EEU remains powered to control stby pwr if RAT is deployed
I am a mere mechanical mortal, I am sure some Avionics genious will give a better explanation.
Cheers !

Great reply thanks QF22, just what we needed :ok:

[spannersatcx]

As the saying goes - the only stupid question is the one you don't ask!:ok:

[Perrin]

I worked with engineers for over 40 years and asking and talking and helping each other saved alot of false routes to follow to fix a snag. I sure feel sorry if I had to work with a so called engineer like Beetoo-1. I bet he can't go on who wants to be a millionaire because he wouldn't have friend to call. :uhoh:

Keep them up Boys

[787PIC]

Perhaps the residual power from the PMGs while the engines are winding down!

[MATMAX]

As I can remember , there was a technical question at the beginning of the thread ...
I think that nobody is interested by what you are saying now.
Leewan , sorry , I was too busy last working days to try to find you a TECHNICAL answer ...
I will take time to check the MM next working days.
Salut.

[leewan]

As I can remember , there was a technical question at the beginning of the thread ...
I think that nobody is interested by what you are saying now.
Leewan , sorry , I was too busy last working days to try to find you a TECHNICAL answer ...
I will take time to check the MM next working days.
Salut.

No worries, bro.:ok: I think i found the answer thanks to the input from you guys. QF22 's explanation seems to be it. Looking into AMM for a more thorough explanation.
Just read in a medical journal that the remedy to deviant attention seeking behaviour is not to show any interest in the subject.;) So let's just do that.