B737 Electrical Smoke

[LEM]

Just some thoughts about electrical smoke in a 737 classic:

To my knowledge, in the sim they can only make smoke come out of the EADI/EHSI, and from the CB panel.

Any other places?


Let's say smoke starts to come out of the F/O EADI.
First thing we could do is depower the whole F/O panel.

Then we'll see....

So: Bus Transfer Switch off, Gen Switch 2 off.

Then there is time to look for the CB, pull it, and restore power to the whole panel.
Wait and see if smoke starts again.

Of course in the meantime turn the horse toward the nearest stable anyway.


If smoke is coming from the CB panel, one thing we could do is depower the whole airplane, turning both generators off, as battery power alone in unlikely to feed a bad short.

We could do the whole descent like this, turning one generator on just before the approach.


Comments are appreciated.

[Engineer]

Would it not be advisable to follow the laid down Boeing/company procedure.

[LEM]

Hi Engineer,
the Boeing NNC says to remove power to the affected equipment, if the source of smoke is known.

Nothing is said about how to do that (yes, I know, "by switch or CB", of course I'm not gonna cut wires with my hands...)

Of course I would perform the whole NNC, but in doing so nothing is done against the smoke coming from behind the CB panel...
You just rush for landing, but....

[Engineer]

Cannot comment on 737

In general for smoke of an electrical nature the procedure is to isolate each electrical bus individually. Starting with the AC buses.

Isolate number 1 generator wait to see if smoke ceases if not reinstate. Isolate next generator on so on. If smoke not caused by equipment powered by ac bus bars procedure will move you on to dc bus bars fed from TRUs.

If fault not on thoses bus bars then procedure moves to battery fed bus bar.

Procedure is designed to isolate in sequence all bus bars hence electrical equipment,whilst maintaining supply to the rest of the sytems, in a sequential order. Eventually coming to the source of electrical smoke.

If you come to the end of the procedure and have failed to isolate system then you have either carried out the procedure incorrectly

or you have Air Conditioning smoke :{ have seen that happen on the Simulator. But that is another story :ok:

[N5528P]

or you have Air Conditioning smoke have seen that happen on the Simulator. But that is another story

Don't stop, your audience is nailed to the seats!

Bernhard

[alexban]

remember talking some time ago with some of my most respectable instructors about this case ,of electrical smoke-fire inflight.
This can be one of the deadliest things that can happen inflight,especially after the disapeareance of the engineers from the cockpit.
It's some amount of work to be done,under stress,and also the necessity to proceed asap to land.
Also the NNC can be sometimes quite long.
The conclusion that I have from my previous discussions is that in such a case (electrical smoke-fire ) the wisest choice would be to depower the plane (as lem says ,gen off) and do a rapid descent inbound landing.
If remains time you may try to sort things out via the NNC..
Time can be very precious,and sometimes it may be not enaugh if you do it by the book...happened more then once
Brgds
Alex