737NG Transfer bus fail

[Lucky Angel]

Just got back from my LPC and having tried a transfer bus failure in the sim i was surprised to notice that after finishing the QRH we had absolutely no resul. In the QRH it states

Conidition:A TRANSFER BUS OFF light illuminated indicates the related transfer bus is not powered
ENGINE GENERATOR SWITCH..............ON
If TRANSFER BUS OFF light remains illuminated:
APU(if available)...........START & ON BUS

The problem is that after doing this drill you get no result what so ever. My question is:Is it a sim problem or is it a checklist problem?????

[Shaka Zulu]

It should normally work the way your QRH describes it, maybe there was a fault with the connection relay (Buss Tie Breaker) that makes it unable to connect to the Transfer Bus Bar, and part of your simulator check?

[seat 0A]

Lukcky:

My question is:Is it a sim problem or is it a checklist problem?????

There is always the 3rd option:

Maybe the transfer bus has failed!:ooh: :\

[wrenchbender]

Wouldn't the Engine Generator Switch be already in the "ON" position? Are you sure it doesn't say......

ENGINE GENERATOR SWITCH........OFF, THEN ON.

[Wizofoz]

wrenchbenber,

They are momentary switches. They don't stay in the "on" position.

[Lucky Angel]

That doesn't actually solve my problem guys. When the QRH is completed it is supposed to solve the problem or tell you what to do if problem not solved ie land at nearest suitable airoprt.
In this case when the checklist is complete it doesn't solve the problem and doesn't tell you what to do next.
I know many of you will say to use some skill and common sense and improvise but that is not the point. Here we have a case where Boeing maybe has a wrong or incomplete checklist for this problem.

[seat 0A]

Here we have a case where Boeing maybe has a wrong or incomplete checklist for this problem.

Come on.. don`t overreact. :{

So the transfer bus is off. Not resettable. allright.
You loose some equipment.

There are more failures in the QRH where mr. Boeing doesn`t give you any fatherly advice about what to do next. And luckily so. Because that is what YOU get paid for.

If it`s really serious, it`s land at nearest suitable airport. If it`s not serious enough, well it`s your call.

[LEM]

On Classics, the cklist says: BUS TRANSFER SWITCH.... OFF THEN AUTO.

The transfer bus is a large piece of metal, difficult for it to break...
Most probably the transfer relay has got a problem, and that's why the Transfer bus off sensor is located NOT on the bus itself, but on the "center position" of the relay (the relay is magnetically attracted on the side with current - one of the two Generator busses - center position means not attracted by any side, thus open).

Resetting the Bus transfer switch may solve the problem.

If not, check the Transfer bus CIRCUIT BREAKER.
If it is popped, you have two options: resetting it or leaving it alone.

What to do?
We know the dangers of resetting a cb...

Since the real problem with this failure is losing one of the two pilots flight instruments, I suggest:
1) if in good weather, keep it popped, don't risk further electrical problems.
Pilots Flying becomes the non affected side. Easy.
2) if in IMC, better to have two pilots crosschecking each other.
Try ONE cb reset.

Note: with a Transfer bus cb popped, the amber light on the ovhd panel will be off!
Hower, you can easily recognise this typical scenario looking at the Aft fuel pumps lights... the one illuminated corresponds to the Transfer bus failed.


One more trick might work: if the relay cannot connect to his normal side, you can try forcing it to connect to the other side.
How?
Turning the Generator bus off on the affected side!

So far for a Transfer bus off. I'm not familiar with NG, but I'm afraid the conditions you stated in your initial post, Lucky Angel, are not correct.

Anyway, hope this can help.

LEM