737-300 questions queries

[N1 Limit]

Hi chaps

I’m busy with self-studying for the 737-300 course,however there are few questions on systems that are bugging me,here’s an example belo :

Generator Drive Disconnect switch when operated disconnects the Generator Drive:

1)From the generator in the event of a Generator Drive malfunction
2)From the engine in the event of a Generator Drive malfunction,only if the engine has been shut down first
3)From the engine in the event of a Generator Drive malfunction

I chose the last answer No3 but apparently it ain’t the good answer,can anyone shed some lights with me on the matter?I truly appreciate it

[Flight Detent]

..if it was an NG, the last answer seems right to me!

Cheers...FD...:)

[cribble]

From my B737-300 FCOM.....(my bold)

"Each generator drive is a self-contained unit consisting of an oil supply, cooler,instrumentation, and a disconnect device..."

and

"....this switch disconnects the generator from the engine in the event of a generator drive malfunction.."

Not much help for the question posed, I'm afraid, since the description is explicit that the disconnect device is part of the generator drive.:confused:

Another company's FCOM may have slightly different wording.

[Capt Pit Bull]

<engage patronising mode>

Consider the following:

Is there any point in having the generator drive turning if the generator is disconnected from it?

If the generator drive was failing mechanically would you like an option (short of shutting the engine down) to stop it turning?

Bearing these points in mind, where would YOU place the disconnect if YOU were designing it?

pb

[rudderrudderrat]

Hi Capt Pit Bull,

The original query was why Ans 3 is considered incorrect. (The one I would have chosen).
Sorry - but I don't understand your point or your <patronising mode>.

[N1 Limit]

That was actually much clear,there's no point in having the Generator Drive turning if the Generator is disconnected.That answer the question short and concise

[Capt Pit Bull]

Hi Rudder,

lol, yes, I guess I should RTFQ myself! d'oh!

Answer 3 is the best thats available, although if there was something about the gearbox that would be a better answer, although insofar as the gearbox can be consdiered part of the engine I suppose its fair enough.

(my general point is that most aspects of aircraft systems can be figured out if you understand the point of them. I'm naturally lazy and would rather understand than memorise. Which is kind of patronising becuase it implies a proportion of our profession prefer to memorise rather than understand, which is why I am a bit of a git)

N1, Who says answer 3 is no good? What answer is offerred as being correct?

[rudderrudderrat]

Hi Capt Pit Bull,

We are similar in that I try to understand the systems rather than just memorise. I still don't understand the logic behind Airbus A320 Fuel L & R TKS LO LVL though - but that's another thread.

Glad we agree.

[N1 Limit]

Well it's an online question i did and it stroke me that's why i jotted it down to put in in this forum so that u guys shed lights on that,there are other few questions that merit discussing too but let's argue on this one first.

[mainwheel]

N1,

The correct answer would be A.

The disconnect switch enables a worm drive "inside" the CSD to separate the gears to a non engaged position.

The CSD is still being driven by the Engine, but only the input shaft is turning.

The rest of the CSD and the Generator are stationary.

It cannot be reset in flight, only on the ground.

[Capt Pit Bull]

Mainwheel, I can see what you're saying but it seems to me to be a fundamentally misleading answer as it implies there is a disconnect between the drive (as a unit) and the gen.

Still, badly worded mutiple choice questions are the norm in this industry so why worry about it too much. Nobody here disputes how it works which is the main thing.