B737 question

[msathre]

Two questions that I've read different theories about.

First: Starter does not automatically cut-out at 46%, so you manually put it from GRD to OFF. I understand that by putting it manually to OFF, you override the start switch solenoid that was supposed to automatically de-energized and put the start switch to OFF.

I read somewhere, sometime, long ago, I think, but are not sure :) That when this happens, there is some "test" and some warning system that will not work properly. Anyone know anything about this?

Second question:
How much do you save, or how important and why is it to put in wind directions and strength in you route page in the FMC? If anyone can explain this in a good matter, I would really appreciate it :)

[bfisk]

Hello,

This is for the NG; there might be differences between the classic and the NG.

The starter is supposed to automatically disconnect at 56% N2, not 46%. You would then observe the starter switch popping back to OFF/AUTO, the bleed air duct pressure flutters, and the START VALVE OPEN light goes out. If the starter does not disconnect, there is a QRH procedure for it, which essentially tells you to move the start switch yourself within 120 seconds of engaging it.

As for the FMC, you don't really gain or lose anything per se, but having the correct winds in the RTE DATA section provides you with better time and fuel predictions, which provides a bit of relief in todays world of flying around with close to min.fuel.

The FMC does use head-/tailwind in it's computation of ECON speeds, but will use actual winds in lieu of entered winds, so it will fly faster in a headwind and slower in a tailwind, even without any data entered.

Good luck.

[msathre]

Thanks for replying bfisk

Its 46% N2 on the classic, and you put it manually to OFF if it doesn't go automatically. But the procedure is not my question, my question is: Is there any warning system or other systems that might be affected or not work properly because of this? I read that somewhere a long time ago, but i can't find the book about it.

Anyone else have some inputs to the FMC question?

[BOAC]

ms- I am not aware of any safety system that would be affected by the action, but life is full of surprises! I suppose it depends really on why the solenoid failed to de-latch.

I rarely bothered with leg winds on the 737 FMS since as above the FMC uses actual winds The only time they are important is if you have to meet a particular 'slot' somewhere, as in the early days of Ops into Pristina when we had a target of +/-5 minutes in a 15 minute window. I guess if you are 'nervous' about fuel, having each leg wind in might re-assure you, but if an unexpectedly high headwind on a leg causes a 'Using reserve' warning, there are always the PLOG winds/Met charts to look at.