744 Engine Fire bottles

[Tonic Please]

Hello,

Forgive my purpose but it's the information I'd like for mere understanding.

I have the PMDG add-on for FSX (I know, I know, it's only a simulator!) and, being the same price nearly as FSX itself, it's jam-packed with 90%+ of 744 bits and bobs so very 'realistic' in terms of whats possible in the simulator world. It was designed by pilots, too, so ease up a little ;) Here is a link so you can see what it includes: PMDG Simulations (http://www.precisionmanuals.com/pages/product/744x.html) - I can't find the longer list, typical).

Anyway, one can set failures so I set an engine fire 2 minutes after take-off. Whilst I followed the procedures and landed successfully, a few things occured to me re. the real world.

1. On the EICAS page, once I have pulled the fire switch and turned it (to the left, first, for ex.), what does the yellow caution "BTL LO ENG R A" (or B to the right mean?).

2. Do you use rudder trim to help keep the wings level and nose more centralised?

3. What is the difference between pulling the fire switch and twisting it and which way do you twist and why? Pulling is arming?

4. Would you still use A/T mode with an engine on fire or simply shut down? What about regular autopilot?

I guess that's all. Thanks very much!

TP.

[16down2togo]

1. BTL LO means that the respective bottle A or B on the wing (on the engine with RR) is emptied
2. of course everything that helps but keep in mind that with power changes you still have to control more/less rudder
3. pulling is arming the squibs on the fire bottles and more important closing the engine fuel and pylon valves so no more fuel enters the engine and strut,
turning L or R empties the respective fire bottle
4. autothrottle and autopilot still work beautifully with one engine shut down on a 744, you can still do a low vis autoland in this config.
Have fun

[spannersatcx]

Pulling the fire handle arms the system, closes the fuel, hydraulic, pressure regulating and shut off valve, and trips the generator field. After the bottle is discharged, the flight crew will be notifed the condition by advisory EICAS messages

[Tonic Please]

Ah, most grateful for responses. I didn't suppose A and B means left and right wing. Logical I suppose.

Thanks kindly.

[SMOC]

A/B is bottle A and bottle B, two large bottles in each wing near the inboard pylons. Total of 4 bottles per A/C. A/B on the left and A/B on the right side.

RR uses two small bottles installed in each engine inlet nacelle total 8 bottles per A/C. A/B each engine.

[Tonic Please]

Thank you for the clarification. It makes sense now! :ok:

[NSEU]

I'm not aware of any arming function on 744 engine squibs (not electrically, anyway).

Pulling the fire handle, however, may allow you to turn the handle afterwards (e.g. some kind of mechanical interlock, like sticking a key in a lock and turning it)

Rgds
NSEU

P.S. A good test for a desktop simulator:

On the real aircraft, you can only pull the fire handle out if:
1) The respective fuel cutoff lever is in OFF, or
2) The fuel cutoff lever is in RUN and, at the same time, a fire has been detected, or
3) You use the hidden mechanical override button behind the handle (at any time)

[spannersatcx]

That's what is says in the AMM description and operation.

[NSEU]

True, the AMM does use the word "arm", but, electrically, nothing appears to happen in the extinguishing circuit when you pull the handle. There are no additional electrical contacts for "arming" shown in the diagrams, unlike, say, the Stab or Aileron Trim.

Cheers
NSEU

[spannersatcx]

what about mechanically though?

There are 2 switches in the handle, from the hot batt bus > squibs, until you pull the handle you can not fire the bottles because you can not make the switches to complete the circuit. So by pulling the handle you arm the system ready to fire when you rotate the handle and make the switches complete the circuit and bang!

[NSEU]

I'll agree to the "mechanical" arming, Spanners ;) It's unlikely that the handle can be turned when pushed in (at least not without the handle going "bang").