Hey Guys!I'm using AES and have a question regarding the deactivation of the GPU in respect of pushing back the airplane.After I deactivate the GPU without the engines (=generators) running all of my settings in the FMS are gone. It seems that there is no chance to deactivate the GPU without activating the generators otherwise there is not enough power left for the flight instruments to work and everything in the cockpit goes dark...How is that handled in the real aircraft? Do they first start all engines before the aircraft is pushed back? Isn't the BatteryPower enough to feed all the flight instruments for a couple of minutes?Thanks for the answerMat

Hi Mat,You need to sign your full name before someone can help you. Thanks.

Ok - just updated my signature ;-)Now everybody is very welcome to help me ;-)

I don't know how it's handled in the real aircraft, but no airliner I'm aware of can power the whole flightdeck off the battery, not even for a couple of minutes. The battery only powers standby equipment. Battery starts are always with limited indications. However, I don't lose the FMC programming when the GPU is disconnected. When the engines are running and gens online I can switch the FMC back on and the flight plan still loaded.I too would be interested to know what the real aircraft procedures are.Kevin

That wasn't so bad!Speaking generally, J41's (and most other commuters) park at spots that do not require a pushback. Usually, the GPU stays attached to the airplane as the #1 engine is started. Once it is started and the generator is online, the GPU is disconnected and then #2 is started.The EADI's, EHSI's, etc, are powered via the L and R Essential Avionics Busses, and these busses can only be powered by 1) their respective generator through the associated Generator Line Contactor, or 2) by the GPU through the Cross-Tie Bus. Battery power alone will not power the major avionics components. Notable exceptions are the #1 RTU, the CDU, and the standby instruments.Since the avionics master switches must be off for engine start, there is usually a scramble to accomplish checklist items once the engines are started. V-speeds must be re-entered, heading bugs and courses reset, the FMS setup (thankfully, it's a simple process), etc.It's even more rushed when you're doing a single engine taxi, and you're starting the other engine while in line for takeoff. Thankfully, FSX makes single-engine taxiing all but impossible, so you won't have to deal with that aspect...Edited to add:Since it's pertinent to the discussion, I should add that, yes, you can do a battery start if required. This is usually done if the station's GPU is inop, or the airplane won't accept the power because the volts/freqs are out of tolerance. Another time you'll do a battery start is if you're de-icing at stations where you can't de-ice at the gate. You'll start normally at teh gate, taxi to the de-ice pad and shutdown. After the de-icing is complete, you do a battery start.

Thanks, guys!However one thing struggles me: Why does Kevin have the FMS programming after he disconnected the GPU and why does my FMS reset? I assume Kevin was also referring to disconnecting the GPU before activating the generators!?

The FMS storing info despite a power loss was a bug. wink wink, nudge nudge. ;)

Oh I see... ;-) But it was much more friendly this way :-D Can't they undo this? lolEDIT: @Nick: Are they doing all the FMS stuff at the deicing pad then - after they started the engines?

Thanks, guys!However one thing struggles me: Why does Kevin have the FMS programming after he disconnected the GPU and why does my FMS reset? I assume Kevin was also referring to disconnecting the GPU before activating the generators!?

Yes. I programmed the FMC on GPU power, disconnected the GPU, pushed back, started engines and switched the FMC back on. When I first tried this it looked as if the FMC had dumped the programming, but it hadn't. It powered up with the usual screen. I initialised the FMC position as normal and found the flight plan still loaded.Kevin

I don't own the J41 but heres an interesting way to do pushback "Reverse Thrust" after both engines are started.

Goes against everything I've been told about pushbacks but hey they did it here.Sean Green

Reverse thrust push back is something that is company specific apparently. Some companies will allow, some won't... can cause all sorts of FOD... oh and the problem of tipping up onto the empennage when braking... :(There is a warning on the panel in the PMDG JS41...Andrew

Is there a "time limit" you have to power the FMC back up before it dumps data. I pushback with avionics off/disconnected GPU and by the time I start engines and reestablish FMC power, it's still dumping the flight plan for me (and actually AHARS data too). What am I doing wrong?

There is a warning on the panel in the PMDG JS41...

That actually applies to pushing the aircraft back (using a truck) with engines running, not under own power. Some googling came up with this airworthiness directive:AD/J4100/15 Placard to Prohibit Aircraft Pushback with Engines Running 4/2008 DM Applicability: All Jetstream Series 4100 aircraft. Requirement: Action in accordance with BAe Regional Aircraft Alert Service Bulletin J41-11-024, original issue, or later CAA/EASA approved revision. Note: UK CAA AD 004-05-99 refers. Compliance: For aircraft with a nose landing gear shock strut which has already achieved 12,000 landings, install the placard specified in the Requirement document within 30 days after 20 February 2008; unless already accomplished. For all other aircraft, the required placard must be installed when the nose landing gear shock strut reaches 12,000 landings. This Airworthiness Directive becomes effective on 20 February 2008. Background: Operators of high time aircraft have reported they are approaching the published life limitations for nose landing gear parts. The mandatory life limitations for some nose landing gear shock struts, currently running at 12,000 landings, are constrained by the life of the towing bracket. Pending introduction of a re-identified shock strut towing bracket, an operational restriction is imposed to prohibit aircraft pushback with engines runningI just pretend that the "re-identified shock strut towing bracket" thingy has been installed in my JS4100, and push back with engines running. Or park such that no pushback is required.

Gents-I think the larger picture here is that you are all too used to flying a jet. I think it is safe to say I have more JS4100 time here than anyone else in the room... and i've NEVER pushed back in a JS4100.It really just isn't done except maybe in some VERY unusual parking spots. One of the really great aspects of the J41 was our ability to rotate around the inside main landing gear in a slow speed turn. The ability to accomplish this pivot without jarring the brakes and throttles was what separated the good JS4100 drivers from the mediocre. At our line, we tended to be competitive about it- and I carried a ruler in my flight kit to measure the performance of my fellow upgrade classmates to see how close they'd get the nose gear to the stop mark on a curved lead-in line. (even harder than it sounds...)EDIT: Someplace out there is a fantastic photo of the T-Gates at KIAD from the 1994-1999 period when our line would cram 20+ J41s into rows two and three deep in an area hardly large enough for a football match. (Normal football- not "American" football, mind you...) I searched but cannot find it... If anyone finds it- please add to this thread...

I think we are asking here: WHAT IF a JS41 has to be pushed back via towbar and tractor ? Would the FMC simply be programmed after start? e.g. using AES.