Hello everyone,

I introduce myself : I'm Alexandre from French West Indies (and a French Speaking guy, so in advance, sorry for my English), new to the forum.

I start directly : Is there any way or any procedure that allows to open the gear doors at ground as shown on the following screenshots (OneDrive link) ?

https://1drv.ms/f/s!AgR7ZAZB54P1iZomov68OS41gPmPSQ

Of course, I've already tried the "alternate gear extension" procedure, who work in flight, but not at ground (what seems logical).

The PMDG product support seems to be unavailable at the moment...

Anyone have an idea?

Thank you in advance for your answers/clarifications.


Alexandre aka AAlphaSierra

Hi

From my memory you can only open the doors if you mechanically unlock the doors. Free fall item.There are some handles in the vicinty of the doors so you can unlatch the doorlocks. More a maintenance item than i flightcrew item.
Regards.
Jo va Bra

Normally this is done with the manual door release handles at the doors. These are not simulated.

If you use the alt gear extention, the doors will be kept closed by the hydraulic system. Perhaps switching hydr system 1 and 4 to OFF would open the doors using the alt extend.

Jo va Bra & fleng200, thanks for your clarifications about the manual door release (that is not simulated in the PMDG 747v3 so?).

Of course, I've tried the alt gear extension with all hydr system off. In flight it's work, but not at ground.

Regards.

 

AAlphaSierra

Alexandre,

Rene is correct and in theory the Alternate Extend should open the doors on the ground as well as in flight but the only reason to open the doors on the ground is for maintenance.  Leaving the gear doors open (particularly the body gear doors) can damage the gear doors due to the way the Body Gear doors rest on or near the tires at low weight.  If the aircraft is loaded or refueled with those doors open it either jams the doors (best case scenario) or breaks off the hinges.  We typically open the doors for whatever work or inspection needs to be done and then immediately close them up to prevent problems. 

The second issue that comes into play is that once the Alternate Extension has been activated,  you can't close the doors on the ground.  You need to cycle the gear handle to reset the system or cycle the manual gear door release levers (which aren't modeled) to allow the doors to close again so not something I would recommend.

Hope that clarifies

Thank you for that clarification. 

I don't forget that PMDG has done a really great job with this V3 747-400... We wait patiently (or not) the-8! 😉 

 

AAlphaSierra

14 hours ago, Jet Tech said:

Rene is correct and in theory the Alternate Extend should open the doors on the ground as well as in flight

Paul, do you know if this applies to those aircraft which have a reset system which keeps the alternate gear motors running through a full cycle even if you prematurely put the alternate gear extension switch back to off? A maintenance manual procedure (32-35-00 p501~) mentions pulling the alternate gear extension reset circuit breakers in the Main Equipment Center prior to doing alternate gear extension door checks. Does this mean that the system fitted to newer aircraft (and retrofitted aircraft) inhibits door opening? Or does pulling the CBs allow the correct parts of the circuits to be checked?

I had a look at the wiring schematic, but I can't make any sense of it.

 

16 hours ago, Jet Tech said:

The second issue that comes into play is that once the Alternate Extension has been activated,  you can't close the doors on the ground.  You need to cycle the gear handle to reset the system

The same maintenance procedure (above) mentions moving the lever to OFF prior to checking the doors. I can't see the point of this. Doesn't the alternate gear extension cable system position the hydraulic valves so that hydraulic power doesn't impeded the door opening/gear deployment?

Dr Quavion  :P

 

Looking through the Schematic manuals it looks like our first 10 birds didn't have the Auto Reset system installed but the last 6 did.  I know our company policy was to always perform the Auto Reset check after any alternate extension to make sure the motors make the full circle back to normal and didn't stop half way around. 

 

The second point I think is just a safety precaution as the doors should be locked out as described but you know Boeing doesn't want to take the chance one isn't locked and takes someone's arm off accidentally.   They certainly move pretty quickly

7 hours ago, Jet Tech said:

Looking through the Schematic manuals it looks like our first 10 birds didn't have the Auto Reset system installed but the last 6 did.

Similar proportions to ours. I was also looking at the BA schematics (I think everything after G-CIVB has the newer system).

7 hours ago, Jet Tech said:

The second point I think is just a safety precaution as the doors should be locked out as described but you know Boeing doesn't want to take the chance one isn't locked and takes someone's arm off accidentally. 

By "checking the doors", I meant by pushing the alternate switches in the cockpit (not by climbing in the wheel well 😛 ). The doors can still trap your arm in freefall if you're in the wrong place.

I'll continue my struggle to analyse the circuit. My biggest problem is understanding how the internal and external microswitches attached to the motors influence the relays at specific times.

 

Thanks,

Cheers,

JHW