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Can´t open any Maindeck Cargo Door

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Hello!

 

First of all, I have to say that the 747 v3 is a very nice addon! I like it so much!

But I have a problem. I can´t open the cargo doors in the maindeck (side cargo and nose door).

In every plane. (F, ERF, BCF, M). The other doors working right!

I hope you can help me.

 

Best regards,

Robin Plate

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Is your External Power 2 or APU Gen 2 AVAIL? (Not ON.)

 

From the manual's introduction:

 

"When using a cargo variant, the nose and side cargo doors require that a power source be available, but not in use. As an example, if you are using APU power, GEN1 can be used for power, but GEN2 will need to be switched off (left AVAIL) in order for the doors to operate."

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Is your External Power 2 or APU Gen 2 AVAIL? (Not ON.)

From the manual's introduction:

"When using a cargo variant, the nose and side cargo doors require that a power source be available, but not in use. As an example, if you are using APU power, GEN1 can be used for power, but GEN2 will need to be switched off (left AVAIL) in order for the doors to operate."

Just out of interest do you or anyone else here know the reasoning behind this?

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Just out of interest do you or anyone else here know the reasoning behind this?

 

From a quick scan it looks like it's a failsafe to preclude accidental electrically triggered Opening/ Closing whilst in use by ground personnel.

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Shameless plug for the Intro Manual. I know that will probably get tiring to see for all of these things, but we spent a good bit of time coming up with the main things that will trip you up. Have a read through them. I guarantee it'll give you a quicker response than posting here and waiting (moreover, it'll also prepare you with the correct expectations of how things work instead of being frustrated that they're "not working" or "not working correctly").

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From a quick scan it looks like it's a failsafe to preclude accidental electrically triggered Opening/ Closing whilst in use by ground personnel.

 

Or while in flight for that matter, which is the explanation I got from an authoritative source.

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Or while in flight for that matter, which is the explanation I got from an authoritative source.

Maybe I'm being a bit slow but this is the bit I don't really understand. "As an example, if you are using APU power, GEN1 can be used for power, but GEN2 will need to be switched off (left AVAIL) in order for the doors to operate."

 

I don't own the product so cannot read the FCOM myself.

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Rich,

 

When you have the APU running, you have two APU GENs to use: L and R. Most of the time, you would select both L and R to get the most power available to the plane. In order to move the doors, though, you need to de-select one of the GENs such that it only shows as AVAIL (available, but not in use).

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Or while in flight for that matter, which is the explanation I got from an authoritative source.

 

 

In flight - it's no longer an issue as you're no longer connected to Ground Power or APU. It has to do with variable voltage vagaries (fluctuating voltages) of GPU's/ APU's and (over) sensitive sensors on the cargo door mechanisms, etc.

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Many subjects here are what we called RTFM cases when I did techsupport back in the -90th. Read The F¤&/%ng Manual :fool:

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Just out of interest do you or anyone else here know the reasoning behind this?

My theory is that the SSB bus tie contact is open under these conditions; thus, the two AC buses are no longer synchronized (voltages could be out of phase). The motors will operate from either bus, but if it were both then there would be a problem if the power were not synchronized.  At least it makes sense to this engineer.  No other guess I've seen makes much sense so I'm sticking to this theory.

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Many subjects here are what we called RTFM cases when I did techsupport back in the -90th. Read The F¤&/%ng Manual :fool:

 

Thanks for that valuable observation.

 

Aaanyway...it is basically to do with voltage fluctuations across the buses and ensuring an inadvertent close of doors does not happen while crew are in the way loading and unloading, etc.

 

For us - in Sim World - it's a procedure we have to conform with - just like real world - and PMDG have modelled it - like the sticklers for detail they are. Bless them.

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Many subjects here are what we called RTFM cases when I did techsupport back in the -90th. Read The F¤&/%ng Manual :fool:

I don't own the product yet and am therefore not going to read the FCOM yet but thanks for the information from the rest of you. I fly Airbus real world and was merely interested in the logic behind the systems as they have their own little quirks like most aircraft. Thanks again.

My theory is that the SSB bus tie contact is open under these conditions; thus, the two AC buses are no longer synchronized (voltages could be out of phase). The motors will operate from either bus, but if it were both then there would be a problem if the power were not synchronized.  At least it makes sense to this engineer.  No other guess I've seen makes much sense so I'm sticking to this theory.

And actually this is where I was getting confused, from the way I interpreted the information the door power was coming from the GEN which was Avail and not in use however would I be right in thinking it's actually the opposite and Boeing are trying to achieve a single power source or generator for all systems including the doors in order to allevaiate unsynchronised buses, voltages etc. therefore using the single GEN that is switched to ON and thus ignoring the second GEN not being utilised?

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therefore using the single GEN that is switched to ON and thus ignoring the second GEN not being utilised?

 

Yup, that's my conclusion after reading the electrical systems descriptions and on line sources combined with my quite old BSEE degree.

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In flight - it's no longer an issue as you're no longer connected to Ground Power or APU. It has to do with variable voltage vagaries (fluctuating voltages) of GPU's/ APU's and (over) sensitive sensors on the cargo door mechanisms, etc.

APU can still run when you take off ....

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I really don't think cargo sensor sensitivity is the issue here. Isolating the cargo drive systems and main deck cargo doors from the rest of the aircraft means that when you use heavy duty door and cargo drive motors, it doesn't upset the rest of the aircraft. You don't want large voltage fluctuations or power drop outs when you're programming the FMC or aligning the IRUs.

The main deck cargo system can only be powered by APU Gen #2 or External Power #2. Both of these are automatically deactivated when 3 or more engine generators reach 6100rpm (this equates to a certain engine N2 or N3 depending on engine type). So, at well below takeoff thrust, it's not possible to get power on the cargo systems. Also, the power is controlled by air/ground relays triggered by main gear strut compression.

On the real aircraft, when you reach takeoff thrust and are barrelling down the runway, even though you may see the APU AVAIL lights still illuminated, the aircraft electric system logic won't let you use APU electrical power.

The system is almost idiot proof :wink:

Cheers

John H Watson

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Gents,

 

Has nothing whatever to do with power quality, etc.

 

John's explanation is the valid reason.

 

If you'd like to learn more on this kind of design decision, Google "UAL Flight 811 cargo door"

 

The industry learns things the hard way...

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I really don't think cargo sensor sensitivity is the issue here. Isolating the cargo drive systems and main deck cargo doors from the rest of the aircraft means that when you use heavy duty door and cargo drive motors, it doesn't upset the rest of the aircraft. You don't want large voltage fluctuations or power drop outs when you're programming the FMC or aligning the IRUs.

The main deck cargo system can only be powered by APU Gen #2 or External Power #2. Both of these are automatically deactivated when 3 or more engine generators reach 6100rpm (this equates to a certain engine N2 or N3 depending on engine type). So, at well below takeoff thrust, it's not possible to get power on the cargo systems. Also, the power is controlled by air/ground relays triggered by main gear strut compression.

On the real aircraft, when you reach takeoff thrust and are barrelling down the runway, even though you may see the APU AVAIL lights still illuminated, the aircraft electric system logic won't let you use APU electrical power.

The system is almost idiot proof :wink:

Cheers

John H Watson

 

Wow thank you John, so just to clarify the Door will run off ONLY APU GEN 2 or GPU GEN 2 when AVAIL and thus not in use? Meaning that essentially the cargo system is using this generator in the "background" so to speak as it is technically not in use. I would assume then that with APU GEN 2 ON and GEN 1 AVAIL the door would not operate?

 

Time for be to purchase the product and test it myself I guess .

 

Thanks again.

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I would assume then that with APU GEN 2 ON and GEN 1 AVAIL the door would not operate?

 

 

ah.. As I understand it, if you have two sources of power available on the right hand side (i.e. APU 2 and EXT 2) EXT #2 takes priority (but EXT 2 must remain in AVAIL mode). APU #2 can help the power source on the left hand side of the ship to power all the normal stuff. Earlier, I was thinking more along the lines of only one type of power source being available.

 

Note that if you only have one type of power on the aircraft (e.g. EXT #1 and EXT #2) EXT #1 will have to handle all the normal (in air) stuff but it will also have to power all the cargo loading equipment for the lower lobe cargo (including the lower lobe cargo doors). This loading equipment is lower power stuff... and, of course, it's not like a passenger aircraft where you have to power lots of galley equipment and inflight entertainment stuff.

 

I always have trouble finding a book which tells me that this is the way it should be... However, I recall, at least one time, a freighter pilot, during his preflights, switching APU #2 to ON during cargo loading... and freaking me out... but then I realised EXT 2 was also plugged in and in AVAIL mode (and there were no complaints from the cargo loaders).

 

Hope this helps

Cheers

John H Watson

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ah.. As I understand it, if you have two sources of power available on the right hand side (i.e. APU 2 and EXT 2) EXT #2 takes priority (but EXT 2 must remain in AVAIL mode). APU #2 can help the power source on the left hand side of the ship to power all the normal stuff. Earlier, I was thinking more along the lines of only one type of power source being available.

 

Note that if you only have one type of power on the aircraft (e.g. EXT #1 and EXT #2) EXT #1 will have to handle all the normal (in air) stuff but it will also have to power all the cargo loading equipment for the lower lobe cargo (including the lower lobe cargo doors). This loading equipment is lower power stuff... and, of course, it's not like a passenger aircraft where you have to power lots of galley equipment and inflight entertainment stuff.

 

I always have trouble finding a book which tells me that this is the way it should be... However, I recall, at least one time, a freighter pilot, during his preflights, switching APU #2 to ON during cargo loading... and freaking me out... but then I realised EXT 2 was also plugged in and in AVAIL mode (and there were no complaints from the cargo loaders).

 

Hope this helps

Cheers

John H Watson

Thanks John it's very interesting. When I get round to purchasing her I'll have a play around and see what does and does not work, I'll assume PMDG have got it spot on

 

Thanks again

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