Hi Guys,I am in Singapore for the next two weeks looking after my mum. Out here I have full use of all my fathers 747F operation manuals and training CD's so if anyone has any obscure questions on the aircraft let me know. So far I have found a huge amount of information to help fill the gaps in my knowledge.Rob

Thanks for the offer, Rob...On the 744F, why is it necessary to have the #2 APU or #2 EXT power set to AVAIL, rather than "ON", when loading cargo? Will loadshedding problems be created if it's not like this... or will cargo loading simply not happen with the switches ON.(I had problems finding this in my books)Cheers.Q> イアン

This is the first bit of information I have found. A huge amount to get through :)Note: If both EXT PWR 2 and APU GEN 2 AVAIL lights are illuminated, main deck cargo handling equipment power is provided by EXT PWR 2. Selecting EXT PWR 2 ON transfers main deck cargo handling power to APU GEN 2. Note: On freighter airplanes, when the main deck cargo handling bus is powered by APU generator 2, pushing APU generator 2 control switch causes main deck cargo handling bus to lose power.I will keep looking into why this happens and ask my father if I get stuck.Cheers Rob

A bit more -Main Deck Cargo Handling Bus (freighter)The main deck cargo handling bus is powered on the ground when external power 2 or APU generator 2 is available. An interlock prevents either source from powering main electrical busses and the main deck cargo handling bus simultaneously. Pushing the available Power source switch ON deengergizes the main deck cargo handling bus. When both external power 2 and APU generator 2 are available, external power is used. Pushing External 2 switch ON transfers main deck cargo handling loads to APU 2Rob

Thanks, guys.."An interlock prevents either source from powering main electrical busses and the main deck cargo handling bus simultaneously."So it IS airplane logic. I remember working on Classic Combi 747's and was under the impression that selecting EXT #2 was only done as a precautionary measure rather than system logic.Cheers.Q> イアン。

Qavion,Quick question, did you used to fly the classic 747? I have been trying to find some online information (I own the RFP 747 and have the Book that came with the boxed version)Rob

No, sorry, I didn't fly it...I did work on them for 20 or so years as an engineer, but only in limited field. I couldn't tell you how to fly 'em.Cheers.Q>

Hi Q,let me translate ;-) into your language.There are two interchangeable main deck cargo handling relays in P715 in the MEC. These bad boys are 28V DC controlled, 3 pole, double throw, center off type relays. The relays contain two coils, one for external power and the other for auxiliary power. The separate outputs from BCU No. 2 are each capable of 500 mA continuously at 28V DC. Only BCU No. 2 controls the application of power to the main deck cargo handling bus. The two power sources are the No. 2 external power and No. 2 APU generator, as already mentioned by Rob. External power No. 2 has priority. To get it powered by EXT No. 2, the BCU checks the average of all three phases for frequency, voltage and phase rotation. The BCU also monitors air/ground logic and IDG speed inputs.Shoot. The rest is nasty B2 stuff...I don't want to dig any deeper.regards,delcom