HappyPass
23rd Feb 2011, 10:44
Hi, I'm a aviation enthusiast who likes very much to delve deep into the inner workings of an airplane and of aviation in general.
I'm browsing through a 757 CBT (in the glory of a 640x480 resolution) and found a thing that for me doesn't add up.
It is stated (if I'm not mistaken) that when one engine is started and external power is connected, the engine (say the right one, left still not running) powers the respective (right) bus as soon as the generator spools up, while ext power powers the other (left) bus. This also complies with the always-2-power-sources-thing.
However the course also states that when the aircraft is parked at the ramp prior to shutdown and ext power is connected (manually selected on), both engine generators are disconnected and the main busses are powered by the ext power only.
Should not external power connect to a bus only when the respective engine generator is off? Why is the behaviour different at the beginning and at the end of the flight, are there particular reasons for this to happen and so on? Since I don't understand the logic behind this - likely because I miss some pieces of the puzzle - I would like to be enlightened on the topic.
Thanks in advance best regards,
Adrian Owen
I'm browsing through a 757 CBT (in the glory of a 640x480 resolution) and found a thing that for me doesn't add up.
It is stated (if I'm not mistaken) that when one engine is started and external power is connected, the engine (say the right one, left still not running) powers the respective (right) bus as soon as the generator spools up, while ext power powers the other (left) bus. This also complies with the always-2-power-sources-thing.
However the course also states that when the aircraft is parked at the ramp prior to shutdown and ext power is connected (manually selected on), both engine generators are disconnected and the main busses are powered by the ext power only.
Should not external power connect to a bus only when the respective engine generator is off? Why is the behaviour different at the beginning and at the end of the flight, are there particular reasons for this to happen and so on? Since I don't understand the logic behind this - likely because I miss some pieces of the puzzle - I would like to be enlightened on the topic.
Thanks in advance best regards,
Adrian Owen