Plane Power Problems

[steve66]

Why do it at each and every gate? They obviously all have the same problem. And it is not an intermitent problem either. About 20 sec of monitoring should have shown the power is either good, or not.

 

[kc8dxx]

Amc

Amc

I'm surprised that you aren't getting an engineer from the ground unit company and an engineer from the plane company to meet on site to determine what's happening. Go to the source of knowledge about this.

A suggestion to the company, from the airline, that they are going to file a formal complaint at AMC may be necessary. For those outside of the airline industry, AMC is a regular get-together of airlines and airline suppliers. The big feature is a forum where the airlines complain, and the suppliers answer the complaints. In front of everyone. It can be rather embarassing if the supplier doesn't have a good answer.

Problem lasting 9 months suggests the supplier has no clue.

 

[dbuckley]

If the phases were consistently reversed(ie.the wrong direction) on all these 30 gates,I would expect every plane(all MFRS.) would be tripping their A/C breakers during this instant of transfer of power source from plane power to airport power.

That is why I asked specifically if the airport - today - serves 777s and A340s which have instant power switchover. Older planes didn't have semiconductor switch, they were mechanical, and hence went through 'off' between onboard and GPU power, hence the cabin lights going out at switchover.

My guess is that planes didn't care about phase sequencing when they had the old way of switching, but with semiconductor static switches doing a no-break changeover then phase sequence is a big issue, as if you cant match phase sequence then the static switch will refuse to switch.

Money still on iWires phase sequence is wrong, until you tell us it works today on a 777 and A340s...

 

[ghostbuster]

That is why I asked specifically if the airport - today - serves 777s and A340s which have instant power switchover. Older planes didn't have semiconductor switch, they were mechanical, and hence went through 'off' between onboard and GPU power, hence the cabin lights going out at switchover.

My guess is that planes didn't care about phase sequencing when they had the old way of switching, but with semiconductor static switches doing a no-break changeover then phase sequence is a big issue, as if you cant match phase sequence then the static switch will refuse to switch.

Money still on iWires phase sequence is wrong, until you tell us it works today on a 777 and A340s...

My contact is not aware of any problems with the above planes with respect to the problem being discussed in this thread.



Typical mechanical( non-static switch) transfer switches will transfer between different power sources within 3-4 power cycles.

3 phase rotational loads generally have "lots" of inertia and will not stop in these 3-4 power cycles.

Therefore,if the airport power had reversed phases ,all the A/c breakers would trip each time in all the planes.(ie.3 phase motors don't like a sudden change in the direction of the imposed magnetic field)

I really think it could be something like: voltage T.H.D. limits being exceeded,outside the band of frequency tolerance limits,voltage phase angle problems(not exactly 120 degrees),voltage spikes on the waveform(scr firing problems) etc.

I will be on a crash job in Europe for the next 2 weeks.I will try to answer any other questions when I return.Note:Have not received approval from this customer, as of yet ,to proceed any further with this problem -he is now on the backburner and maybe will be soon off the stove completely.

 

[dbuckley]

Yeah, having read a bit I now dont think it can be phase either, as (a) the rotation order is specified in the design of the plug, and (b) there are lots of three phase rotational sensitive loads on planes, including stuff like the fuel pumps(!). I earlier was thinking that although there's three phase juice available, maybe its all single phase loads, but that one is out.

I'm declaring this one 'wierd'.

 

[steve66]

I don't really see anything really weird here. (Except the fact that nobody has put their foot down yet and demanded that the problem get solved.)

In my opinion, the plane manufacturer should be the first one to send someone to check out the problem. Like someone else mentioned, its odd that the planes are smart enough to check the power, but not smart enough to tell you just what's wrong. Someone who knows the planes electronics should either fix the problem, or tell you just what exactly is wrong with the power.

Steve

 

[dbuckley]

Ran this past my aeroplane mechanic training friend, who is actually an "everything but the engines and wiring" trainer, but he did say "ground power wont connect - sounds like your 400Hz isn't 400Hz".