a380900
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What's The Deal With Power On?

Fri Jun 06, 2008 12:34 am

I don't quite understand why "power on" is such a big deal for airplanes. I don't remember being aware of it for the A380 for instance.

I would assume that they test every subsystems many times before "power on" so it's not clear to me why linking all these subsystems to a master switch is such a big deal. Can things go wrong?
 
PlaneInsomniac
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 12:42 am

For all I know, the 787 is quite an exception in that it had its roll-out before its power-on. In most modern airliner development programs, power-on happened at quite an early stage.

Whether or not there are going to be many unexpected problems after power-on, is the big question right now. Anybody working with large systems will tell you that even if every part works flawlessly when tested independently, the complete thing may work arbitrarily badly. The 787 incorporates many new technologies, such as a near-bleedless design with an unprecedented number of purely electrical systems.

That said, Boeing and the suppliers now had a lot of time to test everything under lab conditions. I wish the best of luck to them. The most important thing now is that they finally manage to achieve power-on. (Which, according to the latest information, should not take that much longer.)
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Starlionblue
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 2:20 am



Quoting PlaneInsomniac (Reply 1):
Anybody working with large systems will tell you that even if every part works flawlessly when tested independently, the complete thing may work arbitrarily badly.

Indeed.

I think the answer to the original question is that systems are quite complex and it is almost impossible to predict every possible outcome. You can model stuff but the reality is never 100% exactly like your models.

Throw Murphy into the equation and you'll be doing long nights of troubleshooting.  Wink
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autothrust
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 3:10 am



Quoting A380900 (Thread starter):
don't remember being aware of it for the A380 for instance.

It was also a very important milestone for the A380 even with its "sick" complexity, the power on was achieved 2 months later then scheduled.

Here you can see the A380(F-WWOW) power on at 0:30 min ;

http://www.youtube.com/v/WtjTnq5XYcU&hl
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Jetlagged
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 4:03 am



Quoting A380900 (Thread starter):
I don't quite understand why "power on" is such a big deal for airplanes. I don't remember being aware of it for the A380 for instance.

I would assume that they test every subsystems many times before "power on" so it's not clear to me why linking all these subsystems to a master switch is such a big deal. Can things go wrong?

Power on is a critical prgress milestone. Testing on the bench is one thing, but having power safely integrated on the aircraft itself is a significant step forward. Milestones like this are vital for tracking the project's progress against the schedule.

It's not just a matter of connecting the external power.  Wink
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Tristarsteve
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 1:22 pm

If you watch the Airbus film, you can see that at power on all the circuit breakers are tripped, and they start with one battery. Then the second battery and after a while the 400Hz main power. Although all the systems are tested, this is the first time that the electrical looms have power on them when they are connected together. Before each loom was tested individually to its design, but perhaps the designers have made a mistake in designating one pin in one socket! If all is stable, they will set the CBs one at a time and watch what happens. From turning on the first battery, to acheiving full power would take weeks.
 
FredT
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 2:29 pm

The perceived importance of power on probably depends on the number of press releases the company has been able to produce showing that the project is in fact going forward during the months preceding the event. No press releases - big event. Many other press releases - non-event.  Wink
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NoWorries
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 3:39 pm

Whenever two electrical devices are connected together, they cause side-effects in each other. For example, turning on a lamp in your house has an extraordinarilly small but real impact on a generator perhaps hundreds of miles away. In the case of complex electronic systems, , the side effects again are either so small they can be ignored, or if they can't be ignored they have been anticipated and compensated for in the design. Sometimes the devices don't even have to be connected -- just being "near" one another can create side-effects. Again, this can be anticipated in the design. Throwing all of thse systems together into one big bucket has enormous potential for unanticipated side-effects. So they definitely want to go slow -- and there is always the chance some unanticipated set of interactions requires some redesign work.
 
KELPkid
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 5:26 pm

Also everyone, remember that this (the 787) just happens to be the most "electric" plane ever built so far...almost all of the major systems in this bird are electrical! In that sense, the power on is all that more critical...
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nomadd22
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RE: What's The Deal With Power On?

Fri Jun 06, 2008 6:27 pm

You don't just turn on a big breaker. The pilot flips a few switches, but software controls the power up of the god awful number of systems at carefully timed intervals.
Somebody's not just going to throw the main switch in a few weeks. They'll power things up one at a time so they can see the effects of each system on everything else. When they're comforatable enough, they'll power the thing up in a normal fashion, and declare success.
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avt007
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RE: What's The Deal With Power On?

Sat Jun 07, 2008 3:17 pm

For those involved in the building of the aircraft, it's huge! I have rewired helicopters from the ground up, and it's lot of fun to power it up after months of work. There's a real sense of accomplishment involved.
 
474218
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RE: What's The Deal With Power On?

Sat Jun 07, 2008 4:28 pm



Quoting A380900 (Thread starter):
I don't quite understand why "power on" is such a big deal for airplanes.

Let me give a small example of why "power on" is important. Think of the standard coach class seat, it has controls for the following: reading light (on/off), entertainment system (on/off), channel selection, volume control, FA call button. So there are minimum of five controls on each seat, multiply that time the number of seats and each one can not be verified to work untill after "power on".

Now think of all the other systems on the aircraft, flight station instruments, lights, circuit breakers, flight controls, galleys and I could go on and on. Any anything and everything
that requires electrical power can not be tested until there is "power on", and all these tests take time, so the sooner there is "power on" the sooner that the aircraft can be made ready to fly.
 
roseflyer
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RE: What's The Deal With Power On?

Sun Jun 08, 2008 6:00 am

At Boeing there are three very significant events in the production of the airplane. They are:

Power On
Oil On
Hi Blow

Wing to body join is as simple as it sounds yet is a crucially important step especially since wings and fuselages are made by separate companies on most Boeing jets.

Power on is the integration of the electrical system as described.

Oil on is actually hydraulic fluid being added for the first time. It's significant since hydraulics unlike electric systems are difficult to be checked separately, so there are a lot of leaks and problems identified.

Hi Blow is where the fuselage is pressurized for the first time.

These three tests, are significant since they are for the three sources of power on a plane: Electrical, Hydraulic and Pneumatic. Power on is the biggest milestone, but we'll see when the 787 gets these done.
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