PlaneInsomniac From Canada, joined Nov 2007, 807 posts, RR: 0
Reply 1, posted (7 years 5 months 3 weeks 4 days 21 hours ago) and read 4319 times:
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.)
Am I cured? Slept 5 hours on last long-haul flight...
Starlionblue From Greenland, joined Feb 2004, 17427 posts, RR: 66
Reply 2, posted (7 years 5 months 3 weeks 4 days 19 hours ago) and read 4265 times:
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.
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.
"There are no stupid questions, but there are a lot of inquisitive idiots."
Jetlagged From United Kingdom, joined Jan 2005, 2611 posts, RR: 25
Reply 4, posted (7 years 5 months 3 weeks 4 days 17 hours ago) and read 4221 times:
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.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
Tristarsteve From Sweden, joined Nov 2005, 4265 posts, RR: 32
Reply 5, posted (7 years 5 months 3 weeks 4 days 8 hours ago) and read 4110 times:
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 From United Kingdom, joined Feb 2002, 2185 posts, RR: 25
Reply 6, posted (7 years 5 months 3 weeks 4 days 7 hours ago) and read 4078 times:
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.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
NoWorries From United States of America, joined Oct 2006, 539 posts, RR: 1
Reply 7, posted (7 years 5 months 3 weeks 4 days 6 hours ago) and read 4048 times:
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 From United States of America, joined Nov 2005, 6760 posts, RR: 3
Reply 8, posted (7 years 5 months 3 weeks 4 days 4 hours ago) and read 3984 times:
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...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
Nomadd22 From United States of America, joined Feb 2008, 2079 posts, RR: 0
Reply 9, posted (7 years 5 months 3 weeks 4 days 3 hours ago) and read 3937 times:
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.
Avt007 From Canada, joined Jul 2000, 2132 posts, RR: 4
Reply 10, posted (7 years 5 months 3 weeks 3 days 6 hours ago) and read 3801 times:
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 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 11, posted (7 years 5 months 3 weeks 3 days 5 hours ago) and read 3781 times:
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 From United States of America, joined Feb 2004, 10566 posts, RR: 52
Reply 12, posted (7 years 5 months 3 weeks 2 days 15 hours ago) and read 3689 times:
At Boeing there are three very significant events in the production of the airplane. They are:
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.
If you have never designed an airplane part before, let the real designers do the work!