What RPM do flight control motors spin at?
 

I'm writing a book of fiction and I'm trying to figure out how to use parts off of a 777 to create alternate power sources.

One idea is to create a wind-powered generator. That requires preferably a DC motor that normally spins at less than 1,000 RPM. I know the 777 has many surfaces controlled by flight control motors - and I'm pretty sure they're powered by 28V DC. My questions would be:

1) Roughly how many of these flight control motors are there?
2) Do they typically run at low RPM? (less than 1,000)

I considered using the 28V DC alternators that are on the plane, but it seems they have very high RPMs - which means they wouldn't work well mated to a low RPM wind system.

Any help is appreciated!
thanks,
ken

According to this article, they use permanent magnet generators to generate AC that is then converted for use, so your idea may not work.

Page 4, 11.4.5 ELECTRICAL POWER

http://www.davi.ws/avionics/TheAvion...ook_Cap_11.pdf

not sure what you mean by flight control motors?

Motors
 

A book of fiction would certainly need DC alternators. A better solution would be AC batteries

The flight controls for a 777, like most Boeings, are powered hydraulically. Newer "fly by wire" aircraft control the hydraulic power units electrically. Old school aircraft have cables from the flight controls to the hydraulic power packs.

One, two or three PCUs operate each control surface. One PCU controls each spoiler, two PCUs control each aileron, flaperon, and elevator, and three PCUs control the rudder.

The PCUs contain a hydraulic actuator, an electrohydraulic servo valve, and a position feedback transducer.

When commanded, the servo valve causes the hydraulic actuator to move the control surface. The position transducer sends a position feedback signal to the ACEs. The ACEs then stop the PCU command when the position feedback signal equals the commanded position.

OK, that's what I was worried about. The flight control motors are actually hydraulic servos.

I guess I'm stuck with trying to use the DC alternators. In that case, I have to get gearing or belts that will allow a windmill, which probably won't turn any faster than 1K to work with a DC alternator from the plane that probably needs at least 5K to deliver something close to rated output.

Or, they'll have to create their own windings and use the permanent magnets to create a low-RPM generator. It's been done, I've seen many instances on the web of people doing that.

If anyone has any ideas on how to create 1kW/day of power from a mostly in one-piece 777, I'm all ears!

I can't use the APU right now, as the plane is far from the site where the people are settled. At some point, when they have enough tools/manpower, they will try to move the APU out of the tail and over to the settlement. I don't know the fuel consumption of the APU, but there is roughly 1000G of jet fuel still on the plane.

The RAT might work, but it is the same situation as the DC alternator. It wants to spin at a high speed. If anyone knows the RPM the RAT needs to spin at, that would be helpful.

thanks!

None fitted, 400v 3phase

For the work your folks need to do to remove the APU and install it, transfer the remaining fuel you would have approx 15 hours of operation....:rolleyes:

1000G would be better used as cooking fuel

The RAT is connected to a hydraulic pump

TW

Damn, you're shooting down all my options!

It's starting to get complicated to remove the 28V AC alternator and the PSA in order to get DC power.

Can I assume the PSA delivers BOTH 28V DC and 115V AC for the PAX seats? Or, are there smaller inverters at each seat doing the 115V inverting?

If it needs not be a 777 and a punier aircraft will do as well: A Dash 8 would come with some systems You require. It has an extensive 28VDC circuit fed by a generator on each engine plus the APU.

Flight controls are driven partially by hydraulics and partially by bizeps power though...

http://www.smartcockpit.com/download...Electrical.pdf


What about using the APU as a standalone source?

No, it is a 777 that has crashed on an island without anything modern on it. They have to scavenge the plane to make their needs met.

The plane is about 2 miles from the settlement, so running cables to the APU is problematic. Moving the APU is possible, but according to someone else, there is only about 15hrs of operation on 1,000G of fuel. The APU appears to be quite expensive to run for power. It is overkill for their needs - maybe in their future.

The only way to go is:
a) Windmill
b) Steam

Since there are 28V AC alternators on the plane, along with the electronics to deliver both 28V DC and 115V AC and I think three 28V DC batteries, that seems to need to be the heart of the power generating system. Initially, they will use wind to turn the alternators, later they will shift to steam.

There is also a 11-speed mountain bike in the cargo hold. They will use the 10:1 gearing on the bike to convert the 500 RPM wind speed to 5,000 RPM the alternator wants to run well.

With long enough blades, there should be sufficient torque/power to drive things.

Other suggestions are welcome.

What about modifying the rat?

You can see it on here just inboard and to the rear of the stb wing, it is designed to provide power by a wind driven alternator in case of electrical failure


https://www.flickr.com/photos/krislhull/6199902004/

http://dc308.4shared.com/doc/mpLmoiw3/preview.html#2

https://youtube.com/watch?v=FfB2EP71hqY
.

The RAT is possible. I have to figure out what RPM it runs at. I believe it runs at a high RPM. They would have to remove the blades and put a different configuration on it as they will only experience 20 knot winds, not 200 knots.

From what I can read, it seems the RAT has one of these 28V AC alternators in it. Not totally sure.

I also don't know how complicated it is to remove the RAT. They don't have all the tools a regular aircraft mechanic might have.

The BA 777 crash removed it for them, see

PICTURES: BA Boeing 777 Heathrow crash evidence - 1/18/2008 - Flight Global

If there was an Aircraft Engineer going to a job on contract, his tool kits would be in the hold as that's how we take them from country to country.

BUGS........!

Just to put you out of your misery.

They is no such thing as a DC alternator.

You have AC alternators and DC generators.

You can get DC from an AC Alternator by putting the output through a rectifier to get DC.

And the other way round you can take the output of a DC generator and put it through a inverter to get AC.

Electric generator - Wikipedia, the free encyclopedia

How about using the FADEC emergency power generators? Typically very small with low output but probably enough for a few lamps. Designed to work at very low rpm as well, as low as 9% gas gen speed.

How about using the Tacho generators from the brake anti-skid system.
I can't remember what their output is but there are twelve available. One in each axle.

Or there are motors in the ventilation/cooling system fans, galley chillers, toilet system vacuum pumps and a dozen others.

Have a read of By the Rivers of Babylon. A crashed Concorde can be made to move again in fiction. Why not a B777?

Thanks for all of the suggestions. I have more research to do on some of your suggestions.

Right now, I have a windmill built out of the hard plastic from a luggage case that is mounted on a bike frame (recovered from the cargo hold). The bike gives me 10:1 ratio so that I can drive some motor/alternator to get power down to some electronics (PSU?) that can charge the three 28V DC batteries that are on a 777 (at least I know of 3).

The Tacho Generators look interesting, but I think they are primarily used for rotational feedback. Sure, they create a voltage, but I don't think they can produce much power. It's hard to say since I can't find the exact model used in a B777, but I think it is a dead-end. They do seem to have the right RPM (1K) for a windmill.

The FADEC alternators will produce about 300W per channel at approx 2300 rpm, so with the 2 alternators you will get about 1200W at about 28vac. Might be enough to charge the batts if rectified.

What are they going to do with the power? How about just using batteries? Aircraft batteries, Emergency light batteries (many installed), Flashlight batteries, Laptops, mobile phones, etc. If you insist on generation, you could always build a simple gear chain with wire. All you then need is a large disc...

PM

re: FADEC
Thanks for supplying the RPM and wattage of those alternators, I was missing that. They are well suited as windmill generators.

re: power requirements
Yes, all their high-tech gear needs charging. But, they will also use lights from the plane to illuminate their compound. Also to drive some small AC electrical tools (drill, saw?) they found in the cargo hold. Most importantly to keep their VHF hand-helds charged as radio communication is going to be a strategic asset when the battles begin...

With the greatest of respect i think the technical aspects of this are too much for any non 777 technical geek to take on and mistakes will be mercilessly trashed where anomalies like control actuator motors, DC alternators, AC generators, 1KW per day etc are confidently bandied about.

Have you any idea how long and hard you'd need to pedal even an optimised generator setup to charge an aircraft battery? Or how much fuel you'd need to drive a steam generator - let alone the engineering impossibility of building one - or the engine to drive it - from aircraft parts.


You need a vast amount of very specialised knowledge and information to pull off a story like that and with the greatest of respect you haven't got past year one on basic electrical/power/engineering theory yet, let alone the type specific stuff you'd need.