Electrical output of airliners?

[mommus]

Hi everyone,

I'm looking for some info regarding the electrical output of long-haul airliners (787, 777, 767, 747, A330, A380).

I am working on an economy seat design concept that will allow much greater recline while maintaining a 33 inch pitch, but I am unsure how to attack the mechanicals.

I know business and first seats have multiple electric motors but are unsure whether sufficient electrical power is available for hundreds of economy seats - even those designed to use low amounts of power.

I had been looking at bleed air pneumatics also, but this requires a separate compressor on a 787 as they have bleedless engines.

I'm also considering a user-powered system of levers and springs, but electric would be easier.

I've approached Boeing and Airbus who don't seem to want to help unless I have a name within each organisation. Technical spec sheets don't seem to list cabin electrical availability either.

any help appreciated

[HDRW]

I am working on an economy seat design concept that will allow much greater recline while maintaining a 33 inch pitch, but I am unsure how to attack the mechanicals.

I wish you wouldn't!

I am *always* sat behind someone who reclines their seat fully at TOC and only uprights it again when the crew tell them to on descent (and not always then...). It makes it really hard to read/eat/watch the screen/get in an out to visit the loo.

If you allow them to recline further, I'll be trapped with my chin on the seat in front for the whole flight!

If you want to improve comfort in cattle class, finding a way to increase the spacing would be good...

[mommus]

HDRW - thanks for the reply

I'm glad you wrote that, because my design is aimed at preventing exactly the problem you describe.

As a passenger, you have a constant space that remains the same irrespective of the actions of the passenger in front of you, in fact, you will not be able to tell whether the seat in front is reclined or not.

[Spanner Turner]

747-400 has 4 engine driven generators of approx 90KVA = 360KVA

A380 has 4 engine driven generators of approx 150KVA = 600KVA

767 has 2 engine driven generators of approx 90KVA = 180KVA

Each aircraft can have 1 generator unserviceable under MEL so design elec output is vaguely based upon;

747-400, 3 x 90 = 270KVA
A380, 3 x 150 = 450KVA
767, 1 x 90 = 90KVA

All aircraft have a "load shedding" or priority system for elec usage.
I.E you can have lots and lots of power hungry seats, IFE, galleys, showers, internet, hairdryers, elec window shades etc, etc, etc, etc.
However, critical systems will always take priority over this crap when limited elec supply is available (I.E MEL of an generator) or during critical
flight phases. Examples are config changes such as flaps moving or gear in transit when elec hydraulic pumps come on, fuel jettison when lots of
heavy duty fuel pumps start up or engine failure when a generator is lost.

As you can imagine, these scenarios are basically take-off and landing when no-one is moving their seat, having a shower etc. All these nice to
have things are used during cruise and are a random demand not all used at the same time. So there is a "relative" abundance of power available
for your new design seat. Don't forget that all 'elec' seats must have designed in, manual overides to return the seat to the TTOL (Taxi,TakeOff,Landing)
position in case of elec supply not available.

Good Luck

:ok:

[Ian W]

HDRW - thanks for the reply

I'm glad you wrote that, because my design is aimed at preventing exactly the problem you describe.

As a passenger, you have a constant space that remains the same irrespective of the actions of the passenger in front of you, in fact, you will not be able to tell whether the seat in front is reclined or not.

The current business class seats in larger airlines recline by sliding the seat squab forward rather than the seat back backward. However, this means that as the squab moves forward the pax legs need to go somewhere. So in business class they usually stagger the seats with a table space between them where the legs of the pax behind can extend into this maintains pax density or they align the seats in a 'herringbone' which reduces pax density.

I cannot see how you can retain coach class passenger seating 'density', allow them to store carry-on bags 'under the seat in front' and allow a sliding recline. If you could do that the manufacturers Boeing and Airbus and the airlines would be beating a path to your door.

[mommus]

Ian W - thank you for the info

I can't really go into the exact method by which I have configured the seating, but at present (prior to any extensive real-world prototyping) I think I have a way to satisfy all the requirements you describe - with the possible exception of being able to place a carry-on size bag beneath the seat in front. However, I don't think you can do that with current designs - especially of you are sitting in the centre-seat/s of three or four seat blocks.

You can get a decent size backpack etc under there (if you don't wish to recline fully) but not a standard international carry-on bag. I thought these were meant to go in the overhead bins?

It's good news that there is available power onboard most planes. I had read up on the electrical output of various engine types but had no idea how the power was used by onboard systems.

Coincidentally, I was reading about load-shedding recently - but with respect to the Apollo guidance computer, which I believe was one of the first vehicle systems to use it.

thanks again

[spannersatcx]

CX have (mechanically) reclining seats in economy where the seat back (shell) doesn't move but the seat still reclines. If you fly on one of our a/c you will be able to see it in action.

[flarepilot]

be careful with your designs and consider not using electric motors to move the chair

so many problems that you may not have thought of including how to move chair in electrical problem, crash landing and loss of power, interference with pacemakers (ac motors), added weight and maintenance requirements.

you simply can't put 10 pounds of SUGAR (yeah right) in a 7 pound sack.

our airline installed a great idea in airline seats and within days the shortcomings of LINE ops made us remove the seats and replace them with the old ones...we lost money on that deal.

[cockney steve]

" economy" and "electric ajustment" are contradictory.

A self-contained ,mechanically -ajustable seat can be quickly removed or reconfigured, without the associated extra wiring-harness.


Consider worm/quadrant, Acme thread/split-nut , rack and pawl as three mechanisms that lend themselves to a rapid disengagement/reset as well as a slower,more progressive movement..

just my take on it, but the most important thing about a seat iscomfort
get that right and the range of fancy gimmicks ,hence the price, complexity and certification/maintenance costs can be reduced.

You cannot magic up space from nowhere . if it doesn't come from the space behind, it has to come from the "spare" space allocated to the seat's own occupant....that, in turn, creates a problem of access/egress for the pax between the seat in question and an obstruction (cabin-side of ajacent pax.)

[Terry Dactil]

I reckon it would be a great idea if the top of the seat back remained fixed and reclining was achieved by moving the bottom of the seat back forward.
This way anyone reclining their seat would stuff themselves into the seat in front and not upset the person behind. :E

[mommus]

Terry - What annoys you more?

- Not being able to recline enough to sleep?
- Having the seat in front recline into your lap?

[Ngineer]

747-400 has 4 engine driven generators of approx 90KVA

Pretty sure the IDG's are rated at 60KVA. The APU gen's are rated at 90KVA (different cooling).

[Ian W]

Terry - What annoys you more?

- Not being able to recline enough to sleep?
- Having the seat in front recline into your lap?

Third option - Having the seat in front recline into your lap then its occupant lean _forward_ and go to sleep :ugh:

[mommus]

I think I'd be tempted to have a word if someone did that!

[Spanner Turner]

Pretty sure the IDG's are rated at 60KVA. The APU gen's are rated at 90KVA (different cooling).


I'm pretty sure you could be talking about the generators fitted to the 'classic' 747's whereby the generator was the same Part Num as the ones fitted to the APU yet on the main engine were driven by a seperate CSD (constant speed drive). Yes, there was less cooling air available in the cramped quarters under the engine cowls and output was approx 60KvA in this installation. APU had a dedicated cooling fan driven off gearbox to cool the gennies fitted up the back end.

Figures in post above are for the 747-400 with IDG'S fitted (CSD and generator all in one with dedicated oil cooling system). Same item is fitted to 767'S. Below is from the Maintenance Manual.


An integrated drive generator (IDG) is mounted on the aft face of the accessory gearbox at the 7 o’clock position. The IDG consists of a constant speed drive and a generator mounted side by side in a common housing. Other parts integral or mounted to the IDG are the scavenge filter, thermal relief valve, and pressure relief valve. The IDG converts the varing input speed of the engine into 115/200volt, 3-phase, 90 KVA, 400 ±5 Hz power. The IDG weighs approximately 120 pounds (54 kilograms).

:ok:
.

[NWSRG]

Mommus,

The electrical load of your idea might not be that big a deal...if you factor in diversity.

For example, on a 250 seat 787, how many people will be operating their seat motors simultaneously? Probably guess no more than around 20 or so. So you only need to allow capacity for 20 rather than 250...throw in some wriggle room, and you might say 30.

I'd be more concerned at the combined weight of all those motors and associated wiring...

[VinRouge]

Ref diversity, I wouldn't want to bet on what the load would be when the flight attendant tells the cabin to return seats to the upright position...

Lots of electrics equals extra unnecessary fire risk in my mind.

[NWSRG]

VinRouge,

Good point...so we might need to add in some electronics to stagger any mass seat movements...or we let the cabin crew control that element in groups. "Passengers in row 25 will now be returned to the upright position!"...:E

[mommus]

I don't think it will be hard to write some load-managing software that either denies certain users control of their seats or simply reduces the movement speed at times of high load.

At the moment I am working with a design that uses only one compact electric motor per seat. I am unaware of any case where an electric motor on a business or first class seat has caught fire.

[tdracer]

Spanner Turner is correct - 747-400 has 4 x 90 KVA IDGs.

747-8 uses the same IDGs as the -400, but they are rated 96 KVA each for the -8 installation.
Most 767 are 2 x 90 KVA, although the Japanese AWACs 767s were 4 x 150 KVA (two per engine)
777 is 2 x 120 KVA, plus 2 x VSCF at (I think) 20 KVA
787 has 4 x 150 KVA (two per engine).

[mommus]

I think recline is critical if you want to sleep

here's the recline angle my design is aiming to achieve within a 33 inch pitch

http://i39.tinypic.com/1z5ofnd.jpg

[mommus]

it sounds then like available electrical power will be less of an issue with 4-engined aircraft, since twinjets carry more than half the passengers.

[Phalanger]

There is already a business class seat that moves almost in the same way (however goes further in some ways). I've tried everything to miss them because I don't like it, sliding down them is not nice, however for economy it would be an improvement. Maybe don't make the middle part move too sloped.

Also you could use something that causes resistance instead of a motor if I'm thinking on the same lines.

[bcgallacher]

Any maintenance engineer that had to work with electrically actuated seats regards them as a device of the devil - most types I have worked with have been grossly under engineered.

[mommus]

bcgallacher - thanks for the info, can I PM you to ask you a few questions?

Phalanger - yeah I've seen a business class seat that is technically flat but not horizontal. the passenger is kind of tilted like they're undergoing a sea burial.

I've tried to keep the passenger's thighs horizontal or slightly raised to stop them sliding down.

[CallmeJB]

msbbaratt

I've flown with CX, and I'm afraid to say they're http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gifhttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gifhttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/censored.gif awful. Long haul London to Heathrow was pretty intolerable. All things considered I'd far rather have a seat that reclines. I've been avoiding CX ever since at all costs.

London all the way to Heathrow? Yep, intolerable.

[Altcrznav]

HDRW - thanks for the reply

I'm glad you wrote that, because my design is aimed at preventing exactly the problem you describe.

As a passenger, you have a constant space that remains the same irrespective of the actions of the passenger in front of you, in fact, you will not be able to tell whether the seat in front is reclined or not.

There is no such magic.

Be gone charlatan!

[mommus]

There is no such magic.

Be gone charlatan!

I guess you'll just have to wait and see if you're proven right.

[bcgallacher]

Mommus - PM me if you wish

[TURIN]

787 has 4 x 150 KVA (two per engine).

Correction: 4 x 250KvA (two per engine) plus two on the APU. :ok:

[Uplinker]

Good luck Mommus, the world needs innovation. Don't be put off by the idiots on here.

I recently flew as pax on some seats which reclined to near horizontal, and did so by moving the seat squab forward, and a foot rest upwards. These were very comfortable and one could actually sleep rather than cat-nap/doze.

However, there were only 18 such seats in an area that can fit 51 normal business seats. If such fully reclining seats were fitted any closer to each other, outboard occupants would not be able to get past the inboard occupants to the aisles if the latter's seat was in full recline? As it was, one had to carefully step over the other persons legs.

[mommus]

Uplinker - thanks for the feedback. In terms of being able to get past people from a window seat (or similar) I have had to accept that you'll need to ask the people beside you to unrecline their seats and get up. With the density of seating required for 33 inch seat pitch, there really is no way around that.

I've found that even on United Economy Plus you still need to ask people to move if you want to get out, and you spend far more time in your seat that you do getting in and out of it, so I figure that is one of the insurmountable issues with economy class.

I'm just about to start buying components for a prototype, so fingers crossed it will work as a concept.

[NSEU]

I'm intrigued by the single motor concept. Most designers seem to have gone for multiple motors. Is this only for independent control over various chair elements or might it also be that wiring and multiple (micro) motors are lighter than heavy connecting mechanical mechanisms?

That aside, wouldn't the key to comfort be the relative position between the feet and the body (heart)? Some designers have even put seat pocket-like pouches in the seat in front in which you can put your feet (to raise the height of your feet). As a plus six-footer, I've tried various methods to get comfortable in Economy, including putting my feet on the seat (bum) cushion and wrapping a suitcase type strap around my legs to stop my feet slipping off.

From a Line Maintenance perspective:

Accessibililty to motors, microprocessors and the like is a key issue for us. Why do manufacturers force engineers to pull apart the entire seat, just to access the important stuff? Instead of simple hinged panels with one or two dzus fasteners, we get RSI removing dozens of long phillips screws (or having to get out our spanners and socket wrenches). Also note that getting under the seat for access to electrics, often involves sliding our bodies between two rows of seats with our legs in the aisles (which, during turnarounds, are routinely kicked, tripped over or bashed with carts and vacuum cleaners). It's bad enough in Business and First where the pitch is larger. Lifting a seat cushion and going in from the top is much easier.

In the race for lighter construction (to compensate for the weight of electrics), the chair often ends up either being made of exotic, expensive materials, or razor sharp sheet metal which cuts your hands to shreds when you try to work on the chair. The flimsiness of armrests often results in the liberation of arm padding and end caps. By the way, if you do make moveable armrests, please ensure that there is room in the hinge channel to feed seat recline & IFE controller wiring AND the connector plugs.

Whatever you do, please try make the armrests hinged, so you can at least, if the flight is relatively empty, stretch out over 3 or 4 seats.

I can so understand why one commentator's airline removed the electric seats. Electric seats have been around for decades and they still aren't getting any more reliable. It's gotten so bad, our airline has had to form dedicated teams to work on the seats. That is really not good for the airline's bottom line. imho, motorised Economy seats are just going to magnify this problem.

[mommus]

NSEU - thanks for the reply. There's some very interesting and helpful stuff there.

With respect to the number of motors and complexity - I only propose to use one motor per seat, so if you want to recline, you will also have to accept the leg cushion coming out too (and another important dynamic change that I can't mention at present). This might seem stingy, but it allows the mechanism to be infinitely more simple and the whole structure to be lighter.

I believe the great increase in comfort over standard economy seats will offset the limited control over body position (in comparison to a business type seat)

With respect to access for maintenance - I had considered using a quick-release subframe carrying the motor and main mechanicals that can just be swapped out with another, but that would increase the weight quite a bit, and also be cumbersome, especially servicing a window seat on a 3 abreast layout.

Access to the motor and associated parts would be by removing the seat bottom, as you suggest. Since the lifejacket is contained within the leg rest/foot rest this is easier to achieve.