nooblar questions

“one other question, planes have de-icing systems that work in flight”

The aircraft has an ANTI icing system that is designied to prevent ice from forming on on the leading edges. If it is left off and ice does start to form switching it on will de ice the leading edges, the airflow will remove the ice from the rest of the wing.

“these don’t work on the ground because they rely on hot air from the engines”

Yes but it will only remove the ice from the leading edge any way. Also you can operated it on the ground for a short time to test it.

“BUT the 787 is going to have an all-electric de-icing system”

Yes but to be picky there is going to be a small bleed off the engines to anti ice the engine nose cowls.

“the APU probably isn’t powerful enough to run this, but perhaps they could ‘plug-in’ the aircraft at the gate? Any chance of this happening”

As above only the leading edges will be di iced any way.

Electric motors in the wheels. I think Boeing are working on that.

Covered ramp areas. The ramp is a cold, wet, dark and miserable place to work some times. I wouldn’t have it any other way!!!!
Also if the ramp was covered, how would you guys get any pictures?!!!!

Rgds Cking

A340-300 fuel burn increases by 15% with one engine inop. A340-600 fuel burn increases by 9%.

thanks for the info

one other question, planes have de-icing systems that work in flight

these don’t work on the ground because they rely on hot air from the engines

BUT the 787 is going to have an all-electric de-icing system

the APU probably isn’t powerful enough to run this, but perhaps they could ‘plug-in’ the aircraft at the gate? Any chance of this happening?

…also i have seen several other comments that basically say if you can get a plane with x engines to fly on x-1 engines it is always more fuel efficient…

A340-300 fuel burn increases by 15% with one engine inop. A340-600 fuel burn increases by 9%.

Also, re item number 1 – weight measuring devices are very prone to temperature errors. The coldest I have ever seen in the cruise is -78 centigrade. If the aircraft had to do a quick turn around after 15 hours cruising at those temps sny measuring devices would struggle to be accurate bearing in mind they would also have to be accurate if that same aircraft had been left on a baking hot ramp at +55 centigrade.

Referance weight and balence, each airframe has it’s own ‘APS’ – which is derived from an actual weighing of the airframe.

For passengers there are serveral variations of weights, Male Pax, Female Pax and Children (Infants weight nothing apparently!). For these my company (as with most others) derives this into Scheduled Pax (M,F,C) or Charter Pax (M,F,C) each have differant standard weights. Taken into consideration are hand baggage etc into these figures. These are the only figures which I can see being actually slightly variable, and the cost implications of fitting however many hundred weighing stations at say LHR would be horrendiously expensive.

Baggage, Cargo and Freight (including the bins) are all weighed before onload, and as such there would be very little discrepancy here.

Fuel, Catering, Onbaord Sales eqpt etc is also added on as a unit weight to the loadsheet so to be fair, I think as said above there is no real requirement, and certainly no financial gain from having airframes weighed prior to departure.

Welcome to the forums!

thank!

i can’t say anything about the weight and complexity but i can address a couple of points:

The motors would need to be coupled to the wheels somehow, possibly by some kind of ‘gearbox’

i was thinking direct drive with no gears like some electric cars

I’m assuming your plan was that the aircraft would actually fire up its engines when near or on the runway? If the aircraft is on a taxiway or on the runway when they start the engines and a fault occurrs, there may be a delay to other aircraft using the airport.

i hadn’t heard of what adamdowley mentioned, but i got the idea from an airline or airport that was recently wanting a tug to pull the aircraft out to the runway and then have them light their engines there. Some environmental or fuel efficience measure. Anyways i assumed (maybe a bad idea 😉 that they had considered such problems and thought them not important enough.

Pilots are very accurate at predicting weights without scales as they know how much everything weighs and hence will put as many people on as possible that calculations permit.

my impression was that they had no idea how much the passengers and maybe their luggage weighed, so the calculations are based on very conservative estimates (safety first and all)

I imagine drag would be a huge issue with this idea.

well i looked to the israeli strike on iraq. to get the max range out of their F-15s they shut down 1 engine for most of the flight.

also i have seen several other comments that basically say if you can get a plane with x engines to fly on x-1 engines it is always more fuel efficient

but there are a few problems
1. it might be more fuel efficient, but it would also be slower
2. the remaining engines would be run harder, probably shortening life span and stuff

which is probably why you don’t see 747s running around on 3 engines even when they could

An awning wouldn’t stop icing of the aircraft as ice would still form by condensation in the air (think of frost on cars)

interesting, did not realize that

I’d imagine the biggest problem would be that on a 4 engined aircraft where only two are actually used on takeoff

sorry for not being clear, i meant for all 4 to be used for takeoff and then 1 to be shut down for cruise

so if the ‘climbing’ engine was 10% more efficient during takeoff, overall efficiency would be improved by 10/4 = 2.5% during takeoff

A variation on that idea is actually close to reality, and trials have been carried out on an Air Canada 767. Its called the Wheeltug and currently is an electric motor sitting on the nosegear. It is powered by the APU, and the production version is to be mounted in the wheel hub. It can take the aircraft to the runway without its main engines being on.

Check out the latest edition of Airports of the World to see more.

Welcome to the forum irtusk!

Ah, maybe it is possible then! 🙂

Paul

2. Powered wheels

Putting an electric motor in each wheel that is powered by the APU would save much fuel while taxing and maybe less ground crew for stuff like backing up without thrust reversers and shouldn’t weigh that much more

A variation on that idea is actually close to reality, and trials have been carried out on an Air Canada 767. Its called the Wheeltug and currently is an electric motor sitting on the nosegear. It is powered by the APU, and the production version is to be mounted in the wheel hub. It can take the aircraft to the runway without its main engines being on.

Check out the latest edition of Airports of the World to see more.

Welcome to the forum irtusk!

I imagine drag would be a huge issue with this idea. If it was feasable i would imagine it would already be in service.

As I understand it drag isn’t a that much of a huge problem for an inactive engine because it windmills and the air pretty much passes straight through it, so it isn’t as though you’re trying to force a solid disc through the air at 300 knots. There have been a good few occasions when a four engined aircraft has transported a fifth engine attached to the wing with very little or no drag/performance problems.

I’d imagine the biggest problem would be that on a 4 engined aircraft where only two are actually used on takeoff, those engines would need to be enormous (and heavy) compared to those used on a standard aircraft (imagine a 747 or A340 with four RR Trent 800’s!). You’d also loose the redundancy aspect of having the ability to fly on three engines if you have a problem with one.

Paul

Hello and welcome also!

1. I would say it sounds good but my opinion would be that the flight crew need an estimate of weight before loading of the aircraft so they can calculate and order fuel quantities and therefore would create too much much of a delay if they still had to order fuel once the pax/cargo were seated/loaded?

2. Initially I thought it wouldn’t be possible due to the huge inertia the motors would have to overcome and hence the torque they must be able to supply. Then thinking again I thought of the videos of strongmen and the VW pulling (granted empty) 747s. Maybe if the engines were spooled up to overcome the initial inertia, then returned to idle and wheel motors used after?

3. Again an interesting idea. I would imagine though that it would recquire a larger more complex control system. Also any 2 different engines on an airframe will have different efficiencies as all varients are designed for different optimum conditions. I’m not sure that the loss in efficienty over long rutes would be overcome by using a different engine for climb/cruise.

4. An awning wouldn’t stop icing of the aircraft as ice would still form by condensation in the air (think of frost on cars). You would also have to make sure the cover (cantilever and/or suspension cables if there were to be no ground support) would be able to fully withstand the strongest weather condition to prevent collapse on aircraft/ground crew.

Interesting post, thanks. I wasn’t disregarding any of your suggestions, just thinking of some cons – some of which may be wrong, im not expert (yet :p )

Symon

1. Direct measurement of weight

Putting a scale directly into the landing gear (new planes) or by the gate (works with all planes) would eliminate a lot of hassles with estimating passenger and cargo weight. No longer will passengers be bumped because the plane MIGHT be overweight. And no longer will a plane take off dangerously overloaded because the estimations failed.

Pilots are very accurate at predicting weights without scales as they know how much everything weighs and hence will put as many people on as possible that calculations permit.

2. Powered wheels

Putting an electric motor in each wheel that is powered by the APU would save much fuel while taxing and maybe less ground crew for stuff like backing up without thrust reversers and shouldn’t weigh that much more

Agree with PMN

3. Mixed engines

I see people say that engine A is better for takeoffs and climbing while engine B is more efficient for cruising. On for instance a 4 engine jet would there ever be a circumstance where it would make sense to mix A and B? Say have 1 ‘climbing’ engine and 3 ‘cruising’ engines?

Presumably the ‘climbing’ engine would have to be throttled back or shut down during cruise to see any gain.

I really doubt this could be retrofitted to existing aircraft as I imagine there are too many dependencies on the assumption that all the engines are the same. But a new plane designed with this in mind . . .

I imagine drag would be a huge issue with this idea. If it was feasable i would imagine it would already be in service.

4. Covered gates

something like an awning but obviously with no support poles sticking in the ground (would have to be totally supported from the terminal side)

It seems a lot of time and money is wasted with deicing that could be avoided if the plane was protected while sitting at the gate

Also i heard groundcrews can’t work when there is lightning in the area and this would allow them to continue without delay

Are there any issues with extra lighting expense or possible fume accumulation (even though it is open all around)?

I cant see a structure which can only be attached at one end spaning out to cover the likes of an A380 or B747. The costs of bringing this in would be astronomical given that such storms are not an everyday occurance. Maybe if they were happening once a week or more it would be a good idea?

Hi Irtusk. Welcome to the forums!

I can certainly see the logic in some of your points, but on the subject of powered wheels I can think of a couple of reasons, technical and non-technical, why it wouldn’t be practical (although there are a few pilots and people doing their CPL on here who may be able to correct me on anything I get wrong!)

The first thing that springs to mind is actually weight. Electric motors are very solid, heavy devices, and I would imagine the size of motor you would need to move a large widebody aircraft (or even a 737/A320 for that matter) would’t be small. I’d also imagine they would require more space in the wheel wells. Those motors would also require quite a lot of power. I work in music and motors we use for flying PA systems and lighting rigs arn’t the biggest, but they generally require a minimum of a 16 amp three phase supply at 240 volts, so larger, more powerful motors could require a huge amount of electricity to run. That elecricity would need to be generated by a fairly hefty and also very heavy alternator attached to the APU, adding even more weight. Also there isn’t just the weight of the motors and additional alternator to consider. If, for example, they need a 63 amp three phase power supply and a 747/A340 has two or maybe even four motors, that would possibly mean several hundred metres of cable are required running towards the rear of the aircraft and believe me, 63 amp 3 phase cable is EXTREMELY heavy (I’ve coiled far too much of that stuff!) That amount of cable would almost certainly weigh even more than the devices themselves. I’d also imagine all that additional weight towards the rear would play havoc with the trip of the aircraft, although my knowledge in that department is slightly lacking so I’m sure someone can correct me if that assumption is wrong. In any case, it would certainly burn more fuel!

Secondly, it makes the aircraft more complex and gives something else that could possibly go wrong. The motors would need to be coupled to the wheels somehow, possibly by some kind of ‘gearbox’, again adding weight and complexity. I’m assuming your plan was that the aircraft would actually fire up its engines when near or on the runway? If the aircraft is on a taxiway or on the runway when they start the engines and a fault occurrs, there may be a delay to other aircraft using the airport. Not good at somewhere like LHR where there are aircraft coming in and departing at a rate of pretty much one every 90 seconds or so!

I’m sure someone else can give a fairly in depth and technical reason on your mixing engines idea… That’s enough typing and thinking for me for the moment!

Again… Welcome! 🙂

Paul