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Cut out taxying under power.

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Cut out taxying under power.

Old 28th Sep 2006, 13:53
  #41 (permalink)  
 
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No no no!

Just bring the runway to each stand in turn!
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Old 28th Sep 2006, 17:17
  #42 (permalink)  
 
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Originally Posted by cwatters View Post
...
Also, an electric car is far more efficient than a gasoline car...
The primary advantage of the electric car is regenerative braking, wherein the drive motor(s) become a generator to recharge the battery. This advantage is greatest of course in stop-and-go city driving.

On the highway either you have to stop fairly often to recharge, or else have a small engine to keep you charged enroute (i.e. hybrid), and so the advantage is less.

Somewhere there's a chart of cost of energy per million BTU (Petrol, coal, diesel fuel, natural gas, domestic electricity...) that should quickly point out the cheapest energy sources.
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Old 28th Sep 2006, 17:18
  #43 (permalink)  
 
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Talking of Zurich - I have operated through there a couple of times and they have a simple system - the board in front of the aeroplane gives you slot time and start up time in order that there not be a queue at the hold. Started on the time, taxied out - no queue but there were lots of aeroplanes departing and arriving.

So, the fault lies with the ground controllers - yes, they should take the blame, ineficient squanderers of the earth's resources - that's better, shift the blame from the drivers to the controllers
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Old 28th Sep 2006, 19:54
  #44 (permalink)  
 
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Originally Posted by Oktas8 View Post
cwatters - if you read the last couple of paragraphs on that very good website you quoted, you'll read that a That's why tugs are very much more efficient than aircraft engines when it comes to taxiing.
Yup but in a hybrid (turbine/electric) tug the turbine would be operated at max efficiency charging the battery. If you insist...a Diesel/Electric hybrid would also be reasonably efficient.
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Old 29th Sep 2006, 21:30
  #45 (permalink)  
 
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cwatters,
You're confusing the tug and the aircraft in this discussion....

In a tug, a small gas turbine might be a viable alternative in theory, especially since you're already on an airfield, so the fuel is available, and possibly maintenance expertise also.
In practice, diesel and gasoline tugs have been around for ages, so by the time you design the tug, and manufacture them in the relatively small quantities needed, all economic advantages are lost.
Also, if you think about it, trucks run long distances at steady speeds. If gas turbines were significantly better, they'd be more widespread.

The original point (this is for JediDude as well) was that jet engines (gas turbines) are hideously inefficient to drive a big vehicle (i.e., a jet aircraft) at very low speeds on the ground across an airport...... Not to mention that once you're standing still in a queue, your efficiency drops to 0% .... but you're still burning fuel, while a tug could turn off its engine for a few minutes.


The really infuriating thing about all this that in principle the idea makes some good sense......
Somebody mentioned burning 1.5 tons for a 60 minute sector (smaller aircraft, not a big airliner) and 100 to 200 kg taxying. On average, that's 10%!!
Engine and aircraft manufacturers spend billions to gain another 10% fuel efficiency.

When I first read the original news item, it took me only about five minutes to come up up with nearly all the objections listed here.
What DOES sound like part of an answer is far better flow control on the ground. It should not be beyond the wit of man to conceive a system whereby you start your engines, get pushed back, taxi to the runway entry, maybe wait one minute for the current incoming aircraft, line up and take off. Sitting in a queue with engines running means the flow management does not work.
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Old 29th Sep 2006, 22:13
  #46 (permalink)  
 
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Wait... stop the presses! We build new airports the parking ramps will be at a high point around the airport. The tug pushes the airplane to a point where the descending ramp leads to the runway. Gravity takes affect, the plane roles to the end of the runway. As he gets close the runway he starts the motors and takes the runway and away he goes. Timing is everything. One airplane at a time.

When the plane lands, have real gadual high speed turn offs which lead to the ramp back at parking and let gravity takes its course again. Infact the pilots can save even more fuel by shutting down the engines and coasting to a stop at the ramp entrance. The tug does the rest.

This carzy idea lends credence even if I'm not even from California.

What do you think?????
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Old 29th Sep 2006, 22:49
  #47 (permalink)  
 
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Hey - I got this terrific idea: WHEELED transport vehicles. I suspect steel wheels on iron rails would be most efficient. Very long articulated vehicles - perhaps separate cars coupled together to negotiate turns. You might be able to travel almost at jet speeds, if you take into account citycentre-to-citycentre transit times.

I wouldn't try to tunnel under large bodies of water, though - that would be really stupid.
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Old 29th Sep 2006, 23:09
  #48 (permalink)  
 
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Originally Posted by Out Of Trim View Post
And then the aircraft would have to start and warm-up their engines for a certain period of time before take-off; before applying possibly full power for take-off.
I've flown from some of the smaller regional airport where the push back, startup, taxi and then go were measured in minutes.

What is the warm up time generally? My experience is on small Cessna type things where once the power checks are done we're off!

Duncan
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Old 30th Sep 2006, 00:35
  #49 (permalink)  
 
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Originally Posted by barit1 View Post
Hey - I got this terrific idea: WHEELED transport vehicles. I suspect steel wheels on iron rails would be most efficient. Very long articulated vehicles - perhaps separate cars coupled together to negotiate turns. You might be able to travel almost at jet speeds, if you take into account citycentre-to-citycentre transit times.
barit1,
I see you're living in Ohio, USA... so you're forgiven.
When I have to get from the South of France, where I live, to Paris, I take the train. All of 3:15 hours centre to centre, about 900 km.
It only does Mach 0.25, but it doesn't waste time taxying around for half an hour at 15 mph, and I don't waste another hour with check-in, security and boarding. Not to mention getting from the airport to the city centre.
BTW, one of those trains did Mach 0.42 during trials. And yes, steel wheels on iron rails. For the moment the main problem is the catenaries.
I wouldn't try to tunnel under large bodies of water, though - that would be really stupid.
Too late, they already did.... but they do have some money problems...
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Old 30th Sep 2006, 05:07
  #50 (permalink)  
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I've got it!!!!!! Why didn't I think of it before?

Strong men...y'know, the ones with very strong teeth. A length of rope clenched between said knashers by a man in a loin-cloth and Bob's yer uncle.
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Old 1st Oct 2006, 02:25
  #51 (permalink)  
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The Navy has it sorted. For them, the stand is the runway.

'Striking down' an A380 poses some interesting civil engineering challenges though.

...and they'll have to beef up those nose gears a bit...
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Old 2nd Oct 2006, 17:09
  #52 (permalink)  
 
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Originally Posted by barit1 View Post
Is it time to restart the conveyor belt thread?
Yes, but not the same way! Land the A/C on the conveyor with the park brake set and store the resulting energy like a huge rubber band, problem is landings will be one way and takeoffs the other? At least landing a 747 at max weight might be able to sling shot a couple of A340's off the deck

The A380 could charge the airport for a landing fee a skillfully executed T&G and you'd have a days worth of A320 departures!
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Old 5th Oct 2006, 11:53
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Originally Posted by SMOC View Post
...

The A380 could charge the airport for a landing fee a skillfully executed T&G and you'd have a days worth of A320 departures!
Brilliant! And a downwind landing adds a few extra ergs as well!

(We can share the royalties, right?)
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Old 19th Oct 2006, 12:28
  #54 (permalink)  
 
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Just got this off Avweb. Carry less fuel? Yes Richard. Looks like the tow to the threshold thread may have given him an idea as well.

BRITS MAY REQUIRE CUTS IN AIRPLANE EMISSIONS
In Europe, where the threats of global warming and air pollution are taken much more seriously than in some other parts of the world, the contributions of aviation to rising carbon-dioxide levels are coming under scrutiny. The U.K. aims to cut its carbon emissions 60 percent by 2050, but a new report released this week says that can't happen without including aviation, which is not addressed under current schemes. About 5.5 percent of U.K. carbon emissions are from aircraft, but that percentage will rise to about 25 percent by 2050. Richard Branson, of Virgin Airlines, has said that airlines could cut their emissions by 25 percent right now by implementing new procedures, such as taxiing less and carrying less fuel.
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Old 3rd Dec 2006, 11:54
  #55 (permalink)  
 
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Virgin plan to save fuel

This from the BBC

Virgin Atlantic plan to save fuel

Sir Richard Branson has called on the industry to cut carbon output

Sir Richard Branson's Virgin Atlantic is to conduct a trial using 13 of its planes which could cut aviation fuel use and slash carbon dioxide emissions.
By towing its Boeing 747-400 aircraft to take-off areas at London airports during December it said it could save up to two tonnes of fuel per flight.

Aircraft will be towed to Heathrow and Gatwick runways to cut fuel burning.

Virgin said a reduction of 120,000 tonnes in carbon emissions a year could be made if extended across its fleet.

'Starting grids'

It is hoped to reduce the time engines are running before taking off to about 10 minutes.

"Towing aircraft from a stand substantially reduces the amount of time they need to taxi with their engines running and reduces the time spent queuing before take-off," said Virgin Atlantic spokesman Paul Charles.

Virgin Atlantic is working alongside airport operator BAA and National Air Traffic Services (Nats) during the trial, with a longer run-out expected in the first quarter of 2007.

Aircraft will be towed from their stand at the airport to so-called "starting grids" - which are holding areas, close to a runway, consisting of several parking bays for aircraft.

It means that aircraft can be towed closer to a runway before take-off.

Teams from Virgin Atlantic are also holding talks with the international airports in San Francisco and Los Angeles, as well as JF Kennedy airport in New York, about the timing of similar trials.

Greenhouse gases

Virgin Atlantic is half owned by Sir Richard Branson and the other half by Singapore Airlines. The other aircraft in the fleet are five Airbus A340-300, and 17 Airbus A340-600.

Airlines are in the spotlight over the amount of carbon emissions which the industry is producing following falling fares and the growth of low-cost operators..

Aircraft are one of the fastest-growing sources of greenhouse gases and environmentalists are calling on the government to take action to reduce their output of carbon.

Carbon dioxide emissions from aviation doubled during the 1990s while those from the rest of the economy fell. Currently, aircraft produce about 5.5% of UK emissions.

In September Sir Richard said that up to 25% of the world's aviation carbon dioxide emissions could be cut if airlines, airports and governments worked together.

He has also pledged Virgin Group profits worth $3bn (1.6bn) towards renewable energy initiatives.

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Old 3rd Dec 2006, 12:08
  #56 (permalink)  
 
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I'll be interested to hear what the ATC people from Heathrow think. Towing 747s to the holding area sounds like a clever idea, but how much fuel will be wasted by other aircraft which have to taxy more slowly, or are delayed leaving their gates, by slow-moving heavy jets? Could the the ground control problems at airports as congested as Heathrow outweigh the benefits?
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Old 3rd Dec 2006, 13:52
  #57 (permalink)  
 
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Gee, if he had bought 777's instead of stretch 340's he would have been already using less fuel and creating less emissions, but he wanted to support European jobs and now he has a less efficient fleet and all the teething problems he had. But he does have 4 engines 4 long haul. A poor decision from someone used to successful businesses.
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Old 3rd Dec 2006, 14:01
  #58 (permalink)  
 
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Surely this is no more than cheap publicity stunt!
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Old 3rd Dec 2006, 14:22
  #59 (permalink)  
 
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Originally Posted by punkalouver View Post
Gee, if he had bought 777's instead of stretch 340's he would have been already using less fuel and creating less emissions, but he wanted to support European jobs and now he has a less efficient fleet and all the teething problems he had. But he does have 4 engines 4 long haul. A poor decision from someone used to successful businesses.
Call me 'old fashioned', and it is some years since I crossed an expanse of water, but I shall be counting the number of engines before I do it again.

I don't care if they tow me to the holding point, take me there is a pax coach or indeed a chaffeur driven limo, but I shall be looking out on the wing, as we past vast expanse(s) of water, counting the engines.

Have never crossed a 'pond' with less than 3 engines and that ain't about to change
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Old 3rd Dec 2006, 14:24
  #60 (permalink)  
 
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ETOPS

Originally Posted by punkalouver View Post
Gee, if he had bought 777's instead of stretch 340's he would have been already using less fuel and creating less emissions, but he wanted to support European jobs and now he has a less efficient fleet and all the teething problems he had. But he does have 4 engines 4 long haul. A poor decision from someone used to successful businesses.
Mebbe he really believes in ETOPS: Engines Turn or People Swim...

GB
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