On Mon, Sep 23, 2019 at 04:45:38PM +0100, Someone Somewhere wrote:

But it seems obvious that the best solution would be some kind of
(presumably) electrical tug that could take a plane from the gate to the
point where it needs to switch to using its own engines for takeoff.

Given that the engines (I believe) turn the generators that provide
electrical power, that point is the point at which the plane is
disconnected from ground power. They need electricity to power the
radios that let them talk to the control tower, run air conditioning,
make announcements to passengers, and so on.

If you took the idea further then you could considerably optimise the
airport - planes would only need to be at gates for when passengers were
embarking/disembarking ...

You just introduced a lot of complex ground movements. And while that
might (might, not will) make more efficient use of the gates, it won't
make more efficient use of taxiways, runways, or aircraft.

--
David Cantrell | even more awesome than a panda-fur coat

Longum iter est per praecepta, breve et efficax per exempla.

In message , at 13:19:12
on Tue, 24 Sep 2019, David Cantrell remarked:
On Mon, Sep 23, 2019 at 04:45:38PM +0100, Someone Somewhere wrote:

But it seems obvious that the best solution would be some kind of
(presumably) electrical tug that could take a plane from the gate to the
point where it needs to switch to using its own engines for takeoff.

Given that the engines (I believe) turn the generators that provide
electrical power, that point is the point at which the plane is
disconnected from ground power. They need electricity to power the
radios that let them talk to the control tower, run air conditioning,
make announcements to passengers, and so on.

Which is why many aircraft had an engine (aka APU) in the tail to
provide that.

Failing that, batteries, like the much lamented lithium ones in
Dreamliners.
--
Roland Perry

On 23/09/2019 16:35, wrote:
On Mon, 23 Sep 2019 16:04:12 +0100
Recliner wrote:
On Mon, 23 Sep 2019 14:58:53 +0100, Basil Jet
aircraft using the new runway such as the A380 which burns half a ton of
fuel
just to get from the gate to take off position.


Isn't that what those yellow drones someone linked to last week are for?

They don't fly, so they're not drones.

They're robotugs called Mototok Spacer 8600s. They aren't powerful
enough to push back wide-bodied jets, though a larger model might. In
any case, they don't replace any jet fuel, as pushback would otherwise
be done by hefty diesel tugs. So they save some diesel fuel and fumes,
but not aviation fuel.

If you knew anything about physics you'd be aware that using a jet engine to
push a vehicle on the ground is far less efficient than using powered wheels.
Half of the energy is wasted on chucking air backwards rather than making the
aircraft go forwards.


ROTFL

--
Graeme Wall
This account not read.

On Tue, 24 Sep 2019 13:29:42 +0100, Roland Perry
wrote:

In message , at 13:19:12
on Tue, 24 Sep 2019, David Cantrell remarked:
On Mon, Sep 23, 2019 at 04:45:38PM +0100, Someone Somewhere wrote:

But it seems obvious that the best solution would be some kind of
(presumably) electrical tug that could take a plane from the gate to the
point where it needs to switch to using its own engines for takeoff.

Given that the engines (I believe) turn the generators that provide
electrical power, that point is the point at which the plane is
disconnected from ground power. They need electricity to power the
radios that let them talk to the control tower, run air conditioning,
make announcements to passengers, and so on.

Which is why many aircraft had an engine (aka APU) in the tail to
provide that.

Failing that, batteries, like the much lamented lithium ones in
Dreamliners.

Yes, airliners use the APU to power the lights, aircon, radios, etc
when they're on the ground without main engines running if there isn't
ground power. So even if the plane was towed to near the take-off
point by an electric tug, the APU would still have to run. The APU
also provides the power to start the main engines.

David Cantrell wrote:

On Mon, Sep 23, 2019 at 04:45:38PM +0100, Someone Somewhere wrote:

But it seems obvious that the best solution would be some kind of
(presumably) electrical tug that could take a plane from the gate to the
point where it needs to switch to using its own engines for takeoff.

Given that the engines (I believe) turn the generators that provide
electrical power, that point is the point at which the plane is
disconnected from ground power. They need electricity to power the
radios that let them talk to the control tower, run air conditioning,
make announcements to passengers, and so on.

Commercial aircraft have an APU (auxiliary power unit) that provides power for
the things you mentioned when ground power is not available and the main engines
are not running. These are small jet engines located in the rear of the
fuselage.

A few years ago there was a big industry focus on reducing ground use of jet
fuel. The two main areas looked at were self propelled sysems (i.e. adding
electric motors to the landing gear) and battery powered robotic tugs that would
bring the aircraft to the runway.

The problem with both approaches was economic. In the case of the electric drive
motor, the cost of the system, reduction in overall reliability of the aircraft,
and most importantly the cost of additional fuel required to carry the weight of
the motor in flight far offset any ground fuel use savings.

The robot tug had similar economic issues, as well as the operational issues
already mentioned in this thread.

"Recliner" wrote in message
...
https://www.thetimes.co.uk/article/heathrow-congestion-charge-is-expected-to-raise-1-2bn-a-year-wv9qn2c36?shareToken=2e1812617e77460e9d40ce4f851b4 ca3



yes that's right

charge all those people who live on the west side of the airport who have no
choice but to drive there because the airport has three times reneged on its
promise to build rail links in that direction

and I bet they reengage on the current promise too

FTAOD I am no longer an interested party here (having spent 35 years of my
working life waiting for the links to be built)

tim

wrote in message ...
On Mon, 23 Sep 2019 14:07:52 +0100
Roland Perry wrote:
In message , at 11:15:51 on Mon, 23 Sep
2019, remarked:
On Mon, 23 Sep 2019 10:37:29 -0000 (UTC)
Recliner wrote:
https://www.thetimes.co.uk/article/h...harge-is-expec
ted-to-r
aise-1-2bn-a-year-wv9qn2c36?shareToken=2e1812617e77460e9d40ce4f851b4 ca3

Ah, greenwash at its finest. I'm sure reducing the number of vehicles
going
to and from the airport will really make up for the extra emissions from
the
aircraft using the new runway such as the A380 which burns half a ton of
fuel
just to get from the gate to take off position.

If 300 of the passengers arrived by car, the extra congestion, let alone
emissions, would be noticeable.

I used to work near heathrow and the number of people travelling there by
private car was a small percentage of the total. I don't see why that
would
change with a 3rd runway. And my office overlooked one of the parking
pounds
of one of the private parking companies. Anyone who had seen what those
****wits
got up to with their prized possesion would never park at heathrow again.

There are so many BAD reports of what the cheaper end of the market (where
cheaper is still quite expensive) does with your car that I'm surprised
anybody uses them

but they do

tim

"Roland Perry" wrote in message
...
In message , at 15:32:33 on Mon, 23 Sep
2019, remarked:
On Mon, 23 Sep 2019 14:07:52 +0100
Roland Perry wrote:
In message , at 11:15:51 on Mon, 23 Sep
2019, remarked:
On Mon, 23 Sep 2019 10:37:29 -0000 (UTC)
Recliner wrote:
https://www.thetimes.co.uk/article/h...harge-is-expec
ted-to-r
aise-1-2bn-a-year-wv9qn2c36?shareToken=2e1812617e77460e9d40ce4f851b4 ca3

Ah, greenwash at its finest. I'm sure reducing the number of vehicles
going
to and from the airport will really make up for the extra emissions from
the
aircraft using the new runway such as the A380 which burns half a ton of
fuel
just to get from the gate to take off position.

If 300 of the passengers arrived by car, the extra congestion, let alone
emissions, would be noticeable.

I used to work near heathrow and the number of people travelling there by
private car was a small percentage of the total.

Total public transport (by passengers) has crept up to 40% over the last
decade (from 35%). Then there's the staff.

I suspect that a far larger percentage of staff travel by PT, as being
dropped off by a relative every day isn't exactly practical, and paying 20
quid a day to park is going to take a big chunk out of someone's NMW salary
(obviously not so for flight crew)

"MissRiaElaine" wrote in message
...
On 23/09/2019 16:32, wrote:

I used to work near heathrow and the number of people travelling there by
private car was a small percentage of the total. I don't see why that
would
change with a 3rd runway. And my office overlooked one of the parking
pounds
of one of the private parking companies. Anyone who had seen what those
****wits
got up to with their prized possesion would never park at heathrow again.

They should never have gone for a 3rd runway at Heathrow.

they still haven't

tim

"Recliner" wrote in message
...
On Mon, 23 Sep 2019 15:27:05 +0100, Roland Perry
wrote:

In message , at 15:06:09 on Mon, 23 Sep
2019, Someone Somewhere remarked:
On 23/09/2019 14:58, Basil Jet wrote:
On 23/09/2019 12:15, wrote:
On Mon, 23 Sep 2019 10:37:29 -0000 (UTC)
Recliner wrote:

https://www.thetimes.co.uk/article/h...-charge-is-exp
ected-to-r
aise-1-2bn-a-year-wv9qn2c36?shareToken=2e1812617e77460e9d40ce4f851b4 ca3


Ah, greenwash at its finest. I'm sure reducing the number of
vehicles going to and from the airport will really make up for the
extra emissions from the aircraft using the new runway such as the
A380 which burns half a ton of fuel just to get from the gate to
take off position.

What we really need here is fuel per passenger.

I believe the fuel costs about £1 per passenger.

from the airline mag [1] I was reading yesterday, it apparently costs
150,000 to fly a 767 round trip Europe-USA (didn't specify East or West
Coast)

No mention was made about how that cost was apportioned between operation
costs and capital costs.

tim

[1] As in the mag in the seat pocket on the aircraft, not one full of pretty
pictures (or whatever) that you buy in a newsagents.