Someone Somewhere wrote:
On 25/09/2019 16:03, Recliner wrote:
Someone Somewhere wrote:
On 25/09/2019 15:18, Roland Perry wrote:
In message , at 13:51:18 on Wed, 25 Sep
2019, tim... remarked:
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
vehiclesÂ* goingÂ* to and from the airport will really make up for the
extra emissionsÂ* from theÂ* aircraft using the new runway such as the
A380 which burns half a tonÂ* of fuelÂ* 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.

A typical fare for a flight like that is going to be £400 each way. If
they spend £1 of that taxiing to the end of the runway, we really do
need to find something more useful to discuss than spending 90p on an
electric tug instead.

Wasn't the argument less about the money, and more about the fact they
were introducing a congestion charge at LHR due to the locally high
pollution levels and one of the points was less aircraft running their
engines for less time equates to potentially a better local pollution
reduction strategy than a reasonable reduction in cars in the area could
achieve?

Quick back of an envelope calculation: If your car does 40MPG, then
that's about 10km per pound at 130p per litre, which is basically one
return car trip into the Heathrow environs per passenger. Once you take
into account that aviation fuel is tax free, then a better comparison is
oil price - £50/150 litres, or 33p/litre, so even taking into account
refining cost etc that's probably twice that distance

Given that not every passenger arrives individually in a taxi (the worse
possible scenario in terms of car miles per passenger in the area) then
removing that £1/pax in fuel saves burning more hydrocarbons locally
than would ever be feasible by removing all cars from the LHR area.

Of course, cars don't start their journeys on the perimeter (however
that is defined to be) but that's where the congestion charge is to be
enacted to reduce pollution...


The aircraft engines will still need to be started and warjed up some
minutes before take-off, so they'll still burn much of that fuel. The
powerful tugs needed to haul the aircraft will also consume fuel on their
journeys in both directions. I don't think there are any electric options
yet for that sort of powerful tug, so that means diesel. They will also
need drivers, and dedicated routes around the airport that don't get in the
way of planes. So it's not a clean option, and would almost certainly cost
more than the current system — which is why no airport does it.

And the discussion started as there aer electric tugs for shorthaul and
there may be larger ones for bigger jets.

Yes, possibly, but those pushback tugs are much less powerful, and need far
less battery capacity than the far heftier tugs that could tow aircraft at
normal taxi speeds (30-45 km/h) on non-level taxiways for distances of
several miles. I'm not even sure that such high towing speeds are allowed,
because of the stress on the nose landing gear.

The electric pushback tugs only move the aircraft very slowly for distances
of 100m or so, and then have a recharge, which is a vastly smaller task.


The other discussion was about an autonomous (or partly autonomous)
system. Being facetious I could point out there are the pods at
Heathrow already, so similar technology with a much beefier vehicle
could be plausible.

The pods run only on a guideway, with no conflicting traffic.


I accept it might need technologies and systems that don't exist, and a
network of routes for them to get around, but if you're engaged in
spending £15BN on a new runway and to get it accepted you need to reduce
pollution then that kind of thing can be a driver to actually consider
these sort of things rather than take the easy route (which strangely
actually raises revenue) of charging cars for access when you operate an
airport that passengers regularly arrive and depart from outside of
normal public transport hours.

So I accept it costs money, but it could be a clean option.

A lot more money, and only slightly cleaner.


What I'm not sure I accept is the length of time that aircraft engines
need to be running before takeoff - I imagine those things get pretty
hot pretty quickly.

Apparently it's 2-5 minutes, and then there are the checks on pressures,
etc. So it's perhaps 25-50% of the taxi time.

What may be an issue is where running the engines
sit in the pre-flight checklists but an electric tug with a big enough
battery could power some of the aircraft systems whilst it is being
towed (there are certainly ground based APUs for those aircraft without
one). Ok - I accept that charging such things may be a problem.


The tugs would need the power of a railway locomotive. Remind me, how many
battery powered locos are in service?