Good question: "How much fuel does an PTV cost?"
OK, let's do some VERY simplified math in order to get a very, very roughed idea how many fuel is spent for inflight entertainment.
Let's assume (please don't flame - just guesses, no hard numbers!) we have
- a widebody a/c with e.g. 350 seats.
- a PTV control box per seat and a video screen, control pad and complete cabling with 2kg per seat.
- a central PTV control rack server let's assume some 15 kg.
- around 20 screens less in the overhead bins as you can find them in a/c without PTV, lets assume -30 kg altogether.
- average flight duration 5 hours for our a/c with 1/2 hour of descent and landing
- average three such flights per day.
OK: Net weight of PTV is then: (350x2)+15-30 = 685kg. Let's say around 700kg total for simplification.
Some more assumptions for further simplification:
- say we skip the fuel needed for the electricity powering the PTV system
- say the average climb rate of our a/c during starts and climb would be 20m/s (lifting in y-direction).
- say the normal cruising speed the PTV has to be accelerated from the start would be 850 km/h (acceleration in x-direction).
- say our avg. climb duration to the assigned
FL would be eight minutes from takeoff (8min. = 480sec. with 20m/s makes 9600m height or somewhere around FL25..FL28)
- say less ECS-heating of the cabin due to heat of the PTV's is also not mentioned.
To lift our 700kg PTV system from the surface up to the 9600m you would need around 137 kW additional thrust in each climb phase for our PTV only four our eight minutes of climb per start.
To accelerate our PTV and keep it flying with 850 km/h (around 236 m/sec) horizontally you would need a thrust of around 82,6 kW sustained for start, climb and cruise phases of the flight.
Given our flight schedule with three such flights a day 5 hours each with 8 min. climb each we would get to accommodate our PTV:
24 minutes of 220 kW additional power for starts/climb.
786 minutes of 82,6 kW additional power for the flights.
Every day.
For a lifespan of let's say ten years for the PTV with 340 days/year operation of the a/c this sums up to
81600 minutes or
more than two days (!) of 220 kW additional power for starts/climb.
2672400 minutes or
more than sixty months (!) of 82,6 kW additional power for the flights.
I would say that's a LOT of fuel! To get an idea:
http://www.tribnet.com/business/story/4979363p-4907348c.html
citing:
"Alaska Airlines considered reducing the number of magazines it routinely carries on short-range flights, but it hasn't done so yet. Eliminating five magazines from each of the company's 108 aircraft would save about $10,000 a year in fuel expense, the company estimates."
Let's assume one magazine has a weight of 200 grams. Then five of them would be 1kg. And we're talking about estimated 700kg fleet-wide.
What's $10000 * 700?
A lot of money.
Every year.
And increasing with Jet A-1 fuel prices.
Perhaps "no frills" or "no-IFE's" or "no-PTVs" airlines are not too nice for a certain segment of passengers.
But not having them is VERY nice to the operating cost (fuel) of the fleet.
Best Regards,
Kojak
P.S.: Perhaps some geek out there is able to translate the numbers found to gallons or kg/h fuel burn.
When playing cat and mice it's imperative to know, who's the cat.