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New equipment hype

Discussion in 'General Equipment Chat & Advice' started by Bazarchie, May 26, 2020.

  1. ChrisNewman

    ChrisNewman Well-Known Member

    I looked up the fuel consumption of a 747, and read “Over the course of a 10-hour flight, it might burn 36,000 gallons (150,000 liters).” That’s about 12 tons an hour, which would create about 38 tons of CO2 per hour, about 1.9 million tons during a 50,000 hour extension of its working life. I’d be surprised if someone hasn’t looked into the relative environmental costs of such decisions; I know work in this area was going on for the building industry when I was still working at the Building Research Establishment. But I’m sure that a reasonable saving on 1.9 million tons of CO2 would dwarf the environmental costs of building a new plane. Wouldn’t a 100,000 hour 747 be given new engines for a further 50,000 hour stint anyway?

    I’d also be willing to bet a large sum that a virtual meeting would use far less energy than a drive to Cardiff, at least for someone starting outside Wales.

    Yes, there are costs to doing anything, but most electronic tasks use only a tiny fraction of the energy of manufacturing items or transporting people. It’s only because these electronic costs are so small that we make so much use of the possibilities, leading to a significant total energy consumption by the sector. And of course we should repair rather than replace in most cases, but sometimes it’s worth replacing old, inefficient machines with new, more efficient ones. We’d benefit from a lot more information in this area, but I suspect there’s a lot that’s already known, but is difficult to find. (Next to impossible without expending a little energy on an internet search!)

    I’m sure environmentally the cost of getting it wrong will exceed the cost of getting data for any key decisions about recycling, replacement, etc.


    Chris
     
  2. GeoffR

    GeoffR Well-Known Member

    From, distant, memory the fuel load for a 747-400 to BKK or SIN, about a 12 hour flight, would be about 150,000Kg and it would arrive with around 20,000Kg so more like 10 tons per hour but a huge amount would be burned in the first hour and then the rate per hour would diminish. Thus longer sectors would show a lower hourly fuel consumption. A 777-300 burns about 7.4 tons per hour so 25% less making the question how much CO2 to manufacture the 777? If it is less than 400,000 tons there may be a case for replacing the 747 with a 777.

    A little research suggests that an A350 will burn less than either the 747 or the 777 so replacing the 747-400 with an A350-1000 would certainly make sense.

    Civil aircraft rarely get a different engine during their service lives, though there is no good reason why that should be the case. The A320 series and the A330 have been offered with updated engine options so there is no physical reason why an older model should not be fitted with the newer engines. The certification cost may be prohibitive however. Designing aircraft with a standard engine interface would seem to be a reasonable expectation and doing so with the express intention that the airframe will be retrofitted with a more efficient engine at some point in its life would certainly make economic and environmental sense. Re-engining large aircraft isn't common, the Lockheed Galaxy is one example and the USAF has started the process of finding replacement engines for the Boeing B52, the still insist on having eight which makes no sense to me what so ever.

    Replacing a car that does 30MPG with one that does 33MPG doesn't make sense and the tendency for each new model to be bigger and heavier than its predecessor should be sufficient indication that buying a new car to save the environment is nonsense.
     
  3. ChrisNewman

    ChrisNewman Well-Known Member

    Do you mean they rarely get a different type of engine from that they were sold with, or that the engines they are sold with will last for the 200,000 hour design life of the plane? The latter seems quite an achievement! I seem to recall hearing that Rolls Royce make more from servicing their engines than supplying them for new planes (sounds like printers and ink!), but I assumed the engines would need to be replaced at intervals during the plane’s life.

    I’m not certain, but I rather think I saw an analysis recently suggesting that even an electric car would need to do well over 100,000 miles to recoup the environmental cost of scrapping a hydrocarbon-fuelled car and replacing it with electric. (The trade-offs would be so different if our cars were driven for the tens of millions of miles that airliners must cover in their working lives.)

    Chris
     
  4. GeoffR

    GeoffR Well-Known Member

    Yes aircraft very rarely get a different engine type, on any specific airframe.
    I do remember a Rolls Royce engine set a record for hours on wing but I can’t remember the hours it had run. Looking it up it was an RB211-535E4 and over 40,500 hours.
     
    Last edited: Jun 3, 2020
  5. Learning

    Learning Ethelred the Ill-Named

    I presume that a turbofan engine could be redesigned to use liquid hydrogen. I presume that liquid hydrogen could be generated intermittently while there was excess green electricity.
    How about green aviation using liquid hydrogen as fuel. The risk of extreme fire in the case of a crash might be greater than that of using kerosene but that would just increase the frisson of flying to that of the good old days.
     
  6. PeteRob

    PeteRob Well-Known Member

    Certainly you can burn it but you can’t carry enough of it. You can’t maintain hydrogen in a liquid state for any length of time without cooling. The whole issue with hydrogen as a fuel is energy density. You either use it as compressed gas or adsorbed on a carrier. Kerosene (Jet A1) is the optimum fuel for aviation powered by jet engines, aviation gasoline for piston engines.
     
  7. GeoffR

    GeoffR Well-Known Member

    I think the weight of insulation to stop the hydrogen reverting to a gas together with the weight of reinforcement to withstand the pressure might be detrimental to the payload and range.
     
  8. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    Didn't I read somewhere that they were looking into artificial diamond as a material for high pressure resistant components? One of the advantages quoted was that it was a great deal lighter than metal based containment.
     
  9. Chester AP

    Chester AP Well-Known Member

    I always look at the regular double page spread of images from an AP reader. Have you noticed that sometimes all the shots were taken with the same camera, possibly now a few years old, and sometimes 4 or 5 different relatively recent models were used? There are people out there who appear to regularly buy a new model, and I applaud their expenditure because it (hopefully) keeps real photographic retailers in business and feeds the secondhand market which has supplied most of my photography hardware. But I don't know if regularly 'upgrading' always improves their pictures.

    My first DSLR was a 10 mp APS-C (half frame) model that enabled me to get 50 x 75 cm prints that looked good as long as the image wan't cropped. I later upgraded to a 16 mp APS-C model because the sensor allowed much better results at higher ISO settings, but the increased resolution made less difference than I expected on a 50 x 75 cm print. I did have one 40 x 50 cm portrait-format print done from half of a landscape-format image (so image size about 8 mp) and the print is excellent. But I did use one of my best lenses for the shot.

    This 16 mp camera body is now 7 years old and unlikely to ever be replaced unless it falls apart.
     
    Bazarchie likes this.

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