5 ms·

You're not taking into account the vastly simpler design of an electric aircraft. An electrically propelled aircraft will have maintenance requirements similar

by leoedin 13y ago

You're not taking into account the vastly simpler design of an electric aircraft. An electrically propelled aircraft will have maintenance requirements similar to a glider. Fewer engine overhauls and much simpler procedures means significantly reduced cost.

sokoloff 13y ago
I don't think you're taking into account the vastly increased battery maintenance, inspection and capacity testing that will be required. Yes, you'll save a lot on not maintaining a piston IC engine. You'll give some of that back in inspection processes to ensure that you don't have 95% of the range that you think you have. If you run of out power in a Leaf or a Tesla, it's overwhelmingly likely that the car will come to rest on a piece of pavement and intact. If you run out of juice in an electric airplane, you turn into a glider, and it's far from assured that you'll end up at an airport or on pavement. I'm not scare-mongering, but that's the point of view the FAA will take on inspection and testing requirements for electric storage systems to achieve equivalent level of safety. I know when I add 40 gallons into my left tank (beyond the unusable fuel) that I have added 40 gallons of range. I need some similar assurance for battery capacity. (again, it's not me, but the FAA.) Just have a look at the annual inspection requirements for ELT and starting batteries for piston airplanes. And those are not propulsion systems. The batteries that run the AHRS in the G1000 and Aspen systems are also onerous and those batteries are crazy expensive relative to their capacity. I can see electrics working for flight school airplanes, especially if they can get the 80% recharge time down under 2 hours. I don't see them as practical for cross-country travel anytime soon without advances in battery tech; those are inevitable, but I don't see them displacing liquid organic fuels in my flying career for 1000nm legs.
- mahyarm 13y ago
  I would think inspecting & maintaining the actual capacity of the battery would be part of the automated charging system. It would be recorded to a fine a amount of detail. Most airplanes have a more predictable energy consumption model than a typical consumer car also, and since the typical pilot is more sophisticated, can afford to show a more complicated energy display for more accurate energy consumption and range assumptions. Electric aircraft currently would be very useful for people who live on an island or island cluster or want to do frequent short hop flights. For example Hawaii, the Caribbean, Indonesia, the Philippines, Seattle and the near by gulf islands, etc. I can take a ferry boat for 3 hours at scheduled times or I can hop on my plane for 30 minutes at any practical time at the same cost really changes things for island dwellers. I could live on an island and theoretically commute to work every day for 45minutes of total travel time. Going to Tahoe every weekend wont be a big deal, etc. It would be also useful for future automated air taxis, since the energy costs would soon dwarf the cost of everything else in those situations.
- logfromblammo 13y ago
  If it were my ass up in the air, I think I would prefer that the electric power to the drive motor(s) be provided by a very reliable Diesel-cycle or external combustion generator and not just a battery pack, at least with our current generation of battery technologies. #2 fuel oil is far more energy-dense than any battery that I can afford.
  - sokoloff 13y ago
    Agreed. Aviation diesels typically burn Jet-A (widely available at airports, obviously) which is similar in energy content to #2 (and about 50x the energy content of Li-ion batteries on a J/g basis).
    - logfromblammo 13y ago
      As far as I know, the major difference between Jet-A and #2 is that is has a much lower gel point than even the northern winter diesel fuels, because higher = colder. If you already have electric motors, wouldn't electrically heated fuel tanks suddenly be more possible than trying to divert waste heat out of fuel-burning engines? You could save a LOT of money on fuel if you could use off-road #2 oil instead of Jet-A.
      - sokoloff 13y ago
        Dry adiabatic lapse rate is approximately 3C per 1000'. I regularly fly at high VFR altitudes or low flight levels in my private (gas, piston IC) airplane. Even confining yourself to 15K feet, you'd be ~45C or 81F lower than the sea-level temp (assuming the air was totally dry, so maybe call it 35C or 63*F). The wings are extremely effective radiators, and wet wing tanks have fuel right against the outer wing surface. So, you're going to need to dump an enormous amount of energy into the fuel to keep it heated and non-gelled, which is why we have Jet-A, and in fact many jets need to add Prist anti-icing agent, and even some high-flying piston engine airplanes run their avgas through oil-to-fuel heat exchangers. So, even if you're going to fly your diesel engine (or diesel generator) airplane in the mid-teens, you're probably still going to want to use Jet-A, both for its superior anti-gel properties but also because of the supply chain dedicated to getting Jet-A to a great many airports where you'd want to operate from.

by leoedin 13y ago

sokoloff 13y ago

I don't think you're taking into account the vastly increased battery maintenance, inspection and capacity testing that will be required. Yes, you'll save a lot on not maintaining a piston IC engine. You'll give some of that back in inspection processes to ensure that you don't have 95% of the range that you think you have. If you run of out power in a Leaf or a Tesla, it's overwhelmingly likely that the car will come to rest on a piece of pavement and intact. If you run out of juice in an electric airplane, you turn into a glider, and it's far from assured that you'll end up at an airport or on pavement. I'm not scare-mongering, but that's the point of view the FAA will take on inspection and testing requirements for electric storage systems to achieve equivalent level of safety. I know when I add 40 gallons into my left tank (beyond the unusable fuel) that I have added 40 gallons of range. I need some similar assurance for battery capacity. (again, it's not me, but the FAA.) Just have a look at the annual inspection requirements for ELT and starting batteries for piston airplanes. And those are not propulsion systems. The batteries that run the AHRS in the G1000 and Aspen systems are also onerous and those batteries are crazy expensive relative to their capacity. I can see electrics working for flight school airplanes, especially if they can get the 80% recharge time down under 2 hours. I don't see them as practical for cross-country travel anytime soon without advances in battery tech; those are inevitable, but I don't see them displacing liquid organic fuels in my flying career for 1000nm legs.

mahyarm 13y ago
I would think inspecting & maintaining the actual capacity of the battery would be part of the automated charging system. It would be recorded to a fine a amount of detail. Most airplanes have a more predictable energy consumption model than a typical consumer car also, and since the typical pilot is more sophisticated, can afford to show a more complicated energy display for more accurate energy consumption and range assumptions. Electric aircraft currently would be very useful for people who live on an island or island cluster or want to do frequent short hop flights. For example Hawaii, the Caribbean, Indonesia, the Philippines, Seattle and the near by gulf islands, etc. I can take a ferry boat for 3 hours at scheduled times or I can hop on my plane for 30 minutes at any practical time at the same cost really changes things for island dwellers. I could live on an island and theoretically commute to work every day for 45minutes of total travel time. Going to Tahoe every weekend wont be a big deal, etc. It would be also useful for future automated air taxis, since the energy costs would soon dwarf the cost of everything else in those situations.
logfromblammo 13y ago
If it were my ass up in the air, I think I would prefer that the electric power to the drive motor(s) be provided by a very reliable Diesel-cycle or external combustion generator and not just a battery pack, at least with our current generation of battery technologies. #2 fuel oil is far more energy-dense than any battery that I can afford.
- sokoloff 13y ago
  Agreed. Aviation diesels typically burn Jet-A (widely available at airports, obviously) which is similar in energy content to #2 (and about 50x the energy content of Li-ion batteries on a J/g basis).
  - logfromblammo 13y ago
    As far as I know, the major difference between Jet-A and #2 is that is has a much lower gel point than even the northern winter diesel fuels, because higher = colder. If you already have electric motors, wouldn't electrically heated fuel tanks suddenly be more possible than trying to divert waste heat out of fuel-burning engines? You could save a LOT of money on fuel if you could use off-road #2 oil instead of Jet-A.
    - sokoloff 13y ago
      Dry adiabatic lapse rate is approximately 3C per 1000'. I regularly fly at high VFR altitudes or low flight levels in my private (gas, piston IC) airplane. Even confining yourself to 15K feet, you'd be ~45C or 81F lower than the sea-level temp (assuming the air was totally dry, so maybe call it 35C or 63*F). The wings are extremely effective radiators, and wet wing tanks have fuel right against the outer wing surface. So, you're going to need to dump an enormous amount of energy into the fuel to keep it heated and non-gelled, which is why we have Jet-A, and in fact many jets need to add Prist anti-icing agent, and even some high-flying piston engine airplanes run their avgas through oil-to-fuel heat exchangers. So, even if you're going to fly your diesel engine (or diesel generator) airplane in the mid-teens, you're probably still going to want to use Jet-A, both for its superior anti-gel properties but also because of the supply chain dedicated to getting Jet-A to a great many airports where you'd want to operate from.