4 ms·

I wonder why there's no effort to make affordable turboprop engines in the power range required for typical GA usage. Sure, small turbines take an efficiency hi

by jabl 10y ago

I wonder why there's no effort to make affordable turboprop engines in the power range required for typical GA usage. Sure, small turbines take an efficiency hit (boundary layer friction and whatnot), but still? And what makes them so expensive compared to piston engines? But yeah, maybe small diesel engines are a better approach, shrug... And some of the designs look neat, e.g. opposed piston two-stroke like ye olde Junkers engines. There's also efforts to create and certify an unleaded replacement for 100LL. Probably won't solve the price and availability issues with avgas, but at least it doesn't contain lead (which in addition to the environmental issues is a PITA for refineries ) and I guess it's a hedge against that last TEL-producing factory on the planet going bankrupt and grounding the fleet..

Gravityloss 10y ago
Primary training aircraft at least have big potential in electric propulsion.
- Gibbon1 10y ago
  Hybrid Electric aircraft are kinda interesting when you start running the numbers. The weight of the batteries of course reduces the amount of fuel the aircraft can carry. However increased efficiency reduces the amount of fuel you need to carry. There are a bunch of other advantages which would improve safety. In particular better throttle response. A problem with turbine engines is when an aircraft is hit by wind shear during landing you need more power right now, and turbines have lag. And also when you shutdown an engine in a multi-engine aircraft you have a serious thrust imbalance. Hybrid electric would allow power to be routed evenly to each fan as needed.
  - Gravityloss 10y ago
    Traditionally you deal with the lag with variable pitch propellers. But with electric motors you can have a lot of immediate / momentary torque and power and instead vary the propeller speed. I think what is aimed at with electrics is you get a lot simpler aircraft with far lower operating costs and higher reliability and availability. No engine maintenance, no variable pitch propeller, no fuel systems (you do have batteries but they should be self contained man changeable systems). No huge checklists with warmup etc procedures on the ground. It's worth it to just have 30-60 minutes of flight time, because you still get to train takeoffs and landings. Maybe the instructor and student can first swap the new battery with 5x20 kg units or so, take off, do a few touch and go:s, land, then let the next guys do the same.

by jabl 10y ago

Gravityloss 10y ago

Primary training aircraft at least have big potential in electric propulsion.

Gibbon1 10y ago
Hybrid Electric aircraft are kinda interesting when you start running the numbers. The weight of the batteries of course reduces the amount of fuel the aircraft can carry. However increased efficiency reduces the amount of fuel you need to carry. There are a bunch of other advantages which would improve safety. In particular better throttle response. A problem with turbine engines is when an aircraft is hit by wind shear during landing you need more power right now, and turbines have lag. And also when you shutdown an engine in a multi-engine aircraft you have a serious thrust imbalance. Hybrid electric would allow power to be routed evenly to each fan as needed.
- Gravityloss 10y ago
  Traditionally you deal with the lag with variable pitch propellers. But with electric motors you can have a lot of immediate / momentary torque and power and instead vary the propeller speed. I think what is aimed at with electrics is you get a lot simpler aircraft with far lower operating costs and higher reliability and availability. No engine maintenance, no variable pitch propeller, no fuel systems (you do have batteries but they should be self contained man changeable systems). No huge checklists with warmup etc procedures on the ground. It's worth it to just have 30-60 minutes of flight time, because you still get to train takeoffs and landings. Maybe the instructor and student can first swap the new battery with 5x20 kg units or so, take off, do a few touch and go:s, land, then let the next guys do the same.