5 ms·

The majority of the efficiency gains in this concept come from max power requirements, rather than energy recovery. Aircraft engines' max power requirements com

The majority of the efficiency gains in this concept come from max power requirements, rather than energy recovery. Aircraft engines' max power requirements come from take-off performance requirements. The electric engine-portion provides sufficient power at takeoff / climb-out to allow the gas powered portion to be more optimally designed for cruise conditions. This providing net savings overall. This isn't well explained in the article, but has been batted around the aviation industry and aerospace academic world for a while.

Kon-Peki 3y ago
I can’t imagine that regenerative braking would be a thing. If this kind of craft makes it into service, regulations are going to require a “fully” charged battery before beginning the final approach to handle the chance of an aborted landing. So when the plane touches down successfully, it won’t need the electricity. Charging during descent is much more likely to be some sort of air brake generator. You can imagine, though, that a well-done “electric take off assist” would be seen as a safety improvement.
- simne 3y ago
  About aborted landing. Regulations considering all such things, because of this, decision to make landing, taken by captain, considering weather conditions, technical state of aircraft, and physical state of crew. So, in ideal conditions, many such planes could make landing on just some 200m, but in reality, they flight only on strips approx 1500m or longer, for safety considerations.
  - Kon-Peki 3y ago
    I’m not sure if we are agreeing with each other or not :) A hybrid aircraft is going to have smaller engines that produce less thrust, and probably take longer to get to max thrust. Because the electric motors make up the difference during takeoff. Consider what happens when lightning strikes an airport. An immediate ground stop is issued and every airplane in the air that can GTFO has to GTFO. And remember the near accident earlier this year when the FedEx plane almost landed on the Southwest plane. A regenerative braking system reduces the maximum thrust available if an emergency happens near the ground when you are landing and you really really want to stay in the air. I don’t think we are willing to make that trade off for lower carbon emissions. Which is why I think they would find a way to make sure the batteries are charged before that final descent. Now that I think of it, perhaps I should be clear that when I see “regenerative braking”, I am thinking about something on the brakes on the wheels on the landing gear, which perhaps is not how everyone else thinks of it.
    - simne 3y ago
      > A hybrid aircraft is going to have smaller engines that produce less thrust, True. > and probably take longer to get to max thrust False. But it is not important. For passenger planes, usual, to have rich wing mechanization especially mentioned model is one of most sophisticated on this. But mechanization have huge drawback - it usually increase Cx very significant when activated, so engines must run with moderate power (without mechanization, descending made with throttled engines to near zero). After touchdown, plane is technically on ground, but in reality it usually have very high speed, or huge kinetic energy. When engines ok, on nearly all civilian planes, they turned to reverse and braking (military planes usually don't have reverse). And only after speed slowed to ~150km/h (approx 100mph), activated wheel brakes. And this is not because I want to do so, but because kinetic energy is too high for wheel brakes, and because it is just extremely dangerous to brake the wheels on so high speed. Some decades ago, plane constructors even included special ballast to breaks to accumulate heat from plane braking, and for example, Concord does not have reverse, totally depend on wheel brake, for it created ABS system, and it's breaks cooled approx 11 hours. You don't hear me. Regulations consider worst case, so for this plane, will be required longer strips than for original (non-hybrid). Nothing less, but nothing more.
      - simne 3y ago
        For speed and brake issue, remember kinetic energy formula - energy grow as square of speed.

Kon-Peki 3y ago

I can’t imagine that regenerative braking would be a thing. If this kind of craft makes it into service, regulations are going to require a “fully” charged battery before beginning the final approach to handle the chance of an aborted landing. So when the plane touches down successfully, it won’t need the electricity. Charging during descent is much more likely to be some sort of air brake generator. You can imagine, though, that a well-done “electric take off assist” would be seen as a safety improvement.

simne 3y ago
About aborted landing. Regulations considering all such things, because of this, decision to make landing, taken by captain, considering weather conditions, technical state of aircraft, and physical state of crew. So, in ideal conditions, many such planes could make landing on just some 200m, but in reality, they flight only on strips approx 1500m or longer, for safety considerations.
- Kon-Peki 3y ago
  I’m not sure if we are agreeing with each other or not :) A hybrid aircraft is going to have smaller engines that produce less thrust, and probably take longer to get to max thrust. Because the electric motors make up the difference during takeoff. Consider what happens when lightning strikes an airport. An immediate ground stop is issued and every airplane in the air that can GTFO has to GTFO. And remember the near accident earlier this year when the FedEx plane almost landed on the Southwest plane. A regenerative braking system reduces the maximum thrust available if an emergency happens near the ground when you are landing and you really really want to stay in the air. I don’t think we are willing to make that trade off for lower carbon emissions. Which is why I think they would find a way to make sure the batteries are charged before that final descent. Now that I think of it, perhaps I should be clear that when I see “regenerative braking”, I am thinking about something on the brakes on the wheels on the landing gear, which perhaps is not how everyone else thinks of it.
  - simne 3y ago
    > A hybrid aircraft is going to have smaller engines that produce less thrust, True. > and probably take longer to get to max thrust False. But it is not important. For passenger planes, usual, to have rich wing mechanization especially mentioned model is one of most sophisticated on this. But mechanization have huge drawback - it usually increase Cx very significant when activated, so engines must run with moderate power (without mechanization, descending made with throttled engines to near zero). After touchdown, plane is technically on ground, but in reality it usually have very high speed, or huge kinetic energy. When engines ok, on nearly all civilian planes, they turned to reverse and braking (military planes usually don't have reverse). And only after speed slowed to ~150km/h (approx 100mph), activated wheel brakes. And this is not because I want to do so, but because kinetic energy is too high for wheel brakes, and because it is just extremely dangerous to brake the wheels on so high speed. Some decades ago, plane constructors even included special ballast to breaks to accumulate heat from plane braking, and for example, Concord does not have reverse, totally depend on wheel brake, for it created ABS system, and it's breaks cooled approx 11 hours. You don't hear me. Regulations consider worst case, so for this plane, will be required longer strips than for original (non-hybrid). Nothing less, but nothing more.
    - simne 3y ago
      For speed and brake issue, remember kinetic energy formula - energy grow as square of speed.