Nothing on recharging the battery in the landing phase, so room for improvement.
Not really much room. Unlike a car going down a hill, an airplane descending still wants thrust from the engines, just not as much as in cruise.
Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
31–40 of 104 posts
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#32I think there are startups making a similar sort of engine for general aviation. It's good to see that there is development of the same idea for commercial aviation. This isn't like a hybrid car. It's a parallel hybrid, where the gas engine is just big enough for efficient cruise at altitude, and the electric motor/generator provides extra power for takeoff and ascent (or go-around power), and then charges slowly dur…
The fuel burn of take-off and climb substantially lightens the aircraft for cruise. Electric batteries have no such effect, you're carrying all that dead weight for the rest of the flight. This reduces the passenger or cargo capacity of the aircraft, which reduces potential revenue. And what if you need two go-arounds?
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Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#33Earlier quoted context omitted.
You don't do a full climb after a go-around, so the heights are not equal, and the mass is less since you've expended fuel. You also retain some kinetic energy but I assume that is closer to a negligible effect. Also, PE = mgh is probably an not a great formula for energy cost of takeoff/go-around, as there are probably large costs it ignores (gravity loss, less efficient engine use, maybe less efficient turbines?).…
Not a pilot, but on approach for landing you bleed off a lot of energy. For a go-around you need to reverse your descent and build up enough energy to fly away again. Take-off/Go-around tends to be the same throttle setting, AFAIK. Of course it also depends on how early you decide to throw away the approach and go around. Doing it at 1000 feet is different from bouncing it off the runway.
but the point they were making is that it inevitably takes less energy to get to a level flying state (in similar weather conditions) due to fuel consumption.
so, unless the pilot is fighting weather it would make sense that equal throttle levels and equal pitch plans in equal weather conditions would require less and less fuel burn until the tanks are empty.
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#34Earlier quoted context omitted.
The Prius uses a planetary gear set to blend power of the engine with that of the two motor-generators. Both the engine and motors are used at all speeds. Particularly during highway acceleration the entire assembly rotates in the same direction.
This is a great related watch if you have some time to kill: https://youtu.be/KnUFH5GX_fI
That's such a fantastic video. I never totally grasped why hybrids were so much more efficient, because my naive assumptions about how they worked were so simplistic. The real-time graphs he showed were excellent for making his points.
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#351300 HP electric engine power, now that's an achievement. I do wonder if prop engines can act as "windmills" (similar to turbine engines, which often in accidents still have been found to provide a bit of hydraulic power), which means regenerative braking could be used instead of speedbrakes.
After they land, they usually sit around for a while. Not really super important to charge the battery on decent I wouldn't think. Would be interesting to get rid of the battery entirely (or reduce the size) and have a beefed up magsafe plug that was attached during lift off, and came unplugged once it was at cruising altitude.
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#36I think there are startups making a similar sort of engine for general aviation. It's good to see that there is development of the same idea for commercial aviation. This isn't like a hybrid car. It's a parallel hybrid, where the gas engine is just big enough for efficient cruise at altitude, and the electric motor/generator provides extra power for takeoff and ascent (or go-around power), and then charges slowly dur…
Hybrid cars are mostly parallel hybrids. Only the Chevy Volt comes to mind as a serial hybrid.
Chevy Volt was still a parallel hybrid. The gasoline engine was used for driving the wheels for highway cruise because it was more efficient. I think the range extender version of the BMW i3 was a pure serial hybrid though
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#37Earlier quoted context omitted.
> I assume that a go-around requires less sustained power output than a full climb from takeoff, No. Source 1: PE = mgh Source 2: am pilot
You don't do a full climb after a go-around, so the heights are not equal, and the mass is less since you've expended fuel. You also retain some kinetic energy but I assume that is closer to a negligible effect. Also, PE = mgh is probably an not a great formula for energy cost of takeoff/go-around, as there are probably large costs it ignores (gravity loss, less efficient engine use, maybe less efficient turbines?).…
> You don't do a full climb after a go-around,
an IFR missed approach can have you climb quite high, especially in areas with serious terrain. Example: https://aeronav.faa.gov/d-tpp/2607/00346IZLZ17R.PDF airport is at 4400 feet over sea level, but missed approach says: climb to 13,000. Also, some go arounds will lead you to have to divert to an alternate airport, getting there may require climbing high to clear terrain or gaining required engine efficiency to fly the distance.
> And the mass is less since you've expended fuel
In our theoretical aircraft with batteries, mass is the same.
> You also retain some kinetic energy but I assume that is closer to a negligible effect.
Negligible indeed.
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#38Earlier quoted context omitted.
The fuel burn of take-off and climb substantially lightens the aircraft for cruise. Electric batteries have no such effect, you're carrying all that dead weight for the rest of the flight. This reduces the passenger or cargo capacity of the aircraft, which reduces potential revenue. And what if you need two go-arounds?
On anything but very short flights most of the fuel is spent on cruising.
I would classify 290 miles as a very short flight, that's like 1-2 hours or something?
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#39Earlier quoted context omitted.
You don't do a full climb after a go-around, so the heights are not equal, and the mass is less since you've expended fuel. You also retain some kinetic energy but I assume that is closer to a negligible effect. Also, PE = mgh is probably an not a great formula for energy cost of takeoff/go-around, as there are probably large costs it ignores (gravity loss, less efficient engine use, maybe less efficient turbines?).…
> You don't do a full climb after a go-around, an IFR missed approach can have you climb quite high, especially in areas with serious terrain. Example: https://aeronav.faa.gov/d-tpp/2607/00346IZLZ17R.PDF airport is at 4400 feet over sea level, but missed approach says: climb to 13,000. Also, some go arounds will lead you to have to divert to an alternate airport, getting there may require climbing high to clear terra…
> you climb quite high, especially in areas with serious terrain.
Interesting, thanks.
> In our theoretical aircraft with batteries, mass is the same.
The fuel that's expended during cruise reduces the mass.
Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
#40anything that gets rid of leaded fuel on prop aircraft is a win even if 0% efficiency improvement