Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency • Hacker News Board

Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency

#101

Post by [deleted] » Fri, Jul 24, 2026, 4:47 PM UTC

arijun wrote: post #96

cwillu wrote: post #89

Earlier quoted context omitted.

It's a planetary geartrain, with electric motors on the outer and inner, and the gas on the middle. If the electric is _completely_ dead, the gas will just spin without driving the wheels at all. There is no first gear, the mechanical advantage and “clutching” all comes from the inner electrical motor driving the sun gear, while the electric boost/drive comes from the electric motor on the drift shaft (which is on th…

> the gas will just spin without driving the wheels ... and instead drive one of the motors, generating electricity to power the other motor to push the car forward. I feel like that video you're mentioning did a poor job if it didn't describe one of the more important and clever aspects of the Prius's design.

[deleted]

Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency

#102

Post by Melatonic » Fri, Jul 24, 2026, 10:04 PM UTC

Toutouxc wrote: post #92

Melatonic wrote: post #65

Earlier quoted context omitted.

Yea that makes sense. Can't be hitting stall speed. Although maybe there's an argument for less load / wear on the turbine motor if the electric motors could be involved during landing ? Or maybe you keep your downsized turbine motor running closer to peak efficiency even during landing and increase the mechanical energy harvesting to your APU or alternator thing or whatever to control speed and use that to charge a…

Supercapacitors are heavy and basically useless for any kind of propulsion. Note how neither e-bikes nor EVs use them. You need a proper lithium battery if you need any usable amount of energy.

Makes sense. I suppose good batteries may have enough output anyways

Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency

#103

Post by Toutouxc » Sat, Jul 25, 2026, 1:39 PM UTC

repiret wrote: post #100

Toutouxc wrote: post #94

Earlier quoted context omitted.

Exactly like a car going down a hill, a descending plane doesn't need any thrust for anything in particular. Planes are notoriously aerodynamic and can trade altitude for speed easily. (Note how gliders don't need any thrust at all.) There are SOME planes where you want to avoid the "no thrust" situation because their implementation of "no thrust" can lead to weird aerodynamics or prop pitch behavior, or can stress t…

A car going down a slight hill on the freeway still needs a bit of gas to maintain speed. My assertion is that there are no turboprop plans that can maintain a 3° glideslope at normal approach speed without thrust from the engines. If you think there is such a plane, name the type, and show me a citation from it's POH to support the claim.

> an airplane descending still wants thrust from the engines, just not as much as in cruise

> My assertion is that there are no turboprop plans that can maintain a 3° glideslope at normal approach speed without thrust from the engines

These are very different claims, in every dimension. Yes, the final approach is intentionally very shallow, is a minor part of the entire descent phase and the plane flies it in a very "dirty" configuration (gear down, flaps). Yes, the prop on turboprops causes a ton of drag. Are we going to mention the fact that a 737 or an A320 (the most common airliners in the world) are NOT turboprops, they both have a glide ratio comparable to trainer gliders and are fast as fuck?

Re: Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency

#104

Post by repiret » Sun, Jul 26, 2026, 1:35 AM UTC

Toutouxc wrote: post #103

repiret wrote: post #100

Earlier quoted context omitted.

A car going down a slight hill on the freeway still needs a bit of gas to maintain speed. My assertion is that there are no turboprop plans that can maintain a 3° glideslope at normal approach speed without thrust from the engines. If you think there is such a plane, name the type, and show me a citation from it's POH to support the claim.

> an airplane descending still wants thrust from the engines, just not as much as in cruise > My assertion is that there are no turboprop plans that can maintain a 3° glideslope at normal approach speed without thrust from the engines These are very different claims, in every dimension. Yes, the final approach is intentionally very shallow, is a minor part of the entire descent phase and the plane flies it in a very…

Most transport category aircraft have a better glide ratio than most single engine GA planes when configured for best glide. But they don’t cruise descend at best glide speeds or at idle thrust.

I’m talking about turbo props because the article’s hybrid technology is specifically for turbo props.

My challenge stands: find me a turbo prop that would be happy at idle thrust for either approach or cruise descent.