Gas/electric hybrid powertrain in aviation

[MetroMPG]

Via Autopia:

100% electric drive in aviation is nothing new - there are more than a few light & ultralight planes doing that now.

But this is the first hybrid powerplant I've seen.



Autopia reported on a German plane maker that has downsized its engine to a more efficient size for cruising, and added a motor and small battery pack to assist during take-off & climbing.

The pilot pushes the single power lever forward for takeoff, and both motors are running to provide the equivalent of a 160-hp engine. Once the four-seat airplane is at altitude, the pilot reduces power for cruise and the electric engine is no longer delivering power. This leaves a 115-hp gasoline engine to provide the cruise power, which is more efficient than the 160-hp engine the hybrid system replaces

(As an aside, I think people often forget that that's one of the major benefits of a hybrid drivetrain: it lets you "undersize" the internal combustion engine, since peak power demands are met by the ICE + electric. Hybrids are not just about being able to motor around at low speeds on battery power alone.)

It even has regen:

Like its car cousin, the aircraft engine can also use regenerative braking. When a pilot reduces power for descent, the windmilling propeller is used to recharge the battery pack for the next flight.

The electric components are an added safety feature as well, giving the pilot additional time to handle an ICE failure (getting it restarted, or finding the best emergency landing spot).

More: Hybrid Power Comes to Aviation | Autopia | Wired.com

[Daox]

Interesting, but I wouldn't think the benefits are nearly as great as they are with a automobile.

[MetroMPG]

Why not? Planes spend most of their time at cruise, so I figure if they can reduce cruising fuel consumption by downsizing the engine, it'd help a fair amount.

However it does have me wondering why they don't just use a turbocharged engine. Same effect, no? (Smaller displacement engine = better FE under light load; but turbo for power when needed.)

[dcb]

Turbos don't like valve overlap, whereas normally aspirated engine does. Maybe? The regen is uber-cool too.

Aside from takeoff though (and exceptionally crowded airspace) planes can P&G anytime, climb @bsfc peak to simulate hill loading, and glide back to your starting altitude.

[jamesqf]

I think the real reasons for the rarity of turbochargers is cost & FAA regulations. Most aircraft engines are basically 50 year old technology - hell, a lot of general aviation planes are 40 or more - and you can't bring out anything new (except under experimental class) without going through the certification process, or modify an existing plane without getting a supplimental type certificate. Reliable, low-cost turbos have only been around for a couple of decades, so I can't legally go out and buy an aftermarket turbocharger and bolt it on the O-360 in a '65 Piper Cherokee.