2600hp Hybrid Electric Turboprop regional airliner being tested

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Doggzilla

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Many of our members have been discussing hybrid technology for years. Well, it looks like someone else took notice as well. It appears that the system works very well and has a lot of potential.

United Technologies has equipped a Q400 with a 2 Megawatt hybrid system (2600hp) and says that it shows at least a 30% fuel savings.

They say the results cut the aircraft range to about 600nm, but that almost all Q400 routes are shorter than that so it doesn't matter anyways.

They also say that an airframe designed specifically to use the hybrid system would be even more efficient and could almost eliminate the penalties.

https://www.flightglobal.com/news/articles/utc-to-test-hybrid-electric-propulsion-system-on-da-456942/
 

Tiger Tim

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Sort of. Far as I know they're presently building the building in which they'll start testing a powerplant that they hope to test on a Dash 8-100. What's also interesting is that Flight Global's article (above) says the system will be primarily electric with the turbine supplementing power in the climb, while Aviation Week has published that the turbine will basically be running at its design point (100%) all the time and supplemented by electric power for the climb, and using the motor to regenerate power in the descent.
 

BBerson

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It is proposed for 2022. No results that prove anything yet.
It would be lighter and simpler to just install a 2 megawatt second turbine for takeoff only instead of that electric system. The efficiency comes from operating a smaller main engine.
 

Vigilant1

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It's hard to believe that the difference in specific fuel consumption is enough to offset the increased empty weight. I don't think it will prove to be a hit--greater complexity and MX costs, more frequent fuelling (these planes often turn fast), and a less flexible plane. It will keep the fuel trucks hopping.
 

Tiger Tim

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It would be lighter and simpler to just install a 2 megawatt second turbine for takeoff only instead of that electric system.
Think so? I was figuring the electric motor is basically there to add torque to the propeller gearbox in parallel with the compressor section (to use P&W's terminology). Seems to me if someone wanted to do some testing and use a lot of existing and tested hardware, one could probably start with something like the Soloy Dual Pac but replace one of the PT-6s with a big electric motor. There's still the matter of batteries and controllers and whatnot, but at least a gearbox exists.
 

ScaleBirdsPaul

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I’ve not heard of the Dual PAC, but that’s pretty **** cool.

I’m skeptical of any hybrid airplane, but at least this concept seems somewhat feasible. The article doesn’t mention the total battery capacity - how long is that 2600hp available?
 

BBerson

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Think so? I was figuring the electric motor is basically there to add torque to the propeller gearbox in parallel with the compressor section (to use P&W's terminology). Seems to me if someone wanted to do some testing and use a lot of existing and tested hardware, one could probably start with something like the Soloy Dual Pac but replace one of the PT-6s with a big electric motor. There's still the matter of batteries and controllers and whatnot, but at least a gearbox exists.
That Dual Pac looks like a continuous twin engine. The Dash 8 doesn't need 4 engines in cruise. So shut down two of the four after takeoff and cruise on two turbines at 100% design efficiency. Turbines are not efficient at 50% output.
So it could be done the same with electric. But I think the takeoff turbine is lighter than any electric/battery combo.
Nothing beats a turbine for power to weight. That's why no current five seat or larger helicopters are piston or electric.
 

markaeric

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It's probably safe to assume UTC engineers crunched some numbers which convinced them that tests were worth pursuing. All up, electric power-to-weight currently leaves quite a bit to be desired, but motors are pretty good (think Rocket Labs' ~100hp coke can sized turbopump motors), with high efficiencies, the capability of regeneration, and the fact that battery technology is steadily improving due to multi-trillion dollar market forces. UTC will be able to continually reap the benefits of that last point with minimal investment on their part. Also, motors would likely require less maintenance than a gas turbine, and batteries stand a greater chance of dropping in price than an efficient modern jet engine. Parallel hybrids have proven themselves in automobiles, and they just might do it in aircraft too. Whatever the end result is, I'm glad they're at least giving it a go.
 

BJC

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It's probably safe to assume UTC engineers crunched some numbers which convinced them that tests were worth pursuing.
It also could be that someone high in management, or a group of shareholders, forced it without any consideration for the physics involved.

BJC

Edit: I can attest to the fact that lots of money is spent by corporations without any potential benefit other than political correctness, perceived, but not real, environmental benefit, or to placate noisy shareholders.
 
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BBerson

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Regen works with autos in city traffic where stops occur at every block.
No such use in aviation. Aviation transport is like a non stop highway cruise where regen is never required.
Even the final glide takes some engine power and no one would want to drop out of the sky attempting regen.
Regen is proposed for gliders in a thermal. But hardly practical for transport
 

akwrencher

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The difficulty in comparing land based hybrids and air based hybrids is, no stop and go traffic in the air, which is where hybrids give benefits in smaller i.c. and regenerative braking. Regeneration on decent, but how does that improve range significantly?
 

Vigilant1

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The stated case of using the batteries/electric motors for TO and climb and using the just-big-enough turbine engines for cruise and to recharge the batteries also seems overly dependent on a perfect situation. What happens if there's a need to land earlier (passenger with a physiological incident, etc)? If there's not enough juice to fly a go around/missed approach, is it really safe to fly the approach yet? And these planes sometimes are put on very short legs (30 minute flights)-- a turbine with enough excess capacity to recharge the batteries (with losses) in that time would be large enough to perform the climb without the boost.
I'm suspecting some non-market forces are behind this project.
 
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markaeric

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From Pipistrel's website regarding their electric trainer:
The Alpha Electro is optimized for traffic-pattern operations, where 13% of energy is recuperated on every approach, increasing endurance and at the same time enabling short-field landings.
Sure, cars may derive greater benefit from a hybrid setup from typical usage, but that doesn't mean it's useless for a plane.

Proper battery sizing and utilization will dictate whether it has sufficient capacity for a go-around. Tradeoffs will need to be balanced.

Very short legs would be more suitable for all electric. Airliners try to use the proper tool for the job, otherwise they wouldn't need such a diverse fleet. Where a hybrid would fit in is TBD.
 

Doggzilla

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For those of you wondering, its actually backed by Boeing HorizonX, JetBlue Technology Ventures and Washington state’s Green Energy Fund.

And the reason its more efficient is that it allows the generator turbines to operate at their most efficient RPM across the entire flight envelope.

Existing engines are inefficient because the takeoff power requirements mean the turbines cant be tailored for cruise.
 

pictsidhe

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If the battery is to boost climb and is charged on the descent, it should be almost fully charged at landing. No doubt they'll aim to top it off in the taxi phase. A go around doesn't need climb power for very long, so even a 1/2 charged battery that boosts climb to 15,000 is going to have enough juice to get you back up to 5,000 quickly.
It's going to be intersting to see how they integrate it. Electric boost the turbofan?
 

Doggzilla

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Its actually based on the Q400 turboprop and will have the electric motors driving the props with the turbines completely separate and driving gensets.

What I wonder is if the systems will be isolated or if one side will be able to drive the other if a turbine or battery fails.
 

Kyle Boatright

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If the battery is to boost climb and is charged on the descent..
So, my question is this... The most efficient profile is to fly as far as possible at cruising altitude, then (effectively) glide all of the way to touchdown. Regenerating power on the descent means either something is in windmill mode (i.e. generating mode), or the engines are running at higher than idle power to charge the batteries.

So, you're carrying more weight with the batteries and all of the electric drive stuff AND you're losing efficiency in the descent from cruise.

I'd love to see the math that says this is more efficient.
 

BBerson

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Regen only possibly makes theoretical sense in a motorglider with the engine off in a strong thermal. An airliner on approach with both engines off and in regen would be insanity. Passengers want a 3° descent. Which requires power.
 
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