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Hybrid-Electric Aicraft Engine Targeting 30% Fuel Efficiency
- xnx 2mo ago[dead]
- Someone 2mo agoNot “30% fuel efficiency”, but an improvement of 30%. FTA: “The project aims to demonstrate up to 30% improved fuel efficiency for a typical 250-nautical-mile regional turboprop mission”
- c0n5pir4cy 2mo agoI was so confused by the title - I thought jets were fairly efficient at ~40%-50% of theoretical maximum and turbofans can't be that far behind. It would maybe make sense for a single prop aircraft. 30% improvement makes much more sense.
- stymaar 2mo agoHN title mangling strikes again.
- avidiax 2mo agoI 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 during cruise if needed. This means that the battery is quite small and light, having only enough charge to take off and get to altitude. I suspect that this system probably improves safety as well, if architected properly. If one or both of the gas engines fail, so long as they are not seized, that electric motor can still provide some power for diversion.
- SoftTalker 2mo agoThe 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?
- 0cf8612b2e1e 2mo agoEnergy density of liquid fuels cannot be beat by batteries, so this is not competitive if you are looking to maximize cargo. However, there are plenty of short haul flights: private jets, island hopping, regional routes where you need to move little mass.
- xattt 2mo agoExactly. A hybrid passenger car can tolerate unpredictable power output that may come with an auxiliary power setup that may or may not be available when stronger dynamics are called for. A plane doesn’t have this luxury and needs predictable output. The fossil fuel engine either needs a sacrificial “overboost” mode for emergencies (at the cost of wear/long-term longevity), or has to be sized for full power at the ultimate cost of efficiency.
- Melatonic 2mo agoSo theoretically if the electric motors fail (or battery is dead) an engine could be sized and designed smaller (for cruise efficiency) but have some sort of boost mode that still ensures safety ? At the cost of increased maintenance or wear or something if it must be used
- hobonation 2mo agoValid. Perhaps it's not all negative: the electric portion could give a pilot a bit more glide than the gas portion dies.
- Tade0 2mo agoOn anything but very short flights most of the fuel is spent on cruising.
- soperj 2mo agoOnly AI stories show up now, so they had to call it an Ai craft I guess.
- mschuster91 2mo ago1300 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.
- paunchy 2mo agoI've seen references to this capability in reporting elsewhere. It's less useful in an aircraft than a car because you can gradually descend, reducing power proportionally as you're preparing to land. But I'm guessing this is part of where the claimed 30% improvement in efficiency comes from.
- soperj 2mo agoAfter 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.
- Melatonic 2mo agoAt that point seems like you might as well use a launch system like aircraft carriers use
- ssl-3 2mo agoThat would certainly help get the aircraft up to a speed where it has usable lift and can leave the ground. That's a good headstart, and it represents a significant amount of energy. A catapult launch can't help with the next 30,000 feet of climbing, though, while the impossible umbilical might.
- nradov 2mo agoThere would never be a reason to use windmilling props in flight for electrical generation. Even when descending, airliners like the Dash 8 need at least some forward thrust in order to maintain control and stay on the glide slope. They only use reverse thrust for a few seconds during the landing roll.
- MeteorMarc 2mo agoNothing on recharging the battery in the landing phase, so room for improvement.
- bell-cot 2mo agoNot an aerospace engineer - but that sounds like a lot of extra cost/complexity/weight, for pretty minimal benefit.
- repiret 2mo agoNot 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.
- Toutouxc 2mo agoExactly 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 the engine.
- repiret 2mo agoA 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.
- Toutouxc 2mo ago> 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?
- krunck 2mo agoI wonder if during descent instead of cutting power alot to control speed it can instead use the energy to charge the batteries.
- ggreer 2mo agoI'm not sure how that would help. If you're descending it's probably to land, and then you can recharge the batteries with electricity from the ground. That would be more efficient (and cheaper) than burning fuel to charge them.
- tgtweak 2mo agoSays that it's boost-only in all the literature I could see, so it can only add power to the prop not generate with it. Regardless, you don't really get into a position where you're harvesting energy in a plane - you just use less power while you're descending. Unlike in a car, most of a passenger jet's flight time is at speeds where drag (which squares with speed) basically means you'd have to nose down at a very aggressive angle to actually pick up speed without the engines providing thrust. The plane's engines are almost always under some kind of load until it is on the tarmac and slowing down so there isn't any opportunity to "regen" during a normal flight.
- Melatonic 2mo agoYea 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 small supercapacitor. In the event of an aborted landing the supercapacitor could provide a boost of thrust to your electric motors. This would keep wear on the battery lower and also allow it to dump energy at its peak efficiency
- Toutouxc 2mo agoSupercapacitors 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.
- ck2 2mo agoanything that gets rid of leaded fuel on prop aircraft is a win even if 0% efficiency improvement
- jabl 2mo agoThis is about replacing a turboprop with a slightly smaller turboprop and electric motor/generator+battery. The turboprop burns Jet-A, not leaded aviation gasoline.
- Schiendelman 2mo agoIf you care about leaded fuel, the culprit now is general aviation - small airports, Cessnas, not commercial flights. If you go work on it, let me know, I'll help you!
- Melatonic 2mo agoDont we have approved fuel replacement for leaded fuel now finally ? Also I swear there was a company replacing a push pull type plane with a hybrid ?
- Schiendelman 2mo agoWe don't require unleaded fuel for GA.
- _diyar 2mo agoThis is very clever: instead of focusing on electric only flight, just make the existing engine fly in the most efficient window while the electric engine buffers the flight profile. Like a big-boy prius.
- tgtweak 2mo agoMore like an Edison Motors hybrid system.
- m463 2mo agoI kind of wonder how the orders of magnitude work out for solar and wing area. Solar cells are actually quite thin and could be almost like paint on the wings of aircraft. I wonder if the energy generated vs required is even ballpark. There is plenty of sun at 30,000 feet during the day.
- mk_stjames 2mo agoMan this is a middle-schooler level napkin math question. Take a Boeing 777, it has a wingspan of about 60 meters, and I'll ballpark an average upper wing chord of about 7 meters, for a total upper flat area of about 420 square meters. High quality modern but standard single sided solar panels can do about 220 watts per square meter is full sunlight (around 22% efficiency tested at a 1000w/m^2 irradiance). So that is 92,400 watts at full power. 92kW is less than the peak power of a Nissan Leaf. 92kW is 123 horsepower. The two GE turbofans of a 777 are generating something like 40-50 MW of shaft power during cruise. MW.... megawatts. 50-60,000 horsepower. Plastering the wing surface of a commercial plane with solar panels would make up less than a quarter of a percent of the total power it uses to produce thrust at cruise, at best case with them fully-lit. Fully solar sailplanes do exist (NASA's Helios prototypes are an example) but that isn't anything close to a 'normal' aircraft with any appreciable payload/passengers. So, no need to wonder.
- m463 2mo agoI wish I could upvote you more than once. I now realize my middle-school math studies were sub-par :) yeah, I was thinking of the solar planes. I also didn't know that "horsepower at cruising speed" was something you could look up. obvious now, thanks!
- tgtweak 2mo agoRtx has an interesting patent [1] on this that highlights some of the novelties of this setup vs a traditional hybrid (planetary motor/generator like in a Prius): It's a boost-only motor, it doesn't/can't harvest energy on descent. The patented solution (transient smoothing under auto-throttle control) puts electric motors on both the low spool and high spool, then uses a power-splitting algorithm to route high-frequency thrust changes to the electric motors while keeping fuel flow nearly constant on the thermal engine (turbine). The turbine cruises at a steady operating point with tight compressor/turbine clearances and the electric motor smooths out the spikes that are normally there with turbulence and load changes. Benefits: lower fuel burn, longer turbine life (fewer blade-rub risks from speed variation), and smoother ride quality since the auto-throttle bandwidth improves. This setup (based on the various cutaways and photos so far) seems to be only a single 1MW motor so it only runs on the low spool but can still help modulate the turbine decently in the same way it does in the Koenigsegg Regera's hybrid electric setup, that removes the need for a flywheel because the electric motor can smooth out the gas motor's inherent lumpiness. Also disclosed in a previous press release [2], it's only a 200kWh battery so at 1MW peak boost (cited load during takeoff/ascent) it would only run for ~10-15 minutes at the beginning of the flight. Seems most of the savings are due in part to not using as much fuel during takeoff (~20% of a 1-hour flight's fuel) but also in large part to the under-sizing and optimization of the thermal turbine to keep it running in it's peak efficiency zone for more of the flight (~10% of a 1-hour flight's fuel). Curious how the safety margins work here - if the battery is depleted on takeoff (aborted takeoff) or there's an issue that requires descent-then-reascent, if the batteries can't be replenished in-flight there could be a power deficit in that window where you'd normally have 2+2MW of gas turbine power for the plane and now you only have 1+1mw of gas turbine power. [1] https://patents.google.com/patent/US20250296689A1/en https://patents.google.com/patent/US20250296689A1/en [2] https://www.aerospacetestinginternational.com/news/h55-delivers-batteries-for-rtx-hybrid-electric-demonstrator.html https://www.aerospacetestinginternational.com/news/h55-deliv...
- bilsbie 2mo agoI’d imagine the apu could recharge it during flight at least somewhat.
- bilsbie 2mo ago[dead]
- whazor 2mo agoThis is why it makes sense to carbon price the private jets. On a smaller plane you can innovate much faster.
- aunty_helen 2mo agoLove a gearbox those guys over at P&W. Can't get enough gearboxes.
- whatever1 2mo agoSince they can put a huge battery onboard why don't they also electrify runway taxiing? I cringe every time a jet plane has to spool up, burning god knows how many gallons of fuel, just to go 15mph on the runway.