Electric planes

[swaltner]

Is there a reason nobody's just putting an electric motor and batteries in a conventional helicopter?

It’s all about the batteries.

Sikorsky did just that back in 2010 with the Sikorsky Firefly that they brought to AirVenture. They took a. Sikorsky S-300C, gutted the gas engine and added an electric motor bolted to the original transmission and batteries. They took a 3 person helicopter and made it a single place helicopter with a usable load of something like 125 pounds. Whatever the actual capacity happened to be was chosen because it was the weight of their lightest test pilot.

The Firefly had a flight time of about 12 minutes. It was built to get experience with drive electronics, but was shelved until a more reasonable battery technology came along.

 

[mltv]

https://twitter.com/x/status/1422642702747897864

All these orders for planes that at these phase are concepts at best.

 

[bxr140]

All these orders for planes that at these phase are concepts at best.

Isn't that, like, how planes work?

1. Plane concept gets announced.
2. Some big order(s) gets placed on plane concept.
3. Plane concept spends years being developed and tested.
4. Some time later, actual plane flies.

 

[miimura]

5. Some time later, the plane actually enters commercial service

 

[miimura]

I agree with @daniel above. The poor efficiency comparison between synthetic fuels and battery is not really relevant when batteries can't provide you an aircraft with serviceable payload mass for the desired mission. "wasting" the renewable energy to make a energy dense carbon neutral energy carrier is logical. The fact that it can use existing equipment like storage tanks and jet engines is a huge bonus.

Even for battery regional aircraft like the one mentioned above related to United / Mesa, a highly optimized APU used as a range extender can provide the required energy margin required for diversion, etc. without a huge weight penalty. The vast majority of the time it won't be used, but it can eliminate a huge amount of mass that would otherwise be required to provide a battery energy buffer.

This is the kind of specialized APU/generator that I was thinking of for electric plane range extension. The article describes it as a generator for a hybrid plane.

Rolls-Royce puts 2.5-MW generator for future hybrid aircraft to the test

Rolls-Royce has delivered a 2.5-megawatt electrical generator to its newly-renovated Testbed 108 facility in Bristol, UK for final testing and integration into the world's most powerful hybrid-electric aerospace propulsion system.

newatlas.com

 

[daniel]

It’s all about the batteries.

Sikorsky did just that back in 2010 with the Sikorsky Firefly that they brought to AirVenture. They took a. Sikorsky S-300C, gutted the gas engine and added an electric motor bolted to the original transmission and batteries. They took a 3 person helicopter and made it a single place helicopter with a usable load of something like 125 pounds. Whatever the actual capacity happened to be was chosen because it was the weight of their lightest test pilot.

The Firefly had a flight time of about 12 minutes. It was built to get experience with drive electronics, but was shelved until a more reasonable battery technology came along.

But is a quad-copter so much more efficient than a conventional helicopter that the same motor & batteries will give the quad-copter more lift & range?

A helicopter has a large, slower-turning rotor which, in addition, is capable of autorotation. A quad- or octo-copter has what are basically propellers, faster-turning and incapable of auto-rotation. OTOH, a quad(octo)-copter does not need the tail extension or tail rotor. Does any of this make the quad-copter an inherently better design than the conventional helicopter? Is it maybe more amenable to computer control?

Back on the farm we used to say "If it ain't broke, don't fix it."

 

[mycroftxxx]

But is a quad-copter so much more efficient than a conventional helicopter that the same motor & batteries will give the quad-copter more lift & range?

A helicopter has a large, slower-turning rotor which, in addition, is capable of autorotation. A quad- or octo-copter has what are basically propellers, faster-turning and incapable of auto-rotation. OTOH, a quad(octo)-copter does not need the tail extension or tail rotor. Does any of this make the quad-copter an inherently better design than the conventional helicopter? Is it maybe more amenable to computer control?

Back on the farm we used to say "If it ain't broke, don't fix it."

Quadcopters and the like are relatively simple to control; the rotors are fixed pitch, relatively small, with rigid blades - you control each rotor’s thrust directly by varying its motor speed; make the back rotor spin faster than the front rotor and the vehicle tilts nose-down, providing a component of thrust in the horizontal plane to propel the vehicle forward; similar tricks give you backwards or side to side flight. But small fixed pitch rotors are very inefficient; the concept doesn’t scale up well.

A helicopter almost always has a fixed speed rotor, and the thrust produced by the rotor is created by changing the pitch of the rotor blades using a sophisticated mechanical linkage; this is called collective pitch. If that linkage can also change each blades’s pitch in a cyclic fashion as the blade rotates around, you can make the thrust vector generated by the rotor point forwards, backwards, side to side, and cause the helicopter to move in different directions. This requires even more sophisticated linkages, pivots, etc., in the rotor system, but is drastically more efficient aerodynamically than the fixed-pitch quadcopter; there are usually other advantages such as being able to autorotate if the engine fails. It is much harder to control than a quadcopter type system though. So once you get above a few hundred pounds of weight, a conventional helicopter configuration is usually worth the extra complexity. (I’ve ignored a host of practical considerations in the interest of not turning this into a book.)

Many of the “urban air mobility“ concepts mix fixed-pitch vertical lift systems for vertical takeoff and landing, with fixed wing lift systems for cruising flight. We’ll see how well these concepts work; for the short range UAM market concepts it may work. The big issue with UAM is FAA certification that allows operators to use them as these flitting everywhere aircraft; if the FAA puts significant restrictions on what they can do and where they can go, the market for them will never take off

 

[daniel]

Okay. So: Quad-copter is simpler to design and construct, easier to control. Conventional helicopter is much more complicated to design, build, and maintain, much more difficult to control, but more efficient, able to lift greater weight, and safer if there's a failure.

So the quad-copter is the choice for a personal aircraft intended for use by non-pilots (a recipe for disaster in itself). It's more of a toy, so doesn't need a long flight time/distance.

Conventional helicopter is the easy choice for commercial uses of any sort.

So the answer to my question of why they don't build an electric helicopter is that batteries are still too heavy for commercial use and conventional helicopters are too difficult to fly for the hobby market. Does that about sum it up?

 

[mltv]

Litigation is not the way to start a new aviation segment. Wisk sue Archer, now Archer sue Wisk.

Archer Aviation is seeking $1B in damages from Wisk Aero as legal dispute escalates | TechCrunch

Archer Aviation is seeking $1 billion in damages from Wisk Aero, according to court filings Tuesday, significantly escalating the ongoing legal battle

techcrunch.com

Mean while Joby (JOBY) SPAC merger IPO with +33.6% sp pop.

 

[watsongrg]

There are a variety of reasons only turbine powered aircraft are operating at the flight-levels altitudes that modern airliners travels at today. Airplanes are subjected to temperature and air pressure extremes that automobile are not.

Temperture and air density at the smooth flight levels are at an extreme that most passengers don’t grasp nor appreciate.
Its about -40c (or F) Outside that comfy airliner! Lithium batteries lose energy density with decrease in temp. The typical electric car can lose 30-50% of its range at a mere 0c or 32F. How’s that gonna work for an airliner when it’s -40c outside? Everyone knows frozen lithium batteries are a big no-no. Even jet fuel has an additive that keeps it from freezing. So, what’s the plan for keeping those batteries warm?

Now let’s talk air pressure. Surely you know the only reason you can fly around in a jet airliner, with no supplemental oxygen mask, is because the plane is pressurized. And that pressurization comes from the compressor of that jet / turbine engine. Without pressurization passengers would be unconscious, and subsequently dead, in just a few seconds to minutes , at the cruising altitude of a modern jet, without supplemental oxygen. So, whats the plan for pressurizing an electric airliner ?

Even the propeller driven commuter airplanes you may still fly short trips on are powered by a turbine/jet engine. And everyone hates those prop planes because they are noisy and fly at the bumpy lower altitudes. And it’s cold and requires pressurization also.

Modern air travel has reached such a level of extreme efficiency and reliability that the average passenger doesn’t truly appreciate what is being achieved every time they take flight into the skys

 

[JRP3]

1. The passenger compartment is heated and insulated, no reason the batteries wouldn't be as well. Plus the cells generate heat internally while discharging and charging so there is little chance for them to get cold. While on the ground and plugged in the packs would be well heated.
2. Obviously there would be an electric compressor keeping the cabin pressurized.
3. No one is talking about building electric airliners anytime soon, battery technology will need significant advancements to achieve that.

 

[daniel]

2. Obviously there would be an electric compressor keeping the cabin pressurized.

At the cost of additional power. The high energy density of jet fuel can easily give away a bit of power to compress the cabin air. With batteries, that's a significant reduction in range.

A jetliner needs to constantly bring in fresh air from outside. That air must be heated as well as compressed. We all know how much range an electric car loses when you run the cabin heater. At 0C you can dress really warmly if you must, to conserve range. At -40 (C or F) you cannot. You need to heat the air. An electric jet would lose even more range from heating the air.

3. No one is talking about building electric airliners anytime soon, battery technology will need significant advancements to achieve that.

Batteries are never going to rival the energy density by weight of liquid hydrocarbons. The best way to power an airplane with electricity is to use that electricity to create synthetic fuels. The energy loss from the process of making the synfuels will be nowhere near the energy cost of carrying batteries on a long-haul jetliner.

 

[JRP3]

Batteries are never going to rival the energy density by weight of liquid hydrocarbons.

They never need to when you consider the 95% efficiency of electric motors compared to 50% of jet motors.

 

[daniel]

They never need to when you consider the 95% efficiency of electric motors compared to 50% of jet motors.

They just have to reach 50% of the energy density of jet fuel. Where are they now? 1%?

Some quick googling: Lithium batteries have 50 to 260 Wh/kg. Jet fuel has 9.6 kWh/L. A liter of jet fuel weighs .81 kg. I think that comes out to just under 12 kWh/kg, so taking the higher value for lithium batteries of 260 Wh/kg, the battery is at a little more than 2% the energy density by weight of jet fuel.

Then factor in that heat is a waste product of the turbine, whereas the battery-plane needs to use battery for heating, and that the battery retains its full weight for the entire flight while the turbine consumes fuel making the plane lighter as it flies, and you're probably back down to 1% for the battery.

I predict that batteries will never reach 50% of the energy density of jet fuel. But once we have sufficient green energy on line we can make synthetic jet fuel using atmospheric carbon, burn that in existing jets, which will be carbon neutral because they just return to the atmosphere the CO2 that was removed from the atmosphere to make the synthetic jet fuel.

Batteries are the clear choice for cars because weight is not a significant issue. Synfuels are the clear choice for airplanes because weight is a critical issue.

Increase the energy density of batteries four-fold to 1 kWh/kg and you're still only around 8% the energy of jet fuel, and you still have the need for heat from the battery, and the fact that jet fuel disappears as the plane flies.

 

[Etna]

There are a variety of reasons only turbine powered aircraft are operating at the flight-levels altitudes that modern airliners travels at today. Airplanes are subjected to temperature and air pressure extremes that automobile are not.

Temperture and air density at the smooth flight levels are at an extreme that most passengers don’t grasp nor appreciate.
Its about -40c (or F) Outside that comfy airliner! Lithium batteries lose energy density with decrease in temp. The typical electric car can lose 30-50% of its range at a mere 0c or 32F. How’s that gonna work for an airliner when it’s -40c outside? Everyone knows frozen lithium batteries are a big no-no. Even jet fuel has an additive that keeps it from freezing. So, what’s the plan for keeping those batteries warm?

Now let’s talk air pressure. Surely you know the only reason you can fly around in a jet airliner, with no supplemental oxygen mask, is because the plane is pressurized. And that pressurization comes from the compressor of that jet / turbine engine. Without pressurization passengers would be unconscious, and subsequently dead, in just a few seconds to minutes , at the cruising altitude of a modern jet, without supplemental oxygen. So, whats the plan for pressurizing an electric airliner ?

Even the propeller driven commuter airplanes you may still fly short trips on are powered by a turbine/jet engine. And everyone hates those prop planes because they are noisy and fly at the bumpy lower altitudes. And it’s cold and requires pressurization also.

Modern air travel has reached such a level of extreme efficiency and reliability that the average passenger doesn’t truly appreciate what is being achieved every time they take flight into the skys

During high altitude cruise the batteries must be cooled rather than warmed up. Even at -40C, because they are not really "outside" but generally inside a composites fairing of some sorts.
Typically 10% of power generated is lost as heat, for example on a PC12 you'll cruise at least at 400kW so that's 40 kW you need to reject somehow - that's a lot of heat! The descent is dealt with mostly by using the battery as heat sink.
Pressurization certainly requires a lot of power, on the order of 1 kW per passenger, but the aircraft systems still represent a small percentage of propulsion energy. Typically in the single digits %. The plan for pressurizing an electric airliner is similar to the Boeing 787, with pressurization provided by an electric ECS rather than bleed air.
Having said that, batteries will constrain electric aircraft to short distances for awhile, not giving enough time to climb very high.

 

[JRP3]

Air One personal EVTOL

Meet the Air One, the New Two-Person eVTOL You Can Park in Your Garage

Aviation startup Air has just unveiled a two-person eVTOL designed for recreation. It has a top speed of 55 mph and a range of 110 miles.

robbreport.com

 

[daniel]

Air One personal EVTOL

Meet the Air One, the New Two-Person eVTOL You Can Park in Your Garage

Aviation startup Air has just unveiled a two-person eVTOL designed for recreation. It has a top speed of 55 mph and a range of 110 miles.

robbreport.com

You can't actually buy one. It needs to be certified. IOW we have only the company's word that it's safe. Note also that the company claims it's "buy and fly" but the article notes that you'll need a license to fly it. IOW it's not "buy and fly" at all. One article said they "expect" it will be the price of "an expensive car," so I'm guessing $200,000. And when reality pokes its head in, probably $300K to $500K.

So, just one more in a very long list of vaporware companies bilking investors out of money for R&D so the owners can pay themselves a salary while having fun tinkering with something that no rational city council would ever allow untrained pilots to fly over occupied homes.

You can buy a helicopter today, and you can learn to fly it. You probably won't be allowed to land it at an urban home. So being able to park a plane in your garage is kind of a useless feature.

 

[JRP3]

It is supposed to comply with FAR 103 Amphibious Ultralight category.

He was talking about the Air One that I linked, I didn't think it was Amphibious.

 

[SalisburySam]

You probably won't be allowed to land it at an urban home. So being able to park a plane in your garage is kind of a useless feature.

See Spruce Creek, Florida.

 

[lolachampcar]

See Spruce Creek, Florida.

or any other airpark in the US