EITML5 helicopters
Posted by ohheychris@reddit | aviation | View on Reddit | 21 comments
Is there anyway to eliminate more moving parts? Like how can engineers create, invent, or remove parts to make helicopters less maintenance I guess.
I’m just genuinely curious. Have we reached peak performance with the aircraft?
quietflyr@reddit
Probably hybrid electric propulsion is the next way to reduce complexity. If you could have a direct-drive main rotor system that would eliminate a whole lot of complex failure-prone components. Plus if you kept enough juice for maybe 5 minutes of cruise flight you would dramatically reduce the hazards associated with engine failure.
Maybe some kind of electronically controlled actuators mounted on the rotating system to eliminate the swashplate? Questionable whether that would help things that much.
vortex_ring_state@reddit
Already there.....https://avweb.com/aviation-news/bell-continues-development-of-electric-tail-rotors/
quietflyr@reddit
I'm familiar with it. I know a bunch of the team that worked on it.
But that's just electric tail rotors. I'm talking about main rotor. If you electrify that you get rid of the main gearbox and most of the associated failure modes.
BoringBob84@reddit
And you introduce a whole bunch of new failure modes. Often times, we can inspect mechanical parts and predict that they will soon fail. We don't get those warnings from electrical parts.
I am not saying that there is not a future in electric propulsion - just that it must be carefully designed.
quietflyr@reddit
Electric motors are very reliable, being as they only have one moving part, save for a couple bearings, versus a main gearbox with hundreds of moving parts.
Yes there are failure modes with electric propulsion, but there are so many with gearboxes. Plus gearboxes require very expensive overhauls periodically, where an electric motor rebuild would be much less expensive owing to massively lower person hour requirements.
devildog2067@reddit
Most industrial AC electric motors basically have two failure modes (bearings and shorts in the windings). Only one of those involves a moving part and is easy to inspect for. The other is usually a surprise.
DC motors have the additional failure modes associated with brushes and commutators.
Like u/BoringBob84 says, electric motors eliminate many failure modes but introduce others. We have many decades of accumulated experience finding out what tends to break on helicopters. We’d have to re-learn those lessons with electric helicopters. I’m not saying it isn’t worth doing (though I will say with current battery tech it’s utterly unviable) but there will be a cost in lives and it’s you should not be glib or cavalier about it.
quietflyr@reddit
OK I'll just put my 20+ years of aerospace engineering experience (most of it on helicopters) aside because you think I'm being glib or cavalier.
devildog2067@reddit
How much experience do you have with electric motors? I’ve only been working in the field for about as long as you, but what do I know?
Electric motors sometimes just stop working. Inspections often don’t catch impending failures. There would have to be an electric motor equivalent of LLP, and figuring it out would be hard, expensive, and costly in terms of safety and lives.
Would the resulting mature technology ultimately be enough safer to justify that cost? Maybe. Probably, even. Helicopters are horrifically complex. But it’d still have to be paid.
And regardless, it’s entirely moot until batteries with enough energy density to sustain flight make such investment of effort and dollars viable, and we’re decades away from that.
quietflyr@reddit
So your electric motor experience isn't in aviation, is it?
There are reliability requirements which would have to be met before such a system could enter service. An OEM would have to prove that their system is sufficiently reliable, and there are many ways to achieve that reliability. But if it can't be shown to be that reliable, it won't fly.
I never said such a system is ready right now, just that it's probably the direction to go for greater reliability and reduced parts counts.
As for cost, a main gearbox for a Bell 412 costs about a million bucks on its own, and needs to be overhauled every 3000 flying hours IIRC, for a cost of many hundreds of thousands of dollars each time. Plus oil changes and other preventative maintenance in between. I think it's pretty likely an electric replacement could be operated within that price range.
Also I specifically called out hybrid electric propulsion, not battery electric propulsion. Battery capacity for 5 minutes flying time on our current technology would not be excessive, considering it wouldn't need to be at full power. It would only need to be enough to give a better landing site selection for an emergency landing, and allow the aircraft to land under power rather than rely on autorotation.
devildog2067@reddit
Quite a lot of it is, actually — I was an advisor to the HorizonX team that looked at both Joby and Wisk, in part due to my experience in aviation (I’m not super deep in aerostructures but I know quite a lot about engine maintenance) and in part due to my experience with electric motors. Won’t go into more detail than that, save to say I’m not an engineer and I never claimed to be. I trained as a physicist (PhD) and mostly worked on the business side.
All I said — which you have yet to refute — is that changing propulsion technology introduces new kinds of failure modes. It’s true that there will be fewer moving parts with an electric motor, and it’s probably true that the system reliability will overall be higher as a result. But we don’t know that, and without extensive testing — which costs money — we can’t know.
The reality is that no one is investing behind this kind of technological change, because no one is asking for it. For as terrible as helicopters are at flying, they’re good enough and we know how they work. We’ve bought that experience by flying them for decades and decades, figuring out what makes them crash when they crash, and re-engineering the systems that break. Helicopters are mature technology. Turbine engines are mature technology. No one is looking to change them in their existing form factors.
And that I think is ultimately where your train of thought takes you. If you’re going to re-engineer a VTOL platform with a new propulsion technology, why make it look like a helicopter at all? The helicopter is a product of design compromises and limitations driven by the technology of the time. If you’re going to start over, you rapidly conclude that you might as well start all the way over — that’s why all the eVTOL aircraft have multi-rotor/tiltrotor/quadcopter-ish designs and do away with the tail rotor. If you’re going to do electric motors, you can (as you note) do away with gearboxes entirely — which then gives you a lot more freedom where to put the rotors. You can make the rotors spin in opposite directions, eliminating the need for the parasitic power loss of a tail rotor (which is basically entirely wasted).
If anyone thought electric powered helicopters were a good idea, they’d have started a company to try and build them. Lord knows that people have started dumber companies to build dumber things. No one is going down this path because it’s fundamentally not a good idea.
quietflyr@reddit
eVTOLs generally have very different design and mission requirements than many helicopters, but I do agree configurations will change based on electric propulsion.
That said...
https://www.aerospacetestinginternational.com/news/airbus-helicopters-to-test-collins-hybrid-electric-propulsion.html
Does Airbus count as "someone going down that path"?
devildog2067@reddit
Airbus invested in two hydrogen powered aircraft startups too, and those aren’t a thing. There’s a difference between “building prototypes” and “building an actual production-scale product”.
FWIW, the prototype you linked to keeps the gearboxes… this is more like the equivalent of a diesel-electric train version of a helicopter, than an actual electric helicopter.
quietflyr@reddit
You know what comes before a production scale prototype? A testbed or technology demonstrator. Quit moving the goalposts.
And for the 100th time, I never proposed an electric helicopter. I proposed a hybrid electric drivetrain, which is basically using turbines for electricity generation and rotor drive coming from electric motor(s).
That's basically what this is.
devildog2067@reddit
> If you could have a direct-drive main rotor system
> You get rid of the main gearbox
Your whole point was that eliminating the gearbox eliminates many of the mechanical failure modes, yet:
>PioneerLab’s existing engines are to be swapped for a hybrid-electric propulsion system comprised of a Pratt & Whitney Canada PW210 engine derivative linked with two Collins Aerospace 250 kW electric motors and controllers through a common gearbox.
This is an entirely different thing than you started out talking about. The electric motors drive the gearboxes. It’s not a direct-drive main rotor system.
BoringBob84@reddit
I agree that electric motors are very reliable, if they are designed and operated correctly. However, an electric propulsion system requires complex motor controllers with power electronics, microprocessors, software, and communications buses. All of that equipment has failure modes and requires redundancy for critical systems. And the incredible amount of energy density required for helicopters makes battery technology another major challenge.
As engineers, we are not in the business of saying that anything is impossible, but many things are more difficult than they look, and they are not always economically feasible, even when they are technically feasible.
quietflyr@reddit
... Which is common for many systems on aircraft, and is something we already know how to do. 10^-9 has been required of such systems for many decades, and we achieve it all the time.
Again, I'm not talking about a battery electric helicopter, I'm talking about hybrid electric, with a 5 minute partial power backup. Should be very achievable.
SheepherderAware4766@reddit
Yes, electric motors have great reliability, however, it doesn't display failure signs. For a gearbox, I could pull a gear out and run CT scans and metallurgy to check for for stress fractures. I can't do that for software failures.
A maintenance technician doesn't care about the average time until failure of the model, he cares about the individual time to failure of the machine in front of him.
quietflyr@reddit
Cool. You could have said the same thing about flight controls and fly by wire. But here we are with most modern commercial aircraft being fly by wire, and flight control system failures less likely than ever.
But yes, there are system reliability issues that need to be developed and addressed. 10^-9 is still a requirement before this could go into service on a Part 29 helicopter. This is mostly why it's not in service already.
Late-Mathematician55@reddit
I just read about an account of "helicopter-induced lightning", which caused a Sikorsky S-76, cruising at 4000ft, had been stuck by lightning that its own airframe had created, and dropped 3144ft before the crew could regain control .
Now I'm even more scared of flying in them.
https://www.tsb.gc.ca/eng/medias-media/communiques/aviation/2026/a23p0136-20260513.html
BoringBob84@reddit
Electricity is lazy. If it wants to get from point A to point B, then a huge chunk of aluminum is a much easier path than air. Thus, aircraft and rotorcraft are frequent "shortcuts" for static charge in the atmosphere and are designed accordingly.
Depending on the criticality of the system to flight, it either has to "ride through" lightning strikes unaffected, it can be momentarily interrupted during and after a lightning strike, or it can be disabled by a lightning strike.
Those are safety regulations. However, from an economic perspective, few customers would tolerate their non-essential passenger entertainment systems being repeatedly destroyed by lightning strikes, so even non-critical systems have to be somewhat robust.
Inspi@reddit
Probably fewer parts in the airframe (Bell H-13) but probably not much in the engine.