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Hybrid or electric theory?

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Vigilant1

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Back on topic, the viable near-term use I see for hybrid power in aircraft is applications where you need some multiple of cruise power (big multiples, like 2-3x or more) for very short periods. Think electric VTOL that transitions to wingborne flight for cruise.
What I see very often, though, is proponents breezily making assumptions that place very strict (unacceptable?) constraints on how the power system will be used. "Then, after takeoff, the batteries will be recharged in cruise flight" etc. To my mind, normal (non-emergency) ops in a powered airplane shouldn't include any approach/landing without the ability to execute a missed approach/go-around. So, if we need to fly for 20 minutes to recharge the batteries, we can't do a safe, normal landing in that window. Can't go beat up the pattern and get 10 landings in an hour. A precautionary landing within the first 20 minutes becomes more than just an inconvenience, etc. A "normal" IC powerplant provides a lot of flexibility: 100% power until the last drop of fuel is used.
 
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blane.c

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What pilots must know to determine the Carson Speed for any piston airplane is its best-glide speed, or VG. Add 32 percent to that, and that’s the Carson Speed. Flying at the Carson Speed is an aerodynamic bargain because it represents a 32-percent airspeed increase (over VG) yet fuel consumption rises just 16 percent.

 

blane.c

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What I see very often, though, is proponents breezily making assumptions that place very strict (unacceptable?) constraints on how the power system will be used. "Then, after takeoff, the batteries will be recharged in cruise flight" etc. To my mind, normal (non-emergency) ops in a powered airplane shouldn't include any approach/landing without the ability to execute a missed approach/go-around. So, if we need to fly for 20 minutes to recharge the batteries, we can't do a safe, normal landing in that window. Can't go beat up the pattern and get 10 landings in an hour. A precautionary landing within the first 20 minutes becomes more than just an inconvenience, etc. A "normal" IC powerplant provides a lot of flexibility: 100% power until the last drop of fuel is used.
We routinely landed at airports were you at some point during the approach were committed to land (one way or another) and for example one time when I did have to go around at a normal airport I could have just side/slipped around the 150 sitting on the runway and landed in the remaining except of course for all the explaining I would have had to go through afterwards. Another time a crew whos aircraft had at this juncture had been on fire for what must have seemed for them forever elected to go around because a atv was on the runway, there wing folded subsequent in the pattern, hind sight being 20-20 they would have been better off (likely) to have landed over the atv and taken the crash at a much reduced speed in the over run. I am not a big fan of the missed approach mentality as it is currently accepted in mainstream aviation, speaking personally if you are on the runway and I want to land ... you had better duck.
 

Vigilant1

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We routinely landed at airports were you at some point during the approach were committed to land (one way or another) and for example one time when I did have to go around at a normal airport I could have just side/slipped around the 150 sitting on the runway and landed in the remaining except of course for all the explaining I would have had to go through afterwards. Another time a crew whos aircraft had at this juncture had been on fire for what must have seemed for them forever elected to go around because a atv was on the runway, there wing folded subsequent in the pattern, hind sight being 20-20 they would have been better off (likely) to have landed over the atv and taken the crash at a much reduced speed in the over run. I am not a big fan of the missed approach mentality as it is currently accepted in mainstream aviation, speaking personally if you are on the runway and I want to land ... you had better duck.
I'm sure you aren't saying that aviation is safer or better if we don't have the option to go around.
 

blane.c

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It is that with electric it may end up being more like a glider than a conventional airplane, and the prevalent direction in actuality that it is taking in general aviation is for either ultralight or self launch/sustainer glider applications so especially with glider the go-around option has never been much of a reality to begin with. The trainer aircraft (electric) that I have read articles about seem to have about an hour of flight, well to take out a student and do a lesson and spend a couple extra minutes on something in a normal powered aircraft is routine and for that not to carry over to some extent in an electric is going to require strong discipline coupled with the fact that batteries don't get better with age it is likely that a go around may in fact not be the best option.
 

blane.c

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If someone takes the runway they should take-off. If they have a problem and there are landing aircraft they should get off the runway and deal with it. If a toddler toddles out to the middle of the runway and I choose to land over the toddler and crash in the over-run because it is a better option in my opinion than crashing off-airport that is my elective as long as of course the toddler remains untouched. Same if an aircraft is disabled in the middle of the runway. I do not have the mentality that I have to do a go-around for me it is an option.
 

Hot Wings

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The trainer aircraft (electric) that I have read articles about seem to have about an hour of flight,
I agree that for this application your notice of potential hazard due to reduced options is probably one that needs to be considered by each operator. With pure electric just planning on landing with enough battery reserve to do a couple of go arounds seems prudent.
Adding an ICE does complicate the problem, especially if the ICE isn't capable of minimum climb with a low battery.

When I've modeled hybrid flight I've always considered the need to return to the take off point from any position in the climb phase due to ICE failure. I'd never considered a having to do a go around with only half of the system being operative. Will add that to my spread sheets next time I play with this.

Total hybrid system failure probably neds to be considered with the same thinking as an ICE total failure?
 

Vigilant1

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Fuel management is already a factor in 55% of general aviation accidents. I wonder how the numbers will look if pilots have two separate fuel 'tanks", "fuel" can only flow one way between them, and only slowly (below the consumption rate) and when an engine is running. And, each "fuel tank" is dedicated to a particular powerplant which is mission-critical in a different phase of flight. Nope, I can't see any potential problems with that...
 
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blane.c

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I am not sure why maybe it is that some people have been taught that participation makes us all winners but some people seem to me now to believe that they are entitled to the aircraft engine running.
 

cblink.007

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We have been researching hybrid aircraft propulsion for some time. We think a parallel planform, such as seen in a hybrid car, would work (ie three modes of power to the prop; ICE only (with batt charging), Elec Only, ICE-Elec "max power mode", but maybe not the ultimate solution. We think the ticket is in elec-only driving the prop, with a 'range extension' ICE motor. The battery technology is on the threshold of making this possible...and affordable. We want to do this; our Shrike aircraft platform would make an ideal test mule for the technology!

Obviously, the performance (ie, useful load, range, endurance) and price MUST be on par with a comparable ICE only aircraft, and more importantly, it must reduce operational costs in order to make it successful. The era is approaching, whether we like it or not, and I think our community will play a significant part in achieving and advancing the state of the art!

As the Mandalorian says, this is the way!
 

cblink.007

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I am not sure why maybe it is that some people have been taught that participation makes us all winners but some people seem to me now to believe that they are entitled to the aircraft engine running.
Aviation Quote of the Generation!
 

BBerson

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three modes of power to the prop; ICE only (with batt charging), Elec Only, ICE-Elec "max power mode",
So then the pilot has the option to use either power-plant one or power-plant two or both.
How is that different from using two ICE power plants, with the option to use ICE power plant one or ICE power plant two or both?
 

Vigilant1

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....(ie three modes of power to the prop; ICE only (with batt charging), Elec Only, ICE-Elec "max power mode"....
"the prop" ? So there's a single transmission and/or clutches through which the ICE and electric motors can turn the prop? And your goal is that the price won't be higher than ICE alone? Even with some very rosy guesses about how low the operating costs will be, this will be quite something to see.
 

cblink.007

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So then the pilot has the option to use either power-plant one or power-plant two or both.
How is that different from using two ICE power plants, with the option to use ICE power plant one or ICE power plant two or both?
No, the intent would have been computer control, with drive output based on power demand and flight conditions. To have a manual control only would be inefficient...but should absolutely be available to the pilot for the sake of emergency procedures.

"the prop" ? So there's a single transmission and/or clutches through which the ICE and electric motors can turn the prop? And your goal is that the price won't be higher than ICE alone? Even with some very rosy guesses about how low the operating costs will be, this will be quite something to see.
Okay, relax, my friend. 1. Review the theory of operation of a parallel vs series hybrid drive systems; a parallel system (like a Toyota Prius) would require a combining gearbox, while with a series system (like a Chevrolet Volt), the prop would be driven by the electric motor only. 2. It is extraordinarily naive to think that a hybrid system would cost the same, or even cheaper than a current ICE system at present. Not a chance! The state of the art simply doesn't make the economic case for it yet. A prototype system would be very expensive (hence the reason why we are not developing one at present). My point was that in order for a hybrid system for an aircraft to be practical and successful in the marketplace, it would need to be affordable up front, and cheaper in the long run over the current powerplants. Given the current state of the art, the risks are high, and as a consequence, so will the development costs of such a system.

At the end of the day my group knows its limitations; we do not possess the resources to develop a hybrid powertrain like this yet, even though we have been enjoying a very successful Yamaha Apex conversion project so far; first dyno runs this week!
 

Vigilant1

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Okay, relax, my friend. 1. Review the theory of operation of a parallel vs series hybrid drive systems; a parallel system (like a Toyota Prius) would require a combining gearbox, while with a series system (like a Chevrolet Volt), the prop would be driven by the electric motor only.
Thanks for your concern. I am relaxed and understand the distinction between a parallel and series hybrid. Your proposed power system is a parallel hybrid model
(ICE only (with batt charging), Elec Only, ICE-Elec "max power mode")
, and so will require a common transmission for everything.

2. It is extraordinarily naive to think that a hybrid system would cost the same, or even cheaper than a current ICE system at present. Not a chance!
I agree 100%.

Best of luck with the Yamaha.
 

cblink.007

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Thanks for your concern. I am relaxed and understand the distinction between a parallel and series hybrid. Your proposed power system is a parallel hybrid model , and so will require a common transmission for everything.


I agree 100%.

Best of luck with the Yamaha.
All good. The conversion has been stupid simple (after the rebuild). Literally just bolt the SkyTrax PSRU on! This motor could be a candidate ICE base for a parallel hybrid plant, for what it is worth. We will be running a Sensenich ground adjustable prop; we have been taking a real close look at incorporating a brake that can stop the prop in the event of engine failure, but that'll be for down the road. We are looking forward to cataloging the vibe spectrum for the whole system; it will help the Yamaha conversion community IMHO!
 

Traskel

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I have a love-hate relationship with physics-related puzzlers; the obvious answer is often the wrong one. I also enjoy any discussion that includes the word 'never', particularly when looking back on it from a later date (when I'm *not* the one who used the word).

It's obvious to everyone that converting repeatedly among various energy types costs efficiency, and it seems obvious that any system that does that will be less efficient than one that doesn't.

Anyone know the most energy-efficient way to transport mass designed by man? Prize is 15 seconds of HBA fame.

Charlie
Drop it from an airplane...
 
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