Electric Power Plants

[KJ Hamblin]

Well then my apologies. I will admit that I am not well versed in aviation or marine engines yet. With the 1HP will always be 1HP, all I was meaning to say is along the lines of 1 meter is exactly equal to 1 meter. 1 inch is exactly equal to 1 inch. 1 watt is exactly equal to 1 watt and so on. That was in reference to Matt's "The equations don't care what is producing the power." It was a reference to the units used in equations.

[f_lunn@yahoo.com]

Now don't quote me on this because it is coming from memory, but I believe the HP rating for a combustion engine and electric motor are specified differently. I believe an electric motor is rated on the amount of continuous power it can deliver while a combustion engine is rated by the peak power it can deliver. That difference is very important.

So if you need a 200HP combustion engine to make your aircraft fly, an electric motor that will give you the same performance will have an HP rating lower than 200HP. Really you have to get into the mathematics of the whole system. You need to figure out the amount of thrust you need that will result in the airspeed you need to produce the amount of lift you need to get the payload(aircraft+people+stuff) in the air.

Once you have that thrust you can calculate how fast the propeller needs to spin(RPM) to produce that thrust, then check the datasheet of the electric motor to get an estimate of the current draw at the calculated RPM and a given voltage. Expect the actual current draw to be 10-20% more.

What are you thinking about doing f_lunn? I'm an electrical engineer and pilot, so I like where you seem to be heading.

KJ,
I was intrigued with the " FlyNano" on pg 32 of the July issue of SportAviation. This 155 lb flying jet ski sounds far fetched--but I wouldn't mind building a more conventional amphib with electric power. I live on a lake and fly a trike Tundra. I could put floats on it, but I'm sensitive to the noise. My wife and I do not like the one jet ski on the lake and know the neighbors and the loons don't like it either.
Sounds like the batteries will significantly increase the weight of the FlyNno !

[Ron Blum]

IMO, all of you are correct. Power is power, and it doesn't matter what is driving the prop. With that said, though, the prop is still the limiting factor. Also, many people claim that electric motors are much better because they produce max torque at "zero" RPM. This is great for ground transportation (cars, busses, tractors, etc.), but it doesn't matter in an airplane. Here's why. The prop still produces thrust based on its RPM (... and forward flight speed, (variable) pitch and cross-section). At zero RPM a propeller produces zero thrust. The huge advantage that airplanes have over cars is that they operate at a constant RPM for the vast majority of time ... and the variation can be 'slow' (per the regs, jet engines need to produce takeoff thrust in <8 seconds (props are better at <~5 seconds)). This would be an eternity in a car.

One small clarifying point on horsepower ratings, though. Airplane engines are certified to run at maximum power for 5 minutes/flight and 75% thereafter. "Typical" electric motors run at their rated power for a few seconds and 50% thereafter. Car engines rarely run at rated horsepower and at interstate cruise speeds use about 12 horsepower (squat compared to an airplane). Bottom line: Airplanes require a lot of power. -Ron

[steveinindy]

...and before anybody gets excited, that's a 20 kW-hour battery. That's a big battery. With current Li-po battery technology, that's 220 lbs of batteries. For only 27HP.

Yeah, welcome to why most of us (over the age of 30) will never see anything bigger than a small LSA powered by electric motors in our lifetimes. All of this effort and money are being spent on the aviation equivalent of a sideshow attraction.

[Ron Blum]

I agree with the battery size issue, but who says it has to be batteries? There are really big companies working on this issue: Boeing, Sikorsky, GE Aviation, Honda, Toyota, GM, the government, etc. On top of all that, there are a lot of venture capitalists pouring money into this new industry. How long did it take the world to go from the Wrights' 12 Hp motor to the jet engine? Looking back, it wasn't very long. This could very well be the next generation.

PS. I am over 30, but know that i will see practical electric airplanes in my time.

[steveinindy]

but know that i will see practical electric airplanes in my time.

Define "practical". To me a two-seat LSA that cruises at less than 130 kts is not very practical for anything other than bug smashing (which I enjoy, don't get me wrong). I just think we are differing on our definition of practical here.

[Ron Blum]

My definition of "practical" is "useful", and LSAs that fly at 130 KCAS are defined as "illegal". There are several thousands of C150/172, Cub, Ercoupe, Piper and Beech pilots/owners that would love to see 130 KCAS (that also use their airplanes for business). The stuff that the big boys are working on (in addition to electric propulsion for transport category airplanes) could very well be enough power for a Bonanza, C210 or etc.

As a perfect example, Boeing spent A LOT of money putting an electric motor in a Diamond (motorglider). The hydrogen fuel cell alone was over $1M. Also look at Boeing's "N+3" and "SUGAR" programs. Sikorsky has also put a lot of research into their electric helicopter, "FireFly". Boeing's research won't lead to them building an electric 172 (they are actually looking at APU type appliances), but it could shed technology that allows someone else to produce one.

We are often limited by our own lack of imagination.

[f_lunn@yahoo.com]

Well, I should have finished reading the July issue of SportAviation before posting this thread--on pg. 90 is an article titled " Practical Electric Airplanes" by Peter Lert. He answers most of my questions. Also, he agrees with Ron and believes electric airplanes will reach "parity" with gasoline in 5 years and "perhaps surpass them" in 10 yrs. Very informative article.

[steveinindy]

Eh....it's not a lack of imagination on my part. I just find it to be a bit less likely to productive than a lot of other potential courses of research including my own into crash survivability, occupant protection, reduction of risks of post crash fire, etc which is yielding patents and applicable technology in the short term rather than the "Well, maybe we can get this to market sometime around 2025". We haven't seen the billions of dollars poured into electric cars produce a truly viable alternative (the hybrids notwithstanding) and I'm pretty up to speed on a lot of the stuff that Boeing and those guys are up to. It's a lot of talk and speculation at this point planning for something 20-30 years or more down the line most likely by conservative estimates.

I might be focused on what I'm doing, I'm definitely more pragmatic (you might call it pessimistic), but I haven't seen anything approaching a usable design that lives up to the hype once it is actually put in to the testing phases. It's the same problem we see with the flying car concepts (except here we don't have the increased risks associated with that particular operating model). We all get excited and then it turns out that it doesn't work in the "real world" as well as it did on paper. Then those who were enthralled get let down and eventually the cycle starts anew with the next engineer who thinks he has the problem licked and not enough sense to keep from spouting off performance standards to the public before he has the technology (either off the shelf or a test-proven new design) to actually achieve it. That's one reason you'll notice why I never try to get into too specific of detail about the aircraft I am designing. I have a few benchmarks (fuel efficiency, range, speed, inclusion of new safety features like I am working on, etc) picked out that I will discuss publicly but it is because I know the technology is there to do it.

I find the electric propulsion idea interesting, as I do many things (birdwatching, scuba diving, photography, wine, etc) but I maintain sufficient distance to allow myself to glean what is useful but not get so close as to lose my scientific objectivity.

I like problems that can be solved within a reasonable amount of time. I try to follow the advice of James Watson (the bold ones are the ones I feel are pertinent and emphasis is, therefore, my own):

1. Knowing “why” (an idea) is more important than learning “what” (a fact).
2. New ideas usually need new facts.
3. Think like your teachers not your peers.
4. Seek out bright as opposed to popular friends.
5. The sooner you narrow your creative interests, the better.
   
6. Keep your intellectual curiosity broad.
7. Work on Sundays.
8. Exercise when you feel intellectually dull.
9. Have a big objective that makes you feel special.
10. Always have an audience for your creative work.
11. Avoid boring people.
12. Science is highly social.
13. Leave a project or field before it bores you.
14. Choose an objective apparently ahead of its time.
15. Work on problems that take 3-5 years to work out.
    
16. Never be the brightest person in the room.
    
17. Stay connected to intellectual competitors.
18. Work with a teammate who is your intellectual equal.
    
19. Constantly share what you learn.
20. Immediately write-up big discoveries.
    
21. Travel increases your creative prowess.
22. Be the first to tell a good story.
23. Read out-loud what you write.
24. Two obsessions are one too many.
25. Don’t take up golf.
26. Close competitors should publish simultaneously.
27. Schedule as few appointments as possible.
28. Never dye your hair or use collagen.

Likewise, I have "rules" posted for my research and those who work with me. This is geared towards the day I am a professor and have a formal "lab" but bear with me:

1. If you utter the word “accident”, you have to put a quarter in the jar. The proper term is "crash".
2. Breakthrough ideas often come to prepared minds that have all the facts, but are unfocussed and even bored with what they are doing at the time.
3. If you think you have a better idea, let’s hear it.
4. Don’t address Steve as “Dr. ________” unless you want something. (NOTE: At the moment, I don't have my doctorate yet so it doesn't matter one way or the other)
5. It helps to have top cover when you are fighting entrenched opposition.
6. Good scientists need to be multi-skilled.
7. The quickest way to get kicked out of this lab is to lose your desire to learn.
8. Sometimes you can’t tell the authorities what you are actually doing because the authorities need deniability.
9. In transmitting new ideas, face to face contact is usually the only effective way
10. Always put in a provisional patent before you publish anything.
11. Be nice until it is time not to be nice.

LSAs that fly at 130 KCAS are defined as "illegal".

Wow...I knew they were slow but dang. All the more reason why I've never understood the fixation some folks have with the new generation of aircraft geared towards that market. If I want to putter around, I'll be more than happy to get an Aeronca or a vintage Cub (which I plan on doing anyhow). I guess my mindset is more towards "Point A" to "Point B" rather than what transpires (beyond the safety and cost aspects) between the two.

[Ron Blum]

Now, for the real kicker ... reality. For the majority of the EAA crowd, aviation is about passion, but for the OEMs, it's about finances ... yes, one has to make a profit or the business closes. Olive Ann Beech was once asked (a long time into her career), "What do you think is the biggest change in aviation has been since you started?". The "reporter" was looking for ... composite materials, new avionics, new radios, new... Her answer was simple and elegant. There is no difference. We started the business to make money, and that is still our goal today.

On a great note, both the "visionaries" and the OEMs are seriously looking at electric airplanes. There IS a future.