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New electric engine improves safety of light aircraft

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Re: New electric engine improves safety of light aircraft

#41

Post by knodi123 »

mrfusion wrote: post #22
knodi123 wrote: post #18

Earlier quoted context omitted.

There are no dumb questions, but if you were a pilot, this would certainly be a dumb thing to try. 1. in light planes, "the weight of the plane" is a little more complicated, since fuel can increase the weight of your plane by, like, 40% or so. We're talking, like, 500 pounds of fuel on a 1600 pound plane. 2. a helicopter has a very complex mechanism to give it control based on propellor movement. an airplane trying…

Thanks, makes sense for this case. I'm still wondering though, say for a purely electric plane designed for this type of VTOL from the ground up, is it workable? Couldn't the large area of the wings counteract the counter rotation or at decrease it to an acceptable level?

> say for a purely electric plane designed for this type of VTOL from the ground up, is it workable

Sure, toys can do it. That's what all these commercial drones are doing. But there's an irritating inverse square law that says the power required to hover goes up shockingly fast when you start to increase the weight.

Also, there's a reason commercial airlines don't use electric engines and batteries; the power-to-weight ratio for a gasoline engine far exceeds that of an electric+battery solution.

Re: New electric engine improves safety of light aircraft

#42

Post by repiret »

unics wrote: post #7

Wonderful idea. I do wonder how that changes the center of gravity and how much weight is diminished for cargo but seems well worth it. When the engine goes out you generally only have 10 seconds to decide where to land. Now it seems you have many minutes to find a place. In most circumstances I'd think this is better then the parachutes for planes because you have a chance to save very expensive airplanes.

> When the engine goes out you generally only have 10 seconds to decide where to land.

That depends entirely on how close you are to the ground when the engine goes out. If its during takeoff, you might have less than 10 seconds to decide. If its during cruise, you probably have much more than 10 seconds to decide - and of course you can continue to adjust your decision as you get closer to the ground.

Re: New electric engine improves safety of light aircraft

#43

Post by VLM »

unics wrote: post #7

Wonderful idea. I do wonder how that changes the center of gravity and how much weight is diminished for cargo but seems well worth it. When the engine goes out you generally only have 10 seconds to decide where to land. Now it seems you have many minutes to find a place. In most circumstances I'd think this is better then the parachutes for planes because you have a chance to save very expensive airplanes.

"When the engine goes out you generally only have 10 seconds to decide where to land."

Even helicopters don't fall that fast.

Lets say you're cruising 5000 feet above ground. That's a mile. You're in a plane with a roughly 10:1 glide ratio so you can glide 10 miles. At a best lift speed around 60 knots that's a mile a minute. Locally the only way to be more than 10 miles away from an airport or farm field would be over a great lake. During takeoff if you climb at 1000 FPM (maybe optimistic) that takes 5 minutes which puts you 5 miles away you can always turn around and glide back. All of my engineering estimates are wrong but wrong by far less than a factor of 2. Its a very long and stressful glide down if you have an engine failure.

Most engine failures don't make the news because nobody got killed or even landed off airport.

What tends to kill people is over confidence. Well, I have a big meeting tomorrow and I can handle a little rain storm, whoops. I only have a single engine and can't be bothered to IFR so I have to run scud under the overcast whoops I'm 5 miles from shore and only 1000 feet up when the engine dies (I think this most famously killed John Denver?)

Re: New electric engine improves safety of light aircraft

#44

Post by keenerd »

bri3d wrote: post #40
mrfusion wrote: post #34

Earlier quoted context omitted.

200KG for the motor sounds very high?

That's definitely extremely high - brushless motors with much higher power (~80hp) are in the 50kg range (see for example EV218).

Interesting! UQM has the "PowerPhase® Select 50" which is a 30kW motor. I would say this counts as the "very lightweight motor technology" I speculated they were using because you can't get any datasheets or information or even a price for the UQM products.

40hp 200kg brushless motors are extremely common by comparison. Dozens of places will sell you one for a few grand.

Re: New electric engine improves safety of light aircraft

#45

Post by repiret »

lujim wrote: post #32
mmaunder wrote: post #29

At the risk of stating the obvious, many crashes would not be affected by this: CFIT (controlled flight into terrain). Sadly common, it's how Kennedy junior died and many others. Stall/spin. Common on take off and landing and avoidance is a huge emphasis in training. Visual flight into instrument conditions. If untrained what often happens is the pilot will end up in a spin/spiral into the ground or doing a CFIT. Als…

That seems like a bit of an pessimistic take on this. Isn't that like saying front impact airbags aren't very helpful in a rear end collision? CFIT, stall/spin, and VFR into instrument conditions are all training deficiencies. This solution fixes something a pilot can't be trained to avoid, an engine failure at an inopportune time. Training can only take you as far as "glide and crash gracefully" without stalling and…

Most general aviation engine failures are caused by poor fuel management. Training and discipline helps just as much with fuel management.

While there are clearly situations where this device can save lives, I agree with the GP that the case needs to be made that its worth the cost and weight, and that the people peddling it haven't made that case.

Re: New electric engine improves safety of light aircraft

#46

Post by RealCasually »

pwnna wrote: post #35
digi_owl wrote: post #6

Earlier quoted context omitted.

I suspect that while landing you really want the engine in "neutral" so you can at any moment kick it into full power if some issue shows up. Landing is damn close to a controlled crash. And i don't think these kinds of aircrafts have the wing surface etc to be floating around on thermals.

Usually when landing you want something like 110% of your stall speed, which means that you're not "crashing" (by which I mean stalling). This involves some sort of engine power. I am not aware of any plane that lands without power outside of an emergency.

Staying above stall speed in a descent does not require any power. It is extremely common to perform a "power off" landing in a small plane, and these are often not in emergency cases.

Re: New electric engine improves safety of light aircraft

#47

Post by mhb »

VLM wrote: post #43
unics wrote: post #7

Wonderful idea. I do wonder how that changes the center of gravity and how much weight is diminished for cargo but seems well worth it. When the engine goes out you generally only have 10 seconds to decide where to land. Now it seems you have many minutes to find a place. In most circumstances I'd think this is better then the parachutes for planes because you have a chance to save very expensive airplanes.

"When the engine goes out you generally only have 10 seconds to decide where to land." Even helicopters don't fall that fast. Lets say you're cruising 5000 feet above ground. That's a mile. You're in a plane with a roughly 10:1 glide ratio so you can glide 10 miles. At a best lift speed around 60 knots that's a mile a minute. Locally the only way to be more than 10 miles away from an airport or farm field would be ov…

I think this most famously killed John Denver

Not exactly. John Denver NTSB report: http://www.ntsb.gov/news/press-releases/Pages/NTSB_Determine...

Re: New electric engine improves safety of light aircraft

#48

Post by lujim »

repiret wrote: post #45
lujim wrote: post #32

Earlier quoted context omitted.

That seems like a bit of an pessimistic take on this. Isn't that like saying front impact airbags aren't very helpful in a rear end collision? CFIT, stall/spin, and VFR into instrument conditions are all training deficiencies. This solution fixes something a pilot can't be trained to avoid, an engine failure at an inopportune time. Training can only take you as far as "glide and crash gracefully" without stalling and…

Most general aviation engine failures are caused by poor fuel management. Training and discipline helps just as much with fuel management. While there are clearly situations where this device can save lives, I agree with the GP that the case needs to be made that its worth the cost and weight, and that the people peddling it haven't made that case.

I don't think of it as someone 'peddling' something. To me it seems like a creative solution to an actual problem.

Training is the best, but private pilots vary drastically in their training, skill, experience level (especially recent experience).

While I would love to see all pilots selected out of the population for their aptitude, then go through years of intense military like training followed by checkrides every 6 months, it's just not realistic in General Aviation. It's a group of people that differ wildly in their aptitude, age, skill level, that just happen to be healthy enough to pass a relatively low bar medical exam.

Training for Private Pilots in the US might not be perfect, but I don't think a "throw training at it" response is all that useful of an answer. Train what? For how many hours, and require recency of experience after how long?

Re: New electric engine improves safety of light aircraft

#49

Post by dpark »

keenerd wrote: post #39
mrfusion wrote: post #34

Earlier quoted context omitted.

200KG for the motor sounds very high?

Find us a lighter one for sale.

http://hpevs.com/catalog-ac-3X%20oil%20cooled.html

If I'm reading correctly, the AC-35 has a peak rating of 47.78 horsepower, and weighs 43.9kg.

Presumably the 200kg motors you're looking at are not intended to be part of a moving vehicle. Those are likely intended for use in factories or shops where the weight is of little concern but durability is at a premium.

Re: New electric engine improves safety of light aircraft

#50

Post by pwnna »

phillc73 wrote: post #37
pwnna wrote: post #35

Earlier quoted context omitted.

Usually when landing you want something like 110% of your stall speed, which means that you're not "crashing" (by which I mean stalling). This involves some sort of engine power. I am not aware of any plane that lands without power outside of an emergency.

Apart from all those thousands of sailplanes people fly every week. They land without power, and very few of those landings would be an emergency.

Yeah that is correct, I was more thinking of commercial flights rather than sailplanes/gliders
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