Electrically Powered Ultralight Aircraft

On Aug 5, 1:12 pm, Larry Dighera wrote:
On Sun, 05 Aug 2007 10:53:30 -0700, Phil wrote
in om:

Very interesting. It doesn't mention how long it takes to charge the
batteries.

There's a pod-cast here in which Sonex's owner John Monnett and
engineer Pete Buck discuss that topic:http://www.aviationweek.com/media/audio/sonex.mp3

I wonder if anyone has done any experiments with a hybrid drive system
for an aircraft. I am thinking of something like a 3-cylinder diesel
engine providing enough power for cruise, supplemented with a battery
pack and motor for takeoff and climb.

In rec.aviation.piloting Phil wrote:
On Aug 5, 1:12 pm, Larry Dighera wrote:
On Sun, 05 Aug 2007 10:53:30 -0700, Phil wrote
in om:

Very interesting. It doesn't mention how long it takes to charge the
batteries.

There's a pod-cast here in which Sonex's owner John Monnett and
engineer Pete Buck discuss that topic:http://www.aviationweek.com/media/audio/sonex.mp3

I wonder if anyone has done any experiments with a hybrid drive system
for an aircraft. I am thinking of something like a 3-cylinder diesel
engine providing enough power for cruise, supplemented with a battery
pack and motor for takeoff and climb.

The advantage for hybrids comes from stop and go driving where the
battery is charged by regenerative braking.

There isn't much stop and go flying.

--
Jim Pennino

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In rec.aviation.soaring wrote:
In rec.aviation.piloting Phil wrote:
I wonder if anyone has done any experiments with a hybrid drive system
for an aircraft. I am thinking of something like a 3-cylinder diesel
engine providing enough power for cruise, supplemented with a battery
pack and motor for takeoff and climb.

The advantage for hybrids comes from stop and go driving where the
battery is charged by regenerative braking.

There isn't much stop and go flying.

There is also an advantage which comes from only needing to size the
engine for cruise, not for acceleration, since you can suppliment the
smaller engine with the batteries during acceleration. Smaller engines are
generally more efficient than larger ones when putting out the same amount
of power.

The other advantage is that the engine can stay in the engine's efficiency
band even when the RPM demanded of it is higher (acceleration) or lower
(initial start).

However, these also don't help nearly as much on aircraft as on cars. The
difference between acceleration and cruise power on an aircraft is much
less than in a car, and aircraft engines tend to spend most of their time
in the efficiency band anyway, especially if there's a constant-speed prop
affixed. The extra drag caused by the extra weight of the batteries and
the rest of the hybrid system would probably outweigh any efficiency gain.

--
Michael Ash
Rogue Amoeba Software

"Michael Ash" wrote in message
...
In rec.aviation.soaring wrote:
In rec.aviation.piloting Phil wrote:
I wonder if anyone has done any experiments with a hybrid drive system
for an aircraft. I am thinking of something like a 3-cylinder diesel
engine providing enough power for cruise, supplemented with a battery
pack and motor for takeoff and climb.

The advantage for hybrids comes from stop and go driving where the
battery is charged by regenerative braking.

There isn't much stop and go flying.

There is also an advantage which comes from only needing to size the
engine for cruise, not for acceleration, since you can suppliment the
smaller engine with the batteries during acceleration. Smaller engines are
generally more efficient than larger ones when putting out the same amount
of power.

The other advantage is that the engine can stay in the engine's efficiency
band even when the RPM demanded of it is higher (acceleration) or lower
(initial start).

However, these also don't help nearly as much on aircraft as on cars. The
difference between acceleration and cruise power on an aircraft is much
less than in a car, and aircraft engines tend to spend most of their time
in the efficiency band anyway, especially if there's a constant-speed prop
affixed. The extra drag caused by the extra weight of the batteries and
the rest of the hybrid system would probably outweigh any efficiency gain.

--
Michael Ash

There is, I believe, a UAV using hybrid power. The idea is to switch off
the gas engine and run on electric power for a stealthy approach to a
"location of interest".

Bill Daniels
Rogue Amoeba Software

"Michael Ash" wrote

The extra drag caused by the extra weight of the batteries and
the rest of the hybrid system would probably outweigh any efficiency gain.

Probably? You are being far too kind. A redundant power system, only
helping at takeoff is GOING to waste efficiency. There is no way to avoid
that fact unless then cruise speed is going to be painfully slow.
--
Jim in NC

In rec.aviation.soaring Morgans wrote:

"Michael Ash" wrote

The extra drag caused by the extra weight of the batteries and
the rest of the hybrid system would probably outweigh any efficiency gain.

Probably? You are being far too kind. A redundant power system, only
helping at takeoff is GOING to waste efficiency. There is no way to avoid
that fact unless then cruise speed is going to be painfully slow.

I don't doubt you in any way, and in fact my general feeling is in
complete agreement with you. But I'm not speaking from a position of great
knowledge so I used a weasel word to indicate that.

--
Michael Ash
Rogue Amoeba Software

In rec.aviation.piloting Michael Ash wrote:
In rec.aviation.soaring wrote:
In rec.aviation.piloting Phil wrote:
I wonder if anyone has done any experiments with a hybrid drive system
for an aircraft. I am thinking of something like a 3-cylinder diesel
engine providing enough power for cruise, supplemented with a battery
pack and motor for takeoff and climb.

The advantage for hybrids comes from stop and go driving where the
battery is charged by regenerative braking.

There isn't much stop and go flying.

There is also an advantage which comes from only needing to size the
engine for cruise, not for acceleration, since you can suppliment the
smaller engine with the batteries during acceleration. Smaller engines are
generally more efficient than larger ones when putting out the same amount
of power.

If you are trying to say it takes less power to maintain speed than to
accelerate, yes that is true.

The advantage from the electric engine at cruise is that it uses zero
energy.

There were attempts to increase mileage of gas engines by turning off
uneeded cylinders at cruise. They didn't work that well and you still
had to move the pistons, the big crank, and all the rest of the stuff.

The other advantage is that the engine can stay in the engine's efficiency
band even when the RPM demanded of it is higher (acceleration) or lower
(initial start).

The transmission keeps the engine RPM within a limited range.

Hybrids have no effect on that.

However, these also don't help nearly as much on aircraft as on cars. The
difference between acceleration and cruise power on an aircraft is much
less than in a car, and aircraft engines tend to spend most of their time
in the efficiency band anyway, especially if there's a constant-speed prop
affixed. The extra drag caused by the extra weight of the batteries and
the rest of the hybrid system would probably outweigh any efficiency gain.

It doesn't help at all on airplanes.

The advantage to hybrids is they get better gas mileage.

They do that by using the deceleration to charge batteries which recovers
some of the kinetic energy instead of using it all to heat the brake linings.

--
Jim Pennino

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wrote in message
...

The advantage from the electric engine at cruise is that it uses zero
energy.

Snippage
--
Jim Pennino

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You want to support this, somehow?

Tim Ward

In rec.aviation.piloting Tim Ward wrote:

wrote in message
...

The advantage from the electric engine at cruise is that it uses zero
energy.

Snippage
--
Jim Pennino

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You want to support this, somehow?

Tim Ward

At cruise the electric motor is turned off.

The only energy used is some slight bearing friction.

The electric motor is only turned on when more power than the gas
engine can provide is needed.

--
Jim Pennino

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wrote:
In rec.aviation.piloting Tim Ward wrote:

wrote in message
...

The advantage from the electric engine at cruise is that it uses zero
energy.

Snippage
--
Jim Pennino

Remove .spam.sux to reply.

You want to support this, somehow?

Tim Ward

At cruise the electric motor is turned off.

The only energy used is some slight bearing friction.

The electric motor is only turned on when more power than the gas
engine can provide is needed.


To carry more weight at the same speed and altitude takes more power, so
you have to account for the energy expended kiting you deadweight
electric takeoff system around the sky as well. Sizing an engine for
cruise has been done, if only backwards. Think JATO. Most JATO's are
actually RATO (rocket assisted takeoff). I expect RATO would beat an
electric system based on energy density and the fact that when it is
done you have reduced your weight by the fuel. I also suspect for a
given amount of thrust the rocket will be lighter than an electric motor
and associated clutches and gearing. In my opinion, at this point in
time it is just as practical for a homebuilt as well as in not.


Charles