Electrically Powered Ultralight Aircraft

In rec.aviation.piloting cavelamb himself wrote:
wrote:

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.


Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?

--
Jim Pennino

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wrote:
In rec.aviation.piloting cavelamb himself wrote:
wrote:
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.

Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?


No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.

Charles

In rec.aviation.piloting Charles Vincent wrote:
wrote:
In rec.aviation.piloting cavelamb himself wrote:
wrote:
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.

Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?


No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.


Gee, you mean all I gotta do is tweek the trim and throttle a bit?

Who'd have guessed it? :-)


--
Jim Pennino

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Charles Vincent wrote:

No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.

Charles


Don't be snotty, Charles.


Since the subject is an electrically powered aircraft, the weight issue
is not trivial. That's been my issue with this thread from the start.

The constraints given here were to fly at the same speed and altitude
but at a higher weright.

You can increase lift via increased angle of attack only as far as
CLmax. No Farther. (You seem to have that part right)

Beyond that any increased weight will require increased wing area.

Aspect ratio alone won't answer is most cases.

And - an electric powered plane would NOT lose weight in flight.

No electrons are "consumed" - no change in battery weight.

cavelamb himself wrote:


Don't be snotty, Charles.


Since the subject is an electrically powered aircraft, the weight issue
is not trivial. That's been my issue with this thread from the start.

The constraints given here were to fly at the same speed and altitude
but at a higher weright.

You can increase lift via increased angle of attack only as far as
CLmax. No Farther. (You seem to have that part right)

Beyond that any increased weight will require increased wing area.

Aspect ratio alone won't answer is most cases.

And - an electric powered plane would NOT lose weight in flight.

No electrons are "consumed" - no change in battery weight.



Not really being snotty at all. Frankly, I was in the process of
deleting screenfulls of messages on the topic of electric powered
airplanes being as the subject really holds no interest for me. For
some reason I happened to read "The advantage from the electric engine
at cruise is that it uses zero energy" on one message just as I deleted
it. Pulling it back from the trash, I felt compelled to respond to it.
My mistake. For some reason you are in turn compelled to nit pick my
correct assertion because it did not completely cover the relevant
aerodynamic theory. In my opinion, it covered enough, but not following
the thread, I have no idea what sort of debate has been raging. As I
stated elsewhere, I just didn't expect that information required for
even the most basic pilot ticket would be the subject of any debate
here. In the end, to fly at the same speed and altitude but at a higher
weight requires more power be applied, whether you use that power to
drag the same wing at a higher angle of attack or a bigger wing doesn't
change that. Or you could use more power to drag the wing at a higher
speed to generate the lift you needed. All of this ignores the fact
that for internal combustion aircraft powerplants, the weight per HP
goes down as the power goes up. Last time I looked at it, the opposite
is true of electric motors. I don't think an electric assist for an IC
engine is going to be viable for aircraft in the near future.


Charles

Charles Vincent wrote:

cavelamb himself wrote:


Don't be snotty, Charles.


Since the subject is an electrically powered aircraft, the weight issue
is not trivial. That's been my issue with this thread from the start.

The constraints given here were to fly at the same speed and altitude
but at a higher weright.

You can increase lift via increased angle of attack only as far as
CLmax. No Farther. (You seem to have that part right)

Beyond that any increased weight will require increased wing area.

Aspect ratio alone won't answer is most cases.

And - an electric powered plane would NOT lose weight in flight.

No electrons are "consumed" - no change in battery weight.



Not really being snotty at all. Frankly, I was in the process of
deleting screenfulls of messages on the topic of electric powered
airplanes being as the subject really holds no interest for me. For
some reason I happened to read "The advantage from the electric engine
at cruise is that it uses zero energy" on one message just as I deleted
it. Pulling it back from the trash, I felt compelled to respond to it.
My mistake. For some reason you are in turn compelled to nit pick my
correct assertion because it did not completely cover the relevant
aerodynamic theory. In my opinion, it covered enough, but not following
the thread, I have no idea what sort of debate has been raging. As I
stated elsewhere, I just didn't expect that information required for
even the most basic pilot ticket would be the subject of any debate
here. In the end, to fly at the same speed and altitude but at a higher
weight requires more power be applied, whether you use that power to
drag the same wing at a higher angle of attack or a bigger wing doesn't
change that. Or you could use more power to drag the wing at a higher
speed to generate the lift you needed. All of this ignores the fact
that for internal combustion aircraft powerplants, the weight per HP
goes down as the power goes up. Last time I looked at it, the opposite
is true of electric motors. I don't think an electric assist for an IC
engine is going to be viable for aircraft in the near future.


Charles


I guess I was just over reacting to the swing wing parasol comment.

And yes, I can see your point.
Higher Cl - or bigger wing. Either will require more power.
Which was my point as well.

Yep. A lot of this thread has been - well - fanciful?


Richard

In rec.aviation.piloting Charles Vincent wrote:
cavelamb himself wrote:


Not really being snotty at all. Frankly, I was in the process of
deleting screenfulls of messages on the topic of electric powered
airplanes being as the subject really holds no interest for me. For
some reason I happened to read "The advantage from the electric engine
at cruise is that it uses zero energy" on one message just as I deleted
it. Pulling it back from the trash, I felt compelled to respond to it.

Have either of you guys heard of the term "thread drift"?

Both of you are responding to the part of the thread that drifted off
to the topic of hybrid CARS and how they get good mileage.

--
Jim Pennino

Remove .spam.sux to reply.

wrote:
In rec.aviation.piloting Charles Vincent wrote:
cavelamb himself wrote:


Not really being snotty at all. Frankly, I was in the process of
deleting screenfulls of messages on the topic of electric powered
airplanes being as the subject really holds no interest for me. For
some reason I happened to read "The advantage from the electric engine
at cruise is that it uses zero energy" on one message just as I deleted
it. Pulling it back from the trash, I felt compelled to respond to it.

Have either of you guys heard of the term "thread drift"?

Both of you are responding to the part of the thread that drifted off
to the topic of hybrid CARS and how they get good mileage.


Fair enough.

Charles

wrote:
In rec.aviation.piloting Charles Vincent wrote:

cavelamb himself wrote:



Not really being snotty at all. Frankly, I was in the process of
deleting screenfulls of messages on the topic of electric powered
airplanes being as the subject really holds no interest for me. For
some reason I happened to read "The advantage from the electric engine
at cruise is that it uses zero energy" on one message just as I deleted
it. Pulling it back from the trash, I felt compelled to respond to it.


Have either of you guys heard of the term "thread drift"?

Both of you are responding to the part of the thread that drifted off
to the topic of hybrid CARS and how they get good mileage.


Look again, Jim.

It seems to have drifted back on thread.

In rec.aviation.piloting cavelamb himself wrote:
wrote:
In rec.aviation.piloting Charles Vincent wrote:

cavelamb himself wrote:



Not really being snotty at all. Frankly, I was in the process of
deleting screenfulls of messages on the topic of electric powered
airplanes being as the subject really holds no interest for me. For
some reason I happened to read "The advantage from the electric engine
at cruise is that it uses zero energy" on one message just as I deleted
it. Pulling it back from the trash, I felt compelled to respond to it.


Have either of you guys heard of the term "thread drift"?

Both of you are responding to the part of the thread that drifted off
to the topic of hybrid CARS and how they get good mileage.


Look again, Jim.

It seems to have drifted back on thread.

This is probably a historic moment.

Normally what happens when thread drift begins is that it increases
at an increasing rate such that what was originally zepplin aerodynamics
becomes the best recipe for strawberry preserves...

--
Jim Pennino

Remove .spam.sux to reply.