composites vs. aluminum

[John C]

I know this gets talked about all the time...but I have aquestion I was
hoping someone smarter than me could help me with.

An aluminum evangelist showed me this link:
http://www.aerotalk.com/myth_02.cfm

The author asserts that:
" The ratio of empty to gross weight is one of the most telling measures of
structural efficiency.
The equations are basic:EMPTY WEIGHT + PAYLOAD = GROSS WEIGHT

Reduce empty weight by 100 lbs and the pilot can load an extra 100 lbs of
payload, fuel/ baggage/ people.

EMPTY WEIGHT/GROSS WEIGHT = WEIGHT EFFICIENCY RATIO

The lower the ratio, the more efficient the design."

He goes on to use this determination of strength/weight (or, structural
efficiency) to determine that composites do not offer a greater
strength/weight ration in airframe construction applications.

But then I read about the new 7E7, which is a largely composite aircraft,
thus lighter, thus more efficient.

How do I reconcile these conflicting pieces of information?

[Leon McAtee]

"John C" > wrote in message >...
> EMPTY WEIGHT/GROSS WEIGHT = WEIGHT EFFICIENCY RATIO
>
> The lower the ratio, the more efficient the design."
>
> He goes on to use this determination of strength/weight (or, structural
> efficiency) to determine that composites do not offer a greater
> strength/weight ration in airframe construction applications.

Just how did he do this?

> But then I read about the new 7E7, which is a largely composite aircraft,
> thus lighter, thus more efficient.
>
> How do I reconcile these conflicting pieces of information?


The information is not necessarily conflicting. You can build heavy
out of any kind of material. It's just that composite planes are so
easy to build overweight compared to other materials.

Also most of the homebuilt moldless composite planes are way over
built/designed due to quality control issues. The plane must be
designed for the worst case builder and thus ends up just strong
enough when built by a poor craftsman and heavier than it could have
been if all the builders were good craftsmen. The double bite comes
when the poor craftsman uses too much resin and filler. Not only is
his weaker than it could have been, it's heavier than one built by the
good craftsmen.

When you have good quality control you can design the composite part
to tighter standards, and end up with a very efficient structure.

Think how heavy some RV's would be if the homebuilder had to roll his
own aluminum from billets...........or make his own plywood for wing
skins.....

It's all about quality control.
===================
Leon McAtee

[Dude]

You can do best with a combination.

Composites can make complex shapes and be used to make a slicker yet lighter
fuselage, but if you use a simple airfoil, it is tough to build lighter than
an aluminum wing without getting expensive.

A lot also depends on what speed the plane will be cruising at. The higher
the speed, the more important to be slick.

I would be interested to know at what speed do wing rivets really start to
hurt vs. the extra weight of a normal homebuilt composite wing. I would be
willing to take one of our more experience builder's best guess.



"John C" > wrote in message
...
> I know this gets talked about all the time...but I have aquestion I was
> hoping someone smarter than me could help me with.
>
> An aluminum evangelist showed me this link:
> http://www.aerotalk.com/myth_02.cfm
>
> The author asserts that:
> " The ratio of empty to gross weight is one of the most telling measures
of
> structural efficiency.
> The equations are basic:EMPTY WEIGHT + PAYLOAD = GROSS WEIGHT
>
> Reduce empty weight by 100 lbs and the pilot can load an extra 100 lbs of
> payload, fuel/ baggage/ people.
>
> EMPTY WEIGHT/GROSS WEIGHT = WEIGHT EFFICIENCY RATIO
>
> The lower the ratio, the more efficient the design."
>
> He goes on to use this determination of strength/weight (or, structural
> efficiency) to determine that composites do not offer a greater
> strength/weight ration in airframe construction applications.
>
> But then I read about the new 7E7, which is a largely composite aircraft,
> thus lighter, thus more efficient.
>
> How do I reconcile these conflicting pieces of information?
>
>

[Stealth Pilot]

On 29 Apr 2004 18:32:35 -0700, (Leon McAtee)
wrote:

>"John C" > wrote in message >...
>> EMPTY WEIGHT/GROSS WEIGHT = WEIGHT EFFICIENCY RATIO
>>
>> The lower the ratio, the more efficient the design."
>>
>> He goes on to use this determination of strength/weight (or, structural
>> efficiency) to determine that composites do not offer a greater
>> strength/weight ration in airframe construction applications.
>
>Just how did he do this?
>
>> But then I read about the new 7E7, which is a largely composite aircraft,
>> thus lighter, thus more efficient.
>>
>> How do I reconcile these conflicting pieces of information?
>
>
>The information is not necessarily conflicting. You can build heavy
>out of any kind of material. It's just that composite planes are so
>easy to build overweight compared to other materials.
>
>Also most of the homebuilt moldless composite planes are way over
>built/designed due to quality control issues. The plane must be
>designed for the worst case builder and thus ends up just strong
>enough when built by a poor craftsman and heavier than it could have
>been if all the builders were good craftsmen. The double bite comes
>when the poor craftsman uses too much resin and filler. Not only is
>his weaker than it could have been, it's heavier than one built by the
>good craftsmen.
>
>When you have good quality control you can design the composite part
>to tighter standards, and end up with a very efficient structure.
>

the problem for composite structures in the past has been their
unknown fatigue life. they are typically built to much higher safety
margins than aluminium aircraft which have been a more understood
technology.
if composites were built to the same margins as conventional aircraft
you'd see them being a lot lighter and there'd be less of a conundrum.
Stealth Pilot
Australia

[[email protected]]

John C wrote:

> I know this gets talked about all the time...but I have aquestion I
> was hoping someone smarter than me could help me with.



> He goes on to use this determination of strength/weight (or,
> structural efficiency) to determine that composites do not offer a
> greater strength/weight ration in airframe construction applications.
You can compare the same airframe with Al alloy and carbon fiber:
Michel Colomban MC100: 202Kg empty (F-PECH)
Colomban Robin MCR01: 235kg empty (G-BYEZ)
http://www.avnet.co.uk/lts/pages/mcr1.htm

> But then I read about the new 7E7, which is a largely composite
> aircraft, thus lighter, thus more efficient.
Scale effect and industrial way to built, no experimental built.


> How do I reconcile these conflicting pieces of information?

Basicaly, the composite carbon-epoxy is the best for strength. But, in
the case of MCR01, a carbon fiber skin for the wing, just enough for
loads is too thin face a little gravel. For durability, its need more
fiber, more epoxy, more weight. In fine, the skin is still in Al
alloy.


By
--
Gardan GY20 Minicab F-PRAZ
Philippe Vessaire ҿӬ

[GeorgeB]

On Thu, 29 Apr 2004 16:35:41 -0400, Todd Pattist
> wrote:

>"John C" > wrote:
>
>>The author asserts that:
>>" The ratio of empty to gross weight is one of the most telling measures of
>>structural efficiency.
>>He goes on to use this determination of strength/weight (or, structural
>>efficiency) to determine that composites do not offer a greater
>>strength/weight ration in airframe construction applications.
>>
>>But then I read about the new 7E7, which is a largely composite aircraft,
>>thus lighter, thus more efficient.
>>
>>How do I reconcile these conflicting pieces of information
>
>They don't conflict. The author acknowledges that lighter
>weight is possible with a composite if you use advanced
>composite techniques. The 7E7 uses such techniques, but
>they are expensive. Modern racing gliders and small
>composite aircraft are not built using those techniques, and
>they don't use composites to get weight reduction. They use
>composites to get smooth curves, low drag and high speed for
>about the same weight.
>
>The author's "structural efficiency" formula ignores drag,
>and that's the main concern for those using composites.
>Todd Pattist

I agree with Todd; further, the ratio comparison likely is significant
only within similar types of aircraft. I suspect the advantages of
one construction technique over another change rather significantly
from ultralight to glider to SEL to MEL to heavy.

Have we any experts around to comment?

[[email protected]]

On Fri, 30 Apr 2004 15:29:22 -0000, "karel adams"
> wrote:

>Does this imply that a slow & sturdy aircraft does not
>profit as much from the composite advantages
>and hence can better be built from aluminium?
>And that likewise a sleek fast tourer better be composite?
>
>KA (learning slowly)

That sounds pretty right Karel. Real world laminar flow did not
really begin to happen until the advent of super smooth composite
airplanes. Laminar flow isn't something an airplane that does not
cruise faster than 130 kts or so needs.

The P-51 Mustang is well known as one of the first fighters to make
use of a laminar flow wing. Many ascribe it's long range and high
speed to the wing design. In fact it very likely did (then and now)
not achieve much laminar flow for several reasons. It was discovered
that even slight imperfections in the wing caused the laminar flow to
trip to turbulent. Dents, scuff marks from ground crew, patches, butt
joints in the aluminum sheeting all caused the laminar flow to trip to
turbulent. In addition, it was found that the area within the
propwash was not laminar. The Mustang had a mighty big prop that
washed about a quarter to a third of each wing.

So achieving laminar flow isn't easy. Getting attached laminar flow
is one of the big reason (as I understand it) why Burt Rutan designed
the rear engined EZ series of airplanes.

Corky Scott

[BllFs6]

>So achieving laminar flow isn't easy. Getting attached laminar flow
>is one of the big reason .....

This brings up a question Ive had..

A laminar flow wing is better than a non one.....

At what speeds does the advantage become significant? Or at what speeds does it
really pay to opt for a laminar wing?

And... is a laminar wing that happens to be dirty etc and not working in a
laminar fashion STILL better than its non laminar from the start counterpart
wing at the same speed?

take care

Blll

[Bill Daniels]

"BllFs6" > wrote in message
...
> >So achieving laminar flow isn't easy. Getting attached laminar flow
> >is one of the big reason .....
>
> This brings up a question Ive had..
>
> A laminar flow wing is better than a non one.....
>
> At what speeds does the advantage become significant? Or at what speeds
does it
> really pay to opt for a laminar wing?

Laminar flow is easier to achieve at high Reynolds numbers and the Reynolds
number increases with speed. See:
http://www.efunda.com/formulae/smc_fluids/calc_reynolds.cfm

Therefore the answer is that a laminar wing pays off at all speeds but is
most effective in the "drag bucket" of the airfoil in question - that is
within a range of AOA where extensive laminar flow is achieved. This range
almost always extends below the AOA used for cruise flight and almost up to
the stalling AOA.
>
> And... is a laminar wing that happens to be dirty etc and not working in a
> laminar fashion STILL better than its non laminar from the start
counterpart
> wing at the same speed?
>
All wings have some laminar flow and none have all laminar flow. The more
you have, the better. Wing sections designed to have a large amount of
laminar flow (Laminar airfoils) are always better. All airfoils are
degraded to some degree by surface roughness. Even laminar airfoils that
are very sensitive to surface roughness will be better than one not designed
for extensive laminar flow.

It's better to think of airfoils as better or worse and not to group them
into laminar and non-laminar. Since WWII, almost all new airfoils have been
designed with the goal of achieving as much laminar flow as possible when
used in the intended application.

Bill Daniels

[Richard Lamb]

karel adams wrote:
>
> > schreef in bericht
> ...
> > On Fri, 30 Apr 2004 15:29:22 -0000, "karel adams"
> > > wrote:
> >
> > >Does this imply that a slow & sturdy aircraft does not
> > >profit as much from the composite advantages
> > >and hence can better be built from aluminium?
> > >And that likewise a sleek fast tourer better be composite?
> > >
> > >KA (learning slowly)
> >
> > That sounds pretty right Karel. Real world laminar flow did not
> > really begin to happen until the advent of super smooth composite
> > airplanes. Laminar flow isn't something an airplane that does not
> > cruise faster than 130 kts or so needs.
> (...)
> > So achieving laminar flow isn't easy. Getting attached laminar flow
> > is one of the big reason (as I understand it) why Burt Rutan designed
> > the rear engined EZ series of airplanes.
>
> OK. If one wanted an easy-to-fly tourer, cruising at 120 kts or so,
> wouldn't it be a nice compromise to build the wings in composite
> and the fuselage in aluminium?
> Are there homebuild desgins like this?
>
> Karel
>
> >
> > Corky Scott

Like the Glass Star? Steel tube frame, composite fuselage skins,
and stressed skin aluminum wing.

Richard

[Bill Daniels]

I used to have a friend that built metal aircraft. He had an interesting
way of explaining his preference.

"When you build a composite aircraft", he said, "first you make the plug and
then the mold and then the aircraft." "It's like building the same damned
airplane three times."

"When I'm through pounding a rivet", he said, "I'm through with the damn
thing". "I don't have to wait for it to dry or cure". "I don't need any
particular temperature to work either." "If I'm comfortable, the airplane
is too."

I fly a composite aircraft.

Bill Daniels

[Paul Lee]

wrote in message >...
>... turbulent. In addition, it was found that the area within the
> propwash was not laminar. The Mustang had a mighty big prop that
> washed about a quarter to a third of each wing.
>
> So achieving laminar flow isn't easy. Getting attached laminar flow
> is one of the big reason (as I understand it) why Burt Rutan designed
> the rear engined EZ series of airplanes....

Yes. pushers can get good prop thrust efficiency easier since the
"thrusted" air behind is not impeded by any structure. Air molecules
move randomly at about 1000KTS and will easily fill in the void in
front of a pusher prop to be used for thrust. In a tractor the
thrusted air is deflected by the fuselage resulting in more thrust
loses. Thats why tractors generally have bigger props to "reach"
around the cowling and over wings.

---------------------------------------------------
Paul Lee, SQ2000 canard: http://www.abri.com/sq2000

[[email protected]]

On 2 May 2004 17:02:05 -0700, (Paul Lee) wrote:

>Yes. pushers can get good prop thrust efficiency easier since the
>"thrusted" air behind is not impeded by any structure. Air molecules
>move randomly at about 1000KTS and will easily fill in the void in
>front of a pusher prop to be used for thrust. In a tractor the
>thrusted air is deflected by the fuselage resulting in more thrust
>loses. Thats why tractors generally have bigger props to "reach"
>around the cowling and over wings.

Not sure that prop efficiencies are that much greater for the pusher
than for the tractor engined airplanes Paul. While it's true that the
pusher prop doesn't throw it's thrust against the fuselage, the
fuselage is nevertheless affecting things. You always know when a
pusher flies by because of the characteristic whapping rasping sound
the prop makes. It makes this sound because the airflow to the prop
is masked by the shape of the fuselage and wings at various places.
Around the bottom of the fuselage the prop sees relatively clean air,
but when it passes the wing, it hits a mass of downwash from the wing.
Then clean air, then turbulent air again. Plus, the mass of the
fuselage itself masks off some of the air the prop sees. The
turbulence is so severe that it's my understanding metal props are not
recommended for EZ's.

In addition, the diameter of the prop on tractor airplanes isn't
generally larger because it has to be to generate thrust around the
fuselage, it's larger because it can be. Props on pushers generally
have to be smaller in order to not grind it off on the ground in case
of inadvertant high AOA. Over rotating with an EZ risks a prop
strike.

Most tractor engined airplanes don't have that issue. Rotating for
takeoff moves the prop away from the ground, not closer to it.

My understanding is that Burt Rutan has said that front engine or
pusher, the efficiencies and design advantages pretty much cancel each
other out if you design around them, in other words neither design
offers a clear advantage over the other.

Corky Scott

[Paul Lee]

wrote in message >...
> On 2 May 2004 17:02:05 -0700, (Paul Lee) wrote:
>................. You always know when a
> pusher flies by because of the characteristic whapping rasping sound
> the prop makes. It makes this sound because the airflow to the prop
> is masked by the shape of the fuselage and wings at various places.
> Around the bottom of the fuselage the prop sees relatively clean air,
> but when it passes the wing, it hits a mass of downwash from the wing.
> Then clean air, then turbulent air again..........
> In addition, the diameter of the prop on tractor airplanes isn't
> generally larger because it has to be to generate thrust around the
> fuselage, it's larger because it can be. Props on pushers generally
> have to be smaller in order to not grind it off on the ground in case
> of inadvertant high AOA. Over rotating with an EZ risks a prop
> strike.
> ......

You raised some good points. The actual sound difference doesn't
bother me as a pilot. In fact the "behind" sound in a pusher is more
bearable. But the fact is that even turbulent air, while not ideal,
can be pushed back with the prop - those molecules moving randomly at
1000kts can easily fill in the void - unless you are moving near
1000kts. In a sense you have "turbulent" (dead) air in front when
taking off. Best possible laminar flow, from what I gather, is more
crucial for wing lift than for prop thrust. So I still think there is
some advantage to pusher props - although, as you pointed out, it may
not be very significant.

Just a further brainstorm curiosity. Not sure if I can express this
clearly. The greatest net force you have is on takeoff. The prop grabs
the molecules and throws them backward. The change in molecular
momentum results in the thrust (F = dP/dt). When the air is moving
fast backward (high air speed) there is much smaller change in
momentum - granted there is more molecules pushed. Would the turbulent
air (slow air) in front of a pusher prop help the thrust somewhat? A rocket
engine, with molecules relatively at initial 0 speed, has more thrust
than a jet.

[[email protected]]

On 3 May 2004 16:11:01 -0700, (Paul Lee) wrote:

>Just a further brainstorm curiosity. Not sure if I can express this
>clearly. The greatest net force you have is on takeoff. The prop grabs
>the molecules and throws them backward. The change in molecular
>momentum results in the thrust (F = dP/dt). When the air is moving
>fast backward (high air speed) there is much smaller change in
>momentum - granted there is more molecules pushed. Would the turbulent
>air (slow air) in front of a pusher prop help the thrust somewhat? A rocket
>engine, with molecules relatively at initial 0 speed, has more thrust
>than a jet.

My understanding, which is limited I admit, is that pusher props are
less efficient than the exact same engine and prop mounted on the
front of an airplane. It's one of those characteristic give and takes
that happen throughout the relm of aviation design. True, the pusher
gets to push air directly to the rear. The downside is that the air
it gets to accelerate is dirty (turbulent) air and that degrades
performance. The tractor engine sees clean air for it's prop, but it
smacks some of the air it accelerates against the nose of the
fuselage, the windscreen, wings and appendages. There's good with the
bad though, the column of air blasted to the rear gives the elevators
and rudder effective air movement to become operational even at very
low forward airspeeds. Ever see a Pitts taxiing in with it's tail up
in the air? With a pusher, the air being blown rearwards doesn't pass
over any of the control surfaces, they must wait for forward motion to
become fast enough for them to have enough airflow before responding
to input. This is one reason why the EZ's have a relatively long
takeoff roll.

You are absolutely correct that a front mounted prop pushes a certain
amount of air against the nose of the fuselage, and that's thrust
wasted. But remember, props don't produce a whole lot of thrust down
near the hub anyway so percentage wise, there isn't much thrust there
to waste. In fact in some props, there isn't really an airfoil near
the hub. This would be true with the pusher props too, since the
fuselage also masks the area near the hub in that instance too.

What is bad is the prop passing through the two downwash area's and in
some cases the column of exhaust from the engine. Remember me saying
that in the P-51 the area of the wing within the turbulence from the
prop was non laminar due to the turbulence? Well think about what's
happening to the airflow around the prop when it whaps through the
downwash from each of the wings. And it's the entire prop that passes
through this downwash.

I agree that during takeoff, this affect would be minimised, at least
until lift off, then the airplane would be producing maximum lift,
which means the prop would be passing through the strongest downwash
off the wings that it ever encounters.

So if you managed somehow to fit your engine in front of your SQ, I'm
guessing that performance would be virtually identical. Well mayby
not, it might takeoff quicker because you'll be able to lift the nose
to get a higher angle of attack sooner. It's the tiny size of the
fuselage the minimal wetted area and the smoothness of the surfaces
and finish, plus the laminar design of the airfoils that give Rutan's
designs their performance, not necessarily the rear placement of the
engine.

The airplane with the lowest coeficient of drag ever recorded was a
tractor design, albeit a small one. :-)

Corky Scott

[Paul Lee]

wrote in message >...
> On 3 May 2004 16:11:01 -0700, (Paul Lee) wrote:
> .............
> The airplane with the lowest coeficient of drag ever recorded was a
> tractor design, albeit a small one. :-)
>
> Corky Scott

Scott,

Lowest CD very much depends on the design. There are "many" tractor
designs and much fewer pusher ones to compare to. But really overal
CD of a body has little to do with pusher/tractor prop effectivenes
issue here. I think a good way to settle this is to put a model
tractor body in a wind tunel and then reverse the same thing and
test it as a pusher. Anybody's got a spare wind tunel and lots of time?

[[email protected]]

On 4 May 2004 20:09:32 -0700, (Paul Lee) wrote:

>Lowest CD very much depends on the design. There are "many" tractor
>designs and much fewer pusher ones to compare to. But really overal
>CD of a body has little to do with pusher/tractor prop effectivenes
>issue here. I think a good way to settle this is to put a model
>tractor body in a wind tunel and then reverse the same thing and
>test it as a pusher. Anybody's got a spare wind tunel and lots of time?

I didn't make myself clear enough, sorry. What I meant to say was
that pusher or tractor, the plusses and minuses pretty much cancel
themselves out. One can optimize a pusher to make it a really
efficient airplane, or optimize a tractor to do the same. I doubt you
will find enough differences in the performance of such machines to
measure.

Corky Scott

[alexy]

(Paul Lee) wrote:
>I think a good way to settle this is to put a model
>tractor body in a wind tunel and then reverse the same thing and
>test it as a pusher. Anybody's got a spare wind tunel and lots of time?

Or, if one is looking to "prove" the opposite result, put a model
pusher body in a wind tunnel and then reverse the same thing and
test it as a tractor! <g>
--
Alex
Make the obvious change in the return address to reply by email.

[George A. Graham]

On Wed, 5 May 2004, alexy wrote:

> (Paul Lee) wrote:
> >I think a good way to settle this is to put a model
> >tractor body in a wind tunel and then reverse the same thing and
> >test it as a pusher. Anybody's got a spare wind tunel and lots of time?
>
> Or, if one is looking to "prove" the opposite result, put a model
> pusher body in a wind tunnel and then reverse the same thing and
> test it as a tractor! <g>
> --

Actually, this question has been answered.

The Cessna SkyMaster has both a pusher and a tractor engine.
The single engine climb rate and speed are both higher for the
rear engine alone, than for the front engine alone.

The pusher wins!

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[Morgans]

"George A. Graham" > wrote >
> Actually, this question has been answered.
>
> The Cessna SkyMaster has both a pusher and a tractor engine.
> The single engine climb rate and speed are both higher for the
> rear engine alone, than for the front engine alone.
>
> The pusher wins!
>
> George Graham

Actually, no. One would have to test without the prop on the non-operating
engine and with the cooling inlets streamlined. With the dead engine prop
still on, it is largely a test on which position has less drag than the
other.
--
Jim in NC


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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[Big John]

George

The rear engine on a 337/0-2 sucks air at high velocity over the
center section of the wing giving bird more lift which of course you
can use any way you want.

Big John
`````````````````````````````````````````````````` ``````````````````````````````

On Wed, 5 May 2004 12:33:42 -0400, "George A. Graham" >
wrote:

>On Wed, 5 May 2004, alexy wrote:
>
>> (Paul Lee) wrote:
>> >I think a good way to settle this is to put a model
>> >tractor body in a wind tunel and then reverse the same thing and
>> >test it as a pusher. Anybody's got a spare wind tunel and lots of time?
>>
>> Or, if one is looking to "prove" the opposite result, put a model
>> pusher body in a wind tunnel and then reverse the same thing and
>> test it as a tractor! <g>
>> --
>
>Actually, this question has been answered.
>
>The Cessna SkyMaster has both a pusher and a tractor engine.
>The single engine climb rate and speed are both higher for the
>rear engine alone, than for the front engine alone.
>
>The pusher wins!
>
>George Graham
>RX-7 Powered Graham-EZ, N4449E
>Homepage <http://bfn.org/~ca266>

[jls]

"Big John" > wrote in message
...
> George
>
> The rear engine on a 337/0-2 sucks air at high velocity over the
> center section of the wing giving bird more lift which of course you
> can use any way you want.
>
> Big John
>
`````````````````````````````````````````````````` ``````````````````````````
````

Ah, my lilliputian friend, not enough air to cool the engine, though, since
Vietnam era 02's all got fried rear engines.

[George A. Graham]

On Wed, 5 May 2004, Morgans wrote:

> > The pusher wins!
> >
> Actually, no. One would have to test without the prop on the non-operating
> engine and with the cooling inlets streamlined. With the dead engine prop
> still on, it is largely a test on which position has less drag than the
> other.
> --
> Jim in NC

Wow what a response! How are things in Mayberry Barney?

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[Big John]

jls

Flew an 0-2 for a year in VN. FAC'd in bird and also used as light
transport to support my Sector FAC's in II Corps.

1.Never lost an engine.
2. Never fried a rear engine.
3. Never heard about any frying.

Have always babied my engines.
If I would have needed to fry one to save my ass, would have done so
and never looked back.

Big John


On Thu, 6 May 2004 07:49:01 -0400, " jls" >
wrote:

>
>"Big John" > wrote in message
...
>> George
>>
>> The rear engine on a 337/0-2 sucks air at high velocity over the
>> center section of the wing giving bird more lift which of course you
>> can use any way you want.
>>
>> Big John
>>
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>Ah, my lilliputian friend, not enough air to cool the engine, though, since
>Vietnam era 02's all got fried rear engines.
>