zero fuel w & b

in my PPL training it was drummed in to me the importance of always doing
the w & b calcs with the fuel you were taking and also the zero fuel case.
I posted sometime ago that with the Warriors I flew it was impossible to go
outside the w & b envelope by burning fuel. I have just finished my
transition to the C172 and have extensively investigated different loading
scenarios and found exactly the same thing, at least with this N model I am
flying.
Are there any single engine airplanes out there that really can go outside
the envelope by burning fuel? ( I am only interested in the normal
ategory - not utility). Perhaps the training is just to prepare you for
heavy aircraft?
Terry
PPL downunder

"d&tm" wrote in message
...
[...]
Are there any single engine airplanes out there that really can go outside
the envelope by burning fuel?

Sure. Any airplane in which the CG moves as fuel is burned has that
potential, depending on what other aspects of loading exist.

I haven't looked at the 172 case recently. Possibly due to weight
restrictions for baggage or seats you can't load it close enough to the
critical end of the CG range with full fuel for the CG to move outside the
range by using up fuel? I don't know off the top of my head.

What I do know is that I own a single-engine airplane (Lake Renegade) that
can wind up with the CG out of range after fuel has burned. I also know
from my friends who own Bonanzas that at least some models of Bonanza have a
similar issue. I am sure there are a number of smaller single-engine
airplanes that have the same requirement to pay close attention to weight &
balance.

Of course, there's a difference between the potential for problems
generally, and the potential for problems with specific loadings. Generally
speaking, I've found that the issue of CG moving out of range with fuel burn
still only happens in specific loading configurations. For example, in my
airplane the issue is most pronounced when the airplane is heavily loaded to
start with, and when that weight is mostly up front. Even at higher
weights, there are loading configurations that are generally assured to not
wind up outside the CG range as fuel burns.

As long as you've done enough W&B calculations to check the various
configurations and be very familiar with how the CG moves according to
loading and fuel, then to some extent it's not necessary to do a full W&B
calculation for every flight, assuming you've otherwise ensured you're not
overweight and have a loading configuration for which fuel burn isn't an
issue.

But, it's certainly not safe to say that one need not worry about fuel burn
for single-engine airplanes, even if you limit that statement to the smaller
ones (two- and four-seat).

Pete

d&tm wrote:

in my PPL training it was drummed in to me the importance of always doing
the w & b calcs with the fuel you were taking and also the zero fuel case.
I posted sometime ago that with the Warriors I flew it was impossible to go
outside the w & b envelope by burning fuel. I have just finished my
transition to the C172 and have extensively investigated different loading
scenarios and found exactly the same thing, at least with this N model I am
flying.
Are there any single engine airplanes out there that really can go outside
the envelope by burning fuel? ( I am only interested in the normal
ategory - not utility). Perhaps the training is just to prepare you for
heavy aircraft?
Terry


Bonanza's come immediately to mind.
I do not know if the current models are built this way, the older models
had the fuel stored in the front of the wing, ahead of the main spar.
Any weight in the aircraft behind the front seats is behind the fuel
weight. As fuel is burned, the weight ahead of the spars decreases while
the weight behind the spar remains the same, hence the cg moves aft. At
some point, the cg moves out of the envelope (the ability of the
horizontal stabilizer to provide sufficient lift).
Piper PA32's will can also develope this situation.
Cessna's seem to have a broader range.
You have to look at each aircrafts envelope.

Van's tandem seat RV-4's had a bad string of fatal accidents until the
word got out and builders became more aware of the potential danger.

"d&tm" wrote in message ...
: in my PPL training it was drummed in to me the importance of always doing
: the w & b calcs with the fuel you were taking and also the zero fuel case.
: I posted sometime ago that with the Warriors I flew it was impossible to go
: outside the w & b envelope by burning fuel. I have just finished my
: transition to the C172 and have extensively investigated different loading
: scenarios and found exactly the same thing, at least with this N model I am
: flying.
: Are there any single engine airplanes out there that really can go outside
: the envelope by burning fuel? ( I am only interested in the normal
: ategory - not utility). Perhaps the training is just to prepare you for
: heavy aircraft?
: Terry
: PPL downunder
:

Cherokee 6 comes to mind right away...

"Peter Duniho" wrote in message
...
"d&tm" wrote in message
...
[...]
Are there any single engine airplanes out there that really can go
outside
the envelope by burning fuel?

Sure. Any airplane in which the CG moves as fuel is burned has that
potential, depending on what other aspects of loading exist.


Both the Warrior and the C172 c of g moves forward with fuel burn but so
does the allowable limit, at the same or greater rate, which is why it is
not possible to go outside the envelope under any loading conditions.

I haven't looked at the 172 case recently. Possibly due to weight
restrictions for baggage or seats you can't load it close enough to the
critical end of the CG range with full fuel for the CG to move outside the
range by using up fuel? I don't know off the top of my head.



What I do know is that I own a single-engine airplane (Lake Renegade) that
can wind up with the CG out of range after fuel has burned. I also know
from my friends who own Bonanzas that at least some models of Bonanza have
a
similar issue. I am sure there are a number of smaller single-engine
airplanes that have the same requirement to pay close attention to weight
&
balance.

Of course, there's a difference between the potential for problems
generally, and the potential for problems with specific loadings.
Generally
speaking, I've found that the issue of CG moving out of range with fuel
burn
still only happens in specific loading configurations. For example, in my
airplane the issue is most pronounced when the airplane is heavily loaded
to
start with, and when that weight is mostly up front. Even at higher
weights, there are loading configurations that are generally assured to
not
wind up outside the CG range as fuel burns.

As long as you've done enough W&B calculations to check the various
configurations and be very familiar with how the CG moves according to
loading and fuel, then to some extent it's not necessary to do a full W&B
calculation for every flight, assuming you've otherwise ensured you're not
overweight and have a loading configuration for which fuel burn isn't an
issue.

this is basically why I do the analysis, to break it down to simple rules
that will not require me to have to do the c of g calcs each time.
conclusion with the C172N is that, with the weight restrictions satisfied
1. it is impossible to get c of g too far forward.
2. the only way to have c of g too far back is with more weight in back seat
than front. ( most unlikely situation for me)
3. it is impossible to go outside by burning fuel.
So my simple rule becomes stay within the wt constraints and do a c of g
check only if I want more wt in the back seat than the front. - which is
likely to be never.

But, it's certainly not safe to say that one need not worry about fuel
burn
for single-engine airplanes, even if you limit that statement to the
smaller
ones (two- and four-seat).

I certainly wouldnt assume that without doing the same analysis on the
particular aircraft. It seems to me that the aircraft I have referred to (
warrior and C172N) are probably designed so that fuel burning will not cause
an adverse c of g . I would also be curious to know if other models of C172
or the higher performacne C177, C182 C206, C210 follow the rules I outlined
above.
Excuse my ignorance but I hadn't heard of a Lake Renegade, but I did do a
google and note that it is a beautiful looking amphibious aircraft whch
obviously has some specific design characeristics for its intended
application, namely an engine above and behind the cabin, which makes it a
little different from the aircraft I am likely to fly, but I take your point
that fuel burning may be an issue in some small planes.
terry
PPL downunder

this is basically why I do the analysis, to break it down to simple rules
that will not require me to have to do the c of g calcs each time.

Try this - start at the bottom of the envelope, and pretend that each
corner represents a zero fuel loading. Then add fuel and see where you
end up. Draw that line on the envelope. The inner envelope is defined
as the the most restrictive envelope from all these lines and the
existing envelope. So long as your loading (with fuel) is within this
inner envelope, you'll be ok to zero fuel. (at least w&b wise.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

john smith wrote:




Bonanza's come immediately to mind.
I do not know if the current models are built this way, the older models
had the fuel stored in the front of the wing, ahead of the main spar.
Any weight in the aircraft behind the front seats is behind the fuel
weight.

In my 64 S35 all weight in the plane is behind the fuel. The fuel is at
75 and the front seats are at 85. Rear seats 121 and baggage at 150.

Newps wrote:

john smith wrote:

Bonanza's come immediately to mind.

I do not know if the current models are built this way, the older
models had the fuel stored in the front of the wing, ahead of the
main spar. Any weight in the aircraft behind the front seats is
behind the fuel weight.


In my 64 S35 all weight in the plane is behind the fuel. The fuel is
at 75 and the front seats are at 85. Rear seats 121 and baggage at 150.

Any idea where front seats are in the 36 series?

Same place. Although the fuel is the same arm as the front seats in the 36.





john smith wrote:



Newps wrote:

john smith wrote:

Bonanza's come immediately to mind.

I do not know if the current models are built this way, the older
models had the fuel stored in the front of the wing, ahead of the
main spar. Any weight in the aircraft behind the front seats is
behind the fuel weight.



In my 64 S35 all weight in the plane is behind the fuel. The fuel is
at 75 and the front seats are at 85. Rear seats 121 and baggage at 150.


Any idea where front seats are in the 36 series?

"john smith" wrote in message
...
d&tm wrote:

in my PPL training it was drummed in to me the importance of always doing
the w & b calcs with the fuel you were taking and also the zero fuel case.
I posted sometime ago that with the Warriors I flew it was impossible to
go
outside the w & b envelope by burning fuel. I have just finished my
transition to the C172 and have extensively investigated different
loading
scenarios and found exactly the same thing, at least with this N model I
am
flying.
Are there any single engine airplanes out there that really can go outside
the envelope by burning fuel? ( I am only interested in the normal
ategory - not utility). Perhaps the training is just to prepare you for
heavy aircraft?
Terry


Bonanza's come immediately to mind.
I do not know if the current models are built this way, the older models
had the fuel stored in the front of the wing, ahead of the main spar. Any
weight in the aircraft behind the front seats is behind the fuel weight.
As fuel is burned, the weight ahead of the spars decreases while the
weight behind the spar remains the same, hence the cg moves aft. At some
point, the cg moves out of the envelope (the ability of the horizontal
stabilizer to provide sufficient lift).
Piper PA32's will can also develope this situation.
Cessna's seem to have a broader range.
You have to look at each aircrafts envelope.

Van's tandem seat RV-4's had a bad string of fatal accidents until the
word got out and builders became more aware of the potential danger.

It is true that the CG moves aft with fuel burn on all of the 2 place Van's
designs. It is also true that depending on the individual aircraft and the
loading that you could run the CG beyond the aft limit. You certainly can
in my RV-6. That said, please do some fact checking before you conjure up a
"bad string of fatal accidents" for RV-4's due to CG issues. Didn't happen.
There was one accident in the NTSB database between 1980 and today where CG
was listed as a factor...

Not jumping your kimchee or anything, but facts are facts, and making 'em up
(or remembering 'em incorrectly) isn't a good idea when safety is at issue.

KB