zero fuel w & b

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.

Kyle, I have personal knowledge of four, and first hand reports from
others in the RV community. The rash of accidents happened in the late
80's/early 90's. They were the basis for Van revising the aft cg limit
on RV-4's Just because the NTSB doesn't list it doesn't mean they didn't
happen. I also know of other NTSB final reports where the report did not
match the facts. You have to understand that the NTSB does not
investigate all accidents. In most cases, they take the information from
another agency and synthesize the results.

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.

Which is amusing, because most flight instructors have never flown an
airplane where this is actually necessary.

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.

No surprise. I can't think of any trainer where this would be true.

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?

Well, not so much heavy as optimized. The trainers you are used to
flying are not really optimized for performance - they are built to be
simple to maintain, rugged enough to take the training regime, and easy
to fly. They have pretty wide cg envelopes, and it's pretty hard to
get into W&B trouble unless you really overload.

Move into something like a V-tail Bonanza, and it's a different game.
The cg range is narrow (due in large part to limited empennage control
- it's a lot wider in the straight tails) and the fuel is way forward
so as you burn it, the cg moves aft - and can easily take you out of
limits. They do it that way for a reason. The V-tail is less draggy.
Keeping the cg close to the aft limit reduces the required downforce
from the tail, and thus the extra lift the wing must generate to
counter it. Generating lift also generates drag, so you get a more
efficient airplane. That's important, because big gains in speed are
made by improving aerodynamic efficiency, not increasing engine power.

Here's something to think about. The Warriors and Skyhawks you fly are
realistically 110 kt airplanes on a good day. They make it happen with
4 seats and 160 hp. Remember that power required goes up with the cube
of airspeed - in other words, making a plane with the same aerodynamics
fly 160 kts would require almost 500 hp. When you see a four seater
doing 160 kts on half that horsepower (as the early Bonanzas did) you
need to ask yourself - what was traded off to get that speed? Where
will I have to work harder, where will I have less margin for error?
In the case of the V-tail Bonanza, the narrow cg (and consequently the
worry about getting out of cg as you burn fuel) is part of the answer.

Hope that makes it all clearer.

Michael

I fly a homebuilt Savannah (there are quite a few flying in Oz) and if
the pilot weighs less than about 120 pounds, and the fuel is nearly
exhausted, the CG is just slightly forward of the envelop.
tom

d&tm wrote:
Are there any single engine airplanes out there that really can go outside
the envelope by burning fuel?
Terry
PPL downunder

d&tm wrote:

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?

I believe Bonanzas can have this problem in certain configurations.

It depends on which where the CG is. If you've got an aft CG
and burning fuel drives it more aft, you've got problems.

In my plane, we typically sit on the forward CG limit with
the tanks full. Since the envelope is sloped on the forward
CG side (the limit moves aft as you go up in gross weight),
even as the CG moves forward with fuel burn, you're also
getting lighter so the CG limit is moving forward faster.

"Ron Natalie" wrote in message
...
d&tm wrote:

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?

I believe Bonanzas can have this problem in certain configurations.

It depends on which where the CG is. If you've got an aft CG
and burning fuel drives it more aft, you've got problems.

In my plane, we typically sit on the forward CG limit with
the tanks full. Since the envelope is sloped on the forward
CG side (the limit moves aft as you go up in gross weight),
even as the CG moves forward with fuel burn, you're also
getting lighter so the CG limit is moving forward faster.

Similar to the Warrior. but you can barely get enough wt in the front to
reach the forward limit. expecially when I am one of them ( 180 lbs). But
it is just possible with a couple of sumu wrestlers and less than full fuel
to exceed the forward limit, in this case burning fuel actually brings you
back in bacause as you say the cg moves forward but the limit moves forward
faster at lower wt.
What is your plane John?
terry
PPL downuder

"tom" wrote in message
oups.com...
I fly a homebuilt Savannah (there are quite a few flying in Oz) and if
the pilot weighs less than about 120 pounds, and the fuel is nearly
exhausted, the CG is just slightly forward of the envelop.
tom

Tom, do you carry some ballast to correct this? I know nobody plans to run
out of fuel but if it happened , say from a fuel leak, I would hate to be
worrying about an off field landing with a forward cg.
terry




d&tm wrote:
Are there any single engine airplanes out there that really can go
outside
the envelope by burning fuel?
Terry
PPL downunder

john smith wrote:
d&tm wrote:

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

Piper PA32's will can also develope this situation.


I'd previously posted links for some weight and balance info for a few
aircraft I've flown over the years. One of them happens to be a PA32.
This link http://www.4-fs.com/new/flying/N3000AWB.xls is to the W&B
spreadsheet for the Piper Lance (PA32-RT300T) which we've been flying
the last few years. I had included variables for fuel at departure and
'low fuel' for landing for just this reason. You can plug in the
following plausible values for a real flight and end up with the CG in
range (though precariously aft) at the start of the flight and have the
CG aft of the limits with 15 gallons remaining at the end of a flight:

Pilot+no front passenger: 180 lb
Center Passengers: 0
Rear Passengers: 360 lb
Fuel: 94 gal
Front Baggage: 0
Rear Baggage: 90

The CG only moves 0.22 inches to the rear after burning 79 gallons of
fuel, but it does take you 0.20 inches past the aft CG limit during the
flight.

Flying this plane with club seating does allow for some interesting
weight shifting when passengers (wife and kids typically) swap seats in
flight. You definitely do feel the change, and as such I always keep in
mind which passengers sit in which seats. Imagine the above loading
with the rear passengers (2x180lb) in the center row of seats and the
rear seats empty. Once airborne they decide they don't like to fly
'backwards' in the club seating and 'help themselves' to the the empty
rear seats. Suddenly we go from a very comfortable CG to a precariously
aft CG. Not a situation one generally needs to worry about in 2 and 4
seat airplanes.

That is part of why I find these spreadsheets so helpful in quickly
looking at a bunch of 'what if' scenarios before we depart.

Steve

I weigh 170, so the only ballast I carry is around my ass. 8^)
tom

d&tm wrote:
"tom" wrote in message
oups.com...
I fly a homebuilt Savannah (there are quite a few flying in Oz) and if
the pilot weighs less than about 120 pounds, and the fuel is nearly
exhausted, the CG is just slightly forward of the envelop.
tom

Tom, do you carry some ballast to correct this? I know nobody plans to run
out of fuel but if it happened , say from a fuel leak, I would hate to be
worrying about an off field landing with a forward cg.
terry

"Steve Schneider" wrote

Flying this plane with club seating does allow for some interesting weight
shifting when passengers (wife and kids typically) swap seats in flight.
You definitely do feel the change, and as such I always keep in mind which
passengers sit in which seats. Imagine the above loading with the rear
passengers (2x180lb) in the center row of seats and the rear seats empty.
Once airborne they decide they don't like to fly 'backwards' in the club
seating and 'help themselves' to the the empty rear seats. Suddenly we go
from a very comfortable CG to a precariously aft CG. Not a situation one
generally needs to worry about in 2 and 4 seat airplanes.

With the passengers putting the CG at the most aft limits, do you notice any
increase in speed, with the same power and prop settings? I would think the
aft CG would take the downward lift away from the horizontal, and pick up
some speed, but I don't know. It would seem like the ideal experiment; to
be able to quickly change the CG with no changes in air density, power, or
any other type of changes.
--
Jim in NC

"tom" wrote in message
oups.com...
I weigh 170, so the only ballast I carry is around my ass. 8^)
tom

"Does this airplane make me look fat...?"

;O)

Jay B