zero fuel w & b

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

"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

As the wife and kids move around, I do need to re-trim -- but I haven't
casually noted a significant speed increase. I'll have to recruit some
'hefty' passengers and perform the experiment (our last experiment was
for my son's 5th grade science class when we capped empty water bottles
at various altitudes and he showed the class how much the bottles
collapsed as we returned to the ground).


Morgans wrote:
"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.

"Steve Schneider" wrote in message
...
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, thanks for that. I have made up similar spreadsheets for the Warrior
and C172 , but perhaps a little fancier in that they are set up to select
different reg numbers from a drop down menu, with the specific aircraft
data ( useful for paupers like me who dont own their own plane), a clear
button to clear all the input data and a message box to warn if any of the
fuel, baggage or total wt restrictions are exceeded. But I like your idea
of showing the low fuel point ( rather than just deleting the fuel as I do)
I think I will steal this idea :)
As I said in my previous post, it would be very unusual for me to have more
wt in the back than the front, ( which is likely to test the aft cg ) but
I could understand with club seating, the pax might be more inclined to want
to ride in style, instead of up the front.with the driver.

I notice even your 6 seater would struggle to take 4 adults with full fuel.
( the adutls would have to weigh on average less than 180 lbs - counts out
a lot of my friends!
Terry
ppl downunder

d&tm wrote:

Steve, thanks for that. I have made up similar spreadsheets for the Warrior
and C172 , but perhaps a little fancier in that they are set up to select
different reg numbers from a drop down menu, with the specific aircraft
data ( useful for paupers like me who dont own their own plane), a clear
button to clear all the input data and a message box to warn if any of the
fuel, baggage or total wt restrictions are exceeded. But I like your idea
of showing the low fuel point ( rather than just deleting the fuel as I do)
I think I will steal this idea :)
As I said in my previous post, it would be very unusual for me to have more
wt in the back than the front, ( which is likely to test the aft cg ) but
I could understand with club seating, the pax might be more inclined to want
to ride in style, instead of up the front.with the driver.

I'll have to dust off an Excel manual and polish up my spreadsheets with
some of your cool features! :-)

I notice even your 6 seater would struggle to take 4 adults with full fuel.
( the adutls would have to weigh on average less than 180 lbs - counts out
a lot of my friends!
Terry
ppl downunder


True, though full tanks would far exceed the typical passenger's bladder
range. Half tanks would still yield over 2 hours of flying time with
reserves (close enough to the upper end of the random passenger's
comfort limit per my experience) and let you carry a 5th person plus a
bit of baggage some 300+nm.

The Lance is by far the most practical aircraft I've ever had the
pleasure to fly. As a coincidental but random trip example, we're
heading off tomorrow to Santa Barbara with a full load of 6 people to
make good on a trip we donated for an event at a local community
college. This will be my wife and I plus 4 people who won the drawing.
Fortunately, the passenger weights are a bit on the low side, so with
partial fuel we can fly the ~300 mile round trip with fuel to spare. It
always seems like our passenger load works out pretty well.

One of the advantages of being a sole owner/operator is that you don't
have to worry about the prior pilot/partner/club member topping off the
tanks when you need to fly with partial fuel. I'd sure hate to drain 40
or 50 gallons before a flight because someone forgot _not_ to top off,
or perhaps the prior scheduled flight didn't occur so the tanks are
still full from the flight before that one.

Steve

I'll have to dust off an Excel manual and polish up my spreadsheets with some of your cool features! :-)

You might also want to take a look at the one I did for our club.

http://www.flying20club.org/planes8237B.html

I did the "new style" spreadsheet a little differently from the others,
take a look at the "how the spreadsheet works" part of the instructions tab.

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

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

snip
At some point, the cg moves out of the envelope (the ability of the
horizontal stabilizer to provide sufficient lift).

Aft c.g. violation makes the aircraft unstable in pitch. Forward c.g.
violation is an ability of the stabilizer to control pitch, i.e. bring the
nose up.

Danny Deger

"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...

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