Tie Down Trouble

"A Lieberman" wrote
On my IFR checkride, I had to show my numbers for weight and balance.

470 pounds of meat in the front seats *required* 100 pounds in the baggage
department with full tanks. I elected to put in 75 pounds (yes, I brought
barbell weights) and account for fuel burn off to keep me in CG.

So, you had to take off out of CG, right? Fuel burn on the taxi and run-up
could not account for that much, right?

Is the landing CG range different from the take-off CG?

Just curious. :-)
--
Jim in NC

On Wed, 17 May 2006 20:25:30 -0400, Morgans wrote:

"A Lieberman" wrote
On my IFR checkride, I had to show my numbers for weight and balance.

470 pounds of meat in the front seats *required* 100 pounds in the baggage
department with full tanks. I elected to put in 75 pounds (yes, I brought
barbell weights) and account for fuel burn off to keep me in CG.

So, you had to take off out of CG, right? Fuel burn on the taxi and run-up
could not account for that much, right?

Is the landing CG range different from the take-off CG?

Just curious. :-)

Hmmm, never did a comp landing vs takeoff. Knowing the flight was going to
be 2 to 2 1/2 hours long, figured a forward CG of 25 pounds, that would be
lost rather quickly on taxi, runup and takeoff.

DE had no problem with my rational, so I don't think I was "unsafe" in
doing what I did. I weigh 190, and he was 280, and this is by far the most
meat I had in the front row, so I knew W&B would be critical.

With just me in the front seat and full tanks, I would need some ballast in
the back, that's how narrow the envelope is. While I have 30 pounds in the
back with oil, 25 pound barbell and the like, I felt like adding 100 pounds
seemed almost wacko, but the book said to do so.

My thoughts were that I would be burning off 120 pounds of fuel, so the CG
would shift gradually back. I didn't want to be far aft CG if my flight
went much longer, and as it turned out, it was 2 1/4 hours.

I guess my thoughts were that after the fuel burn off from the test, that I
would be aft CG had I stuck with 100 pounds, so I kinda compromised with
the "known" slight forward CG on take off rather then end up with an
unknown aft CG after 2 hour flight.

Bottom line is you are correct, in that flight, I should have figured both
the take off CG and landing CG to ensure that the W&B truly balanced.

That envelop for W&B in my Sundowner is a very narrow window.

Allen

Morgans wrote:


Is the landing CG range different from the take-off CG?

Possibly, yes.

On the Sundowner, the CG heads slightly aft as fuel is burned off AND a
more forward CG is allowed at lighter weights.

A Lieberman wrote:

My thoughts were that I would be burning off 120 pounds of fuel, so the CG
would shift gradually back. I didn't want to be far aft CG if my flight
went much longer, and as it turned out, it was 2 1/4 hours.


Study your POH for the forward limit. At lighter gross weights, it
moves substantially forward. For a real shocker, look at the limits in
Utility and Acrobatic category.


Bottom line is you are correct, in that flight, I should have figured both
the take off CG and landing CG to ensure that the W&B truly balanced.

That envelop for W&B in my Sundowner is a very narrow window.

Not true on ours (a '76 C23-180). It's very difficult, in fact nearly
impossible with full fuel and a typical male pilot, to make that plane
tail heavy and still be under max gross. Only the forward limit is a
pain. That plane LOVES rear seat pax.

On our own, we've flown ours out of limits forward. It still rotates
well off the runway, trims out nice, recovers from stalls, and handles
well. The real effect is stabilator authority in slow flight, which
could cause a pilot to run out of flare during a landing. At a lower
gross, you need less pressure on the stabilator, hence the substantially
more forward CG limit.

I suggest always flying by your POH, this is for discussion and
educational purposes only.

Are you a BAC member? They have some incredible expertise with the
Sundowner, Sierra, Musketeer series of airplanes, including folks who
were actually there during the FAA certification processes.

There is no way to load our 74 Archer into the utility category with any
fuel on board. Even with a 95 lb pilot only, and no fuel, the cg is right
at the aft edge of the utility envelope. OTOH, it's almost impossible to
get the cg too far aft in the normal category and still be below gross.

--
Bob (Chief Pilot, White Knuckle Airways)


"B A R R Y" wrote in message
. com...
A Lieberman wrote:

Study your POH for the forward limit. At lighter gross weights, it moves
substantially forward. For a real shocker, look at the limits in Utility
and Acrobatic category.

I once hear about a guy that flew a C210 cross country with a tail tie down
bucket of concrete attached. at destination he was asked how it flew. he
said " well about like a bonanza" For who don't know the Bonanza wiggles in
turbulent air.

"Dylan Smith" wrote in message
...
At some airfields, you get tiedowns in the grass that consist of some
kind of weight (such as a concrete block or tire filled with concrete)
and a tiedown. Perhaps they aren't much use -- a plane apparently can
still fly with one attached to the tail.

In this month's 'Pilot' magazine (British) under Safety Matters:

Tiedown attached
----------------
AS A BEECH C23 Sundowner took off from Aldergrove, ATC saw an object
dangling from the tail. It was a car tyre filled witih concrete which
has been used as a tie down. The pilot landed safely after a normal
circuit.
During the pre-flight inspection, the pilot had removed tie-down weights
attached to the wings, but hadn't noticed the weight attached to the
tail.

I have to imagine the flight characteristics of a Sundowner with 50lbs
of concrete hanging off the tail had to be 'squirrely'!
--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

Bob Chilcoat wrote:
There is no way to load our 74 Archer into the utility category with any
fuel on board. Even with a 95 lb pilot only, and no fuel, the cg is right
at the aft edge of the utility envelope. OTOH, it's almost impossible to
get the cg too far aft in the normal category and still be below gross.

cherokee 180 model D (1969).
Me, aircraft & fuel to tabs: just right of the utility category. the only
way into the utility cat. is with 20 gal of fuel and no one in the aircraft.

me, aircraft, full fuel, big bruiser in the copilot seat -- need 50 lbs of
ballast in the baggage.

I've got a 7 gal. water carrier (one of the those bright blue plastic
square things) that has about 50 lbs (maybe a bit less?)

4 FAA people (175 @) and full fuel -- ramp weight is exactly POH limit,
but the CG is slightly outside the limits.

4 FAA people, fuel to tabs -- life is good everywhere. But I won't be
able to takeoff until October due to density altitude.

3 FAA people, full fuel, 50# in the baggage -- just inside CG range.