New Cherokee 140 owner, W&B "problem"

tawood said:
But, with 4 different weight and balances, from 4 different places, over 40 years, all showing the same weight + or - 20 lbs and a CG + or - a 1/2 inch...and with a current 1277 lbs empty weight...I don't know, and I'm also starting not to care.
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Well, you may not care now. But here's a funny story. While researching the old W&Bs that I saved over the years (hurray paper - see if you iPad can do that) I found something curious. At a certain FBO X they had 2 Piper Cherokee airplanes A (1966) and B (1968), which passed through significant modifications, were re-weighted etc. So, at a certain moment, A and B ended having identical documented W&B data, down to 1/100th of a pound and 1/100th of an inch. What are the chances? Sure, they are both Cherokees with overhead crank, but... I am almost certain that someone reused paperwork for airplane A in airplane B. Unfortunately, airplane B was lost 2 years ago. A student pilot on his first solo made a go-around from 20 ft over the runway, lost directional control, and flew into a hangar (spoiler: he survived with superficial injuries, airplane was completely destroyed). So I cannot visit them and check the current paperwork. And I'm not implying that airplane was so nose-heavy that a solo student could not manage it. That would be laughable. Still, amazing things happen with W&B sheets. BTW, FBO X a Part 141 school that receives an elevated scrutiny from local FSDO.
 
tawood said:
But, with 4 different weight and balances, from 4 different places, over 40 years, all showing the same weight + or - 20 lbs and a CG + or - a 1/2 inch...and with a current 1277 lbs empty weight...I don't know, and I'm also starting not to care.
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If by "4 different weight and balances" you mean 4 different weighings on scale, then I would agree with you and not care about the difference from stock. Well, I would care. A lot. I would be HAPPY. :) The stock CG sucks.
 
so, i have a question.

the front seat is adjustable, and per the poh the arm is 85.5. the back seat has an arm of 117. there is not 31 inches from the middle of the seat when fully aft and the center of the back seat.

so, my question is, where did they get the arm from, the front, middle or back of the seat track. if the passenger seat is moved fully aft wouldnt that change the arm. a 4 inch change aft in the front seats makes a huge differance with two good size fella’s in the front
 
ncemt said:
so, i have a question.
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I, too, have a question. Would the arm possibly be the average given the seat track length and weight of the installed equipment (seat, seat belts, etc)? Or do you think the full weight of a seat occupant comes to bare at the front most, or rear most, attach point?
 
Ravioli said:
I, too, have a question. Would the arm possibly be the average given the seat track length and weight of the installed equipment (seat, seat belts, etc)? Or do you think the full weight of a seat occupant comes to bare at the front most, or rear most, attach point?
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Wherever his belt buckle is.
 
Errors in arithmetic are the most common cause of cg puzzles. Even a reweigh is no guarantee if the math isn't done right or the airplane isn't properly leveled as per manuals or the unusable fuel isn't as specified or the wheel positions aren't accurately measured.
 
ncemt said:
where did they get the arm from, the front, middle or back of the seat track.
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FWIW: Usually if a seat is adjustable there will be arm measurements stated for most forward/most aft seat positions in addition to an arm for an "average" person position. These values are usually found in the POH/AFM, or TCDS, or as a supplement page if the adj seats are an option. In most cases the measurement is taken from the datum to a point in the middle of the seat bottom which is the same method used for cargo/baggage areas. Some people use their own reference point once the fore/aft seat limits are known.
 
From my decade long experience I can say the it isn’t easy to get a Pa140 out of CG. They’re marvelously forgiving. The only thing I’ve encountered is if you have a pair of really big people in the front seats. But if they actually physically fit and you’re within gross, it manifests as having trouble keeping the nose wheel off in the flair. Even that can be alleviated with a heavy flight bag or case of oil in the luggage bay.
 
well, when i was loading airplanes in the Air Force when you did the weight and balance form F for anything placed in the c-130 before flight like a truck, tank, or pallet. the center of gravity was the arm used, has nothing to do so much with the attachment point. i agree the seat belt in your lap is probably pretty close your actual cg, which is why i asked, the POH gives you a set number for the front seat, 85.5 and 117 for the back seat. the seat is adjustable but no range is given. My gut feeling that its from the most forward position because thats the worst case scenario and my guess without putting a tape to it is pretty close to 31inches .. but i was hoping someone had an actual answer with something to back it up.
 
JustinD said:
Someone please correct me if I'm wrong but doesn't an aircrafts w&b already take into account all fluids (i.e. oil, hydraulics) including non-useable fuel?
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Usually non usable fuel. Depends.
Sometimes oil. Sometimes not.
I assume hydraulic fluid could go either way depending on the aircraft - does it carry 20 gallons, or a pint?
 
ncemt said:
My gut feeling that its from the most forward position
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FYI: In my experience, if you can not find the arm range for an adjustable seat then the seat arm value they state is 99.9% the measurement to middle of the adjustment range. Considering this is of concern to you, perhaps get that tape measure out or call Piper Tech Support to verify the answer you seek.;)
 
I found in another post an faa ac ACE-97-02 showing 80.5 to 90.5, so your middle is dead on, thanks.
 
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