C of G issues
 

Yesterday I did my first long x-country in GKEY. We flew from Cold Lake (Alberta) to Brandon (Manitoba) and back. Total time 6 hours (940 nm). GKEY performed like an angel.

We never needed to do a C of G in this plane before, because so far it was not needed with just two people in it, but we found something interesting - these are the numbers we used:

Empty weight = 3099 lbs
Pilot = 195 lbs
Front Pax = 165 lbs
Centre seat pax #1 = 147 lbs
Centre seat pax # 2 = 144 lbs
Aft cargo = 35 lbs
Zero Fuel weight = 3785 lbs
Fuel = 780 lbs
Take off weight = 4565 lbs

The max TO WT for this plane is 4630 lbs.

The C of G worked out to be 137.7 which means we were a little outside of the curve to the left, and nose heavy.

Just for giggles, I then worked out a typical C of G with only me and my "first" CFI, who weighed close to 300 lbs, and full fuel 888 lbs. To my surprise, we were then even more left to the curve - 136.7 - and I remember the plane flew just great!

I see in the tech logs that this plane has had several alterations and mods made, like radio's, new seats, new equipment, Robertson STOL kit etc., and each time the C of G was recalculated just by math alone. It has never been physically re-weighed or C of G audited.

Is it possible that the C of G works out left of the curve because of wrong calculations with these many previous mods?

It's a distinct possibility. You can always get it re-figured. As I remember, it isn't expensive or time-consuming.

There is no way you are out of CG. It is almost impossible to exceed the CG of a skymaster. Pay careful attention to units of measurements -- i.e., moment/1000.

And on a side note, you can never bee too nose heavy -- otherwise the airplane would never rotate.

My sentiment exactly. I believe the numbers in the tech logs are cooked. I think my best option to to have a C of G audit done on the plane, to get the correct numbers.

If the plane has had a number of mods, it is a good idea to get it re-weighed.

Things like new paint, repairs and the like add to the weight continuously.

It is a fast & easy job if you have the scales or know some one who has them.

For example, although I have had much lighter radios installed and had wiring cleaned up etc., the four layers of paint mean the empty weight is now 80 lbs higher than the original Cessna weight & balance.

BTW, you can call Cessna and for a fee they will send you the original equipment list & weight & balance.

Dave

This is a pretty cool W&B calculator.
http://www.skybound.nl/cgi-bin/service/wb/index.cgi
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ASS ROUND

weight
 

Check your take off weight and fuel weight again. I have a 1975 P337G plane. Max. T.O Wt is 4,700 lbs. Also it hold 150 gallons of fuel. At 6 lbs per gallon. Fuel wt. comes comes to 900 lbs. It appears you noted the max. landing weight and not the T.O. weight.

Jerry
N34EC

I wish I did make that mistake, then it was easy to fix.
In my POH, my max TO weight is 4630 lbs (which I used), and the max landing weight is 4400 lbs.

With the 150 gal, 2 gal is unusable, and stays in the plane (as part of the empty weight), thus the full fuel added should read 888 lbs (at least the way I understand it). Even if I did add an extra 12 lbs for the unusable fuel (assuming that it has not been added before), it does not change my CG's at all.

During this trip, we only added the amount of fuel mentioned, to make my CFI feel better.

But still it does not make sense. What are your ususal CG's you get?