REFLECTOR: Wgt and Balance

[Terry Miles]

Dear All,

I did my wgt and balance this week.  Here is the news and comments.  

 

First the news:  She came in at 1892.5 pounds and 136.7 aft of datum. I am
very happy with that.  Here are some particulars:

*	300 HP Lycoming which is another 60 pounds more than the 260 HP
version.  
*	Two full sized batteries in the nose, 
*	All the seats, seat cushions, hooker seat belts, and the false fire
wall in place.  No carpet or headliner or trim.
*	A couple of headsets, and my backup handheld GPS and VHF/VOR ICOM
and a small fire extinguisher.  
*	A final exterior paint job and some Zolatone on the gear legs, wheel
wells and ceiling beams   

 

I used locally borrowed certified scales.

 

Minor irregularity:  I thought the "Owners Flight Manual and Wgt & Bal" book
was nicely done and provided me with some approximate figures.  That gave me
a reasonableness crosscheck as I started to get my own numbers.  I take
exception to one number in the Velo book on page 33 where it shows the sump
tank at 145 inches.  It is over 150 inches.  The reading comes from the fact
that the gas won't all drain into the sump so using gear wgt numbers on the
scales may not be the most accurate approach for this particular
measurement.  Especially in the RG where the sump is only half the size of
the FG.  Be aware that with any two known numbers you can calculate the
third.  I backed in my wheel numbers (moment)  and used the know fuel weight
and the known arm.  

 

"Been There" Advice:  

*         I made the mistake of pouring all the first 20 gal into one tank
thinking that it would level across wings in no time flat.  Wrong.  What I
did was introduce a heavy wing and small bank angle.  It would be better to
put the fuel in equally to each tank then wait a couple of minutes.  Pick a
slow time for the fuel truck man!  Then rocks the wings slightly.   Be sure
you are chocked.    

*         I didn't measure the distances from datum to various key points
prior to putting the aircraft on the scales.  Points like wheel axel points,
aprox wgt centers for front seat, rear seat, spots you have earmarked for
Jepp bags, door cubbyholes, you name it.  It is much harder to do this with
the aircraft on scales.   All these can be done easier with a plumb bob and
marking spots on the hangar floor then record them all on a sheet of paper
before you begin.  All this for a reasonableness crosscheck as you do the
measurements.  You will need to know all the other distances the day you
load the airplane for a trip to grandma's.  Good idea to get them now.

*         Leveling:  My airplane as it sat empty on the hangar floor was
nose high.  I should have thought to shim the main wheels with a pc of
plywood as I mounted the airplane on the scales.  I didn't.  

*         The top plate of the scale was a rectangle shape about 28x18
aprox. I never thought about it.   I put the dam things in sideways and
didn't have room for chocks.  

*         You can let air into or out of the tires within a range to get the
pitch and bank level numbers you need.  A friend on hand suggested that and
it worked great, with this exception.  If you have the nose tire down to
complete deflation as you add wgt the side walls will compress on you some.
The wgt change on the nose from empty to full is about 50 pounds.  

*         I did my fuel probe calibration at the same time to include
marking my cabin sight gauges and a dip stick.  That's a lot going on at
once.  Make yourself a checklist.  Or be ready with siphon pumps and barrel
for oversights!  

*         Check BOTH tanks as you add fuel with the dowl stick from the
hardware store.  I had a wing to wing wgt imbalance as the night went along
that didn't affect the CG, but was a puzzle to me until I realized I had a
small wing droop (gear flex?)  that didn't show up much on my centerline
mounted digital level in the aft cabin.    For the XL: for me:   the dip
stick for me came out at 1 inch equals 5 gallons or close enough from empty
to full.

 

Terry

 

 

  

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