Possible Weight & Balance Calculation Error

[philiplane]

Due to the variation in how tanks are filled, and the specific gravity of the fuel used, it is impossible to be accurate by filling the tanks and then calculating the fuel out. The weight will vary from -5 to +20 pounds on an M20C.

I always weigh with full engine oil, fuel drained, and unusable fuel added in per the manual. 

Edited September 24, 2020 by philiplane

[ManGar]

14 hours ago, ArtVandelay said:

Wow, that’s pretty far aft, did you move the battery from engine compartment to tail or some other mod that would affect it?

No, the battery is still in the front.  I just got the airplane last year and the only modification I made was the alternator STC which lightened the front by 6 pounds.  At this rate, I won't be able to install the G5 and get rid of the vacuum pump.

[ManGar]

14 hours ago, David Lloyd said:

My airplane is the fattest C in existence at 1771 lbs.  The CG is 46.15, so I think the 49" numbers are most likely incorrect. My weights were 615 for the left main, 614 for the right main and 542 nose wheel.  The OP said the nose arm was 3".  That has to be incorrect. Mine was close to 0.  This is the distance between the center of the nose trunnion and the center of the nose axle.  Can't be 3". My distance the nose and main axle centers was 66.5, so 65.75 is believable. 

If you want to check the math, print and read the weight and balance work sheets, go to the airport with those sheets, a plumb bob, a level and a tape measure.  

Park your airplane on a nose downhill slope and check for level.  Deflate your nose tire as needed. Measure the distance between the nose wheel axle center and main wheel axle centers.  Fill out the first part of your worksheet (assuming your weights were correct). Measure the distance from the center of the nose gear trunnion and main wheel axle centers. This is where you will find the 3" difference.   Fill out the second part of your worksheet.

This will not be an exact calculation as the gear discs are slightly compressed with all the stuff in your airplane that should not have been weight and the 30 gallons of fuel you didn't drain.  But, it will give you a pretty good idea.

My airplane was weighed earlier this year after an installation by Pee Dee Avionics in Cheraw, SC. They had the scales, they removed a fuel line and pumped out most of the fuel, then drained the remainder of the fuel. Then added back the unusable fuel. I think they charged a few hundred dollars.

 

Thank you!!!  I suspected the arm distance in one of the gears was at least one of the culprits along with the 50 pound difference in the main gears.  I'll do as you suggested just to verify and then get it weighed to make it all legal.  Thanks again for all of the advise from everyone!

[ManGar]

13 hours ago, carusoam said:

MG,

1) You are about to embark on the same journey that everyone else has gone through...
2) WnB checking is the first thing... many new owners didn’t get the paperwork during the transition...

3) Your paperwork is pretty far off base... somebody probably lost sight of where 0.0 is located.... it is a bolt on the nose gear...

4) Weighing the plane needs to follow a procedure to get it right... that procedure is in the maintenance manual...  

5) Chances are, somebody didn’t know these details and put the details together in a close but not quite right kind of way...

6) Find who made the errrors to see what else they touched....

7) No need to blame anyone.... the factory has messed up quite a few as well...
 

8) Most mechanics that have Mooney experience are going to know how to weigh a plane...

9) there are a few threads around here where people have spent pages trying to find where their errors are and came from in their WnB...

10) It is important to know... doing the WnB prior to flight is still important... especially when the plane is new2U...

11) To know if a mechanic has scales... call and ask...

12) To save a ton of dough, organize all the things that are now included in the weight... a dated record that can be updated each time something gets added or removed...

13) expect to find a level surface... then realize, your nose is going to be a couple of inches high...

14) Be ready to Jack the plane up to help with leveling... it helps to have jack points for your plane...  ask your mechanic what he has...

15) you will become familiar with a seam, some seat tracks, and a bolt, by the time you are done with this project....
 

16) Work on getting a copy of the MM, Parts Manual, and latest POH printed for your plane.... All stuff that is handy to have...

 

PP thoughts only, not a mechanic...

Best regards,

-a-

Thanks for all the advise.  This has all been a learning experience.  None of which has made me regret buying my first airplane.  I love the Mooney and know its a great machine.

[carusoam]

11 hours ago, ManGar said:

Thanks for all the advise.  This has all been a learning experience.  None of which has made me regret buying my first airplane.  I love the Mooney and know its a great machine.

No better way to get started in GA than having an M20C...

 

All old planes take time and effort to get up to the level the new owner wants...

The first year is often the most challenging...

Things get much more stable after that...

Best regards,

-a-

[Hank]

13 hours ago, ManGar said:

Thanks for all the advise.  This has all been a learning experience.  None of which has made me regret buying my first airplane.  I love the Mooney and know its a great machine.

Still loving my C! 13 years and counting . . . .