Move CG aft

[Guest]

Looking at a Mooney and the empty cg is 36.5 per the last weight and balance.  This is very far forward. Is there a way to add ballast to the tail to help bring the cg to a more reasonable number?

[Hank]

Just now, Kerrville said:

Looking at a Mooney and the empty cg is 36.5 per the last weight and balance.  This is very far forward. Is there a way to add ballast to the tail to help bring the cg to a more reasonable number?

What model Mooney is this? Some have Charlie weights that can be placed in the tail. Others just use tools, books or sandbags in the baggage area . . . .

[Guest]

It is an M20J. I can’t quite get it to balance as I would like even with the baggage area loaded to to max. I would like to be able to take full fuel at least when I am solo. So I was hoping there was a way to add ballast to the tail. 

[EricJ]

37 minutes ago, Kerrville said:

It is an M20J. I can’t quite get it to balance as I would like even with the baggage area loaded to to max. I would like to be able to take full fuel at least when I am solo. So I was hoping there was a way to add ballast to the tail. 

Something is very unusual here, and I'd look at possibly an error in the W&B rather than modifying the airplane.   A J model shouldn't have a CG problem, especially with one person and full fuel.

[Utah20Gflyer]

36 minutes ago, Kerrville said:

It is an M20J. I can’t quite get it to balance as I would like even with the baggage area loaded to to max. I would like to be able to take full fuel at least when I am solo. So I was hoping there was a way to add ballast to the tail. 

If it is really as far out as you describe my first suspicion is an incorrect weight and balance.  Why would your plane be so nose heavy in comparison to other people’s aircraft?  

[Guest]

I checked the arithmetic and it is on the form unless the shop did the procedure incorrectly. 

[MikeOH]

Check the station numbers.  Are they reasonable locations for a given entry?...something still seems off in the W&B

[EricJ]

7 minutes ago, Kerrville said:

I checked the arithmetic and it is on the form unless the shop did the procedure incorrectly. 

Something isn't right.   Worst case you can re-weigh the airplane and figure out where it really is, but something sounds very off unless it's had an engine conversion or something that moved the cg a ton.    FWIW, the empty cg on my J is at 47.1", and it's a reasonably typical airplane.   Something would have to be very unusual to move the cg that much.

[KSMooniac]

There is a mistake somewhere.  

[Fly Boomer]

1 hour ago, Kerrville said:

It is an M20J. I can’t quite get it to balance as I would like even with the baggage area loaded to to max. I would like to be able to take full fuel at least when I am solo. So I was hoping there was a way to add ballast to the tail. 

Mistakes are common in W&B calculations.

[Ragsf15e]

Do you have the original WB from the factory to compare to?  J models don’t have significant modifications that would change it, besides maybe a 3 blade prop and that isn’t much.

[Guest]

Thanks. Will check all that. I’m trying to see if I can get my hands on a prior WB. It was reweighed by the prior owner last year. 

[ArtVandelay]

Something isn't right.   Worst case you can re-weigh the airplane and figure out where it really is, but something sounds very off unless it's had an engine conversion or something that moved the cg a ton.    FWIW, the empty cg on my J is at 47.1", and it's a reasonably typical airplane.   Something would have to be very unusual to move the cg that much.

For comparison, mine was shipped with CG 44.9 and now 45.85, yours seem a little far back, what was it’s factory CG?
OPs is definitely not correct.

[PT20J]

1 hour ago, Kerrville said:

Looking at a Mooney and the empty cg is 36.5 per the last weight and balance.  This is very far forward. Is there a way to add ballast to the tail to help bring the cg to a more reasonable number?

That is impossible. The forward limit on a J is 41. My empty CG is 46. If it was reweighed, someone screwed up the calculation. (Because of the trailing link landing gear, you cannot use standard positions for the gear -- you have to use the procedure in the POH which is also in the Service and Maintenance Manual when weighing the aircraft). If the CG was calculated, you'll have to go all the way back to the factory CG and recheck all the intervening calculations (assuming that all the changes were kept) to find the error.

[Guest]

I am reading the mx manual and it looks like the shop just weighed the plane and measured from the datum point at the firewall. They did not use the nose gear trunnion reference per the equation in the manual. I imagine this would account for the problem?

[Guest]

I have no idea what the number is for the distance from nose wheel trunion to the center of main axles. I will have to measure next time I see the plane. Just using a random guess of 3 inches brought the cg forward 2 inches, but it is still probably no where near right. I think sitting empty it should surely be greater than 40. 

[PT20J]

10 minutes ago, Kerrville said:

I have no idea what the number is for the distance from nose wheel trunion to the center of main axles. I will have to measure next time I see the plane. Just using a random guess of 3 inches brought the cg forward 2 inches, but it is still probably no where near right. I think sitting empty it should surely be greater than 40. 

Likely

[1980Mooney]

15 minutes ago, Kerrville said:

I have no idea what the number is for the distance from nose wheel trunion to the center of main axles. I will have to measure next time I see the plane. Just using a random guess of 3 inches brought the cg forward 2 inches, but it is still probably no where near right. I think sitting empty it should surely be greater than 40. 

No telling what he did but it is in error.  The firewall is straight at the top and then angles forward. If he used the top of the firewall then he is at least 3.68 inches in error.  That gets you to 40.18 inches - still too far forward (limit is 41 inches).

Your plane is not nose heavy - the W&B is screwed up.

 

 

 

[Guest]

I’ll just get it weighed again. 

[PT20J]

5 minutes ago, Kerrville said:

I’ll just get it weighed again. 

If the weights are correct, there is no need to reweigh it. Just level it and measure the gear positions per the Mooney procedure.

[Fly Boomer]

7 minutes ago, Kerrville said:

I’ll just get it weighed again. 

Not a bad idea.  There might be some way to get to a better number mathematically, but that could just introduce some different errors.

[Hank]

1 hour ago, 1980Mooney said:

No telling what he did but it is in error.  The firewall is straight at the top and then angles forward. If he used the top of the firewall then he is at least 3.68 inches in error.  That gets you to 40.18 inches - still too far forward (limit is 41 inches).

Your plane is not nose heavy - the W&B is screwed up.

The way I read it, the bottom of the firewall is at -5.00, and the top is at 3.68, a difference of 8.68 inches.

Gotta watch those signs!

[Guest]

The WB document specifically states that they used the firewall for the datum. The mx manual says to drop a plumb bob from the nose wheel trunion, which is clearly a different location. I will try that to readjust using current weights. 

[PT20J]

2 hours ago, Hank said:

The way I read it, the bottom of the firewall is at -5.00, and the top is at 3.68, a difference of 8.68 inches.

Gotta watch those signs!

@Kerrville is correct. The firewall isn't used and the airplane has to be levelled.

[gacoon]

8 hours ago, Kerrville said:

Looking at a Mooney and the empty cg is 36.5 per the last weight and balance.  This is very far forward. Is there a way to add ballast to the tail to help bring the cg to a more reasonable number?

Light weight starter, remove vacuum system, if it has 3 blade prop change to 2 blade, consider avionics and/or instrument upgrades.  All can considerably lighten the front end.  All can be modeled doing W&B calculations.