Curious question about Charlie Weights in long bodies

[cliffy]

Discussion at the airport today about charlie weights in Mooneys

Were they all the same weight or did they change with s/n?

Anyone know?

[Marc_B]

Not a long body but my POH has instructions for calculating how much fixed ballast weight is recommended in the tail based on CG. Options for 6, 13, or 19 lbs. I suspect the long bodies are similar  

[cliffy]

Now that's interesting I didn't know that chart even existed.   Thanks.

Just thinking out loud here-  Seems that short bodies might be less effective trying to stop rotation with a higher polar moment (adding charlie weight) than medium or long bodies due to the shorter moment arm and/or the shorter rudder. 

It comes to follow then IF one wants to move the CG aft with weight (and suffer the lower Useful Load ) in a short body then weight in the baggage compartment might be a better idea (also lowering the allowable baggage in that compartment). 

Another thought would be to add weight on the radio shelf aft of the baggage pit. This might be a better idea than the baggage pit itself. 

Lower polar moment than tail mounted but already planned for in the certification- radios or weights? What difference does it make? 

More weight needed due to shorter moment arm than tail mounted but everything is trade off in airplanes.

Just postulating for ideas from the brain trust. 

[Niko182]

On 3/22/2025 at 11:33 PM, Marc_B said:

Not a long body but my POH has instructions for calculating how much fixed ballast weight is recommended in the tail based on CG. Options for 6, 13, or 19 lbs. I suspect the long bodies are similar  

I have the same thing in my 99 Eagle.

[EricJ]

41 minutes ago, cliffy said:

It comes to follow then IF one wants to move the CG aft with weight (and suffer the lower Useful Load ) in a short body then weight in the baggage compartment might be a better idea (also lowering the allowable baggage in that compartment). 

Another thought would be to add weight on the radio shelf aft of the baggage pit. This might be a better idea than the baggage pit itself. 

Lower polar moment than tail mounted but already planned for in the certification- radios or weights? What difference does it make? 

It's a tradeoff, since moving the ballast forward to reduce the polar moment linearly increases the amount of ballast weight needed.    In other words, if you move the weight forward half the distance toward the CG, you'll need twice as much weight.   That can chew up UL pretty quickly.  

I helped a friend with an experimental do an engine swap from an na motor to a twin turbo that weighs quite a bit more.   Just to get the CG back to where it was we added a big chunk of ballast and mounted it in a small space on top of the stabilizer, basically as far back as we could get it to minimize the amount of ballast needed.   So the increased engine mass and the ballast together increased the polar moment, but I don't know that that changed the handling much.   I never flew it before the swap so have nothing to compare to, but he hasn't complained about it at all (other than the increased fuel consumption). 

[Marc_B]

For comparison for the mid-body (long body would have a further arm for the tail charlie weight so this would be even more accentuated)...

6 lbs in tail at station 197.5 = moment 1185

equivalent to:

10.7 lbs in avionics bay at 110.8 (78% increase)

12.4 lbs in baggage area at 95.5 (107% increase)

16.8 lbs in rear seat at 70.7 (179% increase)

[N201MKTurbo]

FWIW, a friend of mine got a field approval for adding as much as 110 pounds of Charlie weights to the tail of a Rocket. The FAA man said he would approve the mod for any Mooney. He made real drawings and had them approved by a DER.

[cliffy]

1 hour ago, Marc_B said:

For comparison for the mid-body (long body would have a further arm for the tail charlie weight so this would be even more accentuated)...

6 lbs in tail at station 197.5 = moment 1185

equivalent to:

10.7 lbs in avionics bay at 110.8 (78% increase)

12.4 lbs in baggage area at 95.5 (107% increase)

16.8 lbs in rear seat at 70.7 (179% increase)

These are numbers for a K correct?    :-)

[Marc_B]

14 minutes ago, cliffy said:

These are numbers for a K correct?

Yes. 97 M20K. 

[Fly Boomer]

2 hours ago, N201MKTurbo said:

FWIW, a friend of mine got a field approval for adding as much as 110 pounds of Charlie weights to the tail of a Rocket.

I can't imagine any amount of weight on the nose or anywhere else in the airplane that would put it back inside the envelope with 110 pounds in the same location as the factory Charlie weights.  I also can't imagine that the airplane would be flyable.

[N201MKTurbo]

I flew it like that, it was very easy to fly. I think he ended up with 35 Lbs. The plane had 3 prop strikes on landing before the mod. FWIW, I I flew the plane  before the mod and it wasn’t the planes fault. My friend convinced the owner to buy a 172.

[cliffy]

We all watch the weekend landings at our airport and invariably 3 or 4 out of 5  Mooneys land fast and PIO down the 

runway for 1000' or more before touching down on all 3 wheels at the same time. As do ALL the Cirrus airplanes. 

I took a friend flying last Saturday (he owns an E model) and after we got back he said he needs to try slowing down more before 

he crosses the runway end.  Said he was crossing the numbers at 70 KNOTs !  I do it at @65 MPH in my D/C

[Aerodon]

1 hour ago, Fly Boomer said:

I can't imagine any amount of weight on the nose or anywhere else in the airplane that would put it back inside the envelope with 110 pounds in the same location as the factory Charlie weights.  I also can't imagine that the airplane would be flyable.

It takes less than 110 lbs on the elevator to put the tailskid on the ground....

[N201MKTurbo]

The mod was designed to accommodate from 4 Lbs to 110 lbs. it went in 5 Lb increments. You could get finer increments by making the lead plates thinner. The structural analysis was done at the 110 Lbs. Rockets were very nose heavy.