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.

[goodyFAB]

On 3/24/2025 at 10:55 PM, N201MKTurbo said:

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.

im not arguing but as a rocket owner i can tell you that 100lbs on the horizontal will put the tail toward the ground. 

[N201MKTurbo]

1 hour ago, goodyFAB said:

im not arguing but as a rocket owner i can tell you that 100lbs on the horizontal will put the tail toward the ground. 

The mod would physically and structurally accommodate that much. I think they ended up with about 25 Lbs. It wasn’t my deal, I was just an observer and when it was done they threw me the keys and said to go check it out. It flew much nicer with the weights.

[IvanP]

20 hours ago, N201MKTurbo said:

The mod would physically and structurally accommodate that much. I think they ended up with about 25 Lbs. It wasn’t my deal, I was just an observer and when it was done they threw me the keys and said to go check it out. It flew much nicer with the weights.

Was this weight added after the batteries were relocated to the tail section? I flew a Rocket that had both bateries far aft in the tail couple of times and it felt a bit nose heavy with just one person in it, but overall a nice flying machine. I do not think that teh owner added any more weight after relocating the batteries. Accessing the batteries was a different story  .

[N201MKTurbo]

Yes, it had the dual battery box aft of the access panel. 

[IvanP]

It probably balanced the plane nicely. I almost bought a Rocket couple of years ago, but the deal fell through and I ended up with a Bravo. While I liked the Rocket, I really like the way the longer body feels.  

[1980Mooney]

On 3/24/2025 at 5:45 PM, 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. The FAA man said he would approve the mod for any Mooney. He made real drawings and had them approved by a DER.

 

22 hours ago, N201MKTurbo said:

The mod would physically and structurally accommodate that much. I think they ended up with about 25 Lbs. It wasn’t my deal, I was just an observer and when it was done they threw me the keys and said to go check it out. It flew much nicer with the weights.

 

23 hours ago, goodyFAB said:

im not arguing but as a rocket owner i can tell you that 100lbs on the horizontal will put the tail toward the ground. 

 

On 3/24/2025 at 9:27 PM, Aerodon said:

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

 

1 hour ago, IvanP said:

Was this weight added after the batteries were relocated to the tail section? I flew a Rocket that had both bateries far aft in the tail couple of times and it felt a bit nose heavy with just one person in it, but overall a nice flying machine. I do not think that teh owner added any more weight after relocating the batteries. Accessing the batteries was a different story  .

In round numbers the Missile 300 added about 200 lbs on the nose gear of the mid body J (full feathering prop, 2 extra cylinders hung farther forward).  I am not sure how much the Rocket 305 added ( heavier case, cylinders and added intercooler and full featheirng prop.) but likely substantial.  But don't forget that the Missile 300 and Rocket 305 conversion put 2 batteries in a battery box as far back in the mid body tail cone as it could go as @N201MKTurbo highlighted.  That weighs over 60 lbs.  (one approx 30 lb battery was removed from the baggage compartment wall).  Also back then the conversion included a approx. 8 lb AeroSafe Guardian Standby Electric vacum pump located in the tail cone.  The autopilots were pretty heavy, and control computer mounted in tail cone also.

If a Rocket or Missile owner goes all electronic on the panel and go with a modern autopilot, although you take the vacum pump off the engine and a few pounds off the instrument panel,  you can wind up removing a lot of weight much further back in the tail cone making the CG worse.  And if a Rocket or Missile owner is stupid enough to go to EarthX batteries in the tail they will just have to add that much additional Charlie Weights.

 

Edited May 5 by 1980Mooney

[1980Mooney]

1 hour ago, IvanP said:

Was this weight added after the batteries were relocated to the tail section? I flew a Rocket that had both bateries far aft in the tail couple of times and it felt a bit nose heavy with just one person in it, but overall a nice flying machine. I do not think that teh owner added any more weight after relocating the batteries. Accessing the batteries was a different story  .

Without the custom Battery Board on a Missile or Rocket, you are totally screwed.  You will get a hernia and probably damage the tailcone.

[cliffy]

7 minutes ago, 1980Mooney said:

And if a Rocket or Missile owner is stupid enough to go to EarthX batteries in the tail they will just have to add that much additional Charlie Weights.

 

Proves that just because it legal it may not be a good idea! The LAW of Unintended Consequences

The charlie weights that I have seen seem to run about 6 pounds each. 

[Fly Boomer]

3 hours ago, cliffy said:

The charlie weights that I have seen seem to run about 6 pounds each. 

I think there are 2x 6 lb and one 7 lb max.

[cliffy]

On 5/5/2025 at 3:40 PM, Fly Boomer said:

I think there are 2x 6 lb and one 7 lb max.

Kind of what I was thinking from memory.

From number crunching 19 pounds in the rear moves my CG aft 1.2 inches at gross weight.