M20K CG

[druidjaidan]

Early M20K. W/B shows it at an empty weight of 1930 and a CG at 33.0in. This doesn’t look like it should be a nose heavy weight champion mind you. 2 blade prop, modern avionics, factory O2 in the tail, not a rocket conversion, doesn’t even have the intercooler. 

I understand that modern Mooneys have a rep for forward CG, but this can’t be right can it? Even with 120 in the cargo and full fuel to pull the cg as far aft as possible this plane would be well out of CG with a single FAA standard person up front. I couldn’t get this plane into CG in any configuration, I must have something wrong right? 

Edited December 16, 2023 by druidjaidan

[Shadrach]

6 hours ago, druidjaidan said:

Early M20K. W/B shows it at an empty weight of 1930 and a CG at 33.0in. This doesn’t look like it should be a nose heavy weight champion mind you. 2 blade prop, modern avionics, factory O2 in the tail, not a rocket conversion, doesn’t even have the intercooler. 

I understand that modern Mooneys have a rep for forward CG, but this can’t be right can it? Even with 120 in the cargo and full fuel to pull the cg as far aft as possible this plane would be well out of CG with a single FAA standard person up front. I couldn’t get this plane into CG in any configuration, I must have something wrong right? 

Sure reads like you have something wrong to me. can you post the weight and balance data?

[druidjaidan]

3 minutes ago, Shadrach said:

Sure reads like you have something wrong to me can you post the weight and balance data?

 

[Shadrach]

24 minutes ago, druidjaidan said:

 

I’m trying to find W&B from another K model to make a comparison but have not had much luck.

Also, that revision does not tell much much of a story without previous data.

[druidjaidan]

I just can't believe I have this right tbh.

This plane appears to be totally unflyable currently and would need a ridiculous amount of charlie weights to make it usable just to fly solo.

If that's right and common I need to abandon shopping for a K. I don't want to carry around a 100lbs of lead shot to out in the cargo anytime I want to go flying and the family needs more usable weight than I can afford to put 100lbs of Charlie weights in.

[Utah20Gflyer]

The most likely hypothesis is the weight and balance is wrong.  Unless you have access to the previous weight and balance so you can find the mathematical error the plane will need to be re weighed and a new weight and balance created.  
 

Mid body Mooneys tend to have the best weight/balance scenarios and you don’t tend to see them with far forward or aft CGs.  My G model is almost impossible to get out of CG.  

[Ragsf15e]

29 minutes ago, druidjaidan said:

I just can't believe I have this right tbh.

This plane appears to be totally unflyable currently and would need a ridiculous amount of charlie weights to make it usable just to fly solo.

If that's right and common I need to abandon shopping for a K. I don't want to carry around a 100lbs of lead shot to out in the cargo anytime I want to go flying and the family needs more usable weight than I can afford to put 100lbs of Charlie weights in.

That’s got to be wrong. The w/b requires offsets from the measurement points iaw the manual.  No way they did it right.  My F with a 3 blade is 45inches!

[Shadrach]

13 minutes ago, Ragsf15e said:

That’s got to be wrong. The w/b requires offsets from the measurement points iaw the manual.  No way they did it right.  My F with a 3 blade is 45inches!

Yup. Most mid bodies are 45-47”

 

[hubcap]

The CG on my K model is between 43 and 44 inches depending on fuel and load. I have 950ish useful load.
 

I am guessing there is a mistake on your paperwork.

[LANCECASPER]

This is from a ‘97 Encore that I owned that had the factory Classic Plus avionics and TKS FIKI





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[GMBrown]

My K (1980) has a CG of 44.  From the factory was 43.  The moment for your plane appears to be incorrect.  It should be in the vicinity of 89,000.  My from the factory moment was 89,337.  So I question his nose figure of -9420.  If the moment was actually positive (i.e. +9420), then the cg would be 37518 + 35550 + 9420 = 82488.  Which would make an empty weight CG of 42.8.  Well within the envelope.  Looks like a typo in the Nose Arm.  It should be plus 15, not negative.  Just conjecture but it would make the numbers fit the factory specs.

[kortopates]

Decades ago a shop offered to weigh my first Mooney, a 231. It came out with similar results. I just ripped l it up as you should do with this one and hopefully you didn’t need a new one from any changes. But if so just have them do a revised wt & bal from calculating. I’ve been through major panel updates and always calculated the revised wt& bal.


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[PT20J]

It looks like this was a reweigh. The CG calculation can get messed up if the procedure for determining the datum and distances to the wheel axels described in the POH and service manual is not used.

[druidjaidan]

1 hour ago, GMBrown said:

My K (1980) has a CG of 44.  From the factory was 43.  The moment for your plane appears to be incorrect.  It should be in the vicinity of 89,000.  My from the factory moment was 89,337.  So I question his nose figure of -9420.  If the moment was actually positive (i.e. +9420), then the cg would be 37518 + 35550 + 9420 = 82488.  Which would make an empty weight CG of 42.8.  Well within the envelope.  Looks like a typo in the Nose Arm.  It should be plus 15, not negative.  Just conjecture but it would make the numbers fit the factory specs.

I think you're on the right track, and I think I know what's happened now.  I'm not an expert in this so I could be wrong (and I'm using a 252 POH rather than a 231 POH, but I figure it's got to be close). The nose gear should be negative, it's in front of the datum.  However, it should be a 5in arm, not 15in. And the main gear arm is measured from the nose gear as a reference, so I think it should be 66in not 56in.  Changing the arms out for my guesses gives a 43in empty CG, which is perfect and makes WAY more sense. I think we're still not going to buy this particular one, but I'll let the broker/seller know that they should get their paperwork fixed.

 

[PeteMc]

5 hours ago, Shadrach said:

I’m trying to find W&B from another K model to make a comparison

I don't have my W&B handy, but just looking at the generic numbers in the POH...  1830lbs, 76.53 Inches

 

[Shadrach]

5 hours ago, LANCECASPER said:

This is from a ‘97 Encore that I owned that had the factory Classic Plus avionics and TKS FIKI





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Wow, the was barely a two person aircraft as delivered. The classic plus package must have been pretty extensive.

[Shadrach]

36 minutes ago, PeteMc said:

I don't have my W&B handy, but just looking at the generic numbers in the POH...  1830lbs, 76.53 Inches

 

That’s way aft. That can’t be right.

[PeteMc]

7 minutes ago, Shadrach said:

That can’t be right.

Don't know what to tell you...     Remember it's generic out of the POH, not a real W&B.  But can't see Mooney using totally bogus numbers.

 

 

Edited December 17, 2023 by PeteMc

[PT20J]

Just follow the procedure in the manual and you will get the right answer.

[LANCECASPER]

2 hours ago, Shadrach said:

Wow, the was barely a two person aircraft as delivered. The classic plus package must have been pretty extensive.

It was delivered to the original owner as a 252, none of which had a very high useful load. Then about 20 days later the FAA paperwork came through approving the Encore, so it got a 230 pound gross weight increase. 

[pkellercfii]

Your shop both didn’t follow the Mooney service manual (MSM) procedure for weighing the aircraft & determining the resultant CG, and even for the lazy shortcut they took for finding the CG, they used the wrong arm distances.  If I take your wheel weights & combine them with my airframe undercarriage distance measurements, then, using the proper MSM procedure for determining CG, I get 40.86” for your empty CG. That’s still mighty far forward, but, for some typical W&B cases I ran, still within the envelope. My Mooney is an ‘89 252, and so not much different from a 231. The undercarriage distance measurements shouldn’t vary much between airframes. 

You need to find an A&P who will at least recalculate your empty CG correctly. Decide for yourself if you want reuse the weights measured by a shop where the personnel apparently flunked out of elementary school and thus can’t read a service manual. The procedure for determining empty CG from the individual wheel weights & undercarriage distances is on p. 8-00-01 of the M20K service manual.

—Paul Keller

 

[kortopates]

That’s way aft. That can’t be right.

it’s not actually inches but the moment in thousands- intended for using the moment envelope rather than inches.


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[kortopates]

So given the erroneous weight and bal is 3.5 years old i am still scratching my head to understand how the pilot has been doing his or her obligatory weight and balance pre-flight check. Although we all know the answer. sigh…


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[Schllc]

My long body has a cg of 45.23. 
you would have to do something intentionally stupid to get the plane out of CG. 
It’s easy to exceed gross, but it is very difficult to get out of CG.

[Z W]

1982 M20K here.  41.9 CG.  Very hard to get it out of CG, although it tends to run nose-heavy.  Flies better with some weight in the back.

I have some doubts about the W&B numbers after all the changes.  Have considered getting it reweighed.  Took at least 25lbs of wires and mess out during the last panel install.  Sheets like the one posted here have made me reluctant to let the plane see the scales...