Mooney Missile CG

[Rspencer612]

Hey all,

I have acquired a BEAUTIFUL M20J Missile conversion. Sadly the airplane logs were lost and it spent some time sitting. We have re complied with all the AD’s and finished the annual inspection and discrepancies.  Today we had a mechanic with scales out and the plane weighed in at 2065lbs empty with a CG of 36.96

this CG is so far forward the airplane CANT be loaded in anyway to get the the CG within limits. We will be inspecting the tail behind the battery looking for the 24lbs of Charlie Weights we learned about today that SHOULD be there according to Rocket Engineering, But when I run that calc as if they aren’t and we add them, still doesn’t seem to get my empty CG far enough AFT to be useable. What do other Missile owners have as there empty weight and CG?

 

also having a tough time getting an AFM supplement for the M20J Missile from Rocket.  Any owners have a digital copy they could share?  Thanks all. Looking forward to flying it, it’s ready but grounded until we figure out the CG issue..........

Edited May 1, 2021 by Rspencer612

[carusoam]

Rs,

When discussing WnB...

It is best to share the details that you know... all of them... line by line...

Expect one of the lines to have an error...

Or all Missiles wouldn’t be able to fly...

 

There is a constant discussion about WnB errors around here... it was getting filled in yesterday again...

Some are goofy math errors... dropped minus signs and things like that...

Or mis-ID’d reference point...  the bolt with the plum bob hanging from it...

The most recent Missile WnB mathematician around here may be @Seth.   So I have invited him to fly by if able...

Best regards,

-a-

[RJBrown]

Sounds like your mechanic needs help with math.

do you have the weight as measured from each wheel?

If not they need weighed again.

with 340# in front seat plus only fuel you should be within balance. If not the error is human not the plane.

what you describe could not be certified.

[Niko182]

The plane didnt have weights in the tail?

Something is clearly wrong with the math. Also make sure that when you weight it, the tanks are empty. That could make a difference.

[Guest]

From the maintenance manual.

Clarence

[Rspencer612]

Hey guys, to answer a few questions from above, yes we weighed the plane full of fuel and subtracted the fuel weight and moment. This is how most folks do it these days including Maxwell Aviation. 
 

we followed the manual and leveled the airplane and took the measurements. I am going to share the W&B work sheet here in a picture. 
 

and yes, Missiles had an extra battery and 24lbs of Charlie weights added to the tail to offset the forward CG created by the 100+lb engine and prop increase. We are going to look today and see if the weights are still there. We put two new batteries in. 

[David Lloyd]

The original W&B on my airplane at the factory, it was weighed with full fuel and they deducted the weight.  There was a line on the form for fuel temperature that was filled in as 80 degrees.  The weight of 52 gallons of fuel deducted was only 298 pounds due to the temperature.  Somewhere I have seen a chart that showed the weight of avgas per gallon at various temperatures.  So, it can be done.

20-1165 W & B Data .pdf

[Niko182]

Isnt the takeoff weight increased from 2740 to 3200 lbs. 3100 doesnt sound right.

[Rspencer612]

2 hours ago, Niko182 said:

Isnt the takeoff weight increased from 2740 to 3200 lbs. 3100 doesnt sound right.

I thought the same thing. I called Rocket as I have seen 2837 and 3200, depending on gear mods. This I believe was a 2837 bird by serial number. But then the gentleman at Rocket told me that they had a $$ only STC that took this model/conversion to 3100lbs based on my Mooney and Rocket serial numbers.  He is working to regenerate STC relevant paperwork for me and this airplane, but told us to use 3100. So you and I are confused together......

[1980Mooney]

2 hours ago, Rspencer612 said:

I thought the same thing. I called Rocket as I have seen 2837 and 3200, depending on gear mods. This I believe was a 2837 bird by serial number. But then the gentleman at Rocket told me that they had a $$ only STC that took this model/conversion to 3100lbs based on my Mooney and Rocket serial numbers.  He is working to regenerate STC relevant paperwork for me and this airplane, but told us to use 3100. So you and I are confused together......

There is no confusion. It is 3,200 lbs. 

Rocket Engineering holds the Missile STC’s under 2 names.  From the FAA STC Database which you can search online   STC/Mooney Limited, 6427 E. Rutter Road, Felts Field Spokane WA 99212 United States
		SA00081SE		Installation of Continental IO-550A engine and Hartzell PHC-C3YF-2UF/ FC7382 propeller.		Reissued		05/20/1994
		SA00260SE		Installation of engine cowling.		Issued		12/20/1995
		SA00472SE		Gross weight increase as modified per STC SA00081SE.

Rocket Engineering Corporation, 6427 E. Rutter Rd, Felts Field Spokane WA 99212 United States
		SE00223SE		Installation of Auto-Valve Inc oil drain valve

 

 

 

 

 

Edited May 1, 2021 by 1980Mooney
Turned STC upright

[Guest]

The maintenance manual calls for draining the tanks while doing a reweigh for W&B. From the manual here’s the procedure.

Clarence 

[Rspencer612]

50 minutes ago, 1980Mooney said:

There is no confusion. It is 3,200 lbs. 

Rocket Engineering holds the Missile STC’s under 2 names.  From the FAA STC Database which you can search online   STC/Mooney Limited, 6427 E. Rutter Road, Felts Field Spokane WA 99212 United States
		SA00081SE		Installation of Continental IO-550A engine and Hartzell PHC-C3YF-2UF/ FC7382 propeller.		Reissued		05/20/1994
		SA00260SE		Installation of engine cowling.		Issued		12/20/1995
		SA00472SE		Gross weight increase as modified per STC SA00081SE.

Rocket Engineering Corporation, 6427 E. Rutter Rd, Felts Field Spokane WA 99212 United States
		SE00223SE		Installation of Auto-Valve Inc oil drain valve

I thought the same thing, and maybe he misspoke when we called him, but he clearly told us 3100lbs max gross for this serial number.  I REALLY WANT him to send me the STC paperwork.  He has said they will for over 2 weeks now, yet never emails back or calls to get payment or send the materials.  Very frustrating actually.  And with no logs, Its certainly hard to get it all right.  Probably 2837 or 3200 based on your paperwork above, but it mentions gear upgrades.  on the phone, he mentioned an STC that is purchase only, no parts, for this serial number J to 3100 with the Missile conversion.............But maybe we misunderstood him...........

The gross weight part is easy to have changed and have the A&P/IA re print and sign.  the bigger issue here,  is regardless of the gross weight, the empty CG is too far forward.......way to far.  We have to solve that first and foremost for safe and legal operation!

Edited May 1, 2021 by Rspencer612

[Rspencer612]

27 minutes ago, M20Doc said:

The maintenance manual calls for draining the tanks while doing a reweigh for W&B. From the manual here’s the procedure.

Clarence 

I do understand that, but most guys, Including the most popular Mooney Service Center in the country, Weigh full fuel and subtract weight, moment, arm.  It achieves the same thing.  We do have the procedures in the J POH, and Maintenance manual for defuel weighing.  Since they achieve the same thing, the CG will still be very forward (maybe a very minor negligible change) in the 37 range which is not useable...........I think Charlie weights is likely the only reasonably priced solution here.

[Niko182]

12 minutes ago, Rspencer612 said:

I do understand that, but most guys, Including the most popular Mooney Service Center in the country, Weigh full fuel and subtract weight, moment, arm.  It achieves the same thing.  We do have the procedures in the J POH, and Maintenance manual for defuel weighing.  Since they achieve the same thing, the CG will still be very forward (maybe a very minor negligible change) in the 37 range which is not useable...........I think Charlie weights is likely the only reasonably priced solution here.

This reason alone is why a good chunk of airplanes gain weight when being reweighed. My Mooney technically has 89 gallon tanks, but when I top them off, I can fit just under a 105 gallons. That delta is a difference of 90 lbs. It will be worth it to do it right the first time. Especially since you're already running into problems. It just sucks now that you'd need to drain 70 gallons to properly weigh the J.

Edited May 1, 2021 by Niko182

[aviatoreb]

I am just really suspicious that there was a significant math error in the reweighs and that balance is way off.  I have never heard of a missile or a rocket with balance that far forward.  Even with the charlie weights you can't get that back to the balance envelope.  Typically the rocket engineering mods were carefully arranged so that with charlie weights you are at least in the standard original envelope at lower weights, even if on the forward end of it, and there is a funny bump in the w&b charts to accommodate higher weights but it is easy but not trivial to stay in that window.

[Niko182]

12 minutes ago, aviatoreb said:

I am just really suspicious that there was a significant math error in the reweighs and that balance is way off.  I have never heard of a missile or a rocket with balance that far forward.  Even with the charlie weights you can't get that back to the balance envelope.  Typically the rocket engineering mods were carefully arranged so that with charlie weights you are at least in the standard original envelope at lower weights, even if on the forward end of it, and there is a funny bump in the w&b charts to accommodate higher weights but it is easy but not trivial to stay in that window.

And If anything, wouldn't a Missile be further aft than a rocket since there isn't the weight of the turbo system, and the 520 and 550 practically weigh the same. I would guess there has to be a mistake on that nose scale.

[aviatoreb]

55 minutes ago, Niko182 said:

And If anything, wouldn't a Missile be further aft than a rocket since there isn't the weight of the turbo system, and the 520 and 550 practically weigh the same. I would guess there has to be a mistake on that nose scale.

I don't know about that.  A turbo isn't all that heavy and there are many details of the engine setups that I could see making one a few pounds heavier here or there. 

Anyway, I suspect something is just in error with this weight and balance measurement. I would seek a second opinion - reweigh - if this can't be sorted out in the paper work details directly.

[Guest]

4 hours ago, Rspencer612 said:

I do understand that, but most guys, Including the most popular Mooney Service Center in the country, Weigh full fuel and subtract weight, moment, arm.  It achieves the same thing.  We do have the procedures in the J POH, and Maintenance manual for defuel weighing.  Since they achieve the same thing, the CG will still be very forward (maybe a very minor negligible change) in the 37 range which is not useable...........I think Charlie weights is likely the only reasonably priced solution here.

Then I must be the outlier MSC.  De fueling in the only way to get an accurate empty weight.  You’ll need to STC and it’s associated installation drawing and instructions to know that the airplane meets those drawing.

Clarence

[carusoam]

Pluses...

1) Rocket really knows their stuff...

2) Their documentation is really excellent...

3) Their WnB and T/O distances can be proven to match reality...

 

Minuses...

4) Rocket engineering is a challenge to communicate with, it takes extra effort.  More than expected.

5) WnB math is an engineering school level class... this level of project gets covered over a couple of weeks... not because the math is challenging... no calculus required. It is a kinda complex subject.

6) Mooney added to the challenge by choosing a reference point that is between the nose wheel and the main wheels... a bolt on the nose gear.   This adds a negative number into the mix... where others use the firewall for an interesting place to start...

7) really odd... MGTW for Missiles and rockets are consistent through the years... where there is a step change for M20Js based on serial number and a change of a set of steel tubes in the structure...

 

8) Don’t be surprised if one highly regarded MSC in TX doesn’t empty the fuel tanks... there are a dozen ways to know exactly how much fuel is in there.  If you don’t know what the TX shop does to know the fuel load to 1/10th of a pound...   guess we won’t be leaving fuel in the tanks... 

When performing maintenance exercises... mechanics will reference the procedure used by number...  you won’t find a reference in your logs that says... that guy in TX said...

 

As a new owner...

9) getting the WnB right is a one time, get numbers you can live with kind of thing... accidentally being outside the envelope can be really bad at slow speeds...

10) While you are at it... verifying unusable fuel level, and max fuel level, and Kfactor for your FF sensor is a normal procedure for people that are planning to get the most out of their plane...

11) Don’t go on rumors...  it is highly unlikely that the rumored MSC would take a short cut as described here...  call that MSC directly to verify what they actually do...  don’t be surprised if they take an engineering level approach... and what you heard sounded more simple than what really is being done...

Don and Paul Maxwell are incredibly knowledgable, and sharing of their knowledge...  Paul Monitors MS...

12) Being extra familiar with the weighing process is important...  knowing how to level the plane is important, in both directions...  especially when deciding on using full fuel...

13) Some Mooneys, not many... have a mark on the fuel neck.... that indicates where full fuel is... the POH for the plane is specific about what the mark means and how to use it...

14) A mechanic taking the easy way out... has probably marked the floor with a lot of chalk... put blocks of wood under the scales at the mains... checked the scales for accuracy... used a plum bob, and marked the floor with it...  drained the useable fuel out of it... did the same or similar for oil and TKS fluid...

Oil level is nice... the dipstick is extra valuable with telling how much oil is in there while on the ground...

Fuel doesn’t have that graded level stick that is accurate while on the ground... good time to make one while you are at it...

When flying a Mooney...  it is usually about...

• speed
• efficiency
• safety

There is a right way to do everything...   most often, it is pretty well documented... POH, MM, Parts Manual...

Sometimes it takes having the experience to get things done correctly...  find the mechanic that has the experience...

Kind of like transition training... an ordinary CFI can teach how to fly a Mooney by the book...  but a Mooney specific CFI can teach a pilot how to operate around all points of the envelope safely...

Not seeking the extra expertise... can leave you operating well within the boundaries... or accidentally outside of them...

In modern Mooneys WnB can be done using 1/10th of a pound...  being off by a quart of oil, or a quart of fuel is in the 1.5 Lb category...  the whole WnB game is a very sensitive sport...

Continue to strive to get the correct details...  it is worth it.

And.... The Mooney M20R POH actually states the density for 100LL at at least one temperature...  crazy accuracy stuff...

Go Mooney!

PP thoughts only about the engineering class lovingly called Statics...

Best regards,

-a-

 

 

 

[carusoam]

See if this helps any...

Gravity... on!

-a-

 

[Rspencer612]

22 minutes ago, carusoam said:

Pluses...

1) Rocket really knows their stuff...

2) Their documentation is really excellent...

3) Their WnB and T/O distances can be proven to match reality...

 

Minuses...

4) Rocket engineering is a challenge to communicate with, it takes extra effort.  More than expected.

5) WnB math is an engineering school level class... this level of project gets covered over a couple of weeks... 

6) Mooney added to the challenge by choosing a reference point that is between the nose wheel and the main wheels... a bolt on the nose gear.   This adds a negative number into the mix...

7) really odd... MGTW for Missiles and rockets are consistent... where there is a step change for M20Js based on serial number and a change of a set of steel tubes in the structure...

 

8) Don’t be surprised if one highly regarded MSC in TX doesn’t empty the fuel tanks... there are a dozen ways to know exactly how much fuel is in there.  If you don’t know what the TX shop does to know the fuel load to 1/10th of a pound...   guess we won’t be leaving fuel in the tanks... 

 

As a new owner...

9) getting the WnB right is a one time, get numbers you can live with kind of thing... accidentally being outside the envelope can be really bad at slow speeds...

10) While you are at it... verifying unusable fuel level, and max fuel level, and Kfactor for your FF sensor is a normal procedure for people that are planning to get the most out of their plane...

11) Don’t go on rumors...  it is highly unlikely that the rumored MSC would take a short cut as described here...  call that MSC directly to verify what they actually do...  don’t be surprised if they take an engineering level approach... and what you heard sounded more simple than what really is being done...

Don and Paul Maxwell are incredibly knowledgable, and sharing of their knowledge...  Paul Monitors MS...

12) 

 

 

PP thoughts only about the engineering class lovingly called Statics...

Best regards,

-a-

Fair points. Rocket is very tough to get their attention. He answers the phone and tells me he is going to get me things, but there is no follow through. It’s very frustrating. I don’t know how to solve that. I have expressed I expect to pay for the time and document copies. Still no actions. Tells me to send emails then does not reply or call.  Not sure what to do next/more here.......
 

it’s not a rumor. I called Don to get his input a couple days ago as I was sure baffled by it to.  I explained how we weighed it, scales calibrated only a couple weeks ago, this was conducted by a full time aircraft weight A&P who travels and just weighs planes. His response was they scale them the same way, fueled up to the bottom of cap and then delete the fuel weight/moment. He expressed no issue with this mechanics method. Certainly the other method is the MOST accurate. Don advised to see if Charlie weights were removed and start there. This was also Rockets advise to start on the phone. My A&P did not get to it today, so waiting for that. 
 

and this plane was original Rocket STC as a 2837 MGTOW based on serial number. When I called him, he said it was higher than that and we both heard him say 3100 which obviously can’t be right. Again if we could just get the paperwork for this airplane from Rocket we may have these answers.  Hope it’s not 2837 because if we need Charlie weights it’s only going to have a 730lb ish useful load........

 

and I agree, a small mis calculation and being out of the envelope is not a safe thing. This plane is ready to fly, but has not left the ground as we work to resolve this.  The “math” looks good for the weights the scales showed. So, the question I guess is are the scales not accurate?  Well they were just calibrated and he is weighing multiple aircraft weekly with no other issues or complaints. So yes, we believe the planes balance is an issue needing resolved.  But I’ll see if I can find another local set of scales to verify it. 

[carusoam]

On the fuel being filled to the cap...

This is a method I follow as well...

Verify two things...

What volume is that?  Because the POH, your fuel gauges, and your placards next to the fuel tank may not be saying the number... some fuel necks are longer than others and don’t represent the bottom of the cap...

My plane mentions using the bottom of the fuel neck... (where the cap seats). But I can get a few more gallons in when carefully allowing air to escape out of the rib vent holes between wing sections...

If your plane’s fuel tanks have been re-sealed since it left the factory...  these holes in the ribs are often suspected to have been covered over unknowingly...  same situation at the bottom of the ribs... fuel can’t travel between ribs the holes get blocked...  (useable fuel to be checked before relying on the standards...)

Max filled tanks for my plane is about 102 gallons... where the POH and placards total 95...

For more detail about emptying the tanks... MSers typically drain the fuel from the tanks one at a time in flight... or they use the drain at the bottom of the fuel separator...

Once a tank is drained... it can be carefully filled and measured/verified at the same time...

M20Ks can have the most complex fuel tank arrangements... knowing what you have may be extra complex... extra fuel caps, tank connectors, and possibly overflow tanks... and something called a scupper valve at the top of one of the fuel necks on each side...

Nicely outfitted Rockets can have some pretty heavy avionics in them with lots of extra wire to support them.

A Rocket is one of the most capable Mooneys for business travel...

For family travel, they start getting UL limited, and O2 isn’t everyone’s preference... 

PP thoughts only, trying to help get to the bottom of this challenge...

To help with the biggest challenge... One person who has recent success getting Rocket Engineering support is @Seth...

Who I just sent an invite to...  See how he was able to get through...  Seth had a challenging tech situation when installing an OH’d Missile engine...

Hope this helps...

Best regards,

-a-

 

[DMM]

Did you measure the distance (arm) to the main gear with weight on the gear (L m/r)?  64.4 seems short.  When we bought our "E" the previous A&P used the arm listed for the main wheel assembly as shown in the factory equipment list (64.5).  Apparently that's the unloaded location of the wheel.  Our actual measurement was 65.7.  

[1980Mooney]

A couple comments and questions:

I see some pics of your plane online. 

SARLTaylor-N4262H-64.jpg | Sport Air Racing League (sportairrace.org)

KGYI-MooneyM20-N4262H-71.jpg | Sport Air Racing League (sportairrace.org)

Your cowling doesn't have the ram air found on most Missile conversions like this:

Do you have extended range Monroy tanks?  I assume you do not since your A&P used 64 gal in his calculation.

Where did your A&P get the Arms?  The POH says the wheelbase is 5 ft. 11 9/16 inches or 71 9/16 inches.  The nose wheel center should be 5 inches in front of the Reference Datum (service manual says should be within 0.06 inches of plumb line from nose gear trunnion which is station -5.  See 32-50-02).  That means the Main Gear Arm is 66 9/16.  Your A&P used 64.  Are your nose gear discs collapsed and the nose wheel displaced back?

 

 

My Missile was weighed by Rocket.  2,169 lbs empty and CG 41.63 inches.  I have a standby vac in the tail which adds weight.

It is inconceivable that your Mooney is that far out of forward balance.  However I see all these pics of it racing.  Do you think someone took the weights out of the tail for some sort of speed mod?

Regarding Rocket - mine was one of the last Missile conversions.  It was done in 2001.  They hadn't done any in a while at the time and they actually made a mistake setting up the IO-550.  They had to get the Continental Rep out to help remind them - I was there when it happened.  Their focus even in 2001 had almost entirely shifted to turboprop conversions of Piper Malibu's. There are some threads here saying Rocket committed to support the STC for 17 years - not sure from when but the last Missile or Rocket was done 20 years ago.  They support as a curtesy now but let's be realistic - they haven't worked on a Mooney or internal combustion engine in 20 years.  There probably are few if any employees still there that actually turned a wrench on a Mooney. Darwin Conrad is in his 70's.  Whoever is helping you has to go dig in the files.

 

Edited May 2, 2021 by 1980Mooney

[carusoam]

Great insight 1980!

Thanks for sharing...

Best regards,

-a-