See any errors in this W/B?

[Roberts13t]

This is from a 64 M20E. It was weighed. This weighing moved the CG aft by over 1.5”. I don’t want to hear how it’s possible or anything other than trying to find errors in the process. Please just check the math and process on the computation sheet. I have a few ideas on some errors but I want to hear from the experts as I’m really new to mooneys. Thanks for the help!

[RLCarter]

Net weight is off by a tenth .... really need to see the previous also

[Roberts13t]

6 minutes ago, RLCarter said:

Net weight is off by a tenth .... really need to see the previous also

If weighed would there be a reason to see the previous? The previous is a calculated one, not a weighed one. The previous one can be traced through 7 previous computations of adding and subtracting equipment from the original w/b from factory. This current weighed one is 20 lbs heavier for empty weight, 1.64” CG toward the aft, and 3669.96 more moment.

 

I’m wanting to focus on if this weighed one was done correctly because the changes seem large. Moreover the aft moving CG is of concern. And yes I know how it may have happened. 

[Hank]

Found a Service Manual in the Download section (my hardcopy is in the hangar). Took this here picture, it's page 2-3. There is much clear explanatory text before this fine drawing.

[Roberts13t]

20 minutes ago, RLCarter said:

Net weight is off by a tenth .... really need to see the previous also

So what should the net weight be? Did you get it by just adding up that column?

[Roberts13t]

12 minutes ago, Hank said:

Found a Service Manual in the Download section (my hardcopy is in the hangar). Took this here picture, it's page 2-3. There is much clear explanatory text before this fine drawing.

Using that figure from Mooney and the weights from the OP I get 46.11” for CG. That’s going in the direction I need it to. 

[Hank]

He also added the moment for the oil instead of subtracting it. That gives CG = 46.61, which still seems kinda far back. The 15lb was correctly subtracted from the weight, but that negative doesn't apply when figuring out moment, unless there was 15 lb of expected oil not there (there wasn't). Simple math errors.

15 minutes ago, Roberts13t said:

And yes I know how it may have happened. 

So what are you thinking this late at night, when we're all about to turn in?

[N201MKTurbo]

I thought your nose wheel arm looked odd. I looked in my J manual and it shows the nose wheel axel at -5 not 0.5. Double check that.

[Hank]

Just now, N201MKTurbo said:

I thought your nose wheel arm looked odd. I looked in my J manual and it shows the nose wheel axel at -5 not 0.5. Double check that.

Your J is longer. The nose wheel bolt distance was changed as the fuselage stretched.

@Roberts13t, lookup the Service Manual in the Download section. I'll check back in the morning. 

[N201MKTurbo]

Just now, Hank said:

Your J is longer. The nose wheel bolt distance was changed as the fuselage stretched.

@Roberts13t, lookup the Service Manual in the Download section. I'll check back in the morning. 

Sure, but even the drawing above shows the nose wheel in front of the datum. That would be -0.5 instead of 0.5.

[Roberts13t]

Hank, these are the things that keep me up at night.

I think the arm is incorrect too on the oil. The Mooney M20E w/b sheet I have says -6.5. (-7.5 is C models)

[RLCarter]

If it was weighed according to the MM, fuel & oil should have been drained so there shouldn’t be anything for oil or fuel on the worksheet 

[Roberts13t]

8 minutes ago, RLCarter said:

If it was weighed according to the MM, fuel & oil should have been drained so there shouldn’t be anything for oil or fuel on the worksheet 

Have you weighed your E? Where was the front wheel compared to the datum? 
 

They didn’t do the computations correctly for subtracting the oil from the moment. If you subtract unusable fuel and moment then it changes CG by .12 forward. 

[RLCarter]

6 minutes ago, Roberts13t said:

Have you weighed your E? Where was the front wheel compared to the datum? 

I have it at the hangar, will set a reminder and get it posted for you

[jaylw314]

1 hour ago, Roberts13t said:

Have you weighed your E? Where was the front wheel compared to the datum? 
 

They didn’t do the computations correctly for subtracting the oil from the moment. If you subtract unusable fuel and moment then it changes CG by .12 forward. 

It looks like they weighed the aircraft with full oil.  Rather than drain the oil and weigh the plane, they subtracted the weight of the oil and its moment.  Mathematically, that's correct, although I have no idea if that's technically kosher.

It's a little confusing that the moment for DEDUCTING the oil is positive, but it makes sense if you think about it since your multiplying two negative numbers. 

I'm curious how they got that fuel weight.  Does your E really only have a only a half gallon TOTAL of unusable fuel?  I think the J officially has 2.5 gallons of unusable fuel, that's a huge difference?  The fact they added it suggest they must have drained both tanks fully

The numbers as presented, though, at least look correct.

Edit:  Aircraft empty weight is typically FULL oil and unusable fuel.  I noticed in my J POH the sample W&B are done with aircraft basic empty weight, e.g. including full oil.  Obviously, any combination of oil and fuel is doable as long as its done consistently, which might be part of the issue here.  Did your previous W&B use full oil?

Edited April 27, 2021 by jaylw314

[David Lloyd]

On 4/27/2021 at 12:33 AM, RLCarter said:

If it was weighed according to the MM, fuel & oil should have been drained so there shouldn’t be anything for oil or fuel on the worksheet 

Kevin Kammers at Mooney sent me the original W&B for my airplane.  in May 1975 they were weighing them with fuel and deducting the weight of the fuel, unlike what it says to do in the manual.  Attached file, couldn't figure out how to attach only the first two pages.  Look at the first two pages closely and you see the temperature is noted and the fuel weight is calculated based on that temperature.  52 Gallons at that temperature does not weigh 312 pounds.

Also note the nose gear is at -1.0.

20-1165 W & B Data .pdf

[RLCarter]

13 hours ago, Roberts13t said:

Have you weighed your E? Where was the front wheel compared to the datum? 

Just a quick comparison, my CG is farther back than yours and your nose wheel weight is 50ish lbs more. I'm guessing mine is accurate do to the fact it was done twice, 1st one was miss-placed and found several days later and it had been re-weighed, I was there for both weigh ins.

[Roberts13t]

I can’t get the service manual 106 to download. Has anyone else had trouble?

 

[RLCarter]

1 hour ago, Roberts13t said:

I can’t get the service manual 106 to download. Has anyone else had trouble?

 

It won’t download on mobile devices (ph, tablet) it will download to a PC

[Roberts13t]

24 minutes ago, RLCarter said:

It won’t download on mobile devices (ph, tablet) it will download to a PC

Thank you

[Hank]

1 hour ago, RLCarter said:

It won’t download on mobile devices (ph, tablet) it will download to a PC

I downloaded it onto my $100 Samsung tablet last night, that's where the picture I pasted came from (screenshot). My own plane is a 1970, I don't need this manual.  

[Guest]

From the maintenance manual, here’s the text to go with the picture Hank posted.  Fuel and oil to be drained.

Clarence

[Roberts13t]

43 minutes ago, M20Doc said:

From the maintenance manual, here’s the text to go with the picture Hank posted.  Fuel and oil to be drained.

Clarence

Looking at these procedures it appears it was done incorrectly. All the oil and fuel should have been drained. Then instead of using the weight, arm, and moment they should have used the three weights and the formula given by Mooney. Looks like it will have to be redone correctly this time.

 

I assume because it is a 64E then the Service manual from 1966 should be used opposed to the 106 series manual that also has E series in it but from 69-75?

 

Personally I learned Empty weight was no fuel, but unusable in the tanks, and oil/hydraulic fluids to run it. Basically in a CH47 I needed to know how much fuel and how much internal or external cargo I needed to take in so it was good to already know the aircraft had oil/hydraulic fluid in it and accounted for. Truthfully if the mechanic did it that way then used the Mooney formula I probably wouldn't be that upset as it give a person a realistic functional "empty weight" and CG. Of course the question would arise of 6 of 8 qts of oil.

[carusoam]

There has to be a half dozen ways to make a mess out of doing a WnB...

It helps to have the one before...

This way you can prove to yourself it was done correctly, or at least has the same result as being done correctly...

Often around here... somebody drops the minus sign at the nose wheel...  this misplaces the reference point... the bolt indicated BT the plumb bob...

 

If you aren’t familiar with Statics problems, and haven’t done a fair amount of math...

Start a new thread...

Detail all of your effort...

In the end... there is one unique answer for your plane, today.

It takes a fair amount of effort to get it done right...

PP thoughts only, not a mechanic...

Best regards,

-a-

[RLCarter]

On 4/26/2021 at 10:01 PM, Roberts13t said:

I have a few ideas on some errors but I want to hear from the experts as I’m really new to mooneys. Thanks for the help!

So what was your theories on errors? I went through the motion on mine because I found several W&B sheets in all the paper work that came with plane (several with the date obscured) and had no real way of knowing which was current. If you do it by the book and double ck your math you’ll have a W&B that is correct.