Unknown item in W&B

[JAG]

Hi Jim,
I just looked back at your other thread, and one thing I noticed is the measurements you had for calculating the CofG.

When I measured my points, I came up with:
A (front face of Fwd Firewall to main wheel centers) = 87.8 "
B (Nose Wheel center to main wheel center) = 93.7 "
I took a great deal of time doing the measurements using a plumb bob, tape on the floor, large straight edges, etc. Still easy to mess it up though...

The last W&B on my aircraft had the following measurements: A=88.5" B=94"

You indicated in your last post that they had 96" for B. That may be an error (I am only guessing), and a larger number for that measurement will move the C of G forward.

I would hope all of our early model 337's have the same measurements, but it can change a little (1/4" maybe) depending on who measures and how tight the rigging is on the gear.

Let us know how the next weighing goes and what you find out. One last thing is to move the scales around when you weigh it. When I weighed mine, I jacked the aircraft to set it on the scales. Even though they were calibrated scales, I weighed it a second time (jacked it back up and set it down again) after moving the scales to a different position, just to make sure there was no difference in how they read.

Hope this helps.

Jeff

[JimC]

Originally Posted by JAG

When I measured my points, I came up with:
A (front face of Fwd Firewall to main wheel centers) = 87.8 "
B (Nose Wheel center to main wheel center) = 93.7 "
I took a great deal of time doing the measurements using a plumb bob, tape on the floor, large straight edges, etc. Still easy to mess it up though...

[...]

Hope this helps.

Jeff

It helps tremendously. All I know at this point is that it's very likely wrong. Knowing where it's likely wrong will help me sleep at night. I figured the linear measurements were off - there was no effort made to record a precision of less than one inch. Also, the the weight of my front tire was recorded as 500.0 lbs, exactly. Is it possible? Yes, but I think it's more likely they were using a substandard scale with a precision of 10.0 lbs. Combine that with substandard measurement and you have my W&B.

What REALLY shocks me is that this has been the reference W&B for 30+ years! Either
a) nobody checked c.g. or
b) nobody thought having two 170 lb pilots throw the plane out of c.g. was unusual!

[JimC]

Well, it took almost a year - but I had my plane accurately weighed. As expected, I gained 60+ lbs of useful load and the c.g. moved back almost two inches. I'm still trying to figure out why the c.g. is slightly forward more than the fleet average - I'm at 139.38.

This error has been in the paperwork of the plane for over 30 years!

[patrolpilot]

My '77G just weighed in at 3068 @ 140.

[Learjetter]

Paperwork says I’m at 2968 @ 141.1 ‘77 G model.

But I’m going to weigh her this fall and get an accurate updated W&B.

[JimC]

Those G models are light! I can't figure out how they're lighter than the Es and Fs, when they have the same fuselage as a P-model.

[JAG]

Jim - what is your empty weight? E & F should be lighter than the G given the different interior...

Jeff