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Aircraft weighing

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gkalin

Member
Getting ready to weigh our new 14. Couple questions: since this is EAB, can I use a set of postal scales…..Amazon sells some for $60 or so. Or do I need to round up something “certified”, assuming there is such. What do paint shops use? Also, understand it needs to be in flight attitude with no fuel, but what about smoke oil? Have a smoke systems helper setup with the tank directly behind the left seat. About 4 1/2 gallons. Weigh it empty, half full, full?
Jerry
 
A lot of us have used the inexpensive scales. They seem to be accurate. I had the occasion to weigh mine with one amazon scale with spacers of the same height as the scale on the other wheels and also with a dedicated set of aircraft scales a DAR had. They agreed within three pounds. Matt had a cool trick that requires only two scales in the second link.



Weighing the aircraft

Has anyone used one of these heavy duty scales to weigh an RV? Capacity is listed as 660 lbs per scale so it seems adequate for our use just not sure about accuracy and longevity. Price is very reasonable compared to "certified" aircraft scales. A few additions and subtractions have been made...
vansairforce.net

Weighing (W&B)

I hesitated to post this till I confirmed. 7A. Standard main gear. Elastomeric Nose gear. I bought three postage scales from the big company. They are branded with the swish. Rated to 600lbs ea. First weigh, I was very meticulous. Airplane level. Scales Tared. Multiple numbers recorded. Pretty...
vansairforce.net
 
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For what its worth, I have used the 600 lb postal scales you get on Amazon for quite a few aircraft. I always check their calibration with known weights, and against each other before a weighing, and they are really pretty accurate and repeatable. One thing to remember - I found this out on my Rocket - they are rated for 600 lbs, and that’s fine for most RV’s. The Rocket has enough mass ahead of the wheels that you can;t jack both wings up and then slide the scales underneath, or it will fall on its nose - you have to jack up one wing at a time and then set the whel down on the scale. Well that is fine for the first one. tehn you go to the other side and jack it up and guess what (everyone see sthis coming….). You put a huge amount of extra weight on the first scale! I bent the heck out of it…and it STILL tested accurate after the weighing. just looks a little funny now….

Smoke oil? Personally I’d drain it - the only fluid I leave in for weighing is engine oil, and I specify how much was in the sump when I do so.
 
gkalin said:
Getting ready to weigh our new 14. Couple questions: since this is EAB, can I use a set of postal scales…..Amazon sells some for $60 or so. Or do I need to round up something “certified”, assuming there is such. What do paint shops use? Also, understand it needs to be in flight attitude with no fuel, but what about smoke oil? Have a smoke systems helper setup with the tank directly behind the left seat. About 4 1/2 gallons. Weigh it empty, half full, full?
Jerry
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Remove the smoke oil and any fuel in the tanks, leave the oil in the engine. Make sure you weigh the plane in a closed hangar. The slightest air movement will cause inaccurate weighing. If you make small ramps it will make it easy to push the plane on to the scales, just make sure that you have a chock on the scale to stop the planes motion. No use learning a new language if it rolls off and you have to start again.
 
Norman CYYJ said:
Remove the smoke oil and any fuel in the tanks, leave the oil in the engine. Make sure you weigh the plane in a closed hangar. The slightest air movement will cause inaccurate weighing. If you make small ramps it will make it easy to push the plane on to the scales, just make sure that you have a chock on the scale to stop the planes motion. No use learning a new language if it rolls off and you have to start again.
Click to expand...
Don't forget to subtract the weight of the chocks, at each location. :)
The FAA defines BEW to include "unusable" fuel and engine oil, no other fluids (de-ice, smoke, etc.).
To be honest, I weighed mine with full fuel, then calculated and subtracted the weight and moment of the fuel.
 
I used the 600lb Amazonian postal scales and a friend's set of expensive racing scales. The two were within a pound of each other. I'm sure others have better tips, but just in case, here's $.02 worth.

One tip I learned the hard way.
Do not lift and lower the airplane on the scales. There's probably a trick to it, but what happens is the gear imposes a side load and results in an inaccurate result. 30 lbs on mine. Unfortunately it gained the 30 lbs when weighed properly!

To be accurate, you need to roll on the scales. So determine how much shim you need to level both ways. Place that on the scales. You probably need some sort of ramp to roll up and on to the scales. You may need to winch the airplane up the ramps.

Another tip
Cut six 12" squares of 4 mil plastic. Grease them lightly then stick the pairs together. Place a set between shims. If there's any side load, the slip pads allow a little movement.
 
wirejock said:
I used the 600lb Amazonian postal scales and a friend's set of expensive racing scales. The two were within a pound of each other. I'm sure others have better tips, but just in case, here's $.02 worth.

One tip I learned the hard way.
Do not lift and lower the airplane on the scales. There's probably a trick to it, but what happens is the gear imposes a side load and results in an inaccurate result. 30 lbs on mine. Unfortunately it gained the 30 lbs when weighed properly!

To be accurate, you need to roll on the scales. So determine how much shim you need to level both ways. Place that on the scales. You probably need some sort of ramp to roll up and on to the scales. You may need to winch the airplane up the ramps.

Another tip
Cut six 12" squares of 4 mil plastic. Grease them lightly then stick the pairs together. Place a set between shims. If there's any side load, the slip pads allow a little movement.
Click to expand...
I "shimmed" to level just by leaving air out of the high tires.
 
wirejock said:
I used the 600lb Amazonian postal scales and a friend's set of expensive racing scales. The two were within a pound of each other. I'm sure others have better tips, but just in case, here's $.02 worth.

One tip I learned the hard way.
Do not lift and lower the airplane on the scales. There's probably a trick to it, but what happens is the gear imposes a side load and results in an inaccurate result. 30 lbs on mine. Unfortunately it gained the 30 lbs when weighed properly!

To be accurate, you need to roll on the scales. So determine how much shim you need to level both ways. Place that on the scales. You probably need some sort of ramp to roll up and on to the scales. You may need to winch the airplane up the ramps.

Another tip
Cut six 12" squares of 4 mil plastic. Grease them lightly then stick the pairs together. Place a set between shims. If there's any side load, the slip pads allow a little movement.
Click to expand...
When I lift the plane on to the scales, I use greased nylon sheets (gift from a friend - a set that I used to set wheel alignment…) to make sure I don’t put any side loads on the scales. You do sort of have to guess where things are going to end up when you do it that way, but its not hard.
 
BobTurner said:
I "shimmed" to level just by leaving air out of the high tires.
Click to expand...
Yes. I forgot that tip. It's a great method to adjust level a little. On mine the mains were much higher and even a flat tire wouldn't level it.

A note to Beringer folks though. If a Beringer tire gets too low, it looses the seal on the bead and will go completely flat. Beringer wheels/tires are not like a car tire. The bead is much smaller and the tire doesn't snap over a bead. The pressure holds the tire sealed to the bead on rim. Airing it back up may not be possible with the airplane weight on the ground.
Tube tires would also be advised not to lower the pressure so far the tube gets pinched.
Thanks
 
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wirejock said:
Yes. I forgot that tip. It's a great method to adjust level a little. On mine the mains were much higher and even a flat tire wouldn't level it.

A note to Beringer folks though. If a Beringer tire gets too low, it looses the seal on the bead and will go completely flat. Beringer wheels/tires are not like a car tire. The bead is much smaller and the tire doesn't snap over a bead. The pressure holds the tire sealed to the bead on rim. Airing it back up may not be possible with the airplane weight on the ground.
Tube tires would also be advised not to lower the pressure so far the tube gets pinched.
Thanks
Click to expand...
 
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