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DISCUSSION: LongEZ Weight and Balance
I belong to a local EAA chapter (582). Many of these chapters own or have access to aircraft scales. Consider doing your Weight and Balance as part of an "EAA Builders Meeting".
This is an excellent way to get helpers, and a lot of extra eyeballs double checking everything. I almost guarentee someone in your local EAA chapter has done this before.
The LongEZ Pilots Operating Handbook is the final authority. This discussion is not meant to replace it.
DOWNLOAD LongEZ Pilots Operating Handbook.
Like any aircraft, An accurate Weight and Balance must be performed on the LongEZ to determine if it can be safely operated within the design Center of Gravity envelope.
Carefully review the Pilots Operating Handbook.
There is an excellent discussion on weighting the LongEZ, and performing some basic measurements to ensure that the correct geometric relationship exists between the Canard and the Main wing.
The geometry and measurements between the Canard and the Main wing are important.
If these measurements are not within the tolorances shown, then the CG envelope specified in the Pilots Operating Handbook are not valid for this airframe.
The following spreadsheet can be used for calculating CG and performing a Weight and Balance.
The spreadsheet is locked to prevent accidental manipulation of the formulas.
HOWEVER, the password is LongEZ, in case you need to change one of the critical cells.
Print out several hard copies of this to document measurements and scale readings.
DOWNLOAD LongEZ Weight and Balance Spreadsheet.
LONGEZ MEASUREMENTs
The aircraft needs to be completely assembled with all accessories and covers installed. Ready for flight. Ensure the tires are inflated to their operational pressures.
The fuel tanks should be empty. Fuel shifts around and its exact location is hard to predict. Empty the tanks.
For best results, the plane needs to be on a hard, flat, level surface. You will need a level, plumb bob, chulk line, and measuring tape.
1) Extend the nose gear and place a temporary weight so it straddles the leg hole in the instrument panel.
Place as much temporary weight (25 lbs ??) as necessary to ensure the plane will not fall over backwards.
The weight of this temporary weight needs to be known with a good degree of accuracy. ALSO, The location (FS#) of the temporary weight needs to be known.
CAUTION - Even though the nose is weighted down with the "temporary weight", the plane can still be tipped back with even a small amount of downward force at the wing tips, propellor, or any lifting force at canard or nose.
I brief my helpers to never touch the plane without specific instructions from me.
DO NOT LEAN AGAINST THE PLANE, IT WILL FALL OVER BACKWARDS
As an extra precaution, I place an extra 50lbs in the pilots seat while the plane is being moved about and being prepared for the scale readings.
I then remove this extra precautionary weight just before reading the scales. After the scales have been read and double checked, I then place this weight back in the pilots seat
2) Level the plane in both pitch and roll, use small pieces of foam or lumber to achieve this level.
If you have two levels, this is better, use one for pitch and one for roll. Duct tape the levels into position so they don't fall over while moving and leveling the plane.
Do NOT partially retract the nose gear to achieve pitch level. The nose gear must be fully extended.
3) Refering to the Pilots Operating Handbook and the two drawings above, drop a plumb bob from the locations identified. Mark these on the floor with a chalk mark.
4) Double check all the chalk marks on the floor. When confident that all marks are accurate, carefully move the plane out of the way.
5) Refer to the drawings and the Pilots Operating Handbook, connect the plumb bob marks using a chulk line.
6) Using a tape measure, measure forward 40 inches from the instrument panel REFERENCE line. Mark this as FS#0. All other measurements can now be measured from this line.
There is a note in the Pilots Operating Handbook regarding the wing and canard measurements;
Basically, it says the following, if the measurements below are not correct (using FS#0 as described in step 6), but are correct in relation to each other, then renumber the Instrument panel FS# to correct for the error.
EXAMPLE, ALL the measurements taken below are 1 inch greater then specified, then the FS# desigination for the instrument panel can be modified, i.e FS# 39 instead of FS#40.
Make this change on Weight and Balance spreadsheet, Then repeat Step 6, but use the new FS# (39), The measurements should now be within tolerance.
7) Measure and record from the FS#0 line to the following lines.
NOSE GEAR = 19.5 ( Tolerance not critical - But the measurement must be accurate to compute W&B)
MAIN GEAR = 110.5 +/- 1.0
CANARD = 18.6 +/- 0.3
WING ROOT = 113.9 +/- 0.3
WING TIP = 156.0 +/- 1.0
LONGEZ WEIGHING
When you've completed the measurements, the plane can now be weighed. The best way to do this is with three scales, but if your careful and diligent, equally accurate results can be achieved with two, or even one scale.
The weights on the mains will typically be 350 - 550 lbs. Normally, the left and right will be within a few pounds of each other.
If you see a large difference i.e. more than 10 lbs, make sure you know whats causing this difference before proceeding.
Having a Difference could be a symptom that one of the scales isn't reading correctly (i.e. side load, tire not centered, etc)
The weight on the nose will be 10 - 30 lbs, depending on the weight and location of the temporary weight installed.
When the tire(s) are on the scale;
1) The top longerons must be level in pitch and roll.
If you have two levels, this is better, use one for pitch and one for roll. Duct tape the levels into position so they don't fall over while moving and leveling the plane.
Shim the mains and/or nose to achieve level while the plane is resting on the scales.
Do NOT partially retract the nose gear to achieve pitch level. The nose gear must be fully extended, the same position used during the MEASURMENTs.
2) The EXACT weight and FS# must be known for any temporary weight used to keep the plane from tipping backward.
Put this temporary weight in a location where it won't get bumped or fall off the plane. Resting on top of the battery (don't short out the battery), or the leg holes in the instrument panel are good examples.
Double check the position of the weight before taking scale readings.
3) The main gear must be unsprung.
Getting the gear unsprung is normally EZ, just lift one of the wing tips. However, because the nose gear is extended, The plane will tend to turn when you do this. Have one of your helpers hold the other wing to keep the plane from turning.
4) The tire must be in the center of the scale plate.
5) There must be no side forces exerted to the scale surface.
Keeping the tire in the center of the scale is EZ, but making sure there are no side forces on the scale is a little more difficult.
Professional scales have a grease plate (two metal plates sitting on each other with grease in the middle).
The grease plate sits on the scale, then the tire sits on the grease plate. This allows the tire to slide sideways, and relieve any side forces on the scale.
Any two pieces of flat clean metal will work, I've even used one piece of metal, then smeared grease on the tire were it sits on this plate (messy). Regardless of how its done, you must ensure there are no side forces on the scale.
6) READ THE SCALES
After reading the scales, double check items 1 through 5 again.
7) Make corrections to the scale readings or make sure scales are ZEROed
The scale reading may need to be adjusted to take into consideration the weights of any shims or grease plates.
8) If you do not have three scales, then you will need to repeat this entire process after moving the scale to its new location
LONGEZ WEIGHT AND BALANCE SPREADSHEET
At this time, you need to review the Weight and Balance information located in the Pilots Operating Handbook. In particular, locate the chart that shows the operational weight and CG limitations for the LongEZ. Note that there is an Operational envelope, and contained inside, is the "First Flight Box".
WARNING - RAF issued a change to the Operational envelope, The AFT CG limit is changed from FS#104 to FS#103.
DOWNLOAD LongEZ Weight and Balance Spreadsheet.
When finished, move the plane off the scales and park it on its nose.
After you enter the corrected scale readings and FS# locations into the spreadsheet, your instantly rewarded with an aircraft Empty Weight and Center of Gravity.
Now enter the proposed Pilots weight, Fuel, and Oil. You'll see the impact these have on the TOTAL WEIGHT and ARM (CG).
The PERMANENT BALLAST cells on the spreadsheet are provided to allow you to change ballast status that was NOT part of the original weight. For instance, After weighing, you may need to add or remove Ballast in the nose or tail to correct for a forward or aft CG condition.
Simply enter the weight (minus if you are removing) and FS# in the PERMANENT BALLAST cells and you'll see the effect the ballast has on the TOTAL WEIGHT and ARM.
NOTE: If a permanent ballast was installed when you recorded the weights, DO NOT reenter it here. The ballast weight and FS# are already part of the weighing process.
HOWEVER, Make a note on the W&B worksheet that the ballast was installed and is part of the basic weight. This will eliminate any confusion later as to the status of the ballast.
ADJ (adjustment) cells are provided on the spreadsheet and can be used to make adjustments, additions, and deletions to the Weight and Balance calculations without reweighing the plane.
CHANGING AN ITEMS WEIGHT and LOCATION:
EXAMPLE - Rather than add ballast to correct for an aft CG, you've determined that you can move the 22 pound battery forward by 18 inches. There's no need to re-weigh the plane, simply enter the corrections on the spreadsheet.
NOTE: If an item is being removed from the plane that was installed in the plane during the initial weighing process, then enter its weight as a MINUS (we are subtracting its weight from the plane).
In the ADJ1 cells, enter the original battery weight (minus 22) and FS# (19), Battery is removed.
In the ADJ2 cells, enter the new battery weight (22) and FS# (1), Battery is installed.
You'll see the effect of changing the battery location in the TOTAL WEIGHT and ARM cells.
Once you're satisified with the results, Print them out and transcribe these numbers to your Pilots Operating Handbook.
WARNING - Double check the math by using a calculator and computing the Weight and Balance from the figures you entered in the Pilots Operating Handbook.
Final Note - The Weight and Balance is a document that will be inspected in order for you to receive your Airworthiness Certificate, and must be carried in the plane at all times.
Your FAA inspector will question you about the procedures and techniques used. You must be completely familiar with this procedure.
If you have any questions or comments, please contact me;
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