Weight and Balance

Sv.grainne

Super Member
Joined
Jan 14, 2020
Messages
2,312
Location
Kerrville, Texas
Aircraft
Aviomania, G1sB Genesis
I plan to purchase and build a single place gyro soon and know that the kit is setup for a pilot weight of 155 - 220 lbs. Once built should a hang test be done? Anything else that should be done as part of W/B to obtain airworthiness certificate?
 
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Hi Bobby
We do a double hang test fully loaded with the pilot to find the center of gravity at the same time. That is our weight and balance checking that the angle is in the manufacture's specs.
The FAA does not always have experience with our method and expects a chart with weight and the moment arms. Our DAR's don't have that problem.
PRA has been asked to call the FAA and explain gyroplane reality to them.
 
Thanks for the response. I asked the mfg about this and was referred to specs, weight empty and max takeoff weight. I asked about cheek plate setup and he said that the plates are set for a pilot from 155 to 240 lbs.

How can you derive arm/moment from CG and weight data?
 
Thanks for the response. I asked the mfg about this and was referred to specs, weight empty and max takeoff weight. I asked about cheek plate setup and he said that the plates are set for a pilot from 155 to 240 lbs.

How can you derive arm/moment from CG and weight data?


I did it once, long ago, with a FW ultralight. If I remember well, I measured the weight under the front wheel, did the same with one of the main wheels, multiplying that by two in order to account for the other wheel. Then I found the point where the moments of the front & main wheels cancelled out, along the estimated longitudinal axis of the gyro. There was the c.g.... Sure not 100% accurate, but enough for paperwork...
 
We do not get a weight or moment arm.
The cheek plates are set (to an angle) for a pilot from 155 to 240 lbs is the answer.
You make sure it hangs within the cheek plate angle set by the manufacture.
 
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I did it once, long ago, with a FW ultralight. If I remember well, I measured the weight under the front wheel, did the same with one of the main wheels, multiplying that by two in order to account for the other wheel. Then I found the point where the moments of the front & main wheels cancelled out, along the estimated longitudinal axis of the gyro. There was the c.g.... Sure not 100% accurate, but enough for paperwork...
That's works for CG and checking the angle when balanced at the CG point.
The DOUBLE hang test lets you mark where on the mast the center of gravity is so we can adjust the engine to as close to CLT as we can get it and check the angle.
 
That's works for CG and checking the angle when balanced at the CG point.
The DOUBLE hang test lets you mark where on the mast the center of gravity is so we can adjust the engine to as close to CLT as we can get it and check the angle.


I see... Thanks for the info...
 
I plan to purchase and build a single place gyro soon and know that the kit is setup for a pilot weight of 155 - 220 lbs. Once built should a hang test be done? Anything else that should be done as part of W/B to obtain airworthiness certificate?


The CofG, weight and balance, and correct keel angle of a gyroplane in flight is determined by conducting hang tests of the aircraft full fuel and pilot on board. The first hang after removing the rotor blades and suspending the aircraft by its teeter bolt, free from contact with the ground. A line dropped from the point of suspension vertically down and position along the gyro noted. A second suspension is made with the rotors on and a second line vertical down made and noted. Where these intersect is the CG.

Keel angle in flight, determined by suspension from the teeter bolt and a measurement then taken, either at the keel or the rotor mast, to determine how many degrees from level the gyroplane hangs. This must be within a range of 9 and 14 degrees with the Cyclic stick in a neutral position to ensure safe and effective control stick movement. This measurement taken with fuel tanks full then empty to account for fuel burn in flight.

The second hang is the one that determines the where cheek plate holes are. Test cheek plates can be made with slots so a correct keel angle can be obtained and the placement of the cheek plates bolts holes then determined.
 
Thanks Leigh. Mfg told me that the cheek plates come drilled and the machine is already setup. Figured I would have to redo so no big deal. Club I belong to can help with this. Just trying to gain some understanding. I weigh 165.
 
That's works for CG and checking the angle when balanced at the CG point.
The DOUBLE hang test lets you mark where on the mast the center of gravity is so we can adjust the engine to as close to CLT as we can get it and check the angle.


John:

Gyro is being sold in Europe as ready to fly and as quick build option here in the US so assuming no changes needed for engine placement.
 
It will hang in spec's then no worries.
It's interesting to learn how far off CLT it is???
As long as the HS is far back, large enough, and has air moving over it (= Not at the top of a zoom climb) it will compensate for non-CLT design solely adding drag to compensate. Autogyro's need a larger HS as there are pitch incursions on power changes in the two models I've flown. however not a big deal unless the engine quits just as you lift off or at the top of a zoom climb as all pilots will just move it back to the horizon or attitude required.
 
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