The gyro hang test

It is vitally important that the gyro be balanced properly, or in other words, the CG ( center of gravity) must be right.

To have the machine out of CG and fly in a nose up condition is very dangerous and the same is true for an extreme nose down attitude. So to be sure the CG is correct, the the gyro is is given a hang test.

When the gyro is constructed, it is given a hang test before the first flight. If later on changes are made to the gyro, such as adding or removing weight or modifying the gyro then it must have another hang test before flight.

In the photo above my friend, Teddy Udala, is preparing for Dave Bacon, another gyro pilot friend to do a hang test on Teddy's gyro. Teddy built the gyro awhile back then decided to make some changes such as shortening the mast , lowering the seat, and several other modifications, thus the need for a hang test to see if the center of gravity had changed.

So, early one morning before the wind came up we took Teddy's gyro the the gate-way and winched the machine up off the ground. Teddy then got into the seat.

Teddy's gyro is based on the Bensen design and as such it is supposed to hang between 0 and 3 degrees nose down for the CG to be correct.

To do the hang test, the pilot sits in the seat of the gyro with all wheels off the ground and holds the control stick centered...that puts the torque tube ( which is up under the rotor head) in a level attitude. The nose down angle is measured at the back of the mast by someone, in this case, Dave Bacon , holding an angle finder against the mast and reading where the needle points. Teddy's CG came out at 3 degrees nose down. So it was within CG limits. Had it not been in CG he would have had to make new head plates to get the CG right. Teddy was saved a lot of work because nothing had to be changed on his gyro...it was ready to fly.

My Bensen gyro had recently had a starter and a battery added to the gyro...that came to a total of 30 pounds that was added to the machine. I feared the worst. I thought it would be so out of CG that new head plates would have to be made and I had nearly worked myself into a tizzy thiking of all the work that would need to be done because of the added weight.

But to my great delight, the nose down angle of my gyro when we gave it the hang test came in at 2 degrees nose down. YIPPEE!! The CG was perfect and no new head plates were required.

The 30 pounds we had added had been pretty evenly distributed with half the 30 pounds

added to the engine and the other half more up toward the front...that may be why the CG was still OK. All I know for sure that it IS Ok and ready to fly!

And I did make a brief flight with the new starter during the fly-in. I flew from my hangar out to the fly-in site on the lake bed. Not more than a mile altogether but after getting there and making a couple of passes , it was quite enough flying for the conditions . The day was 103 degrees and that put the density altitude somewhere over 6000 feet...not ideal conditions for flight.

I am looking forward to doing some flying and getting the feel of the gyro with the added weight

on it. Oh the thrill of just turning on the ignition switch and then pushing the start button to get the Mac going !

After I get some time on my gyro with the starter I think we are going to add those wonderful tuned exhaust expansion chambers to the gyro this winter. Then I can stand that gyro on it's tail and go straight up on take off...well, I used to do that but I will tame it down some this time.

Till next time.

Marion Springer