View Full Version : Correct method to do a Hang test.
11-08-2004, 07:15 AM
I have been reading many threads regarding this issue, especially the comments Aussie_Paul and Doug Riley have made on the issue.
Iím a little unsure what is actually the correct method to do the hang test.
I have learned by reading a lot of articles, my old Air Command manual ect, that the angle of the rotor head pitch block should be around 2-3 dg nose down. Give or take.
Now, I canít seem to read anywhere if this is with locked pitch block (with wooden wedges or similar) or if it is with the force that the pilot holds the pitch block perpendicular to the RTV
What is most correct??
Also, what about the trim spring??
Does it have to be on or off, or does it not matter?
What Iím looking for is a description on how to do a correct hang test from A - Z regardless witch gyro it is performed on.
11-08-2004, 04:12 PM
It does not matter whether the spring is in place or not.
This procedure applies to a Bensen, Air Command or similar small gyro:
Lock the controls in the neutral position.
Fill the fuel tank half full of water or fuel.
Use a cheap bolt in place of your teeter bolt.
Suspend the gyro by the temporary teeter bolt so that the wheels are all off the ground when you sit in the seat.
When the gyro is hanging freely, the angle of the rotor spindle should be 2.5 degrees forward of vertical. You can measure this angle with respect to the torque bar of the rotor head. If your gyro has a mast that is raked (leans back) ten degrees, then you can also measure the angle of the mast. In this case the angle of the mast should be the same as the angle of the spindle: 2.5 degrees forward of vertical. If the mast has some angle other than 10 degrees, you will have to add or subtract degrees (or simply measure the torque bar's angle instead).
By "forward of vertical" we mean that the top of the mast or spindle is closer to the front of the gyro than the bottom.
11-09-2004, 01:48 AM
Thank you Doug for answering. I kind of hoped you would.
I have done Hang tests with the trim spring attached and removed, but in the future Iíll just leave it in place.
I have also done tests with the torque bar locked or hold by the pilot. I couldnít find much difference between the two. Ok locked torque bar it is.
I havenít used the method you describe here. Do you believe it can be used on a Tandem gyro?
But it is very simple I give you that. Maybe I just use that in the future.
Because there are several people using my Tandem Commander I have always done the hang test so the outer limits were found i.e. different weight in seats with full and empty tanks. This weight limit has always been marked on the seats so there are no confusion. This way it could be that some weight combinations could be higher or lower but the weight limit in the seats has always been decided to be in such a way that no matter what combination the pilot chooses to fly with, he will still be within limits, i.e. 1 Ė 4 dg forward of vertical.
It takes a long time to do these combinations but Iíll rather be safe than sorry.
Doug, how would you do a hang test on a Tandem gyro if you should find the outer limits??
11-09-2004, 03:48 AM
"Fill the fuel tank half full of water or fuel."
Fuel OR WATER???
Isn't this go'n to stuff things up Doug,with water being nearly twice as heavy as fuel?
11-09-2004, 03:56 AM
Water is 10 lbs per Imperial gallon, and fuel 7.2 lbs per Imperial gallon.
Bidy if you half fill it with water then it does not matter about the hang test, as the engine will not start!!!!!!!!!! :D
Aussie Paul. :)
11-09-2004, 04:05 AM
I think Brian uses liters. It still won't run with water though. Thank you,Vance
11-09-2004, 02:25 PM
Birdy -- won't engines run on water in OZ like they do here in the states?
Water, at 8.2 lb. per gallon, weighs about a pound more per gallon than gasoline. Not too serious an error with a half-full tank the size we use on gyros. I suggested water for safety (an idea I stole from Ralph Taggart).
It won't be safe unless you dry the tank out before running the engine, though.
11-10-2004, 04:32 AM
Another day lived,another lesson learned.
Gees,at this rate I'll be able to take the S outa SCG....................in another 10 years.
11-10-2004, 01:33 PM
Awe come on Birdy, your bragging like I do all the time, 15 years!!!!!!!! is more like it. It took me 20 years.
Aussie Paul. :)
11-10-2004, 01:54 PM
Doug, I just performed a hang test on my KB2; from the keel it was 13 dg down with me sitting in it with seat tank about 3/4 full (fuel). I was told it should be between 9 and 12 dg down. Being that close could I just put a little weight aft rather than change the cheek plates (at least temporarily)? stuart
11-10-2004, 02:49 PM
Stuart, does your keel make an angle to the mast of 9-10 deg back from vertical? Is your rotor head attached to the mast so that, when the head is neutral, the spindle is parallel to the mast's long axis? (I THINK the KB-2 is just a 1970 Bensen B-8M, which does have these specs, but I wanted to be sure).
If so, then, yes, you could move something aft to get the gyro within spec. It would be a shame to ADD ballast weights just to avoid cutting new head plates.
Are you much heavier than the average guy or have you made some mod that results in this extra nose-down angle? A gyro built to plans with a 200-ish pound pilot, a 2-stroke engine and normal fuel quantity and location will normally not need any fiddling with the head position...
11-10-2004, 06:06 PM
Geeze Stuart, have you been eating lots of biscuits and cheese burgers? :D
Stuart could add another person to his gyro and still be in limits on weight. :D
Sorry Stuart, I couldn't help it, I still think it's funny, you told me at ROC that this is the only thing you have ever done, where people envy you for your body! :eek: :D
Doug, I think Stuart weighs about 140 lbs after thankgiving dinner. :p
11-11-2004, 06:18 AM
If so, then the gyro ought to hang too nose-high rather than too nose-low using stock head plates. OTOH, if he already moved the head back knowing he was light, he may just have moved it too far back.
If it's hanging nose-low AND the head plates are stock, the mast angle is stock and the machine has some typical gyro engine (i.e. not some 50-lb. turbojet), then I'm stumped.
11-11-2004, 06:35 AM
The headplates were re-made, and he has a MAC 72. The biggest problem he had down in Macon, was keeping the nose wheel on the ground with him in it, and taxiing.
11-27-2004, 07:05 AM
Hey Guys, Thanks Doug and Scott, sorry I got real busy and didn't go back to this thread to read y'all's comments. Scott when we redid the cheekplates to enable me to keep the nose down during taxiing we didn't rehang it; when I got ready to start flying down here I rehung it just to be sure, and that is when I found that it was now too far nose down. Oh, and Scott, That's 142 lbs! stuart
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