COG testing questions

[maulonir]

Hello,I have a couple of questions regarding the hang /tilt back testing and was hoping someone from the board may be able to help me out.My machine is a dominator style tandem with 2 seat tanks.

[asra]

Hi Rob,Just do the tests 1 up empty,2 up empty,1 up full,2 up full.The thrustline on your gyro will definitely be below the COG but it will be interesting to see how far,if any,the COG migrates downwards with a full fuel load.I only ever flew that machine with the rear tank full two up. It is unlikely it would leave the ground two up with both tanks full.If you wanted to placard that the machine must only have fuel in the rear tank when two up then you can do the tests with that in mind.Do the hang test whichever way is the easiest for you and if you need a hand with some extra bods give me a ring.

[maulonir]

Thanks Murray,I can manage finding the COG using the hang method. I will do the full test just to see the results rather than placarding. I have a 912s ready to install which wiill mean doing it all again however it will still be some months away before I get time to fit it.Rob

[Waddles]

Rob,I know from the testing of my gyro that the results can be skewed for reasons yet undetermined. I"ll have to do the whole lot again!Furthermore, I have proposed to the Board an alternate method for gyros that will determine the most satisfactory manner in which to conduct these tests and get definitive results that will be good for the life of the gyro providing that modifications are not made.The Board has not yet ruled on my proposition, but suffice it to say that the survey is showing that a perhaps broader approach is required, something that was expected at the time. It"s all about getting consistent results across the board for the ultimate benefit of all.This is only phase one and the results will take some considerable time to collate and analyse. I"ll post my results here when I"m happy that they are done properly and accurately.Regards,Waddles.

[asra]

Hi RobHere are a few pics of a recent hang test we completed on a Dominator. The owner was happy for me to post these 2 pics in order to possibly help you.Give me a call should you like to discuss this further.Regards SamL...............................

[willatodd]

pardon my ignorance but is there a simple way to explain the intersecting lines and how to tell from here what is clt. i have not yet been able to afford my own gyro but have been flying the mto sport and not sure if i understand it properly as i havent had to do it myself.

[tonydenton]

sam,did you have multiple people to lift and tilt back and then just balance it with one person for the photo or is every one stronger in victoria. . i think what some have been worried about is if the weight of the machine starts to come down and that person can"t hold it up then there is a possible drop happening or the guy could try to keep up his end of the bargain and do a personal injury. either way your posts / photos and lines have been very helpfull. also as asra has asked the mere fact that it"s getting done is showing up what"s what. some are interesting some are eye openers, definetely moving forward that"s the main thing.

[asra]

sam,did you have multiple people to lift and tilt back and then just balance it with one person for the photo or is every one stronger in victoria. . i think what some have been worried about is if the weight of the machine starts to come down and that person can"t hold it up then there is a possible drop happening or the guy could try to keep up his end of the bargain and do a personal injury. either way your posts / photos and lines have been very helpfull. also as asra has asked the mere fact that it"s getting done is showing up what"s what. some are interesting some are eye openers, definetely moving forward that"s the main thing.Hi TonyOur normal procedure is to do the hang test empty with blades on. We then lower it onto the ramps as shown placing the front wheel on a create to level the machine. Now we lift the front (1-2 people) and balance it which 1 person can do with 2 fingers. We now lower its nose down again and fill the tank to full. Raise nose again for another balance test, then lower. Finaly we lift machine via its Hbar for final (full fuel) hang test and its done. This technique is far the fastest and easiest we have found here. I should point out I have now completed 20 without any issues or near misses.The key is for 1 person to coordinate, requires prior planning, check everything as you go, take no chances, and don"t rush anything.Safe hanging gents