Gyro Accident Tasmania

[asra]

I think the pushrod had a section cut out then another piece overlapped and bolted on the side to clear the starter.In my last post I said that if something looks a weak point it usualy is. What I was meaning there is that if the required strength of component is decided purely on the maths all the inputs must be known. As this cannot yet be done for hubbars I doubt it could be done for the torque tube. This is what makes me doubtfull when something is said to be over engineered, but to say double the strength and vibration resistance of the existing torque tube the maths would point out the best way to go.Another thing that could be done to rule out possible causes is increase the teeter travel. I have always had nine degrees teeter travel both ways and considered that the norm.

[Greg Mitchell]

Allan"s teeter travel was more than mine after installing 3.5mm bread board teeter stops. Mine were 4.5mm which I estimated equated to 1 degree of slightly more.Clacs have been done by people with math skills I do not possess and 1 degree is agreed on.The teeter stops were installed when prototyping the MLS so as to prevent the heads of the innermost strap bolt from comming anywhere near the housing. Further the scoring of the underside of the hub bar by metal to metal contact was addressed by the same mod.Essentially we had to prototype the MLS on our gyros because in the US the use DW"s and we use Pat"s!Look on the US forum under accident section and conrtol rod breaks to see a bitmap pic of the spliced rod.Mitch

[Des Garvin]

Hi All,
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[asra]

Des, I"ve got a calculator off the net that tells me a set of 26" blades 2degree pitch 8-h-12 airfoil 15kgs per blade - thats a set of 26" AKs would drop the coning angle about half a degree at 120knt thats about quarter of a degree at 60knt. I"m thinking if a gust of wind or turbulance pushed a blade off track far enough that it hit the prerotator there would only be one strike as I have read that helicopter rotors that have been studied are back on track in one revolution.Chuck Beaty has got a post on the US forum. He set one up with very little teeter travel and got bad stick shake each time he took off because the hub bar was hitting the stops. Thats when the most teeter would normaly occur. I dont know if he flew in any rough weather but he wasn"t getting the stick shake when he was flying. I think the actual amount of teeter required would depend on the blade as some may teeter more than others. I"ve always had nine degrees and thought it the norm but I see Allan and Mitch consider six degrees the norm.I think that Benson calculated the nine degrees. I have never looked it up but I take it there was a reason for that amount of travel. Somebody else may be able to tell you more about it.

[Des Garvin]

Thanks Peterw for your reply. Des Garvin

[Greg Mitchell]

Actually I am not certain now if we have six or nine. What I am certain about is that "we" dont necessarily consider 6 degrees the norm. What I am led to believe is that we only need about +-2 degrees for normal flight and that an extra 4 degrees is enough to facilitate prerotation. Our heads could in fact be 9 degrees as Larry said the head was based on the Bensen head.I"ll double check that.Chuck Beatty also said he doubted the torque tube had broken.Mitch

[joew]

Mitch,How is the progress with finding the Gyro?Joe W

[Greg Mitchell]

G"Day Joe,I believe little has been done since last week. I did hear a reward was likely to be posted.OK, just got off the phone from Larry in the US.Bensen heads have 10 degrees of teeter each direction.Not to be confused with the 9 dgrees forward and 9 degrees back stick giving a totall of 18 degrees.Not to be confused with the 8 degrees of side stick either side giving 16 degrees total.Further, the new MLS torque tubes allow another 6 degrees of movment forward of the horizontal or in addition to the original 18 degrees. This to facilitate the use of the rotor brake, without the need to manually engage.Whilst I was of the belief +-2 degrees was the normal amount of S & L flight, I am informed this morning that is more like 4 degrees.4 from 10 is 6 degrees, take out another degree for the modded teeter stops and now we have 5 degrees left.30 knots blowing on our return flight with 40% STRONGER GUSTS, results in possible 45 knot gusting. Neither Allan nor I were very comfortable at all and were almost back at the strip prior to the accident.I am told getting hit by a gust head on like that will cause the advancing blade at 3 oclock to rise dramatically and by the time it"s at the 12 oclock position may well be close to the stops. Even if it was not at the stops, the longer length of bolt now is likely to strike the MLS housing. Pop Pop.I have redundant straps for the rodends and push rods being made, when they are installed I will be back having fun, flying my Monarch and using my MLS with confidence.I certainly appreciate everyone voiceing their concerns and providing much food for thought.Thanks.Fly Safe.Mitch.

[asra]

The straps for Dave Johnstons gyro.Mitch, I will make yours over the weekend.

[Disco]

Thats a new joystick setup, I"ve never seen one like that before.

[Des Garvin]

Aey Mitch,

[asra]

With ten degrees teeter travel minus pre rotator and bolt interferance, it may be a bit premature to nail that as the definite cause of the accident. I was going to say it might be best to see what ASRA comes up with in its investigation but has anyone been appointed by ASRA to investigate this accident.

[Greg Mitchell]

G"Day Disco,Allan said previously, " I departed the Clarence Point private airfield with Greg “Mitch” Mitchell for a flight to determine the best and safest route for the conduct of a “mass” flyby of gyros the following Friday. This was requested by the organisers of the Three Peaks yachting event due to get under way that day. The participating gyros were to be part of a contingent expected for the annual ASRA National Championships. The return route had us tracking north along the western bank of the Tamar River. I was behind and slightly below Mitch at 1000’ AGL, an ideal position from which to observe the terrain and population density in the general area."We are in no doubt the wind had "picked up" on our return and was at least thirty knots. Allan and I are agreed in that we both felt very uncomfortable in the gusty conditions. We were getting "kicked around" a fair bit, no doubt about that. It took me 4 attempts to land into the wind, in the end aiming for a break in the trees with less rotor comming off the trees. I"m attaching a pic of the basic pump stick on my old setup.Hi Des,Probably

[Ken Watson]

Geez Murray, if the rod end fails there is no way that strap will do anything. Put a rod end under tension using that strap and I know what will fail first.I think you missed the point that it would be serious tension that makes it fail in the first place.I think its a bit of piece of mind thats a bit patronising. I think its a waste of time but if it makes you feel more comfortable then do it. Why dont you just double the size of the rod end.Just my opinion, Ken

[asra]

That small strap is there not to provide a final connection between rod end and tube (Even though it can & does) It is to stop the rod end unscrewing should the rod end lock nut come loose. Rod ends are strong and this is evident in rolled over machines. This is something I will begin to add to my aircraft now on. Great Idea"s gents keep them coming>>>>>Regards SamL...............