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  1. #1
    Trainee Pilot Dragonfly7861's Avatar
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    Dragonfly Engine Failure - Bailey V4

    A spot of excitement yesterday. At 300' on climb-out I noticed a slight change in engine note, followed about ten seconds later by a complete engine failure. I had turned to stay over the airfield as soon as the engine went sour so when it failed I was in an easy position for an uneventful engine-out landing on the cross runway with 4000' remaining at touchdown. I always operate only over landable terrain and take a very conservative approach to takeoff and landing routes and this paid off this time. On the ground I pulled the little aeroplane clear of the strip by hand and expected to find an oiled plug or a separated lead in the ignition circuit, something like that, but alarmingly on checking switches off and feeling for compression back at the hangar it was clear there was no compression at all. Oh dear, I thought. The engine turned freely without distress so I opened the tappet cover expecting to find a stuck valve, but in fact engine rotation did not actuate the valves at all. What evil sorcery is this, I wondered. Removal of the cam chain access cover revealed all. The cam chain was derailed from the cam drive sprocket and was sitting behind the sprocket. Both sets of valves appeared to be closed, but the lack of compression indicates one set is cracked open. This is a single cylinder engine with two inlet and two exhaust valves. Each pair of valves is operated together by a forked arm from one exhaust lobe and one inlet lobe on the cam shaft. Hopefully, there has been no collision between valves and piston. The cam chain is intact and turns happily with the crankshaft. I'm unable to see whether the tensioner is still intact, but I suspect that the tensioner has failed, allowing the chain to jump off the sprocket. I think this might be a repair job for someone with a lot more expertise than I possess, so the hunt for a repair venue has begun. I've asked Paul Bailey for advice, having found him most responsive and helpful in the past. This model of engine is not listed on their web site now, but hopefully parts will still be available. The engine is six years old, had 132 hours on it, and has been maintained as per the book. Does anyone have any experience of a similar event with a Bailey V4?
    Last edited by Dragonfly7861; 19-11-17 at 10:26 AM. Reason: Error in Engine designation


  2. #2
    Trainee Pilot Dragonfly7861's Avatar
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    A quick update. Paul Bailey has offered to repair the engine if I send it to him, but I think this might all get a bit expensive from out here in The Colonies. Closer examination in my workshop indicates a cam-chain tensioner failure is indeed the problem. I will strip the head and barrel off and see what the tensioner has been up to and check for any collision between valves and piston, then proceed from there. I shall keep you all updated as we go.


  3. #3
    Co-Pilot BobH's Avatar
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    Dragonfly7861,

    The worry is that the reason you have no compression is because one or more valves may have bent, thus causing it to seem open all the time and preventing any compression. Let's hope not.


  4. #4
    Trainee Pilot Dragonfly7861's Avatar
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    Bob, exactly. The head will need to come off for a careful examination of the valves, in all likelihood there will be bent valves (or worse). Work and the flu have stopped me getting on with it yet, but the schedule is clear beyond mid November and I'll get stuck into it. I hope parts can be supplied, some here in Australia have reported difficulty with getting spares from Bailey. We'll see. Thanks for the comment Bob, Cheers.


  5. #5
    Trainee Pilot Dragonfly7861's Avatar
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    A short update. I have checked with the organisation responsible for ultralight aviation here, RAAus, and legally I am allowed to work on my aircraft provided it is not provided to anyone for hire or reward. So, with the legalities out of the way, off comes the head. Photos and details of the journey as they become available. I notice that Ben Ashman is now offering Dragonflies with Polini and CorsAir engines rather than the Bailey. Hmm... Does anyone know if conversion kits are available?
    Last edited by Dragonfly7861; 19-11-17 at 10:28 AM. Reason: Added Test


  6. #6
    Co-Pilot D-Flyer's Avatar
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    Hi

    I know of at least one owner who has taken the Bailey V4 off and fitted a Polini instead - some adjustments to engine mounts I think is all that's required. Ben will help I'm sure!


  7. #7
    Trainee Pilot Dragonfly7861's Avatar
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    D-Flyer, as you predicted, Ben Ashman to the rescue. He has kits available to fit the Cors-Air M25Y or the Polini 130 or the Polini 250. The kits include a new lower monopole, new engine brackets, a wiring loom adaptor, new fuel system components, and a new prop. Given that I soar the Dragonfly a lot and do little cross country, I think the Cors-Air is the engine for me. The Australian distributor (Adelaide Airsports) is going through the process of getting approval for this modification. Sadly, we in Australia do not have SSDR regulations so we must define the modification to the authorities. Given that the M25Y engine is the current Dragonfly production variant, and the conversion kit is from the original equipment manufacturer, one would think this is simple, but.... not here in Oz. We'll get it done, and I'll let you know how it goes. I will also post strip-down photos of the damage to the Bailey for information. Strip down is planned for tomorrow afternoon. I will be turning my little Bailey into a wall ornament, complete with propeller. It should look nice on my workshop wall.


  8. #8
    Trainee Pilot Dragonfly7861's Avatar
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    IMG_0566.JPGIMG_0570.JPGIMG_0573.JPGIMG_0574.JPG IMG_0572.JPG
    Here is the damage inside the little Bailey. In the first photo it is clear that the valves and piston have not collided - lucky indeed. The second photo shows the source of the failure. There is what appears to a guide arm attached to the cam sprocket and this has failed at the attachment at one end resulting in the arm flailing around and mayhem to surrounding structure. Photos 3 and 4 show some of the damage to the structure around the cam bearing and to the inside face of the cam cover plate. The arm itself is badly blued, distorted and butchered. The engine stoppage was sudden and total - but clearly trouble brewed for some time, with the engine finally crying enough when the cam chain was dislodged and derailed by the failed arm. The cam chain tensioner seems fine by the way, the failure seems to have only involved this arm device which is attached to the cam sprocket. I don't understand the function of this arm, but it doesn't really matter because in my view the engine is too badly damaged to be re-built, so it will become a wall hanging in my work shop. I plan to retrofit a Cors-Air M25Y engine which is one of the engines used by FlyLight on Dragons currently for sale. In effect, I will be bringing it up to current factory specification. Can anyone tell me what this arm jigger is for? It was sprung and would seem to have put outwards pressure on the cam chain as the assembly rotated. I've not come across this before. Total time in service for this engine was 132 hours. Operate these wonderful little aircraft conservatively, engine failures can and will happen, that's my advice. No crossing tiger country, no flying over large bodies of water, only fly where a survivable landing is possible - much like the way in which pioneer aircraft were operated, in fact. I'll let you all know when the Dragonfly is airborne again.


  9. #9
    Trainee Pilot Dragonfly7861's Avatar
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    Last update on this thread. The Dragonfly is now fitted with a brand new CorsAir Black Devil engine and is flying again. I do miss the easy starting and gentle nature of the Bailey, but I'm getting used to two-stroke life and the extra power is nice. Thanks to FlyLight for their conversion kit which worked a treat and to Larry at Adelaide Airsports for doing the modification and paperwork for me. Thermal season is upon us down here and I saw pelicans soaring the other day so I'm off to join them. Cheers all!

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  11. #10
    Co-Pilot D-Flyer's Avatar
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    Glad to hear you're back in the air... I've heard of others over here in Blighty that have followed the same route to resolving the Bailey issues, and feedback after a couple of years seems to be very positive, so hope you have the same experience!
    <Insert wit here>


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