Europa-List Digest Archive

Mon 06/06/11


Total Messages Posted: 2



Today's Message Index:
----------------------
 
     1. 12:28 AM - Re: N127ZP Landing gear failure. (JonSmith)
     2. 02:00 PM - Re: 912ULS ignition failure update (jpg12305)
 
 
 


Message 1


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    Time: 12:28:50 AM PST US
    Subject: Re: N127ZP Landing gear failure.
    From: "JonSmith" <jonsmitheuropa@tiscali.co.uk>
    Hi, I was very sorry to read of your misfortune. It must be heartbreaking. With luck the damage to your lovely looking plane will be just the retract handle, strut mod and a new guide plate. (Engines and props are just bolt on accessories!!) Just a few thoughts from me: As the retract handle is still in the "down gate" the over-centre locking mechanism has obviously failed to do it's job and has let go for whatever reason. Certainly this should not be able to happen so I feel it must be considered that something was not quite right with your set up. It may or may not be possible to determine now what it was but either way I'm sure that when you repair and check things it will definitely be possible to avoid it happening again. I believe that during the initial build (and in the uk, at each annual inspection) there are two critical considerations: 1/ The geometry of the set up must be correct. 2/ There must be no wear or play in any of the system which might allow this otherwise correct geometry to alter. Nb. The following must be finally checked with no weight on the wheel, ie. aircraft hoisted. 1/ Geometry: (a) The LG8 arms must contact their respective stops together and be parallel to each other. Furthermore when the arms are on their stops the front edge of the retract lever must be hard against the front edge of the "down gate" on which it reacts. The lever holds the arms against their stops so there must be no gap here whatsoever, just a tight sliding fit so that you can actually move the lever laterally in and out of the gate. If there were to be any gap here then any vibration in the system could cause the lever to move forward slightly thus partially retracting the undercarriage and bringing the "over-centreness" of the lock to a critical point where it might go past the point of no return and collapse. If it was to go past that point with the weight of the aircraft on the wheel then nothing will save it! (b) Furthermore, with the gear down and locked, the amount of over-centre must be checked to be correct. An accurate method of sighting up (the centres) must be devised. The middle pivot point (top reaction plate clevis pins) must be min 1/16' and max 1/8' forward of the top pivot point (LG8 mounting shaft) and bottom pivot point (LG04 pin). Too much puts extra strain on the LG frame, too little and the over-centre lock would be critically 'weak'. To achieve this the LG8 stops must be the correct length. They 'should' be correct from manufacture but I have heard of some people having to grind them down a bit and/ or adding to the length to get the amount of over-centre spot on. Finally the pre-tension of the rubber block must be set correctly to achieve the correct result (79mm between inner faces of the top and bottom reaction plates). 2/ Wear: Any wear or play anywhere in the system could cause movement which might critically affect the geometry, possibly allowing the over-centre to become critical and collapse. Namely, wear in any of the pivot points and bushes, wear/ slop developing in the joint between the retraction handle and the port LG8 allowing unwanted movement of the handle relative to the gear (though I notice you have the strut mod so this should have been ok.) etc. Could it possibly have been that on yours you may have had some gap at the front of the gear handle, or maybe the LG8 stops were slightly too long thus not giving a safe amount of over-centre? These seem to me to be the most likely causes. I'm not opening the oft-argued debate about which version of the Europa is best again. (Monowheel IS the best one!!!!!!) Good luck and Regards, Jon -------- G-TERN Classic Mono Read this topic online here: http://forums.matronics.com/viewtopic.php?p=342167#342167


    Message 2


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    Time: 02:00:51 PM PST US
    Subject: Re: 912ULS ignition failure update
    From: "jpg12305" <jpg.comm@laposte.net>
    Good to know you are back in the air. I know this drove you mad, but the positive thing is the shared experience. See you soon, probably in Blois early July, weather permitting. Jean-Paul LFEF Read this topic online here: http://forums.matronics.com/viewtopic.php?p=342243#342243




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