Odd.
Some 912 Kitfox owners have had the opposite problem with the carb springs
pulling the throttles open.
Duncan McFadyean
-----Original Message-----
From: J Moran <jmoran01@earthlink.net>
Date: Wednesday, August 08, 2001 3:17 PM
Subject: Throttle Cable Considerations
>
>I recently had a landing accident in N44EU which was
>precipitated by power failure during a go around; N44EU, a Mark
>1, incurred "substantial damage" (FAA assessment). I was
>fortunate to walk away with minor bruises and scratches.
>
>In analyzing the accident later, I concluded from all the
>details of the power failure that the most likely cause was that
>the throttle cables kinked within the throttle block when I
>attempted to rapidly apply full throttle, effectively locking the
>power at the existing setting.
>
>With the throttle at idle, several inches of cable are within the
>throttle lever block and are not constrained by the sheath. When
>the throttle is advanced, the springs at the carburetors normally
>take up slack in the cable. Should the throttle lever be
>advanced faster than the springs take up the slack, the cable can
>loop downwards and kink within the throttle lever block,
>effectively locking the throttle at a setting providing much less
>than commanded power.
>
>I expect that the rate at which the springs can take up the slack
>will vary between aircraft depending on the routing of the
>throttle cables, cable lubrication, and any other friction or
>mass in the throttle cable system. In my case, I used powdered
>graphite lubricant on all cables rather than oil (this to avoid
>dirt attracted by oil) - I doubt that this contributed to the
>problem, but each builder must make a choice of lubricant for
>himself. The awkward part is that dirt, temperature, and other
>unknown conditions could affect the maximum rate of throttle
>application before kinking will occur and this could vary between
>flights. Further, rapid throttle application tends to occur when
>power is needed rapidly so a pilot could exceed the critical rate
>inadvertently.
>
>A further consideration with this throttle system design is that
>should one of the throttle springs break then a similar kinking
>failure will almost certainly occur.
>
>My understanding of the reason the spring is incorporated by
>Rotax is to cause the engine to go to full power should a
>separation occur within the throttle linkage, the concept being
>that having full power is better than having less.
>
>My inquiries turned up another report of a Europa which kinked a
>throttle cable on takeoff resulting in less than full power and
>an aborted takeoff with no serious consequences. This lends at
>least a bit of credibility to my amateur accident investigation.
>
>I don't know whether the XS model uses the same throttle design
>so this may not apply there.
>
>Until the cause is officially established, I believe Europa
>builders who have throttles of the above described design should
>use some care when advancing the throttle rapidly.
>
>John Newtown, CT
>
>
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