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- Sep 13, 2011
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I don't suppose I'm the 1st and I probably wont be the last .... but hopefully it's worth sharing a fairly unpleasant experience I had in my 'S1 a couple of weeks ago
My elevator trim cable was made from 0.075" steel wire as per plans. It was new in 2011 and had logged 325 hours of predominantly aerobatic flying (so lots of "excercise"). 2 weeks ago I took off and climbed to 1500' then re trimmed for level flight @ 130 mph. The trim lever worked, but felt slightly odd - So I added more down trim (which also worked) but when I returned the trim level to level flight there was no change (ie I was stuck on full "down" trim).
At this point I did not know what the problem was (worried about pitch control failure or a jam), so I slowed to 80 MPH, opened the canopy and released the "safety" part of my hooker harness. Although there was a LOT of stick force I established that I could fly the aircraft @ 80mph OK and that I still had pitch control, albeit sometimes using 2 hands as I got more tired (I did consider flying upside down at one point for a rest, but thought better of it)
There was a 12 mile flight back to base and a 3 mile final on "cruise" power with a low descent rate. I chopped the power on the threshold and only used significant back stick at touchdown .... Phew !
Later inspection revealed that the trimmer cable had fractured at the intersection of the solid fuz tube and the flexible outer section near the front of the fin. Fortunately there was enough wire attached to the tab itself (say 30") to prevent it from fluttering - but also enough to keep it at the full "down" position.
Close inspection of the wire shows no corrosion or mechanical damage - my best guess is that it's a work hardening induced fatigue fracture. Virtually impossible to pick up on pre flight inspections though !
I've replaced the wire (available from "spruce" as "Bowden Inner Cable") and just for once in aeroplane world it's a cheap fix !. Going forward I'm intending to replace every 200 hours or 3 years.
In terms of handling the emergency I'm pretty happy with what I did (the "landback" field I'd departed from was only 400m - home base is 715m). However, I'd welcome any thoughts / comments from others with similar experiences.
My elevator trim cable was made from 0.075" steel wire as per plans. It was new in 2011 and had logged 325 hours of predominantly aerobatic flying (so lots of "excercise"). 2 weeks ago I took off and climbed to 1500' then re trimmed for level flight @ 130 mph. The trim lever worked, but felt slightly odd - So I added more down trim (which also worked) but when I returned the trim level to level flight there was no change (ie I was stuck on full "down" trim).
At this point I did not know what the problem was (worried about pitch control failure or a jam), so I slowed to 80 MPH, opened the canopy and released the "safety" part of my hooker harness. Although there was a LOT of stick force I established that I could fly the aircraft @ 80mph OK and that I still had pitch control, albeit sometimes using 2 hands as I got more tired (I did consider flying upside down at one point for a rest, but thought better of it)
There was a 12 mile flight back to base and a 3 mile final on "cruise" power with a low descent rate. I chopped the power on the threshold and only used significant back stick at touchdown .... Phew !
Later inspection revealed that the trimmer cable had fractured at the intersection of the solid fuz tube and the flexible outer section near the front of the fin. Fortunately there was enough wire attached to the tab itself (say 30") to prevent it from fluttering - but also enough to keep it at the full "down" position.
Close inspection of the wire shows no corrosion or mechanical damage - my best guess is that it's a work hardening induced fatigue fracture. Virtually impossible to pick up on pre flight inspections though !
I've replaced the wire (available from "spruce" as "Bowden Inner Cable") and just for once in aeroplane world it's a cheap fix !. Going forward I'm intending to replace every 200 hours or 3 years.
In terms of handling the emergency I'm pretty happy with what I did (the "landback" field I'd departed from was only 400m - home base is 715m). However, I'd welcome any thoughts / comments from others with similar experiences.
