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Sherlock and the Sagging Strut

** As it turns out, there was more than one way
to solve the mystery of Melmoth 2's sagging
main landing gear strut.**
Gemini Sparkle

Key Takeaways:

  • The author's homebuilt aircraft exhibited a perplexing symptom where one main landing gear strut appeared to "collapse" after landing, causing the wing to slump, only to slowly re-extend during taxiing.
  • Initial investigations by the author and other experts, including a strut overhaul, failed to identify the cause, as they focused on a malfunctioning or "sagging" strut.
  • The true nature of the problem was discovered through an online forum: the issue was not a strut collapsing, but rather one strut remaining *over-extended* after landing, creating the subjective impression that the other strut was sagging.
  • This delayed compression was attributed to the aircraft's weight settling too gradually on heavily damped struts due to changes in landing technique, such as using Fowler flaps and increased braking, preventing them from reaching their static height immediately.
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During the summe of 2010, my homebuilt, Melmoth 2, which had been flying for almost eight years, began to display a mystifying symptom. As I turned off the runway after landing, the main landing gear oleo on the outside of the turn would seem to collapse. The wing on that side would slump toward the ground, and because Melmoth’s wings have relatively little dihedral and are completely wet from root to tip, fuel would sometimes even dribble out of the tank vent at the wingtip. Once or twice the local controller at my home field told me that I had a flat tire, but after seeing me taxi off listing drunkenly to starboard a few times, he must have decided that nobody could have that many flat tires.

But here was the bizarre thing: As I continued to taxi, the strut would slowly return to its normal height.

Peter Garrison

Peter Garrison taught himself to use a slide rule and tin snips, built an airplane in his backyard, and flew it to Japan. He began contributing to FLYING in 1968, and he continues to share his columns, ""Technicalities"" and ""Aftermath,"" with FLYING readers.

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