Re: LS1 midspan hinge repair

One Sky Dog


I do not have Q plans. From the discussion I surmise an Aluminum arm is bonded to the canard and it failed in fatigue between the hinge at the huge change in stiffness where it is bonded in. Stress follows stiffness change. I chimed in because I seem to remember an accident where this might have been a factor in a inflight elevator failure. I cannot remember details. Fatigue failures are insidious and sadly not considered in plastic airplanes not designed to last a half century. My 767 door springs had to demonstrate 200,000 cycles to qualify. How much testing did the Q Corp do on hinge arms?

For your somewhat off topic question. Dragonfly has tip bearing, 2 mid span hinge arms 4130 steel bonded in and the elevator torque control tube is coaxial and plugs into the elevator hinge tube. Torque loads are transmitted through the Revised bonded in wood rib with a bellcrank and two bolts directly to the skin laminate. 

The Dragonfly elevator flutter issue was using -3 bolts to pin the aluminum hinge tube to the steel elevator control tube in the fuselage that was also pinned together with -3 bolts. The only thing between the hinge tube and elevator skin, 2 lb styrofoam. When things got shaking the bearing strength of the hinge tube was not enough to keep the holes from elongating allowing flutter. No one lost a fluttering elevator which at least took the hinge joints to limit loads.


On Monday, May 9, 2022, 12:42 PM, Frankenbird Vern <smeshno1@...> wrote:

 Charlie.. do our Dragonfly Canards share this issue? If so then I'll be modifying. I figured it was fatigue..and probably from propeller thrust 
variations. Just my guess as to why. First thing that came to mind was adding doublers but I'll look at Jay's solution. My canard has not flown, 
but the hinges are installed. I will be building both elevators new.   

From: <> on behalf of One Sky Dog via <Oneskydog@...>
Sent: Monday, May 9, 2022 7:20 AM
To: <>
Subject: Re: [Q-List] LS1 midspan hinge repair

These center hinges have failed before. Steel is a lot better in fatigue than Al  but if the inflight stress levels are close to the limit it is an insidious problem. It is obviously not a shear failure of they would be breaking upon loading.

Reducing stress is the only answer. This is a materials problem. Either increase cross section, increase load transfer points, or redesign like Jay has done.

Fatigue = repeated cyclic loading below the yield point internal material flaws move to high stress areas over time resulting in cracks and final failure at loads below the design point.

My $0.02 worth of armchair analysis.



On Monday, May 9, 2022, 4:47 AM, Frankenbird Vern <smeshno1@...> wrote:

 Mike.. if Bob or Jim can photo the fail and present it? ..might give some idea of what the cause was.

  Could be from not breaking the sharp edges or possibly the material itself.  .125" is fairly robust so it makes
 me wonder why. 


From: <> on behalf of Terry Crouch via <Q1terryMDT@...>
Sent: Sunday, May 8, 2022 2:46 PM
To: <>
Subject: Re: [Q-List] LS1 midspan hinge repair
There are 6 appendix sheets for the LS1, CS-17 is on the first one.  Send me your phone # Mike and I will send a photo.

Terry Crouch
Quickie N14TC

-----Original Message-----
From: Mike via <n7000t@...>
Sent: Sun, May 8, 2022 12:15 pm
Subject: [Q-List] LS1 midspan hinge repair

Hi all,
I flew my Q200 to Livermore recently to have bob Farnahm ( original builder) help me do my condition inspection. Upon removal of the right elevator we found the midspan hinge was broken. Bob and Jim Patillo have offered to fix in my absence and since I live in Nevada. Problem is none of us can find the LS1 addendum for the Q200. Especially needing the CS17 part to help with the fix. I’ve been on quick heads and Jon finley’ site to no avail. Does anyone have a PDF file you can send me on that topic (maybe Sam that has rebuilt his canard?
Thanks in advance 

Mike Q200.   N200QK.    
pM me please 

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