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Eddy's crash investigation results
After much investigating and head scratching between several smart individuals we have arrived at a theory we think best represents what possibly happened with the Mad Mosquito that caused it to crash. Please understand that we are not closing the door to further investigation as we move forward and reflect on what we have learned so far. The point has come where we feel comfortable enough with the theory and are ready to reveal it to the community. I don’t want to appear as though I am throwing my late father under the bus but the theory reveals that a modification he made is what started the catastrophic failure. I know in my aching heart that he would want this information to be revealed to educate and protect the people in the community who, as you all know, he loved very much. This has not been an easy process for me or the other people involved but we have tried to be objective and meticulous in the spirit of how my father would have handled this investigation. He was a great man and we owe it to him and ourselves to arrive at some point of closure. Please also understand that with this crash (like most others) we will probably never be 100% sure of what actually happened. I would like to thank Dwight Junkin, Lorne Diebel, Ross Quarniccio, Mike Messex, Ladon Moore, John Snider and John Uptigrove for all of their intense help and dedication in regards to helping figure this out. As well I would like to thank all of you for your thoughts, prayers and support for my family. My mother wanted me to let you all know that you made my father a very happy person when he became involved with the Mosquito and Experimental Helicopter communities and that he has never seemed happier than in the last three years of his life because of all of you.

The following explanation covers the theory of catastrophic failure that lead to the crash of the Mad Mosquito XEL and the death of owner operator Eddy Thompson on July 4th 2010. The theory is based on eyewitness accounts, observation of the actual wreckage and pictures taken at the crash scene before any of the wreckage was disturbed. The theory is chronologically revealed in steps numbered 1 through 6. Each step of the theory consists of a scenario and supporting evidence will be cited to illustrate how each step of the theory was decided upon. All data has been sent to a DOT crash investigator who is working on his own theory independent of any input or influence from the Mosquito factory or community regarding this crash theory. The DOT investigator we sent information to has been tasked with investigating another helicopter crash so we do not yet have his input and it may be some time before we receive anything from him.

Step 1.

Scenario: While in a cruise flight profile the left horizontal stab broke off from the tail boom.

Supporting evidence: The horizontal stabs were not mounted hard fixed to the tail boom (as per the designer’s recommendation) but were modified to allow for an adjustable angle of incidence. After viewing under a microscope this modification appears to have weakened the integrity of the aluminum cross tube that holds the stab into the tail boom. The left stab (believed to be the one that failed) shows signs of a clean break around the circumference of the joining tube and correspond with four cross-drilled holes at roughly 90 degrees in relation to each other. The right stab appears to have broken off as a result of secondary damage since the cross tube is bent forward and the break is not clean but rather jagged indicating that it was acted upon before the tube broke. This evidence is supported by the portions of cross tube that were left in the tail boom but do not have the benefit of the mating halves since the stabs have yet to be found. In retrospect the modification methods although crude were not load bearing but clearly could have and probably did contribute to the degradation of the tube causing the point of failure.

Step 2.

Scenario: After breaking off, the left horizontal stab flew up and back and struck the tip of the advancing blade of the tail rotor somewhere near the 12 o’clock position.

Supporting evidence: One of the tail rotor blades has evidence of high velocity damage to the tip with small traces of blue paint residue left in the folds and curls of the broken aluminum. The horizontal stabs were the only items on the helicopter that were painted blue and detachable.

Step 3.

Scenario: A fragment from the left horizontal stab (probably the cross tube) was pelted forward and began to ark to the left due to spin (english) and the relative wind in cruise flight. The horizontal stab fragment met the bottom surface of one of the main rotor blades when that blade was somewhere between the 9 o’clock position and the 6 O’clock position in counter clockwise rotation (retreating blade). When the fragment made contact with the blade it blew a hole in the blade.

Supporting evidence: The hole in the rotor blade has a 1” indentation on the leading edge side and is semicircular in shape. When viewed under a microscope blue paint residue and metal-to-metal scratches can be seen. This indentation also establishes the approach angle of the fragment as it hit the blade and suggests that the fragment slightly favored a root to tip entry/exit path. When the shrapnel extending from the fragment exit point on the topside of the blade is folded back into shape it suggests a matching semicircular half of the indentation left on the leading edge of the hole.

Step 4.

Scenario: The damaged main blade pitched extreme leading edge down.

Supporting evidence: The pitch control horns on each blade are bent but in opposite directions and of different magnitudes. The pitch horn corresponding to the damaged blade is bent upwards at 90 degrees (proving a severe negative angle of incidence/angle of attack was experienced) while the pitch horn corresponding to the undamaged blade is bent down at about 45 degrees.

Step 5.

Scenario: The damaged main blade in an extreme negative angle of attack slowed down due to the drag created and lost centrifugal rigidity causing the blade to flex along it’s entire length with a resulting massive shift of balance toward the opposite blade that was still carrying weight and inertia. The damaged blade made contact with the right front skid and float.

Supporting evidence: Damage to the right front skid and the blade are a shared match and the right float is lacerated about the entire circumference at the same spot where the blade and skid met. The right front skid bow tube is also broken. Eyewitnesses say they heard a loud metal on metal contact and as they saw the helicopter fall out of the sky the deflated float wrapped around the nose, the blades were completely stopped with one of the main rotor blades folded, the tail boom was broken off near the cockpit and there were some parts falling away from the helicopter.

Step 6.

Scenario: The torque inflicted on the fuselage when the blade impinged on the skid caused the forward part of the fuselage to yaw hard left and then the tail boom broke off where it joins the fuselage. The engine and drive train experienced sudden stoppage.

Supporting evidence: Eyewitnesses say the main blades seemed to stop instantaneously, the tail boom broke off, the helicopter folded up and silently fell from the sky. The forward “Love joy” coupling (drive shaft side) broke in half in such a way that the directional signature proves that the tail rotor inertia is what broke it not torque from the engine. The couplers on the tail rotor gearbox are not damaged.
Any damage after Step 6 is secondary damage and is assumed not to be a cause but rather a result of the damage caused by any of the preceding steps.

In closing I would like to add that if anything changes in the theory I will post it here on this thread.

First of all I'd like to thank Mark for how incredible he's been through this this whole tragedy. In spite of the pain of his loss Mark has been deeply involved in investigating the incident. The Mosquito community owes him and his depth of character a debt of gratitude.

Secondly, and all who have seen Eddy's Mad Mosquito at airshows can attest to this, Eddy was meticulous and took the construction, maintenance and safety of his machine very seriously. A lot of thought went into the build. He documented every step. All who knew Eddy knew that owning his Mad Mosquito and being a part of the Mosquito community had been a highlight of his life so he went to great lengths to make sure he did everything well. I believe Eddy would want us to learn from this so we can make sure it doesn't happen again.

So to that end I'm asking and stressing that if anyone has ideas for modifications, small or big, PLEASE pass them through myself or Dwight first. Dwight and I will consult and involve others if required to be sure we examine all the potential ramifications of the mod. While of course we don't claim to know all we are closest to the design and have a more intimate understanding the function of the machine and so will have insight that others may not. A second and third set of minds on any proposed change will only help to ensure that the change is sound. And if the mod is beneficial it can perhaps become a change to the Mosquito to improve it over all.

And to ensure that do all we can to maximize the safety of the Mosquito we will be issuing an AD to further reinforce the horizontal stabilizer even in the factory form. To those with horizontal stabs be watching for this shortly in the AD section of the builders forum.
Mark, I'd like to commend you and your team for having the presence of mind to conduct this investigation, considering the tremendous loss to you, and the Mosquito community.
I believe that you have worked up a very reasonable theory of the accident. As everyone knows, an accident usually starts with one small issue, and then works into something on a more catastropic level. Your sceneros support this completely.
I personally feel a sense of relief now knowing what may have caused the accident. I think we will all continue to enjoy our Mosquitos, but we must not let our guards down, no matter what we're flying.
Thanks Mark.
Merci pour cette analyse.
Thank you for this analysis.
Jean-Rémy (XE 1077 - Sud Bretagne - France)
Eddy would be proud Mark. Thanks for everything you've done along with others. We're all here for you.
ower thoughts and prayers to eddy, his family and all fellow aviators who have gone west.

Mark I really look up to you man, and most of it has nothing to do with helicopters. I don't know how I would handle what you and your family have been through, and you totally took charge in this situation. Not only have you honored your father who we all loved, but you have honored all of us in doing this right, I comend and thankyou for it. If anyone does not have any idea of what sacrifice and putting the needs of others before them selves looks like, you have just witnessed it. Mark thankyou for all you have done for all of us...........
My thoughts exactly Rob. I'm really thankful for the brotherhood we all share. Mark, we all love you man!

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