Narrative:

I was landing on the runway at ZZZ with two other passenger. Upon roll out and approximately half of the way down the runway, my front nosewheel touched the ground. Almost immediately thereafter, I felt vibration in the front nosewheel then heard and felt something pop in the front of the aircraft. Immediately the aircraft went nose down into the pavement and skidded off the runway to the left. The propeller was destroyed and the left main landing gear folded back and there was some minor surface damage to the undercarriage and wingtips. Fortunately no one was hurt as I estimate we were only traveling around 50 to 60 KTS when the accident took place. Since purchasing the aircraft new, I have replaced 5 front nosewheel forks that all have bent to the left upon landing or taxiing the aircraft. Three of them were bent by me and 2 by a commercial pilot I hired for business trips. I called lancair and asked if this had been a problem with any other lancair iv's and they said no. They requested that I send one of the bent nosewheel forks to them for inspection, which I did, and was told that upon inspection they had no idea how this was happening and that they had no complaints or problems in the past with this part. The last time the nose fork bent I just happened to be in ZZZ1 and was carrying an extra one with me just in case there was a problem. Well the mechanic that replaced the nose fork for me laughed and said he had replaced two other nose forks on another lancair iv. He felt that it was a major design flaw and would eventually get someone killed. Callback conversation with reporter revealed the following information: as a result of the callback the reporter supplied pictures of four of his failed nosewheel forks including the last one which separated from the aircraft as detailed in his report. The reporter's photos show four of the five units which were on his aircraft, all of which bent to a greater or lesser degree at the area at which the manufactured piece is bent at 90 degree angles to position the ends of the forks to hold the nosewheel axle. Reporter also stated, in an attempt to resolve the problem prior to the incident, he sought the services of a machining company to provide an after-market version of the fork with improved metallurgy. Per a letter supplied to ASRS by the reporter, this company refused to do so based on their evaluation of the inadequacy of the engineering of the original. From their report the reporter understood the original part had been machined flat from cast aluminum and then bent to its 'U' shape. This process could result in reduced tensile strength in the area of the bend. It was their belief that a stronger replacement part would simply transfer the loads to the attachment point to the nose gear strut which they felt would be inadequate to carry the stresses. The author of the letter, in fact, stated he had predicted exactly the type of failure which ultimately occurred. A second callback elicited more interesting facts. A maintenance inspection of the aircraft showed that the engine mount, to which the nosegear is mounted, had been installed out of plumb. The two topmost attach points being 7/16 inch out of alignment. This would result in the nose gear strut axis being off vertical to a greater or lesser degree depending on the spacing of these attach points. The net result was that every impact on the nose gear strut would be applied at an angle rather than the perpendicular as designed. The repeated side loads thus generated are likely the reason for the multiple failures. He stated that a representative of the lancair company has inspected his aircraft and was the source of his awareness of the motor mount misalignment. The reporter stated this factory rep disclaimed any responsibility for that portion of the assembly 'process' thereby implying responsibility for doing so would fall on one of the subsequent assemblers. Letter from machining company: this letter is offered as a professional opinion from xyz machining concerning the design and fabrication of the nosewheel yoke assembly you shipped to our facility in october 2004. As you know in october you requested our organization to evaluate the apparent metal fatigue you repeatedly have experienced with multiple nosewheel yokes from your lancair aircraft, and if possible, remake the yoke from a stronger, alternate material. As you know, upon completing our evaluation of the component in question, xyz machining declined the opportunity to fabricate a replacement from a material type different than offered by the original equipment manufacturer. The reason we declined was due to our concern that a different material type would induce unreasonable stress to the upper portion of the nosewheel assembly where the yoke is attached. As you also recall, at the time xyz machining predicted that if the existing design was not soon rectified to eliminate the twisting and fatigue occuring to the nose yoke assembly, allowing the nose wheel tire to rub on the interior side of the twisted yoke, that it may eventually lead to breaking off the aircraft completely and dropping the aircraft's propeller onto the landing surface. After speaking to you last week, we understand that unfortunately our prediction was accurate. In conclusion, it is the opinion of our company that the nosewheel yoke assembly discussed is inadequately designed for the loads required of the aircraft.

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Original NASA ASRS Text

Title: OWNER/PLT OF A LANCAIR IV RPTS THAT THE NOSEWHEEL FORK FAILED ON LNDG AT ZZZ RESULTING IN L MAIN GEAR COLLAPSE AND DIVERSION OF THE ACFT OFF THE PAVED SURFACE. RPTR ADVISES THE FAILURE OF THE FORK WAS THE FIFTH FAILURE OF SUCH UNITS ON HIS ACFT IN THE SIX MONTHS SINCE NEW.

Narrative: I WAS LNDG ON THE RWY AT ZZZ WITH TWO OTHER PAX. UPON ROLL OUT AND APPROX HALF OF THE WAY DOWN THE RWY, MY FRONT NOSEWHEEL TOUCHED THE GROUND. ALMOST IMMEDIATELY THEREAFTER, I FELT VIBRATION IN THE FRONT NOSEWHEEL THEN HEARD AND FELT SOMETHING POP IN THE FRONT OF THE ACFT. IMMEDIATELY THE ACFT WENT NOSE DOWN INTO THE PAVEMENT AND SKIDDED OFF THE RWY TO THE L. THE PROP WAS DESTROYED AND THE LEFT MAIN LNDG GEAR FOLDED BACK AND THERE WAS SOME MINOR SURFACE DAMAGE TO THE UNDERCARRIAGE AND WINGTIPS. FORTUNATELY NO ONE WAS HURT AS I ESTIMATE WE WERE ONLY TRAVELING AROUND 50 TO 60 KTS WHEN THE ACCIDENT TOOK PLACE. SINCE PURCHASING THE ACFT NEW, I HAVE REPLACED 5 FRONT NOSEWHEEL FORKS THAT ALL HAVE BENT TO THE L UPON LNDG OR TAXIING THE ACFT. THREE OF THEM WERE BENT BY ME AND 2 BY A COMMERCIAL PLT I HIRED FOR BUSINESS TRIPS. I CALLED LANCAIR AND ASKED IF THIS HAD BEEN A PROB WITH ANY OTHER LANCAIR IV'S AND THEY SAID NO. THEY REQUESTED THAT I SEND ONE OF THE BENT NOSEWHEEL FORKS TO THEM FOR INSPECTION, WHICH I DID, AND WAS TOLD THAT UPON INSPECTION THEY HAD NO IDEA HOW THIS WAS HAPPENING AND THAT THEY HAD NO COMPLAINTS OR PROBS IN THE PAST WITH THIS PART. THE LAST TIME THE NOSE FORK BENT I JUST HAPPENED TO BE IN ZZZ1 AND WAS CARRYING AN EXTRA ONE WITH ME JUST IN CASE THERE WAS A PROB. WELL THE MECHANIC THAT REPLACED THE NOSE FORK FOR ME LAUGHED AND SAID HE HAD REPLACED TWO OTHER NOSE FORKS ON ANOTHER LANCAIR IV. HE FELT THAT IT WAS A MAJOR DESIGN FLAW AND WOULD EVENTUALLY GET SOMEONE KILLED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AS A RESULT OF THE CALLBACK THE RPTR SUPPLIED PICTURES OF FOUR OF HIS FAILED NOSEWHEEL FORKS INCLUDING THE LAST ONE WHICH SEPARATED FROM THE ACFT AS DETAILED IN HIS RPT. THE RPTR'S PHOTOS SHOW FOUR OF THE FIVE UNITS WHICH WERE ON HIS ACFT, ALL OF WHICH BENT TO A GREATER OR LESSER DEGREE AT THE AREA AT WHICH THE MANUFACTURED PIECE IS BENT AT 90 DEGREE ANGLES TO POSITION THE ENDS OF THE FORKS TO HOLD THE NOSEWHEEL AXLE. RPTR ALSO STATED, IN AN ATTEMPT TO RESOLVE THE PROB PRIOR TO THE INCIDENT, HE SOUGHT THE SERVICES OF A MACHINING COMPANY TO PROVIDE AN AFTER-MARKET VERSION OF THE FORK WITH IMPROVED METALLURGY. PER A LETTER SUPPLIED TO ASRS BY THE RPTR, THIS COMPANY REFUSED TO DO SO BASED ON THEIR EVALUATION OF THE INADEQUACY OF THE ENGINEERING OF THE ORIGINAL. FROM THEIR RPT THE RPTR UNDERSTOOD THE ORIGINAL PART HAD BEEN MACHINED FLAT FROM CAST ALUMINUM AND THEN BENT TO ITS 'U' SHAPE. THIS PROCESS COULD RESULT IN REDUCED TENSILE STRENGTH IN THE AREA OF THE BEND. IT WAS THEIR BELIEF THAT A STRONGER REPLACEMENT PART WOULD SIMPLY TRANSFER THE LOADS TO THE ATTACHMENT POINT TO THE NOSE GEAR STRUT WHICH THEY FELT WOULD BE INADEQUATE TO CARRY THE STRESSES. THE AUTHOR OF THE LETTER, IN FACT, STATED HE HAD PREDICTED EXACTLY THE TYPE OF FAILURE WHICH ULTIMATELY OCCURRED. A SECOND CALLBACK ELICITED MORE INTERESTING FACTS. A MAINT INSPECTION OF THE ACFT SHOWED THAT THE ENG MOUNT, TO WHICH THE NOSEGEAR IS MOUNTED, HAD BEEN INSTALLED OUT OF PLUMB. THE TWO TOPMOST ATTACH POINTS BEING 7/16 INCH OUT OF ALIGNMENT. THIS WOULD RESULT IN THE NOSE GEAR STRUT AXIS BEING OFF VERTICAL TO A GREATER OR LESSER DEGREE DEPENDING ON THE SPACING OF THESE ATTACH POINTS. THE NET RESULT WAS THAT EVERY IMPACT ON THE NOSE GEAR STRUT WOULD BE APPLIED AT AN ANGLE RATHER THAN THE PERPENDICULAR AS DESIGNED. THE REPEATED SIDE LOADS THUS GENERATED ARE LIKELY THE REASON FOR THE MULTIPLE FAILURES. HE STATED THAT A REPRESENTATIVE OF THE LANCAIR COMPANY HAS INSPECTED HIS ACFT AND WAS THE SOURCE OF HIS AWARENESS OF THE MOTOR MOUNT MISALIGNMENT. THE RPTR STATED THIS FACTORY REP DISCLAIMED ANY RESPONSIBILITY FOR THAT PORTION OF THE ASSEMBLY 'PROCESS' THEREBY IMPLYING RESPONSIBILITY FOR DOING SO WOULD FALL ON ONE OF THE SUBSEQUENT ASSEMBLERS. LETTER FROM MACHINING COMPANY: THIS LETTER IS OFFERED AS A PROFESSIONAL OPINION FROM XYZ MACHINING CONCERNING THE DESIGN AND FABRICATION OF THE NOSEWHEEL YOKE ASSEMBLY YOU SHIPPED TO OUR FACILITY IN OCTOBER 2004. AS YOU KNOW IN OCTOBER YOU REQUESTED OUR ORGANIZATION TO EVALUATE THE APPARENT METAL FATIGUE YOU REPEATEDLY HAVE EXPERIENCED WITH MULTIPLE NOSEWHEEL YOKES FROM YOUR LANCAIR ACFT, AND IF POSSIBLE, REMAKE THE YOKE FROM A STRONGER, ALTERNATE MATERIAL. AS YOU KNOW, UPON COMPLETING OUR EVALUATION OF THE COMPONENT IN QUESTION, XYZ MACHINING DECLINED THE OPPORTUNITY TO FABRICATE A REPLACEMENT FROM A MATERIAL TYPE DIFFERENT THAN OFFERED BY THE ORIGINAL EQUIPMENT MANUFACTURER. THE REASON WE DECLINED WAS DUE TO OUR CONCERN THAT A DIFFERENT MATERIAL TYPE WOULD INDUCE UNREASONABLE STRESS TO THE UPPER PORTION OF THE NOSEWHEEL ASSEMBLY WHERE THE YOKE IS ATTACHED. AS YOU ALSO RECALL, AT THE TIME XYZ MACHINING PREDICTED THAT IF THE EXISTING DESIGN WAS NOT SOON RECTIFIED TO ELIMINATE THE TWISTING AND FATIGUE OCCURING TO THE NOSE YOKE ASSEMBLY, ALLOWING THE NOSE WHEEL TIRE TO RUB ON THE INTERIOR SIDE OF THE TWISTED YOKE, THAT IT MAY EVENTUALLY LEAD TO BREAKING OFF THE ACFT COMPLETELY AND DROPPING THE ACFT'S PROPELLER ONTO THE LNDG SURFACE. AFTER SPEAKING TO YOU LAST WEEK, WE UNDERSTAND THAT UNFORTUNATELY OUR PREDICTION WAS ACCURATE. IN CONCLUSION, IT IS THE OPINION OF OUR COMPANY THAT THE NOSEWHEEL YOKE ASSEMBLY DISCUSSED IS INADEQUATELY DESIGNED FOR THE LOADS REQUIRED OF THE ACFT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.