Titusville, FL, USA
N700VR
Piper PA-34-220T
According to the pilot, the airplane touched down on the runway on all landing gears, bounced slightly, then touched down on the nose landing gear causing it to collapse. On short final approach when the airplane was approximately 10-15 feet above the runway, the pilot applied nose-up pitch trim to counter the nose-heavy tendency of the airplane but the pitch trim continued to operate in the nose-up direction despite his release of the pitch trim switch. He applied power and forward pressure on the control yoke. Postaccident examination of the electric pitch trim system revealed the rocker switches would intermittently stick in either the nose-up or nose-down position. Testing and disassembly of the pilot's electric pitch trim switch revealed the unit tested satisfactory electrically, but intermittent mechanical sticking in either the nose-up or nose-down direction was noted. Dirt/grime was noted near the rocker switch assembly. Examination of both rocker switches revealed the hole (pivot point) in 1 of the 2 was .001 less than the minimum specification. The pitch trim servo operationally tested satisfactory. Since purchase by the pilot approximately 2 months earlier, he accumulated approximately 20 hours and noted that during the last 2 or 3 flights, or a total of 8 or 9 times, the pitch trim continued in the direction of application when using the pitch trim switch on the pilot's control yoke. He corrected this by moving the control yoke opposite the direction of the travel of the trim, and also by moving the pilot's pitch trim switch opposite the initial application direction. Of the 8 or 9 times, the trim continued in the nose-down direction 6 times, and in the nose-up direction 2 or 3 times. He did not have a mechanic inspect the electric pitch trim system to determine the cause of the trim continuing in the direction of application, and on the day of the accident when the airplane was at an avionics shop to have work performed, he did mention to any personnel the issue related to the pitch trim.
On July 5, 2005, about 1236 eastern daylight time, a Piper PA-34-220T, N700VR, registered to and operated by a private individual, experienced collapse of the nose landing gear while landing at Space Coast Regional Airport (KTIX), Titusville, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight from Vero Beach Municipal Airport, Vero Beach, Florida, to Space Coast Regional Airport. The airplane sustained minor damage and the commercial-rated pilot, the sole occupant was not injured. The flight originated about 1210, from Vero Beach Municipal Airport. The pilot stated that the accident flight was the second flight of the day; the first flight to Vero Beach was uneventful. Prior to departure on the accident flight he performed a preflight inspection of the airplane using the airplane's checklist, which included a test of the autopilot system. The autopilot system tested OK. No discrepancies were noted when he performed an engine run-up before takeoff. After takeoff, he engaged the autopilot but it disconnected several times while changing heading using the heading bug. He continued to his planned destination (KTIX), and contacted the KTIX air traffic control tower when the flight was approximately 10 miles south. The flight was cleared for right base to runway 09, and due to calm wind condition, he elected to land with full flaps. He confirmed having three greens on final and visually verified the nose landing gear was down before touchdown. He maintained 90 to 95 knots until over the threshold, and when the flight was approximately 10 to 15 feet above the runway, he reduced power and applied nose-up pitch trim using the electric pitch trim switch on the pilot's control yoke to help alleviate the nose heavy tendency of the airplane. The pitch trim kept running in the nose-up direction, which he corrected by applying power and forward pressure on the control yoke. The airplane touched down on the runway on all three landing gear, bounced less than 5 feet AGL, and with power applied, then landed on the nose landing gear which collapsed approximately 1 second later. He steered the airplane towards the right side of the runway, and remained in the airplane for a couple minutes to coordinate with the tower before exiting the airplane. The emergency locator transmitter (ELT) did not activate as a result of the accident, and he did not hear the stall warning horn. Examination of runway 09 by a representative of the airplane manufacturer with FAA oversight revealed ground scars on the runway associated with both propellers located approximately 1,500 feet from the approach end of the runway. A second contact location was noted approximately 66 feet from the first runway contact location. Damage to the runway was noted 88 feet from the first runway contact location, and the airplane was noted to come to rest 604 feet from the initial runway contact location. The airplane was recovered for further examination. Examination of the airplane by a representative of the airplane manufacturer with FAA oversight revealed the stabilator trim indicator was at or near the full nose-up indication. The stall warning horn operationally tested satisfactory with the flaps fully extended (same configuration as at the time of the accident). Operational testing of the electric pitch trim system using the switch on the pilot's control yoke revealed the stabilator trim would continue to operate in the nose-down direction, even though the electric pitch trim switch was released. Additionally, the stabilator trim would intermittently continue in the nose-up direction despite release of the electric pitch trim switch. The electric pitch trim switch and pitch trim motor were retained for further examination. The pitch trim servo and electric pitch trim switch were examined at the manufacturer's facility with FAA oversight. Bench testing of the pitch trim servo revealed the unit "...passed the final acceptance tests in accordance with the factory maintenance manual." Visual examination of the electric pitch trim switch revealed "some dirt/grime build-up present near the switch rocker assembly." Manipulation of either of the 2 rocker switches of the switch assembly confirmed intermittent mechanic sticking of one or both rockers in either the trim up or trim down directions. Bench testing of the switch revealed proper electrical operation. Additionally, both rockers had to move to full travel limit to activate the micro-switches and illuminate the respective LED light in the test fixture. The switch was disassembled and the internal diameter (ID) dimensions of each hole located in each of the 2 rocker switches were determined. The ID of the hole in the "thin rocker switch" measured between .066 and .067 inch, and the ID of the hole in the "wide rocker switch" measured .068 to .069 inch (specification for both is .070 + /- .002 inch). The roll pin measured .066 to .069 inch (specification is .066 to .069 inch). The disassembled switch was submitted for further examination to the NTSB Materials Laboratory located in Washington D.C. The examination by NTSB of the disassembled electric pitch trim switch confirmed the average inside diameter of the hole of the "small rocker" was less than specification when measured at both ends, and the average inside diameter of the hole of the "large rocker" measured within limits. No obstruction or foreign matter was observed in either of the holes in the rocker switches. The roll pin which acts as a pivot for each rocker switch was found to be .0005 inch less than specification, and was bent at an angle of approximately 1 degree. A wire spring which acts to return the rocker switch to the neutral position and is installed in a channel at the base of each rocker switch was noted to have worn a groove approximately .005 inch deep in the corners of both rocker switches. Two finite element models were constructed to determine what effect the wear groove had on the amount of "restoring force" and "restoring moment" available to return the rocker switches to neutral; the models did not take into account the result of friction, and did not include the top part of the rocker. The results of the modeling revealed that the "restoring force" to return the rocker switch to neutral is less for a worn rocker switch, when compared with an unworn rocker switch. Additionally, the amount of "restoring moment" is less for a worn rocker switch at low angles of rotation, but the "restoring moment" becomes greater for a worn rocker switch as the angle of rotation increases, that is, a greater amount of "restoring moment" occurs when the rocker switch is moved a greater amount. The rocker switch was reassembled and no sticking of either rocker switch was noted. The pilot further reported that he has operated the airplane approximately 20 hours since purchasing it on May 6, 2005. No discrepancies were noted with the electric pitch trim system prior to his purchase; however, he noted that on the last 2 or 3 flights, or approximately 8 or 9 times, the pitch trim would continue to operate in the direction of application when using the pilot's electric pitch trim switch. His corrective action consisted of applying opposite pressure on the control yoke and by moving the pilot's pitch trim switch in a direction opposite the initial trim application direction. Of the 8 or 9 times this occurred, the trim would continue in the nose-down direction approximately 6 times, and would continue in the nose-up direction approximately 2-3 times. The trim continuing in the direction of application was intermittent since he owned the airplane. He further reported that he did not have any maintenance facility inspect the pitch trim system to determine the reason for the trim continuing in the direction of application despite release of the rocker switches. The airplane was at an avionics shop on the morning of the accident but he did not mention that discrepancy to any personnel of the facility. He was preparing on upgrading the avionics and having an upgrade or inspection of the trim system which ..."would likely have commenced by July 11, 2005." The airplane was manufactured in 1998, and had accumulated 1,501.8 hours total time since new. NTSB and FAA review of the airplane maintenance records from the date of manufacture revealed no entry indicating removal and/or replacement of the pilot's electric pitch trim switch. The airplane minus the retained components were released to the pilot/owner of the airplane on August 11, 2005. The retained components were also released to the pilot/owner on December 12, 2006.
The pilot's continued operation of the airplane with known intermittent deficiencies of the electric pitch trim switch, resulting in a mis-trim condition of the airplane (nose-up), and subsequent hard landing on the nose landing gear causing it to collapse. A factor in the accident was the failure of the electric pitch trim switch to return to the neutral position after being disengaged due to dirt/grime.
Source: NTSB Aviation Accident Database
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