Accident Sequence
On June 17, 2014, about 1205 eastern daylight time, a Schweizer 269C-1, registration N152CC, operated by Ace Pilot Training, Inc., was substantially damaged during landing at Lehigh Valley International Airport (ABE), Allentown, Pennsylvania. The student pilot, who was conducting a local solo instructional flight under 14 CFR Part 91, sustained minor injuries.
According to the student pilot, she landed the helicopter after a 40-minute flight and began shutdown procedures. She applied collective friction, started the timer, and ran the engine at 2,500 rpm for cool down. After turning off the boost pump and radios, she retrieved the checklist. While tightening the cyclic friction at the cyclic base, the helicopter developed ground resonance. Unable to get airborne due to the engaged friction, she rolled the throttle to idle. The resonance increased, and "in a matter of seconds, the helicopter shook itself apart." The pilot held on until the movement stopped, then secured the engine and exited.
A photograph showed the tail boom twisted toward the right side at its junction with the main structure.
Examination Findings
Postaccident examination included recovery and testing of the four landing gear dampers at the manufacturer. A Sikorsky representative and FAA inspectors were present. Testing used a load cell and computer to record stroke versus load, identical to production verification.
All four dampers failed the load stroke test and exhibited slight dried hydraulic fluid on pistons and boot interiors. Specific results:
- Left forward (part 269A3150-19, serial S0782): Intact with bending and fracture of the upper bearing lug; low on compression at lower pressure test point; out of limits at ultimate load.
- Right forward (part 269A3150-19, serial S0783): Intact; low on compression lower pressure test point; slightly out of limits at ultimate load (2830 lbs vs 2900-3600).
- Left rear (part 269A3150-21, serial S0742): Intact with minor upper lug bending; low on lower pressure test point; out of limits at ultimate load (2210 lbs vs 3200-3900).
- Right rear (part 269A3150-21, serial 80729): Intact with slight upper lug bend; out of limits at ultimate load (3100 lbs vs 3200-3900).
Maintenance Background
On April 15, 2014, the certificate holder issued Alert Service Bulletin (ASB) B-304 for a one-time load stroke inspection of landing gear dampers at an overhaul or repair facility, effective for all 269C models, with compliance by January 9, 2015. The ASB did not provide background history. Concurrently, a revision to the Handbook of Maintenance Instructions (HMI) added a load stroke inspection procedure.
The 100-hour inspection criteria required inspection of landing gear dampers for operation and condition, and for damper extension with full fuel tank. HMI indicated dampers experience pressure decrease with use and should be extension-checked each 100 hours or every 6 months.
According to the responding FAA inspector, maintenance was outsourced. The helicopter's latest 100-hour inspection occurred on April 24, 2014, with 58 hours operated since. Records dating back to 2011 (about 800 hours) showed no maintenance actions involving the dampers.
The student pilot reported about 40 hours of helicopter flight experience and held an airline transport pilot certificate for airplanes with about 5,465 fixed-wing hours.