Accident Overview
On December 19, 2011, at 1100 Eastern Standard Time, a Piper PA-44-180, registration N790GK, operated by Airline Transport Professionals (ATP) sustained substantial damage when the right main landing gear collapsed during the landing roll at Gwinnett County Airport (LZU), Lawrenceville, Georgia. The flight instructor and a pilot-rated student were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the instructional flight conducted under 14 CFR Part 91. The flight originated from DeKalb-Peachtree Airport (PDK), Atlanta, Georgia, earlier that day at about 1000.
Pre-Landing Gear Issues
While configuring the airplane for a power-off stall, the pilots observed an unsafe gear indication after selecting the landing gear down position. Two green lights were illuminated, but the right main landing gear indicator light was off. The flight instructor recycled the landing gear, but the right main indicator light remained off. The instructor then replaced the indicator light bulbs, but the light still did not illuminate. The gear was cycled five more times without success. Following the emergency landing gear extension procedures from the pilot’s operating handbook (POH) also failed to illuminate the right main gear light.
Landing and Collapse
The pilots notified an air traffic controller of the condition. The controller observed the airplane during a low approach and advised that the gear appeared down. The flight instructor entered the traffic pattern and landed on runway 07. During the landing roll, all three main landing gear were extended, but as the airplane slowed, the right main landing gear collapsed. The airplane veered off the runway and struck a runway light, resulting in damage to the right engine’s propeller, right wing outboard leading edge, right flap, and right aileron.
Aircraft and Maintenance History
The airplane was manufactured in 1979 and powered by two Lycoming O-360 series, 180-horsepower engines. Its most recent 100-hour inspection was completed on November 16, 2011, at which time the aircraft had 9781.3 total hours and 7073.6 hobbs hours. The accident occurred about 38 hours after that inspection.
Postaccident Examination
Examination of the right main landing gear revealed that the truss assembly hook did not travel over the truss pin. Federal Aviation Administration inspectors tested the landing gear, and the right main gear did not lock on any attempt. Excessive friction was found between the truss bracket and stud, preventing the side brace from fully rotating and thereby preventing the truss hook from traveling over the lock pin. The right main landing gear truss bracket pin had little or no grease, while the left main gear pin had grease indications around the pin and zerk fitting.
Maintenance Records
Airframe maintenance records showed that a new bushing was installed in the right main landing gear side brace mount assembly on November 16, 2011. The mechanic who performed the work stated he could not find guidance in the maintenance manual for removing and installing the new bushing; he replaced it, verified movement between parts, and reinstalled the side brace assembly. The same maintenance entry noted that he greased the landing gear and performed a retraction, extension, and free-fall test without defects.
Maintenance Manual Procedures
The Piper Aircraft PA-44-180/180T Airplane Maintenance Manual (Page 32-15) outlines the installation procedure for the main landing gear side brace link assembly:
- A. Position link support bracket with swivel stud installed at its attachment point on the web of the spar and secure with bolts and washers.
- B. Ascertain that the upper and lower links are assembled with downlock hook, retraction fitting, etc., attached, and check through travel of the links and downlock hook clearance.
- C. Attach the upper link to the swivel stud of the support fitting and secure with bolt, bushing, washer, nut, and cotter pin.
- D. The actuating cylinder rod end bearing and lower side brace link may be attached respectively to the retraction fitting and strut housing during gear adjustment.
Additionally, the manual states: "When assembling components of the landing gear, lubricate bearings, bushings, and friction surfaces with proper lubricant as described in Chapter 12."