MIAMI, FL, USA
N194GA
Beech 1900C
After takeoff, both main gears remained down and locked; the nose gear was in-transit. Attempts to lock the nose gear were unsuccessful; the nose gear collapsed during the landing roll. The emergency hand pump was unable to build pressure in secondary system due to leakage past the shuttle valve and the shuttle bore in the end cap of the left gear actuator; excessive clearance was noted. The shuttle valve or bore were not worn or damaged. During manufacturing, the shuttle bore and shuttle valve are honed and lapped to fit and kept as matching parts; clearance limits are not specified. Functional testing detects excessive clearance. Overhaul procedures do not require honing of the shuttle bore. The power pack motor was inoperative with a "load" applied. The left actuator was overhauled August 1998; during overhaul the shuttle and end cap were not replaced. The overhauled actuator was installed February 2000. Emergency extension and rigging checks required by the airline job card and maintenance manual respectively were not performed following actuator installation. Emergency extension check was accomplished last approximately 4 months earlier; the maintenance manual does not indicate application of force to the tires during extension check using the emergency hand pump. The airplane had accumulated approximately 1,475 hours and 1,746 cycles since actuator installation and 18,302 hours and 23,315 cycles since power pack assembly installation.
On September 16, 2000, about 1925 eastern daylight time, a Beech 1900C, N194GA, registered to Raytheon Aircraft Credit Corporation, operated by Gulfstream International Airlines as flight 9416, dba Continental Connection, experienced collapse of the nose landing gear on landing at the Miami International Airport, Miami, Florida. Visual meteorological conditions prevailed at the time and an instrument flight rules (IFR) flight plan was filed for the 14 CFR Part 121, scheduled, international, passenger flight. The airplane sustained minor damage and there were no injuries to the airline transport rated captain, the first officer, or to the 10 passengers. The flight originated about 1725, from the Freeport International Airport, Freeport, Bahamas. The captain and first officer stated that after placing the landing gear selector handle to the up position, both main landing gears remained down and locked and the in transit lights in the gear handle were illuminated; there was no down and locked indication from the nose landing gear. The landing gear handle was cycled several times with negative results. Additionally, the abnormal landing gear manual extension checklist was run also with negative results. Positive "G" loading maneuvers were unsuccessful in extending the nose landing gear to the down and locked position. It was noted that the "hydraulic fluid low" annunciator light illuminated when the landing gear circuit breaker was pushed in. The airline dispatcher and maintenance control were notified to obtain advise on how to extend the nose landing gear. Two low approaches past the Miami Air Traffic Control (ATC) tower and activation of the gear warning horn with power reduction confirmed that the nose landing gear was not fully extended. An emergency was declared with ATC and the flight returned for landing. After touchdown, the propellers were feathered; the nose landing gear collapsed after touchdown on the runway. Examination of the airplane by the FAA while on the runway revealed minor damage. During recovery of the airplane, the right main landing gear collapsed resulting in structural damage. The airplane was recovered and placed in a hangar on jacks for further examination. Examination of the hydraulic system of the airplane revealed that the hydraulic power pack motor was inoperative. External visual examination of the power pack motor revealed arching damage to the forward side of the cover can in an area behind one of the electrical cables; no evidence of chafing or arching on the electrical cable insulation was noted. Attempts to extend the landing gear using the emergency hand pump revealed all landing gears could be extended but resistance against them prevented them from locking into position. The left main landing gear actuator was isolated from the system and the nose and right main landing gears extended and locked into position which resistance could not prevent. No fluid leakage was noted from the left main landing gear actuator. The power pack motor and the left main landing gear actuator were retained for further examination. Examination of the power pack motor with FAA oversight revealed that the ceramic insulator for the positive terminal stud was broken and an internal stand-off on the cover can was missing due to what appeared to be electrical arching. The stand-off is responsible for the negative electrical connections from the negative brush holders to the motor frame. The motor operated under a "no-load" condition but did not operate when a load was applied in accordance with the acceptance test procedure. Disassembly of the motor revealed that commutator, brush shunts and brush holders were in good condition with no signs of overheating. No determination was made as to the reason for the high heat connection at the stand-off which exhibited arching. The power pack motor was manufactured on September 16, 1988, and installed in the power pack assembly that was installed in the airplane on October 11, 1991. The airplane had been operated for approximately 18,302 hours and 23,315 cycles since installation of the power pack assembly at the time of the failure. A report from the power pack motor manufacturer is an attachment to this report. Examination of the left main landing gear actuator with FAA oversight and a representative of the airplane manufacturer present revealed that it operated with no discrepancies noted during testing of the primary retract port (retraction of the actuator equates to gear extension). Testing of the shuttle valve by applying hydraulic pressure to the secondary retract port resulted in excessive leakage from the uncapped primary retract port; the full test pressure could not be reached due to the excessive leakage. The report from the actuator manufacturer indicates that when hydraulic pressure was applied to the secondary retract port, the actuator which was fully extended, retracted and locked. By design, the secondary retract port is utilized when performing emergency gear extension using the hand pump. Disassembly of the actuator revealed a discrepancy with the backup ring on the piston head. There was no evidence of excessive wear or damage to any of the parts including the end cap and shuttle. The shuttle measured .377 inch; the finished part size is specified to be .3770 inch. The shuttle bore in the end cap of the actuator measured .381 inch; resulting in a clearance of .004 inch between the shuttle and shuttle bore in the end cap. The shuttle bore by detail drawing is .3760 inch +.0003 inch -.0000 inch. According to the manufacturing facility which also overhauls the actuators, during manufacture, the end cap is required to be honed and lapped with the shuttle and kept as matching parts. There is no specified bore diameter or maximum clearance between the shuttle and the shuttle bore after honing and lapping during manufacturing, the proper clearance between the shuttle and shuttle bore in the end cap is verified during functional testing. The overhaul procedures of the actuator do not require honing of the bore in the end cap. A report from the landing gear actuator manufacturer is an attachment to this report. The left main landing gear actuator installed at the time of the incident was overhauled in August 1998, and installed in the airplane on February 1, 2000. It was installed to replace the actuator that was previously removed for another company airplane. The overhaul paperwork indicates that only a seal kit and poppet fitting were replaced; the shuttle valve and end cap were not replaced at the overhaul. The paperwork indicates that the shuttle valve leakage was tested at 1,500 psi and no leakage was noted. The airplane had been operated for approximately 1,475 hours and 1,746 cycles since installation of the actuator. Following installation of the left main landing gear actuator in the incident airplane, the FAA approved task card titled "Landing Gear Retraction" utilized by the airline, indicated that the emergency extension system was required to be checked but was not accomplished with the letters "N/A" in the mechanic block. A note at the bottom of the job card reads, "N/A = ops check new actuator only-not landing gear inspection (C-5) with an illegible word beneath 'C-5'". The task card also indicated that quality control inspection of three actuators for noise, binding, and proper rigging was not required. The maintenance manual indicates that, "...if the actuator being installed is not the one that was removed, rig the landing gear." The manual also indicates that the landing gear should not be cycled electrically until the landing gear is properly rigged and to raise and lower the gear during the rigging procedure with the emergency hand pump. Check of the emergency gear extension was reportedly complied with on May 7, 2000, in accordance with task card 32-00-01. The maintenance manual does not indicate to apply a forced against the extending landing gear to simulate airloads during the extension check using the emergency hand pump. An additional party to the investigation was Mr. Paul DeVore of the FAA, Aircraft Certification Office located in Wichita, KS. The airplane minus the retained power pack motor and the left main landing gear actuator was released to Oscar Barrabi, a supervisor of Gulfstream International Airlines, on September 20, 2000. The retained components were released to Mr. Wayne Modny, Director of Quality Control, Gulfstream International Airlines, on December 29, 2000.
The excessive clearance between the shuttle valve and the shuttle bore in the end cap of the left main landing gear actuator for undetermined reasons either during overhaul or manufacturing resulting in failure to build hydraulic pressure using the emergency hand pump. A finding in the investigation was the failure of the airplane manufacturer to identify procedures in the maintenance manual that would detect the above listed condition during check of the emergency hand pump.
Source: NTSB Aviation Accident Database
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