N218YV

HISTORY OF FLIGHT

On May 17, 2011, approximately 0645 mountain daylight time, N218YV, a Beech BE-1900D, sustained minor damage when the left main landing gear (LMLG) collapsed during landing roll out on Runway 35L at Denver International Airport (DEN), Denver, Colorado. The airline transport pilot rated captain, commercial rated first officer and the nine passengers were not injured. The airplane was registered to Raytheon Aircraft Credit Corporation, Wichita, Kansas, and operated by Great Lakes Aviation, Cheyenne, Wyoming. An instrument flight rules flight plan was filed for flight 5150 that originated at Pueblo Memorial Airport (PUB), Pueblo, Colorado, about 0607, destined for DEN. Visual meteorological conditions prevailed for the scheduled passenger flight conducted under 14 Code of Federal Regulations Part 121.

According to the captain, while on approach to DEN, the first officer (pilot flying) called for the landing gear to be extended. The captain placed the gear handle in the down position and waited for all three landing gear down-and-locked annunciator lights to illuminate green. However, only the “NOSE”, “RH”, and “L” illuminated. The "H" light for the left gear did not illuminate (there are two bulbs per annunciator, one for the "NO", "SE", "L", "R", and both "H's"). Due to the redundancy built into the annunciator lights, the Captain was confident that even though the “H” light was not illuminated; the fact that the “L” was, indicated that the gear was down and locked. He also noted that the landing gear in-transit light stayed on and the gear motor continued to run for approximately 16 seconds before the gear-motor relay circuit breaker popped. The captain said he confirmed several times that at least one light was illuminated on all three landing gear down-and-locked annunciator lights prior to landing and stated, "All training tells us that indication is 3 down and locked gear."

Just before touchdown, the gear unsafe warning horn sounded. The captain said he was not concerned about the horn and elected not to go-around and run the Quick Reference Handbook (QRH) checklists, since all three landing gear down annunciators were illuminated. Plus, he had previously looked out the window and saw what appeared to be a down and locked gear. Upon landing, and after a few seconds during the rollout, the airplane began to "wobble" and the left main gear collapsed.

The airplane came to rest on the left side of the runway and all nine passengers exited from the left main door. There was no fuel spill or fire.

PERSONNEL INFORMATION

The captain held an airline transport pilot rating for airplane multi-engine land. His last Federal Aviation Administration (FAA) first class medical was issued on August 24, 2010. At the time of the incident, the captain reported a total of approximately 3,250 total hours; of which, 2,800 hours were in a Beech 1900D.

The first officer held a commercial pilot certificate for airplane single and multi-engine land, and instrument airplane. His last FAA first class medical was issued on February 3, 2011. At the time of the incident, the first officer reported a total of approximately 950 total hours; of which, 85 hours were in a Beech 1900D.

AIRCRAFT INFORMATION

The Beech BE-1900D is equipped with a retractable tricycle landing gear system. Extension and retraction of the NLG and both main landing gear (MLG) is accomplished by the action of individual hydraulic actuators installed on each landing gear assembly. The MLG actuators retract for gear extension and extend for gear retraction while the NLG actuator extends for gear extension and retracts for gear retraction. Hydraulic pressure for the system is supplied by a hydraulic power pack located in the left wing leading edge inboard of the nacelle and associated plumbing for the normal extend, normal retract, and emergency extend modes. Control of the system is accomplished through the landing gear handle located to the left side of the center pedestal on the pilot’s inboard sub panel. The landing gear handle has two detents, UP and DN. When the handle is placed in the UP position, power is supplied to the hydraulic pump motor and to a gear-up solenoid that allows fluid to flow through the normal retract side of the system. When the handle is placed in the DN position, power is supplied to the hydraulic pump motor and to a gear-down solenoid that allows the fluid to flow through the normal extend side of the system. Once the landing gears are fully extended, an internal mechanical lock in each of the actuators holds the landing gear in the down position. The lock will also activate a down-position switch in each actuator that will interrupt current to the hydraulic pump motor once all three landing gears are in the down and locked position. In the event that all three landing gears are not down and locked, the hydraulic pump motor will continue to run for about 14 seconds before the LANDING GEAR RELAY circuit breaker pops and interrupts current to the pump motor. In the event of a system malfunction or failure, the pilots can extend the landing gear manually through the use of a hand pump located in the cockpit. The manual extension system utilizes a different reservoir and plumbing than the normal system. Visual indication of the landing gear positions is provided by two red lights located in the landing gear handle and six green lights (two bulbs for each annunciator) located next to the landing gear handle. Illumination of the red lights in the handle occurs when the landing gear are in-transit and illumination of the green lights occurs when the gear are in a down and locked position. A gear-up indication occurs when none of the lights are illuminated. In addition to the down-position switches internal to the actuators, there are two position switches located in each wheel well to provide either an up-position or a down-position indication. In order to get either a gear-up or gear down and locked indication two of the three switches have to be in the correct position. When the down-position switch in the wheel well and the down-position switch in the actuator are both closed, current is supplied to the two green down and locked lights in the landing gear position annunciator assembly corresponding to the appropriate landing gear (NOSE, RH, or LH). When the down-position switch in the wheel well is open and the up-position switch in the wheel well is closed, no current is supplied to any lights. For any other combination of switch positions, current is supplied to the two red in-transit lights in the gear handle. Based on the wiring, there are no combinations of switch positions that can supply current to both the in-transit and down and locked lights simultaneously. Each individual landing gear indication and the in-transit indication have two bulbs installed in a parallel circuit for redundancy. If one bulb should burn out, the pilot will still see the correct indication.

According to the Model 1900D Illustrated Parts Catalog, Chapter 31-10-00-03, the landing gear position annunciator assembly is composed of three different lamp modules; P/N 90-42292-001 for the NOSE indication, P/N 90-42292-002 for the L and R indications, and P/N 90-42292-003 for the H and H indications. The lamp module part number is stamped on the top of each module by the manufacturer. According to Hawker Beechcraft, the lamp modules are sold complete and there are no provisions in their manuals for replacing or changing the face plates. The individual light bulbs can be changed from the rear of the module without removing the face plate. In addition, a small wall, also called a light dam, is placed between each annunciator bulb to keep individual light bulb illumination concentrated on a specific annunciator.

The operator performed an examination of the incident airplane landing gear position annunciator assembly. A lamp module marked with P/N 90-42292-001 and with an L and R face plate was installed in the center position. However, there was no light dam installed in the lamp module assembly. This meant that the light from the illuminated "R" bulb would have bled over and given the appearance that the "L" annunciator was also illuminated. A search of the maintenance records for the incident airplane in ATA chapters 31 Indicating, 32 Landing Gear, and 33 Lights revealed only two individual light bulb replacements since the airplane had been in operation with Great Lakes Airlines. An additional search of the maintenance records was also performed using the annunciator assembly and lamp module part numbers and nothing was found. The operator then examined their remaining fleet and found 15 of 31 airplanes had discrepant annunciators. This included part numbers being inconsistent with the physical part, missing light dams between the bulbs, or incorrect face plates. All of the discrepant parts were replaced with the correct parts.

Great Lakes maintained the airplane under an FAA approved continuous inspection program, which consisted of routine inspections performed every 60 hours and detailed inspections performed every 220 hours. There are six detailed inspections performed in sequence to ensure that the entire airplane is inspected every 1,320 hours.

The incident airplane was leased by Great Lakes Airlines from Raytheon Aircraft Credit Corporation on December 30, 2008. The most recent routine inspection was performed on May 11, 2011, at a total aircraft time (TAT) of 29,562.5 hours and total aircraft cycles (TAC) of 40,314. Item 21 of the routine inspection calls for a check of the main and nose landing gear struts for leaks and was signed off. There were no non-routine work cards for the landing gear generated as a result of this inspection.

The fifth detailed inspection included provisions to inspect the main and nose landing gears on the airplane as well as performing a detailed lubrication of the landing gear components. Step 6 ...