N960SW

1.1 HISTORY OF FLIGHT

On June 12, 2005, about 2226 Pacific daylight time, a Bombardier CL-600-2B19, N960SW, operated by SkyWest Airlines, Inc., as United Express flight 6543, contacted the runway with the nose landing gear partially extended at the Los Angeles International Airport (LAX), Los Angeles, California. The airline transport pilot and first officer, 1 flight attendant, and 14 passengers were not injured; the airplane sustained substantial damage. Instrument meteorological conditions prevailed for the 14 CFR Part 121 scheduled domestic passenger flight that was operating on an instrument flight rules (IFR) flight plan. The flight originated from LAX at 2127, with a planned destination of Santa Barbara Municipal Airport (SBA), Santa Barbara, California.

A review of the SkyWest Airlines Aircraft Flight Log disclosed that the accident flight was scheduled to be the flight crew's fourth trip of the day, corresponding to the airplane's eighth flight. The 31-minute accident flight was scheduled to depart from LAX at 2125, and terminate in SBA at 2156. The accident flight crew indicated that the preflight inspection was normal and that no maintenance discrepancies were noted.

During post accident interviews, the flight crew stated to a National Transportation Safety Board investigator that the takeoff and en route portions of the flight to SBA were normal and uneventful. The captain stated that as the airplane entered the vicinity of the airport, he began the landing checklist and called for the first officer to extend the landing gear to the down and locked position. Upon manipulating the landing gear lever into the down position, both pilots heard the nose landing gear (NLG) doors open almost immediately.

Several seconds after the landing gear lever was selected to the down position, the pilots noted a "gear disagree" warning message displayed on the Engine Indicating and Crew Alerting System (EICAS), accompanied by a simultaneous warning chime. The primary page on the EICAS system displayed that the main landing gear (MLG) were down and locked with green box indications, and the nose gear was showing a red box, indicating that the nose landing gear was not fully extended.

The captain opted to divert back to LAX in consideration that SBA was closing shortly and that LAX has longer runways and more emergency facilities. After receiving a clearance and maneuvering the airplane back toward Los Angeles, the pilots began to troubleshoot the gear indication with use of the airplane's Quick Reference Handbook (QRH). Following the checklist, the first officer pulled the manual release handle located between the pilot's seats, during which time the gear indication remained unchanged.

With the EICAS continuing to display the unsafe gear indication, and the airplane approaching LAX, the captain declared an emergency. The airplane touched down on runway 25L, making initial contact with the MLG. The airplane continued to roll on the MLG, and as the ground speed dissipated the nose lowered. The nose contacted the runway surface and the airplane slid to a stop. All the crew and passengers egressed the airplane through the main cabin door without further incident.

According to a SkyWest Airlines maintenance manager who responded to the accident, the airplane came to rest on the nose landing gear doors; the NLG uplock pin was released from the uplock assembly. The nose of the aircraft was lifted from the runway surface with air bags. As the nose was raised from the runway, the NLG extended freely from the wheel well, and continued to the down and locked position without any outside force (hydraulic or manual). The nose tires continually remained in contact with the runway surface while being recovered. The aircraft was then towed to the United Airlines ramp area.

1.2 PERSONNEL INFORMATION

1.2.1 Captain

The captain was hired by SkyWest Airlines on March 23, 1996. A review of information on file with the Federal Aviation Administration (FAA) Airman's Certification Division, Oklahoma City, Oklahoma, revealed that the captain was issued an airline transport pilot certificate on December 22, 1996, with ratings for airplane single engine land, multiengine land and instrument airplane. The captain additionally held an airplane and powerplant mechanic certificate. He was last issued a first-class medical certificate on January 17, 2005, with the limitation that he must wear corrective lenses while exercising the privileges of his airman certificate.

The captain received a type rating for the CL-65 on August 4, 2001. SkyWest Airlines records indicated that the captain had accumulated 11,728 hours total flight experience. He had amassed 4,636 hours in the CL-65 series airplane, of which 3,229 hours he was pilot-in-command (PIC). He had flown about 189, 55, and 5 hours in the 90 days, 30 days, and 24 hours, respectively, before the accident. The captain's last CL-65 proficiency check was marked as completed on March 12, 2005; his last competency check and route check marked as completed on September 06, 2004; and his last simulator check marked as completed on September 15, 2004.

1.2.2 First Officer

The first officer was hired by SkyWest Airlines on December 2, 2002. According to the FAA, he held a commercial pilot certificate with ratings for airplane single engine land, multiengine land and instrument airplane. He held a first-class medical certificate that was issued on October 14, 2004, without limitation.

SkyWest Airlines records indicated that the first officer had accumulated 3,145 hours total flight experience. He had amassed 1,768 hours in the CL-65 series airplane and had flown about 245, 72, and 5 hours in the 90 days, 30 days, and 24 hours, respectively. The first officer's last CL-65 proficiency check was marked as completed on May 20, 2004; his last competency and simulator check was marked as completed on May 13, 2005; and his last route check was marked as completed May 20, 2005.

1.3 AIRCRAFT INFORMATION

1.3.1 Airplane, General

The Bombardier Canadair Regional Jet (CRJ) CL-600-2B19 is a twin-engine turbo fanjet. It is certified under the bilateral certification treaty with Canada in effect since 1971. The CRJ-100 (also known as the CRJ-200 and CL-600-2B19) is included in FAA Type Certification A21AE; it was certified January 21, 1993.

The accident transport-category airplane, serial number 7853, was manufactured in 2003. Skywest Airlines was the sole operator of N960SW since its delivery from Bombardier in October 2003. The airplane was configured with 53 seats; 50 of which were passenger seats located in the main cabin.

At the time of this writing there are approximately 740 CL-600-2B19 series airplanes operated in the United States. SkyWest Airlines has the third largest fleet consisting of about 125 airplanes.

1.3.2 Maintenance, General

At the time of the accident N960SW had accrued about 4,126 hours of flight time. SkyWest Airlines maintained the airplane on a continuous airworthiness basis following the Bombardier maintenance inspection program. The engines' total time were also about 4,126 hours, as they were the original engines equipped on the airplane at manufacture. The most recent continuous airworthiness check was conducted on April 26, 2005, which consisted of an A-2 inspection.

1.3.3 Nose Landing Gear System Components

1.3.3.1 System

The nose landing gear (NLG) system is electrically activated and hydraulically operated by hydraulic system number 3. It is comprised of double-wheel and aft-extending (forward retracting) landing gear body. The NLG system encompasses a landing gear lever, proximity sensor system, extension/retraction actuators, uplock assembly, selector valves, priority valve, bypass valves, restrictors, downlock, and check valves.

1.3.3.2 Landing Gear Lever

The airplane cockpit is equipped with a landing gear control panel. The control panel is located beneath the EICAS panels in the middle of the center pedestal (between the pilot seats). A landing gear operating lever is installed in the control panel, which when manipulated, sends an electrical extension or retraction command to the proximity sensor system; it additionally sends ground signals directly to the selector valves. The handle consists of a two-position control lever, and is designed to move up or down to select landing gear position; it is held into position by two mechanical detents.

1.3.3.3 Proximity Sensor Electronic Unit

The proximity sensor system operates by identifying the position of targets and giving a resulting command. The system is comprised of the Proximity Sensor Electronic Unit (PSEU), multiple proximity sensors, and numerous switches. The PSEU receives information via proximity sensors to determine the position of the nose landing gear.

The PSEU serves several functions within the NLG system:

-determines if the airplane is on the ground or in the air

-monitors for gear up, down and transit status

-determines if the landing gear doors are open or closed

-provides commands to extend or retract the landing gear

-provides commands to open and close the NLG forward doors

-records faults of any contradictions or discrepancies

1.3.3.4 Actuators

A single piston, double-acting hydraulic actuator is utilized in the NLG system to hydraulically move the NLG body into the extended or retracted position. The actuator assembly includes a piston, cylinder, restrictor, and several hydraulic seals. The cylinder body is comprised of two hydraulic ports: one for fluid to extend the actuator piston, and the other used to permit fluid to the retract port (on the opposite side of the cylinder). Restrictors installed in the system control the speed of the actuator during extension or retraction.

The forward NLG doors are equipped with a similar type of actuator to position the doors in the extended or retracted (open or cl...