SALT LAKE CITY, UT, USA
N205AU
Boeing 737-200RS
The flight crew said that when they raised the landing gear handle after takeoff, the master caution light illuminated as the result of the loss of 'A' system hydraulics. The captain declared an 'emergency' and preparations were made to land on runway 16L (12,004 feet by 150 feet). The first officer conducted the landing using 15 degrees of flaps and a landing speed of 140 knots. When he deployed the thrust reversers, the left thrust reverser malfunctioned resulting in asymmetrical braking thrust. The airplane's operations manual indicated that with the loss of 'A' hydraulic system and an airplane weight of 89,600 pounds, a landing speed of 156 knots should be used. Directional control during the landing roll would have been accomplished using rudder and differential braking because nose wheel steering would have been inoperable. The captain reported to the FAA Inspector and Frontier Airlines officials that during the landing roll, he took control of the airplane. Photographs taken at the incident scene indicated that after 8,000 feet of runway was used, the airplane's tire skid marks became significantly darker, with right two skid marks darker than the left two.
On September 24, 1997, approximately 1127 mountain daylight time, a Boeing 737-200RS, N205AU, sustained minor damage when it departed runway 16L during landing rollout at Salt Lake City International Airport, Salt Lake City, Utah. The airline transport rated captain and first officer, 2 flight attendants, 2 nonpaying company employees, and 62 passengers, were not injured; however, 1 flight attendant received minor injuries. The airplane was being operated by Frontier Airlines, Inc., of Denver, Colorado, under Title 14 CFR Part 121. Visual meteorological conditions prevailed for the scheduled passenger flight which originated from Salt Lake City, Utah, approximately 10 minutes before the incident. An IFR flight plan had been filed with the destination of Denver, Colorado. According to the flight crew, when they raised the landing gear handle after takeoff from Salt Lake City International Airport, the master caution light illuminated as the result of the loss of "A" system hydraulics. They noticed that the main landing gear did not retract, whereas the nose wheel landing gear did. Simultaneously, the control tower informed them that smoke was observed coming from the vicinity of the right engine. The captain declared an emergency, and the Salt Lake City Airport Rescue Fire Fighting (ARFF) equipment was sent to runway 16L pending the return landing of Frontier Flight 776. The first officer had performed the takeoff, and the captain decided that the first officer would also make the landing. During the approach to runway 16L (12,004 feet long, by 150 feet wide), the nose gear was extended and locked using manual extension procedures, and the flaps were extended to 15 degrees using alternate flap extension procedures. The first officer landed approximately 700 feet down the runway at 140 knots. The spoilers were activated, but only the outboard flight spoilers operated due to the loss of "A" system hydraulics. Both thrust reversers were deployed; however, the left thrust reverser malfunctioned and did not deploy. The flight crew reported that the utilization of one thrust reverser resulted in asymmetrical braking thrust. The airplane's takeoff gross weight was 89,600 pounds. The emergency and abnormal procedures in the airplane's operations manual dictates the use of 15 degrees of flaps for landing without the "A" hydraulic system. The operations manual further states that landing with the above scenario requires a landing speed of Vref or 141 knots. Frontier Airlines' procedures for "normal landing roll" provides two sets of instructions for thrust reverser termination/stowing: first, "At 60 knots, reduce reverse thrust to be at IDLE reverse when reaching taxi speed;" and, second, "At 80 knots, reduce reverse thrust to be at idle reverse when reaching 60 knots." The flight crew reported that the right thrust reverser did not "stow" when the reverse thrust levers were put in the full down position. The Boeing 737 Operations Manual states that the failure of the "A" hydraulic system will result in the nose wheel steering being inoperable and the nose wheel would become free castering. Directional control during the landing roll would have been accomplished using rudder and differential braking, according to Frontier Airline officials. The captain reported to the FAA inspector and Frontier Airlines officials that during the landing roll, he took control of the airplane. Photographs taken at the incident scene indicate the following: at the 4,000 foot runway remaining marker, the airplane was off-set to the right from the runway centerline by approximately 25 feet. At approximately 3,800 feet remaining, the photographs indicate that the black tire marks, which were left on the runway, became darker/blacker and began curving to the right. The right two black marks appear darker than the left two, with the outboard left mark appearing the lightest of all four marks. With approximately 3,725 feet to 3,700 feet remaining, the right outboard black mark appeared to be intermittent "chatter marks" for approximately 50 feet. At this point, all four black marks appear more uniform in color, but the right outboard black mark is still slightly darker. The four black marks continue for another 300 to 400 feet before the right two black marks exit the right side of the runway and the left two black marks terminate approximately 3 feet before reaching the right side of the runway. The photographs further indicate that the tires left approximately 8 to 10 inch deep indentations in the soil for the remaining estimated 50 feet of its travel. The captain ordered an emergency evacuation after the airplane came to rest. The L1, R1, and R2 evacuation slides were used. All passengers and crew members evacuated the airplane safely, with the exception of one flight attendant who received minor injuries. Postincident examination of the "A" hydraulic system revealed a failure in a hydraulic line near the strut on the right engine. The Boeing Commercial Airplane Company had issued a Service Bulletin No. 737-29-1023, dated June 29, 1973, for the modification of the hydraulic line clamping, rerouting, and clearance. According to Frontier Airlines personnel, compliance with this Service Bulletin had not been performed on N205AU. The failure of the left thrust reverser to deploy was due to a left engine oil pressure switch failure.
The captain's failure to maintain directional control during landing roll. Factors were the loss of hydraulic pressure in the 'A' hydraulic system, the thrust reverser failure on the number one engine, and flight crew coordination not being maintained.
Source: NTSB Aviation Accident Database
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