Fatal Nosewheel Landing

By Richard N. Aarons
Source: Business & Commercial Aviation

The nose gear separated and the nosewheel and tire assembly was located on the runway, adjacent to the main wreckage. Examination of the landing gear, landing gear selector handle, flaps and flap selector handle revealed that the landing gear and flaps were in the fully extended position. Emergency medical service personnel reported that they had to cut control cables and move the right wing to gain access to the occupants. Control continuity was confirmed from the elevator, through push-pull tubes and a bellcrank, to control cables near the aft cabin area. At the aft cabin area, one cable was cut and the other cable turnbuckle had melted. The cables then extended from that point to the forward cockpit area.

Continuity also was confirmed from the rudder through cables to the rudder pedals. The rudder cables had also been cut near the aft cabin area. Aileron control continuity was confirmed from their respective bull-wheels at the ailerons, through cables to the aileron sector assembly at the aft cabin area. The cables had been cut near that point and continued to extend to the forward cockpit area. Measurement of the elevator trim jackscrew revealed an approximate 13-deg. elevator trim tab down position. Measurement of the rudder trim jackscrew revealed an approximate neutral rudder tab position. A surprise finding was the right thrust reverser that was found in the deployed position. Penetration damage on the cowling underneath the reverser was consistent with the right thrust reverser being deployed during the impact sequence. The right throttle lever was observed in the aft position, near the flight idle stop, with its thrust reverser lever in the deploy position.

The left engine thrust reverser was found in the stowed position. The left throttle lever was in a mid-range position with its thrust reverser lever in the stow position.

The reversers are activated by pilot operation of the thrust reverser throttle levers and deployed by hydraulic pressure supplied by an engine-driven pump directed to the drive actuators. The reversers can only be deployed when the primary throttle levers are in the idle thrust position and the airplane is on the ground as sensed by either of the main gear squat switches. When commanded, the thrust reversers fully deploy within 1.5 sec. After deployment, engine power can be increased by moving the thrust reverser throttle levers aft for maximum reverse thrust. Stops installed on the thrust reverser levers are set to 90% N1 at sea level on a standard day. To stow the thrust reversers, the pilot can move the reverse thrust levers through the idle reverse detent to the stow position. The airplane was also equipped with an emergency stow switch for each thrust reverser, located on the cockpit glareshield. Investigators noted that a review of a Cessna 500/501 operation manual revealed: "Single-engine reversing has been demonstrated during normal landings and is easily controllable."Teardown examination of both engines showed that their respective low-pressure compressor fan blade tips were bent opposite the direction of rotation and sand had found its way onto the high-pressure turbine blades, consistent with the engines operating at the time of impact. The examination found no evidence of preimpact mechanical anomalies that would have precluded normal engine operation.

The Trip

The flight had departed Venice, Fla., Municipal Airport at 1149 for a 2-hr. flight. The pilot had filed an IFR flight plan. The en route phase was routine. At 1340, the airplane was at 7,300 ft. when an Atlanta Center controller approved a frequency change to the local airport common traffic advisory frequency (CTAF). The pilot acknowledged the frequency change, and no further communication was received by center controllers.

The pilot was 62 years old. He held a private certificate with ratings for airplane single- and multiengine land, and instrument airplane. He had a type rating in the Citation 501. Investigators said a review of the pilot's logbook revealed that he had accumulated a total flight experience of approximately 1,159 hr. About 185 hr. were in the accident airplane — all flown during the previous two years. He had flown the Citation about 8 hr. and 16 hr. during the 30-day and 90-day periods preceding the accident.

Review of performance data for the make and model airplane revealed that at an estimated landing weight of 9,500 lb., the airplane required a landing distance of approximately 2,180 ft. on a dry runway, without wind factored. The distance also assumed a landing reference speed (Vref) of 99 kt., a temperature of 25C and no use of thrust reversers.

The NTSB noted that the pilot had been involved in a prior accident on March 12, 2006, when he was PIC of a Piper PA32-301 that departed the side of a runway while landing. The probable cause of that accident was "the failure of the pilot to maintain directional control during the landing roll with a crosswind, resulting in collapse of the nose landing gear."

In its final report on the Citation accident, the NTSB noted, “Although manufacturer data revealed single-engine reversing has been demonstrated during normal landings and is easily controllable, the airplane had already porpoised and bounced during the landing. The pilot's subsequent activation of only the right engine's thrust reverser would have created an asymmetrical thrust and most likely exacerbated an already uncontrolled touchdown. Had the touchdown been controlled, the airplane could have stopped on the remaining runway or the pilot could have performed a go-around uneventfully.”

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