Citationjet (C525/C526) - CJ I / II / III / IV
Flight Crew Last 90 Days 99; Flight Crew Total 18600; Flight Crew Type 3120
Other / Unknown
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Object; Ground Excursion Runway; Inflight Event / Encounter Weather / Turbulence
Aircraft Aircraft Damaged; General Evacuated
Aircraft; Airport; Weather
A Citation CJ3 aircraft overran the departure end of Runway XY in snowy conditions. Weather at the time of the incident; according to the local AWOS; was wind from 140 degrees at 5 knots; visibility 10 NM; sky condition 1;200 ft. scattered; 4;100 ft. overcast; temperature 0 degrees C; dew point 0 degrees C; and altimeter setting of 29.81 inches of mercury. The captain contacted the company flight follower prior departure and was told; 'There is freezing rain aloft; but it is not reaching the surface.' This was in line with the forecast for the area.The forecast suggested that the freezing precipitation would move out of the airport area by arrival time; and that there would be a rising temperature trend such that it would be above freezing at the time of arrival. The flight crew was able to monitor the regional weather while enroute; including radar; using the XM weather feature installed in the aircraft. They were not able; however; to monitor the weather at Airport ZZZ as the AWOS is not connected to the ADDS (Aviation Digital Data Services). Aircraft X does not have a flight phone installed; so the dialup feature of the AWOS could not be used. Also; the crew could not communicate with the company after departure. As the aircraft approached the area; the crew was able to note that the precipitation had moved east of the airport. The AWOS was obtained approximately 50 nm southwest of the airport; and the decision was made to use the RNAV GPS approach to runway XZ in order to land into the wind. The approach was accomplished using radar vectors provided by approach control.[Company X] has a two-step procedure in place for company aircraft arrivals at ZZZ during inclement weather. The crew had utilized the first step of this procedure when they contacted flight following prior to departure for a condition report. The crew used the second step as they approached the airport by attempting contact with ground personnel via radio. Ground personnel use handheld radios to communicate with the crews; and it is not uncommon for crews to be unable to make contact until on about 5 mile final. This was the case on the day of the incident. When the crew made contact they were advised to miss their approach and attempt landing on runway XY; as only the north end of the runway had been sanded in anticipation of a runway XY arrival. This was most likely related to the fact that night landings are not permitted on runway XZ. Most company arrivals at this time of year occur after sunset so the airport routinely applies sand to the north end of the runway only. On the upwind the airport manager informed the crew that he had personally sanded the north end of the runway; but that a snow shower had passed over the field since the sand was placed; leaving fresh; wet snow.The aircraft was then vectored for the RNAV GPS approach to runway XY. The weather south of the airport was VFR and the crew was able to cancel IFR over the FAF. The remainder of the approach and landing were conducted visually. The aircraft landing weight; as provided by the FMS; was 10;290 pounds. This yielded an FMS calculated dry runway landing distance of 2;579 feet. The contaminated runway landing distance for slush or wet snow; from the AFM contaminated runway charts; was 3;800 feet. Declared landing distance for runway XY is 4;352 feet. There is also about 300 feet of pavement north of the departure end of runway XY that was not available for use for landing calculations as noted on the approach chart.Aircraft speed on short final was at V approach (106kt). Touchdown speed was at or slightly above the Vref of 98 knots. The aircraft right main landing gear contacted the ground just at the top of the runway numbers. The left main touched about 100 feet later; and the nose gear about 100 feet after the left main. The touchdown points were determined by inspection of the runway post-incident. Braking was initiated just after nose wheel touchdown. Initial braking action was poor; but the captain felt that; as in the past; braking action would increase upon reaching the sanded portion of the runway. This was not the case. Braking increased marginally in the sanded area; but was not sufficient to bring the aircraft to a stop on the paved portion of the runway. The CJ3 has an anti-skid brake system. Constant pedal pressure throughout the stopping effort is the recommended procedure. Constant pedal pressure was maintained throughout the landing rollout except in three brief instances where it was necessary to momentarily release the brakes in order to maintain directional control. The aircraft departed the end of the paved runway on the runway centerline; and continued approximately 300 feet through a grass clearway area before stopping against the airport perimeter fence. The distance from the nose wheel touchdown point to the aircraft's final resting place is estimated to be around 4;550 feet.The flight crew was uninjured and exited the aircraft without assistance. Damage sustained to the aircraft is limited to several scratches on the windshields and damage to the inboard corners of both flaps.Available performance information suggests that this landing should have been successfully completed. As noted above the contaminated runway landing distance for the prevailing conditions was 3;800 feet. In addition; runway analysis information provided by a [dispatching service company] suggested that the maximum landing weight for prevailing conditions could have been as much as 12;074 pounds; well in excess of the actual landing weight. Therefore; some variable must have existed at the time that would invalidate the performance calculations. The most obvious is that there may have been a thin layer of ice under the snow that was not detected by ground personnel. Airport personnel; along with the author; examined the runway about 90 minutes post-incident; and no ice was present beneath the snow at that time. Weather conditions were changing through this period; however; so it is at least possible that ice was present that subsequently melted. The flight crew would have no way of knowing this prior to touchdown. Another factor to consider in this incident is the action of the anti-skid system on the CJ3. The anti-skid system is supposed to be designed to modulate brake pressure to prevent wheel skid and maximize braking effectiveness through a wide range of conditions. During landing; it becomes active when the wheel speed reaches 59 mph; or 3 seconds after weight on wheels. There is also touchdown protection logic that releases brake pressure until the wheels achieve 59 mph in order to prevent tire damage caused by pilots landing with their feet on the brakes. In the pilot training manual for the CJ3; there is no mention of a time limit for this feature. This raises the question of whether in certain circumstances it may be possible for the antiskid to hinder rather than enhance braking.As has been mentioned earlier; the captain felt that there was some braking. In a discussion with the Director of Operations of Company X; who had witnessed the landing; the Director of Operations mentioned that the aircraft produced 'roostertails' of slush and that what the captain perceived as braking was actually just the effect of viscous friction. The Director of Operations further stated that he felt that; due to the characteristics of the anti-skid system; braking had never actually taken place. His reasoning for this statement was that no snow was piled up in front of the main wheels when the aircraft finally stopped.Several possible mitigations to this situation are as follow. They are not; however; manufacturer recommended procedures and are offered only as suggestions that might be used under the emergency authority provided under the FARs. They are:1. Turn off the antiskid when the speed reaches about 50 knots.2. Shut down the engines in order to kill any residual thrust. (The CJ3 does not possess thrust reverse)3. Raise the flaps when the speed reaches about 50 knots in order to increase weight on wheels and therefore braking effectiveness.
On approach to runway XZ was told to contact advisory frequency. Once contacted we were told by the airport manager (who was listening on frequency) that the runway was in better condition to land on runway XY due to recent snow fall. Because the winds were light and variable we were able to land XY. We then went missed and contacted approach control again and told them we would like to land runway XY instead. Again; once we were cleared and told to change to advisory frequency we were reassured that the runway was in fair to good conditions to land and get stopped.The captain was coming in to land and I was making my call outs. He was on speed and touched down right on the numbers. Once touched down Captain asked me to select ground flaps. I did what I was told and at that point we were committed to landing; unable to go around. We slid down the runway; as he was unable to get the airplane stopped due to the contamination which the resent snowfall had caused. As a result the captain over ran the runway and we came to a stop a couple hundred feet off the runway. The runway landing distance is 4;352. We calculated the numbers to land on a wet runway prior to landing and there was nothing saying that we could not perform. It was misjudgment on the runway conditions that caused this incident. No significant damage was done to aircraft and procedures for the company are being done to prevent such incidents in the future.
A Citation CJ3 aircraft overran the departure end of a Runway in snowy conditions. Actual runway condition was likely misreported. Additionally the anti-skid system may have hurt rather than helped the Captain to bring the aircraft to a stop on the runway.