Hamilton, MT, USA
N50CV
Cessna Citation 560
The pilot reported that while he was executing a visual flight rules extended straight-in approach to a full-stop landing, he encountered 10 knot wind fluctuations. He therefore decided to increase his approach speed by 10 knots. In addition to the increased airspeed, the pilot flew a flatter than normal approach descent angle. Due to the increased airspeed and the flatter approach, the airplane floated longer than normal after the initiation of the landing flare. Instead of executing a go-around after it became obvious that the airplane would not settle to the runway near the normal touchdown point, the pilot elected to continue the landing sequence. Once the airplane touched down, the pilot was unable to get it stopped in the remaining runway, and it departed the end of the runway and experienced a nose gear collapse after encountering rough/uneven, swampy terrain. The expected landing distance for the airplane was calculated based upon the Vref plus ten airspeed of 108 knots, a landing gross weight of 11,000 pounds, and the reported ambient weather conditions. According to those extrapolated calculations, the landing distance would have been expected to be about 3,100 feet. This distance does not include the use of thrust reversers, as the Model 560 landing performance charts for dry hard surface runways do not take into consideration use of the thrust reversers. The performance section of the Model 560 FAA-Approved flight manual stated that the landing is to be proceeded by, "...a steady three degree angle approach down to the 50-foot height point with airspeed at Vref in the landing configuration." According to Cessna Aircraft, maintaining a flatter approach, or an airspeed above designated Vref, will extend the landing distance beyond what is published in the performance tables. Review of the archived aviation surface weather observations (METAR) for Ravalli County Airport revealed that the winds measured at 1053, eight minutes after the accident, were from 150 degrees at five knots. The wind observations recorded at 0953 indicated calm winds, and the recorded winds at 0853 were 220 degrees at four knots.
On July 10, 2006, approximately 1045 mountain daylight time, a Cessna Citation 560, N50CV, experienced a collapse of the nose gear after running off the end of the runway while landing at Ravalli County Airport, Hamilton, Montana. The airline transport pilot and his passenger were not injured, but the aircraft, which is owned and operated by River City Flying Service, sustained substantial damage. The 14 CFR Part 91 executive/corporate flight, which departed Visalia, California, at 0815 Pacific daylight time, was being operated in visual meteorological conditions after canceling the instrument flight rules (IFR) flight plan the pilot had activated en route. An on-site inspection of the airplane revealed that a portion of the nose gear strut had been torn from the airplane about 60 feet before it came to a stop, and that the structure and skin around the nose gear wheel well had been crushed upward and torn aft. There were significant leading edge indentations present on both wings, and the last 18 inches of the right wing tip had been bent up at a 90 degree angle. In addition, there was significant damage in the right main wheel well area, to include the gear actuator rod being bent about 90 degrees and pushed up through the upper surface of the wing. It was also discovered that the right main gear anti-skid fault transducer had been activated. In his narrative report, the pilot stated that the winds were reported as light and variable, but while on extended final approach he encountered wind fluctuations of plus or minus 10 knots. He therefore decided to increase his targeted approach reference speed (Vref) by ten knots (from 98 to 108). He said that just after he flared and reduced the power to idle, a "gust of wind" caught the airplane and "caused it to float." At that point he elected to continue the landing sequence, and according to him, the airplane ultimately touched down between 1,000 and 1,300 feet past the approach end of the runway. He further stated that once the wheels were on the ground, he placed the thrust reverser levers in the "deploy position," but was unable to move the reverser levers beyond that position in order to increase reverser thrust. He said that he then applied "maximum breaking," and felt hard pedal pressure, but that he did not notice any "significant deceleration." He said that he continued applying hard braking pressure, and tried again to move the reverser levers past the deployed position, but was unsuccessful. According to the pilot, when the airplane departed the end of the runway, it was to the left of the centerline, and that when it came to a stop in a swampy area, the engines were still running. He therefore used the normal engine shutdown procedure, and then exited the airplane through the main cabin door. After the accident, the Cockpit Voice Recorder (CVR) was recovered from the aircraft and sent to the NTSB's Vehicle Recorder Division for readout. That recording revealed that the pilot had selected the landing flap position and armed the speed brakes prior to landing. It also revealed that about 30 seconds prior to touchdown, the pilot commented about wind variations and about the presence of a crosswind. According to the recording, about four seconds after touchdown, the pilot stated that he was "getting on the brakes," because he didn't "...have much left." According to the vehicle recorder technician, about ten seconds after the pilot made the comment about getting on the brakes, the recording revealed an increase in engine RPM similar to the use of reverser thrust. That RPM increase lasted for about six seconds. About two seconds after the increase in RPM began, there were several impact sounds, and a rumbling noise that lasted for about six seconds. In a telephone interview with the NTSB Investigator-In-charge (IIC), the owner of the airplane, who was sitting in the right cockpit seat during the accident sequence, said that the pilot came in on a "long flat approach," and that as he crossed the runway threshold, he was about 10 knots too fast. The owner further stated that the airplane floated "quite a long ways," and that it did not touch down until it was about 2,200 feet past the approach end of the runway. He further stated that he prefers that the airplane be flown at a steeper approach angle than the pilot was maintaining because "...it gives less floating." The owner said that it did not feel to him like there was any braking taking place until the last 400 to 500 feet of the runway. He also said that the braking that did take place did not feel to him like it was being sequenced by the Automatic Braking System (ABS). He also said that that it appeared that the reversers did not deploy until the airplane was about 500 feet from the end of the runway. The Federal Aviation Administration (FAA) Inspector that responded to the scene interviewed two pilot-rated witnesses that saw the airplane while it was on final approach, and then watched it throughout the landing sequence. Both witnesses said the airplane was lower than normal on approach, and that it appeared to be going too fast. They said that after the landing flare, the airplane remained airborne and floated a considerable distance down runway 34 before the main gear tires touched the surface. They reported that the tires appeared to first touch the runway surface somewhere between 1,200 and 2,000 feet past the approach end of the runway, but that the aircraft did not appear to have "weight on the wheels" until about the midpoint of the runway (about 2,100 feet from the approach end). They said that soon after the airplane passed the runway midpoint, it began to slow, but it did not slow at a rate that allowed it to stop until after it had departed the end of the 4,200 foot runway. They said that after it departed the end of the runway, it crossed over a grassy area and a creek, and came to rest in the swampy area around the creek. Both witnesses said they saw the thrust reversers in the fully deployed position during a portion of the landing sequence. One of the witnesses said he did not notice the reversers fully deployed until the airplane was about at the point where the brakes appeared to lock, which according to the skid marks on the runway was about 260 feet short of the departure end. The other witness said that the thrust reversers were deployed "approximately 1,200 feet" from the departure end of the runway. Both said that the winds at the airport were light and variable, and that the wind was not gusting. The FAA Inspector reported that both tires left clearly discernable skid mark patterns on the runway that were consistent with Automatic Braking System (ABS)-generated brake sequencing (see attached diagram). According to the inspector, near the left edge of the runway, starting 2,003 feet from the departure end, there was an ABS-generated braking skid mark that continued for approximately 1,743 feet. This skid mark, which he said was clearly associated with the left main gear tire, became a solid skid mark for about the last 260 feet of the runway. That solid skid mark then appeared to continue on the grass off the departure end of the runway for another 370 feet, to where the airplane came to a stop. According to the inspector, the right tire rolled over an area that was nearer to the runway centerline, and was therefore rolling over a surface that was more covered by previous skid marks and rubber deposits from other aircraft. He reported that the only skid mark in that area that could be clearly identified as having been produced by the airplane's right main tire, started about 1,160 feet from the departure end of the runway, and continued for about 900 feet. This skid mark was also consistent with ABS-generated skid sequencing. There was no clear skidding scar past the end of the runway in the area through which the right main tire passed. After reviewing the skid mark diagram created by the FAA Inspector, in a telephone conversation with the NTSB IIC, a Senior Investigator with Cessna Aircraft Company stated that the ABS-generated skid marks on the runway indicated that the ABS system was working properly during the portions of the landing roll where the pilot had applied enough brake pressure that the main wheels would otherwise have locked up if not regulated by the ABS system. He also stated that the right wheel fault indicator was most likely tripped during the sequence that lead to the extensive damage associated with the right main gear and the right main gear wheel well. The Cessna Investigator further noted that once the thrust reversers on this model airplane are pulled into the deploy position, it takes about one and seven-tenths seconds before the reversers are fully deployed. Only after the reversers are fully deployed will the solenoid release the reverser levers so that power may be increased. According to this investigator, if a pilot applies pressure to the reverser levers prior to the time the solenoid releases them, and that pressure is maintained during and after the time the solenoid is activated, the reverser lockout pin may not be able to release, and the levers will not be able to be moved passed the deploy position. As part of the investigation, the IIC asked Cessna Aircraft Company to calculate the approximate landing distance for this airplane, based upon the Vref plus ten airspeed of 108 knots, a landing gross weight of 11,000 pounds, and the reported ambient weather conditions. According to those extrapolated calculations, the landing distance would have been expected to be about 3,100 feet. This distance does not include the use of thrust reversers, as the Model 560 landing performance charts for dry hard surface runways do not take into consideration use of the thrust reversers. The investigation also revealed that the performance section of the Model 560 FAA-Approved flight manual stated that the landing is to be proceeded by, "...a steady three degree angle approach down to the 50-foot height point with airspeed at Vref in the landing configuration." According to the Cessna investigator, maintaining a flatter approach, or an airspeed above designated Vref, will extend the landing distance beyond what is published in the performance tables. A review of the archived aviation surface weather observations (METAR) for Ravalli County Airport revealed that the winds measured at 1053, eight minutes after the accident, were from 150 degrees at five knots. The wind observations recorded at 0953 indicated calm winds, and the recorded winds at 0853 were 220 degrees at four knots. It was also noted that in the weather information section of the NTSB Form 6120.1/2, the pilot indicated the winds were variable in direction, with a speed of three knots, gusting to five knots.
The pilot's failure to attain the proper touchdown point and to execute a go-around, which lead to an overrun of the runway surface. Contributing to the accident was his failure to maintain the correct landing approach speed (Vref), his failure to maintain the correct glide path, and the swampy and rough/uneven terrain the airplane encountered after departing the end of the runway.
Source: NTSB Aviation Accident Database
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