CEN10LA335
CEN10LA335

On June 21, 2010, at 0825 central daylight time, a Cessna 525A, N800VT, sustained substantial damage during a runway excursion from runway 17 (5,000 feet by 75 feet, concrete) at the Storm Lake Municipal Airport (SLB), Storm Lake, Iowa. The airline transport pilot and five passengers were not injured. The flight was registered to and operated by Clausen Investments, Inc., under the provisions of 14 Code of Federal Regulations Part 91 as a business flight. Visual meteorological conditions prevailed at the time of the accident. However, there were thunderstorms in the vicinity of the airport, and standing water was reported on the runway. An instrument flight plan was filed. The flight departed Oklahoma City, Oklahoma, at 0705.

In a written statement, the pilot reported that he canceled his instrument flight rules flight plan and proceeded to the airport visually, although there were thunderstorms in the area. The wind was reported from the south so he chose to land on runway 17. He reported that during the landing rollout, the wind shifted from a quartering headwind to a tailwind, and that he was unable to stop the airplane on the runway due to the “wet runway and the wind.” Unable to execute a go-around because of the runway length, the airplane departed the runway, causing the nose gear and the left main landing gear to collapse in the grass and mud about 325 feet from the departure end of runway. The pilot stated that he needed less than 5,000 feet of runway to stop. He stated that, “With the brakes fully applied, the aircraft responded as if it had none.”

A Federal Aviation Administration (FAA) airworthiness inspector examined the airplane at the accident site along with technical and safety representatives from Cessna Aircraft. The inspection of the tires revealed that the tire pressures were within limits. No chevrons, heat signatures, or skid indications were noted on the main gear tires. The brake fluid reservoir quantity was within limits. The brake accumulator pressure was within limits with the system pressurized and unpressurized. A ground test of the brake system was conducted and the wheel brakes activated when the cockpit brakes were applied. The ground test of the anti-skid system indicated that the system was operating normally. The anti-skid self test using the rotary test switch in the cockpit functioned as described in the aircraft manual. The anti-skid fault panel located in the nose of the airplane indicated no faults. The Enhanced Ground Proximity Warning System (EGPWS) and four components of the anti-skid braking system were sent to the National Transportation Safety Board’s (NTSB) inspector-in-charge (IIC) for further examination. The four components of the anti-skid braking system were the control box, the control valve, and two transducers. The FAA airworthiness inspector also reported that the pilot stated to him that there was standing water on the runway at the time of the accident.

The EGPWS was sent to the manufacturer for inspection and a data download. The examination of the data revealed that the airplane's flight did not trigger any EGPWS warnings. Consequently, the EGPWS only recorded one data point for the entire flight. The data point that was recorded provided the latitude, longitude, and altitude for the airplane when it was in the landing configuration and 50 feet above the airport/runway. The data point indicated that the airplane was 50 feet above and about 950 feet from the pilot’s reported touchdown point, which was just beyond the runway’s identification numbers. It was not possible to determine the airplane’s speed from the EGPWS data.

The NTSB IIC shipped the anti-skid components to the manufacturer for functional testing. The original build orders showed that the components were manufactured in 2002/2003. All of the components were tested and found to meet functional test requirements with the exception of 1 force vs. pressure test performed on the control valve. The force to actuate the unit was slightly less than the functional test requirements allowed. It was determined that this condition would have no effect on performance and was to be expected due to the age of the component.

The SLB Automated Weather Observing System (AWOS) 3 was out of service at the time of the accident. The 0815 surface weather observation at the Cherokee County Regional Airport (CKP), Cherokee, Iowa, located 16 nautical miles west-northwest of SLB, was: wind 250 degrees at 7 knots, 10 miles visibility, light rain, broken ceiling 8,500 feet, overcast 11,000 feet, temperature 19 degrees Celsius (C), dew point 17 degrees C, altimeter 30.00 inches of Mercury.

The Cessna CJ2 Model 525A Airplane Flight Manual (AFM) provides the information required for determining the landing distance for dry runways, wet runways, and water covered runways. The AFM definition of a wet runway is: “A runway is considered wet when there is sufficient moisture on the surface to appear reflective, but without significant areas of standing water.” The AFM definition of a runway contaminated by standing water, slush or loose snow is: “A runway is considered to be contaminated when more that 25 percent of the runway surface area (whether in isolated areas or not) with the required length and width being used, is covered by surface water, more the 3mm (0.125 inch) deep, or by slush, or loose snow, equivalent to more than 3mm (0.125 inch) of water.

The pilot reported that the gross weight of the airplane at the time of the accident was 10,200 pounds. He reported that there was standing water on the runway. Based on the CKP weather information, the headwind component for runway 17 was 1 knot. The airport elevation is 1,488 mean sea level. The temperature was reported as 19 degrees C.

The AFM Landing Distance Tables provided the landing distances required using the following parameters:

Example 1:
Pressure Altitude: 2,000 feet
Aircraft Weight: 10,500 lbs.
Temperature: 20 degrees C
Dry Runway Landing Distance with Zero Wind: 2,990 feet
Vref Wet Runway Landing Distance: 4,050 feet – 4,350 feet
Vref Water Covered Runway (0.125 inches): 5,900 feet – 6,250 feet

Example 2:
Pressure Altitude: 1,000 feet
Aircraft Weight: 10,000 lbs.
Temperature: 20 degrees C
Dry Runway Landing Distance with Zero Wind: 2,820 feet
Vref Wet Runway Landing Distance: 4,050 feet – 4,350 feet
Vref Water Covered Runway (0.125 inches): 5,900 feet – 6,250 feet

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