NTSB Factual Report

HISTORY OF FLIGHT

On September 16, 2013, about 1126 Pacific daylight time, a Cessna 180-B, N5112E, was substantially damaged when it ground-looped just after landing at Roberts Field (RDM) Redmond, Oregon. The private pilot/owner of the high-wing, tailwheel-equipped airplane was not injured. The business flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no FAA flight plan was filed for the flight.

According to the pilot, per the instructions of the controller in the air traffic control tower (ATCT), he entered a left downwind leg of the traffic pattern for runway 10, and was subsequently cleared to land. The automated terminal information service (ATIS) broadcast, reported a wind direction of "variable," with a speed of 3 knots. When the pilot reported to the ATCT controller that he was midfield on the downwind leg, the controller informed him that the wind was 340 degrees at 4 knots.

The approach and touchdown with full flaps were normal, but just after the touchdown a wind gust lifted the left wing, and the pilot was unable to successfully counter it. The airplane veered to the left, and the right wing and horizontal stabilizer contacted the runway surface. The airplane came to a stop facing back towards the approach path. The controller asked the pilot whether he required any assistance, and the pilot responded in the negative. The pilot was then cleared to taxi to his destination on the airport, which was then accomplished uneventfully by the pilot.

Subsequent examination of the airplane revealed that the right outboard wing and right horizontal stabilizer sustained substantial damage from the runway contact. The pilot reported that there were no pre-accident mechanical failures of the airplane.

PERSONNEL INFORMATION

The pilot reported that he had 1,068 hours total flight experience, including 520 in the accident airplane make and model. His most recent FAA third-class medical certificate was issued in April 2013, and his most recent flight review was completed in that same month.

AIRCRAFT INFORMATION

The airplane was manufactured in 1958, and had accumulated a total time of about 1,914 hours in service. The airplane was of the high-wing, tailwheel configuration.

METEOROLOGICAL INFORMATION

RDM was equipped with an Automated Terminal Information Service (ATIS) system that broadcast basic airport meteorological and runway use information. The ATIS broadcast that was current for the time of the accident and was received by the pilot was "Information Whiskey, valid 1756 Zulu, wind variable at 3, weather better than 5000 and 5,"temperature 18, dew point 7, altimeter 29.97, runways 10 and 22 in use."

The METAR that was issued about 30 minutes prior to the accident reported winds from 330 degrees at 10 knots, and the METAR that was issued about 30 minutes after the accident reported winds from 280 degrees at 5 knots.

AIRPORT INFORMATION

Information provided by the Federal Aviation Administration (FAA) indicated that RDM runway 10 measured 7,000 feet by 100 feet.

ADDITIONAL INFORMATION

Airplane Manufacturer's Owner's Manual Information

The Cessna Owner's Manual (OM) for the accident airplane contained minimal guidance regarding landing flap settings and operations. The OM stated that "Normal landings are made power off with any flap setting," and then followed with "The approach is steep with full wing flaps, but slips are permissible with wing flaps extended if necessary." The OM power-off, wings level, full flaps stall speed was listed as 56 mph.

Airplane Flying Handbook Information

Chapter 8 "Approaches and Landings" of the Airplane Flying Handbook (FAA-H-8083-3) contained some guidance on post-touchdown wing rise. The following statements were extracted directly from that document.

When landing in a crosswind, there may be instances when a wing will rise during the after-landing roll.

Any time an airplane is rolling on the ground in a crosswind condition, the upwind wing is receiving a greater force from the wind than the downwind wing. This causes a lift differential. Also, as the upwind wing rises, there is an increase in the angle of attack, which increases lift on the upwind wing, rolling the airplane downwind.

If no correction is applied, it is possible that the upwind wing will rise sufficiently to cause the downwind wing to strike the ground.

In the event a wing starts to rise during the landing roll, the pilot should immediately apply more aileron pressure toward the high wing and continue to maintain direction. The sooner the aileron control is applied, the more effective it will be. The further a wing is allowed to rise before taking corrective action, the more airplane surface is exposed to the force of the crosswind. This diminishes the effectiveness of the aileron.

Automated Surface Observation System (ASOS) Location

RDM was equipped with an automated surface observation system (ASOS), which sensed and recorded multiple meteorological parameters, including wind speed and direction. The ASOS wind sensor was located about 1,000 feet beyond the runway 22 threshold, and offset about 700 feet southeast of that runway centerline, which placed it about 5,000 feet east-southeast of the accident location on runway 10.

The ASOS equipment was situated in a flat, open section of the airport, with no nearby features that could mask or alter the sensed winds. In contrast, there were numerous buildings located about 700 feet both northeast and southwest of the runway 10 landing zone. According to the Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25) "Obstructions on the ground affect the flow of wind and can be an unseen danger. Ground topography and large buildings can break up the flow of the wind and create wind gusts that change rapidly in direction and speed ... It is especially important to be vigilant when flying in or out of airports that have large buildings or natural obstructions located near the runway.

ASOS Data Processing

Processed ASOS data was used as the source data for the ATIS and METAR reports. Repeater readouts of the ASOS winds were available to the controllers in the ATCT.

Review of the ASOS data capture and processing methods revealed that raw wind information was sensed and recorded every second. That raw, 1-second interval data was overwritten every 14 hours, and was not available for the investigation, because the investigation did not request the data within the 14-hour window.

The highest-fidelity wind data available to the investigation was processed data that was captured at 1-minute intervals. The processing consisted of data smoothing algorithms that were used to minimize "erroneous" wind readings, with the primarily purpose of minimizing unnecessary service calls for the ASOS equipment.

The 1-minute data included both "gust" (or "peak") and "sustained" wind speed and direction values for each time point. The gust values were predicated on a 3-second sample window, while the sustained values used a 5-second sample window; the gust window was always contained within its respective sustained window.

Review of the 1-minute interval ASOS wind data revealed that the wind direction recorded by the system was from the north, and changed about 60 degrees in the minute surrounding the time of the landing. The recorded speeds were between 4 and 7 knots.

NTSB Probable Cause

The pilot's inability to counter an unexpected wind gust after touchdown, which resulted in a loss of directional control.