Date: 201603
Local time of day: 0601-1200
Location: BTL.Airport, MI
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Cirrus Aircraft Undifferentiated
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Landing
ATC / advisory: Tower BTL
Reporter organization: FBO
Reporter function: Instructor; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Multiengine
Human factors: Situational Awareness
Second reporter function: Trainee; Pilot Flying
Anomaly: Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Airport; Human Factors; Weather
Primary problem: Ambiguous

Narrative: Student and instructor were coming back from the practice area. A discussion about runway conditions; the type of landing; and what would be different (application of brakes; letting the airplane coast more than normal on the contaminated runway; what will happen in the event of slippage/stuck brake) on this particular full stop landing took place in the downwind leg of pattern. The student took the landing with the instructor shadowing on the controls. Approach; flare; and touchdown were stable and controlled. The aircraft maintained a straight roll out path on runway centerline for about 2-3 seconds before the nose slowly drifted to the left. The student applied light braking to the right with little success. Instructor took control and applied rudder deflection and greater brake pressure to the right. The aircraft initially responded by correcting to a straight roll out path; then veered left again and departed the runway regardless of rudder/brake pressure applied to the right. Crew notified Tower and performed shutdown. No injuries noted.A thorough weather briefing; indicating runway MU values in the mid-high 20s was obtained prior to launching. ATIS was obtained prior to entering BTL airspace. At the time; runway conditions were thin dry snow over ice with MU values in the mid 20s. The MU values below 40 indicated less than ideal braking; but not impossible landing conditions. The crew believed the contaminated runway to be an acceptable risk. A better understanding of braking action reports; aircraft landing performance on; and different landing procedures for contaminated runways could be gathered and applied to conditions such as these to help determine the likelihood of conducting a safe flight.


Second narrative: Student and instructor were coming back from an instrument practice lesson. Approaching the airport and entering the downwind; the crew briefed the landing and made special note for landing on the contaminated surface and what exactly could happen. It was made clear that the student would have control and the instructor would shadow along for safety. The approach; flare; and touchdown were all controlled and stable. A straight roll-out path remained for about 2-3 seconds after touchdown before the airplane veered left of centerline. Instructor took control to correct; and the roll-out path straightened back up. Airplane again started veering left no matter how much rudder and braking action was applied to the right. The aircraft left the runway surface into the snow at a very slow speed. No injuries were noted.


Synopsis: A Cirrus pilot and instructor reported a loss of control and runway excursion at BTL due to field conditions.