Date: 201901
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Weather elements / visibility: Fog; 10
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Landing
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Communication Breakdown
Second reporter function: Pilot Not Flying; Instructor
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Contributing factors: Human Factors; Environment - Non Weather Related; Airport; Procedure
Primary problem: Ambiguous

Narrative: While Flying into ZZZ on a special VFR clearance. I was handed over to ZZZ Tower by Approach Control. I contacted the Tower reporting my position. I was asked if I was landing on the lake or strip. I advised I was landing on the strip and had the current ATIS advising [that] the strip was okay for SKI equipped aircraft. My plane is equipped with 3 straight skis. I also advised I would be discharging a passenger and wanted to depart out of the control zone. I received approval to land. On final; I asked Tower again if the runway was good for ski equipped aircraft. It appeared some sections were ice covered and the edges quite dark. Tower replied affirmative. I touched down and rolled (slid) out to approx. mid field and came to a stop on bare gravel. The airplane was stopped mid field without any ability to move. My passenger exited the plane and started to rock my wings while I applied power to try to relocate. The aircraft was not moving due to being on bare gravel and having 3 skis. My passenger exited the 50 feet to my left and was walking away when the Tower told me I had a pilot deviation and needed to call the Tower. Using full power and rocking the plane with all I had; the plane slid and hopped to the apron and on ice. I shutdown the aircraft and called the Tower on the phone. I was told I had unlawfully discharged a passenger on an active runway and the airport police were on the way. I explained the passenger only was outside the plane to help me get it moving but was told to remain where I was and the airport police were on their way. I told the Tower the runway was plowed to bare gravel and was not OK for skis and was told that was an Airport Maintenance issue and had nothing to do with the Tower. I watched the airport police drive by and disappear down the road and watched an Airport Maintenance vehicle appear and drive the full length of the runway and disappear off the apron and depart the area. I again called the Tower to tell them I was waiting for the police and was advised they had already talked to me. I had talked to my passenger and no one else. I called the Tower again on the phone again and asked if I could get a clearance out of the control zone to the north and was advised it would be VFR in 2 minutes. I reboarded the aircraft and after obtaining clearance I departed on the small patch of snow remaining.


Second narrative: After a routine flight to conduct a flight review for a private pilot/owner acting as PIC (pilot in command); we returned to land at our departure airport. They had gone to low IFR with a fog bank over the airport; however ZZZ was reporting 500-10; and at 2500 feet we had the field in sight from a distance of approximately five miles.After switching from Approach to ZZZ Tower and being cleared to land on the gravel strip; the PIC advised that he would be stopping on the runway. The Tower advised the pilot to report clear. The reason for the stop was to disembark the Flight Instructor; since the plane was on skis with a nose-wheel ski; and ground maneuvering is quite difficult with the tight turns required to exit and re-enter the runway. This allowed the Instructor to help get the plane moving again and assist in directional control until speed was built up.On final approach; the PIC noticed the runway appeared to have open gravel patches. The pilot questioned the Tower to be sure that the runway was open for ski-plane traffic; and was assured that it was. After landing on a snow covered area on the center of the approach end; the plane went over an area with no snow; and ground to a rapid stop. Subsequently; the plane had great difficulty moving; even with full power. The PIC ultimately exited the runway on to the parallel taxiway and departed shortly after the field went VFR. The Tower indicated a pilot deviation had occurred due to discharging a passenger on the runway. The Tower did not appear to be hearing or listening to PIC transmissions.


Synopsis: C172 pilot and flight instructor reported landing with skis resulted in a runway incursion after becoming immobile and off loading the instructor on the runway.