Date: 201908
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Military Trainer
Operator: Military
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Final Approach
Airspace: Class G ZAB
ATC / advisory: CTAF ZZZ
Reporter organization: Military
Reporter function: Instructor
Reporter qualification: Flight Crew Flight Instructor
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Conflict Ground Conflict; Critical; Ground Event / Encounter Vehicle
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Aircraft X was on a pattern and landing training mission for a pre-Solo-student. Runway 9 in use; winds were calm. At the time of the incident; 3 other aircraft were on the ground; two other aircraft were en-route to join the pattern. Aircraft X was practicing engine failure patterns (short approaches abeam the numbers); which usually lead to a touch and go landing. This was also the case during the incident.During takeoff roll; both student and instructor suddenly saw a vehicle on the left side of the runway. The vehicle appeared to be partially on the runway or at least right next to the runway. The student pilot intended to abort the takeoff. The instructor did override this decision; as it would have not been possible to stop the aircraft on the remaining runway. A close; opposite pass of vehicle and aircraft occurred shortly thereafter.Once safely airborne; the instructor tried to communicate with the airport personnel via CTAF several times; but his calls were not answered. Three more approaches were flown; but all terminated in an early go around due to runway not being clear. The vehicle continued on/very close next to the runway alongside the complete runway for the next 15-20 minutes in what appeared to be mowing operations. This also prohibited takeoff off the two Bonanzas who at that time were holding short Runway 9. They also tried to contact the people working close by the runway; but were not successful either.As no communications could be established with the vehicle and further training was not possible; Aircraft X left the pattern. Airport Operations was informed about the situation and asked to contact [airport] via landline.Factors that led to this situation: The vehicle was not observed by the crew while on downwind. (Contributing factor: The vehicle was small and painted in a dark brown or green color and had no high visibility markings). Due to the high workload during an engine failure pattern; the crew did not see the vehicle at the far end of the runway during the approach and therefore performed a touch and go landing.This incident raises the following questions that I want to be answered:1.) Was the work conducted by the vehicle at the edges of the runway a preplanned activity? If so: a) Why was this work chosen to be performed during a time frame with a lot of flight activity vs times with low or no activity at all at the airfield (i.e in the afternoon)?b) Why was this not communicated to dispatch/pilots beforehand by use of flight pro or other means?c) Why is work on or near a runway with flying activity conducted without communication (i.e someone on the ground monitoring/responding to calls on CTAF). Are the personnel aware of the special circumstances that come with working near or on a runway? 2.) What will be done (i.e. establishment of procedures) to avoid future incidents similar to that one?




Synopsis: Instructor Pilot reported a unannounced vehicle on and near runway preventing practice landings at this private airport.