Date: 201712
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Fairchild Swearingen Undifferentiated or Other Model
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Reporter organization: Air Taxi
Reporter function: Captain; Check Pilot; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure; Distraction; Confusion; Situational Awareness
Second reporter function: Trainee; Pilot Flying; Captain
Anomaly: Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types; Ground Excursion Runway
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Rejected Takeoff; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: I was the IOE Instructor captain in the right seat. The IOE pilot was flying from the left seat and was manipulating the controls during all phases of flight. During taxi to the runway IOE pilot mentioned that the right power lever was difficult to bring over the gate into the reverse position.While taxiing we received clearance to takeoff. The IOE pilot did his pre-takeoff checklist and then taxied onto runway XX. He lined the aircraft up with the centerline of the runway and came to a stop. ATC did advise that there was arriving traffic on a 5 mile final. The IOE pilot advanced the power levers slowly. The aircraft began to drift left of centerline. The IOE pilot applied some right brake and slowly advanced the left power lever to bring the aircraft back to the centerline. However; the aircraft continued to move to the left towards the left side of the runway. I said to bring the aircraft back to the right. I then instructed the IOE pilot to bring both power levers into reverse and abort the takeoff. The IOE pilot was attempting to bring both power levers into reverse even as I instructed him to do so. The right power lever did not get positioned into reverse due partially the difficulty mentioned earlier as well as the pilot's heightened anxiety pulling the lever harder against the stop.The aircraft continued left off the runway and came to a stop. Meanwhile; we pulled the Stop and Feather levers full out to stop the engines. Then we turned off the batteries. We then inspected the aircraft exterior and the runway edge lights. No damage occurred.There was some 'rush' created by ATC when they announced another aircraft on a 5 mile final. There are 2 choices in this case. The first is to not accept the takeoff clearance. The second is to proceed somewhat normally and if the arriving aircraft needs to go-around then that is to be accepted.When a situation gets critical; it is normal for people to tense up. In this case; that might have made it even more difficult to position the right power lever into the reverse position. It is important to try to stay less tense and apply normal pressure in order to achieve the desired result.In all twin engine aircraft; it important to be prepared for (almost expecting) an issue on takeoff; the most critical phase of flight in a twin. Therefore; when a deviation occurs the pilot is mentally prepared to abort if the situation warrants.


Second narrative: [Report narrative contained no additional information.]


Synopsis: Check Airman on a Metroliner reported that the IOE pilot lost control of the aircraft on takeoff resulting in a runway excursion.