Da-42 flight crew reported a runway excursion during a simulated engine failure on takeoff.

Attributes
ACN	1501115
Time
Date	201712
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	DA42 Twin Star
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Route In Use	None
Flight Plan	None
Person 1
Function	Pilot Not Flying Instructor
Qualification	Flight Crew Commercial Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 45 Flight Crew Total 380 Flight Crew Type 33
Person 2
Function	Trainee Pilot Flying
Qualification	Flight Crew Student Flight Crew Private Flight Crew Instrument
Experience	Flight Crew Last 90 Days 65 Flight Crew Total 3269 Flight Crew Type 2
Events
Anomaly	Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types Ground Event / Encounter Loss Of Aircraft Control Ground Excursion Runway

Narrative:

My student and I were practicing engine failures prior to take off. I briefed him on the procedure for an engine out on the runway; and told him I would be failing one of his engines. I failed the left engine during takeoff at about 15 knots. Rather than pull power to idle; the student attempted to maintain centerline solely with use of the rudder. We left the runway surface left of the runway; and came to a stop in the grass. We taxied to the ramp; checked the gear for any damage; and returned to our home airport.in the future; I will brief the students on the procedure; and then show them the procedure myself before allowing the student to try. I will also position my hand in such a way to be able to remove the students hand from the throttles in the event of a failure to follow proper procedures.

Original NASA ASRS Text

Title: DA-42 flight crew reported a runway excursion during a simulated engine failure on takeoff.

Narrative: My student and I were practicing engine failures prior to take off. I briefed him on the procedure for an engine out on the runway; and told him I would be failing one of his engines. I failed the left engine during takeoff at about 15 knots. Rather than pull power to idle; the student attempted to maintain centerline solely with use of the rudder. We left the runway surface left of the runway; and came to a stop in the grass. We taxied to the ramp; checked the gear for any damage; and returned to our home airport.In the future; I will brief the students on the procedure; and then show them the procedure myself before allowing the student to try. I will also position my hand in such a way to be able to remove the students hand from the throttles in the event of a failure to follow proper procedures.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.