PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Flight Crew Commercial; Flight Crew Flight Instructor
Aircraft Equipment Problem Less Severe
General Maintenance Action
Aircraft
We are approaching runway for full stop landing. Everything looks like it is planned. Once we descent to our minimum descent altitude for the approach; I ask my student to remove his foggles to do a landing. Once visual contact with the runway and we are preparing for landing. The student set up for a full flaps and 65 knots approach. The airplane descend as close as possible to the runway; and we begin our roundout and simultaneously reducing the power to idle. Once we put the throttle to idle and flaring the airplane the engine sounds stops and the propeller stops spinning.During ground roll upon landing; I communicate with the tower that the engine stops working and we are ground rolling using the potential energy created by the descent. Luckily we are able to exit the runway to taxiway foxtrot.First we troubleshoot make sure everything is in order and on ON position (mixture; throttle; magneto). We try to restart the engine three times. The first two time we started our engine using the normal procedure; standard Operating Procedure that is specified by the FOM but it did not start. The last attempt I try to lean the mixture; thinking that the cylinder might be flooded with fuel but still no luck. I ask the tower if it's possible to pull the airplane to a FBO ramp so we don't need to block the taxiway. Once in the ramp; I tried to troubleshoot again the airplane by visually scanning the engine for possible abnormal FOD or missing screw but I cannot found anything suspicious. I called the head of the maintenance to be able to help me troubleshoot the problem and he gave me procedure to look and try to restart the engine. The engine was able to restart by using primer but cannot hold low RPM. We decided to stay in ZZZ for the night and wait for the maintenance to fix it the next day.The reason why the engine quit is there is screw that [fell off] during flight. Maintenance was able to repair it the next day. The missing screw is position on which it's really hard place to see and maintenance needed to remove the cowling of the airplane to fix it.
The reporter indicated that it was the carburetor mixture screw that had backed out and was lost during flight.
A flight instructor described an engine problem on landing. The engine was unable to run with the throttle pulled back to idle due to the loss of the carburetor mixture screw.