Skyhawk 172/Cutlass 172
Air Traffic Control Fully Certified
Air Traffic Control Radar 6.0
Situational Awareness; Training / Qualification; Workload
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; General Declared Emergency
Aircraft; Environment - Non Weather Related; Procedure
A C172 pilot informed me that his engine hadn't quit; but was missing and would be 'going fast.'  I informed the pilot of the position of the nearest airport; his destination; and asked if he had it in sight.  I believed he had enough altitude to reach it; but he did not have it in sight.  Two minutes later; the pilot informed me that he would not make the airport and intended to land on the interstate.  The map confirmed his position over the interstate.  I issued the wind at my airport and updated his position with respect to the nearest airport.  Another aircraft checked in and asked if anyone was out to assist.  One minute later; I informed the distressed aircraft that they were; 'Radar contact lost;' with a last observed altitude of 1;200 feet and asked the pilot to stay in communication with us as long as possible.  One minute later; the monitoring pilot relayed communication that the C172 was safe on the ground and was asking for a phone number.  I relayed the facility recorded phone number and attempted to establish the number of passengers.  The pilot immediately telephoned and spoke with the Front Line Manager.  Having the other aircraft assist with relaying communication greatly improved the situation; since we were able to verify the status of the aircraft and communicate a phone number to the pilot.
Near midnight; a VFR C172 engine failed while the pilot was talking with ATC who advised him about location until loosing radar. Then another pilot relayed the distress aircraft position until it landed safely on an Interstate Freeway.