Skyhawk 172/Cutlass 172
Workload; Confusion; Communication Breakdown; Situational Awareness
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway; Inflight Event / Encounter Fuel Issue
Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Declared Emergency
Aircraft; Human Factors
I was working Local Control and had just taken the position.  A target was approaching the Class Delta from the southeast squawking 7700.  Approach had advised me that they weren't talking to the plane and it appeared to be descending.  I reached out to try to talk to the plane and heard no response.  As the plane got closer; the crash crew was called and informed of an Alert 2 and that there was a plane to the east that wasn't in contact with any ATC and appears to be lining up to Runway XX.  A green light gun signal was given to the pilot as he approached final for Runway XX.  The plane then flew north of the field and stayed within a distance that would be appropriate for a VFR traffic pattern.  The plane flew westbound and then appeared to be setting up for left base for Runway X.  The plane was again given a green light gun signal to be cleared to land.  The plan then continued to turn south and east and appeared to be setting up for a left downwind for Runway XX.  At this time the pilot changed his squawk to 7600; indicating no radio.  The plane was again given a green light.  The plane then continued to fly east and turned northwest and descended for a left base for Runway XY.  Runway XY was a closed runway with a large yellow X at both the approach end of XY and the approach end of Runway Y.  The plane was given a flashing red light-gun signal meaning airport unsafe; do not land.  The plane continued and landed without further incident on Runway XY and cleared the runway at taxiway hotel.  The crash crew continued toward and met the plane at the intersection of Taxiway Hotel and Taxiway Bravo.  The pilot told airport Management he was lost; low on fuel; and had problems with his alternator or battery and had turned his radio off.Recommendation: The plane was low on fuel and the pilot was lost and had no radio.  The pilot let ATC now of his situation the best he could by squawking the discrete emergency code 7700 and no radio 7600.  The closed runway was clearly marked as closed by the large X's at the approach end of each side.  I recommend if a pilot has an emergency; the pilot should land on the nearest runway to his/her flight path.
An ATC Local Controller reported a NORDO C-172 with an electrical failure and low on fuel squawked 7700 then 7600 before landing safely on a closed runway.