A Tower Controller reported a light aircraft returning to land due to aircraft problems rolled off the end of the runway. No damage or injuries; and the aircraft taxied to the ramp under its own power.

Narrative

Aircraft X; a VFR Mooney; was departing runway XXR northwest bound. Shortly after becoming airborne Aircraft X stated they needed to return to the runway. The CIC was able to immediately call the crash truck using the dial line at the back of the tower because the direct crash phone is out of service. The CIC (Controller In Charge) had to call the crash team twice because they hung up on the initial call. I had no other traffic in the airspace so I offered the Mooney the option to make a teardrop or enter the downwind; whatever the pilot needed and felt most comfortable doing reference the emergency situation they were experiencing. The piloted decided they wanted to make a teardrop and return; I cleared Aircraft X to land runway XYL and gave the wind. Due to the close proximity to the runway I did not want to distract the pilot with questions of the nature of the emergency; fuel; and souls on board. When the pilot was over the numbers I asked the pilot to check wheels down since I did not observe his nose light on. Aircraft X decided on a go around; stating he was too tight and high. I then offered the pilot to perform another teardrop and return to runway XXR or enter the downwind. The pilot said they would like to try the teardrop again. I asked the pilot if they had time and felt comfortable if they could state the nature of the emergency; he said that the oil filter flap and the cowling were unsecured. Once in the upwind I offered runway XA to the pilot; he declined; I re-cleared Aircraft X to land runway XXR. It appeared Aircraft X touched down at approximately taxiway 1 and kept going into the grass at the end of the runway. When the plane appeared to stop I told the pilot that the emergency vehicles were on the way; asked if he was okay; and when able to shut off the plane. The pilot stated they were okay and he continued to taxi the plane around in the grass and return to the runway to exit onto taxiway 1. I again verified that the pilot was okay and asked them to contact ground once he cleared the runway. He taxied under his own power back to the ramp. We need a working direct phone to the emergency crash team. Not having a working line is dangerous and unacceptable. I think if there was a way to extend the runway; add a longer overrun; or EMAS would be ways to help protect other aircraft from going off the end of the runway.