SA-227 AC Metro III
Maintenance Airframe; Maintenance Powerplant
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
General Maintenance Action
Aircraft; Company Policy
While working Aircraft X's fuel quantity problem; we replaced the Number 1 probe on the left hand side of the aircraft. This maintenance task requires the removal of both inboard and outboard boost pumps on the inboard side of the left wing. After the probe and boost pumps were reinstalled on the left side; the boost pumps (RII) (Required Inspection Item) required an ops (Operations) check. The left Aux (Auxiliary) pump tested ok; but the main did not test. The problem was immediately traced back to the Left Essential Bus switch being in the off position. After turning this switch on; a large pop was heard; following by smoke and a visible flame. Coming from the aft side of the left hand console in the cockpit; directly below the L/H (Left Hand) essential bus switch. I immediately turned off power (with the battery switches); exited the aircraft and yelled to [Maintenance Personnel] that there was a fire; disconnected external power; disconnected batteries and started looking for a fire extinguisher; in that order. After a minute or so; [Maintenance Personnel] had noticed that the flames had gone out; and no flames were visible. No fire extinguisher was discharged; no fire alarms were activated; and no fire department were called due to believing we didn't need them. After re-entering the crew station; we noticed a good amount of smoke coming from the same panel. I opened the panel and removed the partition from that area and started investigating. I found that the L/H essential bus switch had both 4 gauge wires shorted to ground. The description for this switch references it as having about 150 amps of current. I did not immediately report this; but talked to [Maintenance Personnel] about the incident. My base Manager was not available at the time of the incident.This is not part of the safety report; but part of the aftermath; there is not a specific section for this; but it should be documented. Today; I received my first dose of 'backlash.' I talked to [Maintenance Personnel] today about the implications of saying this was a 'fire.' I was informed that [Other Mechanic] asked [Maintenance Personnel] to 'keep me on a tighter leash' and that 'someone needs to babysit him.' I am fully aware that I have yelling and swearing at me headed my way. The lack of repeat inspections on essential components and areas of the aircraft. These inspection intervals are there for a reason.
SA227 Mechanic reported aircraft smoke and visible flame was observed coming from a cockpit panel.