A piece of ... what?
It was scheduled to have its first, low-power engine turn with the eight-bladed propellers on a Tuesday morning. We held a maintenance-turn brief in maintenance control. AWF1 David Pangia, AD3 Sean McMahon and I headed out to the flight line to perform two separate preflight inspections. We went through the engine bay and verified all parts were installed; everything seemed to be in order. The prop spun freely by hand, fasteners were safety wired, cannon plugs were installed and tight, and there was no visible FOD in the engine bay or its surroundings--or so we thought.
AWF1 Pangia and I were excited about being the first qualified ground-pounders to perform a low-power engine turn after a modification. Now came the moment of truth: as I placed the condition lever to "Run," and toggled the switch to start the starboard engine, we received a starter-control indication, right bleed air advisory light, fuel flow and light off, but no rpm indication.
We immediately aborted the starboard engine start in accordance with the NATOPS. We decided to start the port engine first, and the engine started normally. Next, we tried to cross-bleed start the starboard engine, but it wouldn't start. Realizing that we were still not receiving a positive rpm indication, we shut down the port engine and turned the plane over to power plants for further troubleshooting.
The first step was to verify the electrical wiring to the engine. Then the starboard tachometer was removed and replaced. The final step was to again turn the engine and see if the fruit of our labors would pay off. However, it was late afternoon and time to turn the aircraft over to night check.
The night-check supervisor briefed the crew on the status of the aircraft. They performed the low-power turn brief, preflight inspection, and prestart checklist before commencing the engine turn. This time everyone was confident that changing the generator tachometer had fixed the discrepancy. But again, the starboard engine had normal, initial start indications, but no rotation and no rpm.
The operator quickly aborted the turn because something was definitely not right. This time we tried to rotate the prop by hand, but it didn't move. Disappointed, we headed back to the shop to continue troubleshooting. With the MIMs in hand, we continued to the next step, which was to check the propeller brake. This brake prevents the propeller from rotating in the event of an airborne shutdown. The troubleshooters removed the starter, hooked up a torque wrench, and applied torque to release the prop brake, but it didn't budge.
"Did you hear that?" AD3 McMahon asked.
A grinding sound was coming from the compressor section of the engine. Something was seriously wrong. The power-plant mechs opened up the 5th and 10th stage bleed-air valves to inspect the compressor, and their worst fears were realized. Metal shavings were found inside the compressor case.
Where did these shavings come from? We inserted a boroscope, and after extensively searching for about an hour, AD2 Jonathon Butler froze for a moment. There was a six-inch piece of safety wire tangled between the blades in the 4th stage compressor.
As maintainers, it is our duty to provide pilots and aircrew a safe aircraft to fly. We take pride in delivering a platform in which they can return to their families day after day. Greyhawk power plants proved once again that they will do everything it takes to achieve this goal. By putting their training to work and troubleshooting step-by-step in accordance with the MIMs, they potentially avoided a catastrophic mishap.
The starboard engine of 635 was removed and turned into FRC for further investigation. The engine was eventually replaced, engine turns were completed, and the aircraft was returned for flight.
By AD1 Farzana Khan