It was a Saturday in the fall on the island of Guam. Fall on Guam is very similar to the rest of the year except that the weather is very warm and muggy instead of hot and muggy. Assignment to the Backup crew didn’t mean much for most positions but for the pilots and the engineers it meant functional check flights if Maintenance completed actions on critical systems. Functional check flights (FCF) were done with minimum crew and were the only time the aircraft launched with parachutes for all personnel aboard. Crews usually just called them "FCFs" Check flights also required visual flight rules (VFR) weather or basically good weather and daylight. Supposedly the flights were called check flights instead of test flights for insurance purposes. The term check flights avoided potential legal issues if things went very bad on the flight..
The squadron had too few aircraft and needed every plane ready to get into the air. Maintenance had completed a replacement of a propeller which required the check. A scheduled mission would have to cancelled unless the check flight could be completed. Unfortunately, this was not a VFR day and the Executive Officer decided to authorize the flight under less than good weather conditions. Traditionally, the FCFs went off without a hitch so the decision seemed to be one with little possibility of going bad except for that pesky little fact that the FCFs shouldn’t be done in that weather. The decision was one that put the pilot in a small bind. Is this one of those times where you draw line and risk the career or take the chance? Pilots were hungry for any flightime. The younger aircraft commanders were especially eager for time and would readily take the FCF. The pilot wasn’t the best pilot in the squadron but he was probably the best on the island at that particular day. There’s not always time to weigh all of the possibilities before making a decision. When the call went to the pilot, he agreed to take the flight.
The low clouds guaranteed the flying would be on instruments a few seconds after liftoff. Except for the clouds, it was a great day for flying. Guam was warm year round but the clouds made the temperature quite pleasant. The preflight and brief were routine. Four parachutes were strapped into the galley area of the EC-130, Hercules aircraft, in preparation for the flight. These flights are good for the aircraft commander to occupy the copilot (right) seat and allow a junior pilot with some experience to have the controls. This allows the aircraft commander to orchestrate the checks. In this case the pilot chose to occupy the left seat. If anything went drastically wrong, only the pilot would get the blame and the penalty. Taking a check flight in instrument conditions even though authorized by the Executive officer would be indefensible. After a crew brief in the cockpit it was time for the “Before Start Checklist”. All of the switches were positioned according to the checklist and the pilot was ready to start. The pilot said “Clear number 3” into the microphone. The outside observer responded, “3’s Clear.” Next the pilot said, Turning number 3.” On engine start, there are a lot of things to look for and even to listen to. As the revolutions per minute passed 16%, the pilot looks for the fuel flow to begin. Around 35% rpm there should be static in the earphones as the igniters begin to fire attempting to light the fuel and start the engine. The engineer called, “Ignition.” The turbine inlet temperature started to climb rapidly toward the normal operating range for start. Soon the engine stabilized at the low speed rpm of 72%. At this point the pilot started rapidly scanning and rescanning the engine instruments. All were absolutely normal, but something was definitely wrong. The pilot's fingertips resting against the condition lever didn’t feel right. There was too much vibration. Many years before, an old flight engineer had told the pilot he should always have his fingertips against the condition lever or the throttle because it would tell him how the engine was doing and give an indication of excessive vibration. Detecting too much vibration in an aircraft where everything vibrates is a challenge. The fingertips knew something was amiss but how to communicate that to someone that hasn’t started a few thousand engines is difficult. The pilot wanted to start the next engine to have a comparison to make sure this wasn’t just imagination. The next steps were much like the first. “Clear number 4.” “Number 4 is clear” and then “Turning number 4.” As before the fuel flowed at 16%, the igniters started the crackling followed by ignition and the turbine temperature starting to rapidly climb toward normal. The engine stabilized in under a minute as required by the flight manual. The pilot was now sure. He turned to the copilot and said to the copilot, ”We aren’t going anywhere today.” The strange quizzical look from the copilot required an explanation. “There’s too much vibration on number 3.” What followed was a short course by the pilot for the copilot and the engineer on feeling the vibration of a C-130. The copilot and the engineer were clearly unconvinced. They felt and compared the 2 engines. Still unsure the engineer asked, “Why don’t we start the other two engines?” The pilot replied, “Sure, but we aren’t going anywhere.”
Engine number 2, followed by the number 1 engine starting were uneventful. The vibration convinced the pilot the decision was correct but the subtleties of the difference in vibration were not felt by the copilot and flight engineer.
“Maintenance, this is 172, we need a mechanic out here. We’ve got too much vibration on number 3.” Was the radio call the pilot made to squadron base.
“Roger, we’re sending someone out.”
The pilot was glad to see the tall petty officer first class walking out to the aircraft giving wide berth to the spinning propellers. Approaching from the nose of the aircraft the petty officer entered through the crew entrance door, and climbed up to the cockpit of the C-130. The petty officer on duty that day was one of the best and most hardworking of the squadron's mechanics. Once on the headset, the pilot explained the indications. The petty officer repeated the process of touching each engine control in turn. It was more of a “Mr Spock” mind meld type of event. His furrowed brow and then the nod indicated he felt the odd vibration.
The petty officer's next words were, “How about shutting down and let me take a look?”
In the cockpit, the conversation drifted on to other matters as a check stand was wheeled out and the various parts of the engine cowling were removed for inspection. After about 20 minutes, the petty officer reappeared in the cockpit reporting everything looked normal. But, being the professional he was, the petty officer had another plan. The check stand wheels were to be locked and the stand itself was to be chained down. He wanted to try another engine start with the cowling off and the petty officer standing on the check stand as the massive propeller turned inches from his head and body.
Another 10 minutes and the plan and precautions were in place. The linesman was was in front of the aircraft with a good view of the petty officer and the cocpit though neither the petty officer nor the pilots in the cockpit could see eachother. Again the Before Start Checklist was read from the top with the traditional challenge, action and response. The engine was ready for start.
“Clear number 3.” “Number 3 clear” came the response from the linesman. “Turning number 3.” Keith spoke into the microphone.
The rpm indicator jumped off of zero as the propeller started to turn. The flight engineer called “16% - fuel flow” as the fuel flow indicator quickly climbed. The static in the headset was followed almost immediately by the flight engineer’s “Ignition.”
A second later the linesman started yelling into his microphone, “STOP START! SHUT IT DOWN! SHUT IT DOWN!” Mental pictures of a bleeding or dead petty officer in dungarees and blue chambray shirt came to the pilot's mind. Fortunately that was not the case. The pilot could not imagine the signals the petty officer was making to the linesman but they were certainly effective. The engine had a broken engine mount was bouncing up and down on the 3 remaining engine mounts. The petty officer saw the real possibility of the 1,000 lb engine falling on top of him with the massive meat chopper attached to the front of it. The engine quickly slowed to a stop once the propeller brake kicked in.
In reality the engine would have probably stayed attached to the aircraft until rotation on the takeoff roll when the tilt of the propeller acting as a gyroscope would have added directional forces to the engine mounts already at max power force. An aircraft accident was averted. No report. No investigation. Everyone was unhurt and alive. The aircraft was undamaged except for a little maintenance. The crew returned to their homes and Maintenance continued their maintaining.
No comment was made about these events, however a decision was quietly made and implemented by the commanding officer to no longer allow check flights in bad weather or at night.
