Maintenance matters

Flying Safety, June, 2002

Editor's Note: the following accounts are from actual mishaps. They have been screened to prevent the release of privileged information.

LET'S TALK POWER, OR LACK THEREOF...

Without the engine, an aircraft doesn't go very far. It seems we maintainers have a knack for finding ways to FOD our motors, or just not quite do things the right way to ensure the operators can keep the motors running. In fact, we do it to ourselves time and time again.

Do You Have All The Pieces?

Afrcraft maintenance personnel were tasked with troubleshooting a C-5 #3 engine generator discrepancy. Worker 1 performed the outside walkaround and the required intake/exhaust inspection of all four engines. During the #4 engine inspection he found a nut and washer missing from the fan stopper. The fan stopper is a wooden handle with a heavy rubber tip attached to sheet metal and secured by three screws. He finished the inspection of the #4 engine, then re-inspected the #3 engine to ensure it was clear of FOD. Finding none, he documented the inspections in the aircraft forms. Good work ethic, right?

Worker 1, along with two co-workers, started and warmed up the engines and performed their assigned task. After the run, Worker 1 performed the required post-flight intake inspection, and guess what he found? FOD damage to the #4 engine fan blades and surrounding areas! Where could it have come from?

During the initial investigation a screw was found lodged in the #4 engine fan blade's second stage outer shroud. This screw matched the two other screws that were installed in the fan stopper handle. IAW T.O. 1C-5A-2-1, the fan stoppers are to be inspected prior to use. However, there is no criteria for inspecting the fan stopper.

How could we have prevented the $350,000+ repair cost and lost mission-capable time of a critical airlift asset? How about closer attention to detail or more defined directions? Or if you don't have all the hardware, stop and find out where it went before you start the engines.

Did You Put The Cap On?

One of our F-16CG aircraft came home with an engine exhaust nozzle problem. A Jet Troop and a Crew Chief proceeded to change the engine-driven hydraulic pump servo filter to correct the slow-to-close nozzle JAW 1F-16CG-2-78-00-1. The task was completed, and an operational check was performed with no leaks noted, so the aircraft was returned to service.

The aircraft then proceeded to fly the next sortie of the day. Unfortunately for the pilot, he got to come home early as the exhaust nozzle was stuck at 75 percent and the oil pressure was fluctuating out of limits. The pilot landed uneventfully and the aircraft was turned over to maintenance, again!

"What happened?" you may ask. Post-flight inspection revealed the engine hydraulic pump servo filter cap hanging by the safety wire, with oil leaking out of the filter. There was no damage to the threads on the cap, the threaded portion of the hydraulic pump servo, or to the safety wire. In addition, the pump checked out good during a backshop bench check. So, why did this happen?

No one knows for sure how the cap came loose. It was discovered that the F-16 Career Field Education and Training Plan (CFETP) does not directly cover the filter in question. The CFETP just lists "remove and replace filters." It's up to the individual and their supervisor to ensure they know all the tasks required by the aircraft. We train our people on many tasks during upgrade, and some tasks have many different parts. If you need to narrow the field in the training record, take the few extra minutes to make an AF Form 797 entry to cover the additional task. Even better, contact your career field manager and see if you can add the task to the CFETP. The few extra minutes you spend on paper will be gained back by ensuring the Air Force has fully-qualified airmen.

Was The Seal There Or Wasn't It?

Another one of our F-16s was rejoining on a tanker and had a little in-flight oil problem. He safely returned the aircraft to the nearest landing field and called for maintenance, as there was oil on the underside of the aircraft. When the maintenance recovery team arrived they found all four chip detectors properly seated, but the number four detector was missing one O-ring and the second O-ring was cut. The MRT then serviced the engine with 21 half-pints of oil, out of the 47 half-pints total capacity...

What caused this engine event? Simply put, there are two scenarios that could have happened. Either the O-ring was not installed during the post-flight inspection chip detector check, or the seal blew out during flight. No one knows for certain which event happened. Bottom line...when you do the routine pre/post-flight task, ensure you check everything!

How Much Oil Can We Use Per Flight Hour?

In preparation for an over-the-pond deployment, the mishap unit performed several phase inspections which require the engine AC generator to be removed, as was done on the mishap aircraft. After the phase inspection, the required leak checks were performed to include a hot servicing of the engine. The aircraft forms showed 45 half-pints of oil were serviced into the engine. The aircraft then flew one .6-hour sortie. In addition to this sortie, there were two maintenance runs completed due to a fuel malfunction during the sortie.