We've done this task so many times!

Flying Safety, June, 2002 by Joseph Richard

It was your ordinary day in the inspection section at Nellis Air Force Base, and four of us were getting ready to do a 1200-hour inspection on the landing gear system on one of our elite F-16s. This inspection requires all landing gear and their components to be removed so all the bearings, races, mount pins and such can be checked by machine shop for excessive wear.

So far this year the inspection section has completed seven of these inspections and we felt comfortable with the task at hand. It was a hot Monday in July and we were anxious to start this in-depth, four-day project. We already had the AFTO Form 781 preprints filled out, the new gear and all the consumables were on hand, so we were ready to go!

The team jacked the aircraft and everyone was assigned a section to work on. Scott was working on the left main gear with Chad, while Craig and I worked on the nose gear. We removed the nose gear without any trouble, and the left gear was coming along at a good pace. It was almost noon when we decided it would be a good time to break for lunch. We cleaned the area, put away the tools and went into the office for a needed break. After lunch, we were back to work and ended the day with all three landing gear removed from the aircraft. After we cleaned the area we had our normal end-of-the day section meeting. This is where we review the day's work and brief where we will be concentrating the next day.

We all came in the next morning ready to get the landing gear prepared for the machine shop inspection. Craig disassembled the drag braces and other components of the main landing gear. I swapped components from the old to the new nose strut. Scott cleaned the bearing areas on the airframe, since the machine shop was on the way to perform their inspection.

Later on that day, I started to clean some of the components in the parts cleaner before we took them over to the machine shop. Everything was going well and we were ahead of schedule. Then, there was a thunderous explosion. It was so loud that everyone came from his or her office to see what had happened. I quickly turned around, startled by the noise, and was shocked to see Craig sitting on the floor in a pool of red fluid with a stunned look on his face. A million thoughts were going thorough my mind. Was he injured? Was that blood or hydraulic fluid? What had happened?

Craig looked as if he just saw a ghost. I rushed over to see if he was okay and to find out what had happened. It was difficult for Craig to talk, as he was in a definite state of shock, sitting there in a pool of (thankfully) hydraulic fluid. After a couple of seconds of looking at the main landing gear shock strut, I pieced together what had just happened to him. He was disassembling the main landing gear shock strut and was in the process of taking off the landing light bracket. (The light bracket being mounted to the main gear strut has been changed after the Block 30 F-16 aircraft.) He had one of the retaining bolts removed and the second one halfway out when the strut came apart in front of him.

Why did the strut just blow apart? I discovered the strut had not been depleted of its 1900-PSI nitrogen charge during the removal process. On page one of T.O. 1F-16-C-2-32JG-10-1 Task 24-1, Removal of the Main Landing Gear Shock Strut Assembly, there is a warning before step 3 that states "Shock strut shall be depressurized completely. Failure to comply may result in injury to personnel." There is also another warning in the tech data (prior to step 16) to make sure the strut is depressurized prior to removing the landing light bracket from the strut.

Now we had to figure out what went wrong. Were the people involved qualified and did they have a T.O.? Yes. Were they hurried? No. All the workers have done this job plenty of times in the past, and they actually finished the same task just a couple of weeks prior to this event. So what went wrong in this chain of events? Two failures to observe key tech data warnings.

First--A failure to deplete the main gear strut prior to removing it from the aircraft.

Second--A failure to verify that the pressure was depleted prior to removal of the light bracket.

In either case, maybe they thought someone else had depleted the strut or that they would get to it later. In each situation an important Tech Data warning was missed. The missed warning could have caused Craig to be seriously injured. The lessons we learned (or relearned) from this were:

* Always read and follow the T. O.

* Don't assume someone else followed "The Book" when "The Book" asks you to verify something is done.

* It doesn't matter how many times you have performed a task, always review the T. O. for any changes that may have been incorporated since the last time you read the procedures.

The Thunderbirds and the Air Force got lucky this time and avoided a major incident and injury to key personnel, but next time it could be different. Make sure your landing gear maintenance procedures are by "The Book."