Rack and Ruin
GSE maintenance should not be an oxymoron, offers Tony Vasko.
By Tony Vasko
It's amazing that companies will expend heavy dollars on purchasing ground equipment and then let it be neglected, even abused, and then be surprised when it either fails to operate or even worse, fails and injures someone. The more sophisticated the units, the more they are open to going to rack and ruin.
Some equipment by virtue of its construction or design can resist this. The old CT-120 Clark tractors sat outside in rain and snow, got their oil changed whenever, and continued to grind away. Having fenders of cast iron two inches thick may have contributed to this resistance to neglect but little other equipment can boast that kind of construction.
RISE AND FALL OF A TAIL STAND
Take the large tail stand purchased by airlines X for use on the L-1011 aircraft. It was big and had a tower going up nearly 70 feet, which supported two long arms with catwalks that stretched out to the front of it. These were made to embrace the vertical fin of the aircraft and gave you access to any point on them. They had to be long to reach all the way up front around the S-duct. The arms were each mounted on a carriage that rode up and down in vertical tracks in the tower. Hoisting cables running off elevator winches provided motive force.
Self-powered, the unit mounted an engine with a large generator that in turn, powered hydraulic pumps. The hydraulic system powered the winches to raise and lower the arms. There was also a passenger elevator in the tower to carry mechanics up to the working level, where the big arms were set. Also, the whole stand was self-propelled. It rode on four dual wheeled casters with solid rubber treads. Two of the casters had hydraulic motors built in and there was an operator's station from which the whole affair was controlled. It had a steering wheel that was hooked to the casters by bicycle chains. Steering power was supplied by the luckless operator who had to be very strong, but smart enough not to apply too much force — the chains couldn't stand it.
The unit was heavy enough to dent asphalt ramps, and helped prove Newton's Law, Items at rest tended to stay at rest. If you poured enough hydraulic power to it, it would overcome the resistance and get underway with a lurch. Moving it on the open ramps was one thing. You could tolerate the lurch. Close up to the aircraft, lurching was not popular.
Its real Achilles heel however, were the big arms. They were heavy, of course, as they had to support their weight plus mechanics, tools, and equipment. The weight worked like a lever on the carriage. Going up was one thing. The winch turned, the cable was pulled in around the drum and up went the carriage and arm assembly. At least it would if the track it rode in was carefully cleaned and lubricated.
If the unit was not popular with the aircraft mechanics, it was less so with the GSE mechanics because they had to clean all 70 feet of the multiple carriage tracks that were exposed to the weather, and lubricate them, as well as the rollers in the carriages, the big casters, the steering system, and the elevator. Contempt for the unit led to neglect.
Aircraft maintenance would complain that the carriages moved with a series of jerks and stops as the arms were raised and lowered. The GSE mechanics then tried the mechanism out to see what was wrong, with one of them riding on the arm to watch the carriage as the arms moved in a series of fits and starts - just as the aircraft mechanics had said. Going up was not too bad. A hefty winch with a strong and heavy cable overcame the friction. Now it went down and the cable paid out. Nothing except the weight of the arms and carriage forced it down. The winch fed the cable and went slack and loose. A tension brake to prevent free fall had been misadjusted, setting the stage for catastrophe.
The GSE mechanic noticed that the carriage was jammed. I don't know if he moved or maybe even jumped a little or if the carriage decided on its own to let loose. Down went the carriage, arm, and mechanic until the carriage ran out of cable slack and there it suddenly stopped — at least the carriage did. The arm failed under the load of its own weight and inertia. The unfortunate GSE mechanic ended up being badly injured but fortunately, survived.
SO WHAT WENT WRONG?
Post mortems were mainly concerned with pointing fingers. The unit was badly designed. The tension brake had been blamed for causing the jamming. It had contributed, but was not the fault. In the end, the lack of care did it in. The lack of enforcement of the safety program allowed a GSE mechanic to be badly injured. Surely there were enough places to point fingers.
Widebody aircraft are difficult to work on due to their height and size. Brand X recognized this and built a facility to do heavy maintenance checks on their L-1011. Pride of place was given to a docking system that lovingly folded itself around the aircraft when hangared. You could climb up and touch the top of the vertical fin easily. It was an excellent unit in most ways.
When aircraft roll into hangars,the wing stands, etc. must be low enough to allow people to work on them. Then, the aircraft is raised up so that it is now out of reach. The answer, of course, is to adjust the stands, which was done by lots of jackscrews. Torque tubes fitted with universal joints powered them. There were lots of these, too. Still, with everyone clear and watching to make sure nothing on the stand hit anything on the aircraft, it was possible to raise and lower the dock system to the optimum position for work.
Like everything else, the dock system depended on regular maintenance, particularly cleaning jackscrews and lubricating them, while not neglecting universals and angle gearboxes. It was also not a good idea to do paint stripping and washing in the dock either. Paint stripper is unbelievably bad for anything except removing paint. It likes to eat rubber protective boots on jackscrews, too. In a perfect company, all this would have been recognized and a stringent cleaning and lube program would have kept everything in tip-top shape.
Brand X was not a perfect company. The expensive dock system withstood the lack of lubrication care for some time. The day finally came when things jammed. The motors applied their torque to raise or lower the dock platforms. The jackscrews, at least some, were not going to move. The torque built up and the torque tube couplings sheared here and there, some jackscrews turned and changed their height, others didn't. They fortunately stopped before it tore itself apart.
Being too expensive to repair, the dock was laboriously set at a compromised position. Like most compromises, it was not optimum and inevitably hurt production.
It's amazing how much damage a GSE person with some integrity to do the job properly and armed only with a grease gun, an oiler and a sharp set of eyes can prevent. And, how much money can be saved too. A million-dollar piece of GSE is junk if it is not maintained. But hey, you knew that already. Right?