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.
Complaints were made by three mechanics regarding the lubrication of a part on an MD-83 jet.
The Federal Aviation Administration plans to investigate safety complaints by three Alaska Airlines mechanics relating to the lubrication of a part on an MD-83 jet.
While it is management’s job to provide mechanics with the correct tools, it’s every mechanics’ responsibility to insist on getting the right tool – or getting engineering approval to use an...