Dropping a Loaded Van on Soft Ground in North Platte
It is 1930 and you are at a truck stop in North Platte. You need to drop a loaded 53-foot van - 44,000 lb of cargo - and bobtail to the terminal. The lot you are assigned is unpaved, packed gravel over clay, and it rained two hours ago. The spot slopes gently toward a drainage swale, perhaps 2 percent over the 60-foot length of the trailer. The landing gear is a two-speed crank with a flat steel foot. The trailer has no chocks of its own; you carry one pair of rubber chocks in the tractor. Another driver tells you to just pull the fifth wheel release, pull out, and let the trailer settle, because "the spring brakes will hold it." You have 20 minutes before your appointment window closes and the terminal is 40 miles away.
1. List the uncoupling steps in order and explain why each one matters in this particular spot.
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Order matters, and on this ground the ground itself has to be handled first.
- Pick the firmest, most level spot available and get the trailer straight before you stop. If this spot is the only one, put a board or cribbing under each landing gear foot before it takes weight.
- Chock the trailer wheels. You have one pair - put them on the downhill side. On a 2 percent slope with a 44,000-lb load, chocks are cheap insurance against the trailer creeping.
- Set the tractor parking brake (yellow knob). That sets both tractor and trailer parking brakes.
- Lower the landing gear until the foot is firmly on the ground and has taken some weight - with a loaded trailer, crank until you feel resistance, then a couple more turns. The gear must carry the trailer before the fifth wheel lets go.
- Disconnect the air lines and electrical cord and hang them on the dummy couplers, clear of the frame.
- Release the fifth wheel and pull forward slowly, watching both mirrors. Stop as soon as the tractor clears the trailer, and check that the trailer is standing level.
The "just pull the release and let it settle" advice is how landing gear gets bent and how trailers end up on their nose.
2. The other driver says the spring brakes will hold the trailer on this slope. Why is that not good enough here, and what do you do if the landing gear foot starts to sink?
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Spring brakes are not a parking system you can trust on a slope, and the ground is the bigger problem.
- The spring brakes hold the wheels only if the drums, shoes, and chambers are dry and in adjustment. After two hours of rain, a trailer that has been sitting can have rust on the drums, and the brakes may not hold as well as they do dry.
- Soft gravel over clay is a bearing problem, not a brake problem. The landing gear foot concentrates the trailer's weight - roughly 30,000 lb at the nose with a load like this - onto a steel plate maybe 6x6 inches. On saturated clay, that plate sinks. As it sinks, the trailer tips, the load shifts, and the gear can fold.
- The slope keeps pushing. Two percent doesn't sound like much, but the trailer is constantly trying to roll toward the swale, and the spring brakes are all that is holding it.
If the foot starts to sink: stop cranking, put the trailer back under air if you can, and move the unit. If you cannot move it, crib the foot with hardwood or a wide board to spread the load, keep the chocks in place, and get help. Do not crawl under a trailer that is settling.
3. What happens if you release the fifth wheel before the landing gear is down, and why does the sequence put landing gear first?
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The trailer's nose - the upper plate and the kingpin area - drops until something stops it. Either the trailer's frame lands on the tractor's frame rails and fifth wheel, or the retracted landing gear hits the ground.
- Damage: bent landing gear legs, a cracked upper plate, a bent kingpin, damaged air lines and electrical cord, possibly a bent tractor frame or fifth wheel.
- Injury: anyone standing beside or behind the tractor is in the drop zone, and a loaded trailer's nose can come down hard enough to kill.
- The load: a sudden drop can shift or break cargo, and a dropped trailer is out of service until it is inspected.
The sequence puts landing gear before the release because the landing gear is the only thing that can carry the nose once the fifth wheel lets go. Never pull the release handle until you have visually confirmed the gear is down and loaded, and never let anyone stand between the tractor and trailer during the drop.