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By the Book

By the Book


Headquarters and Headquarters Company
50th Infantry Brigade Combat Team
New Jersey Army National Guard
Lawrenceville, New Jersey

Whether you fly or drive, we’ve all seen those same famous words in our operator’s manuals: NOTES, WARNINGS, and CAUTIONS! These simple messages are printed for a reason, and here is a recent example that highlights their importance.

Last year, an Army National Guard unit in my state was conducting a routine convoy movement from their home station to a field training site for the monthly drill weekend. Within 20 minutes of leaving, the lead vehicle experienced an abnormal vibration. The driver and crew both smelled smoke, followed by a loud noise and a sudden drop. The truck’s right-front wheel had just flown off.

How did this happen, you ask? Well, it turns out the M1097 High Mobility Multipurpose Wheeled Vehicle has a long history of similar problems. But here’s what you need to know. (WARNING: You may just learn something from this article!)

The M1097 HMMWV is one of the most widely used ground vehicles in the U.S. Army fleet. As a troop-carrying vehicle and prime mover, this type of HMMWV shares many common components with other vehicles and even uses the same maintenance manual. One unique feature of the HMMWV driveline is the geared hub assembly and spindle bearing. On the M1097, this system includes a lock washer and retaining nut that must be serviced and replaced after each semi-annual inspection.

When properly installed, the lock washer has slotted tabs that are bent into grooves on the retaining nut. This prevents the retaining nut from backing off while the vehicle is in motion. The service manual and repair procedure contain a very clear message: “WARNING, ensure lock tab on lock washer is bent completely into the slot on the retaining nut.” Guess what happens when you skip this step? The entire wheel falls off the vehicle!

Preventative maintenance checks and services, or PMCS as we all know it, is a crucial skill for vehicle operators. It’s a basic task that is routinely practiced at the operator level and reinforced with good leadership. But can you blame a private first class if the wheel falls of his truck? Even if they did their PMCS? In this case, no. You have to dig a little deeper.

The higher headquarters unit conducted an on-duty National Guard accident investigation to determine what went wrong. They discovered the accident vehicle recently returned from reset maintenance. This type of PMCS is 20- and 30-level work that goes well beyond checking your tire pressure and oil level. The operator and crew were not at fault. The problem in this case was a geared hub assembly that was not rebuilt correctly and then not checked by a mechanic supervisor. The warning message was skipped, and the vehicle was returned to the fleet. From the outside appearance, there was no indication of fault or failure even though anyone inside the vehicle could be seconds away from a real disaster.

Did the mechanic intentionally ignore the warning message? I don’t think so. Did the mechanic supervisor intentionally fail to check the mechanic’s work? I doubt it. But right or wrong, the maintenance quality assurance process should have caught this problem. In the safety world, we call this type of mistake “human factors,” and the majority of all Army accidents share this problem.

In the case of this HMMWV accident, no Soldiers were injured. The crew was wearing proper gear and driving the correct speed. The M1097 veered off the highway and onto the shoulder, where it was later recovered without incident. The accident could have been much worse if any of those procedures had not been followed. In the end, the only true cost was some pride and a few dollars’ worth of common parts.

The lesson in this accident is simple: Pay attention to your safety messages! It turns out the retaining nut and lock washer on the M1097 is a well-documented problem. The first Safety of Use Messages describing the issue were published more than 10 years before this accident occurred. That was eight and half years before this young accident driver even joined the Army. He would have never known about this history. For those of us who have been on duty for several years, this accident serves as a great reminder. Take time to read and understand older safety messages on your equipment and comprehend the impact.

Warning messages like the one discussed above are printed in the operator’s and maintenance manuals for a reason. You need to take them seriously and make sure all of your subordinates do the same. Injury to personnel and damage to equipment will happen if you don’t pay attention. After a maintenance task is completed, don’t forget about quality assurance. Always have someone inspect your work. As leaders, operators and maintainers, it is our responsibility to do our jobs by the book. That goes for every task, every standard, every time. If not, the wheels might come off when you least expect it!

  • 1 January 2017
  • Author: Army Safety
  • Number of views: 1478
  • Comments: 0