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NEWS > DEC 2019

In Today’s Era of Automatic Controls on Planes and Cranes, We Wonder, “How reliable are these machines?”

by Dennis J. O’Rourke, CSP

Some time ago, during a deposition, I made a comparison between a crane and a plane regarding operating and instructions to the operator/pilot. There are times when those who control these machines have to make critical decisions, and both of the devices contend with gravity. A rebuttal expert witness said he saw no comparison between planes and cranes. He (in my opinion) was wrong!

Photo courtesy of Dennis O’Rourke
Photo courtesy of Dennis O’Rourke

My analogy between the two machines was that important information for flying a plane was easily reviewed by the pilot while setting in his seat, the charts, and manuals are in front of them. The crane operator, in my example, needed to stand up, walk back, and read the tiny printed instructions riveted to a dark inside wall of the machinery house (P&H 9125 Truck crane). At the time of my depo, the crane configurations were not as complex (number of accessories) as nowadays, and capacity charts/notes could be “properly” placed in cabs visible to operators. As for a small plane, a 10 point placard to review at take-off would suffice – not today.

How do planes react to some elements such as loading, structural fatigue, gravity, and pilot errors? Just as a crane operator must react to these same topics in the 21st century, the second-decade era of technology. We are attempting to removing or “engineer out, human error” accidents involving these machines.

When a plane is heading down the runway to achieve flight speed, the pilot holds the nose down till airspeed is reached. He then raises the nose and becomes airborne. After lift-off, he lowers the nose to maintain airspeed by reducing drag, due to the take-off wing angle. Errors can be made during this critical take-off maneuver. So, a computerized back-up control system is installed to reduce the possibility of a pilot error – stalling the plane.

When a plane is on the ground, the fuselage is supporting the wings, when in the air the wings are holding up the entire air-machine. This changing force direction causes the wings to bend and flex (maybe 20 feet) that causes fatigue. The engine thrust creating this lift is in a continual battle with the gravitational pull of the earth.

A crane itself doesn’t become airborne (hopefully), but the load on the hook does. And when it does the structure of the boom can flex up to 20’, thus, increasing the operating radius overloading the crane. Some manufacturers install computers to automatically “Boom-up” to maintain the correct operating radius. And, engine torque is pulling the load from the earth’s gravity.

Programming automatic controls in modern planes and cranes, how is that done and more importantly, how do we verify that they are working properly? Well, this is where I discuss only cranes and leave the planes to the aircraft manufactures to figure out. As I see it, two methods are now in use “crane input or operator input.” First, crane input, there are mechanical sensors built in the crane that when energized, communicate to the computer as to how the crane is configured or put together, affecting the capacity. Operator input-errors can be: load weight, radius, parts of rope, length of luffing jib, outrigger/crawler extension, amount/extension of the counterweight, luffer mast off-set angle, angle of the live mast to boom angles limiting capacity, boom length, which hoist is used, and much more depending on the crane, more accessories, more chance for – operator error.

Modern cranes cabs have changed. An owner or user of such an automatically controlled crane must establish a test procedure to verify computer accuracy, which is usually beyond the standard Crane Certifier’s skills set.

As we venture into the era of automatic operating machines - planes, cranes, or even cars we wonder, how reliable are these machines? And what are the consequences of their “wrongness? Trustworthiness is established by design, maintenance, and performance testing. We don’t need to invent new methods for dependability. Elevators are automatic machines with unmatched performance. The quality and type of maintenance/testing on elevators are regulated by State licenses. Seems to be working.

DENNIS J. O’ROURKE, CSP, is the Director of National Crane Services, Inc. He has over fifty years’ experience in the industrial, maritime, and construction fields working with heavy equipment and material handling devices. As a safety engineer, Mr. O’Rourke has developed and/or presented over 300 safety-training programs for all representative elements of government and industry.

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