The Adventure of the Loose Screws

DN Staff

August 26, 2009

4 Min Read
The Adventure of the Loose Screws

By Chuck Maggi, Contributing Writer

A laser guided alignment procedure is anything but in alignment, and the optical boys are starting to sweat.

Many years ago I worked as a lead engineer for a large aircraft simulator company. We designed flight simulators for every aircraft known to man including many with motion platforms. These motion platforms included the real cockpit of the aircraft along with visual simulations of the outside environment. These somewhat large simulators were assembled and debugged in a large high bay area at the company headquarters. There were many motion cockpits on the floor with full visual display capability at all times. Times were good and everyone enjoyed the exciting work - especially since you could fly the fruits of your own labor. What a thrill to fly your own 747 with full visual and motion simulation.

We won a contract to produce the visual simulation of a large spacecraft experiment. The award was good news for us until we heard that we had to produce the entire system in 10 months. The job entailed simulation of the controls and the visual response to the astronauts. To accomplish this feat, large optical benches were required to house the optics and the servos needed to perform all of the effects of the controls for these onboard experiments.

We needed extreme stability for the optical benches that would house many lens assemblies. So we purchased several large granite benches, 10 inches thick by 2 feet wide and 5 to 8 feet long from a tombstone manufacturer. There were 6 such benches needed to simulate the 6 experiments on board. I never thought about the weight of each bench but it must have been great. These “tombstones” were held up by a gantry of reinforced steel legs. We figured that absolutely nothing could move the optics if we used these monsters. Little did we know, we were about to be proved wrong.

The time was short for delivery of the entire system so the optical boys began their laser guided alignment procedure. They would start in the middle of a bench with the optical assemblies and work their way towards the ends. Every evening they would go home admiring the good work that they accomplished for the day. Every morning they would come in and find that their alignment was totally out of whack. This went on for many days with ever increasing frustration. They thought that they had a problem and never raised the issue to me until several days later.

The issue was presented to the entire design team and the analysis began on temperature coefficients of every part of the optical bench - including the granite. Every conceivable idea was presented and analyzed to excruciating detail. After several days of analysis with no solutions in hand, I had decided that something beyond our imagination must be happening. So I requested that a night guard position himself inside one of the cockpits of an adjacent simulator for the entire night - watching our area for any suspicious activity. The next morning I had the problem solved.

The night guard reported to me that he saw no suspicious characters and the only thing he observed was a group of men who entered the area for several hours that night and then left. After I enquired with upper management, they informed me that the quality control department was working the night shift. They were doing the graveyard shift as a courtesy so that they would not get into our way and be detrimental to our tight schedule. I then inquired with the head of that department and discovered their procedure. Every night they would enter our area to perform the required inspections of all components to ensure compliance with the contract. I then talked with the group for specifics and was told that they had to verify ALL of the hardware that was being delivered. They stated that they would remove the screws on the optical assemblies and verify that they were of the specified size, length, and type. They would then replace them neatly back where they were originally so as to not disturb our work. Of course, they would tighten them to the specified torque so no one would know they were removed.

Contributing Writer Chuck Maggi earned his BSEE from PSU in 1967. A self-proclaimed “old and tired electrical engineer,” he has worked in oil fields, aerospace, communications, consulting, spooking, and now into asphalt and viscosity in my waning years. He is now back into the exciting world of amateur radio after a 40 year hiatus as N3CRM.

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