Enhanced Vision Systems

Infrared sensors improve aviation safety


It was a dark and stormy night. The moon was obscured by low-lying clouds resembling mountainous peaks while a combination of mist and fog blanketed the hilly terrain. All a sudden, without warning, a shot rang out. All the while a private aircraft approached the nearby private runway. A well-versed captain and an eager but not nearly as qualified co-pilot comprised the cockpit crew and the flight deck they operated consisted of 1980’s vintage electronic flight instruments with some later technology enhancements.

The crew appeared unconcerned and even complacent about the current situation as they had flown this approach into the boss’s ranch on a regular basis. It had, so far, been an uneventful flight, but as usual the boss had been running late which of course delayed the departure, and meant arrival time would be well after sunset. As the crew sat listening to the drone of the twin turbines they contemplated the approach and landing.

The ranch runway, although still private, recently underwent a major refurbishment including improved approaches so the weather was more of a nuisance than a limitation to landing. At about 350 feet above ground level the aircraft broke out of the clouds and the crew made visual contact with the end of the runway. Unfortunately the combined effects of mist, fog, and darkness obscured the second half of the runway. The current situation did not alarm the occupant of the left seat as he knew the landing field better than anyone and had complete confidence in the stopping power of his aircraft.

The runway lights had been activated and sliced through the darkness enabling the crew to align the descending machine with the center line of the runway. Landing gear had been extended and verified down and locked, full flaps had just been selected and the final approach thrust settings were made. Touchdown occurred as planned and the throttles were set to idle in anticipation of deploying the thrust reversers. As the piggy back levers were pulled the crew observed the normal illumination of the in transit lights followed by the green deploy indication. Just as the request for an increase in reverse thrust was made, the co-pilot spotted several deer about two-thirds of the way down the runway. There wasn’t time to stop the aircraft nor was there time to stow the thrust reversers and get the engines spooled back up to enable a go around.

During the unplanned barbeque the next day, the chief of maintenance had taken some time away from repairing the impact damage to the aircraft and was talking with the ranch foreman who previously had been a career military intelligence gatherer. The discussion of course revolved around the recent events and how future situations could be avoided. During the conversation military surveillance techniques were reviewed including how “heat seeking” technology could easily unmask hidden targets. In fact, the comment was made: “You’d think they’d have something like that for aircraft”. Well in fact they do!

Infrared Radiation

Infrared radiation was first detected in 1800 by Sir William Herschel, who was attempting to associate heat with the visible light spectrum. These early studies proved that heat will radiate out from any object whose temperature is slightly above absolute zero. In fact absolute zero is -459.67 F and heat radiation will begin at -441.67 F and each degree has its own unique and predictable radiation pattern. Infrared means “below red” and in this case it is below the visible light spectrum producing a lower frequency and a longer wavelength. As it is not detectable to the human eye and is thereby not associated with sight, infrared radiation is referred to as thermal or heat radiation.

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