Lesson 8: Global Engineering Practices

Metric vs Imperial Systems

The imperial system uses inches, feet, yards and miles. While most countries in the world have converted to the metric system, most have notable exceptions. Some maintain imperial terms (i.e. acre instead of hectare). Most international trade and manufacture is done using the metric system. Some countries, although officially metric, maintain use of both systems because of larger trading partners. This occurs in Canada where items are labeled using both metric and imperial units for easy export to Canada's top trading partner, the United States. However, the transition from one standard to the other has not always been smooth or without troubles.

One of the classic examples of trouble switching from one standard to the other is the Gimli Glider (see image below). A Boeing 767 flight from Montreal to Edmonton had a stop over in Ottawa. While in Ottawa one of the attendants checked the plane's fuel using the dripping method. He used the conversion rate of 1.77 pounds per liter in his calculations when he should have used 0.8 kilograms per liter. As a result the plane ran out of fuel at 41,000 feet and began to descend at the rate of over 2,000 feet per minute. Fortunately, one of the pilots remembered an abandoned air force base at Gimli, Manitoba. With only a single pass, the pilot glided the plane to a landing on the old runway now used as a drag race track. The only glitch was when the front wheels did not lock in place and collapsed. Other than a few minor injuries, everyone landed safe.