Reading_When Conversions Go Wrong

​When conversions go wrong....

https://www.nist.gov/pml/owm/metrication-errors-and-mishaps

Customary vs. SI units

Customary units are measurement units traditionally used in the United States, such as inches, feet, pounds, and gallons. These units are based on historical conventions and often require many different conversion factors.

SI units (International System of Units) are the globally standardized metric units, such as meters, kilograms, and liters. SI units are based on powers of ten, which makes conversions simpler and more consistent, especially in science and engineering.

Drag and Drop

Customary units include:​

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Drag these tiles and drop them in the correct blank above

feet

gallons

pounds

meters

liters

grams

NASA Mars Climate Orbiter

The National Aeronautics and Space Administration conducted a mission in 1998 to further explore Mars. In this mission, NASA and Lockheed Martin, its industrial partner, utilized both U.S. customary units and metric measures. NASA reported in the root cause investigation that a subcontractor did not properly account for changing the non-SI measurements in its software; consequently, the Mars Climate Orbiter crashed because it did not attain the proper orbit. This failed project, totaling $327.6 million in 1998, was unable to obtain intended data. NASA continues to struggle with dual measures, attributing challenges to U.S. aerospace sector reluctance to adopt the SI. The ongoing challenge was observed again in the 2010 internal inquiry related to the Constellation Project measurement practices.

Multiple Choice

What caused the Mars Climate Orbiter mission to fail?

• Engineers used meters instead of kilometers when calculating distance

• A subcontractor of Lockheed Martin did not account for both SI and non-SI measurements

• The spacecraft ran out of fuel due to a mass miscalculation

• The orbiter’s instruments were damaged during launch

Gimli Glider

In 1983, a Boeing 767 flight from Montreal to Winnipeg required an emergency landing because the plane was not properly fueled. Bob Pearson, the pilot of this flight, prevented disaster by safely landing at an airfield in Gimli. The staff of Air Canada recently began using the metric system instead of the customary system. Faulty unit conversions, compounded by other errors, caused the aircraft to be fueled with about 10,000 kg of fuel instead of the required 22,300 kg. Because of the pilot’s skillful landing, passengers arrived with minimal injury; however, this unit mix-up could have cost the lives of those on-board.

Multiple Choice

What was the primary mistake that led to the Gimli Glider incident?

• The fuel tanks were physically damaged before takeoff

• Fuel volume was measured instead of fuel mass

• The aircraft was fueled using pounds instead of kilograms

• The wrong type of jet fuel was used

Korean Air MD-11 Crash

In 1999, a Korean Air MD-11 crashed after takeoff from Shanghai on its way to Seoul. The flight crew was instructed to ascend to 1,500 meters. During ascent, the crew believed it had misinterpreted the request, believing the requested altitude to be 1,500 feet. This assumption was made because aviation altitudes are provided in feet throughout most of the world. During the flight correction, the crew lost control of the craft, resulting in a crash. This crash caused the loss of 8 lives and injured 37 others.

Multiple Choice

Which unit misunderstanding contributed to the Korean Air MD-11 crash?

• Confusion between kilometers and miles

• Confusion between meters and feet

• Confusion between liters and gallons

• Confusion between kilograms and pounds

House of Representatives Carbon Offset Purchase

In 2007, the United States House of Representatives sought to offset its carbon emissions. To achieve this, the House purchased carbon offsets from the Chicago Climate Exchange. From the Green Capitol Initiative Report, it was determined that 24,000 short tons of offset would be purchased; however, the chief administrative officer purchased 30,000 metric tons of offset. This amount was about 9,075 short tons more than the report’s determined amount. This excess offset cost the House an estimated $24,447.

Multiple Choice

What unit error occurred when the U.S. House of Representatives purchased carbon offsets?

• They confused metric tons with short tons

• They confused short tons with long tons

• They confused kilograms with metric tons

• They confused pounds with ounces

Open Ended

Suppose you are advising an organization on how to avoid costly unit conversion mistakes like the carbon offset error. What policy or training would you recommend and why?

Tokyo Disneyland Roller-Coaster Derailment

In 2003, Tokyo Disneyland’s Space Mountain roller-coaster derailed because of a part specification error. In 1995, the design drawings were converted to metric and marginally adjusted. Both the original customary drawings and the metric drawings were maintained. When parts were ordered for the Space Mountain coaster, the original drawings were accidentally used; the ordered axles were 44.14 mm instead of the updated 45 mm. This error caused the axle to excessively vibrate and eventually break. Although individuals were not injured in this incident, Tokyo Disneyland suffered immense reputational damage.

Multiple Choice

What type of unit error caused the Space Mountain derailment at Tokyo Disneyland?

• Temperature units were misread during maintenance

• The ride’s mass limits were calculated incorrectly

• A safety inspection used the wrong speed units

• A component was manufactured using inches instead of millimeters