5 Real Life Cases Where a Unit Conversion Error Caused Serious Problems

Unit conversion errors may seem innocuous, but they can have significant real-world consequences, as they lie at the intersection of precision and understanding. Missteps in the process of unit conversion have led to serious mistakes in a variety of fields, resulting in monetary loss, project failure, and even potential safety risks. The following examples, from space missions to aircraft incidents and law enforcement errors, highlight the critical importance and far-reaching implications of precise unit conversion in various domains.

The Mars Climate Orbiter Incident

In 1999, a mix-up between metric and imperial units led to the loss of NASA's Mars Climate Orbiter. The spacecraft was designed to study the Martian climate and atmosphere, but it disintegrated in Mars' atmosphere upon arrival. The root of the issue lay in a navigational command that was computed in pound-seconds (imperial), while the spacecraft's systems expected the command to be in newton-seconds (metric). This unit conversion error led to a loss of around $327.6 million.

The Gimli Glider Incident

The Gimli Glider is the nickname of an Air Canada aircraft that ran out of fuel mid-flight due to a unit conversion error in 1983. The plane's fuel gauges were inoperative, so the crew had to manually calculate the required fuel in kilograms. However, they mistakenly did this calculation in pounds, resulting in the plane receiving only about half the necessary fuel. Fortunately, the pilot managed to land the plane safely without any casualties.

The LA Police's Traffic Software Issue

In 1986, the Los Angeles Police Department's automated traffic software mistakenly issued tickets to drivers who were not violating any speed limits. This error resulted from a unit conversion mistake in the software. The speed limits were entered into the system in kilometers per hour, while the speeds of vehicles were measured in miles per hour. This led to countless drivers receiving unfair tickets.

The Hubble Space Telescope Misalignment

The Hubble Space Telescope, launched in 1990, initially returned blurry images due to a flaw in its main mirror. The problem was traced back to a unit conversion error: the device used to manufacture the mirror was calibrated in inches, while the design of the mirror was done in metric units. The error resulted in a costly and complicated repair mission to install corrective optics, restoring the telescope's capabilities.

The Conversion Error in the USS Yorktown

In 1997, the USS Yorktown, an American guided-missile cruiser, was left dead in the water for nearly three hours due to a unit conversion error. A crew member entered a zero into a database field that expected a numerical value in a specific range, and the software attempted to divide by this zero. The resultant system failure shut down the ship's propulsion system, illustrating how even small unit conversion errors can have substantial real-world consequences.