Ready for Take-off, Thanks to NIST's Million-Pound Deadweight Machine

The wings on an airliner, such as the Boeing 787 shown above, are subject to huge forces. But how do plane manufacturers know for sure how much force their wings will bear? They can measure them with sensors, but to ensure that these force sensors are working correctly they need periodic testing. So, airplane makers and other companies send their sensors to NIST to be measured using a unique instrument: The Million-Pound Deadweight Machine.

NIST’s Million-Pound Deadweight Machine is by far the largest in the world. It is more than 100 feet tall and contains three stories of shiny stainless steel weights, each one about 10 feet (3 meters) in diameter and weighing roughly 50,000 pounds. Together, the weights create up to one million pounds-force (in metric units, that’s 4.45 million newtons).

To test a company’s force sensor, NIST technicians hang the stack of weights off the device to either stretch or squish it. They know precisely how much force each steel disk produces. So, based on how many disks are hanging from the sensor, they can calculate how much force the company’s sensor should measure. If the sensor’s measurement is off, NIST gives the company a correction that they can use in their own laboratories.

Besides airplane makers, NIST’s Million-Pound Deadweight Machine is vital to the military as well as industries that need to measure large forces, such as oil and gas companies. Rocket and jet engine thrust measurements rely on the machine too.

After 50 years of service, NIST’s unique deadweight machine recently had a major makeover: a 16-month overhaul that involved taking it apart and making repairs, then carefully measuring the weights again and putting everything back together. The process involved massive air hammers, 30-ton cranes, screws the size of your head, and a balance so large that it was built into the ground. To watch videos of this unique event, visit the Million-Pound Makeover website.