Video: When NASA crashed a Boeing 720 on purpose to test a fire-fighting additive

In 1984, the Dryden Flight Research Center of the POT and the United States Federal Aviation Administration, FAA for its acronym in English, carried out a test to test a fuel additive with the ability, demonstrated in simulated tests, to retard or suppress fire in the event of an aircraft accident. But to verify the effectiveness of the additive FM-9a high molecular weight polymer, when mixed with standard Jet-A fuel, was necessary reproduce a real airplane emergency landing scenario. And that is what they carried out on December 1 in the Mojave Desert, California. The test was called Controlled Impact Demonstration.

a passenger plane Boeing 720 four-engine, which had been in service for 24 years, was selected for the test. This is a smaller version of the 707 which Boeing developed for shorter flights. Can transport 124 passengers and has a wingspan of 39 meters, a length of 41 and a height of 12 m. The aircraft would be piloted remote form in the test and several steel structures were placed in Rogers Dry Lake, at Edwards Air Force Base, to break the fuel tanks on the wing when landing.

The use of the FM-9 additive presented a problem. Once combined with fuel, the result was an anti-fogging kerosene that could clog engine filters. To avoid this, it was installed in each of the four engines Pratt & Whitney JT3C-7 from the aircraft a device called degrader which restored the modified fuel to Jet-A standard, before being introduced into the engine for combustion.

Boeing 720 used in the test. POT.

In addition to testing the effectiveness of the FM-9, the Controlled Impact Demonstration had as objectives evaluate the structural integrity of the aircraft during landing, for which dummies with sensors were placed in the passenger seats and in the cabin, new seat designs, fire-retardant cabin materials and fire-resistant windows.

Before the final flight in 1984, it took 4 years of preparation in which Dryden developed the remote piloting techniques necessary for the Boeing 720 to fly without a crew on board; General Electric installed and tested the degraders for each engine; and the FAA refined the fuel with the anti-fogging additive FM-9.

They were carried out 14 preliminary flights to gradually introduce the modified fuel into the fuel tanks and engines while monitoring the performance of the latter. During the 14 flights, carried out with safety pilots on board, the Boeing 720 was remotely controlled by another pilot from the ground for 16 hours and 22 minutes, including 10 takeoffs, 69 controlled landing approaches and 13 landings.

The Boeing 720 made contact with the ground with its left wing.
The Boeing 720 made contact with the ground with its left wing.POT.

In the morning of December 1, 1984, the Boeing 720 took off from Edwards on the fifteenth and final flight of the program. The plane's tanks were filled with 42,000 liters of modified Jet-A fuel and all engines operated normally from startup to impact during the the flight lasted nine minutes.

Piloted by NASA research pilot Fitzhugh Fulton from NASA's Dryden Remotely Controlled Vehicle Facility, the plane climbed to an altitude of 700 meters. The flight plan called for the aircraft to land with landing gear retracted on a specially prepared runway, with the wings level and exactly on the center line, allowing the fuselage remained intact while the wings were cut by eight steel posts.

The Boeing 720 began the descent, but when it was below 45 meters of altitude it was slightly to the right of the desired trajectory. His left wing was the first to make contact with the ground., before reaching the wing cutters. This caused the plane's nose to move to the left as it slid over the runway at an angle of approximately 45 degrees.

As a result, one of the wing cutters hit the internal engine in the right wing, destroying it and causing a large fuel leak that immediately burst into flames. The plane continued to roll to the left until it was almost on its side, causing the damaged right wing to break off and fold over the fuselage, which was engulfed by a large fuel-fueled fireball. It took more than an hour for the fire to be completely extinguished.

The Boeing 720 on fire after landing.
The Boeing 720 on fire after landing. POT.

The demonstration highlighted an often overlooked aspect of aeronautical research. Although small-scale ground tests had indicated that the anti-fogging additive would be effective in reducing post-accident fires, Full-scale demonstration in a real flight environment showed that the modified fuel was ineffective to reduce the spread or intensity of fire.

Despite this result, many useful safety-related data were obtained during the Controlled Impact Demonstration. Cameras inside the plane showed the test dummies shaking violently and panels and other interior parts falling during the emergency landing, although the seats remained strapped to the floor. New seat designs, flight data recorders, fire-retardant materials and fire-resistant windows were tested in real-world conditions. Research data obtained in these areas helped establish new FAA standards on fire prevention and fire retardant materials.