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1st of December 1984

Updated: Dec 2, 2021

The subject of today's aviation blog, a Boeing 720 was originally ordered by Braniff Airways Inc. as plain passenger aircraft, but they never took delivery of the aircraft. The Boeing 720 made its first flight on the 5th of May 1961 and was delivered as a test aircraft to the FAA a week later. In 1982 NASA took delivery of the aircraft so it could play the lead role in a dramatic landing test on this day in 1984, registered as N8333NA.

N8333NA digging its wing into the desert floor of Rogers Dry Lake (© NASA)

In 1984 NASA and the FAA finalised 4 years of preparations for a controlled crash landing of the Boeing 720.

The purpose was to demonstrate the effectiveness of a promising fuel additive that would suppress fuel-fed fire in the event of a crash landing. The additive called FM-9, mixed with Jet-A fuel had already demonstrated its effectiveness in simulated impact tests. The Jet-A and FM-9 mixture could not be directly fed into the JT3C-7 engines of the Boeing 720 as it would clog up the filters. Each engine was therefore equipped with a device called a degraded, which restore the fuel to near Jet-A standard.

To make the most of this test the cabin was fitted out with load measuring equipment and also 40 crash test dummies fitted with sensors to measure forces exerted on the dummies during the crash landing. The dummies were seated in newly designed seats that would also improve survivability. Other adaptions for the crashlanding included special and additional flight data recorders, fireproof cabin materials and fire-resistant cabin windows.

Prior to the crash test flight, 14 trial flights were flown with safety pilots on board to prove the reliability of the remote control system. During these test flights, the aircraft was controlled by Test Pilot Fits Fulton from a ground-based console. During the test flights, a total of 16 hours and 22 minutes of flight time were recorded. In this time, 10 take-offs and 69 approaches were made, as well as several successful landings.

Just before the scheduled touchdown point the left wing dipped and dug into the desert floor. This caused the aircraft to yaw to the left as it slid sideways over the desert floor. Only one cutter hit the aircraft, at the #3 engine, causing a fuel leak that immediately burst into flame. The yaw to the left increased so far that the aircraft was nearly moving sideways. The right-wing broke off and a massive RH engine fuel fed fire (©NASA) fuel-fed fire

engulfed the fuselage.

The intensity of the fire proved without a doubt that, although smaller (lab) tests showed the effectiveness of the additive, this fulls scale test proved its ineffectiveness in a real crash. Further development and test of the additive were cancelled. RH wing breaking off (© NASA)

Although the main test purpose of this crash test was considered a failure, cameras inside the airliner showed the crash dummies being shaken and small panels falling during the crash-landing, although the seats remained attached to the floor. The new seat designs, flight data recorders, galley and stowage-bin attachments, fireproof materials and windows were tested under real-world conditions. Research data from the project in these areas yielded new data on impact survivability that helped the FAA establish new rules regarding fire prevention and fire-retardant materials. The estimated $5 to $7 million over the course of four years for the project were not totally wasted, thanks to the test of safety improvements tested in the cabin. Several video's of the test can be found on youtube, we have included one for you here;

All pictures and video © NASA

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