In 1984 NASA Dryden Flight Research Center and the Federal Aviation Administration (FAA) teamed-up in a unique flight experiment called the Controlled Impact Demonstration (CID), to test the impact of a Boeing 720 aircraft using standard fuel with an additive designed to suppress fire. The additive FM-9, a high molecular-weight long chain polymer, when blended with Jet-A fuel had demonstrated the capability to inhibit ignition and flame propagation of the released fuel in simulated impact tests.

See: http://www.dfrc.nasa.gov/Gallery/Photo/CID/index.html

One of the objectives of this CID (Controlled Impact Demonstration) was to demonstrate that the AMK (Anti-misting-kerosene) additive to the fuel would significantly degrade a post crash fire from ruptured fuel tanks (see attachment PW-1 )

There have been numerous accidents involving fatalities to passengers where fire or smoke inhalation occurred with the aircraft stopped on the ground. Such accidents typically involve ruptured fuel tanks caused by either punctures from engine debris or off runway excursions by the aircraft (e.g. unsuccessful takeoff aborts) It was postulated that the addition of an AMK additive to the fuel would substantially inert the spilled fuel except for leakage from aft of the pumps attached directly to the engine pylons. While some ignition and burning was anticipated due to small amounts of leakage from the engines as well as some degree of misting itself from leakage into a turbulent airstream, the end result was expected to be no more than a flash, or non persistent fire.

The subject CID test attempted to recreate a typical crash impact that was survivable under G-loading by the passengers and seat structure while at the same time ensuring that fuel tank ruptures and a persistent ignition source (tail mounted rocket) were also present to evaluate the degree of fire in an aircraft runway excursion.

A B720 aircraft was used fuel by AMK and the aircraft was to be flown remotely so as to touchdown on a runway heading (without gear down) and to intersect steel cutter blades that would rip the fuel tanks open with attendant fuel spillage in turbulent flow conditions.

All went reasonably well until the actual touchdown, which occurred with a significant crab angle. While the touchdown was within the G levels expected, the uniqueness of the steel cutter blades to this crab angle resulted in a significantly altered an unrepresentative test condition, which resulted in an uncontrolled fire. There are arguments that the test conditions were as expected variations in a crash and therefore representative in the outcome. More discussion on this later. There were also arguments that the fire was controlled compared to non AMK additive fuel. In the latter argument we should consider the final outcome. See figs cap005.jpg and cap004.jpg.

The one figure shows that the aircraft has been substantially burnt out from at least an internal fire, while the other figure shows the condition of the dummy occupants.

So let us examine the conditions that were unexpected and contributed to this outcome.

The NASA web site shows several overall high quality photos of the sequence as follows:

Touchdown with left wing down (fig. ECN-31803.jpg)

The side skew then occurs which brings it into the cutters at a significant angle (fig.
EC84-31805.jpg)

Then cutters do their job + fuel spill + ignition (fig. EC84-31806)

The persistence and intensity of the fire is shown in Figs. EC84-31809 & ECN-31808)

In the movie views provided by NASA we can begin to see the uniqueness of the demonstration as it develops.

Fig. Cap062.jpg shows the touchdown on the left wing that squashes those engines and begins the skew to the left.

Fig. Cap001.jpg shows the forward vector of the aircraft is developing askew to the fuselage and engines. In this figure the cutters are aligned to intersect engine pos 3.

Fig Cap065.jpg shows that the fire initiates in the #3 engine position

When we examine in detail a series of photos taken from movie that show the #3 engine position we can then see how and why the intense fire initiates. (See figs cap030c-p)

The best way to view this sequence of photos is to insert them into PowerPoint presentation and to rapidly step through them.

By doing this you can see that one of the cutters enters the # 3 engine behind the low speed compressor spool and at the front of the high speed compressor spool. The cutter severs into the compressor disks causing the high spool to seize to a stop while at the same time severing the torque box between the front and rear mounts. The front of the engine is then seen to rotate clockwise (looking forward) while shearing its mounts and the aft torque link mounts shear shortly afterwards and are seen falling away silhouetted by the flame.

This extremely robust cutter continued severing through the engine and as it reached the inboard side of the engine it severed the fuel feed to the engine aft of the aerator pump, Thus releasing fully atomized (for burning in the engine) fuel into the turbulent air-stream caused by the skewed motion of the aircraft. The cutter than continued sideways into the cargo hold of the aircraft flowed by fully atomized burning fuel. The interior shots taken inside the aircraft while still in motion show the explosion of this fuel up through the floorboard vents alongside the occupants. The continued motion of the aircraft with atomized fuel spewing into the cargo hold doomed the aircraft. See fig. Cap002.jpg for a view of an uncontained rotor part from # 3 engine.

While the skewing of the aircraft, as it slid out is not unique to the numerous survivable accidents that could be improved by the use of AMK fuel, the robustness of the steel cutter that was able to slice completely through a running engine behind the inlet is historically unique to all other accidents since the advent of commercial jets. While this I itself is only a small unique items among many variations, it was critical to the outcome of this demonstration only because it uniquely defeated the AMK by causing a massive leak aft of the engine pump.
 

Video of the Test can be seen by clicking the three pictures below