Post by benh on Feb 25, 2007 11:15:45 GMT
The Controlled Impact Demonstration (or more colloquially the Crash In the Desert) was a joint project between NASA's Dryden Flight Research Center and the Federal Aviation Administration (FAA) 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, forms antimisting kerosene (AMK). AMK had demonstrated the capability to inhibit ignition and flame propagation of the released fuel in simulated impact tests.
In addition to the AMK research the NASA Langley Research Center was involved in a structural loads measurement experiment which included having instrumented dummies filling the seats in the passenger compartment. Before the final flight on December 1, 1984, more than four years of effort passed trying to set-up final impact conditions considered survivable by the FAA.
AMK cannot be introduced directly into a gas turbine engine due to several possible problems such as clogging of filters. The AMK must be restored to almost Jet-A before being introduced into the engine for burning. This restoration is called "degradation" and was accomplished on the B-720 using a device called a "degrader". Each of the four Pratt & Whitney JT3C-7 engines had a "degrader" built and installed by General Electric (GE) to break down and return the AMK to near Jet-A quality.
Over a series of 14 flights, General Electric installed and tested four degraders (one on each engine); and the FAA refined AMK (blending, testing, and fueling a full size aircraft). During the flights the aircraft made approximately 69 approaches, to about 150 feet above the prepared crash site, under remote control. These flight were used to introduce AMK one step at a time into some of the fuel tanks and engines while monitoring the performance of the engines. During those same flights, NASA Dryden also developed the remote piloting techniques necessary for the B-720 to fly as a drone aircraft.
On the morning of December 1, 1984, a remotely controlled Boeing 720 transport took off from Edwards Air Force Base, California, made a left-hand departure and climbed to an altitude of 2300 feet. The aircraft was remotely flown by NASA research pilot Fitzhugh (Fitz) Fulton from the NASA Dryden Remotely Controlled Vehicle Facility. All fuel tanks were filled with a total of 76,000 pounds of AMK and all engines ran from start-up to impact (the flight time was 9 minutes) on the modified Jet-A. It then began a descent-to-landing to a specially prepared runway on the east side of Rogers Dry Lake. Final approach was along the roughly 3.8-degree glideslope. The landing gear was left retracted.
Passing the decision height of 150 feet above ground level (AGL), the aircraft was slightly to the right of the desired path. Just above that decision point at which the pilot was to execute a "go-around," there appeared to be enough altitude to maneuver back to the centerline of the runway. Data acquisition systems had been activated, and the aircraft was committed to impact. It contacted the ground, left wing low.
It was planned that the aircraft would land wings-level and exactly on the centerline during the CID, thus allowing the fuselage to remain intact as the wings were sliced open by eight posts cemented into the runway. The Boeing 720 landed askew and caused a cabin fire when burning fuel was able to enter the fuselage. The fire and smoke took over an hour to extinguish. The CID impact was spectacular with a large fireball enveloping and burning the B-720 aircraft. From the standpoint of AMK the test was a major set-back, but for NASA Langley, the data collected on crashworthiness was deemed successful and just as important.
VIDEOS
www.dfrc.nasa.gov/gallery/movie/CID/Medium/EM-0004-01.mpg
www.dfrc.nasa.gov/gallery/movie/CID/Medium/EM-0004-02.mpg
LINKS TO images
www.dfrc.nasa.gov/Gallery/Photo/CID/Small/index.html
