A long-time resident of the Mojave retirement community has passed away. Annie was
an unusual, somewhat storied Boeing 720-060B that contributed crucial data to the science
of infrared imaging. Carrying the name of Embraceable Annie on her nose, N7381 was
a flying testbed for the Airborne Infrared Measurement System (or AIRMS).
serial number 18977/442, was delivered on September 20, 1965 to Ethiopian Airlines as
ET-ABP (for a photo of her in Ethiopian colors by Kjell Nilsson, jump to http://www.airliners.net/open.file/395449/L/
). Ethiopian leased her to Middle East Airlines from 1966 until 1968.
This Boeing, like many other citizens of that part of the world, fell victim to
violence in 1972, suffering damage from an exploding grenade during a hijacking attempt.
On December 8, seven hijackers attempted to take over the aircraft at Addis Ababa. Upon
announcing the hijacking, security guards opened fire, and in the ensuing firefight six of
the seven hijackers were killed. An American passenger on board the aircraft, Roderick
Hilsinger, was instrumental in foiling the hijacking. Hilsinger was a well-known college
professor from Temple University, and onboard that Ethiopian Airlines flight that day, he
found himself in the middle of hell. When a hand grenade rolled across the floor, he
reached out, picked it up and tossed it into a section of unoccupied seats, where it
detonated. Though he was seriously injured with shrapnel wounds to his head, shoulder and
ankles, he was credited with saving a hundred lives, those who would have died if the
grenade had gone off where it rested. "Anyone would have done the same thing if they
saw a hand grenade two feet from your foot," Hilsinger said at the time. Apparently
others did not agree with such a humble attitude, and the next year, he was awarded a
commendation by President Nixon for "his uncommon valor and heroism." (Hilsinger
died in 2000 of cancer; click here
to read his obituary).
By 1988, Annie was sitting, still in Ethiopian
colors but registerd as N440DS, at Pinal Airpark in Marana, Arizona, with an uncertain
future (for a photo of her at Marana by Frank Schaefer, jump to http://www.airliners.net/openfile/294284/L/
). Ive yet to uncover how or why the aircraft was selected for the AIRMS program,
but it took two years to rebuild Annie at the Lockheed facility in Greenville, SC.
The aircraft was then flown to Van Nuys, California, where the imaging systems were
installed. David Jones oversaw the entire process, and later served as the Flight Engineer
onboard, and it was he that named N7381 Embraceable Annie, as a tribute to his
wife. The aircraft was reregistered N7381 at this point.
the completion of the test program, the aircraft came to Mojave sometime in 1998, and
ended up in the Aviation Warehouse yard. Mark Thompson, owner of Aviation Warehouse, is a
leading supplier of aircraft and components to the movie and television production
industry for use as sets and props.
The end came unexpectedly on October 17, when the crew from Alameda Metals, one
of Mojaves aircraft metals recycling companies, began breaking the aircraft up for
scrap. I first saw Annie mid-morning that day from across the field, decapitated and
sitting back on her tail. Julio, the talented operator of the Hitachi claw had
most of the fuselage reduced to shreds by later in the afternoon when I was able to make
it over there. The entire canopy was gone, and he was in the process of breaking the keel
behind the wing center section area. After shooting his work for a while, I got to talking
with him. The cockpit section had been cut off and was laying askew, to be saved, along
with the engines, by Thompson for movie use.
The AIRMS Program
is a system developed by Raytheon and the Hughes Aircraft Company for the Defense Advanced
Research Projects Agencys Sensor technology Office (aka DARPA STO) to enable the
detection, through infrared imaging, identification and engagement of targets (both
ground-based and airborne threat vehicles such as aircraft and cruise missles) at ranges
greater than 250 miles from an airborne platform operating at altitudes between 15,000 and
42,000 feet. The AIRMS stretched the envelope in the science of infrared imaging, and led
to a number of important developments in the realm of infrared search and track, or IRSAT.
The sensor itself, with an aperture of 24 inches, was much larger than any which had been
flown before, and required a high degree of stability, as it was so sensitive and
collected such high-resolution data.
of the main goals of the AIRMS program as flown on Embraceable Annie was to collect
a database of imagery to be used to develop and validate target detection and
clutter rejection algorithms (Bender, 1995). In other words, to be able to detect
the IR signature of a target at a great distance, you need to be able to filter the real
target out of all the background cloud and clutter data. The data collected by Annie
was then examined in regards to its IR phenomenology and the results of this study were
then used to develop and validate target detection and clutter rejection algorithms, to be
used in the development of future tactical IR sensors.
The program resulted in the development of a
Distributed Algorithm Stream, or DAS, which is described by project
researcher Dr. Joseph Attili as a full-up end-to-end space-time processing stream
that takes in raw sensor data and generates tracks of moving targets. uch a
highly complex computer algorithm required the high-end computing power of an Intel
Paragon Supercomputer to run on. (For more on the ground-breaking science that came out of
the program, see Dr. Attilis website at http://home.att.net/jattili/airms.html )
A number of defense contractors were involved in the project. As noted
above, Lockheed prepared the aircraft to receive the systems needed to support the AIRMS
Aircraft Technical Service Engineering (ATS Engineering) of Van Nuys was
contracted to build and install much of the aircraft-side hardware that made the AIRMS
program possible (photos and diagrams of the ATS-designed systems are available on
ATS website at http://www.atsengineering.com/
b720.htm ). They designed and built a 12 x 12 unpressurized enclosure in
the normally-pressurized forward cabin of the aircraft, using a set of beefy pressure
bulkheads. The floor bulkhead was greatly reinforced so that the aircraft pressurization,
which in a normal aircraft causes a certain amount of airframe flexing and stretch, would
deflect the floor less than 1/10th of an inch. This was necessary because the
sensors, looking out over such great distances, are very susceptible to any movement.
Rigidity of their mount was paramount. As thick and rigid as these structures were,
however, they were no match for Alamedas Hitatchi claw.
They also built a 8 x 6 opening in the left side of the aircraft
though which the infrared sensor would look out on the world. The design of the
Aerowindow had to be carefully engineered to minimize turbulence at various
aircraft angles of attack. Turbulent airflow in the vicinity of the infrared sensor would
reduce its ability to resolve images as such great distances. ATS based their design of
the Aerowindow on a concept developed by NASA for the Strategic Observatory for Infrared
Astronomy (SOFIA). When the sensor was not being used, the Aerowindow was closed by means
of a door they called the eyelid.
ATS also designed a liquid nitrogen-based cooling system for the enclosure that
pre-cooled the sensitive infrared sensor equipment in order to prevent thermal shock when
the eyelid was opened at altitude. The system utilized two 300-gallon dewar flasks of
liquid nitrogen mounted in the cabin aft of the wings. Before flight, the unpressurized
area was purged with dry nitrogen, and then cooled to the expected temperature at altitude
by liquid nitrogen.
Hughes developed the sensor systems and maintained the aircraft throughout the
flight test program. They also provided crews that operated the sensor systems during
flight. The USAF Flight Test Center at Edwards AFB provided the flight crews and the
mission planning support services. Besides the USAF cockpit crew, the personnel onboard
included a system operator, a gimbal operator and a test director. Seats for up to ten
observers were also provided in the cabin.
The program flew 51 flights during a 23 month period, from the first
flight-worthiness sortie in November 1993 to the last, which observed the induced wakes of
a sea skimmer in October, 1995. The flights collected over one terabyte of data on a
variety of targets, such as aircraft parked on the Edwards ramp, cruise and tactical
missile launches as well as a lot of data on clouds and background clutter such as ocean
waves, airfields, nuclear power plants and harbors
the AIRMS program, and Embraceable Annie went a long ways towards improving this
country's ability to detect and track moving targets by infrared means as great distances,
and it supremely ironic that an aircraft which had been the victim of terrorism was later
to serve such a vital role in the development of tactical tools to fight global
A copy of the booklet ARPA Airborne Infrared Measurement System produced
by Hughes and containing the text of a paper detailing the project presented by Paul A.
Bender, Jr. at the 1995 National Infrared Information Symposium, Applied Physics
Laboratory/JHU Laurel, MD on 12 July 1995 has been donated to the Mojave Transportation
Museums library, and was the source of much of the information presented here. The
Museum was able to salvage one of the N numbers and the right front cabin door for
For more information and photo's of the scrapping of Annie, jump to Alan's Mojave Weblog.