The Ejection Site

ACES II 600 KEAS Test at HMTF

Video by Kevin Coyne

The SAFE association was once again invited to Hurricane Mesa for a sled run following their symposium and I was lucky enough to receive an invitation. This year there were some weather delays but when the shot finally fired it was worth the worry. An F-15 ACES II with certain modifications being considered for USAF use was launched from the sled at a speed in excess of 700 miles per hour. The manikin used this year was the Lowest Occupant In the Service (LOIS) manikin with a nude weight of 103-116lbs depending on configuration of the data channels and ballast. The dummy was outfitted with current issue flight gear and was strapped into the ACES II as a normal pilot would be.

The sled used was the same one used in test 781 last year however it was fitted with two sets of rails set with the appropriate spacing and angles for F-15 seats. The seat was located in the forward set of rails. Two pusher sleds and the main sled had on the order of 100 rockets for thrust intended to push the sled to a velocity in the 600KEAS range and the target velocity was achieved within a very small tolerance. Seat ejection appeared to be within limits and with the landing speed of the dummy looked survivable. Due to concerns of the USAF I was not permitted to photograph the test equipment after the test, but was able to shoot video and stills during the run. The above video shows the sled run in realtime and you can click below to view a slowed down version of the same footage. I shot a Canon Digital Rebel with a shutter speed of 1/1250 and the lens focused manually on the track prior to the shot. The video was shot with a Canon A75 camera mounted co-axially to the Digital Rebel on a special camera rig. I also shot video using a Sony camcorder however due to the high zoom I tried to use the footage is not satisfactory for use.

The above view is clipped from the video and shows the seat boosting out of the sled. The sled is nearly supersonic and has developed a visible shock cone where the airflow over the sled is going from high pressure in front to low pressure behind, condensing the water in the air into a fog that encircles the sled. The picture of the sled taken at top speed showing the seat emerging also shows a similar effect of low pressure air streaming off the top of the seat and spiraling about ten feet behind it.

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