Narrative:

A near miss occurred at approximately XA10 local time on apr/mon/96 at approximately 12500 ft in VMC conditions approximately 45 NM due south of stl between a F15S and a twin engine propeller driven aircraft, possibly a cessna, piper or beech. Avoidance was taken by the F15. Other aircraft did not appear to have taken any evasive action. Nearest distance was approximately 500 ft. F15S aircraft piloted by a civilian production test pilot and a military pilot, on a production support test flight and instrument chkflt. This aircraft is used for production support and target work and is based at stl. Situation: as we were heading north, climbing towards 12500 ft, which is the agreed upon return altitude (per LOA) to return to st louis from the south operating area, as we leveled out, I noticed a motionless spot on the upper right corner of the HUD. I did a momentary double take and realized that it was a twin engine propeller aircraft heading towards us. Realizing that we were on a near collision course, I rolled rapidly to approximately 135 degree left bank, and pulled the stick rapidly aft to generate separation. I estimate that the minimum separation may have been about 500 ft, although the geometry caused me to lose sight in the pull. After I rolled out, we saw the other aircraft continuing south in wings level flight. We asked ZKC, who usually provides us with TA's, if they had seen a civil aircraft pass us. They said that they had, but didn't have any altitude information on him, but that he was on a climb to 14000 ft. Although we have a preferred recovery altitude of 12500 ft into our northbound south recovery corridor, I have often felt that a better recovery profile would have us proceed inbound at 8500 ft (at least if we were initially below 10000 ft), rather than climb upwards through occasional northbound arrival traffic which is normally at 10000 ft on the qball arrival. Although the other aircraft was headed sbound, sbound traffic is rather infrequent in this area. Human factors: it is an interesting note, that when on a collision course, there is no angular movement of the opposing aircraft which tends to make it appear motionless, with only barely perceptible size growth. During the time of my double take, it seemed as if it was in slow motion and that there was very little perception of impending conflict. Of course, the combined speeds were quite high as we were at about 280-300 kcas and I estimate that the other aircraft was at perhaps 150 kcas for a combined closing of 450 kcas (a true closing speed of 500 KTS), which would be roughly 850 ft per second. Little time remains to spot a fairly small object head-on, especially when it has no angular relative motion to aid recognition. If we had taken no evasive action, I estimate that we would have passed within 50 ft. If I had made a pure pullup, we could have made the situation worse.

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Original NASA ASRS Text

Title: AN F15S FLC CONSISTING OF A CIVILIAN PRODUCTION TEST PLT AND A MIL PLT HAS AN NMAC WITH A TWIN ENGED PROP ACFT.

Narrative: A NEAR MISS OCCURRED AT APPROX XA10 LCL TIME ON APR/MON/96 AT APPROX 12500 FT IN VMC CONDITIONS APPROX 45 NM DUE S OF STL BTWN A F15S AND A TWIN ENG PROP DRIVEN ACFT, POSSIBLY A CESSNA, PIPER OR BEECH. AVOIDANCE WAS TAKEN BY THE F15. OTHER ACFT DID NOT APPEAR TO HAVE TAKEN ANY EVASIVE ACTION. NEAREST DISTANCE WAS APPROX 500 FT. F15S ACFT PILOTED BY A CIVILIAN PRODUCTION TEST PLT AND A MIL PLT, ON A PRODUCTION SUPPORT TEST FLT AND INST CHKFLT. THIS ACFT IS USED FOR PRODUCTION SUPPORT AND TARGET WORK AND IS BASED AT STL. SIT: AS WE WERE HDG N, CLBING TOWARDS 12500 FT, WHICH IS THE AGREED UPON RETURN ALT (PER LOA) TO RETURN TO ST LOUIS FROM THE S OPERATING AREA, AS WE LEVELED OUT, I NOTICED A MOTIONLESS SPOT ON THE UPPER R CORNER OF THE HUD. I DID A MOMENTARY DOUBLE TAKE AND REALIZED THAT IT WAS A TWIN ENG PROP ACFT HDG TOWARDS US. REALIZING THAT WE WERE ON A NEAR COLLISION COURSE, I ROLLED RAPIDLY TO APPROX 135 DEG L BANK, AND PULLED THE STICK RAPIDLY AFT TO GENERATE SEPARATION. I ESTIMATE THAT THE MINIMUM SEPARATION MAY HAVE BEEN ABOUT 500 FT, ALTHOUGH THE GEOMETRY CAUSED ME TO LOSE SIGHT IN THE PULL. AFTER I ROLLED OUT, WE SAW THE OTHER ACFT CONTINUING S IN WINGS LEVEL FLT. WE ASKED ZKC, WHO USUALLY PROVIDES US WITH TA'S, IF THEY HAD SEEN A CIVIL ACFT PASS US. THEY SAID THAT THEY HAD, BUT DIDN'T HAVE ANY ALT INFO ON HIM, BUT THAT HE WAS ON A CLB TO 14000 FT. ALTHOUGH WE HAVE A PREFERRED RECOVERY ALT OF 12500 FT INTO OUR NBOUND S RECOVERY CORRIDOR, I HAVE OFTEN FELT THAT A BETTER RECOVERY PROFILE WOULD HAVE US PROCEED INBOUND AT 8500 FT (AT LEAST IF WE WERE INITIALLY BELOW 10000 FT), RATHER THAN CLB UPWARDS THROUGH OCCASIONAL NBOUND ARR TFC WHICH IS NORMALLY AT 10000 FT ON THE QBALL ARR. ALTHOUGH THE OTHER ACFT WAS HEADED SBOUND, SBOUND TFC IS RATHER INFREQUENT IN THIS AREA. HUMAN FACTORS: IT IS AN INTERESTING NOTE, THAT WHEN ON A COLLISION COURSE, THERE IS NO ANGULAR MOVEMENT OF THE OPPOSING ACFT WHICH TENDS TO MAKE IT APPEAR MOTIONLESS, WITH ONLY BARELY PERCEPTIBLE SIZE GROWTH. DURING THE TIME OF MY DOUBLE TAKE, IT SEEMED AS IF IT WAS IN SLOW MOTION AND THAT THERE WAS VERY LITTLE PERCEPTION OF IMPENDING CONFLICT. OF COURSE, THE COMBINED SPDS WERE QUITE HIGH AS WE WERE AT ABOUT 280-300 KCAS AND I ESTIMATE THAT THE OTHER ACFT WAS AT PERHAPS 150 KCAS FOR A COMBINED CLOSING OF 450 KCAS (A TRUE CLOSING SPD OF 500 KTS), WHICH WOULD BE ROUGHLY 850 FT PER SECOND. LITTLE TIME REMAINS TO SPOT A FAIRLY SMALL OBJECT HEAD-ON, ESPECIALLY WHEN IT HAS NO ANGULAR RELATIVE MOTION TO AID RECOGNITION. IF WE HAD TAKEN NO EVASIVE ACTION, I ESTIMATE THAT WE WOULD HAVE PASSED WITHIN 50 FT. IF I HAD MADE A PURE PULLUP, WE COULD HAVE MADE THE SIT WORSE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.