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Parowan Mid-air Simulation

The video below simulates what the pilots would have seen had they been equipped with FLARM. This mid-air collision took place at the broken_wing_512.jpgUS Sports Class Nationals in Parowan, UT this year.  The screen in the background shows the two glider's flight track synchronized with the FLARM units. 

Two FLARM systems are in the foreground.  The FLARM on the left is receiving GPS data for the red aircraft and the FLARM on the right is receiving GPS data for the blue glider. The two actual, unmodified IGC files are replayed in SeeYou which generates virtual GPS data for the simulation.

Each FLARM is internally calculating its flight path and sending it by radio to the other FLARM.  The FLARM display indicates targets relative to the nose of your aircraft (green for a traffic advisory, red for a collision hazard. Details about the FLARM display indications can be found here.

Timeline (UTC):

21:33:03   Short beeps to indicate that a new glider has entered area of interest
                (not a warning, for awareness only)
21:33:24   First alarm (Level 1)
21:33:42   Estimated impact

Pilot testimonial at the bottom...

Now, watch the video.

Extract from Ed Salkeld's NTSB statement:

Both gliders were flying south on the second leg of the task after turning around at the north end of the first turn area.  Neither pilot had the other in sight.  Just before the collision, both pilots pulled up, slowing down, and turning right to enter a thermal under a large cumulus. They collided part way into their first turn. The point of contact was the left wing of glider N455S and the bottom of the nose of glider N514TW.  Neither pilot saw the other until immediately before impact.  (Ed note;  I saw W3 about 1-2 seconds before impact, no time to maneuver.  W3 never saw me).   Glider N514TW had no noticeable damage, was inspected visually by another glider pilot in the same area and continued on course.  Glider N455S lost 5-6 feet of its left wing.  After carefully evaluating the controllability of the glider, the pilot was able to fly it back to the Parowan airport.  I estimated the performance loss at approximately 15% at the speeds I was flying (50-75kts).

One major point of debate between other pilots was the continuation of both pilots rather than an immediate landing as required by the FARs.  This pilot’s thought processes were as follows.  First the accident occurred at an altitude of 13,500 ft MSL, about 4000 ft above the local terrain and 7,500 ft above the nearest airport, Fillmore.  So an "immediate" landing is clearly not going to happen.  At a low airspeed, the minimum descent time for this glider would be about 40-45 minutes.  After determining the glider was still flying, a few seconds, the pilot carefully checked the controllability in pitch, roll, and yaw, and determined the glider was still flying nearly normally.  A small amount of cross control was required but otherwise the aircraft handled very well.  This pilot had one additional concern.  Wing damage was visible from the remaining outboard end of wing to the vicinity of the spoiler.  The spoiler in the left wing was protruding about 1/8  inch.  The concern was whether or not the spoiler would extend properly, both spoilers symmetrically, or not be retractable once extended.  Therefore it was decided to test the spoilers while still at a high altitude.

The Fillmore airport had been briefed as "closed for re-surfacing" so that was not considered an option (which proved to be incorrect, the resurfacing was complete).  The next nearest airport, about halfway to Parowan is Beaver.  This was within gliding distance.  However, this is a small town, very low activity airport and possibly unattended.  The decision was made to continue to the contest site at Parowan since the soaring conditions were exceptionally good, the glider was flying amazingly well, the left wing (the remaining 25 feet) looked very stable and more importantly to this pilot there was a large staff of experienced contest and pilot crew personnel at Parowan to help if I had problems with the landing.  This decision proved correct as I arrived at Parowan at 4,000 ft AGL allowing plenty of altitude to the test the spoilers and set up a conservative pattern for the landing.