Narrative:

I and the pilot of the second glider briefed our cross country flight with the understanding that we would maintain 100 meter separation with each other ideally off to one side to double our chances of finding optimal thermals. I received the communication 'I am following you' as we began our northeast leg at about 13;500 MSL. Reliable communication between gliders was apparent on glider air-to-air frequency during this leg of about 80 KM. After I announced 'now we are heading west' after our turn point from the 050 heading; I heard no further communication from the other glider; nor acknowledgement of my broadcast. About seven minutes later; I scanned to my right; commenced a thermalling turn to the right and found myself in hazardous proximity to the second glider. I immediately flew back to our departure airport; concerned that my fellow glider pilot had a physical or aircraft problem that precluded his answering my several subsequent radio calls. Soon after the hazardous proximity event; I noted his aircraft straight and level; but then lost visual contact with his glider for the remainder of my flight. As he did not respond to my calls; and I had no further visual contact with that aircraft; I broadcast on 121.5 a mayday concerning the lost or somehow disable aircraft. I received no response on 121.5. I landed routinely 20 minutes later; and the other glider only a minute later. After examining my glider on the ground; it was learned that the speaker connection had failed sometime before the northwest turn point; so I could hear no transmissions. I was unaware that the other glider had broadcasted that it was flying at various times at my 3:00; 6:00; and 9:00 positions to accomplish photos of my glider. His broadcasts; I later learned on the ground; had requested that I maintain straight and level flight while he flew nearby; but these broadcasts were neither heard nor acknowledged. For me the lessons have been:1. Any transmission not acknowledged has not been heard.2. Team flying should be conducted as per ground briefing agreements which should include contingency plans for lost radio communication.3. Formation flying of any type should never be undertaken without reliable communication between aircraft. 4. See and avoid remains paramount in VMC flight; and team flying or contest flying gliders should be equipped with a rear view mirror within the canopy to allow sighting of aircraft directly behind and overhead.5. Any aerial photography should not be done by pilot flying.6. Equipment such as radios or speakers or microphone may fail in-flight despite proper operation before launch and during a portion of the flight.

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Original NASA ASRS Text

Title: Glider pilot reports lost communication with his wingman during a cross country formation flight. Unable to communicate or see his wingman; a turn is initiated resulting in a NMAC.

Narrative: I and the pilot of the second glider briefed our cross country flight with the understanding that we would maintain 100 meter separation with each other ideally off to one side to double our chances of finding optimal thermals. I received the communication 'I am following you' as we began our northeast leg at about 13;500 MSL. Reliable communication between gliders was apparent on glider air-to-air frequency during this leg of about 80 KM. After I announced 'now we are heading west' after our turn point from the 050 heading; I heard no further communication from the other glider; nor acknowledgement of my broadcast. About seven minutes later; I scanned to my right; commenced a thermalling turn to the right and found myself in hazardous proximity to the second glider. I immediately flew back to our departure airport; concerned that my fellow glider pilot had a physical or aircraft problem that precluded his answering my several subsequent radio calls. Soon after the hazardous proximity event; I noted his aircraft straight and level; but then lost visual contact with his glider for the remainder of my flight. As he did not respond to my calls; and I had no further visual contact with that aircraft; I broadcast on 121.5 a mayday concerning the lost or somehow disable aircraft. I received no response on 121.5. I landed routinely 20 minutes later; and the other glider only a minute later. After examining my glider on the ground; it was learned that the speaker connection had failed sometime before the northwest turn point; so I could hear no transmissions. I was unaware that the other glider had broadcasted that it was flying at various times at my 3:00; 6:00; and 9:00 positions to accomplish photos of my glider. His broadcasts; I later learned on the ground; had requested that I maintain straight and level flight while he flew nearby; but these broadcasts were neither heard nor acknowledged. For me the lessons have been:1. any transmission not acknowledged has not been heard.2. team flying should be conducted as per ground briefing agreements which should include contingency plans for lost radio communication.3. formation flying of any type should never be undertaken without reliable communication between aircraft. 4. see and avoid remains paramount in VMC flight; and team flying or contest flying gliders should be equipped with a rear view mirror within the canopy to allow sighting of aircraft directly behind and overhead.5. any aerial photography should not be done by pilot flying.6. equipment such as radios or speakers or microphone may fail in-flight despite proper operation before launch and during a portion of the flight.

Data retrieved from NASA's ASRS site as of July 2013 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.