Date: 201907
Local time of day: 1201-1800
Location: NCT.TRACON, CA
Flight conditions: VMC
Weather elements / visibility: 30
Light: Daylight
Aircraft: Small Aircraft
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Cruise
Airspace: Class E ZOA
ATC / advisory: TRACON NCT
Reporter organization: FBO
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Conflict Airborne Conflict; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Company Policy; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: While flying northbound at 3;500 ft. I observed a para-glider being towed by a boat up to 3;500 ft. above Lake Berryessa.  The para-glider was attached to the boat with a tether which was invisible from [my location].  I took evasive action to avoid the para-glider and the invisible tether which is estimated to be at least 5;000 ft. long.  I continued to circle the lake maintaining separation from the para-glider.  The para-glider remained on the tether for approximately 15 minutes while being towed to altitude.  Once the para-glider cut away from the tether I observed the para-glider conduct aerobatic operations abruptly going inverted and banking in excess of 90 degrees over Lake Berryessa.  These aerobatic operations are conducted within 4 NM of an airway (V-195) and two military training routes (T-329 and T-263) in violation of FAR 91.303. Towed para-gliders routinely operate over Lake Berryessa and have been observed tethered to a boat as they are towed up to 5;000 ft.  As soon as one para-glider cut loose; another para-glider was already in tow.  Sometimes several para-gliders are towed by several boats at the same time.  This took place all day long.  No NOTAM was issued and I was unable to communicate with them on 122.9 after multiple attempts throughout the day to call them.  Even when I could locate the tow boat visually; often times the towed para-glider was impossible or very difficult to see and the tow line was completely invisible. There are serious safety concerns with the fact that these operators have not abided by their own agreed upon SOPs (not responding on frequency and not properly submitting NOTAMS) as well as conducting aerobatics within 4 NM of a federal airway and below 1;500 ft. AGL. This is not only a local problem at Lake Berryessa but a problem nationwide as these operations are occurring in other states as well. There is a serious collision hazard between these towed para-gliders and other aircraft operating in the area.  Travis Air Force Base is located nearby and often conducts military training over Lake Berryessa.  California Highway Patrol helicopters also conduct numerous rescues and training operations over Lake Berryessa.  There are also several flight schools nearby that conduct training operations over Lake Berryessa. There is no communication by the para-gliding operations on the agreed upon 122.9 frequency.  Over the past few weeks I have personally tried contacting them on 122.9 while they were operating with no response. The towed para-gliders are operating over a congested lake with many boats and swimmers on the lake below as well as creating a collision hazard with other aircraft by conducting aerobatics and by being attached to an invisible tether over 1 mile long. There are numerous videos on you tube showing these aerobatic maneuvers.Recommendations:  Require towed para-gliders to get a waiver from the FAA to operate above 500 ft. and to have streamers attached to the tether at 50 foot intervals visible from at least 1 mile away (as required by para-sails; towed hang-gliders; and tethered kites under Federal Regulation part 101).Require towed para-gliders to establish a NOTAM clearly stating that there are para-gliders attached to an invisible tether up to 5;000 feet and moving within a several square mile area.  The NOTAM should give a frequency and phone number to communicate with the tow operators.  The NOTAM should also clearly identify the location of the towed para-gliding activity.Require towed para-gliding operators to monitor and communicate their location on an agreed upon frequency.Prohibit towed para-gliders from conducting aerobatics within 4 miles of a federal airway and below 1;500 feet AGL in violation of FAR 91.303.Additional Information:The towed para-gliders are a commercial operation requiring a commercial permit to operate from the US Bureau of Reclamation. When the para-glider finally does release; the tether remains airborne with a very small drag chute which is much harder to see than the larger para-glider. The tether is being reeled-in with a drag chute attached to the tether to prevent the line from falling into the water.The para-gliders take quite a long time to be towed up to 3;000 -5;000 ft.  The boats towing the para-gliders are tracing a box pattern on the lake covering at least three or four miles and take 12 minutes or more to get to altitude.  It takes them much longer than a winch towed glider at an airport which are launched to altitude within 30 seconds per launch.The towed para-gliders are constantly moving unlike fixed location winch launches of gliders at an airport.  Towed para-gliders are a constantly moving target with a 3;000 to 5;000 ft. invisible line attached to the moving target which represents a significant safety threat to any other aircraft operating in the area.As soon as one para-glider is released; another boat is already starting to tow another para-glider.  Sometimes para-gliders are simultaneously being towed by more than one boat at the same time.  This has the effect of para-gliders being on a tether almost continuously.  Imagine a mile-long invisible clothesline constantly moving over several square miles.  This clearly poses a safety risk to other aircraft.Even with a NOTAM; pilots cannot see the invisible tether.  I know where to look and still cannot see the tether.  When the lake is crowded with boats it is difficult or impossible to tell which boat is towing the para-glider.  In addition; it is often difficult to see the para-glider itself.  Once the para-glider cuts loose the tether and drag chute are even harder to see. There is a high concentration of military aircraft operating near and over Lake Berryessa as well as CHP helicopters conducting rescues in addition to a high concentration of civilian training and recreational flights over Lake Berryessa.




Synopsis: GA pilot reported taking evasive action to avoid a paraglider at 3;500 feet above Lake Berryessa.