Incident
On 3 February 2022 at 10:38, aircraft TF-ABB, a Textron 172N, departed Reykjavik Airport (BIRK) with one pilot and three passengers. The planned flight duration was 2 hours, and the aircraft had an endurance of 4 hours. The flight route took it south along the coast, then northwest over Grímsnes, and into the southern part of Lake Þingvallavatn. At 11:51, the aircraft came to rest in the lake at a location known as Ölfusvatnsvík.
Aircraft and Pilot
The aircraft was a 1977 Textron 172N, serial number 172-69176, registration TF-ABB, with a valid airworthiness certificate. It was powered by a Lycoming O-360-A4M engine of 180 HP. The pilot, aged 49, held a valid CPL with SEP and FI endorsements.
Search and Recovery
After the aircraft failed to arrive at its scheduled landing time of 12:38, search efforts began shortly before 13:00. The alert was activated at 13:32. Based on MLAT tracking from Isavia, the last radar points indicated the aircraft was heading northwest over road 350 at about 400 feet MSL around 11:45. Further clues, including a cell phone location in Ölfusvatnsvík and a slick on the water, concentrated the search there. At 22:10 on 4 February, an autonomous underwater vehicle (AUV) located an aircraft at a depth of 47 meters. It was confirmed as a Textron 172 at 00:56 on 5 February, and later as TF-ABB via ROV. The aircraft was recovered on 22 April 2022.
Wreckage Examination
The aircraft was found empty of occupants and tilted forward and left on the lake bottom. All control surfaces were present. The left wing tip and lower nose were embedded. Minor damage was observed, including a broken antenna on the left roof. Flaps were extended to about 30°. The propellers appeared intact. Cockpit switches were found with master and ignition off, throttle retracted 4.0 cm out of 5.5 cm, mixture full rich, and carb heat on. The fuel system was set to both tanks. 49 liters of Avgas 100 LL were found in the right tank and 14 liters in the left. Water contamination was present: 58 liters in the right tank and 28 liters in the left.
Passenger seat belts in the rear were likely not used; the pilot and front passenger did not use shoulder harnesses. The right front seat lap belt showed no signs of use. Life vest packages were unopened. The right door was closed with its window unlocked and resting back on the latch; the left door was closed with its window slightly open.
Weather
At 12:00 on the day of the accident, conditions at the lake were calm easterly winds, light cloud cover, temperature -8°C, and dew point -11°C. Video from onboard revealed ice forming in Ölfusvatnsvík, though it appeared very thin with large open patches.
Ongoing Investigation
The investigation by the Icelandic Transportation Accident Investigation Board (RNSA) continues, including analysis of data from recovered electronics, examination of the ELT (which was armed but did not transmit), teardown inspection of the engine, weight and balance calculations, and review of maintenance records.