What happened
On August 3, 2018, a private Reims Aviation FR172K, registration LN-ACA, was conducting a VFR flight from Stokmarknes to Tromsø. While cruising near Senja, the pilot encountered broken cloud layers and decided to descend to maintain visual contact with the ground. However, the weather conditions deteriorated, and the aircraft eventually entered instrument meteorological conditions (IMC).
Shortly after entering the clouds, the aircraft's vacuum pressure dropped to zero, causing the artificial horizon, directional gyro, and autopilot to fail. While attempting to navigate using only the remaining instruments, the pilot experienced two separate loss-of-control events. In the first instance, the aircraft entered a spiral dive, descending at approximately 11,000 feet per minute before the pilot regained control. A second spiral dive followed, with the aircraft dropping to 1,500 feet.
Unable to continue the flight to Tromsø due to heavy rain and low visibility, the pilot identified a 300-meter stretch of public road (Fylkesvei 232) and performed an emergency landing. The aircraft sustained minor damage to the left wing tip after contacting a bush during the rollout, but there were no injuries to the pilot or the passenger.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the mechanical failure of the vacuum pump and the weather conditions at the time of the incident. The investigation confirmed that the Rapco 215CC vacuum pump had failed, rendering the primary flight instruments inoperative. The aircraft was operating under a maintenance program that required inspections every 100 hours, and the pump had 284 hours of use since its last inspection.
Investigators also reviewed the meteorological data, which showed broken cloud layers and rain across the flight path, confirming that the aircraft was flying in conditions that did not meet VFR requirements.
Findings
- The primary cause of the instrument failure was the failure of the vacuum pump.
- The pilot was flying in IMC without the required instrument rating, a situation made significantly more dangerous by the simultaneous loss of the artificial horizon and autopilot.
- The pilot's ability to maintain control for 34 minutes using limited instruments was considered highly challenging and required extreme concentration.
- The two loss-of-control events occurred over low-lying valleys; had they occurred over the high mountains of Senja, the outcome would likely have been fatal.