On November 6, 2009, a Cessna 310R, C-GFIT operated by Lockhart Air Services Limited was involved in an aviation accident near Cat Lake, Ontario, 8 nm SW, CA. 3 people were killed. Investigators recorded the probable cause as: The aircraft’s altimeters were likely set incorrectly, resulting in a higher reading that led the pilot to descend below a safe altitude. This summary draws on records from the Transportation Safety Board of Canada (TSB).
A Cessna 310R (C-GFIT) operated by Lockhart Air Services collided with terrain near Cat Lake, Ontario, on 6 November 2009. All three occupants were killed. The investigation found the altimeters were likely set incorrectly.
Flight Details and Accident Sequence On 6 November 2009, a Cessna 310R (registration C-GFIT, serial number 310R1865) operated by Lockhart Air Services Limited departed Sioux Lookout, Ontario, at approximately 1800 local time. The aircraft was on a night visual flight rules (VFR) flight to Cat Lake, Ontario, carrying a pilot and two passengers. The estimated time en route was 45 minutes. After takeoff, the pilot advised the Sioux Lookout Flight Service Station that the aircraft was clear of the zone and climbing to 5,500 feet above sea level (asl). Upon arrival in the Cat Lake area, the aircraft flew over the airport and proceeded southwest. The flight path was consistent with a visual inspection of the runway and a downwind leg to intercept the final approach to Runway 11. While manoeuvring to join the final approach, the aircraft collided with rising terrain approximately eight nautical miles southwest of Runway 11. The aircraft struck a densely wooded area. During the impact sequence, the fuel cells ruptured, resulting in an explosion and torching of tree tops. The pilot and both passengers were fatally injured upon impact, and the aircraft was destroyed. The fuselage was not consumed by fire. At 2200, when the aircraft had not yet arrived at its destination, the operator notified the Joint Rescue Coordination Centre (JRCC) in Trenton, Ontario, and a search was initiated. The aircraft was located at 1930 on 8 November 2009 in a wooded area about eight nautical miles southwest of Cat Lake. The aircraft was equipped with a Dorne & Margolin ELT 8.1 emergency locator transmitter (ELT). The ELT antenna was torn off during impact, and as a result, no ELT signal was transmitted. ## Weather and Environmental Conditions There is no recorded or reported weather for Cat Lake. The nearest reported weather was for Pickle Lake, Ontario, 70 nautical miles to the east. The weather at Pickle Lake at 1900 was: wind 170° True (T) at 10 knots, variable from 080° to 230°, visibility 15 statute miles, a few clouds at 24,000 feet above ground level (agl), temperature 4°C, dew point 2°C, altimeter 29.41 inches of mercury, remarks cirrus 1 okta, sea level pressure 977 hectopascals. The barometric pressure in the area was active before the occurrence; the Pickle Lake pressure had decreased from 30.18 to 29.41 inches in a 24-hour period. Sunset on 6 November occurred at 1633, and the end of official twilight was 1709. Moonrise did not occur until 1936; the flight arrived in the Cat Lake area in total darkness. The topography southwest of Cat Lake consists of muskeg and bush and, at night, is devoid of any lights or other distinguishable features that could assist a pilot in discerning a horizon. Darkness and the absence of visual cues can adversely influence a pilot’s perception of the aircraft’s position and movement, and make it more difficult for a pilot to maintain control and to avoid terrain. In some situations, the limited visual cues in sparsely settled areas may lead pilots to believe that they are at a higher altitude than they actually are. ## Pilot and Aircraft The pilot was certified and qualified in accordance with existing regulations and met the crew rest requirements. The pilot held a commercial licence with a current instrument rating and had a total of 1,819 hours of flying time, including a total of 176 hours on the Cessna 310. There was no indication of any physical issue with the pilot that may have contributed to the accident. The Cessna 310R is a twin-engine, piston-powered aeroplane equipped to carry a pilot and five passengers. It was approved for day/night visual flight rules (VFR) and instrument flight rules (IFR) operations. It was also equipped with an autopilot and a global positioning system (GPS). Records indicate that the aircraft was maintained in accordance with Lockhart Air Services’ approved maintenance control system. A review of the aircraft’s weight and balance information indicated that the aircraft was within the prescribed limits during the occurrence flight. A review of the operational flight plan and fuel upload receipts indicated that the aircraft had approximately 400 pounds of fuel on board at the time of the occurrence. The pilot did not report any technical difficulties with the aircraft prior to the accident. A review of technical records indicates that there were no deferred or outstanding defects on the aircraft. The aircraft was equipped with two barometric pressure altimeters. Both altimeters incorporated the three-pointer type of display. This display format has a higher potential for being misread, as compared to altimeters incorporating other types of displays, such as the drum-and-pointer type. Nearly 12 full turns of the adjustment knob are required to effect a one-inch barometric pressure change in the altimeter setting. A one-inch decrease in barometric pressure results in an increase of indicated altitude of about 1,000 feet if no adjustment is made. An adjustment of this magnitude is uncommon in day-to-day operations. New, larger, technologically advanced aircraft are increasingly being equipped with a drum-and-pointer type of altimeter system from the factory. The aircraft’s last flight before the accident flight occurred on 5 November 2009. The altimeter setting at Sioux Lookout at the conclusion of that flight was 30.13 inches. The altimeter setting for Sioux Lookout at the start of the accident flight was 29.44. ## Wreckage Information The tree strikes and wreckage information indicated that the aircraft contacted the trees on rising terrain in a near-level flight attitude. The initial tree strikes involved just the tips of the trees, for approximately 150 yards, and progressed to severe shearing and breaking of the tree trunks for another 150 yards until the remaining aircraft fuselage came to rest. The direction of the wreckage trail was 340° magnetic, indicating that C-GFIT was tracking away from the village of Cat Lake at the time of impact. The wreckage site elevation was 1,460 feet asl. The degree of damage indicated that the engines were producing power and the aircraft was operating at significant speed at impact. This, coupled with the wings-level shallow descent angle at which the aircraft contacted the trees, indicates that the aircraft was likely operating normally and under the control of the pilot at impact. The right altimeter subscale was set to 30.40 inches, which was approximately one inch higher than the prevailing altimeter setting of approximately 29.41 inches. The Lockhart Air Services SOPs require pilots to set and cross-check both altimeters, so the left altimeter was likely set to 30.40 inches as well. Because it requires many turns of the setting knob to achieve a one-inch change in the setting, it is likely that the pilot set the fractional subscale to 0.40, thereby setting the barometric pressure of both altimeters approximately one inch too high. Setting the altimeters one inch too high would cause them to read approximately 1,000 feet higher than the aircraft’s actual altitude, and the pilot would be led to believe that he was about 1,000 feet higher than he actually was. In total darkness and with no visual cues, the pilot would have to rely solely on his altimeters to determine his altitude. A 1,000-foot error could be more difficult to detect with the three-pointer type of altimeter installed on the occurrence aircraft because the longer pointers (the ones most often referenced) would be in a similar position at either setting. As a result, the pilot likely did not notice the incorrect altimeter settings and, during the downwind leg, descended to terrain height believing that he was descending to the circuit altitude. The aircraft overflew the airport and then turned away from the airport in a westerly direction, in accordance with the Lockhart Air Services procedure of confirming that the runway was suitable for use, and then joined the downwind leg. The position of the wreckage indicates that the pilot intended to intercept the final approach for Runway 11. In total darkness, flying the aircraft away from a lighted community and runway placed the aircraft in a position where the pilot was left without any visual clues that might help him determine his position relative to the ground and increased the risk of collision with terrain. ## Findings as to Causes and Contributing Factors The aircraft’s altimeters were likely set incorrectly, resulting in a higher reading that led the pilot to descend below a safe altitude. While manoeuvring for the approach to Runway 11 at Cat Lake, the aircraft descended and collided with trees on rising terrain. Finding as to Risk: Manoeuvring at night away from visual cues may result in a sudden loss of visual reference, thereby increasing the risk of collision with the ground. Other Finding: The aircraft would have been operated at a lower altitude throughout the flight, risking a potential conflict with other en route traffic or terrain. This report concludes the Transportation Safety Board’s investigation into this occurrence. Consequently, the Board authorized the release of this report on 29 April 2010.
Probable cause
The aircraft’s altimeters were likely set incorrectly, resulting in a higher reading that led the pilot to descend below a safe altitude. While manoeuvring for the approach to Runway 11 at Cat Lake, the aircraft descended and collided with trees on rising terrain.