Last updated: 28 April 2017
Narrative:The accident aircraft, a Convair 580A, was one of two aircraft that had recently been delivered to the Government of Saskatchewan's Northern Air Operations. CV-580As had been converted to aerial tankers (water bombers) for fighting forest fires. The accident flight was a training flight that consisted of stop-and-go circuits at the La Ronge Airport (YVC). The purpose of the training was to instruct and cross-qualify new CV-580A captains as first officers for future training requirements. The first two circuits were unremarkable; all altitudes, speeds, and aircraft performance were as expected for the exercises being carried out.
The final approach leg of the third circuit differed from the first two in that the aircraft's speed was lower. The airspeed was stabilized at 103 knots indicated airspeed (KIAS). The rate of descent and respective altitudes were unstable compared with those of the first two circuits. The captain had called for a power setting of 150 to 200 hp on both engines on short final approach, and the flaps, which had been set at 24º, were selected to 28º. The aircraft entered a high sink rate of approximately 1280 feet per minute.
In an effort to arrest the high sink rate, the captain, who was the pilot flying, called for increased power, briefly increased pitch attitude, and then touched down on the runway, approximately 200 feet beyond the threshold. The first officer, the pilot not flying, responded to the captain's call for power by rapidly advancing both power levers to a point beyond the maximum power setting limit. When the power levers were advanced, the left propeller immediately autofeathered and the left engine shut down. The captain, noting the position of the power levers, quickly retarded them to a position he assumed would give maximum power.
During the final approach leg and on the go-around, the captain was not continuously setting or monitoring the engine power settings and consequently was unaware of the engine power or the nature of the emergency. The elapsed time between encountering the high sink rate and initiating the go-around was approximately seven seconds.
After touching down on the runway, the captain, believing that the aircraft was not aligned with the runway, initiated a go-around. The autofeather was not called out or identified as an emergency. The decision to go around was not called out or communicated to the first officer. The go-around was commenced at an airspeed of approximately 94 KIAS (V1 minus 2)1. The gear was then selected up during a momentary positive rate of climb and the flaps were retracted at an airspeed of 95 KIAS, after the aircraft cleared the VOR radio range transmitter located left of the departure end of runway 36.
Shortly after the aircraft became airborne, its left wing dropped slightly and could not be righted. The airspeed fluctuated between 93 and 98 KIAS and would not increase with a positive pitch angle. Once the flaps were retracted at 95 KIAS, the angle of bank increased uncontrollably. The aircraft started to descend, and collided with trees and terrain in a wooded area on the airport property.
Probable Cause:FINDINGS AS TO CAUSES AND CONTRIBUTING FACTORS
1. The flight crew attempted a low-energy go-around after briefly touching down on the runway. The aircraft's low-energy state contributed to its inability to accelerate to the airspeed required to accomplish a successful go-around procedure.
2. The rapid power lever advancement caused an inadvertent shutdown of the left engine, which exacerbated the aircraft's low-energy status and contributed to the eventual loss of control.
3. The inadvertent activation of the autofeather system contributed to the crew's loss of situational awareness, which adversely influenced the decision to go around, at a time when it may have been possible for the aircraft to safely stop and remain on the runway.
4. The shortage and ambiguity of information available on rejected landings contributed to confusion between the pilots, which resulted in a delayed retraction of the flaps. This departure from procedure prevented the aircraft from accelerating adequately.
5. Retarding the power levers after the first officer had exceeded maximum power setting resulted in an inadequate power setting on the right engine and contributed to a breakdown of crew coordination. This prevented the crew from effectively identifying and responding to the emergencies they encountered.
FINDINGS AS TO RISK
1. The design of the autofeather system is such that, when armed, the risk of an inadvertent engine shutdown is increased.
2. Rapid power movement may increase the risk of inadvertent activation of the negative torque sensing system during critical flight regimes.
1. There were inconsistencies between sections of the Conair aircraft operating manual (AOM), the standard operating procedures (SOPs), and the copied AOM that the operator possessed. These inconsistencies likely created confusion between the training captain and the operator's pilots.
2. The operator's CV-580A checklists do not contain a specified section for circuit training. The lack of such checklist information likely increased pilot workload.
Loss of control
N30EG was withdrawn from use in 1998 and went to the Mid Atlantic Air Museum (Reading, PA). In August 2005 it was exported to Canada and converted to airtanker as C-GSKJ