The Australian Transport Safety Board (ATSB) today released its final report into the fatal crash of a Beech King Air at Essendon Airport on 21 February 2017.
King Air VH-ZCR crashed immediately after take-off from Runway 17, hitting the Direct Factory Outlets building and killing pilot Max Quartermain and his four passengers.
The ATSB has determined the crash was caused because the pilot did not detect the rudder trim was set in the full-left position, which hampered the aircraft's ability to track straight and climb.
According to the ATSB, the aircraft's take-off roll was longer than expected and witnesses familiar with the King Air type noted a yaw to the left once ZCR became airborne. A shallow climb was followed by a substantial side-slip to the left, whilst the aircraft roll to the left didn't exceed 10 degrees.
The aircraft was able to climb to an altitude of only 160 feet AGL and increasingly diverged to the left of the runway centreline. ZCR then started descending and the pilot made seven rapid Mayday calls before the aircraft struck the building.
Although the crash was first thought to be the result of engine failure, the ATSB found that both engines had been developing power at the time of impact, and recordings don't detect any change in the engine noise.
"On-site and post-site examinations of the aircraft found the rudder trim was in the full nose-left position at the time of impact," the ATSB report states. "This was consistent with the substantial side-slip at impact derived from the roof collision marks.
"As the ATSB established that ZCR's engines were capable of normal operation and were operating at similar settings, there was no apparent reason identified, such as asymmetric power condition that would require the use of full rudder trim by the pilot.
"As it was unlikely that the pilot had set full nose-left trim during or after take-off, the rudder trim was probably mis-set in the full nose-left position prior to take-off."
Trim runaway was discounted because the aircraft did not have an electric rudder trim and no connection to the autopilot or yaw damper.
The ATSB also noted that the aircraft did not have flaps set at the time of impact. It was normal practice to use approach flaps for take-off, and the ATSB thought that although it was possible they were retracted after take-off, it was considered highly unlikely due to the short time between rotation and the crash.
The flap setting, when combined with the mis-set trim, caused the ATSB to question whether or not the pre-take-off checks were adequate.
ATSB investigations also showed that the aircraft was likely over its maximum take-off weight by 240 kg, but that did not contribute to the accident.
Further investigation revealed that the severity of the crash was exacerbated by the DFO building the aircraft hit. The ATSB also found that other buildings in the precinct of the DFO breached the Obstacle Limitation Surface (OLS) for Essendon. A separate investigation into the approval process for these buildings is still in progess.
The full accident investigation report is on the ATSB website.