Here are some thoughts on the preliminary report from the ATSB on the ABC helicopter crash on the 18th of August 2011. 

The following is an opinion based upon stated facts.  It is noted that conclusions as to the most likely cause of the crash will be revealed in the final ATSB report.

REGARDING THE ATSB REPORT:

Interesting to note that a once-per-minute back to base reporting device was fitted and activated on the night of the crash.

The flight departed well after evening civil twilight, which occurred at 1822 hrs – meaning that it was officially and legally dark for aviation purposes.  The moon had not yet risen, and was due to do so at 2158.  This combination of facts illustrate that the darkness, combined with a remote area would mean that discernment of visual cues for visual flying would have been extremely difficult.

Here’s the sequence of data from the position reporting device:

  1. Switched on at 1856:40 – on ground
  2. Airborne report at 1859:40
  3. First airborne automatic report one minute later at 1900:40
  4. The helicopter did not record another report – it had already crashed within one minute of the last report

At the time of the only airborne report, the helicopters height, speed and direction were:

  1. Height 1,165 ft above mean sea level (AMSL)
  2. Speed 66 knots (kts)
  3. Heading 045 degrees

This information is very important:

  1. It indicates that the helicopter climbed to over 1,000 feet, and descended the same distance within 2 minutes of being airborne. 
  2. We can deduce this because the automatic position reporting device did not get an opportunity to report beyond the 1900:40 mark.

Moreover, we can accurately assess that:

The helicopter – from the last known position at 1,165 – descended at over 1,000 feet per minute in order impact the ground before the next scheduled position report.

  • This is a very high rate of descent for an aircraft that is flying at night and in close proximity to the ground. 
  • Rates of descent of this magnitude require immediate and aggressive corrective actions to make possible a recovery from heights below 1,000 ft.

Further factual information is also revealing:

  1. The standby artificial horizon was operating at the time of impact and was locked in appromately 90 degrees right-wing-low orientation, and almost longitudinally level (nose neither up or down).
  2. When correlated with the impact photographs, it indeed does appear that the blades struck the ground almost coincidentally with the fuselage – indicating that the helicopter was almost on its side before ground impact.


Therefore, from assessment of the facts in the interim report, it appears that the pilot was disoriented well before impact.  This allowed the aircraft to descend rapidly from approximately 1,000 feet, whilst rolling over onto its right side, culminating in an unrecoverable attitude and rate of descent.  The helicopter then appears to have impacted the ground at high vertical speed at almost 90 degrees right-wing-low, with a nose-level attitude.  The helicopter then disintegrated upon impact and a post impact fire ensued.  It seems likely that the occupants would have been killed by the initial impact.

The above is an opinion based upon the stated facts from the ATSB.  The full report will contain further facts about the accident, and hopefully a conclusion as to the most probable cause of the crash.

LINK:
http://www.atsb.gov.au/media/3466996/ao2011102_prelim.pdf