What happened
On 1 February 2015, the pilot of a Robinson R44 helicopter, registered VH-YYF, prepared for a local flight at Warwombie Station, near Hughenden, Queensland. The pilot did not observe any abnormalities during the pre-flight inspection, with oil quantity within the normal range, about 80 L of fuel on board, and no water or other contaminants found during a fuel drain and check. The helicopter was loaded within the normal operating weight and balance limitations. The temperature was 20 °C, the sky clear of cloud and the wind was calm.
At about 0800 Eastern Standard Time (EST), the helicopter lifted off normally. At about 20 ft above ground level, the pilot lowered the nose of the helicopter in attempt to gain forward speed and transition from hover to forward flight. The helicopter then sank quickly and the rotor rpm decayed. The pilot pulled back on the cyclic[1] control in an attempt to flare and reduce the rate of descent, prior to contacting the ground. The left skid contacted the ground first and then the helicopter spun to the right. The rear of the right skid dug into the ground and the helicopter rolled onto the right side. The pilot selected the master switch off before exiting the helicopter uninjured. The helicopter sustained substantial damage (Figure 1).
Pilot comments
The pilot had about 9,000 hours total helicopter aeronautical experience. He had practiced autorotations often and believed that his experience enabled him to escape uninjured. The incident had happened very quickly and he was unsure what had caused the helicopter to sink and lose rotor rpm.
Figure 1: Damage to VH-YYF
Source: Daniel Cook
Safety message
The Robinson Helicopter Company Safety Notice SN-24 stated that rotor stall due to low RPM causes a very high percentage of helicopter accidents. These mostly occur close to the ground during take-off and landing. Safety Notice SN-10 reminds pilots to have their ‘reflexes conditioned so they will instantly add throttle and lower collective to maintain RPM in any emergency’.
The pilot in this incident had completed significant number of practice autorotations. The avoidance of injury highlights the benefits of practice. The following links provide information regarding practice autorotations:
• www.aviationtoday.com/rw/training/specialty/Flight-Training-Tips-Dancing-With-the-Devil_13632.html
• www.faa.gov/documentLibrary/media/Advisory_Circular/AC_61-140.pdf
Aviation Short Investigations Bulletin - Issue 40
Purpose of safety investigationsThe objective of a safety investigation is to enhance transport safety. This is done through:
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- A primary helicopter flight control that is similar to an aircraft control column. Cyclic input tilts the main rotor disc varying the attitude of the helicopter and hence the lateral direction.