| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
On 11 February 2018, at 1227 Eastern Daylight-saving Time (EDT), the crew of a Robinson R22 Beta helicopter were conducting flight training on the western grass area of Bankstown Airport, New South Wales (NSW). There were an instructor and a student on board. The weather at the time was fine with 15 knots of wind from the south-east gusting to 25 knots.
While practicing hover drills at 2–3 m above the ground, with the student at the controls, the helicopter commenced a yaw and started to spin anti-clockwise. The rate of rotation increased and the instructor took control of the helicopter, but was unable to arrest the spin. The helicopter impacted the ground, the tail boom separated and the skids were flattened. The instructor shut down the helicopter, and both crew members walked to the flight school. Both crew members sustained minor injuries.
Figure 1: Accident scene, indicating direction of rotation at time of impact.
Source: NSW Police Force
Safety message
Instructing ab-initio students in rotary wing flight is a complex task. The instructor must allow the student the experience of controlling the helicopter while moderating the student’s inputs in order to ensure controllability of the aircraft. Flight in gusty conditions increases difficulty for both the instructor and the student.
Wind gusting between 15 and 25 knots places the helicopter in and out of effective translational lift.[1] Students may have trouble reconciling the effect of their inputs against movement created by the wind. Instructor workload increases as the student’s control inputs are likely to be larger and less predictable than those used in calm conditions.
CASA Australia and CAA New Zealand produced a Helicopter Flight Instructor Manual which describes hovering as requiring a high degree of coordination. It advises that hovering should not be taught until the student is competent in manipulation of flight controls in forward flight, climbing, descending and turning. The manual also advises to ‘keep a close watch on temperatures, pressures and wind velocity during prolonged hovering’.
While conducting flight training instructors should consider meteorological conditions and the limits of the student’s ability to manage them. Safety Notice SN-42 in the Robinson R22 Pilot’s Operating Handbook advises that ‘…pilots should be aware of conditions (a left crosswind, for example) that may require large or rapid pedal inputs’. To assist instructors, flying schools should publish policies to limit flight in unfavourable conditions and accommodate the competence of their students in varying weather conditions.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
__________