SN-2013/012: Small Unmanned Aircraft – Security of Antenna Mounts


CAA safety notice released after X factor incident. Are you looking FAA this is the sort of thing you will be expected to do perhaps in 10 years time at the current rate of progress.
1.1 A recent incident involving a multi-rotor Small Unmanned Aircraft (SUA) occurred as a result of a combined GPS/compass antenna mount becoming dislodged. This resulted in erroneous readings and a loss of stabilised flight. The incident has highlighted the necessity of checking the secure attachment of all elements of an SUA during pre-flight checks.
1.2 The multi-rotor SUA was being used for an aerial work filming flight. During the flight theremote pilot noticed a decrease in stability and control. Coincident with this, he also noticed that the GPS/compass antenna had come loose and was wobbling on its mount. As part of the remedial actions/drills, the remote pilot switched control of the aircraft from GPS mode to ATTITUDE mode. However, it was clearly evident that stabilised flight could not be maintained and so the flight was terminated within a designated safe area.
1.3 The purpose of this Safety Notice is to highlight the requirement for the operator to be reasonably satisfied that the flight can be safely made (Air Navigation Order 2009 (ANO)Article 166(2)) and that all appropriate checks on the SUA are completed before take-off.
2 Causal Factors
2.1 The investigation concluded that the lack of security of the GPS/compass antenna mounting was the causal factor.
2.2 The remote pilot had completed his pre-flight checks including a visual inspection of the
GPS/compass antenna, which was mounted on one of the rotor arms. The visual inspection had confirmed the correct orientation; however, the physical security of the mount on the rotor arm was not tested. With hindsight, the remote pilot noted that such a check would have confirmed whether or not the antenna mounting had been properly secured.
2.3 Because of the vibration that the rotor arm was subject to whilst in flight, the antenna mount became dislodged and therefore severely affected the quality of the information it was providing to the SUA’s stabilisation system.
3 Compliance/Action to be Taken
3.1 This Safety Notice recommends the following actions:
a) That the pre-flight checks should include a more rigorous inspection of any GPS/compass antenna mountings, including a physical check that they are securely fitted to the airframe.
b) That remote pilots regularly practise reversionary flight modes (where possible). Remote pilots should be competent with all emergency procedures such as loss of GPS.
c) That any detachable items (payload etc.) must be physically checked for security during the pre-flight checks.
For those that missed it the filming incident that sparked this safety notice.