ZK-DYY - Aerodynamic Stall/Spin
Location: Mouth of the Kaipara Harbour, Near Poutu Point, Northland, NZ
Date: 25 November 2006
Type of Aircraft: Amateur-Built Smyth Model S Sidewinder
Synopsis
The aircraft departed from Ardmore airport in Auckland, NZ on the 24th of November, on the way to a "fly-in" at Springhill, Northland, NZ. At approximatly 7.45pm the aircraft was spotted by two fishermen flying low through a heavy rain shower. The fishermen then discovered the aircraft later on, landed on a beach near Potu Point. They remarked that the pilot and passenger both looked distressed. They helped the pilot move the aircraft up to the high tide mark. The pilot and passenger camped on the beach for the night. The fisherman noted that a door appeared to be hanging down under the aircraft.
The next day at 08.00AM, some Potu Point residents helped the pilot tow the aircraft into firm sand. The residents noted that a large flap was protruding below the aircraft. The pilot was anxious to take off, but was unsure of his position, and seemed surprised when he was told where they were. The aircraft took off shortly after this, and one of the residents took some photos of the aircraft, which clearly show the aircrafts speed break protruding below the aircraft.
The aircraft was climbing after take-off from the Kaipara Harbour North Head beach when it suddenly banked to the left, nosed down and dived into the sea. Both occupants were killed in the accident.
Investigation
The pilot had a current private pilots licence and medical at the time of the accident. The only restriction was that he must wear contact lenses while flying, and have a pair of spectacles available if needed.
The pilot had just perchased the aircraft, and only had four hours and twenty minutes of flight experience in the aircraft, one hour of which was a type rating.
The aircraft had no wing flaps, and slowing the aircraft was achieved by extending the speed brake, mounted under the fuselage of the aircraft. Other users of the same aircraft type said that the speed brake was thought to be non-critical and was therefore not included in the aircraft checklist.
The aircraft had a current certificate of airworthiness. It was however noted that the warning light for speed brake extension could not be operated in later testing. It is possible that this light was not working at the time of the accident. The pilot would still have noticed the speed break, had he conducted a thorough pre-flight inspection of the aircraft.
Weather on the day of depature from Ardmore was deteriorating with a cold front approaching from the South. On the second day on the beach, conditions were forcast to be much better, and photos taken at the time support this.
Toxicology results show a level of Tegretol in the pilots blood, which was prescribed to him several days earlier for leg and shoulder pain. The pilot was advised about side affects from this medication. According to the accident report1:
"The drug can cause neurological side-effects including vision problems, fatigue and dizziness. Some cautions to observe until any affects are known is to be careful driving, operating machinery, or doing jobs that require you to be alert."
Conclusion
- The pilot did not carry out a thorough pre-flight inspection of the aircraft prior to the flight
- The aircraft speed brake remained fully extended, causing an increase in the aircraft stall speed
- During a steep climb after takeoff the aircraft entered an aerodynamic stall and spin, and had insufficient height to recover.
- The pilot was taking a medical drug for pain relief. The pilots actions and lack of situational awareness could have been caused by a distraction from the pain he could have still been experiencing, or by the side affects of the drug he was taking.
Lessons Taken From this Accident
This information has been provided in the CAA2 accident report as to what has been implemented since this accident occured:
"From the investigation findings it would appear that the accident occurred after the aircraft entered an incipient spin having aerodynamically stalled when the aircraft was flown into a steep climb. As a consequence, it would have been difficult for the pilot to recover the aircraft in the height available. Given that the speed brake was extended at the time, the resultant drag probably affected the speed at which onset of the stall occurred."
"Human Factors are prevalent in aircraft accident causation. It cannot be ruled out that side effects from the pilots medication contributed to the confusion as to his whereabouts- he could not have seen Great Barrier Island from his position- and to his over sight of the extended speed brake. It is also possible that the pilot’s complaint of a sore shoulder and leg pain may have still persisted, providing a distraction to the pilot. His limited experience on the aircraft type is also noted."
"Because of the dominance of human factors in this accident, lessons learnt remain with pilot education. It is often the case in such instances that the aircraft type, it’s accompanying operating systems, procedures and checklists are perfectly adequate when maintained and operated as intended. Therefore, the investigation makes no recommendation that would seek changes to the aircraft, or operating procedures."
Want to know more?
- CAA Accident Report
- The full accident report provided by the New Zealand Civil Aviation Authority
- Fronts
- Information on the type of weather associated with a Cold Front that the pilot would have encountered on the first day of flying.
- Situational Awareness
- A more indepth look at situational awareness and what pilots can do to maintain this.
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