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C185, Wellington New Zealand, 1997

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Summary
On Monday 3 March 1997 at 1014 hours, privately owned and operated Cessna 185 encountered wake turbulence from previous departing aircraft, the pilot lost control of the aircraft at a height from which recovery was not possible and the aircraft descended to the ground.
Event Details
When March 1997
Actual or Potential
Event Type
Human Factors, Loss of Control, Wake Vortex Turbulence
Day/Night Day
Flight Conditions On Ground - Normal Visibility
Flight Details
Aircraft CESSNA 185 Skywagon
Operator Not Recorded
Type of Flight Private
Origin Wellington International Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed No
Flight Phase Climb
ICL / ENR
Location - Airport
Airport Wellington International Airport
General
Tag(s) Inadequate ATC Procedures
HF
Tag(s) Distraction,
Ineffective Monitoring
LOC
Tag(s) Flight Control Error"Flight Control Error" is not in the list (Airframe Structural Failure, Significant Systems or Systems Control Failure, Degraded flight instrument display, Uncommanded AP disconnect, AP Status Awareness, Non-normal FBW flight control status, Loss of Engine Power, Flight Management Error, Environmental Factors, Bird or Animal Strike, ...) of allowed values for the "LOC" property.
WAKE
Tag(s) Own separation,
In trail event,
Intersection take off
Outcome
Damage or injury Yes
Aircraft damage Major
Causal Factor Group(s)
Group(s) Aircraft Operation
Safety Recommendation(s)
Group(s) Air Traffic Management
Investigation Type
Type Independent

Description

On Monday 3 March 1997 at 1014 hours, privately owned and operated Cessna 185 became airborne after a take off roll which had begun at a mid-point runway position on runway 16 at Wellington International Aerodrome, behind a Boeing 727 which had just departed from the full length of the same runway and climbed directly ahead. The take off clearance given followed the pilot’s request to ATC for a waiver of the recommended wake turbulence separation which applied which ATC had granted as they were entitled to. When the Cessna encountered wake turbulence from the previous departing aircraft, the pilot lost control of the aircraft at a height from which recovery was not possible and the aircraft descended to the ground. Neither of the two occupants was injured but the aircraft was substantially damaged.

The Investigation

The New Zealand TAIC carried out the Accident Investigation. Their Final Report was published on 11 June 1997 and found that “the Cessna pilot should have allowed more time or distance between his aircraft and the departing Boeing 727. It was concluded that the pilot had then misjudged the likely region of wake turbulence in relation to his take-off path. It was also found that the error resulted not from a lack appropriate flight experience or a lack of awareness of wake turbulence and the adverse effects it can have on an aircraft encountering it but from a lapse in concentration. It was suggested in the Investigation Report that this lapse was probably partly due to the routine nature of the flight and partly because of the pilots preoccupation with some personal business problems which he had been dealing with prior to the accident flight and which remained unresolved.

The Report noted that “Standard separation criteria have been implemented world wide with good reason due to the viciousness and somewhat unpredictable nature of wing-tip vortices. Aerodrome controllers have an appropriate responsibility for only issuing advice and warnings about the potential for wake turbulence and for applying standard separations when they consider that wake turbulence is likely to exist. Pilots must accept the responsibility for avoiding wake turbulence, and use sound judgement when any warnings about its existence are given. Aerodrome controllers however should have clear guidelines to follow when granting a waiver of the separation standards. Some countries do not allow waivers to be granted in certain circumstances.” It also noted that “Some commercial operators allow their pilots to request (wake vortex separation) waivers. The potential therefore exists for a similar occurrence at a busy aerodrome with more disastrous results should an aircraft, for example, collide with a terminal building or strike a taxiing aircraft.”

Safety Recommendations

Two Safety Recommendations were made to the National Aviation Authority (NAA) that they should:

  1. Ensure that waivers of the wake turbulence separation standards are restricted to Visual Meteorological Conditions (VMC) / day only, are required to be acknowledged by pilots using promulgated phraseology and are not permitted to be granted at all under certain specified circumstances.
  2. Publish another article on wing-tip vortices in their safety magazine so as to alert pilots and operators to wake turbulence concerns by highlighting the dangers of encountering such turbulence and explaining how it can be avoided.

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Further Reading