Air NZ jet takes off at Queenstown Airport

Should Our Airport be more safe?

A Black Star and Category X rating

Queenstown Airport is at the worst possible end of the safety spectrum for operation of scheduled commercial jet aircraft.

It has a short runway, difficult wind conditions (at the confluence of three mountain valleys which causes turbulence and windshear), minimum legal RESA’s at 90m instead of the industry standard 240m, and a high level of general aviation traffic. This results in Queenstown Airport having a Black Star Category X airport safety rating.

Queenstown Airport's proximity to the alpine divide manifests challenging mountain weather as easterly travelling depressions push against the Southern Alps.  Severe turbulence, downdraughts and windshear can be experienced within the Queenstown basin below 1,200m. Runway conditions can change rapidly with snow, slush or ice. Snow showers can cause rapid reduction in visibility.

These hazards cause greater restrictions on aircraft operation with airlines applying special Queenstown rules that are more conservative than the aircraft manufacturers’ certified limits. Restrictions such as a reduction of permitted crosswind tolerance, down from 40 knots to 25 knots (80km/hr to 50km/hr) and permitted tailwind tolerance reduced from 15 knots to 5 knots (50km/hr to 10km/hr). Flight paths are adapted to be steeper than standard decent rates and significantly steeper climb rates on takeoff. All airlines require that only the Captain rather than copilot must control the aircraft for takeoffs and landings at Queenstown, and Captains must have completed training specific to Queenstown Airport before being able to operate in it.

While in time there may be incremental improvements in some aspects, the essential profile of the restricted size of the Frankton location within its mountainous terrain will always pose challenges to safety.

Queenstown Airport will forever risk the potential that one serious accident could cause immediate restrictions placed by CAA, ICAO, IFALPA, NZALPA or any other agency to substantially impact its viability.

This poses a major and continuing risk to the local and regional economies.

We believe that the local and national economic dependence on tourism, and the importance of Queenstown as its principal jewel, mean the current high risk profile of Queenstown Airport is unacceptable and will become more unacceptable with time.

Current restrictions

Airbus A320 & Boeing 737 rules for Queenstown

  • Maximum crosswind permitted is reduced from 40 knots to 25 knots (80km/hr to 50k/hr)
  • Maximum tailwind permitted is reduced from 15 knots to 5 knots (30km/hr to 10km/hr)
  • Only the Captain can control the aircraft for takeoff and landing
  • The Captain must have undertaken specialist training specific to ZQN operations

Queenstown Airport RESA extension zones

Minimal Safety at Runway Ends

Queenstown Airport's 1,777m runway is already at the short end for jet aircraft. Runway Emergency Safety Area's (RESA) are located at each end as a safety buffer in case of a runway 'excursion' - when an aircraft undershoots or overshoots the runway. The industry standard is for a RESA's length of 240m at both ends of the runway. Queenstown Airport has the minimum allowed RESA at just 90m at each end.

The rapid drop off in the terrain at both ends amplifies this risk, both in making it more challenging for pilots to access their approach and in the event of an undershoot or roll-off.

There appears little prospect that the Queenstown Airport RESA lengths will ever be extended. To the west this would require extending the runway towards the lake, with the required earthworks overlaying homes in Ross and McBride Streets and Lake Avenue, plus a new underpass and bridge for where it would cross State Highway 6. To the east it would require another mammoth earthworks extending into the shotover river, plus a bridge over Hawthorne Drive.

This creates a risk for Queenstown Airport that an incident here or elsewhere could force it to shorten the runway area by redesignating part of it as RESA. This could end jet services into Queenstown, as this news report explains. 

Risk always exists and cannot be avoided completely. Queenstown Airport Corporation presumably assesses the cost-benefit tradeoff for investment in infrastructure risk mitigation measures to reduce the hazard of an end of runway excursion. A problem with this, though, is that the financial costs that result from an excursion event occurring fall 90% on the Airline, with only 10% impacting the Airport (Estimated Cost-Benefit analysis of runway severity reduction, J.N.M van Eekeren, Jan 2016).  Beyond the costs to the Airline and Airport, the financial costs that would impact on our broader tourism based economy would also be substantial. In addition to potential reduction in tourist demand, the event might cause immediate restrictions placed by CAA, ICAO, IFALPA, NZALPA or any other agency to restrict operation of Queenstown Airport until improved infrastructure is commissioned, cutting flights for months or years.

The situation where the Airport must carry the full cost of risk mitigation infrastructure while only receiving a small portion of the potential benefit of reducing the seriousness of an accident is a market failure. If the potential loss to our local economy is similar to the cost impact on an Airline, then Queenstown Airport will under value risk mitigation costs by a factor of 20 times. In this situation, even a well managed Airport will always under invest in risk mitigation.

A jet airline Captain familiar with Queenstown Airport assessed that it was not a question of if a runway excursion might occur, but when. 

Relocating the airport would resolve this problem.

The recent incident (4 May 2019) when Miami Air International's Boeing 737-800 slid off the runway in Florida should be a wake up call for us in Queenstown. The Naval Air Station runway is 2,400, long (620 longer than ZQN) and with fully compliant RESA zones, and yet the jet overshot into the St John's River. It's notable that the geography of Florida is flat and the weather warm. The risk of a runoff in Queenstown is more likely at night, in winter and with adverse weather.

The "loss of separation" incident where a Pacific Blue jet came within 300 vertical meters of a Qantas jet in the skies above Queenstown highlights the hazardous mountain terrain that confines our airspace and limits flight path options.

The mountainous terrain, changeable weather and high and constricted density of traffic, make Queenstown a challenging area to fly. As such, there is increased potential for accidents to occur." This statement was taken verbatim from the CAA’s 2016/2017 Annual Report.

Aviation accidents in the Queenstown area have the potential to damage New Zealand’s reputation for safe and secure skies, and as a tourist destination, as well as incurring unnecessary social cost.” This statement was taken verbatim from the CAA’s 2017/2018 Annual Report.

Dangerous icing issues in winter

The incident report copied below for the 737 makes very sobering reading. To clarify a few things in this report:

RNAV is a satellite GPS based system, independent of ground, used at ZQN, that allows aircraft to follow a non-linear (i.e. curved) approach to an airfield. To land, RNAV requires the pilots to have visual to ground from a minimum of 200 feet above the tarmac.

The navigation used at all other NZ airports is ILS (Instrument Landing System). When ILS has the optional safety extra Autoland fitted (as only Auckland does), a pilot can land in zero visibility. ILS cannot be used at Queenstown due to the necessary curved approaches from east and west to enable following the 3.2 degree approach (glide) angle.

Pilots have no instruments to detect icing other than a dumb metal stick poking a few inches out from their windscreen upon which they see ice building up - refer attached photo of an A320 icing indicator. Ice buildup does a number of things to an aircraft:

  • it adds an unknown mass to the aircraft (this can be many tonnes)
  • it can (dramatically) interfere with the airflow over the wings and destroy lift
  • it can stop various components on the wings from deploying or being able to be adjusted
  • depending on suspected severity it requires a manual intervention to increase flying and landing speed (typically 10 to 15 knots landing speed increase) - a problem on a short runway as ZQN is.
  • it can build-up at the rate of tonnes in seconds in certain conditions

Under icing conditions, the standard operating procedure for any commercial jet at most other airports is to reduce altitude to a hopefully warmer environment (this option is not available around ZQN due proximity of mountains). Pilots around ZQN have the options of either staying in the icing environment, or trying to climb back out through the environment that caused the icing in the first place, or praying. The chances of climbing back up through this environment are very slim. The 737 in the following report was able to manage a level go-around at 95% of full power. Loss of an engine at this time would have been catastrophic.

One of the key points here is that a different/relocated airport, with straight approaches, fitted with ILS and the optional safety feature Autoland, would give an aircraft in trouble, as this 737 clearly was, a fighting chance to make it to the ground in a single attempt. A go-around for a heavily iced aircraft is an extremely risky proposition, although not nearly as risky as trying to climb to a higher altitude.

Incident Report, CAA

Date: 1 September 2007

Location: ZQN, Queenstown

Aeroplane: 737-319


The aircraft was setup for Area Navigation approach for runway (RNAV) 23 approach into ZQN. We experienced severe icing on airframe with 25-30mm of ice on wipers. The aircraft also felt slow to respond to speed changes. With this amount of ice I felt RNAV canned speeds too low and flaps 10 speed interviene 180 knots a better choice. A level change go around was executed at minimum descent altitude due weather conditions, however aircraft struggled to maintain speed and track. Bugged up to 170 knots mode control panel to barely maintain 150 knots. Aircraft also diverged outside of base turn track to 0.2 nm, this even with speed 140-145 knots. We commented to each other that we may experience a ground proximity warning system warning. As aircraft was struggling in go-round (GA) climb manual thrust intervention was required to 95%N1* to maintain speed. Aircraft would not have had enough performance to carry out a single engine GA.

*N1 is a measure of the speed of the low pressure compressor and turbine - in simple terms, the amount of power the engine is producing.

Civil Aviation Authority Reports

Queenstown Airport is singled out by the CAA

The CAA annual reports over the last 10 years show a clear trend of increasing concern regarding safety at Queenstown Airport. Of particular significance, these same reports make no mention of in-air safety at any other airport in New Zealand during this whole decade.

CAA Annual Report 2012

We have conducted a comprehensive risk review of air transport operations at Queenstown to help guide the Authority’s regulatory approach to operations at this aerodrome.”

CAA Queenstown Airspace Classification Review 2014

Given that there are now significantly more passengers in the (Queenstown) airspace at any one time than ever before and greater numbers of aircraft than before, the exposure risk of passengers to an airspace safety occurrence has increased markedly.

CAA Annual Report 2015

The current air surveillance system supporting the air traffic management system is operated by Airways. It consists of primary and secondary radars and a multilateration system based in Queenstown. The current radar system will be at the end of its life by 2021.” (FYI - Multilateration is a navigation and surveillance technique based on the measurement of the times of arrival of radio waves having a known propagation speed).

CAA Annual Report 2016

Queenstown airspace has a variety of flying activities, mountainous terrain, changeable weather and a high density of traffic; all of which create a challenging operational environment with an increased potential for an accident to occur.” The key phrase I wish to emphasise from the 2015/2016 extract is “high density of traffic”.

CAA Annual Report 2017

Queenstown Operations – We conducted a gap analysis of the effectiveness of current controls, created a stakeholder plan and engaged with stakeholders to precisely define the risks associated with Queenstown operations. Pleasingly, there were no major safety occurrences during the year, and analysis determined that current controls are effective.” [Our emphasis]

The mountainous terrain, changeable weather and high and constricted density of traffic make Queenstown a challenging area to fly. As such, there is increased potential for accidents to occur.”

CAA Annual Report 2018

Aviation accidents in the Queenstown area have the potential to damage New Zealand’s reputation for safe and secure skies, and as a tourist destination, as well as incurring unnecessary social cost.” 

Queenstown Airport relocation to wide open valleys with safe flight paths

Safe WIde-Valley Options Are Available

Relocation of the airport would be the single most sensible thing that could be done to improve its safety and reduce risk. We have available within one hour's drive from Queenstown several potential locations that offer wide long valleys to provide straight unimpeded flight paths, regular descent and climb trajectories, more stable wind and weather conditions, and longer runway potential with unrestricted RESA zones.

Risk of serious accident or simply of frustrating weather delays and diversions could be dramatically reduced.