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Report: controller’s conflicting clearance causes collision during pushback at Tel Aviv
1 July 2019
Report: thrust setting for shorter runway causes Boeing 747-8F to rotate at runway end, Tokyo-Narita
ATSB issues recommendations for improved aircraft design tolerance to inadvertent dual control inputs
The ATSB has issued Safety Recommendations to EASA and aircraft manufacturer ATR seeking improved aircraft system design tolerance to inadvertent dual control inputs by pilots.
The Safety Recommendations are contained in the ATSB’s final investigation report into an inflight upset and inadvertent pitch disconnect experienced by an ATR 72 turboprop airliner on a flight from Canberra to Sydney, Australia, in 2014.
During that flight, as a result of a sudden decrease in tailwind, the ATR’s pilots unintentionally applied opposing control inputs to their control columns while trying to ensure the aircraft remained below its maximum operating speed. These differential forces activated the aircraft’s pitch uncoupling mechanism. Intended for activation in the event of one of the aircraft elevators being jammed, the pitch uncoupling mechanism resulted in a pitch disconnect, where the elevators could operate independently of each other.
With the pilots applying opposing control inputs and built-up tension within the flight control system, the pitch disconnect resulted in transient asymmetric elevator deflections, generating aerodynamic loads that exceeded the strength of the horizontal stabiliser, causing significant damage.
The aircraft landed safely and was inspected by maintenance engineers but the damage was not detected. The aircraft returned to service and operated a further 13 flights before a subsequent inspection after a suspected birdstrike found it had sustained serious structural damage to its horizontal stabiliser, which was subsequently replaced.
As part of its final report, the ATSB has issued a Safety Recommendation to EASA, recommending taking “further action to review the current design standard (CS-25) in consideration of effect that dual control inputs may have on control of aircraft.”
In addition, the ATSB has issued two Safety Recommendations to aircraft manufacturer ATR, recommending that ATR:
- assess the operational risk associated with limited tactile feedback between left and right control columns in the context of no visual or auditory systems to indicate dual control inputs; and
- perform a detailed review of the effects of dual control inputs on the aircraft’s longitudinal handling qualities and control dynamics to determine if there are any detrimental effects that could lead to difficulty in controlling the aircraft throughout the approved flight envelope and operational range.
ATSB calls for review of runway lighting standards following Boeing 737-800 runway excursion at Darwin
The absence of centreline lighting on a wider than usual runway was a factor in a serious runway excursion incident involving a Boeing 737-800 at Darwin Airport, Australia.
In December 2016, while landing on a wet runway at night, with visibility reduced by heavy rain, the Virgin Australia 737-800 touched down more than 20 m to the right of the runway centreline. The aircraft continued to the side of the runway, and its right landing gear ran just off the edge, destroying six runway lights along a 400 m path before returning to the runway. There were no injuries and only minor damage to the aircraft.
The ATSB found that a relatively small increase in crosswind had occurred at a critical time a few seconds before touchdown, and the crew were not aware how far the aircraft had deviated.
The two rows of lights alongside runway 29 at Darwin are further apart than what a flight crew would normally encounter, due to the relatively wide runway. The ATSB found that, in the absence of centreline lighting, this characteristic affected the crew’s ability to detect and correct the aircraft’s deviation.
While studying past reports of runway side excursions in reduced visibility, ATSB investigators discovered that a disproportionate number of them occurred on wider runways.
In response to the ATSB investigation, both the aircraft operator and airport initiated a number of safety actions, including providing flight crews with information about the specific risks of approaches to Darwin Airport at night in conditions with reduced visibility.
The International Civil Aviation Organization (ICAO) recommends, but does not mandate, the installation of centreline lighting on wider runways. Of the two runways wider than 50 m in Australia, Darwin’s runway is the only one without centerline lighting.
The ATSB previously recommended the installation of centreline lighting at Darwin Airport after a 2003 runway side excursion. Its concerns were renewed following a 2008 hard landing though no recommendation was issued.
Darwin Airport is a joint military and civilian facility – the Department of Defence owns much of the airport infrastructure, including the runways, while Darwin International Airport operates the civilian aspects of it. Both have advised the ATSB that the installation of centreline lighting will be considered during any future runway works.