Home / Opinion / Online-views /  Mohan Ranganathan | Weathering flight frights

The recent crash of Air Asia Flight QZ8501 and, before that, of Air France’s AF447 in 2009 highlight the need to understand and negotiate large thunderstorms.

Both involve Airbus aircraft. Although the planes have a very high degree of automation protections built in, the crashes have exposed the dangers of extreme flight envelopes, combined with a lack of understanding of weather conditions and crew misinterpretation of flight instruments. Both have occurred in the ITCZ (intercontinental convergence zone) area—a belt of converging trade winds and rising air that encircles the earth near the equator.

Satellite weather data in both events indicates thunderstorms that rose beyond 40,000 feet (ft). One would hope that the Indonesian authorities do not suppress any of the findings of the digital flight data recorder (DFDR)/cockpit voice recorder evidence.

In the AF447 accident, the cockpit was manned by two
co-pilots at the time of the weather encounter. The lack of experience in interpreting weather radar data and the overuse/misuse of automation resulted in stalling of the aircraft and loss of control. It took several months to retrieve the recorders and analyse the crew actions. Did the aviation world learn a lesson from that event?

The QZ8501 crew was experienced, but its crash brings to the fore the importance of proper training and knowledge of weather flying. There were several aircraft flying in the area between 32,000ft and 38,000ft. The analysis of DFDR wind and temperature data and weather assessment of the crew from all those aircraft would indicate the kind of weather conditions prevailing in the area. It is obvious that there was one isolated huge thunderstorm cell—if QZ8501 alone experienced such a high updraft. The initial report by the Indonesian authorities that the aircraft climbed at an abnormal rate before stalling is a clear indication that the experienced crew had misinterpreted the weather radar indications and the autoflight system inputs.

Data indicates the flight climbed rapidly from 32,000ft to 38,000ft at more than 6,000ft per minute. In a very strong updraft, this is achievable. The drop in horizontal acceleration and the stall is an indication that crew lost control of the aircraft due to misinterpretation. The aircraft would have been on autopilot with altitude hold mode when they were deviating left to avoid weather. Encountering the updraft and the rapid climb would have resulted in the autopilot pitching the nose down to regain altitude. The combined pitch down and updraft would have increased the indicated speed and not dropped the speed. Only the DFDR would indicate the crew action. Did they disengage the autopilot and try to raise the nose to bring the speed down?

Stalls can take place even at high speed if the body angle is far too high. At high altitude, it is important to “unstall" the wing. That is the priority. If the crew had tried to bring the speed down and ignore the pitch angle, the aircraft would have been placed at a very unstable condition.

The limited data that has been filtering out indicates that a mishandling of the situation is likely. Very strong updrafts occur only in the core area of a fully developed thunderstorm cell. The rate of climb of QZ8501 indicates that the aircraft encountered one. Did the crew misread the radar indication or is it a case of lack of understanding and experience in weather flying?

After the Air France Flight 358 overrun accident in Toronto while landing in heavy rain on 2 August 2005, the lead investigator had stated: “It is important to find what made the pilot do what he is not trained to do." Airlines appear to underplay adverse weather operations training in their quest to cut costs. Simulators can simulate only conditions that they are programmed to, but cannot be used beyond the limits of the 6-Axis system. High-altitude upset recovery training is also limited.

The actual conditions that aircraft encounter can only be done through experience and visual assessment.
Over-dependence on automation and underplaying training is a danger that airlines, especially in India and Asian regions, are faced with. Total experience does not replace actual experience in high altitude flying. High levels of experience in aircraft flying at lower altitudes cannot replace experience in high performance airline jets.

Airlines from India do operate in the ITCZ area and there is a big deficiency in adverse weather operations and high altitude upset recovery training here. Our cockpits are manned by inexperienced crew and the Directorate General of Civil Aviation (DGCA) has overlooked serious deficiencies in proficiency checks and training. There have been instances of examiner pilots fudging simulator proficiency training and check reports. In 2013, DGCA found more than 350 airline pilots flying with expired proficiency checks.

This mockery of surveillance audits is what resulted in the US Federal Aviation Administration downgrade of India. We have co-pilots with just 200 hours in light aircraft manning cockpits and captains with only 2,500 hours of experience (AirAsia captain had 20,000 hours). The startle factor when encountering adverse weather has already resulted in two Mayday calls by a private Indian airline—once in April 2011 on the Mumbai-Kolkata route near Nagpur and the other near Vizag on the Kolkata-Chennai flight, the following year. These are warning signs which we have been ignoring. To use Reason’s Swiss Cheese Model, the holes are lining up.

The writer is a former Boeing 737 instructor pilot and an aviation safety analyst.

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