IndiGo, GoAir follow A320Neo order

MUMBAI: The core problem which led to the grounding of Boeing 737 MAX aircraft worldwide has surfaced on the Airbus 320Neo as well. Both these aircraft have a tendency to pitch the nose up, excessively to an unsafe degree, during certain stages of flight.The big difference though is that unlike the Boeing 737 MAX, the A320NEO has never had an excessive pitch problem during flight operations. The problem came up recently only during laboratory testing carried out by the European aircraft manufacturer.But a wary European Union aviation regulator, which had certified the A320NEO safe to fly, has issued an interim directive asking airlines to load the A320Neo in such a manner that the tail-end stays comparatively lighter in weight. Which is why airlines like Lufthansa and British Airways have recently started leaving the last row of six seats vacant on their A320Neo.Unlike the European regulator, the Indian aviation DGCA (Directorate General of Civil Aviation) regulator hasn’t put out a directive in public yet. But to comply with the European regulator’s directive, airlines in India have started leaving the cargo compartment closest to the tail empty, said the director-general of civil aviation Arun Kumar on Tuesday.On July 31, European Union Aviation Safety Agency (EASA) issued an airworthiness directive, applicable to all A320Neo aircraft. Citing the problem, EASA said that an excessive pitch attitude (high nose) could result in increased workload for the pilots. "To address the potential unsafe condition, Airbus (the aircraft manufacturer) issued an Aircraft Flight Manual Temporary Revision, limiting the centre of gravity envelope, which prevents the aforementioned condition," said the EASA directive, which came into effect on August 14.What is an aircraft’s centre of gravity and how can it help in preventing an excessive high nose-up pitch? Centre of gravity is a point around which an aircraft balances itself. An aircraft balances like a see-saw, with its nose on one end and tail on the other. It is loaded with fuel, passengers and cargo in such a way that its centre of gravity remains within a prescribed range (area) through all stages of flight like take-off, climb, descent etc."If the tail-end is lighter than the nose-end, the aircraft will be nose-heavy and it will tend to pitch downwards. A heavy nose will counteract the excessive nose-up tendency of the A320Neo," said a senior commander.India is one of the largest operators of A320Neos with over 100 aircraft in operation. Director-general Arun Kumar said: "On August 7, we held a meeting with airlines and stake holders and asked them to implement the EASA directive. Three out of four Indian carriers that operate the A320Neo have already complied with the directive. These include IndiGo and GoAir. We will ensure that the fourth is in compliance by Wednesday."The A320Neo has five cargo compartment, he said. "Compartment 5, which is near the tail end is being kept empty. Compartment 3 and 4 are loaded less and compartment 1 and 2 which are near the nose are loaded more," he said adding that carriers like Lufthansa and British Airways have 32 row of seats. "Our A320Neos only have 31 rows of seats and so the last row is not being kept vacant, instead the adjustments are done in the cargo compartment," he added.Senior pilot Capt Amit Singh, Fellow Royal Aeronautical Society, London said: "A safety management system mandated safety risk assessment needs to be carried out to identify possible complications when a new procedure is adopted." He added that self regulation was an issue which came under criticism in the B737 Max MCAS certification as well. The onus of means of compliance for the directive issued by EASA regarding the A320 NEO pitch issues has been left on the airlines."The directive to limit the centre of gravity of A320Neo is temporary. It will be in effect till the aircraft manufacturer makes changes to the aircraft software to increase the efficiency of the "angle of attack" protection. Angle of attack is the angle at which the wing of the aircraft is incident to the oncoming relative airflow. A nose-up pitch increases the angle of attack, which increases the lift acting on its wings, which is why aircraft take off and climb with a nose-up attitude.But as the aircraft nose goes up, speed goes down. An excessively high nose could stall the aircraft. To prevent a stall, the aircraft computer has an angle of attack protection, which ensures that the aircraft stays within safe angle of attack limits throughout the flight.EASA directive said: "Analysis and laboratory testing of the behaviour of the flight control laws of the A320neo identified a reduced efficiency of the angle of attack protection when the aeroplane is set in certain flight configurations." An excessive nose-up pitch would move the centre of gravity of the aircraft beyond the maximum permissible limit.