Mock drill mess up in Plane

Check pilot's prank nearly crashes Jet flight Manju V, TNN 2 December 2009, 09:47am IST Text Size: | Topics: Flight Pilot Plane Jet Airways MUMBAI: A Jet Airways flight coming in to land in Mumbai in October lost height faster than the prescribed rate of descent as the auto-pilot Twitter Facebook Share Email Print Save Comment Related videos More Videos » tripped, the flight director disappeared and the ground-proximity warning system went off. The flight finally landed safely — with none of its passengers hurt or even aware how close they had come to disaster, but for the experienced pilot and tons of luck. ( Watch Video ) The dangerous turn of events began — about 3,700 feet above the ground — when a check pilot, seated behind the commander and the first officer on the Jet AirwaysDelhi-Mumbai flight, pulled out a circuit-breaker. He did it ostensibly to check the pilot's ability to handle an emergency. Only, such checks are always done in simulators — never with a plane load of people. The unthinking act set off a chain reaction, tripping the autopilot, making the flight director indications disappear and turning off the ground-proximity warning system. The aircraft went sinking at a rate faster than the maximum prescribed descent of 1,000 feet per minute over the hills behind Jarimari, Andheri, but — despite all this — the aircraft managed to make a safe landing. Jet Airways has ordered a probe. But it has not derostered the check pilot though both aircraft manufacturers Boeing and Airbus have a strict policy warning flight crew against use of circuit-breakers during flight — they are not pulled even on a check or a test flight. A Jet Airways spokesperson said: ``The flight had a normal approach and landing, carried out safely within the acceptable parameters. An internal inquiry is in progress.'' But inquiries and investigations are not carried out for flights that are ``operated safely within the acceptable parameters'' and an exceeding high sink rate is not an acceptable parameter, say aviation experts. The matter is over a month old but the inquiry is still in progress and no action has been taken against the pilot concerned. The Directorate-General of Civil Aviation too has initiated an inquiry. ``I will be able to comment only after I have the facts from the air safety department,'' director-general Nasim Zaidi said. When the commander was interrogated, he said (and gave it in writing) that after the aircraft landed, the ACM revealed to him that he had pulled out the circuit-breaker on Radio Altimeter 1 ``just to see his reaction to failures''. The incident took place on October 20 on flight 9W 332 around 8.50am, during the morning peak hour. The check pilot was flying as an additional crew member (ACM) in the jump seat located behind the pilots' seats. An ACM's status is that of a passenger and s/he is not supposed to touch the flight controls. ``The aircraft was established on the Instrument Landing System (ILS) for runway 27,'' an official said, implying the aircraft was coming in to land from the east and was about 3,700 feet high and had got visual guidance to help it descend and touch down on the runway 27 centre line. ``At that instant, the autopilot tripped and the flight director disappeared,'' he added. A flight director gives visual cues to the pilot who follows it by, say, turning left or right or pitching the aircraft up or down to take it to its destination. So, with both vital navigation instruments failing, the commander took over the flight controls to bring in the plane for landing entirely manually. ``But the aircraft started sinking fast. It was going down faster than 1000 feet a minute, the maximum prescribed descent rate. It was a dangerous situation as the approach to runway 27 was over hilly terrain,'' the official said. When an aircraft has a higher-than-normal descent rate, the enhanced ground proximity warning system (EGPWS) blares out a loud aural warning, ``sink rate whoop whoop pull up'' continuously till the descent rate is slowed down. But no such alarm went off in this cockpit. ``A pilot can do the job of an autopilot; he can land, albeit with difficulty, without the help of a flight director. But neither can he nor any other instrument in the cockpit do the job of an EGPWS,'' said the source. It is such a critical equipment to prevent crashes that the International Civil Aviation Organisation mandates that no passenger aircraft should fly without a functioning EGPWS. Jet Airways confirmed that the EGPWS warning was not received. This confirms a system malfunction or a deactivation of the system. ``Since the sink rate was very high, the Digital Flight Data Recorder showed up an `exceedance report', which was picked up by the airline's flight safety department after the aircraft landed,'' said the source. ``It is a very dangerous thing to do as pulling out a C/B can render unintended systems to fail, like the EGPWS failure in this case. No pilot would want to fly without an EGPWS,'' an official said. Aircraft manufacturers are so careful about C/Bs that these switches are not installed at locations easily accessible or even viewable from the pilot's seat. It is located behind the seat as Airbus and Boeing did not consider the possibility of an ACM pulling out a C/B. JET AIRWAYS' RESPONSE TOI: Has Jet Airways initiated an inquiry into the incident? Was the DGCA informed about this? Jet Airways: Yes the DGCA has been informed.The aforesaid flight had a normal approach and landing, carried out safely within the acceptable parameters. Yes, an internal inquiry is in progress. Q: What is Jet Airways' policy on pulling out CBs (when the aircraft is in the air and when there is no requirement to do so in the checklist)? Ans: We cannot comment at this stage, as the inquiry is in progress. Q: Does such an action amount to ``unlawful interference'' as the ACM, whose status is that of a passenger, interfered with the switches? Ans: As mentioned earlier, we cannot comment at this stage since the inquiry is in progress. Q: Has the airline initiated any action against the pilot concerned (the ACM who pulled out the CB)? Ans: Since the internal inquiry into the incident is in progress, we are unable to comment. Q: Did the pilots on that flight get an EGPWS aural warning when the sink rate was high? Ans: No EGPWS warning was received by the Pilots. ACCIDENT INVOLVING CIRCUIT-BREAKERS On 11 March, 1973, during a flight, the captain and flight engineer of National Airlines DC 10-10, out of boredom, decided to experiment and see what would happen to the autothrottle system if the circuit breakers which supplied power to the instruments which measured the rotational speed of each engine's low pressure compressor were tripped. They pulled out the C/B which led to engine overspeeding and destruction of the engine. Pieces struck the fuselage, breaking a window, causing rapid explosive decompression and a passenger was sucked out of the plane. The plane landed safely. HOW IMPORTANT IS AN EGPWS? An EGPWS prevents and aircraft from flying into a hill or into ground. Such type of aircrashes were so common that in the 80s and 90s that an acronym CFIT- Controlled Flight Into Terrain was created to describe it. Since 1990, more than 2,500 passengers and aircrews have died in CFIT crashes. Since only an EGPWS can prevent a CFIT, the International Civil Aviation Organization had set a deadline of January 1, 2003 for all passenger aircraft to be equipped with EGPWS. EGPWS, with its ``look-ahead'' function, provides early warning of looming impact with terrain ahead and below. No passenger aircraft flies without a functioning EGPWS. Twitter Facebook Share Print Email Save Comment Text Size:

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