No one heard Helios Mayday call

A DISTRESS signal sent out by Helios flight ZU 522 during its last minutes in the air fell on deaf ears, a Greek expert said in court yesterday.
Elias Nicolaides, a witness for the prosecution, said the Cockpit Voice Recorder (CVR) of the doomed Boeing 737-300 captured the voice of a man desperately calling for help, minutes before the jet smashed into hilly terrain outside Athens on August 15, 2005.
The airline, Helios Airways and its officers are on trial for “employing, and continuing to employ, unfit and inadequate pilots.” They face charges of manslaughter and reckless endangerment leading to the death of 121 people.
The man issuing the two ‘Mayday’ calls is believed to be flight steward Andreas Prodromou. The switch he used to make the calls has two alternate settings: one is for communicating with tower control, the other for contacting other aircraft (intercoms).
From the CVR data, it emerged that Prodromou had the switch on the intercom setting, meaning the calls for help should have been heard by other planes.
But according to Nicolaides, all the calls were in vain:
“Had this transmission been heard on any frequency, it would have generated a lot of chatter [among pilots], everyone would be trying to find out what is going on. But no one on the other flights heard,” Nicolaides said.
The CVR – which records sounds for 30 minutes in a loop – picked up sounds outside the cockpit, which indicate that someone – Prodromou – was trying to get in. The cockpit door is finally heard to open, Nicolaides said.
Next a person is heard shuffling inside the cockpit, followed by the sounds of someone breathing through an oxygen mask. As far as can be determined, this individual was alone in the cockpit.
“The person who was talking had knowledge of airplanes,” added Nicolaides.
In addition to Prodromou’s frantic calls for help, the CVR recorded warning horns inside the cockpit, such as the Cabin Altitude Warning, which sounds off when the cabin altitude pressure exceeds 10,000 feet.
In this model of aircraft, the cabin altitude warning sound is the same as the take-off configuration warning.
Nicolaides said the pilots had not realised that the alarm concerned the cabin altitude, otherwise they would have donned their oxygen masks and stop the climb immediately.
“The two operators [pilots] did not understand what was happening,” Nicolaides told the court.
Having completely misread the situation, the pilots disengaged the auto-pilot and decreased the engine throttle – standard procedure for problems with the takeoff configuration. As a result, the plane continued climbing, leading to the onset of hypoxia and loss of consciousness.
“There was nothing wrong with the plane,” Nicolaides said. “It just did what it was told to.”
The witness again referred to the outflow valve, which was incorrectly left in the manual position during takeoff, which led to the aircraft not pressurizing during flight. Not only did the two aviators fail to take notice of the incorrect setting during the pre-flight check-lists, they also seem to not have checked the switch when the alarm began sounding – presumably because they were fixated with a (non-existent) takeoff configuration problem.
“People have died in the past in order for these checks to be in place,” Nicolaides remarked.
By default, the outflow valve switch is set to auto. “If it is not, then it’s not hard to spot.”
But by force of habit, one might expect the switch to always be on auto and thus not bother to double-check.
Moreover, shortly before takeoff the captain had signed off on the maintenance log, which indicated that the aircraft had undergone a pressurization test on the ground. This, too, should have alerted the captain to a pressurization problem once the warnings sounded in the air, said Nicolaides.
“The first thing he should have done was set the switch to auto and, if that did not work, they should have stopped climbing. No one wants to commit suicide. They just did not understand what was happening.”
The trial continues.