Here's the latest article online from the Cyprus Mail:
An eerie echo of the Helios crash
By John Leonidou
AIRLINE manufacturers Boeing were fully aware long before last Summer’s Helios Airways crash that warning signals over cabin pressurisation problems could be confusing to the crew, according to emails from the company seen by the Sunday Mail.
Helios Airways flight ZU 522 crashed into a mountainside just north of Athens on August 14, 2005, killing all 121 passengers on board. Though the official accident report is still pending, there are strong indications the pilots were confused over warning signals indicating a gradual loss of pressure in the cockpit. Not realising there was a problem, they eventually passed out, leaving the plane to fly on auto-pilot until it finally crashed three hours later.
“Had there been a proper warning system that would have alerted the crew directly to the problem then it is my belief that the whole tragedy would have been avoided,” a Boeing pilot told the Sunday Mail this week.
Two and a half years earlier, a Norwegian airliner experienced almost identical problems to the Helios Airways plane. On November 29, 2002 a Braathen Airline Boeing 737-700 was forced to descend and make an emergency landing just after takeoff after pressurisation problems similar to those in the Helios case. The Braathen pilots, however, realised the problem and brought the plane down safely, and the company immediately reported the problem to Boeing.
In their report to Boeing customer service headquarters in Seattle, Braathens said the pressurisation problem “was not the ‘normal’ ‘rushing air’ associated with a rapid decompression, because the leakage was not of a rapid type”.
Preliminary investigations into the Helios crash show a slow decompression leak resulted in the pilots passing out.
In the Braathens incident, just as in the Helios tragedy, the problem was compounded by confusion over warning signals: “The warning horn [for high cabin altitude] is the same that is used for the takeoff warning, both with intermittent aural warnings. This led the flight-crew to not identify cabin altitude problems at once.”
Replying on December 9, 2002, Boeing said it had received “an increased number of reports of flight crews not configuring the pressurisation panel correctly”. But it also admitted it had received “similar comments from a number of airlines” regarding the confusing warning signals, adding, they would be proposing an optional system to fix the problem in about two or three years.
“The high cabin altitude warning horn itself has not changed since the 737 first delivered in 1967,” Boeing said. “However, in response to your comments and similar comments from a number of airlines, we are considering development of a limited crew messaging system for the 737NG.”
According to David Learmount of Flight International, as well as two Boeing pilots, this system has yet to be introduced, although Boeing did send out a circulate a “reminder” to flight crews about the difference between warning alarms for incorrect takeoff configurations and cabin altitudes – after the Helios Airways tragedy of August 14, 2005.
Several teams of foreign lawyers have offered to represent victims of the accident in suing Boeing in the US courts.
A BOEING 737 pilot, who wished to remain anonymous, yesterday told the Cyprus Mail that the problems experienced by the Norwegian airliner were “not identical, but very similar” to those on Helios. He insisted the tragedy could have been avoided had Boeing installed proper alarms to warn the crew of pressurisation problems in the cabin.
“From what we know so far about what went wrong with Helios, it appears that the pack and bleed switches were in fact on, but that the pressurisation switch was on manual. This is not identical to what happened in the other flight, but very similar, and had there been a proper warning system that would have alerted the crew directly to the problem, I believe the whole tragedy would have been avoided.”
The pilot said he wasn’t surprised that Boeing had not changed the alarm system after receiving the letter from the Norwegian airliner.
“To change this alarm system is not as simple as some may think. It is not just a matter of changing a few buttons, but changing the whole philosophy of the airplane, which would basically mean retraining all Boeing crew around the world – and that as you can imagine will not be easy.”
Copyright © Cyprus Mail 2005