depressurization

Did Depressurization cause the crash of the Flight ZU522?

Sunday, August 21st, 2005, 12:05 p.m. (10:05 a.m., GMT) - ATHENS, Greece

Story:

When: Sunday, August 21, 12:05 p.m., 2005

Where: About 25 miles north of Athens

What: Helios Airlines Flight ZU522, a Boeing 737-300 carrying 115 passengers and 6 crew members crashed into hillside outside Athens

Some Technical details:

About 2 hours before the crash, Plane reported a problem with its air-conditioning system before entering Greek airspace

118 minute before the crash, the control tower at Athens International Airport was unable to establish communication with the plane

40 minutes before the crash, dispatched fighter jets approached the plane, reported that co-pilot appeared unconscious, the other pilot not in the cockpit, oxygen masks dangling inside the cabin; Fighter jets reported that the plane was flying in a gradually descending holding pattern, apparently on autopilot, at an altitude of about 34,000 feet near Athens airport.

A person banked the plane away from Athens, lowered it first to 2,000 feet, and then climbed back up to 7,000 feet before the plane apparently ran out of fuel and crashed

Autopsy results on 26 bodies showed that the passengers and at least two crew members including the co-pilot were alive when the plane crashed

A 5-year-old boy was alive for a second after the plane went down

Analysis:

There was no Rapid Cabin Depressurization

Basic concepts

Situation study:

------The F-16 pilots reported seeing someone in the cockpit, probably a man, took the control of the plane as is flew in a gradually descending holding pattern, apparently on autopilot, at about 37,000 feet near Athens airport.

It tells that pilots of F-16s could see through the windshields at an altitude of 34,000 feet. (Ceiling of B737-300 is 37,000 feet with normal cruise altitude of 34,000 feet. Some news reported 34,000 feet which makes more sense compared to 37,000 feet). Pressure difference between inside and outside, possible damaged caused by depressurization and deteriorated aerodynamic can cause bulk hull to severely buffet, especially in case of rapid depressurization.

------Apparently on autopilot

With autopilot on, the plane always fly stably and accurately as designated by pilots commands. Pilots give command by input to a certain panal called MCP (Mode Control Panel), or FMC/CDU, depending on what modes the autopilot is flying with. Pilots don't touch control wheel/column with autopilot on. As it reported “apparently on autopilot”, the plane is supposed to fly perfect holding pattern which is not very easy for a pilot to fly that perfectly.

The man taking control of the plane was obviously a pilot from what he was doing (Although what kind of type rating is not known, which makes big difference.) News reported so too. However, if depressurization happened, what he was supposed to do is to do Emergency Descend to a safe altitude instead of “gradually” descend in a holding pattern.

The 3 possibilities are, 1, Tthere was no depressurization; the reason for his descent is he tried to land, not because of depressurization. 2, There was depressurization, but it was not serious enough to get him into trouble without wearing oxygen mask walking from passenger cabin to cockpit, whereas it was almost fatal to the co-pilot who was reported lost conciousness some time ago (if depressurization was responsible for his incapacity). Furthermore, he didn't know exactly what to do in this case; 3, There was serious depressurization, but being lack of oxygen and the thrilling cold didn't kill him; he didn't know exactly what should be done to deal with the problem.

------40 minutes before the airplane crash, the fighter jets approached plane, reported that co-pilot appeared unconscious, the other pilot not in the cockpit, oxygen masks dangling inside the cabin.

Pilots are supposed to watch the cabin pressure closely during flight, especially when there is an ongoing problem with air condition system or pressurization system itself. Pilots have pressurization indication in cockpit, and they use separate oxygen system and masks from the cabin ones. A horn sounds when cabin altitude reaches 10,000 feet, and at 14,000 feet, cabin passenger oxygen masks automatically drop. Cabin oxygen masks can also be manually deployed by a toggle switch in cockpit.

As it mentioned above, there should have been a horn warning pilots about the cabin pressurization problem when the pressure reaches to a level corresponding to the altitude of 10,000 feet, before it dropped to a dangerous level of 14,000 feet when cabin oxygen masks deployed for the safety of passengers. In case auto feature fails, it should be manually deployed from the cockpit by pilots.

As it to pilots, they have a separate oxygen system which ensures their own safety.

According to the Boeing authorized procedure and the memory checklist for cabin Depressurization, the first few steps are as followed:

Cabin Depressurization Procedure

Left Seat

Right Seat

OXYGEN MASK on, set the regulator to 100%

Crew communication established

PA and FASTEN SEAT BELT on

Pressurization, select MAN-DC to fully close outflow valve, monitor pressurization system operations

Controllable or not

(If pressure continues to decrease) report "unable to control cabin pressure"

Passenger Oxygen Switch set ON

Declare EMERGENCY DESCENT

Clearly, the first thing pilots are required to do is to put their own Oxygen Masks On!

Though it was reported co-pilot was unconscious, captain missing from his seat, and passenger oxygen masks dangling in the cabin!

Provided both trained pilots on duty were qualified. During depressurization, even if co-pilot was unconscious, he was supposed to have had oxygen mask on. Captain too, with mask on, seat belt on in his seat! There could be no excuse for the captain to stay away from his seat before landed, especially while experiencing a emergency situation.

Here come the questions: If there was indeed a depressurization situation, Why didn't co-pilot wear his oxygen mask before lost conciousness? Where was the captain? (or even, where is the captain at this moment, or during this period? since all attempts to discover the body of the captain ended with no result.)Why the airplane didn't seem to do any emergency descend?

A man was reported trying to take the control of the airplane from 37,000 feet. If there was depressurization and without a mask on, this man could keep conscious for no more than a few seconds. Even if we may extend his extraordinary endurance to a few minutes. Apparently he must have been keeping conscious long enough to make his way to the cockpit under the extraordinary panic and suffocating.

The conclution that depressurization was the cause of the crash is suspicious.

...A man... take control of the plane as is flew in a gradually descending holding pattern, apparently on autopilot

It did not mention in which modes the autopilot was flying on. Obviously it was not quite possible for the F-16 pilots to see much of the details from outside although autopiloting was reported. If the flight plan was well programmed and autopilot was in the right modes, the plane should have been able to descend in the right path, and it should have adequate fuel, but all of those never happened. According to what was reported in news, the airplane was flying in a holding pattern, it flew for an extended period of time, and crashed after running out of fuel.

Too many important technical details are not available to public. Still, there are too many whys, and these whys are the cause of the dizarster.

Fact Sheet:

(takes off?????)

9:00 am. Helios Airlines Flight ZU522, a Boeing 737 carrying 115 passengers and six crew members, takes off from Larnaca International Airport in Cyprus, heading for Prague, Czech Republic, with a stopover in Athens.

9:37 am. Plane enters Greek air space, identified by Greece's Civil Aviation Authority.

10:07 am. Control tower at Athens International Airport unable to establish communication with the plane.

10:20 am. Air traffic controllers notify Cypriot counterparts who say plane reported a problem with air-conditioning system before entering Greek airspace.

10:25 am. Greek Civil Aviation Authority notifies Defense Ministry's national search and rescue center.

10:30 am. Defense ministry issues a Renegade alert, standard aviation procedure when planes fail to respond to control tower.

10:55 am. Two F-16 fighter jets scramble to locate airliner.

11:20 am. Fighter jets make visual contact with airliner over Aegean island of Kea, but unable to communicate with pilots.

11:25 am. Fighter jets approach plane, report that co-pilot appears unconscious, other pilot not in cockpit, oxygen masks dangling inside cabin.

12:05 pm. Airplane crashes near town of Grammatiko, into hillside outside Athens, about 25 miles north of Athens, killing 121 people. about 25 miles north of Athens.

(FOXNews.com link?)

News Report by FOXNews.com:

(a link to foxnews)