Kikapu wrote:Paphitis,
Can you give us your take on the Air France Flt. 447 crash please.!
Thanks.
All modern airliners are equipped with Weather Radar which indicate areas of thunderstorm activity and severe turbulence. These areas will appear on the radar as blotches of red, with less severe patches of cloud appearing as blue, green and yellow. Pilots will endeavor to avoid the red areas by diverting around the thunderstorm cells.
Cumulonimbus Clouds, found within thunderstorms, are particularly dangerous. The severity of the turbulence found within these clouds can cause structural damage to the aircraft.
Clear Icing (sheets of ice) will also form on the aircraft's fuselage and control surfaces which alter the aerodynamics of the aircraft and its flight characteristics. The wind shear, updrafts and downdrafts can be so severe it could result in the aircraft gaining and losing as much as 5,000FT. Microburst (downdraft) activity beneath the clouds anvil, but usually encountered when flying underneath Cumulonimbus clouds can be so strong it could push the aircraft into the ocean.
There were thunderstorms reported in the area immediately prior to the unfortunate accident. There were embedded Cumulonimbus Clouds up to a height of 53,000FT, which is fairly unusual as most Cumulonimbus cells anvil out at around 35,000FT.
It will be interesting to analyze the flight crew's decision process since they chose to press on or not divert. In order for this to happen, the Cockpit Voice Recorder must be retrieved. This does not mean that I consider the flight crew to be at fault, because I fully understand that getting caught within severe weather conditions is something all pilots experience. Fortunately, most live to tell the tale.
Furthermore, lightning strike is a most unsatisfactory explanation for the cause of this accident. Most aircraft are struck by lightning at least one time every year. Most aircraft are an aluminum hull (some other aircraft have composite hulls such as the Airbus A330) and this forms an excellent Faraday's Tube when hit by lightning. However, all VHF, UHF and HF antennas are attached along the aircraft's fuselage, and the electricity will travel down these antenna and through all VHF, UHF and HF radio systems thus completely frying out the radios circuitry. This will result in communications failure, but is still not an aircraft threatening event.
As stated above, thunderstorm activity and Cumulonimbus Cloud can place the aircraft within grave danger. Being struck by lightning does not. An ACARS (telemetry) transmission was received by Air France Maintenance Control informing them of some electrical malfunctions.
So what is known about AF447?
Attached above is the ACARS automated transmissions.
From the ACARS transmission (telemetry message) we know that the following systems had failed:
34-22-25 - INDICATOR - ISIS (INTEGRATED STANDBY INSTRUMENT SYSTEM)
34-43-00 - TRAFFIC AND TERRAIN COLLISION AVOIDANCE SYSTEM
34-12-00 - AIR DATA/INERTIAL REFERENCE SYSTEM (ADIRS) ((ADIRU & CDU))
34-10-00 - AIR DATA/INERTIAL REFERENCE SYSTEM (ADIRS)
27-90-00 - ELECTRICAL FLIGHT CONTROL SYSTEM (EFCS)
22-83-34 - FMGEC (FLIGHT MANAGEMENT, GUIDANCE AND ENVELOPE COMPUTER)
22-62-00 - FLIGHT ENVELOPE COMPUTATION
22-30-00 – AUTOTHRUST
27-23-00 - RUDDER AND PEDAL TRAVEL LIMITING ACTUATION
27-93-00 - FLIGHT CONTROL PRIMARY COMPUTER (FCPC)
34-11-15 - PROBE – PITOT
27-93-34 - FCPC (FLIGHT CONTROL PRIMARY COMPUTER)
21-31-00 - PRESSURE CONTROL AND MONITORING
27-91-00 - OPERATIONAL CONFIGURATION (F/Ctl Altn law)
So What Might of Happened?
AF447 knew there were severe thunderstorms along its route. They also knew there was a gap between these Cumulonimbus (CB) Cells and probably decided to press on. They would have been relying on their Weather Radar to divert around the CB cells. As is so often the case, the developing CB formations could have closed in from behind, thus encircling AF447. Because AF447 was encircled with CB formations thus committing itself with proceeding to Paris and with no other choice but to fly through CB thunderstorms. Once the aircraft penetrated CB cells, they would have encountered severe turbulence and wind shear. The moist atmosphere would result in
Clear Ice build up along the control surfaces.
Pitot Tubes are heated with Anti Ice Bleed Air from the engines, but they too iced over(?) causing ADR discrepancy. Auto pilot and auto throttle shut down. According to ACARS, there was a
pressure control malfunction suggesting the possibility of rapid decompression instinctively forcing the pilots to initiate an emergency descent. They need to be below 13,000 feet when depressurised without oxygen. This would mean that the aircraft is now well within the most violent heart of the storm, where microburst is the most horendous. Severe CB turbulence could also have resulted in structural malfunction or loss of control. At some point the aircraft was struck by lightning, but this did not cause the aircraft to crash.
