447 - a summary

I think it will be while before we know what happened, this was posted by ZEKE on http://www.airliners.net/aviation-forums/general_aviation/read.main/4449113/#menu92

AF 447. A Summary
An Air France Airbus A330-200 registered as FGHCP took off from Rio de Janeiro – GIG – for Paris – CDG – at 22.03Z, on May 31st with 216 passengers and 12 crew members.It was proceeding via airway UN873 at Flight Level 350.It checked position INTOL at 0133Z , June 1st, and passed an estimate for TASIL at 0223Z.Brazilian authorities revealed that he flew out of radar coverage at 0148Z, maintaining Flight level 350.Around 0200Z, on a communication to Air France Operations, the crew indicated that they were experiencing “strong turbulence” as they approached the ITCZ.Between 0210Z and 0214Z, a quick succession of 24 maintenance messages reported a series of warnings to the crew, along with some advisory on several systems faults and some maintenance messages.The aircraft never transmitted a position report at TASIL and never checked with Senegalese ATC.A search and rescue operation was launched which led to the discovery of the airplane debris over a large area of the ocean.
FLIGHT INITIATION
In spite of lack of precise information, we can however estimate with a high degree of certainty that the flight took off at maximum take-off weight : 216 out of 219 seats were occupied and we know that a few passengers were refused boarding, which is normal SOP for keeping the weight within the structural limits.With that MTOW of 233 T, we can estimate the weight at the last transmission position at about 206 T.
AIRCRAFT PERFORMANCE AND ALTITUDE CAPABILITY
The airplane was well below its optimum flight level, hence its maximum altitude capability. There was no question on its buffet margins (No “coffin corner” situation for the ISA + 14°C conditions they both planned for and encountered).
WEATHER
According to independently studied weather situation, there was nothing unusual in both the position in latitude and in convective activity inside the ITCZ. Tim Vasquez, who made the most thorough analysis, identified some potentially very active cells in the vicinity of the planned flight track and the French Weather Office found that in fact the active Cbs in the area had already started their decaying phase around 0200Z.
ACARS MESSAGES
A summary was made public on June 4th of the received maintenance messages.It is to be stressed that :1/- They only concern the messages addressed to AF maintenance through an automated protocol.2/- They cannot in any case be regarded as equivalent to a DFDR recording.3/- For lack of an access to the complete digital coding of the reported faults, some interpretation could be erroneous.4/- The summary refers to 24 individual messages that have not been made public.Anyway, some attempts at interpretation have – and still can – be made as to the understanding of the technical aspects of the last moments of the flight.REPORTED SYSTEMS FAULTS
They are about Automatic Flight System, Flight controls system, Navigation systems and Air Conditioning & Pressurization.Prominently figuring in the list are the airplane’s ADRs or air data reference units. Some identified codes reveal that in all probability, the faulty channels are related to aerodynamic speed data, which made official services look into the origin of the data : the total pressure probes, better known as “Pitot tubes”, the more when it was revealed that a few incidents – some serious – with similar subsequent warnings have happened in the past. One of them, an Air Caraibes flight from Fort-de-France to Orly led the crew to a very difficult-to-manage flight situation (more later).
SEARCH AND WRECKAGE RECOVERY
Parts of the aircraft and some 50 bodies have so far been recovered, with the Brazilian authorities in charge of forensic medicine and the French dealing with the examination and treatment of the debris.So far, the priority has been given to the occupants of Flight 447, with some urgency acknowledged for the identification and localisation of the flight recorders, the “pingers” of which having a limited life.Very little is known about a precise location of the found and recovered parts of the aircraft.Of some notice are : the tail fin, the left inner spoiler, parts of the Crew Rest container, the forward twin jump seats and the doctor’s kit, the location of which are well known inside the plane.
PRELIMINARY CONCLUSIONS
Very few can be made with a high degree of certainty.However, if we concentrate on facts, we can derive the most likely picture of what happened in this cockpit up to the moment of the last transmission.These facts are :-A night flight in an area of active Cb cells, some likely turbulence, in and out of the main system’s cloud tops of cirrus and some heavy moisture.-A loss of indicated airspeed data, an auto-pilot disengagement leading to a manual partial panel flying with degraded flight control laws.
WHAT IS NOT KNOWN ?
Basically everything that happened after 0214Z, the time of the last transmission.At this stage, it is impossible to determine an in-flight structural break-up or a high-speed impact with the ocean surface.
READING BETWEEN THE OFFICIAL LINES
Most documents, published by Airbus Industrie or the BEA or the EASA seem to suggest that at least the loss of aerodynamic data – meaning either the Pitot tubes or the ADRs – could have been a contributory factor to this accident.We’ll have to deal with each aspect in order to keep some intellectual honesty in this accident study.As we are not privy to the complete documents or the findings of the investigation team, I’d like to repeat that our job is more of a sleuthing nature than an analysis of the complete access to the evidences. And even in that case, we are not trained in accident investigation.And I have to apologise for that proviso.

EY