AF 447 SIGNIFICANT EVENTS

AF447-significant-events 1

AF 447

SIGNIFICANT EVENTS


« The crews can inherit latent conditions created by people far removed in time and space from the event. »


ICAO

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October 1993: A330 certification with Rosemount Pitot probe

AF447-significant-events

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Décember 1995 : TFU 34.13.00.005. Airbus reports Rosemount probe defects due to inadequate certification and starts Goodrich probe development. Extracts :


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“STRONG CUMULO-NIMBUS (Cb) CONTAINING A HIGH DENSITY OF ICE CRYSTALS CAN BEEN COUNTERED, PARTICULARLY IN THE INTERTROPICAL CONVERGENCE ZONE (ITCZ). IN SUCH AN ICY AND TURBULENT ATMOSPHERE, THE A/C AIR DATA PARAMETERS (PRESSURE DEPENDANT) MAY BE SEVERELY DEGRADED, EVEN THOUGH THE PROBE HEATERS WORK PROPERLY.

IT HAS APPEARED THAT THE CHARACTERISTICS OF SUCH AN ENVIRONMENT COULD EXCEED THE WEATHER SPECIFICATIONS FOR WHICH THE PITOT PROBES ARE CURRENTLY CERTIFIED.

THE WEATHER SPECIFICATIONS (ICING/LIQUID WATER CONTENT/GUTLET SIZE) TO WHICH THE PITOT PROBES SHALL RESIST HAVE THEREFORE BEEN UPDATED WITH MORE STRINGENT REQUIREMENTS ON THE BASE OF THE FIELD EXPERIENCE AND RECENT EXTENSIVE FLIGHT TESTS.

AIRBUS HAS LAUNCHED THE DEVELOPMENT OF THE FOLLOWIN MODIFICIATIONS:

1.DEVELOPMENT OF A NEW PITOT PROBE ABLE TO MATCH THE NEW REQUIREMENTS. ALL FLIGHT TESTS AND WIND TUNNEL TESTS ARE NOW COMPLETED AND SUCCESSFULL : THE CERTIFICATION OF A NEW PITOT PROBE HAS BEEN OBTAINED EARLY IN NOVEMBER 1996 (NEW PITOT PROBE : P/N 851HL MOD 44836).”



« Keep in mind that the specification referencesare TSO C16 and AS 393


November 1996 : Rosemount probe replaced by Goodrich probe (Airbus mandatory)

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November 1998 : Rosemount probe replaced also by Sextant (Thalès) AA probe…


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August 2001 : French DGAC says these 2 replacements are mandatory with AD 2001-354(B) :



“ On november 25 2002, FAA said : “The DGAC advises that operators have reported several cases of loss or fluctuation of indicated airspeed when flying through heavy precipitation or freezing weather conditions. The probable cause has been attributed to the presence of ice crystals and/or water exceeding the weather limits for which the pitot probes are currently certified. Loss or fluctuation of indicated airspeed, if not corrected, could result in inadvertent excursions outside the normal flight envelope.”

« This Directive requires the installation of Pitot probes meeting more stringent qualification requirements, but... »


« …the specification references stay TSO C16 and AS 393 ! How was the Thales AA probe certified by french DGAC, taking into account Rosemount experiment ? !»

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Jully 2002 : OIT SE 999.0068/02/VHR. Airbus reports Thales AA defects. Extracts :


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“ THE AIM OF THIS OIT IS TO INFORM THE OPERATORS THAT SEVERAL SINGLE AISLE OPERATORS HAVE REPORTED AIRSPEED DISCREPANCY ON AIRCRAFT FITTED WITH THALES PITOT PROBES PN C16195AA.”

INVESTIGATIONS CARRIED OUT SHOW THAT BURRS CAN REMAIN IN THE PITOT PROBE AFTER DRILLING OF THE DRAIN HOLES. AS A CONSEQUENCE THE BURRS COULD ASSIST THE ACCUMULATION OF EXTERNAL POLLUTION AND CONSEQUENTLY COULD BLOCK THE DRAIN HOLES.”

THE CONSEQUENCE IS AN INCORRECT TOTAL PRESSURE MEASUREMENT LEADING TO AN INCORRECT AIRSPEED COMPUTATION. ”


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January 2005 : Thalès develops « ADELINE » research project. Extracts :


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The objective of ADELINE is to develop new architectures and technologies of air data systems for implementation in new aircraft on the horizon of 2010.

Actual air data equipment is composed of a large number of individual probes and pressure sensors. This equipment delivers vital parameters for the safety of the aircraft’s flight such as air speed, angle of attack and altitude.

The loss of these data can cause aircraft crashes especially in case of probe icing.


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August 2006 : Airbus SIL 34-084. Flushing interval is reduced from 2C to C check




« 21 months between 2 C checks ! Why did Airbus not reduce this interval any more ? »

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Septembre 2007 : EASA reports Pitot probe certification ETSO C16 is obsolete.






AS3931947 !


« EASA says ETSO C16 is obsolete and need to be updated but they do nothing. Why ? »



« Obsolete… »


« Equipments must function properlyin the full normal operating envelopeof the aeroplane »




« Hazardous means a large reduction in safety margins, excessive workload for the crew, serious or fatal injuries »

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September 2007 : Airbus recommends replacement of the Thales AA probe by the Thales BA probe, not mandatory.




« But one year later… »

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September 2008 : Airbus reports « the Thalès BA is not intended to support severe icing conditions » …



(Air France Info PNT n°5 extract)

« Air France and Airbus are discussing…»


« Air France does not replace AA probes by BA probes »

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Air France reports 9 precursor serious incidents between june 2008 and march 2009 (AA probes).



« One crew had reported MAYDAY on the frequency »« NO investigation by french BEA »« NO safety information by french DGAC »« Air France is still discussing with Airbus… »

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A few days before AF 447 accident, Air France starts replacement of Thales AA probes by Thales BA probes.


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june 1st 2009 : AF 447 accident


F-GZCP (Thales AA probes equipped)


« According to french BEA, the A330 was flying atFL 350 through the ITCZ (ice cristals) . Airspeed discrepancy was reported by ACARS. »

« According to EASA, inconsistent measured airspeed could be attributed to Thales AA Pitot probes faults in icing condition. »

« Hum… from our point of view, you may read can be attributed… »


« The consequence should be an inadvertent excursion of the A330 outside the normal flight envelope »


«In 2002, the excursion outside the normal flight envelope was identified by french DGAC as a consequence of the loss or the fluctuation of indicated airspeed »

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1GTurn *

Turbulence 1,5g

225 kts 275 kts

.Speed in

turbulence260 kts

.Maxi 1,7g

ISA+15

15 kts


* avoiding weather

As you can see, the flight envelope

is very limited


« AF 447 crew had not been warned of any problem with the weather »

(weather chart used by the crew)


AF447 flight plan

TASIL

« easy to avoid »


« He could have been warned by the CCO Air France 2 hours before reaching TASIL with that satellite view… »


(alternative routes)

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August 2009 : The Thales AA probe disappears (EASA)





« Too late for AF 447… »


« …because an unsafe condition existed with these Thales AA Pitot probes ! »




« AF 447 crew was not warned of that unsafe condition»

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August 2009 : EASA starts to modifie Pitot probes specifications. ETSO C16 modification :




« This is a safety priority, they say »




« The old AS393

disappears too »


« Too late for AF 447 ! »


« On october 2009, Airbus confirms that many modifications must be done to improve the Pitot probes reliability »



“The TSO C16 does not require the probes to be tested in ice crystal or mixed phase icing conditions despite probes being sensitive to such icing conditions.”

“A probe designed and tested in liquid icing conditions only may require a significant redesign to meet the ice crystal and mixed phase requirements.”

“Recent evidence indicates that the ice crystal and mixed phase conditions may not be adequate for pitot and pitot-static probes.”


« Airbus strongly recommends to EASA that a working group is established as soon as possible. »




« Remember ! In 2002, the french DGAC had advised that the probable cause of loss or fluctuation of indicated airspeed

can be attributed to the presence of ice crystals »


« After the AF 447 crash, the french BEA starts to investigate the precursor serious incidents »




« After the AF 447 crash, Air France continues the AA probes replacement and announces several measures including : »


-a specific flight simulator training “IAS discrepancy” -the position of long-range aircraft monitoring

-training materials about ice crystals

- the flights preparation

Again, too late for AF 447…

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April 1998, serious incident near Frankfurt. Heavy rain, severe icing conditions…




« The BFU madethat

recommendationin 1999 »


« What did they do with that recommendation ??? »


« On August 8, 1996, the National Transportation Safety Board issued that

recommendation : »



« What did they do with that recommendation ??? »



« States shall take the necessary measures to ensure that the safety recommendations are duly taken into consideration » »


« AF 447 crew had inherited latent conditions created by Airbus, DGAC, EASA, BEA and Air France. »


AF 447. REASON MODEL


« The AF 447 accident could have been avoided . »

Captain Gérard ArnouxCaptain Henri Marnet-Cornus (retired)

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AF 447 SIGNIFICANT EVENTS