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issuing an Airworthiness Directive.
On 16 October 2008, EASA asked Airbus to give a review of the situation concerning
this problem at the ARM meeting to be held on 10 and 11 December 2008.
EASA answered by letter dated 18 November 2008 that an assessment of the
risk associated with the speed inconsistency problems was currently being
examined with Airbus and that it would inform DGAC of its conclusions.
At the time of the December 2008 ARM meeting, the “Pitot icing” theme was
on the agenda. Airbus presented 17 cases of temporary Pitot blocking that
had occurred on the long-range fleet between 2003 and 2008, including 9 in
2008 without being able to explain this sudden increase.
At the time of this meeting, Airbus indicated that recent events had not
provided any new information and that the fleet’s airworthiness was not
affected. The manufacturer maintained its position and proposed that EASA
keep the SB A330-34-3206 (Rev. n°01). This SB no longer mentioned the
improvement provided by the C16195BA probes in icing conditions. It was
decided to review the situation again at the next ARM meeting.
The situation was reviewed again at the ARM meeting held on 11 and 12 March
2009. No new cases of fl uctuation or loss of speed were reported. As a follow up
action EASA asked Airbus to make an annual review of problems of this type. The
Service Bulletin BS A330-34-3206 (Rev. n°01) was maintained as a recommendation.
On 30 March 2009, EASA wrote to DGAC saying that a detailed review of the
events for which icing of the Pitot probes was suspected had been carried out
with Airbus, and according to this analysis:
 the events reported in 2008 did not modify EASA’s position and these
events’ classification remained “major”;
 the increase in the number of these events recorded in 2008 could not be
explained at that stage and Airbus had been asked to draw up an annual
report to determine a trend.
In this letter EASA concluded that at this stage the situation did not mean that
a change of Pitot probes on the A 330/340 fleet had to be made mandatory.
1.18 Additional Information
1.18.5 System certification
1. 18.5.1 Regulatory aspects
The A330 meets the requirements of the regulations in force – that is to say
JAR 25 changes 13 or 14 and the special conditions imposed by DGAC – at the
time the type certification application was made.
The systems were developed in compliance with the regulatory requirements
defined in JAR 25 part F and, in particular, paragraphs JAR 25.1301, 1309,
1323 (d) (e),1326, 1419 and in the corresponding ACJs (acceptable but not
mandatory means of compliance).
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These requirements indicate in particular how this equipment must be
designed, installed and tested to verify it can ensure its function in all
foreseeable operational conditions.
Among other things, they state that:
 the systems must be developed in such a way that failures that would
prevent the flight from being pursued in complete safety are extremely
unlikely. Compliance with this requirement must be demonstrated by
means of analysis, and flight and ground tests, taking into account the
possible failure modes, their probability as well as their consequences on
the aircraft and its occupants;
 the systems and associated warnings must be developed while minimising
the risks of crew error;
 means of information must be put in place in order to alert the crew of the
occurrence of a failure and allow them to take the appropriate measures.
It is necessary to perform an analysis of the criticality of the failures and to
associate it to a probability of occurrence (ACJ 25.1309).
For the Pitot probes, the regulations also require that:
 they must be protected against humidity, dirt and other substances that
could alter their function (JAR 25.1323 (d));
 they must be fitted with a heating system designed to prevent any
malfunctioning due to icing (JAR 25.1323 (e));
 appropriate means must be provided (visual warning directly visible to the
crew) to inform the crew of any non-functioning of the heating system
(JAR 25 1326);
 they should be protected against the icing defined in appendix C of JAR 25
(see JAR 25 1419).
Appendix C of JAR 25
Appendix C of JAR 25 is the certification standard in super-cooled water icing
conditions for validating the anti-icing protection systems on aircraft. The
conditions are defined according to the altitude and temperature in terms of
water concentration and of the droplets’ mean volume diameters.
　
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