EASA Safety Information Bulletin
SIB No.: 2009 - 17
Issued: 09 June 2009
Subject: Unreliable Airspeed indication
Background: During the recent accident of an A330 into the Atlantic Ocean
on 01 June 2009, and without prejudging the final outcome of
the investigation, a discrepancy between the different
measured airspeeds was reported. There have been a number
of occurrences of unreliable airspeed indications or misleading
air data information. The root cause of this may be due to, but
is not limited to, inappropriate maintenance, contamination by
small objects or materials on the ground or in the air, extreme
environmental conditions producing icing outside the
certification envelope of the probes or large amount of water
ingestion.
Description: The primary purpose of the pitot-static system is to provide the
flight crew with airspeed information, required to safely control
the aircraft. As noted above, the origins of potential pitot-static
system malfunctions are numerous and cannot be totally
excluded in the operational context. The Aircraft Flight
Manuals and/or Flight Crew Operating Manuals include
procedures for unreliable airspeed indication (Air data system
misleading information) and these should be well known by
flight crews. Correct application of these procedures by flight
crews may be crucial for assuring the safety of the aircraft
when such Pitot-static malfunctions occur.
Recommendations: Operators should ensure that flight crews have proper
knowledge and proficiency:
- To detect and to identify unreliable airspeed indication.
- To apply immediate and conservative actions for ensuring
short term safe flight control, in accordance with the
manufacturer procedures developed for the specific aircraft;
the use of memory items should be considered.
- To apply procedures for the safe continuation of a flight with
unreliable airspeed indication up to a safe landing.
EASA SIB No: 2009 - 17
This is information only. Recommendations are not mandatory.
EASA Form 117 Page 2/2
Familiarisation of flight crews with unreliable airspeed
indication procedures should be provided through adequate
training. Flight crew knowledge and proficiency should be
checked on a regular basis.
Applicability: All aeroplanes operating in commercial air transport.
Contact: For further information contact the Airworthiness Directives,
Safety Management & Research Section, Certification
Directorate, EASA. E-mail:
[email protected].