Hi there.
These Pitot problems have been known for decades. In the late 80s and the early 90s, there was already problems with water/humidity accumulating in the hoose between the probe and the ADR leading to biased airspeeds on Airbuses (and the Boeings may have had their problems too ?). Then Airworthiness directives in the early 2000s to replace the former Sextan (now within Thales) and Rosemount probes by the new models of Thales and Goodrich probes were released, without lasting results, the Pitot obstruction problems reoccurred despite the replacement by the new probes. And the last case between Paris and Rome suggests that a new replacement by the new Thales Pitot probes will not make it. Then let's do what the pilot unions demand, let's buy the new Goodrich probes while Thales prepares a new generation of Pitot probes specifically designed to cope with *increased anti-icing specifications*: if the existing Thales probes already met these specifications (and even more) and if the process of certification does not guarantee that the probes operate in a satisfying manner in real life, then let's review/alter the specifications themselves. The climate change also possibly impacts the high altitude. Maybe they should also include a criteria which says that the performances met during certification should be maintained over a XX % performance level, over YY month, with a ZZ % probability ? (given a specified maintenance process). This would be a way to specify a probe resistance to gradual pollution and obstruction.
The Pitot probes have suffered drain hole defects in the past, partly due to the manufacturing process and susceptibility to corrosion, making the probe vulnerable to pollution.
Similar problems were also observed on the fleet of Mirage 2000:
http://www.defense.gouv.fr/defense/c...2004-001-A.pdf
See page 55.
Within the Mirage 2000 fleet, the Pitot drain pollution was observed on 30% of the Mirages, 60% in hot/humid areas. Seemingly, this drain gradual obstruction by varied pollutions could make the probe more vulnerable to icing conditions. It was 5 years ago.
Now on he airliners we have at least two available probes:
http://www.goodrich.com/portal/goodr...t%200851HL.pdf
https://www1.online.thalesgroup.com/...sor_probes.pdf
One is designed to improve its anti-icing performance, the other is not.
Roughtly, Goodrich probes are on 2 planes over 3, and Thales probes on 1 plane over 3. Cathay's large fleet of planes has not known any problem with Goodrich (Cathay's saying) while Air France is struggling to make a census of its numerous unreliable speed past cases. Why does AF feel the need to establish an historical sensus of the "unreliable airspeeds" cases ? Is it the only way to get the attention of the manufacturers or the regulatory bodies ?
Jeff
PS) History: Technical Standard Orders from 1948 & 1951 about Pitots
Current Technical Standard Order
Current Technical Standard Order