Pitot Probe Limits

[Jetset320]

Does anyone know the limits when a pitot probe is considered to be in need of a replacement/service?

Recently, one aircraft (3 year old A320) has the forward three pitot probes heavily burned around the lenght heated part of the pitot tube. Other aircraft are nothing like this and I snag them each time, but next time I fly same aircraft, they are still there and I would'nt have seen what the engineers wrote in the tech-log.

Last time I called an engineer out and he said that they have no limits per se, but as long as the drain hole is not cloged and the orifice is uniform, its good to go.

These three pitots are like burned toast and have a scab that has fallen off in places, and though i am quite sure the pitot is servicible in the short term, I believe it must have a limit that is more scientific than described.

[spannersatcx]

This is what the Airbus maintenance manual says, it has no finite life it is on condition:

A. Inspection/Check of the Pitot Probe (9DA1,9DA2,9DA3)

(1) Do a general visual inspection of the Pitot Probe.

(a) Color

During the ageing of the probe, the color of the tube becomes brownish and/or blackish.
This coloration has no effect on the operation of the probe.
CAUTION: DO NOT USE SHARP AND/OR METAL TOOLS OR OBJECTS TO CLEAN THE PITOT PROBE. SUCH TOOLS OR OBJECTS CAN CAUSE DAMAGE TO THE PITOT PROBE.
(b) Internal Obstruction (b)

Make sure that pitot probe is clean, without obstruction.
If not, remove the pitot probe (Ref. AMM TASK TASK 34-11-15-000-001) , blow compressed air into the pitot tube at the pneumatic connector and out of the tube entrance.
Maximum air pressure: 57 psi (3.9300 bar) .
NOTE: The compressed air line must have an oil trap to make sure that no oil gets into the pitot probe.

Install the pitot probe (Ref. AMM TASK TASK 34-11-15-400-001) .
(c) Make sure that the drain holes are not blocked.

If not, do the flushing of the Total pressure lines:
- for pitot 1 and/or 2
(Ref. AMM TASK TASK 34-10-00-170-001)

- for pitot 3
(Ref. AMM TASK TASK 34-10-00-170-003) (only standby total pressure line part).

(d) If the inspection/check is not satisfactory, you must reject the pitot probe

[Piper19]

It's normal that they turn brown-black in time. I've seen these pitots like this most of the time, including the scabs.
But I don't think the engineer should say there are no limits as long as the holes are free... (altough I do believe him when he says it's a serviceable one). I found limits in my Boeing AMM, dealing with nicks, dents, scarfs and... especially important for burning and scabs: thickness of the intake lip. This last is a factor that is normal to every probe to increase over the years. Also flaring out is a thing I see quite frequently : go with your fingernail over the pitot intake part, it should be smooth.
Pitot tubes are not made specially for Boeing or Airbus (in fact most of them fit more than one aircraft type), so I think Airbus has the same matter in the AMM regarding limits.

Keep in mind that a normal preflight, daily and weekly check only involves the checks your engineer mentions (drain hole free, no visual damage and clogging).

[Jetset320]

Thanks for the info.

Its quite disconcerting to see them in that state when older aircraft's probes are in better condition. Perhaps they do change them after all!

[HAWK21M]

If the performance of the probe is not affected & the probe entry points are not damaged.....there would be no reason for replacement.
regds
MEL