Pitot Tubes interconnection

[mimmo1942]

In the past I was taught that: “In no case shall lines carrying pressure from two separate Pitot tubes be connected together” (see MIL-I-6115; § 3.2.2 Multiple Pitot tube Installation).
Now I find that in some ex-Partenavia (now Vulcanair) models (P68, AP68TP) there are the following configuration:
§ 2 Pitot tubes signals connected together with 1 IAS Indicator;
§ 2 Pitot tubes signals connected together with 2 IAS Indicator.
I never found anything on the subject in the various FAA’s Advisory circulars and/or certification rules (FAR 23/25, JAR 23/25, EASA CS 23/25).
Welcome to your comments on the subject, information on the flight behavior (Side slip) of the Pitot tubes connection and some literature that could help me in the right design of the flight instrument system.

[muduckace]

Redundancy = safety, direct pilot/-f/o systems allow for indication of error, another standby system allows for a logical idea of the failing system.

[Genghis the Engineer]

I don't know the specific aircraft but, from a certification viewpoint, it's probably just treated as a single tube that happens to have two holes.

So long as the combined system is calibrated as such, I can't see a particular problem, regardless of any US military regulations to the contrary. Almost certainly if one pitot were to block, that would throw the calibrations and create some variation in airspeed indication errors away from those shown in the aircraft manual. On the other hand, the situation is altogether more serious if the aircraft has only one pitot and that blocks!

The main issue, I'd think, with such a system is knowing whether a single pitot has become blocked between flights thus creating a system error which you might be carrying for considerable time if not detected.

Behaviour in sideslip seems likely to me to be neither better nor worse than any other aeroplane, depending upon the positioning of the pitots - poor behaviour of a pitot-static system in sideslip is usually down to poor static positioning rather than pitot issues.

G