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Most pictures of airliner's nose sections show small dark tube- or fin-shaped instruments sticking out of the fuselage below the cockpit windows.

For example this Airbus A350 shows them well: A350 nose section Source: Airliners.net

Other airliners (737, A380, 787) carry similar instruments at the front.

I'm sure Google would be able to tell me if only I knew how to correctly phrase my question, but...

These instruments sticking out of the fuselage, what purpose do they serve?

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    $\begingroup$ I am not sure other planes have these. All of them have the instruments on the sides. But I don't remember seeing the ones in the centre anywhere else. $\endgroup$
    – Jan Hudec
    Commented Aug 18, 2014 at 15:26
  • $\begingroup$ Now seeing the answer, indeed, every aircraft has a pitot tube (here mounted on the AoA vane to improve precision at high AoA), most have AoA vane and the faster ones have total air temperature probe (needed to derive Mach number), but sideslip vanes are not common. Most planes rely on a level or lateral axis of accelerometer in IRS for coordinating turns. $\endgroup$
    – Jan Hudec
    Commented Aug 20, 2014 at 8:06
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    $\begingroup$ Why is there a hatch above the (FO's?) seat? Emergency escape? $\endgroup$
    – CGCampbell
    Commented Aug 20, 2014 at 13:00
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    $\begingroup$ @CGCampbell Yes, the A350 is the first Airbus with an escape hatch in the roof. $\endgroup$
    – florisla
    Commented Aug 20, 2014 at 13:35

1 Answer 1

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Here's a better picture showing all probes, and labeled:

A350
Link to original, high-resolution, unnumbered picture

They are:

  1. Ice detector
  2. Multi-function probe 1
  3. Static port
  4. TAT probe
  5. Side-slip vane
  6. Pitot probe
  7. Angle-of-attack vane

Airbus.com has a PDF (pdf page 125) about the various probes.

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As the name suggests, the multi-function probes record different types of data. Here are more details:

The piloting of any aircraft involves knowing the relative speed of the aircraft with respect to the airflow surrounding it, that is to say to the relative wind. This speed is determined with the aid of sensors of the static pressure Ps, of the total pressure Pt and of the angle of incidence “alpha”. “Alpha” provides the direction of the speed vector in a reference system tied to the aircraft and Pt-Ps provides the modulus of this vector. The three aerodynamic parameters therefore make it is possible to determine the speed vector of an airplane.

These are covered by a US Patent.

Someone asked a similar question here.

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  • $\begingroup$ #5 is a upgraded yaw string, invented by the Wright Brothers, and used on their 1902 glider. upload.wikimedia.org/wikipedia/commons/5/50/… $\endgroup$
    – rbp
    Commented Dec 26, 2014 at 22:40
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    $\begingroup$ @rbp It looks awfully inconveniently positioned; I can't imagine it's very easy for the pilot to see in-flight, especially during maneuvering. $\endgroup$
    – user
    Commented Apr 16, 2018 at 11:24
  • $\begingroup$ @MichaelKjörling All the marked items are merely sensors that feed data into the avionics. The data is then calibrated (no sensor is 100% accurate) before being displayed in the flight deck on the instruments. $\endgroup$
    – ioctlLR
    Commented Apr 16, 2018 at 14:41
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    $\begingroup$ @ioctlLR Yes, my previous comment was tongue in cheek. I guess I didn't make that sufficiently clear. $\endgroup$
    – user
    Commented Apr 16, 2018 at 14:59

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