12
$\begingroup$

Recently while I was on a flight, I've noticed this area near the front door on a Boeing 767 aircraft. I'm a total aviation noob, I just wonder what are these and what they are used for.

enter image description here

$\endgroup$
  • 1
    $\begingroup$ This is what can happen if the static ports get blocked. $\endgroup$ – TomMcW Oct 31 '18 at 13:09
  • 3
    $\begingroup$ There's already a detailed description at Wikipedia. $\endgroup$ – David Richerby Oct 31 '18 at 13:19
  • 4
    $\begingroup$ @DavidRicherby and you know we don't send people to wikipedia to look for answers $\endgroup$ – Federico Oct 31 '18 at 13:26
  • 3
    $\begingroup$ Possible duplicate of How does a pitot plate work? $\endgroup$ – M28 Oct 31 '18 at 14:23
  • 2
    $\begingroup$ @Federico The SE sites I spend most of my time on feel that it's not a productive use of anybody's time to write SE answers to just duplicate Wikipedia in a way that's less detailed and more likely to go out of date. I'll try to remember that Aviation doesn't see thing that way. $\endgroup$ – David Richerby Oct 31 '18 at 15:34
16
$\begingroup$

One of the standard instruments of an aircraft is a "Pitot tube". This instrument allows measurement of the forward air pressure as the aircraft moves through the air. By this measurement the instrument can estimate the relative air speed of the aircraft.

In order to make the measurement, the forward air pressure is compared to the side air pressure and the difference between the two is presumed to be due to the force of the aircraft moving through the air. Thus, the measurement is a relative one, comparing the forward air pressure to the air pressure on the side of the plane.

The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much as compared to the pitot tube which takes in air as the plane rushes through it, thus frequently changing according to the speed of the plane. The pitot tube is usually located on the bottom of the plane and is pointed forwards.

$\endgroup$
  • 1
    $\begingroup$ In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle); you're correct however, that the difference between the "ram air" pressure at the pitot port and the velocity-reduced pressure at the static port gives IAS. $\endgroup$ – Zeiss Ikon Oct 31 '18 at 12:58
  • 3
    $\begingroup$ Why are there there separate Static Ports for the Captain and First Officer? $\endgroup$ – unfa Oct 31 '18 at 13:15
  • 5
    $\begingroup$ @unfa Almost all instruments exist at least twice for redundancy. They are either manually (by the pilots) or automatically (by some computer) cross-checked against each other. That way, if one of them fails, you can still use the other to fly the plane. $\endgroup$ – Bianfable Oct 31 '18 at 13:31
  • 2
    $\begingroup$ "In fact, the pressure at the static ports will drop as the aircraft's speed increases" - I'm not so sure about this, so I posted a question asking about it: aviation.stackexchange.com/questions/56631/… $\endgroup$ – Terran Swett Oct 31 '18 at 14:19
  • 2
    $\begingroup$ You should probably also mention that the static ports are essential for the altimeters and variometers. $\endgroup$ – Martin Argerami Oct 31 '18 at 16:53
7
$\begingroup$

The airplane instruments that need barometric data, airspeed, altitude, vertical rate and all that, need to have a connection to the atmosphere that reads the true ambient air pressure unaffected by the dynamic factors going on in the air stream. You can't measure the air in the pressure hull for obvious reasons, and you can't just measure the pressure in an unpressurized part of the fuselage because there is usually some amount of ram or suction influence on the air within that space and it can't be relied upon as a true indication.

The only place where you can measure true ambient (or static atmospheric) pressure on a body moving through the air at high speed is with a hole that is flush to the surface and perpendicular to the airflow. That's what the static port is. It's always along the side where the surface is more or less perpendicular to the air stream, and is usually near the front where the equipment that needs to measure the ambient pressure resides. Hence the static ports just aft of the cockpit beyond the curve of the nose.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.