23
votes
Accepted
Why is the pitot tube located near the nose?
There are several reasons to have the pressure sensors in the front section of the fuselage.
The further aft the more turbulent the airflow is and the thicker the boundary layer caused by the ...
- 2,246
22
votes
How can a pitot tube freeze when it's heated?
Captain Bill Palmer, in his book "Understanding Air France 447" has a section dedicated to answering that very question as it pertains to AF447. Although there is no way to know for certain he puts ...
- 28.1k
21
votes
Why don't airliners have a navigation GPS as back up in case of a pitot tube malfunction?
Airliners do generally have GPS receivers, but GPS doesn't give you the information that's needed in this case.
In AF 447, the primary consequence of the blocked pitot tubes was that the flight ...
18
votes
What were the safety recommendations following the Aeroperú Flight 603 crash?
who was responsible for ATC relaying false altitude information to the pilots
Not an easy question mostly because it asks (even if not directly) to put the blame on someone. And although there is not ...
- 6,940
17
votes
Accepted
Is it possible to accurately measure airspeed without pitot tube?
Technically speaking, inertial measurements are not sufficient to derive airspeed. You need pressure measurement (or airspeed measurement, see LIDAR). Pitot-static probes are the most usual and ...
- 1,537
17
votes
Accepted
Does the pressure at the static ports drop as the aircraft's speed increases?
The comment:
In fact, the pressure at the static ports will drop as the aircraft's
speed increases (Bernoulli principle)
is not exactly accurate. The aircraft is a complex aerodynamic shape ...
- 18.5k
16
votes
Accepted
Why not have Pitot Heat always on?
I can generally only speak for commercial aviation. The reasoning is probably the same or similar for General Aviation, but seeing as that is such a wide and varied field, with a tremendous number of ...
- 2,373
15
votes
Accepted
Why are pitot-static measurements preferred over other velocimetry techniques?
The linked article says that an HWA (hot-wire anenometer) is
fragile and requires complex equations to relate the sensed value to the fluid speed as well as correct for inherent, unavoidable ...
- 9,909
14
votes
What is the difference between a pitot tube and a pitot-static tube?
A pitot probe strictly measure ram air pressure, commonly called "pitot pressure" or Pt pressure. A pitot tube measures pitot pressure and pitot pressure only. A separate static port is required to ...
- 2,373
14
votes
Accepted
Why does the Boeing 737 have a pitot tube on the tail?
There are five sets of pitot tubes on the 737, organized into two groups, the pitot tubes on the nose are used for airspeed measurements, independent for the pilot and copilot and one as a backup. ...
- 35.8k
11
votes
Is it possible to accurately measure airspeed without pitot tube?
Airspeed - not reliably under all circumstances. You need to feel that wind somewhere in order to get a direct and accurate measure of the speed of it, and the pitot tube is an accurate and proven ...
- 60.7k
11
votes
Accepted
Why might flight schools prohibit you from testing pitot heat during pre-flight?
I was taught to check it (on a C152/172) before every flight but I've also heard people say that you don't need to. Some reasons I've heard people give for not checking it are:
Risk of draining the ...
- 71k
10
votes
Why can the aircraft not turn on pitot heaters itself?
There's much simpler and safer logic. Most modern Western transport aircraft automatically switch the pitot heaters on when in flight mode or at least one engine is running. Pilots can manually force ...
- 5,805
10
votes
Do pitot tubes account for reduced pressure at altitude?
A pitot tube measures the ram airflow entering the pitot tube which is aligned with the direction of flight. The difference between static air pressure (from a hole usually located at a perpendicular ...
- 26.3k
9
votes
What were the safety recommendations following the Aeroperú Flight 603 crash?
What caused the ATC to pass incorrect information to the flight crew was that they had no reason to mistrust their own instruments. The altitude information displayed to the controller was transmitted ...
- 27.6k
8
votes
Accepted
How does Pitot Heat influence airspeed indication (assuming no ice or moisture)?
No, there is no decrease or change with the use of pitot heat.
The pitot system measures pressure. There is no airflow through the system in normal operation. Any airflow through the system would be ...
- 16.5k
8
votes
Accepted
Which air stream pressure / speed is measured by the pitot?
You're correct that there are a number of parameters that influence the measurement of air data in general. For example, the total pressure measurement (as done using the Pitot tube) is influenced by,
...
- 99.4k
8
votes
Which air stream pressure / speed is measured by the pitot?
The first thing to have in mind is that a pitot tube is NOT measuring speed: the pitot tube measures pressure and later on the airplane (flight management system in a modern airplane) calculates the ...
- 3,873
8
votes
How does an air-data computer convert ram air pressure from the pitot tube into airspeed?
Usually there is an intermediate module ADM (air data module) that makes the conversion from analog pressure into digital numerical value. One ADM will do this for the ram air pressure, another ADM ...
- 1,732
8
votes
Accepted
Why are some A350s missing SSA probes on their nose?
You are right: the three side slip angle probes are redundant because side slip can be calculated by the ADIRS without these probes. Airbus included them in earlier A350 models to crosscheck this ...
- 51.6k
8
votes
Accepted
Are pitot systems protected from ice?
You can see an example sketch of a heated pitot tube in the FAA Handbook of Aeronautical Knowledge:
As you can see, there are two heaters that heat the entire tube and (ideally) stop ice from forming ...
- 51.6k
8
votes
Please describe ram pressure in simple terms
Airspeed is basically measured by measuring the kinetic energy of the air molecules impacting dynamic pressure port (for example on a pitot tube).
The higher the velocity, the more energy, hence more ...
- 25.8k
7
votes
Accepted
How does a pitot plate work?
The B-2's pitot plate has actually been the cause of an accident in conditions that may or may not have had the same effect on aircraft with pitot tubes.
Pitot plates work much like pitot tubes; they ...
- 642
7
votes
Is it possible to detect a pitot static failure (blockage) of air data probe during flight and alert the pilot?
The crew checks the pitots and static ports before the flight to ensure they are in good condition and not blocked by objects or insects. Pitot tube (pitot-static) can be obstructed in-flight. Static ...
- 68.6k
7
votes
What alternatives to pitot static systems are available or in development?
A number of systems are under development- most are optical systems- determining airspeed using LiDAR. NLR, for example has developed an Optical Air Data System for this purpose:
The developed ...
- 99.4k
7
votes
Accepted
What does the Airspeed indicator show when your pitot tube is blocked?
Depends on how much blockage. If fully blocked, as in air tight, the pitot side becomes like the sealed aneroid side of an altimeter and it only reacts to changes in static pressure, indicating the ...
- 118k
7
votes
What does the Airspeed indicator show when your pitot tube is blocked?
If the pitot tube gets blocked in flight, such as by icing, the airspeed indication is maintained at first.
Note that the indication is still subject to changes in static pressure as long as the ...
- 2,815
7
votes
Why are pitot-static measurements preferred over other velocimetry techniques?
Hot wire anemometers are great for measuring turbulent fluctuations on a very fine timescale (say kHz). This is really not needed for aircraft speed. The very same wind tunnels that use HWA or LDA (...
- 1,010
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