Questions tagged [sensors]

Questions about various sensors used in aviation, both on aircraft and ground equipment.

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1 answer
176 views

What are this sensor especially those at tips?

This is an image of an RQ-7 B UAV what are those sensors marked in red circles.
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Can a modern commercial passenger flight recover from failed sensor(s)? [closed]

ABC News reports a failure in a pitot tube sensor may be the cause of an AirFrance Rio to Paris flight tragedy. Excerpts from the news include: An Associated Press investigation at the time found ...
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2 votes
1 answer
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Why is a pressure type sensor fire warning system not affected by bends or kinks in the line?

In a pressure based fire warning sensor, there is a line containing helium gas with a hydrogen core. Flight manuals say that a bend or kink in the gas line does not affect their operation. But if ...
8 votes
4 answers
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Are there wool threads for displaying angle of attack?

Like there is a wool thread on a glider's canopy for showing relative wind on yaw axis. Are there or have there been a wool thread as a long term mean of showing angle of attack? For instance placed ...
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10 votes
2 answers
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Why is this angle of attack sensor tab not symmetrical between the leading and trailing edges?

Here is an Angle of Attack (AoA) sensor I took from here. If you are interested to know the AoA detail, just click the link. You may see what is inside it. But not sure what airplane's AoA sensor it ...
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What does "half of the horizon circle" means?

The definition of Prevailing Visibility is: "Prevailing visibility is the horizontal distance over which objects or bright lights can be seen and identified over at least half of the horizon ...
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1 answer
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What kind of signal is outputted from engine fire sensors

Engine fire sensor informs the pilot engine fire and triggers fire extinguisher to release their payload. However, fire extinguisher valves are controlled through pressure operated switches or ...
6 votes
2 answers
2k views

How does a fuel density sensor work? (densitometer, cadensicon)

While some fuel volume sensors use ultrasonic measurements this answer to How is fuel mass measured in airliners? says: The FCOM lists the sensors involved in this measurement: The FQI system ...
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16 votes
2 answers
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How is fuel mass measured in airliners?

Large airliners display the amount of fuel in each tank as a mass (usually in kg or lbs) and not as a volume. This makes sense since mass is important for weight&balance considerations and the ...
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5 votes
5 answers
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How do aircraft instruments determine the aircraft's orientation relative to the ground?

Autopilots exist for airplanes and drones, how is orientation measured with respect to ground? In particular how is the direction of gravity detected and how is it differentiated from acceleration due ...
17 votes
2 answers
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What are these bars on an F-16's nose?

I've always wondered what the purpose of these "bars" on the nose of the F-16 (and some other military aircraft) are. Are they sensors (if so, what kind)? Are they lightning strips? I can't ...
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1 answer
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How to simulate magnetometer used on navigation system?

Magnetometer is used to measure yaw angle which will be used on AHRS system.When I simulate the magnetometer in matlab, I feel confused about what unit should be used for measurements magnetometer?...
7 votes
3 answers
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Could airliners fetch data like AoA and speed from an INS?

If I understood what an inertial navigation system (INS) is, it should be able to calculate speed and orientation of the aircraft. If this is possible, why do airliners solely rely on sensors to ...
3 votes
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How is airspeed measured on supersonic aircraft? [duplicate]

Behind the shock wave air is subsonic, would that not cause an issue with the pitot tubes or any other sensor?
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Why is the pitot tube located near the nose?

The pitot tube located near the nose could be affected by the boundary layer and could increase the error. Then why is the pitot tube located near the nose?
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Fighter Jets speed [duplicate]

How does an aircraft measures (or calculates) its speed while in air? Which equipment or sensors are used for measurement of speed? Does it takes Earth as a reference frame for its speed measurement ...
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2 answers
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What is the purpose of aircraft localization? [closed]

I want to understand what is the purpose of doing localization while an aircraft is flying? What sensors are used by the instruments that do this localization of an aircraft? Is there more than one ...
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1 answer
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What is this thing on a FDX MD11 (MD10?)?

I assume something forward looking; not sure why there and how they got this to play nicely with radar
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What is that sensor on the Airbus A220?

What is the that sensor in the picture?
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1 answer
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Why does an ADIRU 1 failure disable all functions of the A330/340’s GPWS - even those not requiring ADIRU data?

Among the many (many many) aircraft systems degraded or rendered unavailable to the flightcrew of QF72 as a result of a partial intermittent ADIRU 1 (Air Data / Inertial Reference Unit 1) failure, the ...
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Do aircraft have accelerometers?

Do modern aircraft employ accelerometers or other similar equipment to measure g-forces on the aircraft? I could imagine this being used as an inspection/service indicator, particularly after hard ...
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Why do most commercial solid-state Inertial Measurement Units (IMUs) measure angular rate and not angular acceleration?

The vast majority of MEMS-based IMUs are formed by an accelerometer and a gyroscope, providing linear acceleration and angular rate measurements respectively. However, having available the angular ...
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Why aren't angle-of-attack data sanity-checked before being fed to other aircraft systems?

For most fixed-wing aircraft, accurate angle-of-attack information is utterly essential for safe flight, due primarily to the risk of stalling the aircraft if the AoA of one or both of its wings ...
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1 answer
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What is GPS HIL in layman's terms?

GNSS Horizontal Integrity Limit/ Horizontal Protection Level is a measure of GNSS position error/integrity that's very important in RNP operations and RAIM, but it has an obtuse definition in aviation ...
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How many Angle of Attack sensor vanes should a commercial passenger airliner have? [closed]

The ill fated MAX of recent news had 2 angle of attack vanes, with the MCAS computer picking the worst one. It seems a "software patch" may not be the only improvement option available. Sensible ...
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Why are the angle-of-attack sensors on most airplanes mounted on the forward fuselage rather than at the wing roots?

A source of reliable angle-of-attack information is important for airplanes, as flight at an excessively-high angle of attack can cause the airplane to stall, which is generally considered to be an ...
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2 votes
1 answer
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How do rate gyros and other sensors send information to the flight control computer in an F-16?

How do rate gyros and other sensors send information to the flight control computer in an F-16? I mean is it a hardwired communication or it is done through a bus? If by bus, what is the bus called? ...
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Why would there be airflow from the back of a TAT probe?

During walk-around checks, I occasionally find airflow coming out from the back of the TAT probes on the Airbus A320. I wonder if it's air to cool down the TATs as they are heated during flight for ...
6 votes
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642 views

What sort of sensors are used for sensing the positions of the control surfaces for the ECAM F/CTL page on Airbus aircraft?

During the pre-flight flight-controls-check how does the ECAM F/CTL page report on the actual positions of the control surfaces? What sort of sensors are these? Is it a proximity sensor? This is ...
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4 votes
1 answer
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How are sensors in the wheels connected to power and data buses?

In this question the sensors to measure the tyre pressure are described. But how do such sensors receive the electrical power they need, and how are the signal values transmitted back to the relevant ...
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1 answer
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What material and shape should be used for angle of attack sensors?

Does the material and shape of the vane for an angle of attack sensor have to be identical to the material and shape of the wing? What properties should I consider?
1 vote
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Why are so many tail-strike incidents not verified until later inspection?

One often reads of a "suspected tail-strike" at take-off (for example suspected because a controller has seen something from the tower, or because a cabin crew member sitting at the back of the plane ...
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1 answer
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How much does an air data module cost?

Curious how much Air Data Module and Angle of attack sensor costs, such that is used on commercial airliners.
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How are AOA sensors tested after working on them?

If a maintenance or replacement has been done for an AOA sensor, would the mechanic be able to test if the sensor now works correctly? Can such a sensor be tested on the ground? If there is no ...
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1 vote
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Aircraft with load sensors in their undercarriage to calculate CG [duplicate]

In another question on SE aviation I read that certain aircraft have load sensors in their undercarriage to calculate CG. Which are these types? The technology to build load sensors into the ...
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7 votes
3 answers
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Why do aircraft stall warning systems use angle-of-attack vanes rather than detecting airflow separation directly?

Stall warning and protection systems on essentially all aircraft work by using several hinged vanes on the side of the fuselage (usually at least three, and preferably more), which align themselves ...
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5 votes
4 answers
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Why are the AOA sensors placed outside the aircraft?

Why should the AOA sensors be placed outside the aircraft? Is it not the angle between the chord line of a wing and a vector representing the relative motion between the aircraft and the surrounding ...
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2 answers
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what type of sensors does the Boeing 737 MAX use for MCAS?

I can imagine there are several different ways to measure angle of attack (accelerometers, relative pressure measurements between pitot tubes, etc), but I'm curious which sensors the 737 MAX uses for ...
15 votes
1 answer
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What were the advantages of the L-1011 AoA sensor design?

The Lockheed L-1011 had an unusual type of AoA sensor. Instead of the usual vanes it used a tube with two rows of holes in it about 90° apart. A diaphragm sensed the pressure differential between the ...
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Has the number of angle of attack sensors been reduced in Boeing 737 Max, in comparison to the older models?

Boeing 737 is flying since 1967. I would like to know first how many ' angle of attack sensors' does it have, and has they number been reduced for Boeing 737 Max, in comparison to the older models ...
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18 votes
4 answers
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Why is not every airplane equipped with 3 angle-of-attack sensors?

For critical systems, redundancy is built into the system. It is common knowledge among designers/architects to have three different inputs so in case one is faulty, input from the remaining two can ...
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How many AOA sensors does the 737 MAX have?

How many AOA sensors does the 737 MAX have? Given that it's reported in the media, that one faulty AOA probe activated the MCAS on the Lion Air flight, I was wondering if anybody also knows how an ...
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10 votes
3 answers
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Is it common for automated control systems to use non-redundant sensors?

While reading an article about the Lion Air Crash with a Boing 737 Max 8, I was very surprised by the following paragraph: In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from ...
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14 votes
2 answers
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What is this tube in a jet engine's air intake?

I have long been wondering what is the official name of this little air intake tube located in front of the fan blades and its intended functions. I did search it on google but it was in vain. I guess ...
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Why are the positions of an aircraft's angle-of-attack vanes dependent on airspeed?

According to this answer to an earlier question of mine, the positions of the angle-of-attack sensor vanes on the A330/A340 are dependent not only on AoA, but also on airspeed (and, according to @ymb1'...
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1 answer
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Will an Airbus A320 plane go into an unrecoverable nosedive and crash if a single angle of attack sensor fails, like on Lion Air JT610?

For example, has an Airbus gone from cruise flight into an automated unrecoverable nose dive until it hit the ground because an AOA sensor failed in flight? Moreso, are there any cases of an AOA ...
3 votes
1 answer
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Do airplanes have sensors to detect landing gear fires?

Given that retracting a landing gear that happens to be on fire is a suicidally bad idea, for reasons that should be immediately obvious, do airplanes have temperature sensors on their landing gear in ...
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1 vote
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How is an out-of-trim condition (in relation to weight distribution) detected on the ground?

My question relates to Captain reports Out of trim and this answer. How is an "out-of-trim" condition like the one mentioned in the linked question detected on the ground? I.e "out-of-trim" in the ...
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Which company manufactures the air data system on the Boeing 787-9 'Dreamliner'

I'm asking specifically about the manufacturer and model of the Pitot probes/tubes that provide the pilots with current air speed readings. Pretty sure it's either UTC or Honeywell but can't find ...
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What are those sensors on the forward A321neo fuselage?

What are those sensors on the forward (Airbus) A321neo fuselage? If it helps, this is WOW air's TF-DTR.
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