Questions tagged [sensors]

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

Filter by
Sorted by
Tagged with
32
votes
2answers
5k views

What are these boxes built into the tails of some fighters?

In looking at European-designed fighters of the 4th and 4.5th generation, I keep seeing a common design feature; a box-like structure built into the tail, often in the top half or third. Some examples:...
31
votes
2answers
5k views

What is the smiley face sensor at the stern of the F-4 Phantom?

The F-4 Phantom has an interesting collection of sensors at the extreme rear of the empennage. What are these sensors for? My daughter calls them them smiley sensors but I suspect that is not the ...
30
votes
2answers
53k views

How does an alpha (AoA) vane work?

The alpha vane (also called AoA vane) is an external probe used to measure the angle of attack. I have been trying to understand how exactly it works, but I can't find any clear explanation or ...
17
votes
4answers
2k views

How does the Guardian counter-MANPADS system work?

I came across this picture of a FedEx McDonnell Douglas DC-10 equipped with an anti-missile defense system. (wikimedia.org) According to the picture description: FedEx became the first U.S. ...
16
votes
3answers
2k views

Do modern airliners have oxygen sensors in the cabin?

I know that airliners have pressure sensors to check the cabin pressure, and thus check if we can breathe (and get enough O2) inside it so we don't get hypoxia. But that got me thinking: Is there any ...
15
votes
2answers
3k views

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 ...
15
votes
1answer
771 views

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 ...
15
votes
1answer
3k views

What is this device protruding from the rear of this 787?

While looking at the photos from this question I noticed a small protrusion from the side of the plane. You can see it in the photo: and in the diagram from l@aeroalias answer: In the diagram it ...
14
votes
1answer
2k views

What are these sensors on the Night Stalkers' Chinook MH-47G?

What are these sensors (or lights) on this heavy assault Chinook MH-47G of the US 160th Special Operations Aviation Regiment, "Night Stalkers"? Source, picture by Russell Hill This regiment was the ...
13
votes
2answers
1k views

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 ...
12
votes
2answers
3k views

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 ...
10
votes
3answers
475 views

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 ...
9
votes
4answers
3k views

What is the ultraviolet signature, if any, of aircraft and jet engines?

The Wikipedia article on the FIM-92 B variant of the Stinger Missile says: In this version, the infrared seeker head was replaced by a combined IR/UV seeker that utilized rosette scanning. This ...
9
votes
1answer
9k views

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 ...
8
votes
2answers
488 views

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.
8
votes
2answers
1k views

How do tyre pressure sensors in aircraft work?

I am specifically interested in the sensors used on the B777 and B787.
8
votes
1answer
554 views

What additional functionality is provided by the F-14 nose pitot, absent in early models?

Early model F-14A had no nose pitot: ... but they seem to have quickly acquired them sometime in the late 1970s. The Iranian F-14s have them, and it's quite hard to find a picture of an F-14 without ...
7
votes
4answers
658 views

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 ...
7
votes
1answer
205 views

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 ...
7
votes
1answer
1k views

What is the purpose of proximity sensors on hydraulic systems?

One of the planes I worked on had ground spoiler response checked with proximity sensors. The reason mentioned for that was - "The ground spoiler is hydraulic only - hence its response will be checked ...
6
votes
4answers
392 views

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 ...
6
votes
1answer
354 views

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'...
6
votes
1answer
677 views

What sensors are required to fly RNAV 5 airways?

In the example shown above: Is an aircraft required to have all 3 sensors listed or just one of them to fly the L512 airway? What ICAO reference confirms the answer? Does 'critical DME' (bottom row) ...
5
votes
4answers
653 views

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 ...
5
votes
4answers
4k views

How are pitch angle and pitch rate measured in an airplane?

What equipment or method is used to obtain measurements of the pitch angle (θ) and pitch rate (q) during flight? Edit: I am asking about how the aircraft systems sense these quantities
5
votes
1answer
1k views

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 ...
5
votes
2answers
3k views

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 ...
5
votes
2answers
164 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 ...
5
votes
2answers
3k views

What is the difference between IMU (Inertial Measurement Unit) and AHRS (Attitude and Heading Reference System)?

According to online sources like wikipedia the difference belies on the addition of an on-board processing system (I assume it means a microcontroller) which outputs already processed data and not ...
5
votes
1answer
145 views

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 ...
4
votes
3answers
2k views

What types of fuel quantity sensors are used in an aircraft? How do they work?

Can you explain the different types of fuel quantity sensors used in most recent aircraft? Are ultrasonic tank sensors used these days? How does an ultrasonic sensor work?
4
votes
2answers
5k views

How would the Airbus A320 PFD respond to failure of all pitot and AOA sensors?

In theory, if all 3 pitot tubes and all 3 AOA-sensors would fail simultaneously for a period of time, could the PFD still deliver correct roll angle and horizontal displays? How would the plane ...
4
votes
2answers
926 views

What is this pod at the wing-tip of a U2?

In this image of a U2S, what it the very unaerodynamic looking pod at the wing-tip? It looks like it holds some sort of sensor package. However, it doesn't seem to appear on all U2s (at least not ...
4
votes
2answers
4k views

How does a pilot know if he has headwind, tailwind or crosswind?

While in cruise, without GPS how does a pilot know the wind direction? The airspeed sensors only register forward speed. Is it a matter of reaching waypoints sooner or later? And if flying on a ...
4
votes
1answer
120 views

Is there a system of automated sharing of current (experienced) weather between aircraft in flight?

For example, if say - Aircraft 1 is flying a certain route, being followed by Aircraft 2 at an interval of say, 5 minutes (over the same position). Is there a system by which Aircraft 1 can transmit ...
4
votes
1answer
98 views

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 ...
3
votes
1answer
285 views

Can a laser Doppler anemometer be used to measure airspeed?

Could this be used in place of or in addition to a pitot-static system?
3
votes
1answer
402 views

Do fuselage rip/crack/damage sensors exist?

Are there sensors that can detect a rip, crack or damage in the fuselage skin by not using air pressure differential on aircraft?
3
votes
1answer
253 views

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 ...
3
votes
3answers
2k views

What is Engine Pressure Ratio?

I kind of know what it is but I don't fully understand it. Wikipedia says, the engine pressure ratio (EPR) is the total pressure ratio across a jet engine, measured as the ratio of the total ...
2
votes
1answer
193 views

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 ...
2
votes
1answer
397 views

How can avionics detect tailwind? [duplicate]

We can see the effect of the tailwind on the plane's flight direction on the modern military fighter jet huds. I wonder about how can the avionic systems detect tailwind and which sensors using in the ...
2
votes
1answer
95 views

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? ...
2
votes
1answer
241 views

Is there a practical use of streaming data received from meteorological sensors installed on aircraft?

I am not the practitioner in the field of aviation, and my knowledge is mainly theoretical. Therefore I would be happy to get a feedback from practitioners on the following topic: I was reading about ...
1
vote
1answer
127 views

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 ...
1
vote
1answer
90 views

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 ...
1
vote
1answer
137 views

What are heat detection sensors and how can they cause a speed error?

From this news article on Saratov Airlines Flight 703: A report handed down by Russian investigators has blamed human error for the crash of Saratov flight 703, saying the pilots didn’t switch on ...
1
vote
1answer
74 views

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
1answer
278 views

What devices measure EPR & RPM on a turbofan engine?

What devices measure EPR & RPM on a turbofan engine?
1
vote
2answers
338 views

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 ...