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Hot answers tagged

28

Your daughter is right as explained here: The 'bug-eyed' face of the parabrake door mounting the two rear-hemisphere radar warning antennas. So they do detect other airplanes and probably the smiles of their pilots too as they are getting close to the phantom.


27

You're right. It's the ECM/EW antenna/equipment (fairing) in all the aircrafts except Typhoon. This photo shows the details of EW/ECM suite in Gripen. Source: www.w54.biz In Typhoon, it is the engine bleed air heat exchanger. The part is in detail here. Source: b-domke.de


26

The short answer is that we want to warn the pilots about an impending stall well prior to an actual stall condition. From a safety perspective, waiting until the airflow starts to separate, or at the onset of buffeting, it's already too late. By using AOA we can set a very conservative threshold. This AOA threshold can be adjusted by taking into account ...


23

From what I have studied at my instrumentation course, it rotates and reads the angle between the current position and the reference position. You then have several (3-4) of them around the fuselage because a roll maneuver (for example) will alter the measurements asymmetrically and in this way you can compensate for this effect.


20

An AOA vane (like what you have shown) works by aligning itself with the local airflow, like an arrow. The angle to some reference line (normally aircraft fuselage horizontal) is then measured with a potentiometer/RVDT/etc. This is the local angle of attack. Often the local angle of attack is converted to aircraft angle of attack through a calibration ...


20

Would installing the AOA vane (or, in general, sensor) at the wing root be more accurate than installing it near the nose? No, it wouldn't. In fact, it may be slightly worse due to the larger upwash at the wing leading edge and the vane protrusion may even negatively interfere with the wing aerodynamics. Traditionally, AOA measurements are used for stall ...


17

I have worked on and designed DIRCM systems. Most of the technical specifications on these systems is classified. Also, the U.S. is not the only country with DIRCM systems. In particular, Israel is equipping their airliners with the C-MUSIC system. How does this system work? Basically, a laser at the wavelengths of the Infrared Missile seeker is directed ...


17

Those sensors are part of the AN/AVR-2A Laser Warning System. Here is a closeup of the system components. The AN/AVR-2A is a passive laser warning system which receives, processes and displays threat information resulting from aircraft illumination by laser designators, range finders and beam riding missiles. ... The AN/AVR-2A LDS consists of one interface ...


15

The probe on the left is a TAT (Total Air Temperature) probe and the device on the right is an Ice Detector. From this website: UTC Aerospace Systems (Total Air Temp) From this website:UTC Aerospace Systems (Ice Detector)


15

That's the EPR inlet pressure sensor (there's another one located aft of the engine in the exhaust). EPR = Engine Pressure Ratio, one way to measure thrust. (source) See also: What is the difference between EPR and rotor speed as thrust setting parameter? How does the EPR reading behave in reverse, and in reheat modes?


14

No, it is not possible to place the sensors inside the aircraft, because the angle-of attack sensors need exposure to the surrounding air, in order to measure, as you mention yourself, "relative motion between the aircraft and the surrounding air".


13

Your assumption is correct - it is indeed about infrared (wavelength between 750 nm and 10,000 nm) and ultraviolet (wavelength between 100 nm and 400 nm) radiation. The sensor detected two specific wavelengths, one from each range. Every body has an electromagnetic radiation which is consistent with its temperature. This radiation has an intensity ...


13

While it would not significantly affect the O₂ percentage one thing that must be tabulated on a cargo aircraft is the amount of dry ice loaded. Dry ice is very common in packaging to keep perishable shipments cool during transport. Since dry ice sublimates into gaseous CO₂ as it warms there is a limit to how much can be loaded into an aircraft. If there is ...


13

The Boeing 737 MAX has 2 AoA sensors. However, MCAS only takes input from 1 AoA sensor at a time. Sources: The black box flight recorder data for Lion Air JT610 shows the data from 2 AoA sensors, labeled "Left" and "Right". Also, if you look at the nose of the 737 MAX, you will see a left and right AoA vane. (The sensors with the red tags are pitot tubes)...


11

How does this system work? Guardian is basically a Directional Infrared Counter Measures (DIRCM). By using an infrared laser (and an optical parametric oscillator to generate a second IR Band wavelength) the Guardian jams the IR seekers of incoming Infrared missiles through their sensor apertures. Does this successfully work in countering all types of ...


11

if a single angle of attack sensor fails No. An A320 has three AoA sensors. If one reports a different value to the other two, the avionics will ignore values from that AoA sensor and use the values from the other two. If two of the three fail and report consistent values - the avionics will believe the third is the odd-one out and unreliable. If those ...


11

Triple redundancy is necessary to detect a fault and exclude it. The system then continues to operate through the fault. Double redundancy is used to detect a fault but cannot exclude it, so the system stops operating. The important fact is that the faults they actually detect are identical. Stall events are rare and are normally not expected in flight. ...


10

In general, yes. Except in certain configurations, namely autoland, autoflight functions are usually fed with one set of sensors. This matches the fact that pilots flight instruments are fed from a single source as well. Therefore, the autopilot behavior and instruments should have a coherent and predictable response. The main reason is fault isolation. If ...


9

As you have already imagined, it's the APU fuel line shroud drain, as visible here: (Source) Detail: The fin gives an aerodynamic profile to the drain. The reason this drain exists seems to be: Natural fuel leaks from the auxiliary power unit (APU) fueling line were supposed to drain harmlessly out the bottom of the structure as designed, ...


9

The primary flight display¹: is a single display, but it shows five separate instruments: On the left, the speed tape. This shows the value from the pitot probe. In the middle the attitude indicator. This shows attitude from gyroscopes. All gyroscopes are grouped in the “inertial reference unit”. On the right the big tape is altitude. This shows the value ...


9

The air conditioning system on board airliners is an open system: it scoops up air from the atmosphere, compresses it, expels it through the cabin vents, and then outflows it through discharge valves. In modern airliners there is a certain amount of re-circulation: the expelled air was of such good quality that it seemed a waste to just dump it in the ...


9

I found several patents that resemble the L-1011's, dating back to at least the 50s. One such patent remarks that there are two main types, the vane, and the rotating pneumatic tube (also comes in conical shape). The advantages of the latter when compared to the vane-type are: [B]etter balancing characteristics, lower air friction, greater sensitivity, ...


8

The pitot tube has nothing to do with the angle of attack. It is used for measuring pressure which in turn gives you the airspeed. Accelerometers are used for the Inertial Navigation System. The angle of attack is another sensor (shown below): the principle is that it rotates and reads the angle between the current position and the reference position. ...


8

This is a so called aspirated TAT sensor, optional on the Airbus. Air is being drawn through aspirated TAT sensors to ensure that they correctly indicate the temperature even when the aircraft is not moving. Normal TAT sensors develop a bias when the aircraft is static. This video gives a nice explanation.


7

In place of pitot-static system No, because it measures different physical quantity. Laser Doppler anemometer measures velocity of the stream¹. But pitot-static system does not. Pitot-static system measures dynamic pressure and expresses it as airspeed at which that dynamic pressure would occur at sea level on an ISO standard day². Since lift and control ...


7

Two AoA sensors are more reliable than three! Let's have a look at probability calculation, and assume the fault probability of one sensor to be p = 0.1 % (per flight, or whatever you like to choose). The probability of the same sensor to work as expected is q = 1 − p = 99.9 %. Two Sensors The probability for no fault: q2 ≈ 99.8 % a discrepancy (1 fault)...


6

Farhan is correct that these "bug eyes" are part of the radar warning system, but unfortunately is incorrect as to what that system actually does. Radar warning systems are commonly installed on military aircraft. Their primary purpose is to detect the upper-level radio frequencies employed by ground- and airborne-based active (i.e. radiation-emitting) ...


6

The pod contains the Radar Warning Reciever (RWR). The variant in the picture is the TR-1B, which had wingtip mounted RWR units. According to globalsecurity.org: The Air Force has fielded new electronic countermeasures on the aircraft, giving it a jamming capability and upgraded radar warning equipment with wing-tip mounted digital receivers. As an ...


6

They both use a tire pressure monitoring system (TPMS) from Crane. Crane's marketing materials on the system are available on its site, and this newsletter from Boeing confirms it: The software group helped with testing on a new tire pressure and brake temperature monitoring system on the 777 for Boeing supplier Crane Aerospace & Electronics. (...


6

On a Boeing 777, a tire pressure sensor/fill valve is installed on each of the 12 main gear wheels and two nose gear wheels. There is an in-axle transformer in each of the axles. The tire pressure sensor/fill valve is made of an air fill valve and three independent pressure sensing channels which provide accurate tire pressure. The tire pressure sensor/...


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