37

Here's a better picture showing all probes, and labeled: Link to original, high-resolution, unnumbered picture They are: Ice detector Multi-function probe 1 Static port TAT probe Side-slip vane Pitot probe Angle-of-attack vane Airbus.com has a PDF (pdf page 125) about the various probes. 1 As the name suggests, the multi-function probes record different ...


24

Outside US, SI is generally used for everything except altitude, distance and speed. Altitude: 1000 ft happens to be reasonable vertical separation, which is somewhat easier to calculate with than the corresponding metric figure 300 m. Distance: There are two quantities that were never converted to decimal. Time and angle. Since we didn't switch to gradians,...


23

Non-SI is only used for altitude, distance and speed except in US and some other American countries. Altitude is in feet because 1000 ft happens to be reasonable vertical separation and 1000 ft is easier to calculate with than the corresponding SI figure 300 m. Also the procedures for instrument flying were first developed in the USA using feet. Distance is ...


20

Unfortunately, countries tend to want to decide themselves how stuff is supposed to work once you're within their borders. That's why we have different rules and laws, and when you go somewhere else in the world, you might need to know some of the differences. In England they drive on the wrong side of the road, imagine that! :) In order to have things run ...


18

In response to the pros/cons of feet vs. meters, the big advantage that feet have over meters, is that it allows you to use nice human-memorable numbers for cruising altitudes. In the US, we generally use 500ft for visual separation, and 1000ft for separating IFR traffic from other IFR. This translates to roughly 150m and 300m respectively. This means, we ...


18

European Civil Aviation Authorities use the imperial system to depict altitudes and airspace restrictions (feet), speeds (knots) and distances (nautical miles). Some VFR aircraft have speed indicators in km/h, gliders can have altitude and variometer in meters and meters/second and apart from a special ICAO VFR chart being available in metric in Germany, ...


16

Indirectly, as the difference between true air speed and ground speed. Since aircraft cannot measure true air speed, several steps are needed to arrive at the correct wind speed: The pitot tube (big aircraft have several of them) gives the stagnation pressure of the air, which is the sum of static and dynamic pressure. The static ports (again, big aircraft ...


14

Europe uses imperial for distance (nm), speed (knots) and altitude (feet). Russia and China are the only major countries that use meters for altitude - and it causes all sorts of confusion. Some aircraft (more in europe) use kilometers and statute miles/hour on the ASI - but the same is true in the US.


14

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 nonlinearities as well as external factors such as fluid type, ambient temperature, humidity, and angle between the flow and the sensor. Conditions in a wind tunnel or ...


13

Stations (STA), generally Fuselage Stations (FS), designate location along the length of the aircraft, increasing from nose to tail. Generally station 0 is somewhere in front of the airplane. One reason for this is that if the airplane grows longer, there still won't be any negative stations, and sections of the plane keep their station numbers. FS 100 can ...


10

I can tell you that all of the airplanes that I have flown (which are US registered, but some are French built) use the following: Feet for height Knots for airspeed (Nautical Miles/Hour) Some old airplanes still use Miles/Hour (MPH) Nautical Miles or feet for distance Statue Miles or feet for weather (visibility and RVR) Mach for high speed flight Inches ...


10

If you know GS and local wind speed, the TAS always the same, regardless of altitude. The true airspeed is called "true" because it is exactly how fast you are moving relative to the air. Picture it as a person in a weather balloon (which does not move relative to the surrounding air, i.e., TAS=0), pointing a radar gun at your aircraft to measure its speed. ...


8

What you need is enough lift to remain in the air. For that, the maximum lift of your hang glider needs to exceed the total weight. When you know the total weight of the glider (you included), you can derive the theoretical minimum airspeed from the lift formula: $$L_{max}=\frac12{\rho}V^2C_{max}S$$ $$V_{min}=\sqrt{\frac{2W}{{\rho}C_{max}S}}$$ Where: $L$...


8

Probably not. The 2012 paper Advances in Atomic Gyroscopes: A View from Inertial Navigation Applications* states in the abstract that "there are still lots of problems that need to be overcome to meet the requirements of inertial navigation systems." Even once atomic inferometer gyroscopes are able to meet the basic requirements of inertial navigation ...


8

In order to achieve the same flow conditions, you need to match several similarity numbers. The most important one expresses the ratio of inertial forces to viscous forces within a fluid and is called Reynolds number (Re): $$\text{Re} = \frac{v\cdot l\cdot\rho}{\mu}$$ Nomenclature: $\kern4mm v\kern6mm$flow speed $\kern4mm l\kern7mm$characteristic length ...


8

Where is the camera relative to these target aircraft, and what's behind them? Straight from NASA themselves: NASA flew a B-200, outfitted with an updated imaging system, at around 30,000 feet while the pair of T-38s were required to not only remain in formation, but to fly at supersonic speeds at the precise moment they were directly beneath the B-200 ...


7

Like anything else a Dynamometer is used except the engine is bolted directly to it (most likely on a test bench). In a car a rolling road is simply a way to couple the tires to the dyno without having to have any custom fittings. For what its worth cars lose a bit of horse power in the transmission/drive shaft/differential so shaft horse power and wheel ...


7

You state that "the transition should be much simpler in terms of human factors." Ideally, yes. In practice, no. When mistakes happen, they may well be lethal. The Gimli Glider incident was partly caused by a confusion between which system was used to measure fuel quantity. From Wikipedia: The subsequent investigation revealed a combination of ...


7

To expand a bit on the other explanations here, "flow cones" are one of the many methods used for flow visualization. When something is being tested in a wind tunnel or in flight, you usually can't see the air flow around the body. To be able to visualize the flow, something is added to the air, like smoke, or to the body, like flow cones or tufts. Tufts ...


6

Unless Boeing has recently changed to the metric system in their design work, the short answer to the question as to whether Boeing and Airbus use different systems insofar as aircraft manufacture is yes. I'm only familiar with Boeing up through the 747-400. Perhaps others can provide an answer for later models. The Boeing Weight and Balance Control and ...


6

As others have mentioned, the basic units to define the airspace are feet and nautical miles. However, some other values are also used when navigating the airspace, and a few are from the SI system. For instance: pressure settings: hPa (aka millibars, mbar) runway lengths: meters visibility: meters temperature: centigrades Regulations (VFR): minimum ...


5

To quote from the Wikipedia article on the subject: Although the unit knot does not fit within the SI system, its retention for nautical and aviation use is important because standard nautical charts are on the Mercator projection and the scale varies with latitude. On a chart of the North Atlantic, the scale varies by a factor of two from Florida ...


5

This is a historical development that dates back to that much of the early aviation equipment was sourced from the United States, and was consequently in imperial units. This in particular occurred after World War Two, and hence mixing them was a bad idea, and the imperial system stuck. Interestingly, the places where the US did not have a lot of influence- ...


5

There is a fair amount of variability between aircraft manufacturers as to how they reference physical locations on their airplanes, especially along the longitudinal axis. Even within a company, different schemes are sometimes used for different models. For example, on the Boeing 747-100, -200, -300, and -400 aircraft, the reference datum is 90 inches in ...


5

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 (laser Doppler anemometry) or PIV (particle image velocimetry) for detailed measurements themselves usually use Pitot tubes to measure the reference windspeed in ...


4

They are used to visualize the airflow over parts of the aircraft. See this document for more details about flow visualization techniques (flow cones are described at 2.2.1)


4

A Kalman filter is used on all kinds of IRU's and INS's, even with airspeed information as in an ADIRU. A Kalman filter is just a general method (and a very useful one) for state estimation and sensor fusion, which is exactly what's going on in an INS system. I wouldn't call this "compensation". Inertial naviagation requires us to read in sensor values ...


4

ADS-B* encodes the ground speed in NM/s (nautical miles per second) in $2^{15}$ increments of ≅ 0.22 knots each such that: 0 ≤ Ground Speed < 2 NM/s As of June 2015*, it is optional to report the ground speed (users can use two position reports to get the speed). Decoding to Knots (NM/h) is more common though for aviation for most of the world.** * ...


4

Supplementary answer: As the question mentions this NASA page shows a diagram of traditional Schlieren photography and it's the idea I had in my head. I assumed you'd need a carefully prepared light beam and couldn't figure out how this was done. Than's to @ymb1's comment, here are some slides from the NASA Armstrong Flight Research Center presentation ...


4

The true airspeed (TAS) can be calculated from the indicated airspeed (IAS), which is derived from the pitot tubes and static ports, as follows: $$ \mathrm{TAS} = \mathrm{IAS} \sqrt{\frac{\rho_0}{\rho(a)}} , $$ where $ \rho_0 $ is the air density at sea level and $ \rho(a) $ the air density at altitude $ a $, which depends on pressure $ P $ and temperature ...


Only top voted, non community-wiki answers of a minimum length are eligible