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15 votes
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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 ...
Camille Goudeseune's user avatar
10 votes
Accepted

What is the effect of altitude on true airspeed?

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 ...
Sanchises's user avatar
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8 votes
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How is the camera positioned for these plane-to-plane Schlieren images of shock waves?

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 ...
Federico's user avatar
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8 votes

How is windspeed scaled in wind-tunnel tests?

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 ...
Peter Kämpf's user avatar
8 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 (...
Vladimir F Героям слава's user avatar
6 votes

Why are pitot-static measurements preferred over other velocimetry techniques?

There are quite a few reasons. First off, as everyone has already mentioned, HWAs are quite fragile and somewhat more complicated to decode (though the latter is a non-issue with modern electronics). ...
Kostadinov's user avatar
5 votes
Accepted

How long should a pitot tube extend from the wing?

That’s going to vary from airframe to airframe based on windtunnel data. Ideally you’re searching for a place where the tube orifice has good access to free stream air that is undisturbed by airflow ...
Romeo_4808N's user avatar
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5 votes

How does Kalman filtering work in inertial navigation systems?

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 ...
RealAnswersNotAI's user avatar
5 votes
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How does Kalman filtering work in inertial navigation systems?

First of all you should know that a Kalman filter is a state estimation technique. More than a filter, it is an estimator. Whilst it does filter sensor noise in the process, the most important use is ...
DeltaLima's user avatar
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4 votes

How is the camera positioned for these plane-to-plane Schlieren images of shock waves?

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 ...
uhoh's user avatar
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4 votes

What is the effect of altitude on true airspeed?

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}{\...
Bianfable's user avatar
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4 votes

What is the EGT probe output tolerance?

It is much more complex than you can imagine. I found a master thesis entitled Investigation of Sensor Faults in a Gas Turbine of Politecnico di Torino, studying the CFM56 turbofan. It states that ...
ocirocir's user avatar
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4 votes

Modern method to verify speed of a homebuilt aircraft

On the newest experimental development programs they use what are called "Smart Booms", or Smart Air Data Test Probes, for the test a/c, which is a flight data probe or boom that doesn't ...
John K's user avatar
  • 132k
4 votes

Modern method to verify speed of a homebuilt aircraft

The "Brauniger IQ Comp" variometer which is at least two or three decades old now is a rate-of-climb instrument for hang gliders. It is capable of producing a wind direction and wind speed ...
quiet flyer's user avatar
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3 votes

If the altitude of the aircraft is given by the pitot tube, in icing condition with heat on, how is real altitude /speed interpretation done?

The pitot tube measures pressure, not density. The pressure is not affected by the heating of the tube.
DeltaLima's user avatar
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3 votes

Who decides what measurement units are used for altitude, and why is there no standard?

As to feet being the best measurement for height, what utter nonsense! Prior to WW2, all metric countries flew in meters. That changed after WW2 with America dictating what happened on this planet. ...
Eric Burns's user avatar
3 votes

How is windspeed scaled in wind-tunnel tests?

It really depends on what data you need and the conditions you need it for. Let's say you want to test a scale aircraft model in a wind tunnel in order to predict the lift forces on the full-sized ...
cbrian's user avatar
  • 340
3 votes

How does Kalman filtering work in inertial navigation systems?

A Kalman filter reduces noise. If the sensor has a systematic error, a Kalman filter won't help you. Basically, the Kalman filter extrapolates an expected value and compares that to the next ...
Peter Kämpf's user avatar
2 votes

What is the coordinate system used in an Aircraft?

It is much different with depending on what you are doing. Engineering drawings reference a 3 point system for installations mainly Station (X or FS), Butt Line (Y or BL), and Water Line (Z or WL) ...
Thomas's user avatar
  • 21
1 vote
Accepted

Viewing and capturing real time values of Tachometer measuring instrument on television set and computer monitor in Aircraft and Automobiles

With modern automobiles (that is, after OBDII was introduced in the 1990s), it is trivially simple. You just need a Bluetooth OBDII reader (about $15 on Amazon, eBay, &c) and an application like ...
jamesqf's user avatar
  • 2,577
1 vote

How does a synchro resolver converter work?

The angle of attack sensor turns the shaft on a synchro (or a resolver: they're essentially the same thing) which is a transformer whose outputs are uniquely related to that shaft angle. That's where ...
stretch's user avatar
  • 289
1 vote

How to calculate DDM in a ILS dual frequency system?

I don't think you're supposed to just average the two together somehow by themselves. The two signals are designed to be used in different zones and in practice have very different signal strengths at ...
RealAnswersNotAI's user avatar
1 vote

How to compare two SFCs, one in thrust, the other in power (both turbofans)?

For comparing turboprops vs turbofans, you would normally divide the turboprop's SFC by the prop's thrust coefficient at comparison airspeed. For two turbofans, always compare TSFC. It's a function ...
Therac's user avatar
  • 27.6k
1 vote

How to find the measurement of how far Tail plane to Center of gravity of the aircraft?

First you calculate the position of the CG, then you do a simple arithmetic calculation based on the station of the tailplane.
Juan Jimenez's user avatar
1 vote

Why doesn't the aviation industry use SI units?

The first part of the answer is that it is too difficult to change. It would involve lots of rewriting rules and manuals and retraining. The second part is that it does not really matter. As a pilot ...
ghellquist's user avatar
  • 1,586
1 vote

What is the measurement system used in the aviation industry?

A common misconception is that pounds and kilograms, or nautical miles and kilometers are similar units. They are not actually measuring the same thing. The pound is a unit of force not mass, kilogram ...
Max Power's user avatar
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