Questions tagged [measurement]

Questions about various forms of measurement used in aviation

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10
votes
2answers
1k views

What is the effect of altitude on true airspeed?

I know that wind is taken into account when we compute the TAS(true airspeed) and GS(ground speed). However what is the relationship between the TAS and altitude? For example: What is the true ...
1
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1answer
210 views

What is the relation between altitude and vertical speed?

I recently saw 2 graphs on a flight path on BBC, shown below. For those interested, it's the path of the recently crashed Boeing 737 max flight ET302, but that's irrelevant to my question. My ...
2
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1answer
83 views

Pitot tube model

EDIT: Background on my application I am making a few measurement models for an extended Kalman filter (EKF). The EKF is meshing an INS and a GPS currently, but the GPS update rate does not update ...
11
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2answers
885 views

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

These two popular press articles discuss the use of schlieren photography to image shock waves of jets during flight using a special schlieren camera on a third plane. Gizmodo: NASA Captures First-...
2
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1answer
658 views

How to calculate DDM in a ILS dual frequency system?

I'm working in a project where I have to process ILS baseband signals. I have no problem obtaining DDM value from single frequency signals, nor the individual components of a dual frequency signal (...
1
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1answer
1k views

Where is the wing sweep angle measured from?

If you look at a 747 planform wing you see something like this: In several aerodynamics and aircraft design text books they use the wing sweep angle as an important parameter to measure the wing ...
3
votes
2answers
209 views

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

I want to compare some recent turbofan engines in terms of fuel efficiency, particularly the PW535A and FJ44-4. I found the SFC for the PW535A to be 0.44 lb/h/lbf. I couldn't find anything on the ...
11
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2answers
1k views

How is windspeed scaled in wind-tunnel tests?

Let's say you have a scale model that is 1:10th the size of the real thing. You want to test this in a wind-tunnel. Do you also scale down the windspeed 10x? Why or why not? I would think it has to ...
1
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1answer
401 views

What is the unit for ground speed reported by ADS-B?

Strangely enough, I'm having trouble finding the unit reported by ADS-B on the Internet. Many sites simply refer to it as "ground speed". Is it measured in KPH?
0
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1answer
90 views

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

How do you find the measurement of Piper Archer Tail Plane distance to the center of the gravity. Google really doesn't help me... maybe you guys know some website that has databases of small ...
4
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3answers
4k views

How does Kalman filtering work in inertial navigation systems?

As far as I understood it correctly most INS-systems use a Kalman filter to compensate measurement errors. I would like to know: Does the Kalman filter compensate the errors from all the onboard ...
7
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1answer
11k views

How is the wind direction and wind speed measured in flight?

Most large aircraft have a wind direction and wind speed indicator. How is this measured? The vector difference between TAS and ground speed? How accurate is this? In the below picture (taken from ...
6
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2answers
1k views

How is horsepower measured for aviation piston engines?

As far as I can tell, aviation piston engine power output is typically measured in HP (horsepower). Automotive engine power output is typically measured by running the host vehicle on a rolling road, ...
3
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2answers
464 views

Is there an explanation for the measurement system used in aviation? [duplicate]

Why is speed measured in knots (as opposed to kmp/h or mp/h), and distances in nautical miles? Is there a reason for following such a system?
3
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3answers
1k views

Is there a database of airport ceilometer raw data?

I am interested in obtaining raw ceilometer data, to test some cloud/aerosol layer identification algorithms. Is this type of data freely available or will I need to ask for it directly from the ...
1
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1answer
173 views

Are there any companies that use atom interferometers in aircraft?

Are there any companies that use atom interferometers in aircraft? If so, are they used for navigation? If not, is it possible to assemble it? Here is the link from wiki Atom interferometer and link ...
2
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1answer
681 views

Still using knots, nautical miles, inches of Hg. Is that impossible to switch to SI units? [duplicate]

Why doesn't the aviation industry use SI units?. I believe only a few countries use meters and other SI units in air transportation, including India and China (please correct if wrong). Using kts ...
13
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3answers
5k views

Does European airspace use the metric system?

I figured this was probably a no brainer, since Europe uses the metric system, I assume the airspace does... But then I remembered that aviation likes international standards, and I know the US uses ...
3
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2answers
663 views

What do aerodynamic flow cones measure?

This picture of an Airbus A350 test aircraft shows multiple instruments on the flap fairings, wing fairing and on the empennage: Source: A380_TLS_A350 AIB199GG (high-res version) They are being ...
31
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1answer
11k views

Which external instruments are visible on the A350's nose section?

Most pictures of airliner's nose sections show small dark tube- or fin-shaped instruments sticking out of the fuselage below the cockpit windows. For example this Airbus A350 shows them well: ...
11
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3answers
50k views

What is the coordinate system used in an Aircraft?

I know that from nose to tail the aircraft is divided by STA (station). At least for Boeing and Airbus this is the case but I am not familiar with other manufacturers. However, there is also two ...
24
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4answers
9k views

Why doesn't the aviation industry use SI units?

This is a followup to What is the measurement system used in the aviation industry? and related to this question from History. I can understand the arguments as to why adoption of SI units would not ...
23
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4answers
34k views

What is the measurement system used in the aviation industry?

I saw this question from History Stack Exchange and noted that the US is still using the imperial measurement system such as feet, miles and pounds. Given that a plane may need to fly from one ...
6
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1answer
2k views

What are these acceleration parameters produced by the Inertial Reference System?

Following acceleration parameters are transmitted from Inertial Reference System (IRS) to Flight Control System (FCS): Flight Path Acceleration Along Track Acceleration Cross Track Acceleration ...
21
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3answers
10k views

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

I know that some countries (Russia and China for instance) use meters to measure altitude while the rest of the world uses feet. Why isn't this standardized around the world? I guess all modern ...
16
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2answers
629 views

How can I estimate the minimum runway needed to take off with a hang glider?

I'm interested in short, or trick, take-offs - such as from platforms, tall trees, etc. I think that I should have a wind speed and direction measure an understanding of my wing surface area This ...