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Topic Title: What are the alternatives to measuring aircraft airspeed using Pitot Tubes?
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Created On: 23 October 2013 11:26 AM
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 23 October 2013 11:26 AM
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jarathoon

Posts: 1041
Joined: 05 September 2004

Air speed is the speed of an aircraft relative to the prevailing wind speed.

GPS devices measure speed over land not air speed, so may give a misleading figure for airspeed.

Using Pitot tube assemblies is the most common way of measuring air speed at the moment on aircraft.

http://en.wikipedia.org/wiki/Pitot_tube

Are there other ways of doing this?

Is it possible to use strain gauges attached to aircraft structures (for example, where the leading edge of the wing meets the fuselage) to infer auxiliary measurements of air speed from strain forces on the aircraft?

Small pressure plates or other devices on forward facing structures would be possible as well, but they might be subject to icing up in certain conditions just like pitot tubes are (ideally the auxiliary sensor should operate independently and not fail under the same environmental conditions as pitot tubes).

Any thoughts? Good for a student project perhaps?

James Arathoon




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James Arathoon
 30 November 2013 09:42 AM
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edwinjarvis

Posts: 11
Joined: 13 November 2013

Let me get into it deeply then answer you back...........
 30 November 2013 01:58 PM
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jarathoon

Posts: 1041
Joined: 05 September 2004

If you attempt to use wing to fuselage strain gauges, you will have to compensate the measurements for real-time changes in the thrust output of the jet engines (perhaps by using another set of strain gauges on the jet engine wing mount points).

Obviously there are an array of other complications, associated with changes in roll, pitch and yaw as well; Effects due to changes in air density and cloud etc can be determined on fully instrumented test fights, made by FAAM for example. http://www.faam.ac.uk/

I understand the BAe 146-301 they use is stripped down and rebuilt every so often, as part of its regular maintenance cycles. Once wind tunnel investigations on model aircraft are tried, Cranfield University might be a good place to contact to investigate this on a real instrumented jet aircraft.

Determining if the pitot tube assembly has failed with a reasonable degree of confidence would be a very worthwhile function even if accurate measurements of air speed in all conditions prove not to be possible.


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James Arathoon
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