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  #11  
Old 05-30-2013, 02:31 PM
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LAMPSguy LAMPSguy is offline
 
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All certainly valid points, I was certainly not advocating ripping out the systems now!

As for molecular counting, there are very similar systems on submarines. Not sure exactly how they work...probably know salinity, depth, temp, calculate density and can therefore make a pretty accurate guess as to the speed.

IAS vs TAS vs CAS...numbers that I think get used interchangeably by so many people in so many situations.

Just exercising the brain with this one.
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  #12  
Old 05-30-2013, 03:37 PM
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Engineering advancements occur when old engineers (like me...) retire. ("Why, in my day we had 6 pitot tubes and we LIKED it!")

Solid state sensors reliably detect the movement of wheels and other things in our cars - at a couple of dollars or less per sensor. You would think they could come up with a similar sensor that could measure the movement of the air itself some small distance off of the fuselage (then calibrate that). Something that would look like a little blade antenna or even a OAT probe.

The whole "static system" thing also seems silly nowadays. A flush-mount pressure sensor ought to have that value (ambient pressure) electrically as data, with no static system plumbing. Hmmmm - same thing in the pitot for that matter - the pitot tube becomes a dead end tube to a pressure sensor. Same for the AOA - after all, those three tubing lines are just running to a computer box (ADAHRS) with those exact sensors and conversions in it!

EDIT: SORRY LARRY - MISSED YOUR POST ABOVE! Maybe we have a business here...
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  #13  
Old 05-30-2013, 06:15 PM
flyvans.com flyvans.com is offline
 
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my prediction would be that we never move away from actual realtime air speed measurements. everything else remains an inferior backup.
however, the current way of doing it with long tubes being split into several parallel measurement units with possible leaks and hysteresis is quite outdated. also, the suceptibility to ice, bees (and forgotten pitot covers) will be further reduced.

as everything becomes more integrated, it is about time for someone to come up with electronic pitot respectively static units that digitize right on the spot and distribute the data electronically.

also, solid state measuring methods using laser doppler or ultrasound might one day replace the traditional pressure sensing.

as for altitude, pressure sensing will likely remain prime for a long time. both due to legacy compatibility issues as well as its connection to performance/aerodynamics. but who knows, maybe some day it will be easier and more accurate to volumetrically count molecules ;-)

regards,
bernie

edit: several posters having the same ideas while writing the post ;-)
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Last edited by flyvans.com : 05-30-2013 at 06:17 PM.
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  #14  
Old 05-30-2013, 06:16 PM
Direct C51 Direct C51 is offline
 
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Just to give you a data point from a fellow helicopter guy, our aircraft technical manual specifically states 'a failure of the air data computer does not constitute a grounding condition'. The pitot and static data are fed to the air data computer. That data is then combined with INS and GPS data to give us airspeed, velocity vectors, wind, etc. Essentially a loss of the pitot static system does not ground the aircraft. We are still required to have backup pitot static driven standby instruments that work, but these aren't used unless everything else is lost. I flew one the other day, high speed low level with a failed air data computer. There is no noticeable difference at all, except we do not have in cockpit wind information. I could easily do without a pitot static system. I think the problem is going to be when you lose all electrical equipment. Pitot static is all you will have left.
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  #15  
Old 05-30-2013, 06:51 PM
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rmartingt rmartingt is offline
 
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Quote:
Originally Posted by Bill_H View Post
The whole "static system" thing also seems silly nowadays. A flush-mount pressure sensor ought to have that value (ambient pressure) electrically as data, with no static system plumbing. Hmmmm - same thing in the pitot for that matter - the pitot tube becomes a dead end tube to a pressure sensor. Same for the AOA - after all, those three tubing lines are just running to a computer box (ADAHRS) with those exact sensors and conversions in it!
These are already in service... there's basically an air data computer built into the base of a pitot tube.

http://www.goodrich.com/Goodrich/Bus...r-Data-Systems
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  #16  
Old 05-30-2013, 07:53 PM
Norman CYYJ Norman CYYJ is offline
 
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We could be using a pressure sensor right in the pitot head or a solid state device to measure the temperature rise and then just run the data to our boxes.
It would save a bunch of plumbing.
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  #17  
Old 05-30-2013, 08:48 PM
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fl-mike fl-mike is offline
 
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There are many other ways of measuring air flow. Hotwire mass airflow sensors, ultrasonic Doppler shift, etc. All have trade offs.
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  #18  
Old 05-31-2013, 07:58 AM
Sig600 Sig600 is offline
 
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Quote:
Originally Posted by flyvans.com View Post
my prediction would be that we never move away from actual realtime air speed measurements. everything else remains an inferior backup.
This. The only number that matters when it comes to the safe operation of an airplane is local air speed over the wing, right now. The pitot tube is just too simple, too cheap, and too reliable to be replaced by some kind of GPS derived wizardry.

It would be akin to having some kind of off board system telling you what your rotor RPM is... how comfortable would you be with that?
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