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11-08-2013, 01:53 PM
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Join Date: Jan 2009
Location: Beautiful downtown Winnemucca
Posts: 87
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Airspeed Indicator broken?
I have an airspeed indicator in my hand, not connected to anything. I can blow into the AI's pitot port and quickly bring the indicated airspeed up to any value I want. When I quit blowing into the AI, the needle very slowly goes back to 0. It takes 60 seconds for the needle to go from 120mph indicated to 0 with both pitot and static ports open. Is this normal or does the AI likely need repair?
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Flying Maule MXT-7-180
Building RV-9
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11-08-2013, 04:07 PM
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Join Date: Dec 2007
Location: Fredericksburg, TX
Posts: 662
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There is a small needle-type valve in the AS pitot input that can be adjusted to change the rate at which airspeed can change. Usually can be done with a small screwdriver. In too much and the airspeed changes too slowly (like yours); out too much and the airspeed will "bounce" around in unstable conditions.
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Jim Averett
RV-8
TS36 - Silver Wings
Fredericksburg, TX
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11-08-2013, 04:55 PM
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Join Date: Mar 2005
Location: Dallas area
Posts: 10,768
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And for anyone else reading this thread; NEVER blow into an ASI.
If you want to operate it by mouth, apply suction to the static port.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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11-08-2013, 05:54 PM
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been here awhile
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
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Quote:
Originally Posted by Paul B
I have an airspeed indicator in my hand, not connected to anything. I can blow into the AI's pitot port and quickly bring the indicated airspeed up to any value I want. When I quit blowing into the AI, the needle very slowly goes back to 0. It takes 60 seconds for the needle to go from 120mph indicated to 0 with both pitot and static ports open. Is this normal or does the AI likely need repair?
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Quote:
Originally Posted by Mel
And for anyone else reading this thread; NEVER blow into an ASI.
If you want to operate it by mouth, apply suction to the static port.
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It probably needs repair now......
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11-08-2013, 09:11 PM
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Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,958
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Quote:
Originally Posted by Mel
And for anyone else reading this thread; NEVER blow into an ASI.
If you want to operate it by mouth, apply suction to the static port.
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I haven't ever done this but can you tell us more about why blowing into the ASI is a bad thing? My first thoughts are this is exactly what the pitot tube does.
Is it the speed and force with which one could possibly peg the needle if they were not used to how much pressure it takes?
Thanks Mel, always learn something from you.
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Kurt W.
RV9A
FLYING!!!
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11-09-2013, 06:24 AM
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Join Date: Mar 2005
Location: Dallas area
Posts: 10,768
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The ASI is very sensitive to force and speed of the "blowing" and the moisture of breath.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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11-09-2013, 08:51 AM
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Join Date: Jan 2009
Location: Beautiful downtown Winnemucca
Posts: 87
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Thanks for responding!
I am always grateful for the collective wisdom at this site and the eagerness to share it. It sounds like I may have damaged the airspeed indicator by blowing into it (I only did this about 100 times), if it wasn't already broken. Can anyone recommend a place I could send this instrument to get checked out and possibly repaired?
__________________
Flying Maule MXT-7-180
Building RV-9
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11-10-2013, 05:21 AM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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A rubber squeeze bulb and a length of hose attached, can be used more gently while you're watching the needle move.
Best,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
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11-10-2013, 09:56 AM
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Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
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A large syringe works well and has good control when testing for leaks or to compare markings on gauge with a manometer.
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VAF #897 Warren Moretti
2019 =VAF= Dues PAID
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