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Carb Temp Installation Problem http://thorp18.com/thorpforum/viewtopic.php?f=35&t=8245 |
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Author: | TonyNZ [ Tue Jul 03, 2018 11:39 pm ] |
Post subject: | Carb Temp Installation Problem |
At last 100/Ann inspection I decided to instal a carb temp guage I've had sitting around for some time. Installation went OK, blank out of carb and probe installed. Power on and all worked well until I went for a flight. Take off climb and cruise all good and I saw temps that I expected. The surprise came when I pulled power in the circuit and discovered the throttle would not fully close! It would come down to about 13-1500 rpm and thats it. I could put power back on ok but same problem when closing throttle. Well a wide circuit and approach and when over the numbers pulled the mixture to land. As we all know a Thorp wont land with that much power on. Start up and taxii in fortunately on grass so didn't have to ride the brakes much. I thought you dummy you have let the prob wiring get tangled with the throttle lever. Once pushed back in the hangar off with the cowl but there was no evidence if the wiring fowling AND the throttle would close as normal?! Any way tie wrapped the cable to several points and went for another flight, same thing! Dang!! Made up a stainless bracket to really ensure the wiring could not get near the throttle linkage, inspected the full length of the throttle system and there was nothing unusual. Another flight, the same problem!!!@#%. Running out of ideas, have another carb which I could check the location of the prob in the carb throat as I thought if it protrudes in too far it may fowl the butterfly but there is no way this could happen. Only thought left is that if ice forms on the prob and grows upwards (only needs about 3/8") that would stop butterfly fully closing and ofcourse once shut down for 10 mins or so the ice would melt and allow full movement. My next plan is to remove the probe and blank then see if problem still exists. Any bright ideas would be appreciated . Ah forgot to mention this is a O-320 A2A bog standard. Tony Schischka ZK-VMS T18C |
Author: | Ryan Allen [ Wed Jul 04, 2018 6:40 am ] |
Post subject: | Re: Carb Temp Installation Problem |
Any chance the probe itself is too long and getting in the way of the butterfly valve? |
Author: | James Grahn [ Wed Jul 04, 2018 9:29 am ] |
Post subject: | Re: Carb Temp Installation Problem |
Did you try carb heat while flying? Cubes |
Author: | Rich Brazell [ Wed Jul 04, 2018 10:23 am ] |
Post subject: | Re: Carb Temp Installation Problem |
If it were me and I am , I would remove the probe and try it in the other carb to see if the guilty bastard is hanging things up ! RB |
Author: | thorpdrvr [ Wed Jul 04, 2018 3:27 pm ] |
Post subject: | Re: Carb Temp Installation Problem |
Possible vacuum leak around temp probe that is letting air into carb throat even when butterfly is totally closed?? |
Author: | TonyNZ [ Wed Jul 04, 2018 3:53 pm ] |
Post subject: | Re: Carb Temp Installation Problem |
Thanks all. A bit of a brain scratcher. Yes tried carb heat. I think best to remove probe to prove if it is the cause then take it from there. Tony S ZK-VMS |
Author: | 1albee [ Wed Jul 04, 2018 9:24 pm ] |
Post subject: | Re: Carb Temp Installation Problem |
When you installed the probe, did you remove the carb. ? If so you may be getting a air leak when things get warm. You can spray something like WD - 40 around the carb. with the engine running and see if there is a change in RPM or running smooth. Be very carful when doing this ! Secure aircraft to known strong tie down, Think about hands or head into prop and if too much spray is used, smoke +++ can be a result. Phil 118BC |
Author: | Bill Williams [ Thu Jul 05, 2018 9:56 am ] |
Post subject: | Re: Carb Temp Installation Problem |
I'd rather be lucky than good! |
Author: | James Grahn [ Thu Jul 05, 2018 12:15 pm ] |
Post subject: | Re: Carb Temp Installation Problem |
I'm glad you found it. Also glad you remained calm and landed ok with a stuck throttle. Could have been worse. Cubes |
Author: | Rich Brazell [ Thu Jul 05, 2018 1:32 pm ] |
Post subject: | Re: Carb Temp Installation Problem |
Bet you won't do that again ! The airlines are just as guilty ! Personal knowledge involving a contract Spirit Airlines DC-9 leased to the Navy . A lot of FOD ( safety wire , etc. ) found in the belly of the AC . Like Cubes said , you kept a cool head with a jammed throttle !! RB |
Author: | TonyNZ [ Fri Jul 06, 2018 3:42 am ] |
Post subject: | Re: Carb Temp Installation Problem |
All back together and went for a quick flight, glad to report "ops normal". I love flying my T18! Tony S ZK-VMS |
Author: | flyingfool [ Fri Jul 06, 2018 9:25 am ] |
Post subject: | Re: Carb Temp Installation Problem |
So the lesson here (for me) is to not leave anything directly below the Aircraft that needs to be reinstalled. As something may drop into that other part when working above it. |
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