moy71 Posted January 21, 2009 Share Posted January 21, 2009 I am still learning to fly and on my pre-take off checklist is the need to switch off carb-heating after the run-up. Well shock/horror, as I was levelling off to circuit height i realised that the carb-heat was left on. I did not notice any change in the way the engine behaved during take off....it was like any other take offs i have done in the past. My question is: how serious is leaving the carb-heat on on take off? Thank you. ps...now i physically don't let go of the carb-heat. i leave my hand glued to it until i release it back. Link to comment Share on other sites More sharing options...
motzartmerv Posted January 21, 2009 Share Posted January 21, 2009 Don't beat yaself up mate, you wouldn't be the first to takeoff with carb heat on, and won't be the last. You got to circuit height didn't you.. so it couldn't have been all bad. Climb performance is reduced by having it on, so obviously we want all the climb we can get. A warm day or extra weight would have a larger effect then the 100 or so rpm drop on your climb out. I guess the worst case scenario is you don't quite have the pony's to get over an obstacle and after you get out and dust yaself off you realise you had carb heat on.... But, i think an object lesson has been learned so take from it what you can. Holding the carb heat out until its ready to go in will only work on the pre takeoff check, its much more common to leave it on doing touch n goes. Have a finals check at 200 ft, carby heat off, flaps set and windsock checked. It helps.. cheers Link to comment Share on other sites More sharing options...
Guest basscheffers Posted January 21, 2009 Share Posted January 21, 2009 There is the maintenance issue: the hot air does not go through the air filter, so you could suck in dust that causes engine wear. Also a reason to do the check and close it again immediately; the check should not take more than a few seconds anyway. I did almost the same thing the other week. I was practicing forced landings, solo. After the last one I headed back and it wasn't until I started the landing checks I realised it was still on... Link to comment Share on other sites More sharing options...
Student Pilot Posted January 21, 2009 Share Posted January 21, 2009 There is the maintenance issue: the hot air does not go through the air filter, so you could suck in dust that causes engine wear. Also a reason to do the check and close it again immediately; the check should not take more than a few seconds anyway. It's no good just pulling it on and off, you have to leave it there long enough so if there is ice it clears. If the revs pick up after a couple of seconds of carb heat on that indicates there is ice. I'd guess at around five second depending on Aircraft, and leave your hand on it till you push it off. Link to comment Share on other sites More sharing options...
markendee Posted January 21, 2009 Share Posted January 21, 2009 My Rotax airbox filters both hot and cold air. Don't know why all systems are not like this. I do realise there is not a large dust issue at altitude when heat is required but I think we have all been guilty of leaving it on while landing/taking off at times. As a maintenance issue I would rather all intake air be filtered. Mark Link to comment Share on other sites More sharing options...
Guest brentc Posted January 21, 2009 Share Posted January 21, 2009 There's a couple of issues that may asire by leaving on the carby heat: - You will be a few rpm down and thus have less power as stated (minimal impact) - Depending on aircraft type as stated, you may suck dust into the carby (not good and could cause damage, but depends on a/c type and setup - Jabs don't do this;)) - The mixture will be richer as the air is hotter coming in (I hope I've got that the right way around) - You could cause detonation and engine damage Mostly unlikely that you have done damage, so don't beat yourself up over it! Link to comment Share on other sites More sharing options...
Guest basscheffers Posted January 21, 2009 Share Posted January 21, 2009 I'd guess at around five second depending on Aircraft Five does not longer count as "few"? :confused: Mark: is that a property of all Rotax engines? Or just specific installations? Link to comment Share on other sites More sharing options...
markendee Posted January 21, 2009 Share Posted January 21, 2009 Bass, Only specific setups. The airbox supplied by ICP with the Savannah kit swaps cold air taken from the front of the engine bay just behind the prop and when heat is on takes air from the muffler. (That's clean air heated by passing around the exhaust.) Simple as can be. No airbox no heat at all. Mark Link to comment Share on other sites More sharing options...
motzartmerv Posted January 21, 2009 Share Posted January 21, 2009 You DO need to leave it on for a while to check for ice, not just operation. In winter we have had a rev increase after 15 seconds or more on many occasions. In fact it became part of the check. Remove ice from wings and controls, plug in battery charger for startup, and blow out carb ice just prior to takeoff.. Leaving the heat on until the revs raced, and quickly lining up and blasting off.. Link to comment Share on other sites More sharing options...
mAgNeToDrOp Posted January 21, 2009 Share Posted January 21, 2009 No Carby heat in a foxbat? How does it deal with icing in the carby then? Having only flown Jabs so far am just curious... Link to comment Share on other sites More sharing options...
Guest pelorus32 Posted January 21, 2009 Share Posted January 21, 2009 No Carby heat in a foxbat? How does it deal with icing in the carby then? Having only flown Jabs so far am just curious... The Rotax does not by default have a carby heat. You can install an airbox which provides carby heat. However there is not a lot of discussion of carby icing with Rotax engines leading one to speculate that they are not terribly prone to it. Talking about the 912 series here. Regards Mike Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted January 21, 2009 Share Posted January 21, 2009 The Lightwings and Storch SS4 have a carb heat set-up similiar by the sound of it, to the Savannah. I will use it occasionally prior to take off, but always pull it on a bit after a descent, prior to landing. On the subject of carb ice in 912s. Yes it is possibly, and I have experienced it on a couple of occasions. There were those in the past who swore that a two-stroke couldn't get carb ice either...wrong. Problem with carb iceing, is it is very incipient, probabily dosen't occur often enough for us to recognize it as such, and by the time you land and say 'what the..." all evidence is gone. If there was ever a Gremlin in the works ...this is it. Additionally, some people believe you have to have visible cloud, to get carb iceing...wrong...quite possible to get it in a cloudless sky. Often it can be kicked off by just loading some fuel, with a bit of suspended moisture in it. If the previous evening has been particulary dewey, can also be a good indicator of possible carb iceing conditions, that day. Also the standard met indicators which are dew point and humidity, the closer they are together IE; 65DP/62 Hum.........watch out. Far apart IE: 20 DP 50 Hum...less chance. Having experienced carb ice a few times with different engine types, it is something I have always got in the back of my mind when flying. One cough or a bit of rough running, bang ,on comes the carb heat !............. Link to comment Share on other sites More sharing options...
facthunter Posted January 22, 2009 Share Posted January 22, 2009 Power for Go round in a Jab. I witnessed an aborted touch and go in a Jab. the aircraft was just trundling along the ground and not accelerating at all. ( the runway is quite long) and eventually the pilot pulled the throttle and applied the brakes with only just enough runway left. The aircraft was not overloaded either. I spoke to the pilot later and he said that he had forgotten to take off the carb heat. So much for the performance. It has more effect on some engines than others, and I believe it could cause damage to some engines, as well as a significant power loss. Leaving the carb heat on is very common. I would suggest that EVERY throttle application to high power. that the carb control is checked cold as a follow -up. I have done it this way with students , and I think its important enough to do it.. Nev.. Link to comment Share on other sites More sharing options...
Guest brentc Posted January 22, 2009 Share Posted January 22, 2009 My carby heat was stuck on for probably a couple of months and I had no idea. There was a fault on the engine end. It could go a long way to explaining my higher than normal fuel consumption at the time (which coincidentally was just after the rebuild). Even when it is working there is little if any effect on engine rpm so I assumed it was working perfectly. Link to comment Share on other sites More sharing options...
Yenn Posted January 22, 2009 Share Posted January 22, 2009 It didn't stop your take off, so no problem. When the mixture is rich, due to the lighter air charge i doubt that you would get detonation problems, so all is dependent upon you realising that power is down and aborting the take off if necessary. I had an engine failure due to carby ice in a C150. I used carby heat right up to the time of applying full power, about 150m into the take off ground run power was so far down that I shut the throttle and the engine immediately stopped. It was a bleak, cloudy damp day at Grovedale in mud winter. Link to comment Share on other sites More sharing options...
poteroo Posted January 22, 2009 Share Posted January 22, 2009 Have changed pre-takeoff checks around to locate the power checks and carby heat test just prior to take-off. If we need to taxi a long distance, as in backtracking, then we ensure 30 secs of hot air before applying t/o power. If you can see condensation vapour off the propellor tips when doing your run-up.....you'll certainly need to prevent icing. Found that both PULP, and the old 'Super' mogas, seem to create more carby icing than avgas 100/130. happy days, Link to comment Share on other sites More sharing options...
Skykid Posted January 26, 2009 Share Posted January 26, 2009 Now the Foxbat doesn't have carb heat, and when getting back to circuit I asked CFI about carb heat, do I use it or not and when. Long and short of it was if its there use it, so I pulled out the Cabin Heat knob didn't I!! Did the same thing in a grumman AA5. And that dose have a card heat! It stumped me and the instructor to the piont of taking it back to get it probably looked at... After a couple more trieds we both clicked to what I was doing and had a good laugh about it. Thakns H :yin_yan: Link to comment Share on other sites More sharing options...
Yenn Posted January 27, 2009 Share Posted January 27, 2009 I have for a long time changed my pre take off checks, so that the last check is a power check, looking for a minimum of 2700rpm and the mag check is done immediately prior to that. I have never tried for full power with carby heat on so I cannot be sure that it would not get to the required revs. Will give it a go next time I fly. Link to comment Share on other sites More sharing options...
Bigglesworth Posted January 27, 2009 Share Posted January 27, 2009 I did it once in a 150, and realised in time to clear the hills at the end of the rwy. With it on it probably wouldn't have. With the Jab motor in the Cheetah it has negligible difference at low level, but when crossing the range at 9500, I checked for ice before going over bad country, and noticed a large drop in power. Actually I didn't do this, I crossed at below 5000 feet (as the book says) and got a good view of the underneath of the mountain tops.;) Link to comment Share on other sites More sharing options...
ianrat Posted January 28, 2009 Share Posted January 28, 2009 Carby heat Temp Can any one tell what temps would be going throught the carby system while using Carb Heat. Thank you Ianrat Link to comment Share on other sites More sharing options...
slartibartfast Posted January 28, 2009 Share Posted January 28, 2009 My carby normally runs about 8-12 degrees in summer. When I turn on carb heat, it keeps on warming up until I turn it off - normally at about 20. It warms pretty quickly. I think I've let ot go to 25 before. The other day I stopped for half an hour and left it standing on the apron in about 34 degrees ambient. When I restarted, the carb temp was over 30. It soon cooled down with fuel flowing through it. To answer your question (not) - it would depend on the installation. Plenty warm enough to melt ice though. Link to comment Share on other sites More sharing options...
ianrat Posted January 28, 2009 Share Posted January 28, 2009 Thank you. The system that i intend to use on my 601XL has the heat coming in before the air cleaner. I was worried that if it got to hot it may damage the filter. I do not think 25 would do this. Thank you Ianrat Link to comment Share on other sites More sharing options...
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