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Aviation Forum / General / Aviation / September 2008Carb heat: my new policy. Any comments
Flying a lot of 152s and 172s with carb heat lately. When inbound, I've been taught to pull the carb heat "on" downwind, hey actually use it as a power control to slow the plane just a bit mid-field, and then more importantly, just leave the thing on till clear of the runway and cleaning up. No matter what the temp, humidity. And to have it on at all times when the RPM is less than the green band. Kind of a preventative. A few times I have been coming in on short final and needed a burst of power due to a sudden downdraft, or needed to pour on a little juice cause my approach was coming up just a bit short. Moving the throttle forward 1/4 to 1/2 inch, i.e. giving it a little juice but certainly not a go around type of thing, often times I would get a stumble, hicuup, drop in RPM'S for 2-3 seconds before the horses responded. Lot of convective turb lately and that power really comes in handy at times on mid to short final. Kind of a shocker when the engine doesn't respond quite nicely. This has happened on a few birds, especially on hot days. I think what's happening is the engine is just too rich, hey I've got the mixture all the way in, it's hot (air less dense), and it's (way) hotter with the carb heat on ( air much less dense), all enriching the mixture, and when I put on a little power the accelerator pump in the carb over-enriches the engine for just a little bit; causing the stumble. Other pilots and the A&P just tell me to pour on the power a little slower. I think I'm going to follow a new SOP. Turn the carb heat off on mid-final. Reasoning: no carb, esp a warm one is going to ice up in 30 seconds, sets me up better for a go-around, and will prevent this stumble business (I did test it out at altitude, and it prevents or at least seriously mitigates the stumble). thoughts? T > Flying a lot of 152s and 172s with carb heat lately. When inbound, I've > been taught to pull the carb heat "on" downwind, hey actually use it as a [quoted text clipped - 32 lines] > thoughts? > T Shouldn't be a problem, but sometimes it happens. Apply power a little slower. or Carry just a tiny bit of power on final. Sounds like you might be approaching at cut off. or Bump a little power every 15 to 20 seconds to keep the engine clear. Personally I wouldn't cut the carb heat. >> Flying a lot of 152s and 172s with carb heat lately. When inbound, I've >> been taught to pull the carb heat "on" downwind, hey actually use it as a [quoted text clipped - 42 lines] > or > Bump a little power every 15 to 20 seconds to keep the engine clear. Neither of which would do anything to prevent potential problems. > Personally I wouldn't cut the carb heat. Because flight sim doesn't care either way. >> Flying a lot of 152s and 172s with carb heat lately. When inbound, >> I've been taught to pull the carb heat "on" downwind, hey actually [quoted text clipped - 46 lines] > > Personally I wouldn't cut the carb heat. that's because hpyu have no idea of what you're talking about. Bertie > Flying a lot of 152s and 172s with carb heat lately. When inbound, I've > been taught to pull the carb heat "on" downwind, hey actually use it as [quoted text clipped - 31 lines] > thoughts? > T Best practice without a lot of experimentation is to follow the POH, but I can tell you from personal experience full rich mixtures on final at high density altitudes (or takeoffs, for that matter) give far from best performance. The knob of choice might be mixture, not carb heat, especially since you may have really low manifold pressures on final, and that could cause some ice. I'm remembering things from a lot of years ago, I fly behind an injected engine now. On Sep 6, 2:40 pm, a <papp...@gmail.com> wrote:> > Best practice without a lot of experimentation is to follow the POH, I hope I never let my rookie a.s become so confident I consider deviating from the POH based on my own anecdotal experience. Next thing you know, you're an example of someone who made reasonable conclusions except for a heretofore unknown exception. There's a certain risk factor, also, I think, in deviating from one's training and, I assume in this case, longtime practice. The OP doesn't mention their typical strip, but I think they would be best served by adhering to the POH and just aiming a little further down the runway. ----- - gpsman > On Sep 6, 2:40 pm, a <papp...@gmail.com> wrote:> >> Best practice without a lot of experimentation is to follow the POH, [quoted text clipped - 13 lines] > > - gpsman This is excellent advice and I add my voice to what you have said. General aviation engines particularly Lycoming and Continental, handle carb ice just differently enough that every aircraft POH should be checked to see what the engine manufacturer recommends pertaining to the use of carb heat, especially the exact circumstances where it is recommended and the suggested procedure for it's use. Pilots who alter the manufacturer's recommendations on the use of carb heat anticipating a go around situation are potentially creating a problem where no problem should exist. There is no reason at all why a go around should necessitate an action with carb heat that deviates from recommended procedure. If you have to go around, simply follow recommended procedure.  SignatureDudley Henriques Couple things I want to add to some of the (kind of) opinionated but helpful replies in this thread. My C152 POH, and this is a late -70s model, does not give a clear cut protocol for use of carb heat. It basically says use it when icing is possible or suspected. I think it's standard practice to pull it on power reduction for approach, but as you can see from the replies here there are a variety of standard practices. If I read the POH literally, I'd say turning the heat off when on short final is not contrary to what it says, and is not really more in line with its suggestions than leaving it full on till clear of the runway or go-around power is needed. Does one suspect carb ice in the last 30 seconds of approach? Well there are some anecdotes in this thread that raise the possibility of that, so maybe I won't do this practice anyways, but either way there isn't a sentence in the POH that says to leave that carb heat on till the wheels are on the ground. By the way, the topic of leaning on downwind for approach under high density altitude conditions was brought up in this thread. The C152 POH is almost silent on that also. It talks about leaning in cruise, leaning for max rpm in a full power static runup when over 3000 DA, and to place the mixture rich or "for smooth operation" on approach. I've been taught the former, but another very experienced CFI told me to lean it out "an inch" and push it in only if you need to go around. Both pieces of advice I'd say consistent with the POH text, and both different. FYI, the engine stumble in the original post happens at about 2000 DA days. Just to go off on this tangent, one CFI I has says absolutely avoid operating your Cessna Lycoming less than 1,000 RPM -- not enough oil pressure to lube up the beast, and in fact there is an examiner that will demerit you if you taxi at less than 1000 RPM on your checkride. Now another CFI is adamant about taxiing at minimum possible power -- to save the brakes. Both very respectable experienced CFI's, both with reasons for their suggestion. And both suggestions are "not contrary" to the POH guideline. So sometimes you gotta use your brain to determine a good SOP, and solicit info on the pros / cons / risks to make your own decision. But I'm not bending any of the guidelines in the thin POH. And as far as taking it to the A&P... We've talked about this. He says, well grasshopper, you go the mixture full rich, it's hot, and you punch in the throttle -- this is a carb engine, they sometimes stumble. It's also pretty accepted performance around here by some of the other more experienced pilots -- there recommendation is in line with a few of the posts here -- some combination of: don't pull the throttle to cutoff, lean it out on downwind, push in the carb heat on short final, push the throttle in more slowly, and/or don't worry about the momentary hesitation / stumble , it'll get ya used to the power delay when you get flying turbofans. That last one a little tongue in cheek.... T >> On Sep 6, 2:40 pm, a <papp...@gmail.com> wrote:> >>> Best practice without a lot of experimentation is to follow the POH, [quoted text clipped - 3 lines] >> thing you know, you're an example of someone who made reasonable >> conclusions except for a heretofore unknown exception. > This is excellent advice and I add my voice to what you have said. > General aviation engines particularly Lycoming and Continental, handle > carb ice just differently enough that every aircraft POH should be > checked to see what the engine manufacturer recommends pertaining to the > Couple things I want to add to some of the (kind of) opinionated but > helpful replies in this thread. [quoted text clipped - 59 lines] > > carb ice just differently enough that every aircraft POH should be > > checked to see what the engine manufacturer recommends pertaining to the Take a look at your oil pressure gauge as you change RPMs. If it stays acceptable, the engine manufacturer says there's enough oil pressure. If you are running at low manifold pressures you have set up a condition for carb icing, haven't you? I'd suggest it would be prudent when landing to keep the carb heat on until touchdown, or until you decide to go around. As has been pointed out here, carb heat and throttle can be operated with one hand when advancing the throttle. Why take the chance of growing some ice just when a deer runs on the runway 500 feet in front of you while you're in the flare? Or, more likely, someone has finished their run up and is taxiing out when you're on short final? You have the carb heat on as insurance you'll get power when you need it, don't cancel the policy prematurely. Keep in mind this is written by someone who flies an injected engine! > If you are running at low manifold pressures you have set up a > condition for carb icing, haven't you? I'd suggest it would be prudent [quoted text clipped - 8 lines] > >Keep in mind this is written by someone who flies an injected engine! How fast does carb ice form? If you've had carb heat on from abeam the numbers in the downwind, is ice going to form from short final to flare? I usually leave mine on to touchdown, but a CFI-friend shuts off carb heat when on short short-final in anticipation of a possible go-round. Keep in mind this is written by someone who flies in Arizona! > Couple things I want to add to some of the (kind of) opinionated but > helpful replies in this thread. [quoted text clipped - 59 lines] > > carb ice just differently enough that every aircraft POH should be > > checked to see what the engine manufacturer recommends pertaining to the If the POH says to lean for smooth operation on downwind, then do it if the carb heat makes it stumble. These carbs are designed to provide a rich mixture at sea level, and when the DA is higher than that the fuel:air mix can become too rich to run properly. WE operate at a 3000' airstrip and the DA is at 5000' or more almost all summer. You learn something about mixture, and you learn about carb ice on clear days, too. Lycoming's service manuals call for an idle setting of 650-750 RPM. I think they know a little bit about lubrication and so on, a lot more than that CFI knows about engines. 1000 RPM is way too high and just burns out brakes. The only place 1000 RPM should be used is when the engine has been started from a cold-soaked state, and the oil is still thick enough that it doesn't throw onto the cylinder walls too well. Once it's warmed up some it's OK. If the oil pressure is falling off badly at 650 RPM, the engine's bearings or oil pump or both are shot and it shouldn't be flying. While we're on the subject of dragging the brakes to control speed, if you go on to get a Commercial ticket and do that to expensive airplanes, you might find yourself looking for another job. Overheated brakes have been known to set fire to tires and the whole airplane goes up in smoke. As far as approaches go, we use the "plan-for-abort-unless- everything's-good" training. Most landing accidents are a result of a refusal to go around when things aren't lining up properly. Airspeed, altitude, track---everything must be within reason or we just don't land. SO, the carb heat is left on until we accelerate to get out of there, and we don't slam the throttle open, either. Besides risking stumble or outright failure, it's hard on the engine when cylinder pressures rise so high at low RPM. Take two seconds to open the throttle unless things are really urgent. Dan pretty accepted performance around here by some of the other more > experienced pilots -- there recommendation is in line with a few of the > posts here -- some combination of: don't pull the throttle to cutoff, > lean it out on downwind, push in the carb heat on short final, push the > throttle in more slowly, and/or don't worry about the momentary > hesitation / stumble Sounds pretty reasonable; you can't blame every engine stumble on carb icing (or carb heat), and I remember watching a fellow student do go-arounds and hearing the hiccup as he jammed in full power in the "go" part of each touch-and-go. > pretty accepted performance around here by some of the other more >> experienced pilots -- there recommendation is in line with a few of [quoted text clipped - 7 lines] > go-arounds and hearing the hiccup as he jammed in full power in the "go" > part of each touch-and-go. I'd say a vast amount of engine "hiccups" on a go around are caused not by carb heat but rather by over aggressive use of throttle. SMOOTH is the key word for throttle use on a go around. Aggressive throttle use might get you a "hiccup" in a 150 Cessna. It might even cause an engine failure. It can kill you in a high performance prop airplane. SignatureDudley Henriques > I'd say a vast amount of engine "hiccups" on a go around are caused not > by carb heat but rather by over aggressive use of throttle. SMOOTH is > the key word for throttle use on a go around. Aggressive throttle use > might get you a "hiccup" in a 150 Cessna. It might even cause an engine > failure. It can kill you in a high performance prop airplane. The hiccup is only one part of the risk when shoving the throttle in too fast, too. When high manifold pressures are applied at low RPM, the cylinder pressures get much too high and detonation becomes a danger. Broken pistons and rings and other cylinder parts can all result from this, as can overloaded bearings. The propeller is a very heavy flywheel and we can't expect the same acceleration we get in our cars. Further, even old cars had variable ignition timing that would drop the spark advance to 10 or 6 degrees BTDC during acceleration to avoid detonation, but our LyConts don't have that and are stuck at 20 or 25 or 28 or whatever degrees. The pilot will never hear the pinging because of all the other racket, but it's there if they get too rough with the throttle. Dan >> I'd say a vast amount of engine "hiccups" on a go around are caused not >> by carb heat but rather by over aggressive use of throttle. SMOOTH is [quoted text clipped - 16 lines] > > Dan As a pilot of Warbirds through the years I've run into the problem consistently when advising new pilots on how to handle these airplanes. Some SE warbirds will actually torque roll if high MP is applied on a go around with the prop in full increase (Low pitch/high RPM), if the power is ham handed in with the airplane under about 120 with high AOA involved in the power up equation. SignatureDudley Henriques >>> I'd say a vast amount of engine "hiccups" on a go around are caused not >>> by carb heat but rather by over aggressive use of throttle. SMOOTH is [quoted text clipped - 23 lines] > is ham handed in with the airplane under about 120 with high AOA involved > in the power up equation. Oh brother, here we go again. >>>> I'd say a vast amount of engine "hiccups" on a go around are caused not >>>> by carb heat but rather by over aggressive use of throttle. SMOOTH is [quoted text clipped - 24 lines] > > Oh brother, here we go again. Well hello Max. What took you so long? :-) SignatureDudley Henriques > Flying a lot of 152s and 172s with carb heat lately. When inbound, I've > been taught to pull the carb heat "on" downwind, hey actually use it as > a power control to slow the plane just a bit mid-field, and then more > importantly, just leave the thing on till clear of the runway and > cleaning up. Never heard of this before. > I think I'm going to follow a new SOP. Turn the carb heat off on > mid-final. Tha't what I've always been taught. Actually, I do it on short final. There will come the day when you need full power for the go-around. Too silly if you then have the carb heat on. I was taught to push in the carb heat with my thumb while advancing the throttle for a go-around. >> Flying a lot of 152s and 172s with carb heat lately. When inbound, I've >> been taught to pull the carb heat "on" downwind, hey actually use it as a [quoted text clipped - 10 lines] > There will come the day when you need full power for the go-around. Too > silly if you then have the carb heat on. >I was taught to push in the carb heat with my thumb while advancing the >throttle for a go-around. [quoted text clipped - 13 lines] >> There will come the day when you need full power for the go-around. Too >> silly if you then have the carb heat on. Yeah, same here. > I was taught to push in the carb heat with my thumb while advancing the > throttle for a go-around. That won't work so well in a Piper. You need to do one, then the other. ... Alan SignatureAlan Gerber PP-ASEL gerber AT panix DOT com > There will come the day when you need full power for the go-around. Too > silly if you then have the carb heat on. Then again, how hard is it to shove in the carb heat knob while you advance the throttle in a Cessna? They are right next to each other. I have always just pushed in the carb heat handle at the same time as I advance the throttle, not that difficult to do, even using the same hand. Randy L. SignatureRemember: Any landing that you can walk away from, is a landing that you can be fined, sued, or prosecuted for. > Flying a lot of 152s and 172s with carb heat lately. When inbound, I've > been taught to pull the carb heat "on" downwind, hey actually use it as a [quoted text clipped - 32 lines] > thoughts? > T What's going to happen if you actually do have carb ice which hasn't burned off by the time you turn carb heat off? I'd much rather attempt a go around with the carb heat initially on than attempt a go around with the lingering effects of carb ice. I have no idea what DA you're talking about, but what you're describing is trying to correct a problem with the mixture by controlling it with the carb heat. If you're landing at a high DA airport, you shouldn't have the mixture full rich. Setting the mixture on downwind is the solution to the problem. On a 152 or 172 you can also have your hand on the throttle with your thumb on the carb heat. It should be a natural reaction to push both in together or push the carb heat in first on a go around. > Flying a lot of 152s and 172s with carb heat lately. When inbound, I've > been taught to pull the carb heat "on" downwind, hey actually use it as [quoted text clipped - 31 lines] > thoughts? > T We seem to do things differently in Oz, We dont start slowing down till after we turn base, then apply carby heat and pull power (usually to about 1500 -1700 rpm in the Cessnas). On short final when sure of making it in, we turn off carby heat so we are ready to do a quick go around if a kangaroo hops onto the runway. But I guess you guys dont have kangaroos. :<) Terry PPL Dowwnunder > On short final when sure of > making it in, we turn off carby heat so we are ready to do a quick go > around if a kangaroo hops onto the runway. But I guess you guys dont > have kangaroos. :<) We have some in the zoos, but they don't usually make it out to the airports. What we do have, though, is deer. I just did a go-around yesterday because they were having dinner right at the edge of the runway. ... Alan SignatureAlan Gerber PP-ASEL gerber AT panix DOT com > Flying a lot of 152s and 172s with carb heat lately. When inbound, > I've been taught to pull the carb heat "on" downwind, hey actually use [quoted text clipped - 31 lines] > stumble business (I did test it out at altitude, and it prevents or at > least seriously mitigates the stumble). Lycomings, no problem with your plan at all. Continentals ice a bit more easily, and on a clear dry day, there won't be a problem either, though I'd be inclined to leave it on just a bit longer. I'd also get in the habit of pushing the carb heat in with the throttle if you go around.. Bertie > Lycomings, no problem with your plan at all. Continentals ice a bit more > easily, and on a clear dry day, there won't be a problem either, though > I'd be inclined to leave it on just a bit longer. I'd also get in the > habit of pushing the carb heat in with the throttle if you go around.. > > Bertie Your a dumb a.s. What next, practicing emergency landings by turning off the fuel? If you don't like an engines throttle response with carb heat on, turning off the carb heat is NOT the solution. There are far too many safe ways to deal with the issue, other than deviation from the POH. >> Lycomings, no problem with your plan at all. Continentals ice a bit >> more easily, and on a clear dry day, there won't be a problem either, [quoted text clipped - 9 lines] > If you don't like an engines throttle response with carb heat on, > turning off the carb heat is NOT the solution. Didn't say it was, fjukkktard. Bertie >>> Lycomings, no problem with your plan at all. Continentals ice a bit >>> more easily, and on a clear dry day, there won't be a problem either, [quoted text clipped - 13 lines] > > Bertie Liar. Are you so stupid you can't follow a thread one post long. >>>> Lycomings, no problem with your plan at all. Continentals ice a bit >>>> more easily, and on a clear dry day, there won't be a problem either, [quoted text clipped - 15 lines] > > Liar. Are you so stupid you can't follow a thread one post long. Hey Okie, crank up that one brain cell and explain how he ever proposed such a solution to the problem you just pulled out of your a$$? Pushing in the carb heat with the throttle on a go around is taught by, hmmm let's see here 1,2,...251...carry the 4, uhm every friggin CFI on the face of the earth to every 2 hr+ student pilot on the face of the earth (assuming it was missed in the first hour). Jeez you are one dumb-as-a-day-old-dog-turd Okie, and only prove over and over again that you have exactly zip experience when it comes to planes that don't have a 101 keyboard and a mouse attached as standard equipment. I can see why you rarely offer anything of a substantive nature in this NG, which in your case demonstrates rare intelligence because you can't possibly do as much without stepping on your dork. >>> Bertie >> [quoted text clipped - 14 lines] > NG, which in your case demonstrates rare intelligence because you can't > possibly do as much without stepping on your dork. Thanks for confirming that you can't either. >>>> Bertie >>> [quoted text clipped - 16 lines] > > Thanks for confirming that you can't either. Ah yes, the old tried-and-true "I'm rubber, you're glue" line again. I'm sure you think you're quite the wit for employing that defense and to give credit where credit is due, you are half right. >>>>> Bertie >>>> [quoted text clipped - 21 lines] > I'm sure you think you're quite the wit for employing that defense and to > give credit where credit is due, you are half right. Then address the issue, dumb a.s. >>>>>> Bertie >>>>> [quoted text clipped - 23 lines] > > Then address the issue, dumb a.s. I already did, you subliterate Okie, and well before your ad nauseum "Yes, exactly" responses to posts you had no hope of comprehending. Intelligence may have its limits, but you're a living testament to the fact that stupidity doesn't. >>>>>>> Bertie >>>>>> [quoted text clipped - 30 lines] > Intelligence may have its limits, but you're a living testament to the > fact that stupidity doesn't. You're a liar. >>>>>>>> Bertie >>>>>>> [quoted text clipped - 33 lines] > > You're a liar. How do I know you're not lying? >>>> Bertie >>> [quoted text clipped - 18 lines] > > Thanks for confirming that you can't either. For f.ck's sake Maxie, you can't even do a decent IKYABWAI post. Bertie >>>> Lycomings, no problem with your plan at all. Continentals ice a bit >>>> more easily, and on a clear dry day, there won't be a problem either, [quoted text clipped - 15 lines] > > Liar. Are you so stupid you can't follow a thread one post long. Yeh, right wannabe boi.. Bertie > Lycomings, no problem with your plan at all. Continentals ice a bit more > easily, and on a clear dry day, there won't be a problem either, That observation is in conflict with my experience. Everytime I've gotten carb ice in the pattern has been on a clear day. -Robert "Robert M. Gary" <N7093v@gmail.com> wrote in news:89362f56-85b0-46be-b33f- 2cf3be313f94@v16g2000prc.googlegroups.com: >> Lycomings, no problem with your plan at all. Continentals ice a bit more >> easily, and on a clear dry day, there won't be a problem either, > > That observation is in conflict with my experience. Everytime I've > gotten carb ice in the pattern has been on a clear day. But not a clear dry one. Bertie > > That observation is in conflict with my experience. Everytime I've > > gotten carb ice in the pattern has been on a clear day. > > But not a clear dry one. Well ok. Dry in the sense of visible moisture; yes, no visible moisture. However, we know that humidy is the key to carb ice so there had to be some humidy. But what type of solution is that? You teach students to subtract the dew point from the temp in order to decide when to turn off carb heat. That just sounds complicated for little gain. -Robert > Well ok. Dry in the sense of visible moisture; yes, no visible > moisture. However, we know that humidy is the key to carb ice so there > had to be some humidy. But what type of solution is that? You teach > students to subtract the dew point from the temp in order to decide > when to turn off carb heat. That just sounds complicated for little > gain. It's not complicated. If the temp and dewpoint are 3 or 5 or 8 degrees (Celcius) apart, ice is likely. If they're 25 degrees apart, it's not. Anyone can print out the carb ice risk chart (Google "carb ice") and stick it where it's handy. Here in Canada, the regs say this: "602.72 The pilot-in-command of an aircraft shall, before commencing a flight, be familiar with the available weather information that is appropriate to the intended flight." I would imagine the FAA has something equivalent to that. So some sort of weather information is mandatory, and that would include temp and dewpoint. There's no excuse for being surprised by carb ice. None at all. Like I tell my students, "You wouldn't dive into water without making sure there were no hazards in it that might injure you (hard or sharp pointy things under the surface, predators, and so on) and that it wasn't one degree above freezing. Why would we take off into air about which we know nothing? Dan >> Well ok. Dry in the sense of visible moisture; yes, no visible >> moisture. However, we know that humidy is the key to carb ice so there [quoted text clipped - 24 lines] > > Dan You want to argue awareness of conditions to justify dropping carb heat, when dropping carb heat is not necessary to solve the OP's issue? >>> Well ok. Dry in the sense of visible moisture; yes, no visible >>> moisture. However, we know that humidy is the key to carb ice so there [quoted text clipped - 27 lines] > You want to argue awareness of conditions to justify dropping carb heat, > when dropping carb heat is not necessary to solve the OP's issue? You're an idiot, control freak boi. Bertie On Sep 8, 5:53 pm, Dan_Thomas_nos...@yahoo.com wrote: > So some sort of weather information is mandatory, and that > would include temp and dewpoint. There's no excuse for being surprised [quoted text clipped - 3 lines] > and so on) and that it wasn't one degree above freezing. Why would we > take off into air about which we know nothing? An awareness of carb ice conditions is one thing; but you are advocating teaching two different landing techniques as a result. To me that is too complex for students and unnecessary. Just keep it simple; use the same approach technique regardless of carb icing conditions. -Robert On Sep 8, 12:54 pm, Bertie the Bunyip <T...@ld.you> wrote: > > That observation is in conflict with my experience. Everytime I've > > gotten carb ice in the pattern has been on a clear day. > > But not a clear dry one. Well ok. Dry in the sense of visible moisture; yes, no visible moisture. However, we know that humidy is the key to carb ice so there had to be some humidy. But what type of solution is that? You teach students to subtract the dew point from the temp in order to decide when to turn off carb heat. That just sounds complicated for little gain. -Robert Exacty. > On Sep 8, 12:54 pm, Bertie the Bunyip <T...@ld.you> wrote: > [quoted text clipped - 9 lines] > when to turn off carb heat. That just sounds complicated for little > gain. You're an idiot, Maxie. Go play wiht your guns. Bertie "Robert M. Gary" <N7093v@gmail.com> wrote in news:41382e98-ee2e-45a8- 8e04-0440d8faa5fb@b38g2000prf.googlegroups.com: >> > That observation is in conflict with my experience. Everytime I've >> > gotten carb ice in the pattern has been on a clear day. [quoted text clipped - 7 lines] > when to turn off carb heat. That just sounds complicated for little > gain. Yeah, of course.I wasn't offering it as a solution, though. My statement was a bit vaue, though. Here's what I actually do. With a small continental I would pull the carb heat on downwind a good bit before I pulled the power. I'd leave it on through the approach and kncok it off very short finals, when I have a moment to knock i off. If I thought it was a good day for carb ice, I might leave it on through the landing. If I'm not flying that particular airplane a lot, I might forget, but I do make a rule of locating it in relation to the throttle so that I can push it off if I have to go around. Most airplanes have it arranged so that it's easy to do that with the notable exception of quadrant cherokees. Stearmans are also a PITA if you're in the rear cockpit. If reaching it without distracting yourself form the primary task of flying the airplane is a problem, I either get rid of it early on if the engine is not particularly susceptible, like a cherokee, for instnace, or I'd just leave it on and live with the performance decrement, like in a W670 powered Stearman. Better 90% power than none at all. I used to fly a lot of old airplanes and carb heat was always applied often so I haven't gotten it very often at all. I have gotten it a few tims with Continentals, Wrights and Pratts, but I can't remember a single instance of carb ice on a modern Lycoming. Not to say it couldn't happen. Bertie Bertie > I think I'm going to follow a new SOP. Turn the carb heat off on > mid-final. Reasoning: no carb, esp a warm one is going to ice up in 30 > seconds, sets me up better for a go-around, and will prevent this > stumble business (I did test it out at altitude, and it prevents or at > least seriously mitigates the stumble). Don't put any money on that bet. I've had carbs freeze up on me during stop-n-goes from the time it takes to kick off the heat to the time it takes to pour on the coals. The carb can freeze in seconds. -Robert, CFII >> I think I'm going to follow a new SOP. Turn the carb heat off on >> mid-final. Reasoning: no carb, esp a warm one is going to ice up in 30 [quoted text clipped - 7 lines] > >-Robert, CFII I'm with you Bob. I once thought I'd throttle back and poke under some mist and pop out the other side and resume. when the power came off the revs started dropping and dropping and dropping. I bunged on full carb heat and then full throttle and still the revs kept dropping. out the corner of the eye I noticed a shaft of sunlight and turned toward the hole in the mist. about 2 seconds into the sunlight and I had full power back again. when it happens it happens quickly. now back to the op's description of a rev drop on opening the throttle. my bet is that the carb has been in service for quite a while and the leather bucket seal on the accelerator pump is knackered. it isnt giving the full squirt of fuel on acceleration. the other possibility is that the little jet pipe has moved out of the centre venturi position and the squirt isnt making it up into the inlet tubing. far better me thinks that he doesnt w.nk on creating new procedures and gets the a&p's to check the carby functioning. Stealth Pilot > I'm with you Bob. > I once thought I'd throttle back and poke under some mist and pop out [quoted text clipped - 16 lines] > > Stealth Pilot Very interesting points, which I plan to keep in mind when I return to flying. The only thing that I can add is that the results might be more reliable if the A&P is experienced in servicing carburetors--and possibly magnetoes as well. Peter (Having seen some poor work from folks who should have known better) On Sep 7, 5:53 am, Stealth Pilot <notranspon...@aeroplanes.com.au> wrote: > I'm with you Bob. > I once thought I'd throttle back and poke under some mist and pop out [quoted text clipped - 4 lines] > the mist. about 2 seconds into the sunlight and I had full power back > again. when it happens it happens quickly. I lost the engine in the J-3 once during climb out. I had done a stop- n-go and even though I was under full power I had picked up some carb ice after turning off the carb heat in order to go. I got down to about 200 feet before the power came back. Since then I've always done stop-n-gos will carb heat on until I get a positive climb. I've not had that problem since using that procedure. That procedure is in conflict with the OPs. Now, it is true that a J-3 is going to freeze up much faster than a Cherokee and somewhat faster than C-172 but it just shows that it can happen very, very fast. -Robert > I think I'm going to follow a new SOP. Turn the carb heat off on > mid-final. Reasoning: no carb, esp a warm one is going to ice up in 30 [quoted text clipped - 4 lines] > thoughts? > T Well that will make it easier on the crash investigators. They will see the carb heat in the off position and mark it down to carb ice caused by pilot error. Think of the money you will save the tax payers. > Flying a lot of 152s and 172s with carb heat lately. When inbound, I've I > think I'm going to follow a new SOP. Turn the carb heat off on mid-final. [quoted text clipped - 5 lines] > thoughts? > T Then again, how hard is it to shove in the carb heat knob while you advance the throttle in a Cessna? They are right next to each other. I have always just pushed in the carb heat knob at the same time as I advance the throttle, not that difficult to do, even using the same hand. Randy L. SignatureRemember: Any landing that you can walk away from, is a landing that you can be fined, sued, or prosecuted for. > Then again, how hard is it to shove in the carb heat knob while you advance > the throttle in a Cessna? They are right next to each other. I have always > just pushed in the carb heat knob at the same time as I advance the > throttle, not that difficult to do, even using the same hand. Bingo. Why risk carb ice just to not have to remember to push the carb heat in? -Robert >> Then again, how hard is it to shove in the carb heat knob while you advance >> the throttle in a Cessna? They are right next to each other. I have always [quoted text clipped - 5 lines] > > -Robert We have a similar thing going on right now in the Warbird community. After the McKitrick go around torque roll mort in his P51 last year, we have one very respected member of our community advocating making approaches in the P51 Mustang using cruise settings on the prop instead of the normal 2700RPM (Meto) setup used by pilots flying approach in this airplane. His theory is that on a go around, where torque is a huge issue on the Mustang if power is misused, keeping the prop in cruise won't hurt the engine if it's over boosted unintentionally and will deny the extremly high torque moment associated with the application of too much power too quickly. He maintains this "safety valve" will help save lives. I have a great respect for this pilot's opinion.....normally! As someone involved in the Mustang community as a safety adviser, I find his "theory" "interesting" to say the leat but I'm against it. Doing this flies in the face of the normal Dash 1 approved go around setup for the 51 which is to run the prop up to 2700 and DON'T ham hand the throttle if needed! It as well inserts a "crutch" for pilots flying this airplane that should NOT be needed. Proper checkout and proper handling of the airplane is the right approach to saving lives in the Mustang, NOT altering the way the airplane is normally flown to give those pilots flying it a "safety valve". I see a similarity in the approach to the two issues, the other being the use of carb heat here. SignatureDudley Henriques > We have a similar thing going on right now in the Warbird community. After > the McKitrick go around torque roll mort in his P51 last year, we have one [quoted text clipped - 20 lines] > I see a similarity in the approach to the two issues, the other being the > use of carb heat here. Geeez Dudley, how the hell did you get from dropping carb heat on short final, to an essay like this in only two posts? Put the O2 mask back on. >> We have a similar thing going on right now in the Warbird community. After >> the McKitrick go around torque roll mort in his P51 last year, we have one [quoted text clipped - 25 lines] > > Put the O2 mask back on. Well hello again Maxie. Never get tired of seeing your deeply incisive, informative and thoughtful posts. What's the deal with all the name changes though. Can't seem to make any sense out of why you bother doing it. Why not just post with the Maxwell moniker. Just wondering?? :-)) SignatureDudley Henriques > Well hello again Maxie. Never get tired of seeing your deeply incisive, > informative and thoughtful posts. Well I wish I could say the same about you. But you always have to drift the thread around until it all about you. What's the deal with all the name > changes though. Can't seem to make any sense out of why you bother doing > it. Why not just post with the Maxwell moniker. Just wondering?? > :-)) Only because the name Maxwell was too often forged. Maxwell was not my real name, so who cares, I'll just take another. I think thoughts and ideas are more important on the Usenet. But that's just me. >> Well hello again Maxie. Never get tired of seeing your deeply incisive, >> informative and thoughtful posts. [quoted text clipped - 12 lines] > I think thoughts and ideas are more important on the Usenet. But that's > just me. So in other words, you'd rather be known for your singular rock hard stupidity rather than your first NG nym, which was a sock puppet to begin with. Do you really expect your delusional and incoherent ramblings to be interpreted as anything more than a monument to your stupidity? >> Well hello again Maxie. Never get tired of seeing your deeply incisive, >> informative and thoughtful posts. [quoted text clipped - 12 lines] > I think thoughts and ideas are more important on the Usenet. But that's just > me. That makes sense. Thanks for the explanation. On thread creep; there are actually two entirely seperate issues in play with this thread as I see it. One of the issues, and one that has been addressed by others as well as myself, is the issue of changing or altering a normal and or published procedure, in this case as the initial poster put it, "setting up a new SOP". What I'm dealing with is simply the "changing of normal procedure" issue. FWIW, I usually draw examples from either past or present personal experience when posting on these forums. I'm sorry you have chosen to see this as my "blowing my own horn". I assure you this is not now nor has it ever been my intention to do that. It's an unfortunate byproduct of Usenet that there will be those who for one reason or another, find someone as you appear to have found me. Sorry you feel this way. I'm fairly certain that under different circumstances, we might have had useful aviation related information to share with each other. SignatureDudley Henriques > That makes sense. Thanks for the explanation. > [quoted text clipped - 13 lines] > circumstances, we might have had useful aviation related information to > share with each other. Sorry, but that wasn't much help. >> That makes sense. Thanks for the explanation. >> [quoted text clipped - 15 lines] > > Sorry, but that wasn't much help. For once you're right. SignatureDudley Henriques |
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