kgwilson Posted November 13, 2015 Posted November 13, 2015 Those of us old codgers GA trained, and with indelible use of carb heat imprinted on our brains as well as engine management techniques to avoid over heating during climbs and shock cooling during descents etc wonder why a lot of theses issues happen within the RA fraternity. One of my theories is that it has a lot to do with RA training and the modern idea that you just turn it on and do whatever you like and it just goes. Many people have never lifted the bonnet of their car. This is done by the mechanic, sorry automotive technician. This attitude has found its way into aviation and regardless of the BAK or what I did called "Aircraft Technical Knowledge" they just expect everything to work like it does in the family car. They fail to understand that an aero engine is running at full power or 75% power most of the time. The car is running at about 20% of full power most of the time & unless you are a hoon, rarely at full power. The 912 is far more forgiving to poor treatment with its skidoo heritage & liquid cooled heads but the pure air cooled engine does not like being overheated or too rapidly cooled at all and is unforgiving to those who treat them so. Too many RAA pilots do not treat their aero engines as an aero engine should be treated. Why? I think it is partially due to the failure of the training fraternity to impress the importance of this to students and that many students assume that it is just the same as a modern car with all the bells & whistles but it flies. 4 2
Admin Posted November 13, 2015 Posted November 13, 2015 Guys, I have spent an enormous amount of time trying to clean this thread up...may not have done it properly or to your liking but please when posting, refresh yourself to the opening post and what the thread is about. If you wish to go off on tangents then start a new thread about the topic you wish to bring up. And, irrespective of whether you disagree with what another site member has posted, by all means disagree BUT state the reasons of why you disagree and NOT play the user 1 1
biggles Posted November 13, 2015 Posted November 13, 2015 I make a practice of applying carby heat whenever the throttle is other than fully open .... Bob I think this is probably going too far. But I take your point.Given you are in victoria, maybe your air temperatures are usually fairly low although I would have thought your humidities would be generally fairly low too. Unlike up here in tropics. but if you run your engine at about 2900 rpm as Jabiru suggest then almost constantly have carb heat on. This will thin out the air and have you flying in a constant start of partial power. Will change your fuel air ratios so you will be running lean and maybe too lean - getting hotter CHT's (or maybe cooler if you are in the lean of peak band. ) But I'm sure you get my meaning. carb heat has downsides as well. So overall there is a sweet spot of range where you should be having carb heat on. Not too much and not too little. Had a few instances where I suffered icing when taxiing prior to take-off . I now apply carby heat immediately after starting and maintain until prior to run up checks , which I do as late as possible prior to take off. In reality the only other time I apply carby heat is when on approach to destination ..... Bob 1
facthunter Posted November 13, 2015 Posted November 13, 2015 The only problem with that is often the hot air is unfiltered. I adopted a system of power up, carb heat checked OFF every time. Not a bad idea if you use carb heat often. Also don't wear a jacket with bulky sleeves. I got into grief (nearly) once with the heat being put on by the sleeve catching it (Side throttle and carb heat)Nev
biggles Posted November 13, 2015 Posted November 13, 2015 The only problem with that is often the hot air is unfiltered. I adopted a system of power up, carb heat checked OFF every time. Not a bad idea if you use carb heat often. Also don't wear a jacket with bulky sleeves. I got into grief (nearly) once with the heat being put on by the sleeve catching it (Side throttle and carb heat)Nev Agree , but as you are aware all Jabs apart from a few very early ones, the air is filtered. Jab drivers are spoilt in this regard ..... Bob 1 2 1
Camel Posted November 13, 2015 Posted November 13, 2015 Jabiru carb heat is filtered so allows to be put on during taxi. I previously lived in the snowy mountains and one morning I taxied my C172 to the other end of strip and had done run ups when entering to backtrack, on take off carb ice became very evident with engine coughing and spluttering and my heart racing, carb heat applied and a paddock lined up, engine came good and proceeded to get back towards runway and climbed to a safe height, my concern that it was not absolute that it was ice and could have been fuel contamination or something else, I climbed 3000 feet above strip until I was happy and started my journey. Now I never take off unless I do basics checks before, eg carb heat, mixture , fuel tap and quantity, flaps and trim. A long period of taxi or holding is a recipe for carb ice. 1
facthunter Posted November 13, 2015 Posted November 13, 2015 Climbing above a strip in treed country is a good idea. Should be done more often. Nev 1
Roscoe Posted November 15, 2015 Posted November 15, 2015 Had a few instances where I suffered icing when taxiing prior to take-off . I now apply carby heat immediately after starting and maintain until prior to run up checks , which I do as late as possible prior to take off. In reality the only other time I apply carby heat is when on approach to destination ..... Bob I apply FULL Carb heat as power is reduced just before turning base, and close it on final in case of a go around. 1 3
Happyflyer Posted November 16, 2015 Posted November 16, 2015 Agree , but as you are aware all Jabs apart from a few very early ones, the air is filtered. Jab drivers are spoilt in this regard ..... Bob One of the reasons manufacturers use unfiltered air for carb heat is in case impact ice blocks the air filter. I don't know if Jabiru use the same filter for normal and carb heat operations. Probably not a concern in Australia but could be different in US or Europe. 1
facthunter Posted November 16, 2015 Posted November 16, 2015 Good point. You could get blocking of the air quite rapidly in freezing rain. Rhyme will cover it quickly. Some "experts" say put the heat on prior to reducing power for max effect. An idling engine soon doesn't have enough heat in the exhaust system. FULL on not on. Don't use little bit's of carb heat. Not enough may cause extra problems for you. Nev
Guest ozzie Posted November 16, 2015 Posted November 16, 2015 Some also have alternate air inlet, fuel injection engines usually have it.
DrZoos Posted November 16, 2015 Posted November 16, 2015 A wise old bloke at our club reckons if conditions are such that you need carb heat you are prob best to leave it on all the way to the ground...even if a go round is needed you generally only lose 50-70 rpm and in such conditions carb ice is far less safe than a 50-70 rpm drop at max revs... his other point was that leaving it on can warm the carb body on climb out and ensure your safe on the next approach, especially when its really needed... ???? sounded like good advice to me... adn my aircraft has ample power to be able to climb at 1000 fpm with carb heat on or not...
Nobody Posted November 16, 2015 Posted November 16, 2015 A wise old bloke at our club reckons if conditions are such that you need carb heat you are prob best to leave it on all the way to the ground...even if a go round is needed you generally only lose 50-70 rpm and in such conditions carb ice is far less safe than a 50-70 rpm drop at max revs... his other point was that leaving it on can warm the carb body on climb out and ensure your safe on the next approach, especially when its really needed... ???? sounded like good advice to me... adn my aircraft has ample power to be able to climb at 1000 fpm with carb heat on or not... Do what the POH for your aircraft says to do not some "wise old bloke". There are engines around that will have detonation issues if operated with the carb heat at full power and high ambient temp. 1
DrZoos Posted November 16, 2015 Posted November 16, 2015 Yeh im not auggesting in high ambient temps...but ihigh humidity and cooler temps it sounded like good advice... One also has to remember some POH is generally written as a once size fits all situation manual.. Eg they dont say anything about step climbing in hot conditions... but people do it...
facthunter Posted November 16, 2015 Posted November 16, 2015 Your carby won't keep warm for long once the Carb heat is not on. It, (the carburetter) works much the same as a refrigerator especially when a lot of fuel is going through it. I always check "throttle forward, heat off", myself. You definitely lose significant power with effective carb heat on. Possibly some heat systems are not adequate. If they are effective at removing and controlling ice they will reduce power output significantly. Somewhere there are stipulated temps that must be achieved with it on. Since the heat normally comes from the exhaust muff the idling motor is not very effective at supplying it, after a short time.. Nev
Guest ozzie Posted November 17, 2015 Posted November 17, 2015 A wise old bloke at our club reckons if conditions are such that you need carb heat you are prob best to leave it on all the way to the ground...even if a go round is needed you generally only lose 50-70 rpm and in such conditions carb ice is far less safe than a 50-70 rpm drop at max revs... his other point was that leaving it on can warm the carb body on climb out and ensure your safe on the next approach, especially when its really needed... ???? sounded like good advice to me... adn my aircraft has ample power to be able to climb at 1000 fpm with carb heat on or not... Try and do a go around in a C150 with carb heat on. lucky to get 100ft a minute.
DrZoos Posted November 18, 2015 Posted November 18, 2015 Yeh my stupid statement should have said "Excluding Cessna 15anything" in any temp over -50 with pilots >1kg and fuel > 500ml But i was mainly referring to our two engines Jabs and Rotax... Jabs I have little experience with , but most sub 600kg Rotax 912 should in lower temps cope easily and still climb at 1000ft/min+ even at mtow near sea level... 1
turboplanner Posted January 7, 2016 Posted January 7, 2016 What's this then? If only he'd had a nosewheel!
Guest ozzie Posted January 7, 2016 Posted January 7, 2016 Maybe this has something to do with the thread on Brakes.
facthunter Posted January 7, 2016 Posted January 7, 2016 I don't know what the DC-3 has to do with this thread. I believe the max retard on rejected take off is with stick forward and I know of some props being damaged by coarse braking, but to put it on it's nose might need a tailwind as well. Nev 1
Dave English Posted January 10, 2016 Posted January 10, 2016 Nobody has ever died in a Jab, unlike the many fatalities in other LSAs. We are taught to glide land at 60 Knts. I would rather be glide landing a Jab than most other airframes. 12 people died last year out of the 10 000 member RAA community including experienced pilots doing things they should have known better than attempting. I just dont get the Jab stigma when they have a proven track record of being the safest LSAs in the sky. Yes, 5% of the Jab engines had a failure in 2014, but several people died and none beacause of a Jab. 2
SDQDI Posted January 10, 2016 Posted January 10, 2016 Nobody has ever died in a Jab. Definitely not true, but having said i don't think many (if any) were attributed to an engine failure! I guess though that most people see an engine failure as an increased risk, inasmuch as you lose a few options once your donk goes clonk. This of course isn't a jab exclusive phenomenon. 4
Dave English Posted January 10, 2016 Posted January 10, 2016 Quote from Rod Stiff last year in Sport Pilot magazine Dec 2015 “I have tried to build a strong and safe aircraft and I reluctantly boast that in 23 years no one has been killed or seriously injured as a result of my doing,” he said at the time
facthunter Posted January 10, 2016 Posted January 10, 2016 If he built the world's best pushbikes , quite a few users would have died using them. Nev 1
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