Mixture leaning question.
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
Leaning is a subject that is only rivalled by the downwind turn in its ability to generate a heated discussion.
generally agree with the points you've made.
Now, how about we start a thread on leaning the engine DURING a downwind turn ???
Join Date: Aug 2006
Posts: 171
Likes: 0
Received 0 Likes
on
0 Posts
As Aviator says read the bloody manual.
For many of us- we have done an engineering exam before being endorsed/able to fly solo or with PAX on a new type. I don't care if you fly a C150 or a Cessna Citation- each has their own unique flight manual whether from 1965 or 2004 and each has the emergency procedures and systems sections (usually around 7-8 into it
).
Read this and you will know for yourself! At alot of schools- flying training schools i'm referring to- students get away with the most basic of knowledge and really don't know their planes limitations or characteristics until they build up some serious command time (like on a flyaway). Best to know it before one of these as an engine failure could occur at any time!
For many of us- we have done an engineering exam before being endorsed/able to fly solo or with PAX on a new type. I don't care if you fly a C150 or a Cessna Citation- each has their own unique flight manual whether from 1965 or 2004 and each has the emergency procedures and systems sections (usually around 7-8 into it
).Read this and you will know for yourself! At alot of schools- flying training schools i'm referring to- students get away with the most basic of knowledge and really don't know their planes limitations or characteristics until they build up some serious command time (like on a flyaway). Best to know it before one of these as an engine failure could occur at any time!
Join Date: Sep 2000
Location: Adelaide, South Australia
Posts: 394
Likes: 0
Received 0 Likes
on
0 Posts
It's all about temperatures IMHO. My aircraft has a 280hp Continental IO-550G in front, and the EGT gauge has a "blue band" for climb power (about 1450F), which requires continual leaning during climb.
For me, proper engine management is more important than what any POH might say, in that fuel/air ratio is adjusted to keep EGT and CHT in their normal operating ranges (and OIL temp as a consequense), whether iin climb, cruise or descent.
The primary tool to do that is the mixture control, and the need to use it is dictated by power setting (rate of heat input) and forward speed (rate of heat removal). Some aircraft have better cowling than others and heat removal is more efficient at high power settings (mine has no cowl flaps). Others are not so efficient, so at high power setting and lower forward speed the only way to cool the engine is use cowl flaps and unburnt fuel.
The subject of excess cooling is another one entirely......
For me, proper engine management is more important than what any POH might say, in that fuel/air ratio is adjusted to keep EGT and CHT in their normal operating ranges (and OIL temp as a consequense), whether iin climb, cruise or descent.
The primary tool to do that is the mixture control, and the need to use it is dictated by power setting (rate of heat input) and forward speed (rate of heat removal). Some aircraft have better cowling than others and heat removal is more efficient at high power settings (mine has no cowl flaps). Others are not so efficient, so at high power setting and lower forward speed the only way to cool the engine is use cowl flaps and unburnt fuel.
The subject of excess cooling is another one entirely......
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
Please please please please read the frickin flight manual, it really is irrelevant how old it is, it is there for a reason and anybody even thinking of flying any airplane without knowing the thing from cover to cover should not be in the air....(of course this is just my opinion so feel free to kill yourself at your own will).
The flight manual for my Auster is about as comprehensive as your post above.
Also, it still says to use "any good quality motor spirit", this despite the fact that "good quality motor spirit" these days often has a reasonable amount of ethanol as part of it's mix.
So, yes, RTFM but research to ensure that it's still valid....many are not.
Much has changed with respect to engine handling over the last forty years or so.
Also, it still says to use "any good quality motor spirit", this despite the fact that "good quality motor spirit" these days often has a reasonable amount of ethanol as part of it's mix.
The good stuff is very hard to find these days.
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
I'd disagree with that. Any motor spirit containing ethanol would be poor quality motor spirit.
The good stuff is very hard to find these days.
The good stuff is very hard to find these days.
Bit of a thread drift, but..
I'd be inclined to agree with you (ethanol mixes are still not permitted to be sold here in WA) but I believe that the term "good quality motor spirit" is so open to interpretation that no one really knows what it means.
Does it relate to freedom from sediments, water or what ???
We did use some "good quality motor spirit" many years ago in an old J1 Auster and ceased very quickly after we were plagued by fuel starvation issues caused by vapour locks.
Went back to good old Avgas VERY smartly and never had any further problems .
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
Just to show that conventional wisdom is........well, not wisdom. Why do we run/require/need rich mixtures at high power? Cooling you say? WRONG. The extraordinarily rich mixture is required to assure that detonation does not occur. The rich mixtures primary purpose is to slow the combustion rate and delay the peak pressure point, which eliminates the risk of detonation by reducing the pressure peak. This does, in fact, result in cooler operation, but that's actually a second-order effect of the delayed peak pressure point. If you could retard the ignition timing there would be no need for the extraordinarily rich mixture.
Join Date: Sep 2000
Location: Adelaide, South Australia
Posts: 394
Likes: 0
Received 0 Likes
on
0 Posts
Brian Abraham wrote:
Absolutely correct - where should I send the Tim Tams?
If you have a detonation meter in your panel you would use that to adjust your mixture, but otherwise the EGT and CHT (and your ears if you could hear above the noises) are the primary tools (when used properly) to avoid that situation.
Just to show that conventional wisdom is........well, not wisdom. Why do we run/require/need rich mixtures at high power? Cooling you say? WRONG. The extraordinarily rich mixture is required to assure that detonation does not occur. The rich mixtures primary purpose is to slow the combustion rate and delay the peak pressure point, which eliminates the risk of detonation by reducing the pressure peak. This does, in fact, result in cooler operation, but that's actually a second-order effect of the delayed peak pressure point. If you could retard the ignition timing there would be no need for the extraordinarily rich mixture.
If you have a detonation meter in your panel you would use that to adjust your mixture, but otherwise the EGT and CHT (and your ears if you could hear above the noises) are the primary tools (when used properly) to avoid that situation.
Join Date: Jun 2001
Location: Australia
Posts: 889
Likes: 0
Received 0 Likes
on
0 Posts
"Cooling"
Thanks for the post Brian - I stand corrected. Will try to remember in future...
I think the feature actually is called an economiser function though Mr Saigon, however much of a misnomer it may be. Perhaps you'll accept the advice from this famous flying training institution (not wishing to override Brian's excellent clarification above).
O8
I think the feature actually is called an economiser function though Mr Saigon, however much of a misnomer it may be. Perhaps you'll accept the advice from this famous flying training institution (not wishing to override Brian's excellent clarification above).
O8
Last edited by Oktas8; 18th Aug 2009 at 10:42.
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
...and for those of you "AFM is Gospel" bible-bashers, I challenge you to find anywhere in your AFM that this full-throttle auto-rich is even mentioned
None so blind as those that don't want to learn...
If you fly a normally aspirated, carburetted, fixed-pitch single, it'll take you about a minute at normal cruise settings to see where I'm coming from. Who knows, the few litres of fuel you save yourself by utilising a little knowledge, may one day be the difference...
I rest my case. Play on, kiddies.
If you fly a normally aspirated, carburetted, fixed-pitch single, it'll take you about a minute at normal cruise settings to see where I'm coming from. Who knows, the few litres of fuel you save yourself by utilising a little knowledge, may one day be the difference...
I rest my case. Play on, kiddies.
Join Date: Jan 2008
Location: turn L @ Taupo, just past the Niagra Falls...
Posts: 596
Received 0 Likes
on
0 Posts
Are you deliberately misrepresenting my words Brian Abraham?
So in the case of an aircraft with a mixture already set to full-rich, this device "economises" the mixture to what exactly? Full-rich??? Marvellous. Further, had the device not already enriched the mixture from that selected by the pilot to another, arbitrary uncontrolled value, there would be nothing for the device to do!!! In your infinite wisdom, perhaps you would explain to me exactly why there is no advice of this "feature" in any AFM available to the pilot? And again further, what benefit might one expect from manually enriching the mixture in addition to the (unknown, uncontrolled, uncommanded) enrichment applied by application of full throttle?
I've been an avid student of aviation for quite some time now Brian -but thanks so much for your advice! I will surely continue to keep an open mind and actively seek opportunities to further my education and shed light on those areas of which I'm ignorant -and even mistaken. For sure you won't see me throwing advice like "RTFM" about carelessly -the very prolific, oft-repeated "advice" that make me loose my cool and apparently, on occasion, some circumspection.
I'll certainly keep an eye open for those:
Haven't seen any literature on it at all in the last 30 years or so -although I do confes I haven't searched for it directly in damn near as long either... Perhaps you could direct me to some please? That'd be a valuable addition to my library. Kinda strange there's no mention of it in the AFM of aircraft equipped with these carbs don't you think?
I have of late been maintaining my circumspection Brian, refraining from the types of personal attacks that used to characterise these pages Brian; instead preferring to try to assist by pointing people to the little snippets of information that may benefit or direct towards further learning. How's your circumspection holding up Brian?
Originally Posted by Brian Abraham
Called such by Marvel because it leans the mixture on reduction from full throttle.
I've been an avid student of aviation for quite some time now Brian -but thanks so much for your advice! I will surely continue to keep an open mind and actively seek opportunities to further my education and shed light on those areas of which I'm ignorant -and even mistaken. For sure you won't see me throwing advice like "RTFM" about carelessly -the very prolific, oft-repeated "advice" that make me loose my cool and apparently, on occasion, some circumspection.
I'll certainly keep an eye open for those:
Originally Posted by Brian Abraham
...pilot course notes regarding the operation of float carburettors...
I have of late been maintaining my circumspection Brian, refraining from the types of personal attacks that used to characterise these pages Brian; instead preferring to try to assist by pointing people to the little snippets of information that may benefit or direct towards further learning. How's your circumspection holding up Brian?
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
My circumspection is holding up fine, thanks for the concern.
Why in the hell would an AFM inform you of the principal of operation of a float carburettor? Point is, the role of the enrichment valve, or economiser as its called by some carburettor manufacturers, is covered by pilot course notes and you need a full understanding if you wish to have any hope of passing the exams. I thought from your post you were an experienced aviator, but seems from your last post you merely have an interest.
Well done, and an admiral pursuit, but what exactly is your background and experience.
And take a chill pill.
Kinda strange there's no mention of it in the AFM of aircraft equipped with these carbs don't you think?
preferring to try to assist by pointing people to the little snippets of information that may benefit or direct towards further learning
And take a chill pill.
Join Date: Jan 2008
Location: turn L @ Taupo, just past the Niagra Falls...
Posts: 596
Received 0 Likes
on
0 Posts
Originally Posted by Brian Abraham
Why in the hell would an AFM inform you of the principal of operation of a float carburettor?
Originally Posted by Brian Abraham
Well done, and an admiral pursuit, but what exactly is your background and experience.
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
Corkey, a second seat please, and get some beer in.
For those with no respect nor any REAL aviation experience (and REAL aviators who may wish a review).
For those with no respect nor any REAL aviation experience (and REAL aviators who may wish a review).
Join Date: Sep 2000
Location: Adelaide, South Australia
Posts: 394
Likes: 0
Received 0 Likes
on
0 Posts
RadioSaigon wrote:
Insults may not add to the discussion, but they speak volumes about the poster.
The time stamp on Brian Abraham's last post is 02:05 (EST?) so I'd guess he burnt the midnight oil to prove his credentials on the subject.
Maybe he's playing with someone else now...........
Are there any spare chairs left?
Have a nice night playing with yourself Brian
The time stamp on Brian Abraham's last post is 02:05 (EST?) so I'd guess he burnt the midnight oil to prove his credentials on the subject.
Maybe he's playing with someone else now...........
Are there any spare chairs left?
Join Date: May 2007
Location: Aus, or USA, or UK or EU, or possibly somehwere in Asia.
Posts: 320
Likes: 0
Received 0 Likes
on
0 Posts
Ha HA HA
Haven't enjoyed myself so much reading the rantings of a partially informed nong for a while.
Brian, I agree with the vast majority of what you state as it is extremely well informed. I caution readers to take Pelican with a little balance of engine manufacturer's advice as what he says is always thought provoking and generally spot on, but is well biased toward Conti's. In any case it is essential reading for interested pilots.
RS, you dill. you are living proof that a little knowledge is a dangerous thing. for fcuks sake LISTEN to what is being said, you have been demonstrating a remarkable lack of tolerance to those to whom you should be learning from, not trying to teach.
To the 'don't believe the flight manual' crew: The AFM is still the overarching document that (generally) supplies the information and procedures that you need to know and in any case should be the first reference. Look in there then ask questions on this forum, at least you will have some idea as to what the starting question should be. the subject is about a Cessna 172, not an Auster, which bareley qualifies as an aircraft, certainly not a certified one, and certainly does not have a proper flight manual. it is a curiosity, like many antique/special interest aircraft has a very basic guidance document. iterestingly, despite it's age the tenet that good quality motor spitit will work ok still holds true despite the difficulty of obtaining it. What worked back then will still work now. Cessnas, Warriors, Cirrii (plural of Cirrussess??) Grobs, Diamonds etc. in fact most common training and private aircraft.. all have up to date and informative manuals, even though they are more strongly influenced by the legal and certification influences than is best for the operator in my opinion. Before you advocate ignoring the AFM?POH, you should at least READ it.
Still, all a bit of fun really, can't wait to be told by RS that I aslo am a know nothing 35 year industry professional, and not an avid student like himself, ( Auto Rich, ha ha I especially liked that bit of near-knowledge)
HD
HD
Haven't enjoyed myself so much reading the rantings of a partially informed nong for a while.
Brian, I agree with the vast majority of what you state as it is extremely well informed. I caution readers to take Pelican with a little balance of engine manufacturer's advice as what he says is always thought provoking and generally spot on, but is well biased toward Conti's. In any case it is essential reading for interested pilots.
RS, you dill. you are living proof that a little knowledge is a dangerous thing. for fcuks sake LISTEN to what is being said, you have been demonstrating a remarkable lack of tolerance to those to whom you should be learning from, not trying to teach.
To the 'don't believe the flight manual' crew: The AFM is still the overarching document that (generally) supplies the information and procedures that you need to know and in any case should be the first reference. Look in there then ask questions on this forum, at least you will have some idea as to what the starting question should be. the subject is about a Cessna 172, not an Auster, which bareley qualifies as an aircraft, certainly not a certified one, and certainly does not have a proper flight manual. it is a curiosity, like many antique/special interest aircraft has a very basic guidance document. iterestingly, despite it's age the tenet that good quality motor spitit will work ok still holds true despite the difficulty of obtaining it. What worked back then will still work now. Cessnas, Warriors, Cirrii (plural of Cirrussess??) Grobs, Diamonds etc. in fact most common training and private aircraft.. all have up to date and informative manuals, even though they are more strongly influenced by the legal and certification influences than is best for the operator in my opinion. Before you advocate ignoring the AFM?POH, you should at least READ it.
Still, all a bit of fun really, can't wait to be told by RS that I aslo am a know nothing 35 year industry professional, and not an avid student like himself, ( Auto Rich, ha ha I especially liked that bit of near-knowledge)
HD
HD
Join Date: Jun 2004
Location: ENZED
Posts: 125
Likes: 0
Received 0 Likes
on
0 Posts
When climbing at higher altitudes , dont forget the density of the air decreases also.
To climb a 172 at 6000 ft or higher at full rich mixture is inviting the noise up the front to go quiet.
To achieve the chemically correct mixture required, the mixture will need careful and constant adjustment as you climb.
I have done meatbombing in 172, 182, 185 and 206, and on several occasions a jumper sitting on the floor has leaned back into the dash, and his chute pack has pushed the mixture control in.........instant result, engine stopped!
This has happened at 9,000 and 12,000 ft (206 and 185) in the last decade.
Restart accomplished, but not with full rich mixture..........
Some drop aircraft have a bracket fitted in front of the mixture control, to prevent this happening..................
To feed full fuel flow into an engine at high altitude is asking for trouble.
Leaning is a function not well taught or even understood at some flight training organisations. I recently conducted some Commercial cross country training for a 300 hr PPL, who had never been taught to lean, and didnt know how!
On the other hand, beware the lean all the time brigade, in their attempts to save fuel, engines get operated too lean and hot.
Parachute operations are good for teaching leaning and engine handling
techniques, always remember the 'rate of change' to an engines operating temperature, is just as important as leaning.
It is important that instructors themselves know this subject and how to teach it, but it seems an awful lot dont.!
Cheers
To climb a 172 at 6000 ft or higher at full rich mixture is inviting the noise up the front to go quiet.
To achieve the chemically correct mixture required, the mixture will need careful and constant adjustment as you climb.
I have done meatbombing in 172, 182, 185 and 206, and on several occasions a jumper sitting on the floor has leaned back into the dash, and his chute pack has pushed the mixture control in.........instant result, engine stopped!
This has happened at 9,000 and 12,000 ft (206 and 185) in the last decade.
Restart accomplished, but not with full rich mixture..........
Some drop aircraft have a bracket fitted in front of the mixture control, to prevent this happening..................
To feed full fuel flow into an engine at high altitude is asking for trouble.
Leaning is a function not well taught or even understood at some flight training organisations. I recently conducted some Commercial cross country training for a 300 hr PPL, who had never been taught to lean, and didnt know how!
On the other hand, beware the lean all the time brigade, in their attempts to save fuel, engines get operated too lean and hot.
Parachute operations are good for teaching leaning and engine handling
techniques, always remember the 'rate of change' to an engines operating temperature, is just as important as leaning.
It is important that instructors themselves know this subject and how to teach it, but it seems an awful lot dont.!
Cheers