Mixture leaning question.
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
Harley
Sorry my old fruit, I'm going to have to take you to task on that one.
If your comments were a "wind-up" you'll be pleased to know it worked!
The Auster was the backbone of the charter fleet in Australia up to the early sixties when US$'s became easier to get and machines like the early Cessnas , Piechasers and Comanches took over.
The reason why the flight manual was brief was because at that time pilots were expected to KNOW the details of how to operate an aircraft and paragraphs on how to open the door and get it in seemed superfluous.
It was only when the Americans started making aircraft for the great unwashed that instructions on which part of the sky had to be kept in the windshield became necessary.
As Brian so eloquently pointed out, KNOWING the systems allows the POH to be interpreted correctly.
As for the suitability of "good quality motor spirit"...No, it is no longer correct, because what was GQMS then may not be now. The term is undefined in almost any technical context you care to name.
At least the qualities and requirements for Avgas ARE well defined.
Why don't you get a "real motorcycle" instead of a curio like a Harley
the subject is about a Cessna 172, not an Auster, which bareley qualifies as an aircraft, certainly not a certified one, and certainly does not have a proper flight manual. it is a curiosity, like many antique/special interest aircraft has a very basic guidance document.
If your comments were a "wind-up" you'll be pleased to know it worked!
The Auster was the backbone of the charter fleet in Australia up to the early sixties when US$'s became easier to get and machines like the early Cessnas , Piechasers and Comanches took over.
The reason why the flight manual was brief was because at that time pilots were expected to KNOW the details of how to operate an aircraft and paragraphs on how to open the door and get it in seemed superfluous.
It was only when the Americans started making aircraft for the great unwashed that instructions on which part of the sky had to be kept in the windshield became necessary.
As Brian so eloquently pointed out, KNOWING the systems allows the POH to be interpreted correctly.
As for the suitability of "good quality motor spirit"...No, it is no longer correct, because what was GQMS then may not be now. The term is undefined in almost any technical context you care to name.
At least the qualities and requirements for Avgas ARE well defined.
Why don't you get a "real motorcycle" instead of a curio like a Harley
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
ZEEBEE
Wind up worked, offence not intended.
I agree with you that the only reason that Austers were used is that at that time people couldn't afford proper aeroplanes, or 'airplanes' as the vendors called them
However, This thread was about a theoretical situatuion in a 172 regarding mixture enrichment. you started the whole auster and motor spirit thing. I have done my time behind and between gipsys and cirrussess (cirrii??) and now enjoy reliable and comfortable alternatives, with proper Flight Manuals.
I could not care what your opinion of motorcycles is based on but mine is on 40 years riding and 75 motorcycles, including several of Great Britains finest "classics", or as we call them, 'unreliable dungers'.
I make my own decisions, but do however take the time to listen to others, like yourself, who on occaisions fail to reciprocate (like my old BSA).
With relation to the acual thread:
- I still stand by my references to reading the AFM/POH as a starting point.
- Pelicans Perch is good guidance but not always gospel, but always good reading.
- Some lycoming ARE fuel/oil/air cooled, especially in the climb phase, though the O320 is not critical in this case by any means.
Good Quality Motor Spirit, by its very broad definition , is still available as it is needed for Good Quality Motor Cars to function, or was the Morris Oxford the peak of automotive excellence? (likley yes in your opinion).
Objectively yes the definition my be different but subjectively no, otherwise all those old pommy cars would have long since died from fuel specific related issues rather than just by being poorly designed, built and supported, rattling to bits and collapsing in an oil drenched heap. ( they always had good heaters though). At least all that oil meant that they didn't dissolve into a pile of rust like italian cars did. (oh no, I have offended all those Lancia owners out there!!)
Kind Regards,
HD
Wind up worked, offence not intended.
I agree with you that the only reason that Austers were used is that at that time people couldn't afford proper aeroplanes, or 'airplanes' as the vendors called them
However, This thread was about a theoretical situatuion in a 172 regarding mixture enrichment. you started the whole auster and motor spirit thing. I have done my time behind and between gipsys and cirrussess (cirrii??) and now enjoy reliable and comfortable alternatives, with proper Flight Manuals.
I could not care what your opinion of motorcycles is based on but mine is on 40 years riding and 75 motorcycles, including several of Great Britains finest "classics", or as we call them, 'unreliable dungers'.
I make my own decisions, but do however take the time to listen to others, like yourself, who on occaisions fail to reciprocate (like my old BSA).
With relation to the acual thread:
- I still stand by my references to reading the AFM/POH as a starting point.
- Pelicans Perch is good guidance but not always gospel, but always good reading.
- Some lycoming ARE fuel/oil/air cooled, especially in the climb phase, though the O320 is not critical in this case by any means.
Good Quality Motor Spirit, by its very broad definition , is still available as it is needed for Good Quality Motor Cars to function, or was the Morris Oxford the peak of automotive excellence? (likley yes in your opinion).
Objectively yes the definition my be different but subjectively no, otherwise all those old pommy cars would have long since died from fuel specific related issues rather than just by being poorly designed, built and supported, rattling to bits and collapsing in an oil drenched heap. ( they always had good heaters though). At least all that oil meant that they didn't dissolve into a pile of rust like italian cars did. (oh no, I have offended all those Lancia owners out there!!)
Kind Regards,
HD
Last edited by HarleyD; 19th Aug 2009 at 03:26. Reason: speling and grandma
Join Date: Sep 2000
Location: Adelaide, South Australia
Posts: 394
Likes: 0
Received 0 Likes
on
0 Posts
LocoDriver wrote:
Probably in the late 70's there was a SE aircraft (piper?) that suffered fuel exhaustion and crash-landed in a Brisbane suburban street. There would have been more than enough fuel normally, but the pilot left the mixture FULL RICH for the entire flight. 
I gave away all my Crash Comics to Pinky the Pilot, so if he's lurking here he might be able to look it up and add some more detail.
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!
I gave away all my Crash Comics to Pinky the Pilot, so if he's lurking here he might be able to look it up and add some more detail.
Join Date: Jun 2001
Location: Australia
Posts: 889
Likes: 0
Received 0 Likes
on
0 Posts
Now that the insults from one individual have disappeared, I have a question. Perhaps Brian if you're still around you might be willing to answer.
The device I've heard called the "economiser" functions exactly as you said, enriching the mixture a specified amount at full throttle (not necessarily full power).
I'm also aware of a power enrichment valve, especially in carburettored cars, that opens a second, larger bore, fuel jet in the carburettor at high power settings to overcome the limited response that one can get from a single main fuel jet over a wide variety of power settings.
Question - are the two functions actually the same, just called by different names? Sorry if it's a silly question...
As to the bigger picture of old aircraft, new aircraft, and lack of leaning skills - from the point of view of safety, single power lever engines with modern low fuel warning systems can't come quickly enough. I have read (sorry don't have a reference) that not a single C172 has been lost due to fuel exhaustion since Cessna fitted the "L FUEL LOW R" annunciator to the R models and later.
Thanks,
O8
The device I've heard called the "economiser" functions exactly as you said, enriching the mixture a specified amount at full throttle (not necessarily full power).
I'm also aware of a power enrichment valve, especially in carburettored cars, that opens a second, larger bore, fuel jet in the carburettor at high power settings to overcome the limited response that one can get from a single main fuel jet over a wide variety of power settings.
Question - are the two functions actually the same, just called by different names? Sorry if it's a silly question...
As to the bigger picture of old aircraft, new aircraft, and lack of leaning skills - from the point of view of safety, single power lever engines with modern low fuel warning systems can't come quickly enough. I have read (sorry don't have a reference) that not a single C172 has been lost due to fuel exhaustion since Cessna fitted the "L FUEL LOW R" annunciator to the R models and later.
Thanks,
O8
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
Harley
No offense taken, but as a dedicated stirrer, you really can't help yourself can you ?
The only reason for a flight manual is to outline the occasions where the specific requirements of an aircraft deviate from the accepted norm.
Putting paragraphs in there stating "For take-off, line the aircraft along the runway and open the throttle" are totally (or should be) superfluous and do nothing but increase the bulk of the POH and make it all the more difficult to find the things that REALLY matter.
Have you seen some of the POH's lateley ? No wonder manufacturers keep uprating their engines...it's so they can carry the POH!!!
My ONLY reason for citing the Auster and its poh is simply to point out that a generalised statement such as RTFM has to taken with care.
Great as a starting point but they cannot cover all possibilities and it behooves the driver to know the systems and apply that knowledge where the POH is deficient or even wrong.
I can cite examples on modern aircraft such as the Navajo where the POH is misleading, but that's not what this thread's about.
I think we agree on the fundamentals (even about BSAs and Morris Oxfords ( but that's another subject)
No offense taken, but as a dedicated stirrer, you really can't help yourself can you ?
The only reason for a flight manual is to outline the occasions where the specific requirements of an aircraft deviate from the accepted norm.
Putting paragraphs in there stating "For take-off, line the aircraft along the runway and open the throttle" are totally (or should be) superfluous and do nothing but increase the bulk of the POH and make it all the more difficult to find the things that REALLY matter.
Have you seen some of the POH's lateley ? No wonder manufacturers keep uprating their engines...it's so they can carry the POH!!!
My ONLY reason for citing the Auster and its poh is simply to point out that a generalised statement such as RTFM has to taken with care.
Great as a starting point but they cannot cover all possibilities and it behooves the driver to know the systems and apply that knowledge where the POH is deficient or even wrong.
I can cite examples on modern aircraft such as the Navajo where the POH is misleading, but that's not what this thread's about.
I think we agree on the fundamentals (even about BSAs and Morris Oxfords ( but that's another subject)
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
No Worries ZEEBEE, a bit of fun and should be taken as such.
I have been involved in the writing of two Flight Manuals now and can assure you that any GAMA format manual contains a world of information, specifications, limitations, procedures and other useful stuff included by the manufacturer, as they know best, within the constraints of the certification engineers, the certificating authority, and the army of legal nit pickers (read more certification engineers) who seem bent on preventing actual information that may be useful to the pilot from inclusion. HMMM yes I see your point.
I have on numerous occaisions flown with pilots who have declined to follow (approved) Flight Manual procedures and as a consequence are failing to operate the aircraft in the most efficient and safe manner. this is normally due to a CP who has his own ideas that he (or she) believes are better than those proven by hundreds of hours of flight test. what can I say, this Tribal Knowledge is then perpetuated until properly trained persons can provide proper training.
This exact issue is one that has been referenced earlier regarding poorly (though adequately according to CASA) trained instructors who then go on to provide a minimal standard of training to their luckless victims, sorry students.
Any Grade III's out there reading this, please do not be personally offended, except for those Rover drivers amongst you, you are yourselves victims of the great flight instructor swindle, I know you try hard, but you can only ever be as good as your teachers and sadly these are not the highly experienced senior grade 1's and career CFI's that we used to enjoy the priviledge of learning from.
Good training is expensive, but every one wants the cut price product these days. competition has not been good for the industry, it has hollowed it away from within. Instructing is merely a rung on the boarding ladder of the big carriers. A proper licence should cost about 2 1/2 times what it costs now and include aero's, spinning and a good 'up to the elbows' serve of getting your hands dirty and learning the real stuff that would mean that threads like this would be redundant.
Older guys here may have learned some of that sort of stuff hotting up old vauxhalls or rebuilding their BSA bantam every few weeks. Not much of that goes on these days, just boot up the PC and go simming like soooo many of the wannabe's here.
Rambling on a bit there, but I do feel strangely better now.
HD
I have been involved in the writing of two Flight Manuals now and can assure you that any GAMA format manual contains a world of information, specifications, limitations, procedures and other useful stuff included by the manufacturer, as they know best, within the constraints of the certification engineers, the certificating authority, and the army of legal nit pickers (read more certification engineers) who seem bent on preventing actual information that may be useful to the pilot from inclusion. HMMM yes I see your point.
I have on numerous occaisions flown with pilots who have declined to follow (approved) Flight Manual procedures and as a consequence are failing to operate the aircraft in the most efficient and safe manner. this is normally due to a CP who has his own ideas that he (or she) believes are better than those proven by hundreds of hours of flight test. what can I say, this Tribal Knowledge is then perpetuated until properly trained persons can provide proper training.
This exact issue is one that has been referenced earlier regarding poorly (though adequately according to CASA) trained instructors who then go on to provide a minimal standard of training to their luckless victims, sorry students.
Any Grade III's out there reading this, please do not be personally offended, except for those Rover drivers amongst you, you are yourselves victims of the great flight instructor swindle, I know you try hard, but you can only ever be as good as your teachers and sadly these are not the highly experienced senior grade 1's and career CFI's that we used to enjoy the priviledge of learning from.
Good training is expensive, but every one wants the cut price product these days. competition has not been good for the industry, it has hollowed it away from within. Instructing is merely a rung on the boarding ladder of the big carriers. A proper licence should cost about 2 1/2 times what it costs now and include aero's, spinning and a good 'up to the elbows' serve of getting your hands dirty and learning the real stuff that would mean that threads like this would be redundant.
Older guys here may have learned some of that sort of stuff hotting up old vauxhalls or rebuilding their BSA bantam every few weeks. Not much of that goes on these days, just boot up the PC and go simming like soooo many of the wannabe's here.
Rambling on a bit there, but I do feel strangely better now.
HD
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
Harley,
Glad you feel better...
you wrote
Ain't that the truth.
How many pilots still insist on operating CSU equipped engines an inch or more undersquare as a religion, completely oblivious to the fact that the circumstances (and the POH) may favour the opposite?
Glad you feel better...
you wrote
I have on numerous occaisions flown with pilots who have declined to follow (approved) Flight Manual procedures and as a consequence are failing to operate the aircraft in the most efficient and safe manner. this is normally due to a CP who has his own ideas that he (or she) believes are better than those proven by hundreds of hours of flight test. what can I say, this Tribal Knowledge is then perpetuated until properly trained persons can provide proper training.
How many pilots still insist on operating CSU equipped engines an inch or more undersquare as a religion, completely oblivious to the fact that the circumstances (and the POH) may favour the opposite?
Join Date: Mar 2008
Location: Australia
Posts: 149
Likes: 0
Received 0 Likes
on
0 Posts
Totally agree Zeebee,
This has been very interesting.
Judging by a few comments, it seems some would not lean the mixture at a high elevation airport to obtain max power.
And to the comment about under square over square, again totally agree, some of the info regurgitated out of some is utter tripe.
This has been very interesting.
Judging by a few comments, it seems some would not lean the mixture at a high elevation airport to obtain max power.
And to the comment about under square over square, again totally agree, some of the info regurgitated out of some is utter tripe.
And to the comment about under square over square, again totally agree, some of the info regurgitated out of some is utter tripe.
Join Date: Aug 2003
Location: Perth
Posts: 430
Likes: 0
Received 0 Likes
on
0 Posts
Judging by a few comments, it seems some would not lean the mixture at a high elevation airport to obtain max power.
A "full rich" take-off at high altitude airports is throwing away performance just when it's needed the most.
Most POH's are quite explicit in the correct use of mixture in these circumstances even though it should be taught as a general procedure.
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
Just so that readers don't think I'm some expert on the subject under discussion. I grew up in Whyalla and the "Whyalla Airlines" accident, with all the talk surrounding the event about leaning practices, led me to delve into the subject. On top of everything I knew some of the families who lost loved ones, and also had a loooong association with the patriarch of the family who ran the airline. My personal experience has mainly been with turbines, and the piston engine with which I had the most experience was fitted with a pressure injection type carburetor, which automatically maintained the mixture selected regardless of changes in OAT or altitude. The mixture had three positions only, idle cut off, normal and rich. Rich was used for all ground operations, take off, landing, climb and descent, normal was used for all other normal flight conditions. So not a lot of hands on experience.
No silly questions, only silly answers. Yes, both the same Oktas8.
Is a feature of float carburetors, so yes if so fitted.
And anything from Harley you can take to the bank.
are the two functions actually the same, just called by different names? Sorry if it's a silly question...
Does this enrichment function apply to CSU equipped aeroplanes as well?
And anything from Harley you can take to the bank.
Join Date: Sep 2000
Location: Adelaide, South Australia
Posts: 394
Likes: 0
Received 0 Likes
on
0 Posts
Zoomy wrote:
Most pilots here in AU would not experience a high elevation field in their lifetime, so if and when you are there, leaning the mixture might be the last thing on your mind. For a lot of pilots around the Rocky Mountains USA, it would be second nature.
If you were departing from say, Albuquerque New Mexico (KABQ) which is 5,352' AGL you might be wondering why the aircraft is struggling to climb, or perhaps Leadville (aptly named) at 9,927' AGL where most normally aspirated aircraft would need a JATO to get airborne.
Judging by a few comments, it seems some would not lean the mixture at a high elevation airport to obtain max power.
If you were departing from say, Albuquerque New Mexico (KABQ) which is 5,352' AGL you might be wondering why the aircraft is struggling to climb, or perhaps Leadville (aptly named) at 9,927' AGL where most normally aspirated aircraft would need a JATO to get airborne.
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
I have operated from airports with elevations of 10,000 ft and, just as importantly ambient tepms that raise the DH to 12,500ft. the flight manual actually states that mixture leaning for take off is a consideration at high elevations, but I always work from rich to lean, and in any case the engine manufacturers recommendation is that leaning for take off at high elevations should be followed 'to prevent rough running from overly rich mixture', again more important with some egines more than others.
lycoming injected engines are scheduled rich and will almost certainly require leaning for better power, though i never did experience the 'rough running' at full rich as described. monitior the egt and lean with a good rich side margin, aggressive leaning not required, and you will be sweet, however some TC engines are mandated full rich at high (climb) power settings, regardless of altitude (FTH 12-14,000ft) due to the absolute requirement of fuel for egine cooling within limits, remember that engine cooling capacity of air decreases with altitude even though a TC engine can produce 100% power up to FTH. EGT(TIT) can be well in limits but CHT becoms the critical factor. the top part of the green arc (but below red line) is definately the optimal range to operate in any a regular basis. High CHT will reduce engine life as a matter of course.
Oversquare is very good for your engine generally, better oil consumption, and ring sealing higher BMEP aids efficiency and its quieter. if it was bad there would be no TC or SC engines. a merlin will take 62"MAP in MIL, though the boaties were getting up to 120"MAP (though not for full TBO)
HJD
lycoming injected engines are scheduled rich and will almost certainly require leaning for better power, though i never did experience the 'rough running' at full rich as described. monitior the egt and lean with a good rich side margin, aggressive leaning not required, and you will be sweet, however some TC engines are mandated full rich at high (climb) power settings, regardless of altitude (FTH 12-14,000ft) due to the absolute requirement of fuel for egine cooling within limits, remember that engine cooling capacity of air decreases with altitude even though a TC engine can produce 100% power up to FTH. EGT(TIT) can be well in limits but CHT becoms the critical factor. the top part of the green arc (but below red line) is definately the optimal range to operate in any a regular basis. High CHT will reduce engine life as a matter of course.
Oversquare is very good for your engine generally, better oil consumption, and ring sealing higher BMEP aids efficiency and its quieter. if it was bad there would be no TC or SC engines. a merlin will take 62"MAP in MIL, though the boaties were getting up to 120"MAP (though not for full TBO)
HJD
