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Mixture Controls On Propeller-driven Aircraft  
User currently offlineWestJetForLife From Canada, joined Jun 2005, 814 posts, RR: 1
Posted (6 years 1 month 3 weeks 6 days 8 hours ago) and read 17131 times:

Hi, everyone in Tech-Land. Nik here with yet another question to ask.

When I was in Air Cadets, I was taken up numerous times in a Cessna 172, and even on one occasion flew on a Beech B58 Baron as part of my aviation training through the RCAC (Royal Canadian Air Cadets).

This question has been bugging me for four years, and I haven't found any answers yet, but how do the fuel mixture controls on a propeller-driven airplane work, exactly? I understand lean and rich, but everything else is Greek to me.

To refine the question: when we were up at high altitude (9,000 to 11,000 feet), the Pilot-in-Command pulled the mixture lever(s) back about halfway between 1/4 and 1/2 between lean and rich settings. Why do propeller pilots do this? Does it have something to do with engine control? Fuel mixture in the cylinders? Fuel economy? An explanation would be greatly appreciated.

Thank you,
Nik


I need a drink.
80 replies: All unread, showing first 25:
 
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 1, posted (6 years 1 month 3 weeks 6 days 7 hours ago) and read 17187 times:
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HEAD DATABASE EDITOR



Quoting WestJetForLife (Thread starter):
when we were up at high altitude (9,000 to 11,000 feet), the Pilot-in-Command pulled the mixture lever(s) back about halfway between 1/4 and 1/2 between lean and rich settings. Why do propeller pilots do this?

It's called "leaning" the fuel mixture, and it's done to maintain an acceptable fuel/air ratio for the engine.

At sea level, a fully-rich mixture setting will probably produce a perfectly acceptable ratio of fuel to air. That mixture will contain just the right amount of fuel and just the right amount of air to burn efficiently.

Now, as we climb higher, the air becomes thinner. If the mixture setting remains constant, the engine will receive the same amount of fuel, but much less air. Because there's so much more fuel compared to air, this mixture will not burn efficiently.

So, as we climb, and as the air becomes thinner, we "lean" the mixture (or reduce the amount of fuel being introduced to the engine) so that the ratio of fuel decreases accordingly. This maintains the optimum fuel to air ratio, and the engine keeps running smoothly.

2H4



Intentionally Left Blank
User currently offlineMender From United Kingdom, joined Feb 2004, 237 posts, RR: 0
Reply 2, posted (6 years 1 month 3 weeks 6 days 7 hours ago) and read 17157 times:

It is to allow the pilot to compensate the engine fuel mixture for the aircraft altitude.

As the aircraft climbs and the air becomes thinner the air/fuel ratio or mixture in the engine will become rich as there is less air available to burn the fuel with. By using this control the pilot can manually correct the fuel/air ratio. More often than not the aircraft will have an instrument that displays the EGT or exhaust gas temperature. By watching the EGT gauge when the pilot is adjusting the mixture he can tell when it is "about right".


User currently offlineWestJetForLife From Canada, joined Jun 2005, 814 posts, RR: 1
Reply 3, posted (6 years 1 month 3 weeks 6 days 7 hours ago) and read 17144 times:



Quoting Mender (Reply 2):
More often than not the aircraft will have an instrument that displays the EGT or exhaust gas temperature. By watching the EGT gauge when the pilot is adjusting the mixture he can tell when it is "about right".

What exactly would be the "about right" EGT for flying a prop-driven plane at, say, 10,000 feet MSL?

Another question: do turboprop aircraft (Ex. Dash 8, Dornier DO-328, ATR-42/72) use fuel mixture to enrich/lean their engines, or do these aircraft have computerized mixture controls?

Thanks,
Nik



I need a drink.
User currently offlineN353SK From United States of America, joined Jun 2006, 792 posts, RR: 0
Reply 4, posted (6 years 1 month 3 weeks 6 days 6 hours ago) and read 17108 times:



Quoting WestJetForLife (Reply 3):
What exactly would be the "about right" EGT for flying a prop-driven plane at, say, 10,000 feet MSL?

I'm not exactly sure, but one common technique is to set your cruise power to slightly below what the POH calls for with mixture full rich and then lean it out until the RPMs peak.


User currently offlineVC10 From United Kingdom, joined Nov 2001, 1397 posts, RR: 16
Reply 5, posted (6 years 1 month 3 weeks 6 days 6 hours ago) and read 17104 times:

Now I am no expert on light aeroplane piston engines, but I have had some experience on the larger 18 cylinder variety

Now as I understand it he mixture control on a piston engine sets the mixture ratio desired by the pilot for the engine power he is about to use. Also piston engines have a bad habit of detonating if they get too hot and detonation is definately a condition to avoid. When engines are operated at high powers take-off and climb they tend to get hot and so are more likely to detonate.

There is a specific air /fuel ratio which will give you the engine's best power, however the engine gets very hot [detonation] so the mixture is run at rich so there is excess fuel which can be used to cool the cylinders

As you climb the barometric control will keep the air/fuel mixture at this rich setting or indeed any other setting selected on the mixture lever

Once settled in cruise[ and using lower power] because the power curve drops off either side of best power mixture you can now safely lean the mixture to the lean side of best power with no loss of power compared to that on the rich side of best power mixture.

There are all sorts of arguments about how far you should lean or not lean , but that is another question.

I really just wanted to say that the mixture lever is not there to correct for the engine moving to a rich mixture as it climbs as this should be done by the barometric fuel control capsule

The mixture lever is there to allow the pilot to adjust the mixture ratio to suit the phase of flight and power being used

As I said I am no expert on small engines s if they do not have automatic altitude correction capsules I am quite wiling to be corrected

littlevc10


User currently offlineTb727 From United States of America, joined Jun 2005, 1549 posts, RR: 8
Reply 6, posted (6 years 1 month 3 weeks 6 days 4 hours ago) and read 17069 times:



Quoting WestJetForLife (Reply 3):

Another question: do turboprop aircraft (Ex. Dash 8, Dornier DO-328, ATR-42/72) use fuel mixture to enrich/lean their engines, or do these aircraft have computerized mixture controls?

Nope. The only aircraft that need mixture control are normal aspirated aircraft. On advanced airplanes like jets, you have a fuel control unit that automatically changes fuel density for changes in altitude. I have limited Turboprop time but they basically work the same. I don't have much prop time at all, jets are so much easier, in thrust we trust!



Too lazy to work, too scared to steal!
User currently offlineVC10 From United Kingdom, joined Nov 2001, 1397 posts, RR: 16
Reply 7, posted (6 years 1 month 3 weeks 6 days 4 hours ago) and read 17060 times:

Quoting Tb727 (Reply 6):
On advanced airplanes like jets, you have a fuel control unit that automatically changes fuel density for changes in altitude.

You also have this on piston engines, well at least on the big radials , where the fuel flow is altered automatically with changes in altitude to maintain the selected fuel/ air ratio. The mixture lever selects what that fuel/air ratio will be

littlevc10

[Edited 2008-02-24 14:28:06]

User currently offlineMender From United Kingdom, joined Feb 2004, 237 posts, RR: 0
Reply 8, posted (6 years 1 month 3 weeks 6 days 4 hours ago) and read 17048 times:



Quoting WestJetForLife (Reply 3):
What exactly would be the "about right" EGT for flying a prop-driven plane at, say, 10,000 feet MSL?

Hopefully a pilot will answer this properly, it's nearly 20 years since I worked on piston aircraft but if I recall correctly the pilot leans the mixture until the EGT peaks and then richens it up slightly.

I'm the first to admit that I don't remember too much about the carburetor used on aircraft like the 172 or the Cherokee but I'm sure that it doesn't have any barometric correction, just the mixture control. This is partly because the aircraft is cheap/basic and also partly because they are mainly used at low altitudes. Remember the aircraft are unpressurized.

It wouldn't surprise me that you would have barometric correction on an 18 cylinder engine because the airframe is also likely to be pressurized AND it would have a variable pitch prop.

Once you have a variable pitch prop piston engine control gets more complicated because you have to monitor the torque on the engine. This is usually done by monitoring intake manifold vacuum. Basically the pilot will have to juggle the throttle, propeller pitch and mixture and adjust these at each phase of the flight such as climb, cruise and descent. I think the pilot sets the speed with the prop pitch, then the vacuum with the throttle, then adjusts the mixture.

Quoting VC10 (Reply 5):
Now as I understand it he mixture control on a piston engine sets the mixture ratio desired by the pilot for the engine power he is about to use. Also piston engines have a bad habit of detonating if they get too hot and detonation is definately a condition to avoid. When engines are operated at high powers take-off and climb they tend to get hot and so are more likely to detonate.

The pilot always sets the mixture to fully rich for take off and landing so detonation shouldn't be an issue.


User currently offlineDKCFII From United States of America, joined Feb 2007, 22 posts, RR: 0
Reply 9, posted (6 years 1 month 3 weeks 6 days 4 hours ago) and read 17046 times:

On the C-172 the pilot leans the mixture out until the RPM reaches a peak. At this point you note the EGT and the richen the mixture until the EGT is 50deg rich of peak. This gives you the "Best Power" mixture. If you want "Best Economy" then you leave the mixture at the max EGT. Also some planes don't have an EGT and in that case you just note the max RPM and then turn the mixture in (Richen) about one full turn. Each plane has it's own best economy and best power EGT, so always consult the POH for your airplane.

Quoting Mender (Reply 8):
The pilot always sets the mixture to fully rich for take off and landing so detonation shouldn't be an issue.

The mixture also isn't always set at rich for takeoff.....Where I fly out near Denver, CO we have to lean the mixture before takeoff since the field elev. is 5670msl.

-Dan K


User currently offlineWestJetForLife From Canada, joined Jun 2005, 814 posts, RR: 1
Reply 10, posted (6 years 1 month 3 weeks 6 days 2 hours ago) and read 17019 times:

Once again, Tech/ops never ceases to amaze me.

Thanks, everyone, for their responses. You all have answered my question in full.

Nik

[Edited 2008-02-24 16:47:59]


I need a drink.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6265 posts, RR: 3
Reply 11, posted (6 years 1 month 3 weeks 5 days 20 hours ago) and read 16955 times:



Quoting 2H4 (Reply 1):
At sea level, a fully-rich mixture setting will probably produce a perfectly acceptable ratio of fuel to air. That mixture will contain just the right amount of fuel and just the right amount of air to burn efficiently.

Not really, but the manufacturers would like us to leave the mixture knob at full rich, because climbing out with the mixture full rich provides some margin against detonation and helps cool the engine. If you do a run-up leaning (take the engine up to 1,800 RPM and lean until you find peak, and then push the mixture rich for 3 notches), you will find that the engine, even when close to sea level, is still running pretty rich. You can use the above 3000 foot takeoff procedure in the POH at lower-elevation airports, but if you do, be particularly mindful of your CHT reading on climbout.

However, the manufacturers like you to climb out this way, because many have found that, starting at fields below 3,000 feet of elevation, the engine makes so much power that the primary consideration on climbout is proper cylinder cooling. It is possible that if you are careles with your airspeed on climbout at a low elevation airfield, you could cause the CHT's (Cylinder Head Temperatures) to rise above acceptable limits. Too rich of a mixture definitely helps keep cylinder head temps under control. Read John Deakin's articles from avweb.com from around the 2005-2006 timeframe...  Wink



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineAnalog From United States of America, joined Jul 2006, 1900 posts, RR: 1
Reply 12, posted (6 years 1 month 3 weeks 5 days 19 hours ago) and read 16943 times:

Manual mixture controls are an artifact of overbearing regulation and a stagnant industry. The designs used in piston aircraft engines are just amazingly primitive.

Quoting Tb727 (Reply 6):
Nope. The only aircraft that need mixture control are normal aspirated aircraft

Eh? Superchargers don't obviate the need for mixture control.


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1639 posts, RR: 1
Reply 13, posted (6 years 1 month 3 weeks 5 days 16 hours ago) and read 16931 times:



Quoting Tb727 (Reply 6):
The only aircraft that need mixture control are normal aspirated aircraft.

Proof, once again, that you'd better damn well take what you read on these boards with a huge grain of salt. There is some simply ignorant advice but there is, also, some information that is so far wrong as to be lethal.

I have, from long ago, about 600 hours of T210 time; should I have put duct tape over the mixture control?

Beware, especially, the MSFS "pilots" who seem to know everything about FADEC but couldn't land their fork on their plate.


User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2254 posts, RR: 16
Reply 14, posted (6 years 1 month 3 weeks 5 days 11 hours ago) and read 16902 times:



Quoting VC10 (Reply 7):
You also have this on piston engines, well at least on the big radials , where the fuel flow is altered automatically with changes in altitude to maintain the selected fuel/ air ratio. The mixture lever selects what that fuel/air ratio will be

Never flew a R4360 or even an R2800 but did fly a P&W R985 for a few years and yes you did lean out the mixture as you climbed.


User currently offlineTb727 From United States of America, joined Jun 2005, 1549 posts, RR: 8
Reply 15, posted (6 years 1 month 3 weeks 5 days 11 hours ago) and read 16896 times:

Quoting ThirtyEcho (Reply 13):

Proof, once again, that you'd better damn well take what you read on these boards with a huge grain of salt. There is some simply ignorant advice but there is, also, some information that is so far wrong as to be lethal.

Really?

[Edited 2008-02-25 08:00:47]


Too lazy to work, too scared to steal!
User currently offlineDKCFII From United States of America, joined Feb 2007, 22 posts, RR: 0
Reply 16, posted (6 years 1 month 3 weeks 5 days 10 hours ago) and read 16887 times:

Sometimes I wonder....  banghead 

User currently offlineDragon6172 From United States of America, joined Jul 2007, 1199 posts, RR: 0
Reply 17, posted (6 years 1 month 3 weeks 5 days 9 hours ago) and read 16868 times:



Quoting ThirtyEcho (Reply 13):
couldn't land their fork on their plate.

Now thats good humor!! Big grin



Phrogs Phorever
User currently offlineAnalog From United States of America, joined Jul 2006, 1900 posts, RR: 1
Reply 18, posted (6 years 1 month 3 weeks 5 days 9 hours ago) and read 16866 times:



Quoting CosmicCruiser (Reply 14):
lean out the mixture as you climbed.

Is that really leaning out the mixture, or does that have the effect of maintaining the A/F ratio by compensating for the lower pressure?


User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 19, posted (6 years 1 month 3 weeks 5 days 7 hours ago) and read 16846 times:

Proper leaning of an aircraft piston engine is a very complicated subject. First, on takeoff where power output is maximized and airflow is low no air cooled aircraft piston engine gets adequate cooling airflow to keep cylinder head temperatures at acceptable limits, and so the fuel system is calibrated to give an overrich mixture, effectively cooling the cylinder with raw gas. This is very inefficient, but it works and doesn't impose a weight penalty (except for the excess fuel used.) This is one of the primary reasons for having a manual mixture control; you obviously do not want to use this "overrich" mixture except where you absolutely have to, as in addition to the excessive fuel consumption it causes spark plug fouling (especially with leaded fuel), oil dilution and contamination, and other undesirable effects. Under 75% power output on Lycomings and 65% output on Continentals you are free (according to the manufacturers) to lean to your heart's content. Most lean to approximately best power, which is when you lean to peak EGT and then enrich 50 degrees (when using the guage) or approximate by leaning to the onset of roughness and then enrich slightly. Much more efficient (when your engine can do it) is to lean "lean of peak"; the big radials did this routinely but most stock flat opposed engines do not have uniform enough fuel distribution to do this effectively. But with "Gamijectors" and newer engines (Continentals anyway; I don't know if Lycoming is doing it as well) the flows are better balanced and it is becoming possible. Lean of peak operation sacrifices some power output for much greater efficiency and significantly lower cylinder head temps. This has been frowned on in the past because of the uneven fuel distribution problem; the most dangerous point for a piston engine is actually just slightly rich of peak EGT; that is where CHT maximizes, and if you do not have good distribution you could have one cylinder there when the others are considerably leaner. But with better fuel distribution and much better instrumentation available it is becoming more and more acceptable.


The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 20, posted (6 years 1 month 3 weeks 5 days 7 hours ago) and read 16834 times:

Quoting ThirtyEcho (Reply 13):
Proof, once again, that you'd better damn well take what you read on these boards with a huge grain of salt. There is some simply ignorant advice but there is, also, some information that is so far wrong as to be lethal.

Somehow, I doubt any pilot is gonna print out an A.net thread and bring it along in the cockpit for procedure.

So rather than the usual breathless astonishment at everyone else's stupidity, how about offering up clarification to what is obviously a simple misunderstanding and/or misuse of terminology.

The OP asked if turboprops need manual mixture adjustments like recips do. I take it the answer is no.

However, a turbo/supercharged piston engine (which would NOT be naturally aspirated) needs manual mixture control the same as any other recip, yes?

[Edited 2008-02-25 11:28:49]


Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 21, posted (6 years 1 month 3 weeks 5 days 7 hours ago) and read 16825 times:



Quoting Speedracer1407 (Reply 20):
However, a turbo/supercharged piston engine (which would NOT be naturally aspirated) needs manual mixture control the same as any other recip, yes?

Correct.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineKELPkid From United States of America, joined Nov 2005, 6265 posts, RR: 3
Reply 22, posted (6 years 1 month 3 weeks 5 days 7 hours ago) and read 16826 times:



Quoting SEPilot (Reply 19):

Aaah, a man who's read John Deakin  Smile

However, I must pick a bone:

Quoting SEPilot (Reply 19):
First, on takeoff where power output is maximized and airflow is low no air cooled aircraft piston engine gets adequate cooling airflow to keep cylinder head temperatures at acceptable limits, and so the fuel system is calibrated to give an overrich mixture, effectively cooling the cylinder with raw gas.

Cessna recommends leaning before takeoff in many of their non-high performance birds (like the 152 and 172) at a field elevation above 3,000 feet. In fact, until I moved to the Pacific Northwest (having had learned to fly in a part of the desert southwest of the USA where you will never find a field elevation under 3,500 feet), I thought that this was standard operating procedure, until I went up for a rental checkout in a 172 here in PDX land, and the instructor asked what in the hell I was doing when, after runup, I took the engine up to 1800 RPM and started leaning...we had a thorough walkthrough of the 172 POH after that upon returning to the FBO  Wink

I'm guessing that above 3,000 feet, Cessna at least feels that the engine is no longer making high enough power that you could cook your cylinder heads by taking off with the mixture set for max. power.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 23, posted (6 years 1 month 3 weeks 5 days 7 hours ago) and read 16815 times:



Quoting KELPkid (Reply 22):

Cessna recommends leaning before takeoff in many of their non-high performance birds (like the 152 and 172) at a field elevation above 3,000 feet.

You are absolutely correct. However, the reason is that the full rich calibration is for sea level, and as altitude rises it becomes more rich and consequently power suffers even more, as well as the engine (unless it is turbocharged) is not capable of producing as much power due to the lower weight of air ingested by the engine. I did not address this issue in my previous post; but you are quite right.

Quoting KELPkid (Reply 22):
Aaah, a man who's read John Deakin

Yes, I have, as well as a number of others. John Deakin is the main source for running LOP information, however; he is very knowledgeable on the subject as well as being an excellent writer.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineKELPkid From United States of America, joined Nov 2005, 6265 posts, RR: 3
Reply 24, posted (6 years 1 month 3 weeks 5 days 6 hours ago) and read 16806 times:



Quoting SEPilot (Reply 23):

I'd add you to my RU list for that, but it seems to not be working at the moment...anyone from Demand Media had a look at this?



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
25 SEPilot : You have to go in and edit your profile; add any names you want to manually and they will appear on your and their profile. I had the same problem, b
26 JoeCanuck : Good discussion about something not easily understood by folks without experience with carbs. Basically, you lean or enrich the air/fuel mixture to ac
27 KELPkid : Done! Welcome to my RU list!
28 Analog : Could the variable geometry intakes seen in some turbojets/turbofans (eg. J58, Olympus) have this effect (akin to throttling)? These devices represen
29 Post contains images Bond007 : It's not uncommon of course, to forget to enrich the mixture again when descending... so I'm told ...it all goes quiet, except for the sounds of any
30 SEPilot : Current production turbocharged (there are no currently produced supercharged certified engines that I am aware of) use exactly the same mixture cont
31 SEPilot : Well, we can get into a semantic debate, but the aviation world speaks of it as leaning, which when you consider that it is adjusting the mixture to
32 Post contains images Analog : Well, you are leaning it versus the previous setting (on the knob, lever, misc. adjustment control), so in that sense you are leaning it, but you are
33 SEPilot : Actually, it is not regulations so much as economics. Continental has a full FADEC control system that they have been developing for years; it has be
34 KELPkid : I thought the Cirrus SR-20 and SR-22 were both using this...
35 Analog : Why can't they use automotive engine controls? Take some Bosch ECU (or from another manufacturer willing to license), fiddle with the constants, and
36 SEPilot : If it were that simple I'm sure Continental would have done it instead of developing a whole new system. I do not understand enough about the details
37 Post contains images Analog : I certainly don't understand the details, but I would be willing to assume that the main reason is either regulatory or one of liability (i.e. if we
38 JoeCanuck : The main reason fadec has such a tough time making into planes is product liability. Until very recently, light airplane engines were gasoline powered
39 SEPilot : This may be, but I still point to the fact that Aerosance Controls (owned by Continental) has been working for years developing a totally new FADEC s
40 Mir : I believe that the variable geometry intakes are designed to ensure that the engines get air to the compressor at the right pressure and speed (ideal
41 CosmicCruiser : Thanks for beating me to it SEPilot.....Heck I used to "LEAN" the old R-985 by looking out at the exhaust flame at night.
42 Post contains links N231YE : I used to wonder about FADEC in general aviation, so much so that I asked in this thread: Why Is Fadec Progressing So Slowly In GA? (by N231YE Oct 5
43 SEPilot : Operating lean of peak you actually do this. The problem, as I stated earlier, is that most engines not specifically set up to allow it run poorly le
44 N231YE : I based this off of a fairly new 172, with a fuel-injected IO-360.
45 JoeCanuck : As I understand it, lean of peak works best on engines with constant speed props. Some of the efficiency of a diesel comes from the fact that it is, e
46 SEPilot : If you re-read my post I said that AS IT COMES FROM THE FACTORY it cannot run lean of peak effectively. Being fuel injected, though, I strongly suspe
47 Meister808 : I always think this is funny, because the guys putting the same O-320s in airplanes down at Vero Beach (Piper) wholesomely support LOP operation in t
48 Meister808 : Negative... the only control system Cirrus uses incorporates a mechanical linkage between the throttle and propeller controls, incorporating both int
49 SEPilot : Not having had access to a late model Piper I did not know this. Thanks for the info. In fact, I did get the opportunity to fly a 1972 Piper Arrow fo
50 Mender : The wastegate is used to spill excess boost pressure not to control the mass airflow. The MAF meter on you car doesn't work like you describe either.
51 Post contains links Analog : I should have been explicit about understanding this (that the variable geometry intakes are there to control air speed/pressure in the engine). My p
52 N231YE : Don't forget, some of the big piston radials (notably, many of the P&Ws) used a form of fuel injection, where the fuel was sprayed onto the impeller
53 SEPilot : Some do, some don't. As I said in an earlier post, I flew an Arrow with a 200HP IO-360 that would happily run lean of peak. But I have flown others t
54 VC10 : The Wright 3350 on the Connie from the 749 onwards was fuel injected directly into each cylinder head, using two mechanically driven fuel pumps, one
55 Post contains images SEPilot : Thanks for this tidbit. I really appreciate these gems from people who really knew those magnificent old machines; it is what really makes this forum
56 Post contains images Analog : My question is how the common source of fuel affect this? I don't understand why the same issue wouldn't exist if the two pumps sucked fuel from diff
57 SEPilot : It certainly does. I have faced it many times in designing machine tools.
58 Post contains images N231YE : Interesting. Those cranky old R-3350s had even more of "attitude" problems than I thought I wonder why...maybe small changes between the manufacturer
59 Post contains images KELPkid : Go to Avweb.com, and search for "John Deakin" and "Lean-of-peak". You will find your answer...basically what SEPilot has been saying all along: crapp
60 Post contains images N231YE : Sorry, I went back and re-read the posts in this thread, and you're right. Nice website, by the way
61 Viscount724 : On that point, why do light aircraft like Cessna 172s etc. that presumably should be at least as hi-tech as current cars need mixture controls when t
62 Post contains images Analog : Current cars in the 1930s perhaps. Crazy, isn't it? They work fine up to and above 14k feet. Most cars can make it up to Pikes Peak in CO, US, which
63 SEPilot : We're talking about different examples of exactly the same engine made by the same manufacturer. Some just have better matched injectors than others.
64 VC10 : Each Wright 3350 had one fuel/air metering unit which determined the total fuel flow requirement for all 18 cylinders at any given time. This was del
65 KELPkid : Raton Pass (on the New Mexico/Colorado border, on Interstate 25) seems to be a good test for most cars...I've had more than one car (both American an
66 Post contains images Analog : Of course with manual controls the human is part of the system. Even moderately well trained humans tend to have high error rates, though humans, unl
67 SEPilot : Most errors that the pilot makes (except for fuel management) do not silence the engine; the problem with electronic controls is that an electrical f
68 N353SK : Leaning the mixture also helps to alleviate excess lead buildup. 100LL avgas has a lot more lead in it than most engines built after the 1970s need.
69 Post contains images Analog : That's sort of my point. Humans are good at detecting when things are wrong and compensating; electronics are limited to their pre-programmed reactio
70 Post contains images KELPkid : Unfortunately, in an aircraft, a failure that would cause the engine to still operate, but at reduced power, could very well be fatal, especially if
71 Bond007 : I disagree. A electronic fuel management system is far superior than any human performing the same task manually. A fully redundant system is infinit
72 SEPilot : I certainly do not question the fact that it is possible to make an electronic system to control an aircraft engine that would do a far better job th
73 DKCFII : A bit off topic but I've noticed that too because I grew up in NY and the premium there is 93 octane while out here it is 91. Does anyone know why th
74 Post contains images KELPkid : Because the refiners only care about the octane rating at the altitude their refinery is at, and because the government octane rating is tested at th
75 Post contains images Analog : In NY I've seen premium vary from 92 (I think) to 94 (R+M)/2octane. At higher altitudes the air pressure is lower, which lowers the chance of knockin
76 Bond007 : Little more than pilot training and perception. The more safe you make an aircraft, the more the pilot is potentially encouraged to be less 'safe'. T
77 N231YE : I'm sorry, I forget where I read it, but one of the theories dealt with pilots thinking that their parachute-equipped Cirrus was invincible (causing
78 JoeCanuck : A while back I saw a program on vehicle safety, (I forget the name of the program). One safety investigator posed the question; "what would make a per
79 Analog : Back in the days before collapsible steering columns you pretty much had the latter. People are willing to accept a certain amount of [perceived] ris
80 Bond007 : Right, but the problem is when the risk then becomes greater than it was before the 'safety device'. The Cirrus I believe, is an example of that. You
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When On Approach Do Aircraft Engines Get Louder? posted Tue Jun 5 2007 19:11:50 by Aaden
Spoilerons On Swing-Wing Aircraft posted Wed Apr 4 2007 01:08:01 by Blackbird
"Turbulence" Switch On Autopilot - Which Aircraft? posted Sat Nov 19 2005 19:12:50 by Julesmusician
Two Different Engine Makes On The Same Aircraft? posted Wed Sep 28 2005 18:57:47 by JAM747
Flashing Red Lights On Bottom Of Aircraft posted Mon Sep 12 2005 14:58:44 by TimePilot

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