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Pressure Carburetor?
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kamala(at)MSN.COM
Guest

Posted: Sun Sep 30, 2007 6:55 am Post subject: Pressure Carburetor?

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  cw, you were missed at the flyin.  did you ever find any of the mango  air stuff. all of this carb talk makes me glad I have fuel injection.  mason

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yourtcfg(at)aol.com
Guest

Posted: Sun Sep 30, 2007 7:37 am Post subject: Pressure Carburetor?

GREAT TO HEAR FROM YOU!!  Call me at 360-903-6901 on a different topic.  Back to the carbs.  If all Commanders had a 6 dyl egt and dig fuel flow, maybe it would be worth messing with.  Yours is the only one I know that is equipped that way. and I remember talking to you about the leaning and you said you were running with the throttles wide open (fuel enrichment valve wide open) so manually leaning would have made a big difference.  My concern with this thread is that the poor guy who started this post might try to lean his AMC carbs without the benefit of that technology.  Like Bob said, this is ancient tech. If your airplane isn't equipped properly, you can do serious damage to your engines by messing with the mix and you had better leave it the stink alone.  I am going to the airport today to get the fuel info from my airplane and check it against the mfg. fuel flow (I just flew it 16 hours) I'll bet it is within 5%.  GREAT   TO HEAR FROM YOU!!  Lets talk.  jb 

 

 

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bowing74(at)earthlink.net
Guest

Posted: Sun Sep 30, 2007 4:06 pm Post subject: Pressure Carburetor?

“Commander ownership is not for everybody”  

bb  

         

  

From: owner-commander-list-server(at)matronics.com [mailto:owner-commander-list-server(at)matronics.com] On Behalf Of yourtcfg(at)aol.com

 Sent: Saturday, September 29, 2007 10:00 PM

 To: commander-list(at)matronics.com

 Subject: Re: Re: Pressure Carburetor?  

  

     

HI MILT  

    

Sorry, but I stand by my statement.  Manually leaning a properly adjusted pressure carb is, wrong.  As I had stated in an earlier post (and as said in the referenced article), it is possible to do it, but why??  Properly adjusted, the AMC unit does a great job.  I just flew my 680E 2800nm, 16hrs to the fly-in in TX  I fueled the outboard tanks and after about an hour on the main, switched to them  They ran 1.5 hours and just as I was reaching for the selector switch, the LH engine sputtered.  I no sooner switched that engine tha the RH sputtered.  The point is, with properly adj carbs, they are consistent enough to use exactly he same amount of fuel.  Not science, but imperical information.  I have flown many bathtub Commanders and have yet to fly one with an EGT.  Short of that installation, leaning the carbs would be a random gues s at best.  Is it possible to squeeze a couple of extra gallons per hour out of your engines, maybe.  But if your Commander operating budget is so cramped that three or four GPH will make a difference, I strongly suggest you sell your Commander.  BTW, I don't believe that running over square is bad, (it happens on every TO), or that you can shock cool and engine with the throttle (rapid mixture change will however) or that running LOP is bad in a normally aspirated engine.  But manually leaning you AMC carbs is a bad idea, not recomended by the manufacture of the carb, engine or airframe and completely unnecessary;-)  jb    

 

 

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bowing74(at)earthlink.net
Guest

Posted: Sun Sep 30, 2007 4:06 pm Post subject: Pressure Carburetor?

This is great!

It hasn't "hit the fan" like this since the "Sump-Gate" days of '01.

bilbo



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WINGFLYER1(at)aol.com
Guest

Posted: Sun Sep 30, 2007 5:26 pm Post subject: Pressure Carburetor?

Milt thanks for the info. It is leaking from the bottom of  the carb.  I think it is the carb over flow port. For example, when you prime the carb too  much you see the fuel drip from the carb. The left carb is fine. Thanks  Gil



See what's new at AOL.com and Make AOL Your Homepage.

  [quote][b]

yourtcfg(at)aol.com
Guest

Posted: Sun Sep 30, 2007 5:30 pm Post subject: Pressure Carburetor?

OH NO!! You said the "S" word!!  ;_)  jb 

   	  Quote: 	
		   	  Quote: 	
		  "Sump-Gate" 	
	


 

 

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hawkins(at)cms.udel.edu
Guest

Posted: Mon Oct 01, 2007 3:23 am Post subject: Pressure Carburetor?

Wow!  I had no idea my pressure carburetor question would spur this kind of discussion!  It's a good one though - quite important is seems.



N2760B is a very basic machine.  CHT only on one cylinder for each engine - nothing else. No EGT. No fuel transfer system.  Sounds to me like best approach is to run with mixtures "full rich" and let the pressure carb do it's job.  Leave mixtures "the stink" alone.



Matt



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hawkins(at)cms.udel.edu
Guest

Posted: Mon Oct 01, 2007 4:43 am Post subject: Pressure Carburetor?

Jb-

  

 Thanks for  this!  Perfect description of what we're seeing.  

  

 Left engine (with  properly re-built carb) does exactly as you say - rapid change in engine  operation as you get close to idle/cut-off.   Right engine seemed to  lean somewhat like a "regular" engine.  I'll double-check that this  week.  Right engine is the one that always seemed to run rich and foul  plugs too.

  

 We'll have a look at  this when we can.  Glad to hear that when "auto lean" is not working  properly the fallback in the design is to lean manually.  Makes good  sense.  In the short term, sounds like we just need to be aware of whether  or not the auto lean is running properly or not.

  

 Good news is that  all exhaust pipes are a nice ash grey - no black soot/residue.  Perhaps  engines are still bedding in?  

  

 What's your thought  on the wire-type plugs?

  

 Matt

 [quote]   

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BobsV35B(at)aol.com
Guest

Posted: Mon Oct 01, 2007 8:19 am Post subject: Pressure Carburetor?

Good Morning Matt,   

 That may very well be the best answer for you and your airplane.

  

 However, may I point out that even fifty years ago there were some who did  learn how to operate those engines safely and efficiently by judicious use of  the mixture control.

  

 May I first ask just what style of Pressure Carburetor your engine has?  

  

 Does it have an AMC unit? 

  

 There seems to be a lot of mention about pressure carburetors implying that  all pressure carburetors have Automatic Mixture Controls installed. 

  

 That is definitely NOT true. 

  

 As was mentioned by Milt, the PS5c is not one that will provide any  altitude compensation at all, yet it is probably the most commonly used pressure  carburetor in the GA fleet.

  

 The designers of the fuel controls had to be people who fully understood  the vagaries of engine operation. 

  

 They knew the difficulties present in trying to get even distributor of  fuel and air to each and every cylinder as well as the necessity for each  cylinder to be manufactured to close enough tolerances so that the compression  of each cylinder was as close as possible to being identical and so that the  breathing efficiencies of the intake systems were identical.  

  

 They then designed a fuel delivery system that would work adequately for  engines that were at the edges of acceptability when evaluated for cylinder to  cylinder consistencies. 

  

 Have you ever heard a reference to the "Shaky Jakes", when one is  discussing Jacobs Aircraft Engines?

  

 The reason they were described as shaky was because the early Jakes had a  very simple fuel delivery system that caused the lower cylinders to get a LOT  more fuel than the upper ones.  Most of the later development of the Jacobs  engines were directed toward improving that mixture distribution.

  

 Later, more modern, round engines used many schemes to provide better  distribution. It was thought by all, that it would be best if the pilot did not  have to operate any controls that would affect that mixture. 

  

 The development of the pressure injection carburetor with an AMC unit was  an effort toward simplifying the operation for the pilots of the day. It was  never completely successful.  The best units that were ever made were those  that were fitted to the latest P&W R-2800s and the Curtiss Wright R-3350s  which were the engines that powered the last of the piston airline fleet.

  

 When those engines were used in four engine long range airplanes, they  almost always had flight engineers assigned to operating the engines so that  adequate and proper leaning procedures could be used. For short haul airplanes,  the pilots normally just used the Auto Lean and Auto Rich functions. On those  rare occasions when range or endurance became an important consideration, even  we lowly aviators would do a bit of manual leaning.

  

 What point am I trying to make?

  

 You can do manual leaning of your aircraft even if you don't have the  modern equipment, but it takes a much greater understanding of the potential  vagaries of the combustion process than is generally made  available to we  aviators in our basic training. 

  

 JB mentioned monitoring the tail pipes to ascertain whether or not the  mixtures being provided by your fuel delivery unit are adequate. 

  

 That was, and still is, certainly one of the clues, but there are many  others.

  

 Attendance at a good engine course such as is provided by The Advanced  Pilot's Seminar folks will provide the basics, but they start off by saying  there is no reason to try to learn the basics if the airplane is not equipped  with modern monitoring devices.

  

 Having been an active aviator during the days when such stuff was not  available, I do have a few techniques which I can use to make a decision as to  whether or not it will be practical to operate at any setting other than full  rich.

  

 Let's forget about what you are flying now, and consider whatever airplane  you used when you were a student pilot. Let's say it was a Piper Cherokee 140.  Once you were set up in cruise, you may have been taught to lean the engine  until it got rough, then richen until the operations smoothed. You were probably  also told not to lean at all below some pre selected altitude.

  

 That method has good science behind it!

  

 Before you can decide how much fuel is needed for the total engine, you  must determine how even the mixture is from cylinder to cylinder. 

  

 A very easy way to check on that when flying that Cherokee was to monitor  the RPM while leaning. If the engine got rough before any RPM drop was noted,  the mixture distribution was atrocious. 

  

 If you were able to get a fifty to sixty RPM drop before any roughness  occurred, the mixture distribution was reasonable. 

  

 As an aside, that DID NOT mean you should operate it with the fifty RPM  drop, that was merely a way to check for good distribution. 

  

 Cessna formerly recommended that the 170 with a fixed pitch propellor be  leaned until it encountered a two MPH drop in airspeed. That was a good method  of finding a point just barely on the lean side of best power and it would  probably have given an EGT reading of about fifty rich of peak had we had EGT  gauges back then. For any GA engine being operated at 65 per cent power or less,  there is nothing you can do with the mixture control that will hurt the engine,  so Cessna's method worked well and was very simple.

  

 Back to the Cherokee!

  

 If the engine kept operating smoothly all the way until all four cylinders  quit running, the mixture distribution was perfect. 

  

 With a constant speed propellor, the same sort of test can be performed by  watching the airspeed. Obviously, the air must be smooth and the pilot capable  of holding altitude and attitude very closely while performing the check, but it  did, and still does, work quite well.

  

 If the distribution is good, you should be able to perceive an increase in  power by noting the increase in airspeed as the engine is leaned. Peak airspeed  will occur when the engine is developing peak power. That is, it will be getting  as much power as is possible from the fuel and air being delivered to the  engine.

  

 For what it is worth, most small normally aspirated piston engine get their  peak power when the mixture is at a point corresponding to an EGT temperature  that is approximately eighty degrees Fahrenheit cooler than the peak  EGT number and on the rich side thereof.

  

 Reason would tell us that the engine will run at it's hottest when the most  power is being developed, but tests have shown that to not be true. The CHTs  will be hottest when the engine is operated with an EGT set to somewhere  around fifty degrees rich of the Peak EGT temperature.

  

 If we do not have an engine monitor, we cannot tell precisely where the  temperature is being set, but we can evaluate the performance of the airplane.  

  

 If we lean the engine so that the airplane is going just as fast  as it will go with the RPM and manifold pressure being used, the engine will be  at the best power mixture setting and it will be just a wee bit richer than the  point where the CHTs will be the hottest!

  

 This is certainly NOT meant as a primer on how to lean your engine. 

  

 I just wanted to point out that there is  no easy cake recipe style of  approach. If you wish to rely on the efficacy of the installed fuel control,  that is great, but you should understand the process well enough so that you can  determine whether or not your system is working as it was designed to  work.

  

 That part of the equation is very difficult if you DO NOT have modern  engine monitoring equipment. The potential for finding a mechanic with a proper  flow bench and all the skill and knowledge to use it well is very  slim.

  

 It has been ten to fifteen years since I last priced a rebuild on  one of those fancy fully automatic carburetors for an Aero Commander, but I was  quoted a price of fifteen thousand dollars per carburetor. The owner elected to  donate the aircraft to a mechanics school as it was not economically viable to  overhaul those units.

  

 I have no idea whether or not any alternative carburetors were available  for that airplane, but installing a simple PS5c and modern monitoring equipment  would have been a lot cheaper alternative.  The rub would be whether or not  it was FAA approved!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/1/2007 6:24:06 A.M. Central Daylight Time,  hawkins(at)cms.udel.edu writes:

  	  Quote: 	
		  N2760B    is a very basic machine.  CHT only on one cylinder for each engine -    nothing else. No EGT. No fuel transfer system.  Sounds to me like best    approach is to run with mixtures "full rich" and let the pressure carb do it's    job.  Leave mixtures "the stink"  alone.



Matt

	


 





See what's new="_blank">Make AOL Your Homepage.

  [quote][b]

dowens(at)aerialviewpoint
Guest

Posted: Mon Oct 01, 2007 8:28 am Post subject: Pressure Carburetor?

Hey Chris! How you doin??? Dave Owens here with Aerial Viewpoint... Haven't

heard from you since your visit here at Hooks a few years back...  Did

Dreamcatcher get sold or scrapped??? I heard stories. Looking forward to

hearing from you.





David Owens

Aerial Viewpoint

N14AV

AC-500A-Colemill

hawkins(at)cms.udel.edu
Guest

Posted: Mon Oct 01, 2007 8:49 am Post subject: Pressure Carburetor?

Bob-

  

 That's definitely something I've gleaned  from this discussion.  All pressure carbs are NOT created equal.   I'll check on exactly what I have and let you know.

  

 Milt's view seems sound - if it can be  leaned - you should do it.  No sense in wasting fuel/$$    However, seems like I don't have the engine monitoring systems to do it  accurately or efficiently.

  

 Next time we're up on a smooth day we'll try  the airspeed method you suggest below.

  

 Your description of manual leaning is  exactly what I learned as a student pilot - and still use on a plane with no  EGT.  In fact, it's what my pilot who flies the Commander was trying to do  on the ground when engines were (apparently) running too rich.  Sounds like  we need to do it differently with the constant speed prop.

  

 Everything ran GREAT on our  flight last week - think Summit got the final adjustments right.   Good mag checks, not rough running, nice grey ash in the tubes (no black  soot).  Only question is whether or not the auto lean is working on the  right engine - and exactly what carbs we have (i.e. should it have auto  lean?).

  

 The shop that did the final "tweak" on the  left carb (and got it right) charged us $795.  Guess we did  OK!

  

 Milt sent me Chris Schuermanns PDF file that  listed the other two recommended shop in case we need for the right  engine.  We'll see.

  

 I'm also going to check to see if we have  the black gaskets or the newer orange.

  

 Matt

 [quote]   

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BobsV35B(at)aol.com
Guest

Posted: Mon Oct 01, 2007 9:57 am Post subject: Pressure Carburetor?

Good Morning Matt,   

 Sounds great!

  

 Learning and sharing knowledge is what it is all about. 

  

 You may well have a pressure carburetor that is not easy to manually lean.  

  

 After all, that WAS the goal of the folks who designed it.

  

 In any case, I urge you to read and study the data that is readily  available. A good start is to read John Deakin's articles on general engine  management. 

  

 I doubt if you will find very many folks who have current experience with  the fuel controllers on your airplane. 

  

 It is obvious that JB does have current information because he is so  insistent that your particular unit should only be leaned in an emergency.  

  

 I have no gripe with that philosophy, but I do think it is important that  an operator of such a unit be very knowledgeable as to just what it is supposed  to be doing.

  

 I strongly recommend that you do instrument the engine so that you will be  able to ascertain whether or not the automatic controls are doing what they were  designed to do!

  

 I believe checking it using the airspeed method is quite a bit beyond what  you should be doing with your current level of experience and lack of on board  monitoring equipment.. Those are highly stressed and sophisticated engines.  

  

 Treat them gently!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/1/2007 11:50:32 A.M. Central Daylight Time,  hawkins(at)cms.udel.edu writes:

  	  Quote: 	
		     That's definitely something I've gleaned    from this discussion.  All pressure carbs are NOT created    equal.  I'll check on exactly what I have and let you know.

    

	


 





See what's new="_blank">Make AOL Your Homepage.

  [quote][b]

hawkins(at)cms.udel.edu
Guest

Posted: Mon Oct 01, 2007 10:10 am Post subject: Pressure Carburetor?

Good advise!  Burning a bit of extra  fuel won't hurt me too badly in the short term.

  

 Matt

 [quote]   

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dongirod

Joined: 11 Dec 2006
Posts: 140

Posted: Mon Oct 01, 2007 4:34 pm Post subject: Pressure Carburetor?

Bob;

  

 I used to sit sideways in a Connie running R-3360 Turbo compound engines,  but its been a long time.  

  

 My question is this, since you remember more about those things, I recall  being told some where that aircraft engines use approximately 25% of their fuel  for cooling.  At what point in leaning do we get to where we save fuel, but  shorten the engine life?  And where is the crossover point.

  

 Thanks, Don

 [quote]   ---

BobsV35B(at)aol.com
Guest

Posted: Mon Oct 01, 2007 9:27 pm Post subject: Pressure Carburetor?

Good Evening Don,  

  

 I have never heard that particular number and I believe we would have to  better define the terms before we could either disagree or agree with that 25%  assertion.

  

 As to where does leaning cause additional wear, that is another tough one.  

  

 Running any engine too lean at high powers will cause big troubles.   However running one leaner than optimum at low powers will not hurt it all, but  it will burn more fuel per horsepower developed than is possible when the engine  is run so as to attain optimum BSFC (Brake Specific Fuel Consumption).

  

 I do not know the number used by your airline to lean the Turbo Compound  R-3350, but most users utilized a ten percent BMEP drop from the peak BMEP.  

  

 The procedure used by my airline was as follows. We would first chose a  desired BMEP number from the power charts. Just for kicks, let's say that the  desired cruise BMEP was 254. We would start out with the mixture in Auto Rich.  The mixture would be slowly leaned until the BMEP started to rise. When it went  above 254, we would throttle back until it was at 254, then continue to lean  until it was steady at 254 and where any further leaning would take the BMEP  reading below 254. That procedure determined the peak BMEP (Peak power) for the  manifold pressure being used.  At that time, we would continue leaning the  engine until the BMEP was reading 254 minus 24.5 or approximately 228 BMEP. Once  that spot ten percent leaner than peak power was found, the throttle was used to  add manifold pressure so as to bring the BMEP back to the desired cruise  power. We then checked the manifold pressure to be sure we were still below  the maximum allowed manifold pressure for the desired cruise power.

  

 Sound familiar?

  

 If we leaned the engine further, it would just lose power, but no harm was  done. However, if we richened it up a bit, the engine would overheat and it may  even go into mild detonation. It needed to be well lean of peak power to cool  properly.

  

 I don't know if you recall, but there is a shaft on the rear of the engine  which connects the two fuel injection controllers together. One unit is for the  front row and the other feeds the rear. That shaft would occasionally slip. When  that happened, one row would be running substantially leaner than the other. The  one that was getting more fuel would be carrying more of the load that was being  developed by the engine.  That row would burn the valves and sometimes even  have holes burned in the pistons while the row which was not getting enough fuel  would be running clean and comfortable.

  

 The place where any engine is most likely to develop engine problems are  when the mixture is at that point where the peak BMEP or peak engine power is  being developed. If the engine is run at that same power with a richer than  needed fuel mixture, the extra fuel will slow down the rate of burn and move the  point of peak combustion pressure to a point where the engine is able to operate  relatively cool. 

  

 That function is what is normally referred to as cooling the engine with  fuel and it is how we kept our cool during takeoff and climb regimes!

  

 Another way to cool the engine is to cool it with additional combustion  air. That is what happens when the engine is run well lean of best power. (Note  that I said best power, not Peak EGT. They do NOT occur at the same point) When  we leaned that nice big R-3350 ten percent lean of best power, we were running  at a mixture that was well lean of the best power point and the engine was being  cooled by that surplus combustion air.

  

 Normal cruise power for the 3350 was around 55 to 60 percent of rated  power. We were really running it quite conservatively. If we richened it without  reducing the manifold pressure, we defeated the air cooling effect and it would  overheat and cause all sorts of problems. 

  

 Leaner is cleaner and leaner is cooler. Cleaner and cooler is  generally considered to be better, is it not?

  

 So, if you want to extend engine life, run it at relatively low power  settings and run the mixture on the lean side of best power!

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/1/2007 7:35:20 P.M. Central Daylight Time,  dongirod(at)bellsouth.net writes:

  	  Quote: 	
		     Bob;

    

   I used to sit sideways in a Connie running R-3360 Turbo compound engines,    but its been a long time.  

    

   My question is this, since you remember more about those things, I recall    being told some where that aircraft engines use approximately 25% of their    fuel for cooling.  At what point in leaning do we get to where we save    fuel, but shorten the engine life?  And where is the crossover    point.

    

   Thanks, Don

	


 



See what's new at AOL.com and Make AOL Your Homepage.

  [quote][b]

dongirod

Joined: 11 Dec 2006
Posts: 140

Posted: Mon Oct 01, 2007 10:26 pm Post subject: Pressure Carburetor?

Good Evening Bob;

  

 I flew the Connie on the Shuttle Backup out of DCA, and yes it does sound  familiar.  But that was a long, long time ago,(67) I was in the last class  of Connie engineers.  I have all three ratings of F/E which with about $ 5  will get you a cup of coffee at most Starbucks.  I only slid off the wings  ( 14 ft.) twice in the winter snow, now it would break my leg, then it just  'stung'  like crazy.  I remember we were always happy to get a G as it  had gas heaters and we could pre heat the cabin.  I was so happy to get out  of the wing walking to check the fuel and climbing out on the engine to  check the oil, times sure have changed.  But your procedures sound  familiar, how do you remember all this stuff?  My hard drive gets full, and  when I left an aircraft, I tried to forget it so I could remember the new  aircraft and not get them confused.

  

 As to the 25% it is probably just a figure that some one once told me,  hanger talk, might be true at one particular power setting, might be false, not  sure.  I always figured that was part of the reason aircraft engines were  not very efficient in a power verses specific fuel consumption.  Now that  aught to start another discussion!

  

 Don

 [quote]   ---

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Tue Oct 02, 2007 4:43 am Post subject: Re: Pressure Carburetor?

 	  Quote: 	
		  which with about $ 5 will get you a cup of coffee at most Starbucks. 	




Heck Don,



I'll pay you $5 and feed you starbucks all day if you'll tell me Connie stories.

_________________
Milt

BobsV35B(at)aol.com
Guest

Posted: Tue Oct 02, 2007 6:05 am Post subject: Pressure Carburetor?

Good Morning Don,   

 I should be taking this response off list, but since it does reflect on  reasons why we are involved in this discussion, I will expand a bit about my  background and why it is that I am able to recall some of those details!

  

 It has to do with my age and lack of experience at the time. I started as a  DC-3 copilot in 1951, but that was a time of very rapid expansion and by early  1952,  I was checked out as a DC-6 copilot and had gotten fairly senior in  that slot. The DC-6 and the early Connies were vying for the title of Queen of  the airways.

  

 The Connie was winning in the looks department, but we could go faster and  carry a bigger payload on less fuel. The Connies could get in and out of  slightly smaller airports.

  

 They were both wonderful airplanes and definitely at the leading edge of  technology.

  

 Jet transports were merely wild dreams and there were many very  knowledgeable pundits who often expanded on the idea of why the jet  engine would never work on a transport style aircraft.

  

 I had trained while in the USMC to be an aircraft mechanic and had ended my  very short military career as an Aviation Electricians Mate.  That gave me  e a very strong interest in things mechanical. 

  

 In the spring of 1954, I was assigned to the first class to be qualified in  the brand new state of the art Douglas DC-7 which used those fabulous new Turbo  Compound R-3350s.  The operation of that engine was enough different that  we had several days of specialty training given by Curtiss Wright engineers  before we even went to type specific training for the airplane. 

  

 Even though the DC-7 was authorized to be flown by anyone who had a DC-6  type rating, my airline did send us to a full week of training for the  transition.

  

 Five years, later, when United Air Lines merged with Capital Airlines, the  Capital pilots that held DC-6 type ratings were given three bounces and turned  loose with the airplane.

  

 Back to 1952!

  

 My airline had been getting their Flight Engineers from the mechanic ranks,  but had decided to start using pilots for that function. While I was way too  senior to ever be required to fly as a Flight Engineer, my mechanic background  made me decide that I should get the rating as a matter of professional  qualification. 

  

 Since the only training courses that were available for flight engineers  back then were the ones run by the airlines, I had to self study. That meant  getting the books from the library and studying!

  

 By the time I went to DC-7 training, I had completed my home study regime,  passed the writtens, and conned the company into letting me take the flight test  in an airplane that was being flown to give flight checks to student engineers.  I volunteered to fly as copilot, and when all of the regular engineer trainees  had finished their flight checks, I was allowed to complete mine.

  

 When I attended DC-7 training, I was like a sponge soaking up all that new  information.

  

 After listening to those Curtiss Wright engineers explain why it was not  only best to operate the R-3350 on the lean side of best power, but why it  was imperative that we do so, I went back to those engine books I had been  studying to firm that thought in my mind. I even started to experiment with lean  side operations in my 1947, PS5c equipped, Continental E185 powered,  Bonanza.

  

 It was the beginning of a life long interest in the fine points of  operating piston engines and the stuff that I learned in DC-7 school has proven  to be very helpful in my quest for greater knowledge.

  

 It also helped me greatly when I finally finished my training for a  civilian A&P and eventually, my IA certification.

  

 That is why I can still remember those undoubtedly mundane and irrelevant  details.

  

 When the folks in Ada started to offer their Advanced Pilot Seminars, I  eagerly attended one of the first classes. I found that everything they taught  dovetailed nicely with my training from fifty years earlier and they explained a  lot of the technology that I had not previously fully understood. I am  sure I have a lot more to learn, but one of the main things I HAVE  learned is that the theories of engine combustion and mixture control have been  well known and agreed to since well before Lindbergh's time. 

  

 The major problem with mixture control has been developing simplified  methods of applying that knowledge!

  

 All that make any sense at all?

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



  

 In a message dated 10/2/2007 1:27:27 A.M. Central Daylight Time,  dongirod(at)bellsouth.net writes:

  	  Quote: 	
		  I was so    happy to get out of the wing walking to check the fuel and climbing out    on the engine to check the oil, times sure have changed.  But your    procedures sound familiar, how do you remember all this stuff?  My hard    drive gets full, and when I left an aircraft, I tried to forget it so I could    remember the new aircraft and not get them confused. 	


 





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moe(at)rosspistons.com
Guest

Posted: Tue Oct 02, 2007 6:21 am Post subject: Pressure Carburetor?

Bob,  

   

Thank you very much for a post which explains rich and lean very well.  This is the most literate thing that I have read in quite some time on the subject.  

   

Best regards,  

   

Moe  

N680RR  

680F(p)  

         

  

From: owner-commander-list-server(at)matronics.com [mailto:owner-commander-list-server(at)matronics.com] On Behalf Of BobsV35B(at)aol.com

 Sent: Monday, October 01, 2007 10:27 PM

 To: commander-list(at)matronics.com

 Subject: Re: Re: Pressure Carburetor?  

  

         

Good Evening Don,    

    

   

    

I have never heard that particular number and I believe we would have to better define the terms before we could either disagree or agree with that 25% assertion.  

    

   

    

As to where does leaning cause additional wear, that is another tough one.   

    

   

    

Running any engine too lean at high powers will cause big troubles.  However running one leaner than optimum at low powers will not hurt it all, but it will burn more fuel per horsepower developed than is possible when the engine is run so as to attain optimum BSFC (Brake Specific Fuel Consumption).  

    

   

    

I do not know the number used by your airline to lean the Turbo Compound R-3350, but most users utilized a ten percent BMEP drop from the peak BMEP.   

    

   

    

The procedure used by my airline was as follows. We would first chose a desired BMEP number from the power charts. Just for kicks, let's say that the desired cruise BMEP was 254. We would start out with the mixture in Auto Rich. The mixture would be slowly leaned until the BMEP started to rise. When it went above 254, we would throttle back until it was at 254, then continue to lean until it was steady at 254 and where any further leaning would take the BMEP reading below 254. That procedure determined the peak BMEP (Peak power) for the manifold pressure being used.  At that time, we would continue leaning the engine until the BMEP was reading 254 minus 24.5 or approximately 228 BMEP. Once that spot ten percent leaner than peak power was found, the throttle was used to add manifold pressure so as to bring the BMEP back to the desired cruise power. We then checked the manifold pressure to be sure we were still below the maximum allowed manifold pressure for the desired cruise power.  

    

   

    

Sound familiar?  

    

   

    

If we leaned the engine further, it would just lose power, but no harm was done. However, if we richened it up a bit, the engine would overheat and it may even go into mild detonation. It needed to be well lean of peak power to cool properly.  

    

   

    

I don't know if you recall, but there is a shaft on the rear of the engine which connects the two fuel injection controllers together. One unit is for the front row and the other feeds the rear. That shaft would occasionally slip. When that happened, one row would be running substantially leaner than the other. The one that was getting more fuel would be carrying more of the load that was being developed by the engine.  That row would burn the valves and sometimes even have holes burned in the pistons while the row which was not getting enough fuel would be running clean and comfortable.  

    

   

    

The place where any engine is most likely to develop engine problems are when the mixture is at that point where the peak BMEP or peak engine power is being developed. If the engine is run at that same power with a richer than needed fuel mixture, the extra fuel will slow down the rate of burn and move the point of peak combustion pressure to a point where the engine is able to operate relatively cool.   

    

   

    

That function is what is normally referred to as cooling the engine with fuel and it is how we kept our cool during takeoff and climb regimes!  

    

   

    

Another way to cool the engine is to cool it with additional combustion air. That is what happens when the engine is run well lean of best power. (Note that I said best power, not Peak EGT. They do NOT occur at the same point) When we leaned that nice big R-3350 ten percent lean of best power, we were running at a mixture that was well lean of the best power point and the engine was being cooled by that surplus combustion air.  

    

   

    

Normal cruise power for the 3350 was around 55 to 60 percent of rated power. We were really running it quite conservatively. If we richened it without reducing the manifold pressure, we defeated the air cooling effect and it would overheat and cause all sorts of problems.   

    

   

    

Leaner is cleaner and leaner is cooler. Cleaner and cooler is generally considered to be better, is it not?  

    

   

    

So, if you want to extend engine life, run it at relatively low power settings and run the mixture on the lean side of best power!  

    

   

    

Happy Skies,

 

 Old Bob

 AKA

 Bob Siegfried

 Ancient Aviator

 Stearman N3977A

 Brookeridge Air Park LL22

 Downers Grove, IL 60516

 630 985-8503  

  

    

   

    

In a message dated 10/1/2007 7:35:20 P.M. Central Daylight Time, dongirod(at)bellsouth.net writes:  

   	  Quote: 	
		      

Bob;  

    

   

    

I used to sit sideways in a Connie running R-3360 Turbo compound engines, but its been a long time.    

    

   

    

My question is this, since you remember more about those things, I recall being told some where that aircraft engines use approximately 25% of their fuel for cooling.  At what point in leaning do we get to where we save fuel, but shorten the engine life?  And where is the crossover point.  

    

   

    

Thanks, Don  

  	
  

  



 

         

  

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BobsV35B(at)aol.com
Guest

Posted: Tue Oct 02, 2007 6:26 am Post subject: Pressure Carburetor?

In a message dated 10/2/2007 9:22:51 A.M. Central Daylight Time,  moe(at)rosspistons.com writes:

  	  Quote: 	
		     

Bob,   

    

Thank you very much    for a post which explains rich and lean very well.  This is the most    literate thing that I have read in quite some time on the    subject.   

    

Best    regards,   

    

Moe   

N680RR   

680F(p) 	


 

Thank you very kindly Moe,

  

 Knowing your background, that is especially heartwarming.

  

 Happy  Skies,



Old Bob



 Do Not  Archive



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