Flight Planning

[GeorgePerry]

Gents I responded to a PM about flight planning...and I thought I'd post for all to see.  It's always good to hear what others do or the experiences they've had.  Looking forward to hearing others comments:

I wrote a very detailed response to your PM, but when I clicked preview it disappeared:-(

Anyway, here's the readers digest version of what I wrote previously that I hope will answer your questions.  As you said there are lots of opinions about power management and I'll add mine to the bunch.

Caveats: 1. Power settings don't necessarily hurt an engine or reduce service life...Temperatures do. Specifically CHT and Oil temps must be kept in the green. 2. Power settings for a normally aspirated engine are altitude dependent so "exact" climb and cruise settings will change as density altitude changes.  3. Engines are big air pumps and the most efficient way to operate them is to leave the throttle wide open as much as possible.  4.  I go high as often as I can (winds permitting) that way I can operate with the Throttle wide open and keep the engine below 75% continuous.  5. I think of the mixture as a money handle.  I use the mixture and the prop rpm settings to control power and fuel flow first, then the throttle if I can't get the engine set where it needs to be.

Climb  I use WOT and 2700 rpm until 1500 ft AGL then bring the prop back to 2600 for noise.  I lower the nose to climb at >100 KIAS to keep temps down and increase fwd visibility.  I use ram air boost above 3000 in clear air.  The old rule of thumb that says to keep the MP at or below prop rpm is nonsense.  IO-360 isn't turbo charged so you can't bootstrap them and if you climb quick enough DA will put you below 75% power within about 5 minutes anyway.

Cruise High Altitude(>9K), Fast speed, I use WOT and 2500 rpm.  High Altitude and economical cruise I use WOT and 2350...each at least 50 deg ROP to keep the temps good in the thinner air or if the DA is high.

Mid Altitudes (5-8K) Fast speed, I use 25 MP and 2500 rpm. 50 deg ROP.  Economical cruise, I use 21 in MP and 2350 rpm, 50 deg ROP

Low Altitudes Fast I use 26 MP and 2500 RPM 50 deg ROP.  Economy cruise I set 21 MP and 2350 rpm, 50 deg ROP.

Speeds and fuel burns I see are: 

High/Fast - 145-150 KTAS @ 10.0 GPH.  High/Econ - 137-140 KTAS @ 9.3 GPH. 

Mid/Fast - 147-152 KTAS @ 11.5 GPH.  Mid/Econ - 140 KTAS @ 9.5 GPH. 

Low/Fast - 145 KTAS @ 12.5 GPH.  Low/Econ - 135 KTAS @ 9.7 GPH

based on my experience in my fairly stock M20 F, I plan most trips @ 10.5 GPH and 140 KTAS over the ground. That works out pretty close and it accounts for climb/decent speeds and fuel burns.  Longer trips are a bit faster with a bit less average fuel burn.

Hope this helps...

GMP

 

[TurboExec]

George,

Have you tried running LOP?

These are the typical numbers I see LOP, no boost.

High/Fast - 145-150 KTAS @ 9.5 GPH.  High/Econ - 137-140 KTAS @ 8 GPH. 

Mid/Fast - 150-152 KTAS @ 11 GPH.  Mid/Econ - 140 KTAS @ 8.5 GPH. 

Low/Fast - 145 KTAS @ 10.5 GPH.  Low/Econ - 135 KTAS @ 7.5 GPH

My fuel burns seem to be .5 - 1.5 gph less running LOP.

[GeorgePerry]

Adam,

I have a single Alcor EGT right now with stock injectors...so I don't run LOP.  I suppose I could but don't out of an abundance of prudence. 

Just got my Gami's in the mail and the JPI is coming in the next couple of weeks.  Once the set up is complete, I might give it a try.  I'm not hard over either way.  I grew up flying ROP and I like the engine sound it makes when it's ROP.  LOP just "feels" and "sounds" wierd...but I suppose it's all what your used to.

I keep my fuel burn low with agressive leaning.  I lean right after start up.  I lean in the run up, I lean in the climb, I lean the minute I touch down.  Keeping the throttle wide open and the mixture set correctly really drops the FF.  I've got a brand new oil cooler with works really well and with cowl flap and airspeed management CHT's havn't been a problem.

Your bird is a turbo...correct?  I would think that setting 25 MP and 2500 rpm at 12000 ft would yield some decent FF and TAS figures.

[TurboExec]

Quote: GeorgePerry

I have a single Alcor EGT right now with stock injectors...so I don't run LOP.  I suppose I could but don't out of an abundance of prudence. 

Your bird is a turbo...correct?  I would think that setting 25 MP and 2500 rpm at 12000 ft would yield some decent FF and TAS figures.

[GeorgePerry]

For what it's worth this is what Lycoming has to say:

http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf

Lycoming recommends cruise operation at peak EGT or TIT, which is the point where the best economy range starts. For optimum service life, Lycoming suggests operating 50 degrees rich of peak EGT or TIT.

Lycoming is in complete agreement that it is possible to operate an engine on the lean side of peak TIT. It is done on engines in our well-instrumented Experimental Test laboratory every day. There is nothing detrimental in operating an engine in this manner. However, we can attest to the fact that things that work well in the test laboratory have not always proven successful in service.  s

In the sales literature provided for this “new” technique, it is stated that Lycoming recommended this operational procedure in an owner’s manual that dates back to the late ‘60’s. No mention is made why it is no longer recommended on our present engines. The fact is that the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues. Burned pistons, valves, ruined rod and main bearings were traced to the inability of pilots to utilize this technique with the instrumentation and distractions found in the typical general aviation aircraft. If Lycoming felt that this was indeed an efficient and reliable method of operation, you can be sure that it would be in our recommended procedures.

[TurboExec]

You should get over on the AOPA boards, there is a big thread running there on LOP as we speak...and many more that we have gone through in the past.  If Greg_D pops in I'm sure he'll add his comments as to Lycomings attitude towards LOP operations.

[GeorgePerry]

I'm not saying that LOP isn't a good way to go...All I'm saying is that the "factory" doesn't officially recommend it.  Until individual pilots have access to the same level of knowledge that the Lycoming factory does I'm going to defer to their expertise and recommendations.

My opinion only…Others may opt to run on the LOP and that’s fine.  But for me I’m going to trust the guys who make, test, and sell the engines over individual users.

 

[N9660M]

George, thanks for the info.  You're using power settings in line with what I was considering, so think I'll adapt them.

Take care,

Jim

[Greg_D]

There are a few reasons not to run LOP, but because "the factory doesn't recommend it" is probably the weakest of all.  If you carefully look at the data and the history, it quickly becomes apparent why the factory doesn't support LOP.

And to be clear, the factory doesn't say LOP operations isn't possible.  They just think 98% of the pilots out there are "too dumb" to do it without burning up their engines.  I must be in the other 2% if that's true.  Seriously, I doubt that's the case, but I haven't "burned up" any engines yet, don't intend to,  and I've been running that way for years, including with Lycoming powerplants.

BTW, the guys who developed and teach LOP ops for the GA crowd are not exactly "individual users".  They have very sophisticated engine test stands that were used to develop and test these procedures.  These stands are still used today for seminars.  The procedures they teach are based on proven science and loads of data.  It's not just personal feelings based on hunches.

In the end, it comes down to who you want to believe.  I choose to go with the guys who present actual data and have proven results to show me.  Others may opt to go with what the factory tells them, with no data to support their claims.  I would encourage others to look at both sides of the argument before deciding.  Granted, one side is going to make you look at data and think before you decide.  The other side is going to tell you to do it their way because they know best.  Not a lot of thinking required there.  Hey, maybe they're targeting the 98% group with that approach.

Hey George, do you pay MSRP when you purchase your automobiles?  After all, it's the factory that comes up with those prices, right?

[GeorgePerry]

Greg,

Lets try to keep comparisons realistic...LOP to MSRP...two different animals and a bad comparison.  If it works for you great.  Lots of folks swear buy LOP.  I'm not saying you or they are wrong...on the contrary, you might be right.  I clearly said that running ROP was a personal opinion and the way I prefer to operate my engine. 

Fact: Lots of pilots run engines LOP all the way to TBO with no problems.

Fact: Pilots that don't operate LOP correctly (LOP with greater than 75% continuous power) stand a much higher probability of engine longevity issues.

Fact:  1 burnt IO-360 exhaust valve will cost well in excess of $1000 to fix.  It'll take alot of fuel savings to make up for the cost of that valve. 

Opinion:  A few hundred bucks a year in "extra" gas costs is cheap insurance and running the engine the way the factory says to can't hurt, LOP can if not done properly.

Cheers

GP 

 

[Greg_D]

George, I think you're confusing facts and Old Wive's Tales.

Fact: Pilots that don't operate LOP correctly (LOP with greater than 75% continuous power) stand a much higher probability of engine longevity issues.

I'm not sure which part you consider "fact" here.  Is running LOP at greater than 75% power not operating LOP correctly?  If so, where is that "fact" documented?  Also, what data are you using to support your asertion that running at greater than 75% power causes a much higer probability of engine longivity issues?  Again, are these really "facts" or merely your feelings on the matter?  I know several pilots who routinely run at 85% LOP and have run several engines to and/or past TBO with no cylinder problems whatsoever.

Fact:  1 burnt IO-360 exhaust valve will cost well in excess of $1000 to fix.  It'll take alot of fuel savings to make up for the cost of that valve.

OK, a burnt exhaust valve will cost some money to repair.  What does that have to do with LOP? Is it a "fact" that LOP ops burns vavlves?  If so, where's the evidence and data to prove that?  LOP, your exhaust valves run cooler, much cooler than they do ROP.  By the way, the spot where the guys you trust to tell you how to run your engine (Lycoming) is almost the worst possible place you can be if you are worried about burning exhaust valves or overall engine longivity.

Opinion:  A few hundred bucks a year in "extra" gas costs is cheap insurance and running the engine the way the factory says to can't hurt, LOP can if not done properly

So, in your opinion the extra gas is cheap insurance?  Maybe, but it would take much more gas than the factory recommends.  You'd need to be much richer than 50 ROP to reduce internal combustion pressures to the levels comparable power setting on the LOP side of the curve would deliver.  How rich?  Try about 180 ROP.  That's quite a bit of gas and for me it adds up to a few thousand dollars a year. Oh, and running your engine that way is also very dirty. The primary reason I run LOP isn't for fuel savings though.  It's because it is easier on the engine.  As for the notion that running the way the factory recommends "can't hurt", well that's just plain wrong.  It does hurt.  You only need to looka at the data to realize that.

In the end it comes down to a personal choice.  You can look at the data and science and decide for yourself.  Or you can blindly beleive what the guys who are building the engine tell you to do (without any data to support their assertions).  I believe the more prudent way to operate is by using facts rather than Old Wive's Tales.

[GeorgePerry]

You can lead a horse to water, but you can't make him drink...that's true.  But you can always drown the stubborn sob.

I'm not trying to convince you of anything, and I don't want too.  Fly your plane however you want.  All I'm saying is there are two sides to every argument.  All of my statments are easily verifyable mostly on the factory website...but you've already made it clear you don't trust lycoming.  So each to his own

For others' reading this thread, don't take my word for it....here's what lycoming has to say.  But lycoming and I could be always be wrong and Greg could be right...or some combination of the two.  Who knows??

http://www.lycoming.textron.com/support/troubleshooting/resources/SSP700A.pdf

cheers

[Greg_D]

George, you're very correct that all of your statements are ealisly verified by statements posted on Lycomings website.  No argument there.  It's just that to believe the statements on their web site, you have to believe what they are telling you, without seing any of the data.  Again, they readily admit LOP operations are possible.  They just claim that 98% of pilots are too stupid to do so without botchig things up.  If you actually take the time to look at the data, you'd see the real reasons why Lycoming doesn't supprt LOP.

By all means, read the linked document Lycoming posted.  But before you do, go read the articles by John Deakin on Avweb.  Then spend some time watching a heavily instrumented engine or two running on a test stand.  Then flip through the reams of science, data and inspection reports that suport LOP.  You'll probably then laugh when reading the Lycoming document because you'll realize what it truly is.

Ask yourself if you're in the 98% group or the other group.

[TurboExec]

I was afraid this would turn into a LOP v. ROP thread...

I run LOP because I educated myself about it, and read everything available on the subject including what Lycoming has to say....something I think all aircraft owners should do!  Even if you decide agains LOP at least you understand it, not just blind faith of the manufacturer or whoever.

[Greg_D]

Quote: TurboExec

I was afraid this would turn into a LOP v. ROP thread...

[GeorgePerry]

Quote: Greg_D

[TurboExec]

Start Reading.....one of these articles explains exactly why 50 dF ROP is probably the worst place to run your engine.

http://www.advancedpilot.com/

http://www.avweb.com/news/airman/are_you_wasting_avgas_196816-1.html

http://www.avweb.com/news/pelican/182045-1.html

http://www.avweb.com/news/pelican/182179-1.html

http://www.avweb.com/news/pelican/182176-1.html

http://www.avweb.com/news/pelican/182081-1.html

http://www.avweb.com/news/pelican/182082-1.html

http://www.avweb.com/news/pelican/182084-1.html

http://www.avweb.com/news/pelican/182085-1.html

[TurboExec]

This was a graph that help me to understand what was going on in the combustion chamber ROP v. LOP...

http://www.avweb.com/newspics/pp18ms.jpg

[Greg_D]

[Greg_D]

Adam beat me to it while I was composing my last message.  Have fun reading!

[GeorgePerry]

Quote: Greg_D

read the articles by John Deakin on Avweb. 

[Greg_D]

I don't think you've read *all* of the information.  Far from it.  For starters, John isn't the only one who's posted relevant articles there.  He has the most, at that one sight.  Mike Bush also has some articles there.

You are quick to cast doubt on the credibility of GAMI because they make fuel nozzles that may or may not help a customer run LOP, yet you are willing to take Lycoming at their word when they tell you to do something without anything more than "we told you so".   And Lycoming has a much bigger financial liability at stake in all of this than GAMI ever will.

You are mistaken that the data GAMI has comes from a single engine.  They have instrumented multiple engines on their test stands and found the same results on each of them.  Some have some peculiarities, but the graphs you see posted apply to all gasoline powered piston engines.  The data downloads from individual users are merely used to back up data developed in the labs.

As far as comprehensive studies, many of those were done a long time ago.  The military looked at ways to run LOP during WWII, but they didn't have the same concerns about longevity that we individual aircraft owners have.  The airlines however, did look for longevity.  They were getting 600 hour TBOs running ROP.  After switching to LOP operations, they got 3600 hour TBOs on the very same engines.  They have millions of logged hours documenting this.  One of the 1st pieces of information you're given to read at the APS class is a book on the basic theory and operation of the Curtiss-Wright Turbo Compound engine, written in 1957.  Reading this litle gem, it's clear that LOP operations were SOP in those days.  The point is, all of the LOP stuff isn't new.  It's well documentted, and has been around for a while.

There is also a study that was run on a light twin where one engine was run LOP and the other ROP.  I can't find it now, but I'll keep looking for it.  The results were surprising, to some that is.

Again, every airplane manufacturer that's using Continental powerplants has a section in their respective POHs that describes LOP operations, some *require* it on certain airframes. 

In the end, it's up to the individual owner to decide.  You can run on blind faith with what the factory is telling you or you can study the subject a while and come up with your own conclusions.  The downside to the second choice is that you may voluntarily place yourself in the 98% group instead of having Lycoming do that for you as in option one.

[KSMooniac]

George, you *really* should go take the Advanced Pilot Seminar course if you consider yourself open to fact and reason.  They have done all of the hard work gathering the data and distilling it into a very positive educational experience.  It is the closest thing to any "comprehensive study" you'll find in the public arena, and you will be convinced of the merits and especially why running around at 50 dF ROP is about the worst place to be.  (Aviation Consumer is about as unbiased as they come, so you might read them too.)  Sure, you might make a 2000 hr TBO run, but will likely need to replace your cylinders.  What if they could go 4000 hrs?  That coupled with the fuel savings and the cleaner running characteristics make for a *very compelling* reason to go LOP all the time.

Lycoming is acting like an ostrich with it's head in the sand.  TCM isn't much better.  Cirrus got bold by mandating LOP ops for their turbo-normalized SR22 *and* took on the burden of the engine warranty when TCM refused to honor it because of LOP.  Now TCM has increasing amounts of egg on their face as the trouble-free hours pile up.  Like Greg said, sooner or later the knowledge will be commonplace and these kind of arguments won't crop up, but until then it will take individuals like us to try to convince folks like you to become more educated on the subject and *then* decide for yourself.  Blindly believing Lycoming when they have a vested interest in keeping you ROP is not wise...think about it...if everyone demanded LOP capability, they (a) would have to improve their induction systems and ( would sell fewer replacement cylinders at a minimum.

[GeorgePerry]

Scott,

I'm open to any and all information...Your post alludes to this, but I don't see any info.  Just your opinion.  If your aware of solid data by an unbiased group please post it for all to benefit from

thanks

GP

[KSMooniac]

George, I absolutely sensed that you want to learn all about this, but unfortunately a web forum is grossly inadequate to convey all of the data and science that backs it up, so I can't just post what you are looking for.  I'm not saying this to dodge anything, either, so I hope I don't come across as a smug internet tough guy.    Truly the best place for you to go to get this data is the APS group...they are unbiased believe it or not.  That venture grew out of the ignorance and old wives tales at the urging of a few folks on the Avsig BBS forum many years ago to fill the void that exists in regards to knowledge of engine management.  They did all of the research, gathered the data and developed a wonderful short-course to pass it on to those pilots that want to know everything they can about operating their engines.  I learned more in their 2.5 day course than I did in many of my full-semester engineering courses.  I *saw* real-time data from their test stand demonstrating the principles conveyed in the class.

You might think that GAMI is promoting LOP ops so they can sell more GAMIjectors...that is false.  APS is a separate venture from GAMI, although one of the APS principals is also a GAMI principal.  GAMI turned into a company *because* of the research that led to the APS class...they saw how superior LOP ops were in general and that many factory engines couldn't run LOP due to unbalanced fuel flows.  In a classic American success story, they developed a product to fix that problem.  If you don't need GAMIjectors to run LOP, then they won't sell them to you!  (I didn't need them.)

The key to the debate is first understanding the scientific principles behind the combustion event and how it relates to internal cylinder pressures and temperatures.  After that is understood, then the nuances of mixture management make more sense, and more importantly the recognition and diagnosis of engine problems becames easier as well.  There really is no better way to learn it than to attend their course, or perhaps take the on-line version for starters.  What you don't get is a cookbook method to simply set 50 dF LOP and trust that it is OK...you'll end up fully understanding what is happening when you move the red knob of death.   

The easiest free education would come from reading all of Deakin's articles posted on Avweb as mentioned earlier.  They only begin to scratch the surface, though.