Flight Planning

[Greg_D]

If I ever win the lottery, I'm going to round up all of the "open minded" folks that don't see the benefits of LOP operations and buy them a ticket to Ada, OK and pay for their tuition to the APS course.  Of course, by the time that happens, there won't be but a handful of them anyway.  And within that handful, there will still be those "open minded" ones who've already made their minds up anyway.  You know, the ones who believe the GAMI data is all "cooked" or somehow incomplete, just to sell some injection nozzles, yet fall for Lycoming's  completley unbiased crock hook, line and sinker.

 

Seriously George, please tell us why you think GAMI is biased and why you think Lycoming isn't.  That seems the be the root issue for you.

[GeorgePerry]

I'm not saying that one is more biased than the other...it's just a question of motive.  Gami sells fuel injectors which by all accounts are "almost" a requirement to run LOP.  Lycoming sells engines and could care less about how much fuel does or does not go through them.

With that said, the Gami site has some very good literature on LOP operations and the science behind it.  I found it an interesting read and a compelling argument in favor of LOP. 

http://www.gami.com/articles/bttf.php

It would be nice to see an independent organization verify Gami’s claims.

[Greg_D]

The motive question is interesting.  I've owned 4 airplanes and only 1 needed GAMIs to run LOP. 

In fact, GAMI requires you to run a fuel flow test before they will sell you their injectors.  If you don't ned them, they will tell you as much.  GAMIs are by no means a must to run LOP, far from it. 

Now as far as Lycoming's motives go, well yes, they sell engines and cylinders.  Why would they want to promote something that extends the life of one of their components.  Furthermore, why would they want to promote something that would require them to fix their broken induction systems that work fine if you operate only on the rich side of peak?  Now, call Lycoming and ask them to sell you a new cylinder.  They'll sell you one whether you need it or not.

If it's motive that's the deciding factor, the advantage is certainly on GAMIs side!

As far as independent organizations verifying GAMIs claim, I guess if the millions of LOP flight hours the airlines amassed during their piston engine days won't do it for you, nothing will.  George, Walter, and John didn't invent this stuff.  It's been around for years.  They just uncovered it and wondered why it wasn't still done that way.  Boy, did they open a can of worms.

[GeorgePerry]

Greg...I get it.  You’re convinced that this IS the way to run an engine and there's no telling you otherwise...that's fine. 

If your a proponent of LOP, rather than taking an unproductive adversarial tone, you should present an unemotional case substantiated with facts.  My point is that if the LOP information is so readily available, convincing and factual, why hasn't it been posted for all to read.  It seems to me that most if not all LOP info out there is word of mouth and/or posted by business that may have something to gain. 

If you can show me an article or study by AOPA or another independant aviation organization that proves the benefits I'll be the first to put the mixture in the "smarterr, better, cheaper" side of peak

 

[Cruiser]

Quote: GeorgePerry

Until a "reputable" unbiased orgainization does a comprehensive study that validates the merits of LOP, I'll stick with the factory recommendations and take my chances

[TurboExec]

Quote: GeorgePerry

My point is that if the LOP information is so readily available, convincing and factual, why hasn't it been posted for all to read.  It seems to me that most if not all LOP info out there is word of mouth and/or posted by business that may have something to gain. 

If you can show me an article or study by AOPA or another independant aviation organization that proves the benefits I'll be the first to put the mixture in the "smarterr, better, cheaper" side of peak

 

[KSMooniac]

Tom Horne recently had a very favorable column in AOPA about LOP ops as well as Aviation Consumer.  Go read those two pieces, then read all of free Deakin columns on Avweb.  If you want more of the debate with a lot of the data, go search on the AOPA Forum as well...this topic comes up very regularly and there is a lot of the data, science and logic already posted over there, but you'll have to wade through a lot of crap to find it.

At the end of the day, the APS course is the most efficient way to learn all you need to know about engine management, for either ROP or LOP operations.  There are times for both, and it is worth the effort to learn *why* that is...

[Greg_D]

Quote: GeorgePerry

If your a proponent of LOP, rather than taking an unproductive adversarial tone, you should present an unemotional case substantiated with facts.  My point is that if the LOP information is so readily available, convincing and factual, why hasn't it been posted for all to read.  It seems to me that most if not all LOP info out there is word of mouth and/or posted by business that may have something to gain. 

 

 

[Cruiser]

It is not a matter of keeping temperatures "within limits". It is more of how to operate the engine and get the most performance with the least amount of stress. It has been proven that CHTs and valve temperatures are lower LOP than they are ROP. More importantly the ICP (internal cylinder pressure) is also lower.

It has been said that exhaust valve life is more dependent on the precision of machining the seat face and alignment of the guide than ANY other factor(s). Since there has to be clearance between the valve stem and guide the valve "wobbles" on every stroke. This "wobble" allows the valve to contact the seat slightly crooked. The "wobbling" thousands of times a minute puts stress on the valve and seat. If severe enough a burn spot will develop. The owner/operator wonders what did I do wrong when there was really nothing the owner/operator could have done to prevent this. This process has been found to accelerate the higher the operating temperatures (of the exhaust valve). Above 475°F CHT this could be a matter of minutes.

[Cruiser]

So, based on the above post. You say, "Oh my, peak EGT must be worst place to operate". Actually no. Remember, it is the temperature of the exhaust valve we are concerned with, not the EGT. If you look at an engine power chart you will see the cylinder head temerature actually peaks about 50°F ROP (this would be the absolute worst place to operate your engine if you are concerned about valves) and starts to drop (much more rapidly) by peak EGT and continues to drop LOP. Tests show the exhaust valve temperature to be >5% lower LOP than they are at the same ROP setting. I.E. vavle temperatures at 50°F LOP are more than 5% cooler than valve temperatures at 50°F ROP 

Finally, that pesky ICP is much less LOP than it is ROP at the same temperatures from peak. Would you rather have the effect of pounding the top of your piston with a sledge hammer or tapping it with tack hammer?

[GeorgePerry]

I think this horse is dead...we've beat it until our arms are tired.  To each is own, education is always a good thing as are a variety of opinions.

[TurboExec]

Quote: JimR

I have a question for you LOP operators. Is long engine life entirely a function of keeping CHTs and oil temperature within limits? Are my exhaust valves going to suffer from lack of lubrication by running peak EGT or LOP? Thanks, guys. I'm learning.

[Greg_D]

Quote: GeorgePerry

I think this horse is dead...we've beat it until our arms are tired.  To each is own, education is always a good thing as are a variety of opinions.

[Greg_D]

Quote: JimR

I was trying to get at the idea that I have heard before that unburned fuel cools exhaust valves when running ROP.  Is this issue addressed by the APS folks? 

[KSMooniac]

Jim, unburned fuel most definitely does not cool anything when ROP.  It is another old wives tale that comes from the observation that enrichening the mixture (when ROP) results in cooler EGTs, so folks erroneously conclude that extra fuel must "cool" things.  Wrong!  All the extra fuel does is slow down the combustion event within the cylinder (just like extra air) and the result is lower EGTs.

Also, EGT =/= exhaust valve temperature.  Actual valve temps will track closer to CHTs than EGTs....think about it for a second.  The valve & seat are fit into the cylinder head, and all of the heat of the valve goes to the seat and then the head via conduction through the solid material.  The heat from combustion is whooshing past the valve and transferred via conduction from the gaseous mixture to the solid, which is much less efficient than through the solid contact.  By maintaining a lower CHT, you'll have lower valve temps since the heat will be more apt to conduct away from the valves due to the great temperature difference of the cylinder head.

Also, in your experiments, when going LOP you should be using your *richest* cylinder for your reference, not the leanest as you do when ROP.  Remember than 40 dF ROP is the worst place to be...so run your last cylinder to peak at PEAK (or LOP) and see where the others are...  Mooney's recommendation for 25 ROP is absolutely horrid!