Shock cooling on descent

[DaV8or]

If shock cooling is such an OWT, then why are there so many cracked engines out there? Why are there companies specializing in welding up cracked engines? What causes these cracks? Just bad luck?

[rogerl]

Quote: allsmiles

What do you want Lycoming to come up with?  They developed and gave us a bulletproof engine for our Mooneys!! If we follow some of their simple directions and give it half a chance it will go well beyond TBO!!   What did the other talking heads and "engine experts" come up with? Did they come up with something that I missed?   

[PTK]

I don't mean to be barking I'm only saying that it is frustrating to see how people will complicate something very simple. Just follow these simple instructions from Lycoming recommendations:

Descent

Plan ahead  to  make a  smooth temperature  transition between cruise  and  descent. Start  descent early and  allow airspeed  to increase  within  aircraft limits. Maintain power  asrequired and mixture setting. Cylinder head temperature change rate  should  not exceed  50°F per  minute  to avoid  rapid  shock cooling. Spoilers may be used if so equipped.

Whenever the mixture is adjusted, rich or lean, it should be done slowly. At all times, caution must be taken not to shock cool the  cylinders. The  maximum recommended  temperature change should not exceed 50°F per minute.

Does'mt this sound LOGICAL? What's the problem? Why do some people want to do something different?  Is it because Lycoming recommends it and they want to go against it?  I don't get it!

 

[rogerl]

Quote: allsmiles

I don't mean to be barking I'm only saying that it is frustrating to see how people will complicate something very simple. Just follow these simple instructions from Lycoming recommendations:

Descent

Plan ahead  to  make a  smooth temperature  transition between cruise  and  descent. Start  descent early and  allow airspeed  to increase  within  aircraft limits. Maintain power  asrequired and mixture setting. Cylinder head temperature change rate  should  not exceed  50°F per  minute  to avoid  rapid  shock cooling. Spoilers may be used if so equipped.

 

Whenever the mixture is adjusted, rich or lean, it should be done slowly. At all times, caution must be taken not to shock cool the  cylinders. The  maximum recommended  temperature change should not exceed 50°F per minute.

 

Does'mt this sound LOGICAL? What's the problem? Why do some people want to do something different?  Is it because Lycoming recommends it and they want to go against it?  I don't get it!

 

[John Pleisse]

I think shock cooling can more easily occur practicing engine-outs in the winter time than it can normal ops out of 12k. Shock is the operative word, the rapidity of the cooling. I have flown two engines a thousand hours in my 201 and it is just not an issue. Leave a little power in and keep an eye on things. Turbo? A whole other, completely different deal.

[PTK]

It's a similar frenzy when it comes to lop vs rop.  Lycoming never said we can't run our engines lop. They clearly recommend running AT PEAK, at the beginning of the best economy range.  They attempt to safeguard us from destroying our perfectly good engines!  Mixture control is the key which is not understood by most of us. I'm still learning this myself.  Sure lop will save some gas but do we really care? What is this difference in our little engine, half a gallon an hour?  Not only does Lycoming try to help us but it is the margins they engineered into our engines that saves a lot of us! 

[Shadrach]

Quote: allsmiles

Uhh... guys, Lycoming manufactures the engine and Lycoming honors the warranty. I would listen to Lycoming!!  Anyone can say whtever they want but they are not responsible or liable.  Use common sense and LISTEN to Lycoming.  Do not discount the voice of experience over some "wannabes" out there who talk without any substance.  

[Shadrach]

Quote: DaV8or

If shock cooling is such an OWT, then why are there so many cracked engines out there? Why are there companies specializing in welding up cracked engines? What causes these cracks? Just bad luck?

[Shadrach]

Quote: allsmiles

It's a similar frenzy when it comes to lop vs rop.  Lycoming never said we can't run our engines lop. They clearly recommend running AT PEAK, at the beginning of the best economy range.  They attempt to safeguard us from destroying our perfectly good engines!  Mixture control is the key which is not understood by most of us. I'm still learning this myself.  Sure lop will save some gas but do we really care? What is this difference in our little engine, half a gallon an hour?  Not only does Lycoming try to help us but it is the margins they engineered into our engines that saves a lot of us! 

[PTK]

Looks like Ross is very passionate about shock cooling!  Maybe you need to be shock cooled Ross!!  You said it yourself.  Your engine has not been touched by Lycoming since the 1960's. I don't know how true that is but why would they need to touch it. It's a bulletproof engine!!  Your wannabes you so very passionatly carry water for, have they come up with a better engine??  What do they do?  they talk about lop rop etc etc as if it's a new concept!  Lindbergh did this when he crossed the Atlantic Ross!!  Lycoming does this all day long in a CONTROLLED well instrumented environment.  I know I've seen it! The issue is that not every pilot out there is capable of operating their engine in this narrow performance envelope.  I will listen to Lycoming each and every day before I listen to any talking head out there who claims he knows best!   Chill out Ross!!

[PTK]

[Parker_Woodruff]

Quote: allsmiles

I did not say it is dangerous to run lop.  I assume we are talking about normally aspirated.  What I said was that the loss of power and performance is so great, ofcourse you see lower fuel burn.  In our little engines half or one gph difference is not worth the risk.  

But you are right this is not a lop rop debate!

[Shadrach]

Quote: allsmiles

Looks like Ross is very passionate about shock cooling!  Maybe you need to be shock cooled Ross!!  You said it yourself.  Your engine has not been touched by Lycoming since the 1960's. I don't know how true that is but why would they need to touch it. It's a bulletproof engine!!  Your wannabes you so very passionatly carry water for, have they come up with a better engine??  What do they do?  they talk about lop rop etc etc as if it's a new concept!  Lindbergh did this when he crossed the Atlantic Ross!!  Lycoming does this all day long in a CONTROLLED well instrumented environment.  I know I've seen it! The issue is that not every pilot out there is capable of operating their engine in this narrow performance envelope.  I will listen to Lycoming each and every day before I listen to any talking head out there who claims he knows best!   Chill out Ross!!

[Shadrach]

[Shadrach]

[Shadrach]

God this software is weird... Posts disappear and other times show up in threes... Plus my spellcheck seems incapable of interacting with it... Oh well, sorry for the repeats...

[carusoam]

My CHTs while running LOP are often in the 280 - 320 range. 

I always wonder how much of an issue it is when flying through heavy rain. 

Isn't that like pouring a hose on hot metal.  I would think a metalurgist would vote against the practice of flying in rain.

Best regards,

-a-

 

 

[jlunseth]

  Which of the firms that I named are wannabes w/out substance.

 

Well, I for one am a strong believer in what the GAMI group puts out, because I have been there, attended the seminar, and seen an engine run on the test bed.  They apply good science.  But I do have to object a little to the argument that "these firms" all contradict Lycoming.  Tornado Alley, GAMI, and Advanced Pilot Seminars are all one group of companies, owned and operated by the same relatively small group of people in Ada.  That does not mean their science is wrong science, I happen to think they are right about most things.  But there are also some weaknesses to it.  For example, most of their work is on Bonanzas, and the turbo Bonanzas are "big bore" engines.  The theory maybe applies to our "small bore" Mooney turbos such as the TSIO-360, but not the practice.  The small bore turbos are just plain difficult to set up to run LOP.

Another weakness is that GAMI is in Ada, OK, where it is warm compared to my home, Minnesota.  They don't need to worry about chopping the throttle when the temps are -20 dF, but I do.  Most good pilots here in Minnesota do take care with their engines in the winter, in the summer not so much.

I don't mean to be picking an argument here, a good pilot just needs to use common sense and learn about his/her engine, as much as they can.  And not take anyone's word for it that a technique is right or not right without a little analytical skepticism, even if they are as smart as George Braley. 

I have noticed (cause I have a display that shows degrees of cooling), that I can take care to keep the engine warm for 100 miles in a descent from cruise, but then in the last two miles of final when the throttle needs to be reduced into the 15-17" range, that display gets very cold very fast.  Engine does not seem to mind too much cause it has already come down from 350 to maybe the high 200's. 

[Shadrach]

Quote: jlunseth

[trey2398]

[John Pleisse]

I gotta tell you..........LOP v. ROP seems to insidously creep it's way into every engine disussion. Do it in a Continental, save a gallon or two and do a top at 850 hrs. Fly Lycoming cylinders 150 ROP to TBO...end of discussion. Lycoming presribes no LOP Ops.

M20 Turbos is the only IO360 Turbo STC currently available for purchase..... and conspicously, I hear the old lady and son have the company on the block. Think Tornado Alley might swoop them up?

[scottfromiowa]

So Trey, has shock cooling been defined for you?  I'm so glad you asked.  Looking forward to LOP vs. ROP debate...again.  A.W.E.S.O.M.E...

[MooneyMitch]

Ok, I hate to beat a dead horse with a stick.............   Anyway, I just could not resist in helping to continue to hijack this thread, so here goes!

"LOP v. ROP seems to insidously creep it's way into every engine disussion. Do it in a Continental, save a gallon or two and do a top at 850 hrs."

I have a Continental IO-500G, 1500+ hours, that has ALWAYS run 50 LOP.  No cyl. work yet, but I'm sure I will as things just do wear out eventually. 

I do apologize!  

[trey2398]

Ha...  So the answer is 50 degrees/minute.  Got it...thnx.  Sorry for starting all this...

[KSMooniac]

Quote: N4352H

I gotta tell you..........LOP v. ROP seems to insidously creep it's way into every engine disussion. Do it in a Continental, save a gallon or two and do a top at 850 hrs. Fly Lycoming cylinders 150 ROP to TBO...end of discussion. Lycoming presribes no LOP Ops.