Shock Cooling - Myth Busted!!
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Pretty much same aerodynamics with cross controls.
Forward slip maintains track (so is used for altitude loss only)
Side slip deviates track and maintains heading (think maintaining centreline when landing with crosswind)
Or we'll just say "slip" and keep everyone happy.
Forward slip maintains track (so is used for altitude loss only)
Side slip deviates track and maintains heading (think maintaining centreline when landing with crosswind)
Or we'll just say "slip" and keep everyone happy.
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T28D
I dont think this is thread drift at all. It fits nicely in the thread. Issues of radial handling are for specific reasons, none of which are scientifically based on cooling. Very scientifically based on reverse loads.
The correct handling you refer to is most likely ....careful descents = crank/gearcase and careful climbs = 170 (340F) and cruise = 150 (300-310F) This clearly not shock heating
This is closely aligned with reality and the opinion of some folk i know who are regarded the experts. You can beat engine temps like those you are talking about.
The mid sized radials are generally in the 1500 H.P. area so their thermal loads are significant, but with good disciplined handling they are a really reliable power plant.
the1820 cyl head temp runs 170 celciusin the climb cowls open and 150 celcius in cruise cowls closed, very benign temps.
the1820 cyl head temp runs 170 celciusin the climb cowls open and 150 celcius in cruise cowls closed, very benign temps.
The correct handling you refer to is most likely ....careful descents = crank/gearcase and careful climbs = 170 (340F) and cruise = 150 (300-310F) This clearly not shock heating
This is closely aligned with reality and the opinion of some folk i know who are regarded the experts. You can beat engine temps like those you are talking about.
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Keh ??
Pretty much same aerodynamics with cross controls.
Forward slip maintains track (so is used for altitude loss only)
Side slip deviates track and maintains heading (think maintaining centreline when landing with crosswind)
Or we'll just say "slip" and keep everyone happy.
Forward slip maintains track (so is used for altitude loss only)
Side slip deviates track and maintains heading (think maintaining centreline when landing with crosswind)
Or we'll just say "slip" and keep everyone happy.
Last edited by jas24zzk; 5th Sep 2012 at 10:13.
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I'm interested in your reply to Arnold E
You haven't thought it through very well have you...in the meantime, risking a hijack of a quality thread
You haven't thought it through very well have you...in the meantime, risking a hijack of a quality thread
Last edited by jas24zzk; 5th Sep 2012 at 12:53.
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Thebit where inexperienced folk are all "crossed up "and yet still in control, no mention of flap position, manifold pressuer ( power being developed) or what the POH says.
Yup it can be done, but I simply say WHY would you introduce a student to the edge of incipient spin on final, seems a bit silly and full of machismo bravado to me.
What ever happened to the stabilised approach ?????? from which the kiss the ground arrival is possible.
Test pilots all be aware your jobs are being threatened by newby's getting all crossed up on final and hopefully living to tell the tale.
Sheesh.
Yup it can be done, but I simply say WHY would you introduce a student to the edge of incipient spin on final, seems a bit silly and full of machismo bravado to me.
What ever happened to the stabilised approach ?????? from which the kiss the ground arrival is possible.
Test pilots all be aware your jobs are being threatened by newby's getting all crossed up on final and hopefully living to tell the tale.
Sheesh.
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Forward Slip
The forward slip is performed just like the turning slip, but the heading remains constant. Its purpose is to lose altitude without a corresponding increase in airspeed, which would be the case if you simply pushed forward on the yoke.
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On final, slips are great. Ignoring crosswinds, ever had a short field with obstacles to land in? Ever tried a landing on the keys consistently every time? Munch your popcorn away.
Putting this thread back on topic:
Regarding this thread and forward slips, I am interested in any readings on a prolonged slip to rapidly reduce altitude without yellow arc airspeed increases and what the EGT/CHT/MP changes result. I do not having the sophisticated monitoring equipment to measure this.
I am interested in this approach versus the original poster's "point the nose down and pull the power"@2000FPM descent for 6 minutes.
Putting this thread back on topic:
Regarding this thread and forward slips, I am interested in any readings on a prolonged slip to rapidly reduce altitude without yellow arc airspeed increases and what the EGT/CHT/MP changes result. I do not having the sophisticated monitoring equipment to measure this.
I am interested in this approach versus the original poster's "point the nose down and pull the power"@2000FPM descent for 6 minutes.
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Continuing on from the radial myths, if you can't rotate the engine with the prop then how do they use reverse on radials without the load being reversed? Albatross have 1820's and reversing props, do they have a different gearbox to cope with the reversed loads? What about R2000's on DC 4's and Caribou's they reverse them, do they have to change gearbox's after every reverse landing?
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Shock Cooling - Myth Busted!!
Lycoming Service Instructions link
One of those 'Instructions' is SI-1094D Fuel Mixture Leaning Procedures (pdf file) dated March 25, 1994 (still current)
What does Lycoming define as 'Shock Cooling'?
Only pointing out the current recommendations of the manufacturer.
Myth Busted?
I don't think so.
Lycoming Service Instructions link
One of those 'Instructions' is SI-1094D Fuel Mixture Leaning Procedures (pdf file) dated March 25, 1994 (still current)
Revision "D" to Service Instruction on No. 1094 supersedes all previous recommendations and should be used for engine leaning during normal flight operations. ALL LEANING RECOMMENDATIONS ARE BASED ON CALIBRATED INSTRUMENTATION.
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.
Myth Busted?
I don't think so.
Last edited by Trent 972; 7th Sep 2012 at 05:47. Reason: remove TEXTRON LYCOMING DOES NOT RECOMMEND OPERATING ON THE LEAN SIDE OF PEAK EGT. from post
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Jaba, special note to you. In no way do I want you to think I'm having a shot at you. I just don't agree that the myth is busted, by way of that data set.
Not to worry though, according to the data graph you provided in the OP, the max 'cooling' Delta T indicated is 41°F/min, oddly enough, as you reduced the fuel flow after TOC @13.42.39.
Not to worry though, according to the data graph you provided in the OP, the max 'cooling' Delta T indicated is 41°F/min, oddly enough, as you reduced the fuel flow after TOC @13.42.39.
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that document is from 1994, almost 20 years ago and right in the thick of many OWT's bouncing around the manuals of TCM and LYC. I would be very concerned at believing much that was printed in that document. Some may be good, some not.
I love point 2. Mixture changes should be done slowly!
You are kidding me right, they say that but do not quantify it 
Let me give you a tip, and I am not sure I know which data point you are referring to but I use the BMP (Big Mixture Pull) and then sneak up from the lean side. Some times I don't, just because I lik observing the data. And I would guess the 42dF/min was from a BMP. Heck that is shock cooling at its best, and it is still 20% less than Lycomings suggested 50F/min.
If that there is not enough proof the myth is busted, I do not know what is.
By the way I just went and looked at the raw data file, 42F/min......not that I can find, I see just after TOC and a massive fuel flow drop, the fastest was 32dF per minute. Maybe there was one cylinder that was closer to 40, but whoopee!
I still maintain, the only shock cooling likely is when you spear into a lake/ocean.
George Braly, who has done more testing than anyone I know, took my data set and graphed it far better...... he was chomping at the bit to get it, and he was not surprised.
Seriously, as John Deakin has written before, maybe you can cook an engine to 475-500F and dive like a rock with no power, and maybe just maybe you can create cooling bad enough. But who actually does that. The data proves that it is climbs that create the bigger Delta T and in combination with high ICP.
If I have to repeat the above again...........clearly I am wasting my time. OK one last time Delta T and ICP.
Shock Cooling = Myth Busted! Even more so!
that document is from 1994, almost 20 years ago and right in the thick of many OWT's bouncing around the manuals of TCM and LYC. I would be very concerned at believing much that was printed in that document. Some may be good, some not.
I love point 2. Mixture changes should be done slowly!
You are kidding me right, they say that but do not quantify it Let me give you a tip, and I am not sure I know which data point you are referring to but I use the BMP (Big Mixture Pull) and then sneak up from the lean side. Some times I don't, just because I lik observing the data. And I would guess the 42dF/min was from a BMP. Heck that is shock cooling at its best, and it is still 20% less than Lycomings suggested 50F/min.If that there is not enough proof the myth is busted, I do not know what is.
By the way I just went and looked at the raw data file, 42F/min......not that I can find, I see just after TOC and a massive fuel flow drop, the fastest was 32dF per minute. Maybe there was one cylinder that was closer to 40, but whoopee!
I still maintain, the only shock cooling likely is when you spear into a lake/ocean.
George Braly, who has done more testing than anyone I know, took my data set and graphed it far better...... he was chomping at the bit to get it, and he was not surprised.
Seriously, as John Deakin has written before, maybe you can cook an engine to 475-500F and dive like a rock with no power, and maybe just maybe you can create cooling bad enough. But who actually does that. The data proves that it is climbs that create the bigger Delta T and in combination with high ICP.
If I have to repeat the above again...........clearly I am wasting my time. OK one last time
Delta T and ICP.Shock Cooling = Myth Busted! Even more so!
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I can't help myself.......really have a read of this would you
Now think about this one carefully folks. You can have 70% power in two ways. And best power is at 75dF ROP, so as they suggest for a given power setting, lets look at this.
Say the given power setting is 70% power. Lycoming correctly state that the best power is where you get the fastest speed. However you can achieve a "Given Setting" in this case 70% power or any other for that matter, by a ROP setting, which 75ROP is, or a 25LOP setting. Or the same power at 150ROP.
Which one of these same power settings, same IAS same performance out the prop has the;
a: Coolest CHT
b: lowest Fuel Flow
c: lower ICP
d: Least engine wear and deposits?
So choose answers 1=75ROP , 2=25LOP or 3=150ROP
And you wonder why I laugh at the tech bulletins written by the "Manufacturers"
So please folks, in all good spirits of education have a crack at answering the above, and in a day or so I will do my best to explain the correct answers. I expect most of the local folk here will know the right stuff, but it is a fun education exercise all the same.
The better manuals are really old, produced by P&W and Curtis Wright. The crap printed by TCM and Lyc in the "dark ages" is pure fiction and often comedy. I have many examples in a folder beside my bed (sad hey), but after many a pprune thread I look them up just to be sure I am criticising them properly.
The problem here is 100% of students never get a chance to reason with this stuff.
You know what makes me mad, my wife has been doing some aviation subjects as part of her business degree. Last exam she received 20% of the marks for the exam by answering with completely wrong answers. Yes she deliberately answered them wrong knowing that is what the text books (CPL) preach. If I posted them here 75% of the prune community would recognise them as BS. But the industry, CASA and FAA etc keep churning this crap out.
Rant Off!!!!!!
For cruise powers where best power mixture operation is allowed, slowly lean the mixture from full rich to maximum power. Best power mixture operation provides the most miles per hour for a given power setting. For engines equipped with fixed pitch propellers, gradually lean the mixture until either the tachometer or the airspeed indicator reading peaks. For engines equipped with controllable pitch propellers, lean until a slight increase of airspeed is noted.
Say the given power setting is 70% power. Lycoming correctly state that the best power is where you get the fastest speed. However you can achieve a "Given Setting" in this case 70% power or any other for that matter, by a ROP setting, which 75ROP is, or a 25LOP setting. Or the same power at 150ROP.
Which one of these same power settings, same IAS same performance out the prop has the;
a: Coolest CHT
b: lowest Fuel Flow
c: lower ICP
d: Least engine wear and deposits?
So choose answers 1=75ROP , 2=25LOP or 3=150ROP
And you wonder why I laugh at the tech bulletins written by the "Manufacturers"
So please folks, in all good spirits of education have a crack at answering the above, and in a day or so I will do my best to explain the correct answers. I expect most of the local folk here will know the right stuff, but it is a fun education exercise all the same.
The better manuals are really old, produced by P&W and Curtis Wright. The crap printed by TCM and Lyc in the "dark ages" is pure fiction and often comedy. I have many examples in a folder beside my bed (sad hey), but after many a pprune thread I look them up just to be sure I am criticising them properly.
The problem here is 100% of students never get a chance to reason with this stuff.
You know what makes me mad, my wife has been doing some aviation subjects as part of her business degree. Last exam she received 20% of the marks for the exam by answering with completely wrong answers. Yes she deliberately answered them wrong knowing that is what the text books (CPL) preach. If I posted them here 75% of the prune community would recognise them as BS. But the industry, CASA and FAA etc keep churning this crap out.
Rant Off!!!!!!
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The big radials do ( mixture ) automatically, absolutely dependent on altitude, throttle position, Carby Temp, and where the diaphragm puts it !!!!!!!!
Generally bloody accurate, thank god for pressure carburetors ( throttle bodies in moder vernacular ).
After flight look at the exhaust colour soft grey = good black = too rich white = too lean
It is not rocket science.
For once I am with Jabawocky, the most common problem in the weekend warrior ranks is engine handling ,closely followed by bloody big circuit patterns.
See probably thread drift , now we start on Actual "SideSlipping " as opposed to Forward slipping what ever that is ??????
Generally bloody accurate, thank god for pressure carburetors ( throttle bodies in moder vernacular ).
After flight look at the exhaust colour soft grey = good black = too rich white = too lean
It is not rocket science.
For once I am with Jabawocky, the most common problem in the weekend warrior ranks is engine handling ,closely followed by bloody big circuit patterns.
See probably thread drift , now we start on Actual "SideSlipping " as opposed to Forward slipping what ever that is ??????
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You make a claim of "Shock Cooling - Myth Busted" and provide the data that shows, even without trying, your engine operating technique at one point in time on one engine cylinder (#4), cooled momentarily at a rate of 82% of the recommended OEM maximum.
That being the case, I am sure that it would be very easy for a 'Ham Fisted' effort to achieve a Delta T far greater than 50°F/min.
I'm sorry that you think that you are wasting your time.
As far as questioning the value of the OEM recommendations, perhaps a more recent example from a POH of a 2009 PA46 TIO540 AE2A might show that there has been no change since SI-1094D
OEM says one thing and Jaba says differently, as we have said before, 'each to their own'.... myth busted... I call bullish!t. 
ps. waiting for Clinton to come on now and tell me all about how the greatest rate of cooling occurs after shutdown (short of using a garden hose to cool it).
I already have the links prepared to show that as blatantly false.
That being the case, I am sure that it would be very easy for a 'Ham Fisted' effort to achieve a Delta T far greater than 50°F/min.
I'm sorry that you think that you are wasting your time.
As far as questioning the value of the OEM recommendations, perhaps a more recent example from a POH of a 2009 PA46 TIO540 AE2A might show that there has been no change since SI-1094D
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 and mixture setting as required. Cylinder head temperature change rate is not to exceed 50°F per minute to avoid rapid shock cooling.
ps. waiting for Clinton to come on now and tell me all about how the greatest rate of cooling occurs after shutdown (short of using a garden hose to cool it).
I already have the links prepared to show that as blatantly false.
Last edited by Trent 972; 7th Sep 2012 at 11:58. Reason: typo
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the most common problem in the weekend warrior ranks is engine handling ,closely followed by bloody big circuit patterns.
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Sorry Jaba, I missed your and T28's last post while I was typing.
What was that in your quote box in previous post.... Ah yes
How does that fit in with your BMP (Big Mixture Pull)? 
What was that in your quote box in previous post.... Ah yes
......slowly lean the mixture from full rich to maximum power
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Apologies for being too noisy on this thread but I think Jaba and others might enjoy this from the PA46 POH.
operating on the lean side of peak TIT with elevated manifold pressure substantially reduces or may entirely eliminate the detonation margin. It is certainly not a procedure that is operator friendly to be used in today’s environment with high ATC (Aircraft Traffic Control) attention and traffic demands. The cost of replacing a burned valve or piston will more than offset the small savings in fuel burn. If a $5 per hour savings in fuel is necessary for an operator to afford the use of a Mirage at the risk of engine wear or damage, this is not the correct powerplant or aircraft.