P-Navajo

USMCmech said:
No, on many ocasions they continue in destructive and/or unessacary practices. Despite Amflight's years of experiance, they have not equiped their airplanes with modern accurate instrumentation.
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That single-point CHT probe that hasn't been calibrated since the airplane left the factory is plenty accurate to ensure that you're not frying cylinders.
:sarcasm:

It's astounding what a difference there is in CHT among cylinders on one engine, especially one that doesn't have balanced flow injectors.

Aaaand there are lots of good ol' boys out there who INSIST they know the best way to baby the engine...and the CHT shows a different story.
 
USMCmech said:
No, on many ocasions they continue in destructive and/or unessacary practices. Despite Amflight's years of experiance, they have not equiped their airplanes with modern accurate instrumentation.


Everything I've seen has convinced me that you can't "shock cool" an airplane engine without deliberate and repeated abuse. This is backed up by several enginering studies by universities like Texas A&M.

The main problem with these engines is that they sit unflown for far too long, and when they are flown they are run too hot. If you keep your engines "cool" (under 350 CHT), then you don't need to worry about "shock cooling".
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I'll be honest, I don't remember the CHT we flew at, but the current Amflight Chieftain drivers could tell you what Bob's current idea of an ideal CHT is.

I'd say the blown engines they had lying around were proof enough, but believe whatever you want. I just did what the boss told me to do, and largely trusted the MX guys.
 
So just to be clear, A&M decided that it was not possible to shock cool the engines? As long as they're running and have some amount of power on them? Any link to the summary of the research?
 
PetrolBurner said:
So just to be clear, A&M decided that it was not possible to shock cool the engines? As long as they're running and have some amount of power on them? Any link to the summary of the research?
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It is "possible" to damage an engine by thermal cycling (AKA shock cooling). However the steps required to change CHT that fast are well outside what any sane pilot would ever do in an airplane. The manufactures recomend a limit of 50deg per minute. Anybody that is flying point A - B, and reducing 5" to produce a 500FPM constant airspeed descent is nowhere near that.

The 100% best thing to do is never let your engine get that hot in the first place, keep the CHTs in the 350 range. If your engine is already cool, then you have nothing to worry about. Make sure you use a CHT guage that shows each cylinder, as there can be a big difference #1 may be fine at 350, but #4 could be 420.
 
Poopsmith said:
PT-A28 at 620hp (Cheyenne 1)

Talked to the previous pilots and here is the info:

50 gph for planning pourposes
Engines are 1200 TBO and do not liked to be idled lower than 800rpm on the ground.

Profiles:
Takeoff - 2400rpm / 44"
Climb - 2000rpm / 40" Vy
Cruise - 1600rpm / 36"-38" (settings per power table)

Stage cool about 1" per 1000ft drop
Good idea to put the approach flaps down, or you'll never slow down. You can put them down at 180. Gear at 150 if you need.

Pattern - 2000rpm 23" or 24"

Annuals are from $6000 to $20,000 depending on what is broken. 60hrs minimum of shop time. Engine remanufacture is around $70K.

Pilots said be smoov on the throttles, this is where most problems occur. has to do with the counter-weights.

Descents are not a big issue, you will be going fast, so more planning ahead. You really can't have the power out most of the way since the higher wing loading requires some power to keep the descent reasonable.

Pretty much it, i'll post more if i missed something.
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Careful now. Everyone knows that oversquare is baaaad.
 
USMCmech said:
It is "possible" to damage an engine by thermal cycling (AKA shock cooling). However the steps required to change CHT that fast are well outside what any sane pilot would ever do in an airplane. The manufactures recomend a limit of 50deg per minute. Anybody that is flying point A - B, and reducing 5" to produce a 500FPM constant airspeed descent is nowhere near that.

The 100% best thing to do is never let your engine get that hot in the first place, keep the CHTs in the 350 range. If your engine is already cool, then you have nothing to worry about. Make sure you use a CHT guage that shows each cylinder, as there can be a big difference #1 may be fine at 350, but #4 could be 420.
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That's never been debated.

But some people seem to think it's a-ok to take a TIO-540 that's been cruising at 30" of MP and 380 degree's of CHT for 2 hours and then reduce power to 16" of MP in one fell swoop. Will it blow your cylinder heads off? No, nobody has ever made that argument and if they have then they need to remove their heads from their butts; but doing so will destroy your engine over a 1,000 hour period of continued abuse.
 
jtrain609 said:
Also consider how fast you're moving in the descent. If I remember correctly, you need around 30nm of real estate to go from 9,000' to 2,500' MSL, and that's only going from 26" in cruise power to 18"-20" on approach.
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It's even worse if you have to worry about passenger comfort. With a nice tailwind descending from 10,000 to sea level, you need 70+ miles to make the descent at 500fpm at a high enough power setting to keep the engines warm. :insane:
 
dasleben said:
It's even worse if you have to worry about passenger comfort. With a nice tailwind descending from 10,000 to sea level, you need 70+ miles to make the descent at 500fpm at a high enough power setting to keep the engines warm. :insane:
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In a Chieftain while stage cooling at 2" every 2 minutes you have to start around 26nm from the FAF in order to be slowed down enough for the approach. Generally that would net you 180 knots indicated and a 1,000 FPM descent.

If you do your math right it works like clockwork.
 
jtrain609 said:
In a Chieftain while stage cooling at 2" every 2 minutes you have to start around 26nm from the FAF in order to be slowed down enough for the approach. Generally that would net you 180 knots indicated and a 1,000 FPM descent.

If you do your math right it works like clockwork.
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Slow? Approach? 180 to the marker, son. Mocha hagotdi. :D
 
HA! We couldn't pop the gear until 125 knots, so we kept the redline to the marker business for the turboprops in the fleet.

Quite frankly the EMB-145XR is worlds ahead of any large piston twin as far as speed flexibility goes, but you knew that :)
 
jtrain609 said:
But some people seem to think it's a-ok to take a TIO-540 that's been cruising at 30" of MP and 380 degree's of CHT for 2 hours and then reduce power to 16" of MP in one fell swoop. .....but doing so will destroy your engine over a 1,000 hour period of continued abuse.
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That would be my definition of "deliberate and repeated abuse".

However many pilots do act like doing that even one time will cause their cylinders to shatter like glass.
 
jtrain609 said:
HA! We couldn't pop the gear until 125 knots, so we kept the redline to the marker business for the turboprops in the fleet.

Quite frankly the EMB-145XR is worlds ahead of any large piston twin as far as speed flexibility goes, but you knew that :)
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Yeah, Cessna did it right: Flaps 15 and gear can come out at 180 KIAS on the 402. Pretty easy to just throw everything out. It can sometimes be hard to get it slowed below 149 for flaps 30 and 45 if there's a tailwind or we're carrying a bit of a load, but you just pick the nose up a little and make it work.

Loves me some XR. 250 to the marker, mmmm.
 
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