Leaning Best Practice for newbie

[jaylw314]

12 minutes ago, Bob - S50 said:

If there is even a suggestion that the air may be bumpy I leave my RPM at 2600, descend at 500 FPM and keep pulling the power to maintain 20" MP.  If that turns out to be too fast for the amount of turbulence, I'll use 15" MP instead.

Nothing wrong with that, either, the 2600 will get you down faster with more drag.  I just like the 1900 because the engine cools down slower so less risk of shock cooling, but that's probably less of an issue if you were running LOP in the first place anyway, since you're CHT's were probably already pretty cool.  It's also easier

[Bob - S50]

55 minutes ago, jaylw314 said:

Nothing wrong with that, either, the 2600 will get you down faster with more drag.  I just like the 1900 because the engine cools down slower so less risk of shock cooling, but that's probably less of an issue if you were running LOP in the first place anyway, since you're CHT's were probably already pretty cool.  It's also easier

To be honest I don't worry about shock cooling.

[gsxrpilot]

Agreeing with @Bob - S50. Shock cooling has been debunked as an OWT. It's doesn't effect our engines.

Same goes for sitting on the ramp with the prop spinning to "let the turbo cool down" - debunked.

[FastTex]

1 hour ago, Bob - S50 said:

It's all technique so you'll have to try a few things and decide what you like.  My descent plan:

If the air is smooth, just lower the nose and trim for 500 FPM rate of descent.

If there is even a suggestion that the air may be bumpy I leave my RPM at 2600, descend at 500 FPM and keep pulling the power to maintain 20" MP.  If that turns out to be too fast for the amount of turbulence, I'll use 15" MP instead.

Approaching the pattern I'll pull the power to 15", reduce RPM to about 2200 or 2300 and slow to about 100 - 110 KIAS.  At some point in the pattern my RPM will drop below my selected RPM.  That tells me the engine is not making enough power to allow the prop control to maintain RPM so I can safely push the prop control full forward.

During this entire time I never touch the mixture.  I leave it set from the time I set it for cruise until I shut down for parking.

If I have to go around I have trained myself to do the following:  cowl flaps open, mixture full rich, prop full forward, throttle full forward, positive rate, gear up, 80 KIAS, flaps up and run my electric trim nose down at the same time to compensate for the pitch change.  Then 100 KIAS, cowl flaps to trailing and climb at 100 KIAS to pattern altitude or 1000 AGL if executing an instrument missed approach.

Enjoy getting to know your airplane.

I guess it's now time for me to LOP using the JP830 procedure instead of just pulling the mixture to 8.5GPH! I kind of like that easy pull without checking graph bars and numbers while flying the airplane...do you guys think it's necessary to go through the JP830 steps?

[gsxrpilot]

9 minutes ago, FastTex said:

I guess it's now time for me to LOP using the JP830 procedure instead of just pulling the mixture to 8.5GPH! I kind of like that easy pull without checking graph bars and numbers while flying the airplane...do you guys think it's necessary to go through the JP830 steps?

No, no need to go through the steps. 

Do you know how many degrees LOP you are at 8.5 gph? To learn that would be the only reason to use Lean Find on the 830. I'll bet if you go through the whole Lean Find procedure on the 830, you'll find you arrive at exactly the same place. 

[jaylw314]

6 minutes ago, FastTex said:

I guess it's now time for me to LOP using the JP830 procedure instead of just pulling the mixture to 8.5GPH! I kind of like that easy pull without checking graph bars and numbers while flying the airplane...do you guys think it's necessary to go through the JP830 steps?

No, if anything, it encourages people to fly in the "red box" around 50 ROP longer than necessary.  While at the power settings we use in the IO-360 at cruise, this is unlikely to cause a problem, it's probably not good form to make a habit out of it

 

31 minutes ago, gsxrpilot said:

Agreeing with @Bob - S50. Shock cooling has been debunked as an OWT. It's doesn't effect our engines.

Same goes for sitting on the ramp with the prop spinning to "let the turbo cool down" - debunked.

I remember one of Mike Busch's seminars where he dismissed the risk of shock cooling, but then went on to say he sets his cooling alarm at -60^o F/min.  That's where I set my alarm, and I reduce RPM like I do to avoid setting the alarm off.  I agree it's likely to be overkill, though.

I should point out when I said "it's easier" I was referring to @Bob - S50's technique, not mine  

[gsxrpilot]

Just now, jaylw314 said:

I remember one of Mike Busch's seminars where he dismissed the risk of shock cooling, but then went on to say he sets his cooling alarm at -60^o F/min.  That's where I set my alarm, and I reduce RPM like I do to avoid setting the alarm off.  I agree it's likely to be overkill, though.

I've listened to all of Mike's seminars and am a huge fan of his. But a lot of what he says is based on his many years of experience and anecdotal evidence. It was a whole different experience attending the APS class in Ada, OK. John, Walter, and George presented hard data to back up their positions. And the engineer in me, appreciates the data and the math involved. 

I came away from that weekend class knowing that the same brain cells assigned to worrying about getting run over by Santa's reindeer could now add shock cooling to the list they're responsible for.

[FastTex]

9 minutes ago, gsxrpilot said:

No, no need to go through the steps. 

Do you know how many degrees LOP you are at 8.5 gph? To learn that would be the only reason to use Lean Find on the 830. I'll bet if you go through the whole Lean Find procedure on the 830, you'll find you arrive at exactly the same place. 

Ok, you gave me an idea. I will compare the EGTs of the two flights I have done with the "manual" LOP procedure so I can have an indication if they are pretty much the same. Next flight I made note to run a "step-by-step" procedure and then compare temps...

[Hank]

4 minutes ago, gsxrpilot said:

I came away from that weekend class knowing that the same brain cells assigned to worrying about getting run over by Santa's reindeer could now add shock cooling to the list they're responsible for.

There's a cool song about shock cooling your engine now??? Probably will be soon with the auto makers putting tiny turbo engines and zillion-gear automatics in their new models . . . .

[ArtVandelay]

If there is shock cooling, I would think it could happen when passing through cold rain as you descend (under reduced power).
The cold water cooling the heads faster than the thin air.
It would be interesting to see engine monitor data of this worst case scenario.

[201er]

5 hours ago, FastTex said:

So...this works great, THANKS! I have been doing a few flights where I quickly moved to about 8.5GPH. Everything appears to be more stable (oil temp, CHTs, etc.).

Now at what point to "revert"? For example: I like to be @pattern ALT when about 3NM from the airport. If I'm @5000' with WOT, 2400RPM and 8.5GPH how do I get to FULL PROP, MAX MIXTURE and LOW RPM/Speed and get ready to land? It might sounds like a silly question but I found myself to look for a procedure during that phase of the flight.

Two strategies for descent: leave it all where it is and take the extra speed or power back to maintain speed at a lower power setting for economy. I generally do all my flying targeting 120kias for Carson’s speed so in the descent I pull back to about 2300rpm and about 7.0gph on the mixture for around 50% power. I reduce throttle to maintain cruise mp through the descent and enrich the mixture just a little. This keeps the airframe at the most efficient for fast aerodynamics for the entire trip.

The other method of leaving it all in was previously mentioned and works well too. But it ends up being more inefficient than fast.

Another thing is start your descent really far out (assuming neutral winds) targeting 300fpm descent. This keeps parasitic drag low in the descent rather than doing a slam dunk.

[Bravoman]

The concept of shock cooling sounds plausible for a turbocharged engine. I think with proper use of speed brakes the chance of it happening is slight.

[carusoam]

Some PP thoughts to add....

So much oil flow through the TC is used for temp control, shock cooling from the outside with a low throttle setting is going to be tough to come by...

Short cutting the LOP settings using FF is OK, sort of... taking this short cut leaves power on the table when you want it, or leaves efficiency on the table when you need it...  how much? Do the math with your own plane...

• It depends on altitude
• FF gets you in the ball park, setting it with precision is a 30second deal after that...
• @10k’ using an NA engine, I want to get 100% out of the fuel i’m Burning, and max power to go with that... so setting the %bhp using FF the same way every time is OK... like training in a Cessna is OK...  
• In descent, I typically use WOT and 400fpm from way back... maximizes speed... until redline or maneuvering speed become the driving force... unwind MP accordingly for 1” for each 1k’....
• and trim the rudder to the left during the descent... Smooth days with a well riggged Mooney, you will see the ball sitting sideways slightly.... matching the primary flight theory...
• With well balanced FIs, down low, an IO550 can run about 90°F LOP.  At 10K’, 50°F LOP is a challenge to get...great efficiency and CHT control...
• At altitude running a few °F LOP ensures all of the fuel is converted to maximum NA power available at altitude...
• Power starts to drop off the further LOP you go...
• It helps to decide before the flight... Is today’s objective Speed or efficiency, or somewhere in between...?

If you fly often enough, efficiency is critical...

If you can’t fly often enough, speed is a blessing... (FF is not as important) annual fuel cost when looking at... 10hours per year vs. 100 hours per year...

Pp thoughts only, not a CFI.

Best regards,

-a-

[Bob - S50]

6 hours ago, FastTex said:

I guess it's now time for me to LOP using the JP830 procedure instead of just pulling the mixture to 8.5GPH! I kind of like that easy pull without checking graph bars and numbers while flying the airplane...do you guys think it's necessary to go through the JP830 steps?

I only use the Lean Find function on our JPI when I'll be level at altitude for a long time.  Through experience I've learned that our #1 cylinder is always richest and the last to go LOP.  If I'm only going to be level for a few minutes I'll just lean while watching the #1 EGT.  Once it starts to drop I know I'm LOP.  Also, on my plane, peak EGT is usually something close to 1500 F.  If the EGT is down around 1350 I know I can lean pretty quickly until I get up around 1450 or so and then slow down to find peak.

However, if you ignore temperature, if you set the same MP and RPM every time, you should be able to set the same FF and be pretty darn close.

Or if I know that I'll probably end up around 9.3 GPH, I could do the big pull until I get to 8.5 - 9.0 GPH, then enrichen until #1 (my richest) goes through peak to ROP.  I could then lean again until I pass through peak to once again be LOP.

Almost always more than one way to accomplish what you want.