Cirrus Pilots
- Thread starter MikeOH58
- Start date
jtrain609
Antisocial Monster
My mistake, Amflight opeates rich of peak, but also has a limit on the EGT that they're not allowed to go past when leaning.
But even if you were to run that same engine lean of peak, if you're got an EGT guage and a CHT gauge you shouldn't have any problems doing so as long as you're paying attention to what you're doing. You won't have the advantages of having a probe on each cylinder, but if you have other limits you shouldn't exceed (both EGT and CHT) along with listening to how the engine is running, it shouldn't be a problem.
At 8,000' if you pulled the mixture back too far you'd choke the engine real fast, which should be your first indication that you've screwed something up.
But even if you were to run that same engine lean of peak, if you're got an EGT guage and a CHT gauge you shouldn't have any problems doing so as long as you're paying attention to what you're doing. You won't have the advantages of having a probe on each cylinder, but if you have other limits you shouldn't exceed (both EGT and CHT) along with listening to how the engine is running, it shouldn't be a problem.
At 8,000' if you pulled the mixture back too far you'd choke the engine real fast, which should be your first indication that you've screwed something up.
USMCmech
Well-Known Member
If Amflight is running the engines at Max power, without ballanced injectors, without good instrumentation then I would suspect that they are running much hotter than a Cirrus LOP.
My opinion is that running at Max power is too hot and over time causes most of the problems attributed to "shock cooling".
You should do some homework on running LOP. The things that you're talking about doing can screw up an engine royally, and I'd rather have that kind of misinformation nipped in the bud.
Here's your homework assignment; Google lean of peak, George Braly, GAMI injectors.
TFaudree_ERAU
Mashin' dem buttons
You can't possibly run LOP without an EGT/CHT indication for each cylinder. Unless you're running 25* LOP on the hottest cylinder, you're doing damage. There is no way that a single point EGT can give you enough information to properly run LOP.
The difference between peak EGT and 25* LOP is .1-.2 gph. You can't possibly measure that on an analog fuel flow gauge. When I run LOP below 65% BHP in the Cirrus, I often see the cooler (more lean) cylinders running between 40-50* LOP. The hottest cylinder, or "last to peak" in Avidyne-ese is what the lean assist looks at when making its calculations for LOP operations.
Also, take into consideration the fact that the OEM fuel distribution system in aircraft such as the Navajo/Chieftan is horrible at producing an even flow across all 6 jugs. Coupled with the lack of direct feedback from individual cylinders and exhaust ports, running LOP without the proper equipment is quite possibly the #1 way to have a bad day.
To tell you the truth, I had never heard of LOP until GAMI and JP Instruments came along. There is a really good reason for that.
jtrain609
Antisocial Monster
So, check it out.
This is obviously an area I'm not up to speed on, so I'm trying to get my head wrapped around this.
GAMI injectors, cool, fine, makes sense.
The gauges though, this is confusing to me about why you can't run LOP without having probes on all your cylinders.
If you're running 25 degree's lean of peak, what does the FF matter apart from the injector being of a high quality? I.E. If shouldn't the accuracy of the gauge matter more than whether it's digital or analog? Also, if you've got your probe on your hottest cylinder, doesn't that protect the rest of the engine? I.E. You set 25 degrees LOP and then if the engine happens to get too hot, you're watching the CHT's and you add a little bit of gas to the mix to cool the engine off eh? Or said another way, if you've really botched it and you're running AT peak, you're going to have more than one sign of doing so eh? Or at least that's what I would think.
Does that all make sense?
This is obviously an area I'm not up to speed on, so I'm trying to get my head wrapped around this.
GAMI injectors, cool, fine, makes sense.
The gauges though, this is confusing to me about why you can't run LOP without having probes on all your cylinders.
If you're running 25 degree's lean of peak, what does the FF matter apart from the injector being of a high quality? I.E. If shouldn't the accuracy of the gauge matter more than whether it's digital or analog? Also, if you've got your probe on your hottest cylinder, doesn't that protect the rest of the engine? I.E. You set 25 degrees LOP and then if the engine happens to get too hot, you're watching the CHT's and you add a little bit of gas to the mix to cool the engine off eh? Or said another way, if you've really botched it and you're running AT peak, you're going to have more than one sign of doing so eh? Or at least that's what I would think.
Does that all make sense?
TFaudree_ERAU
Mashin' dem buttons
How do you know that the EGT gauge is on the hottest cylinder? You don't. Actually, a single probe EGT is located in the exhaust manifold, not at the exhaust port as it is in a multi-probe installation.
Analog gauges just aren't as precise as a digital gauge. Can you measure 1436*F on your analog gauge? I can on my digital.
You have to know precisely which cylinder is the hottest to run LOP. Thats the key. You would assume the rear cylinders, but you'd be surprised. I've found that sometimes the middle set of cylinders on the Cirrus are the hottest.
jhugz
Well-Known Member
How long ago did you go through the training miller?
Also I could of sworn that the CHT's were 425 red line 400 max in cruise and about 380 normal in the turbo. I may be confusing numbers with the 20.
jtrain609
Antisocial Monster
Really? See I've asked mechanics about that, "How in the world do you know which one is the hottest."
They've said, without fail, it's the cylinder that receives the least amount of airflow over it. I think in the Chieftain that was the number six cylinder, so they ran the probe off of that one.
How often have you found that the hottest is in the middle? I know it can change depending on a lot of things, but have you found a predominate answer on that?
trafficinsight
Well-Known Member
On the Arrow Piper sez the EGT probe goes on the number 2 cylinder, which is a front cylinder, I would venture a guess and say that's not the hottest cylinder... but there ya go.
bdhill1979
Gone West
1 and 2 (at the back) are always hotter than 5 and 6 in ours, usually by around 40 degrees.
TFaudree_ERAU
Mashin' dem buttons
I've never paid much attention to which one has the habit of being the hottest. The lean assist takes care of figuring that out for me, so it doesn't require a whole lot of attention. I'll take a look at some of our old Emax engine trend data and come up with some sort of observation.
The hottest cylinder can easily vary from airplane to airplane straight out of the factory. The "least amount of airflow" answer is partially correct, but other factors come into play, and in fact using that as a complete answer is incorrect. It's a popular OWT (Old Wives Tale) that gets passed on from person to person without being completely accurate. Even if it were the total answer it's important to note that things like very minor variations in the quality and installation of baffles, cowlings, linkage to cowl flaps, etc, can all affect airflow substantially, so much so that it is foolish to say that any particular cylinder is going to get the most cooling airflow based only on which model of airplane it is.
Airflow aside, are you up to speed on why GAMI injectors are an important part of the LOP equation? It partially answers your question as well.
Airflow aside, are you up to speed on why GAMI injectors are an important part of the LOP equation? It partially answers your question as well.
USMCmech
Well-Known Member
The hottest CYLINDER may be the one with the least airflow, but the hottest EGT may be different.
Fly_Unity
Well-Known Member
Im a CSIP Instructor with over 500 hours in the 22 Turbo. I dont like leaning using your method but alot of Cirrus Pilots do it as you described. Cirrus NOW recommends leaning to 50 degrees LOP, In fact on their Perspective planes all you do is pull the mixture lever back to the arrows match up which will give you 50 LOP.
wjmiller3
Well-Known Member
I am a CSIP too, and that is the way Cirrus told me to do it when I went through training.
wjmiller3
Well-Known Member
Went through CSIP trainig last October, 380 is the majic number for cruise in a 22 turbo, you should not be over that. Not saying that is the redline, just the number not recomended to go over. As for the 20, I rarely fly them so I cant think of those numbers off the top of my head.