DA40 CS Power Settings

BravoZulu said:
25 squared for *many* airplanes is simply a good rule of thumb that typically provides adequate climb performance without overworking/overheating the engine...that is all I'm referring to..
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You may be using it that way but, it's actually more like an acronym: a barely adequate rule of thumb that substitutes a simple thought process for knowledge and understanding and may or may not be adequate for anything.

Let's see you get *many* piston airplanes without turbocharging to 25" MP where I fly on a mild day. I can almost hear a "squared is right" instructor (probably not you) insisting that I bring the prop back to 2200 RPM for takeoff and climb out :rolleyes:
 
MidlifeFlyer said:
Let's see you get *many* piston airplanes without turbocharging to 25" MP where I fly on a mild day. I can almost hear a "squared is right" instructor (probably not you) insisting that I bring the prop back to 2200 RPM for takeoff and climb out :rolleyes:
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Haha 2200 for a climb out in a constant speed that'll do 2700 that is just silly. I would have to recommend to that instructor to read a book on prop efficiency in climb vs. cruise before ever stepping foot in an airplane again!

Random off topic question if anyone can verify the accuracy: the majority of a props thrust comes from the outside 1/3rd of the prop. I was told this by an engineer back in high school (I flew RC planes alot then and this was in reference to a large spinner on a small prop) and I am kind of curious to its truth. Thanks
 
shdw said:
Random off topic question if anyone can verify the accuracy: the majority of a props thrust comes from the outside 1/3rd of the prop. I was told this by an engineer back in high school (I flew RC planes alot then and this was in reference to a large spinner on a small prop) and I am kind of curious to its truth. Thanks
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Not sure, but it sounds about right.
 
I have been told by many experinced (read old farts,70-80 yrs old) pilots that the throttle should never leave the firewall untill your ready to descend because the extra air being induced into the engine will help to cool it, and in a carburated engine, closing the throttle sinks the needle into the jet, and makes for less fuel to the engine, also raising the temps(granted we have control over this).
 
mshunter said:
I have been told by many experinced (read old farts,70-80 yrs old) pilots that the throttle should never leave the firewall untill your ready to descend because the extra air being induced into the engine will help to cool it, and in a carburated engine, closing the throttle sinks the needle into the jet, and makes for less fuel to the engine, also raising the temps(granted we have control over this).
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That is how I fly the arrow but it was green arc MP/RPM for climb to altitude, which is the same engine as the Cutlas RG but the arrow has better cooling. The RG on climb if I operate it like the arrow the CHTs go right to red line by 2500 feet on a cool day, I haven't tried it on a warm summer day yet. But once at altitude I agree and teach throttle to the floor that is the best way for that engine to run (Mechanic confirm this?), control its rpm with the prop to a difference of 4 (for IO-360s) for all the reasons I listed earlier.

It seems to be a trend that the more instruments and safety equipment we have the less we teach crude basics. How many people do you see lean an airplane by making it run rough then bringing it back to smooth operation? Why don't they, the engine will quit... Why don't we teach full stall landings? Stalls are bad you might die... Why 25 squared? We have no idea what engine limitations are because nobody told us...

I don't mean to be condescending in any way, I just find it to be an interesting historic trend. If the limits kill one person because they didn't understand those limits we should avoid teaching it because it is dangerous or someone here heard someone here had this happen to them. . . It is ridiculous, these aircraft are safe to perform all of these procedures the way they were done for years, there is no need to change them IMO.

PS This applies to flap settings from the other post and sorry much of my rant here sparked from reading that post just now.
 
mshunter said:
I have been told by many experinced (read old farts,70-80 yrs old) pilots that the throttle should never leave the firewall untill your ready to descend because the extra air being induced into the engine will help to cool it, and in a carburated engine, closing the throttle sinks the needle into the jet, and makes for less fuel to the engine, also raising the temps(granted we have control over this).
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That's the way they used to run them, probably lean of peak, too (only way to have enough fuel to get across the ocean most of the time.) http://www.gami.com/articles/1940lop.php.
I went to ADA, OK and had GAMIJECTORS installed on the A36 a while back. Wouldn't trade it for the world. FOT and LOP has saved a ton of maintenance compared to my friends running partial throttle, rich of peak settings.
http://www.gami.com/articles/powershot.php <--- more articles on the left hand column.

Someone told me once to run the throttle at like 98% or something arbitrary to induce a little turbidity in the flow to help more even distribution. Tried it for a while, determined it wasn't doing much (or anything) and went back to FOT.

Edit: LOP operations (done correctly and with proper instrumentation and fuel injection set-up) will lead to NO heat issues, contrary to popular belief. To quote George Braly at GAMI, "you can't shock cool an already cooled engine." I routinely run 20-40 degrees cooler than if I were ROP. They even had to keep in mind while engineering the baffling for their GAMI installations not taking away too much heat from certain cylinders because it would be very easy to do.

"Now, would you like to see something really interesting? Picture this, if you please. A normal takeoff with my IO-550, full throttle, 2700 RPM, full rich. We lift off, get the gear up, and reduce RPM to 2500 for noise, accelerate to 120 knots for the climb. I really like the higher speed, for cooling, and for visibility. Fuel flow is about 28 GPH at full power, drops to 25 GPH after the RPM reduction.
Prepare to Scream

But, now the wild one, prepare to scream. At about 1,000' agl, still wide open throttle, 2500 RPM, I reach down, grab the red mixture knob, and firmly and quickly pull it back to about 15 GPH! I have done this with a number of very experienced pilots, and most of them jump right out of their skin, in horror." That's what I'm talkin about.
 
http://www.avweb.com/news/pelican/182045-1.html
(taken from http://www.avweb.com/news/pelican/182544-1.html)

The problem is with operating an engine, I'm not a Dr. or any other type of "professional" that would lead anyone to believe I have a high IQ, but when I meet up with my smart Dr., Attorney, etc friends at the airport and talk to them about flying, I realize they can't even get their lawn mower started for the first pull (or turn of the key) of the season, much less understand and subsequently properly lean a plane while on the ground or (esp.) in the air. Some people may get it, but it's so overwhelming they forget to look outside the plane while getting the engine set up. Some people get it, some don't. Has nothing to do with smarts. Kind of like aviating in general. Just takes experience and repitition (of the correct proccesses and steps), not just weekend warrioring it a lot of the time. My dad is a great weekend warrior pilot, but he's also an engineer so I guess people like him just kind of "get it."
 
I have found that VERY few pilots really understand what is going on under their cowling. Since 95% of CFIs come out of puppy mills where this stuff isn't taught AT ALL, they can't teach it to their students.

That's how we get the same myths carried on as gospel.
 
I've also found that A&Ps can be hit or miss at truly understanding recip theory. I heard a lot of those same OWTs going through A&P school.
 
LatitudeDancer said:
http://www.avweb.com/news/pelican/182045-1.html
(taken from http://www.avweb.com/news/pelican/182544-1.html)

The problem is with operating an engine, I'm not a Dr. or any other type of "professional" that would lead anyone to believe I have a high IQ, but when I meet up with my smart Dr., Attorney, etc friends at the airport and talk to them about flying, I realize they can't even get their lawn mower started for the first pull (or turn of the key) of the season, much less understand and subsequently properly lean a plane while on the ground or (esp.) in the air. Some people may get it, but it's so overwhelming they forget to look outside the plane while getting the engine set up. Some people get it, some don't. Has nothing to do with smarts. Kind of like aviating in general. Just takes experience and repitition (of the correct proccesses and steps), not just weekend warrioring it a lot of the time. My dad is a great weekend warrior pilot, but he's also an engineer so I guess people like him just kind of "get it."
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What is so hard about turning a knob counter clockwise while looking outside till they hear the engine sputter then turn it in 2 turns? The problem isn't them being able to divide their attention, its them thinking they need to stare at the EGT/CHT like it is going to steal their life savings while they touch the red knob, simply ridiculous. When my student does that I pull the mixture and we listen to the prop windmill for 30 seconds or so till i throw the mixture back in, engines don't just shut off, if they have fuel they will run you don't need gauges to lean. Note: I recommend having a place to land (airport) if you demo this, chances are practically non existent that it wont restart, but better safe then sorry.
 
USMCmech said:
I have found that VERY few pilots really understand what is going on under their cowling. Since 95% of CFIs come out of puppy mills where this stuff isn't taught AT ALL, they can't teach it to their students.

That's how we get the same myths carried on as gospel.
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It's worse. You don't have to understand what is going on under the cowling. All you need to understand is that there's a whole section of the POH that is dedicated to performance. There seems to be a preference for "let's pass on stories" over "let's look it up"
 
MidlifeFlyer said:
It's worse. You don't have to understand what is going on under the cowling. All you need to understand is that there's a whole section of the POH that is dedicated to performance.
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You mean, actually run your engine acording to the manufacturers instructions? That's just crazy talk.
 
USMCmech said:
You mean, actually run your engine acording to the manufacturers instructions? That's just crazy talk.
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I have had students come to me for their solo stage exam that still have the POH in the plastic wrapper. Sure enough they fail my brief as I revolve it completely around the aircraft, these aren't VCRs, not reading these instructions costs us all a lot of money and some end up killed over it.

I think every pilot should own a copy of the A&P engines manual, 20 bucks to never be confused about how that thing works again seems fair to me.
 
SteveC said:
No thanks.
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That falls back to "There seems to be a preference for "let's pass on stories" over "let's look it up." You cannot even look up an engine issue without this book at least not any private pilot book where you learn vapor lock is from tanks running out of gas! :(

Steve your a slacker lol
 
shdw said:
What is so hard about turning a knob counter clockwise while looking outside till they hear the engine sputter then turn it in 2 turns? The problem isn't them being able to divide their attention, its them thinking they need to stare at the EGT/CHT like it is going to steal their life savings while they touch the red knob, simply ridiculous. When my student does that I pull the mixture and we listen to the prop windmill for 30 seconds or so till i throw the mixture back in, engines don't just shut off, if they have fuel they will run you don't need gauges to lean. Note: I recommend having a place to land (airport) if you demo this, chances are practically non existent that it wont restart, but better safe then sorry.
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I use that method in 172's and the sort. On the DA40 I'll do it, then hit the "lean" button or whatever it is and check the CHTs are happy and off we go.
I've gotten used to it enough in my 36 I actually yank it back firmly where I know feels right and quickly check the fuel flow (since I'm actually going LOP). When I get the chance I'll spend a sec on CHTs, but it's on 98% of the time +/- .1 gph. $90,000 a powerplant steals my life savings pretty fast, so I give it a little more than a quick once over.
 
shdw said:
That falls back to "There seems to be a preference for "let's pass on stories" over "let's look it up." You cannot even look up an engine issue without this book at least not any private pilot book where you learn vapor lock is from tanks running out of gas! :(

Steve your a slacker lol
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I'm a slacker too and you quoted me. :dunno:
 
shdw said:
I think every pilot should own a copy of the A&P engines manual, 20 bucks to never be confused about how that thing works again seems fair to me.
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SteveC said:
No thanks.
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shdw said:
That falls back to "There seems to be a preference for "let's pass on stories" over "let's look it up." You cannot even look up an engine issue without this book at least not any private pilot book where you learn vapor lock is from tanks running out of gas! :(

Steve your a slacker lol
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You read too much into my response. I'm all for pilots following manufacturer's recommendations - from the AFM and POH. Trust me when I tell you that theose documents alone for the two aircraft that I fly are MORE than ENOUGH information and there is no way that I "should own a copy of the A&P engines (sic) manual". I'm of a similar opinion for smaller aircraft as well.
 
SteveC said:
You read too much into my response. I'm all for pilots following manufacturer's recommendations - from the AFM and POH. Trust me when I tell you that theose documents alone for the two aircraft that I fly are MORE than ENOUGH information and there is no way that I "should own a copy of the A&P engines (sic) manual". I'm of a similar opinion for smaller aircraft as well.
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I was just joking with you anyways bud. But out of curiosity, what are you flying?
 
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