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PostPosted: Thu Sep 21, 2017 4:48 pm 
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I understand you want cowl flaps closed when cruising and open when you're on the ground. The manual also says you want them opened depending on engine stress? Is there a gauge to help gauge when the engine is stressed? CHT? Temps? I see some checklist items say something like, cowl flaps "as necessary" but how do I know what is necessary beyond simply fully closed or open? Thanks in advance.


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PostPosted: Thu Sep 21, 2017 4:59 pm 
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Location: Typically hanging around N07, 12N, KLDJ, KCDW
Primarily CHTs and then oil temps. Oil temp generally shouldn't go too high unless you are running at high power and low airspeed for a prolonged period.

CHTs will generally be the best guide. They can take several minutes to stabilise after airspeed, power, leaning and other config changes, so do check them again after closing the cowl flaps.

Keeping CHTs below 400 is best for max engine life as a general rule.


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PostPosted: Fri Sep 22, 2017 3:07 pm 
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Oracle427 wrote:
Keeping CHTs below 400 is best for max engine life as a general rule.


Which is why the color coding on the gauge continues to baffle me (being green all the way up to 499). Why not make the 425-499 range yellow like the Comanche's is?


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PostPosted: Fri Sep 22, 2017 3:12 pm 
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Location: Typically hanging around N07, 12N, KLDJ, KCDW
That's a Cessna thing. It's the same way on the G1000 which is very annoying to me as I have to flip odder to the system page to see the actual CHT temp. It's very hard to tell if I am at 350 vs 420 as it stands.


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PostPosted: Fri Sep 22, 2017 3:16 pm 
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Oracle427 wrote:
That's a Cessna thing. It's the same way on the G1000 which is very annoying to me as I have to flip odder to the system page to see the actual CHT temp. It's very hard to tell if I am at 350 vs 420 as it stands.


That doesn't sound good. I hope it's easier to tell if you're much above 420?


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PostPosted: Fri Sep 22, 2017 3:51 pm 
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With experience you get used to what’s normal. I personally use the letters of the gauge as a guide. In the 182RG I fly the CHT usually sits between the “A” and “D” in “HEAD” when viewed from the left seat during both climb (cowl flaps open), and cruise (cowl flaps closed). If it goes higher than that I know I should apply some sort of corrective action.


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PostPosted: Fri Sep 22, 2017 4:47 pm 
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Location: Typically hanging around N07, 12N, KLDJ, KCDW
It's extremely easy to tell the temp with one button press, it's just annoying that you cannot see that without hiding a lot of other useful information.

Bottom line is that you get to know the plane after a while. It's all part of pitch and power equals performance. Part of the performance calculus beyond airspeed and climb rate includes temps, fuel flow. I like to cross check those parameters to get more clues about the health of the airplane and to make sure I haven't missed anything important.

If I go into a cruise climb and see that i have a very high fuel flow that's another reminder to lean. The plane will climb just fine at lower altitudes while easily burning an extra 5 gallons per hour.


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