Cowl Flaps
- Thread starter Dazzler
- Start date
jtrain609
Antisocial Monster
Cowl flaps are located on the bottom of the cowling. They are doors that you can open to control the cooling of the engine. I.E. You keep cowl flaps open during climb in most situations so you have additional cooling of the engine when it's operating at high RPM and high temps. When you get up to cruise you'll close them up because the engine is running cooler and they pretty much act as speed brakes.
wheelsup
Well-Known Member
Something to remember out piston engines - it's not so much the temp they are operating at that will hurt them (to an extent), it's the rate of temperature change that will bend metal. Cowl flaps help you control the rate of change vs. the actual temp (although they do control temp as well).
~wheelsup
~wheelsup
BPF
Well-Known Member
Here in buf, it gets COLD...so sometimes, on extra cold days, I'll leave the cowl flaps closed or only partially open on take off until the CHT gets about mid-range in the green. Sometimes, when cruising at low altitudes (short climb), I never open them. Basically, I monitor the CHT instead of always open and close them at specific phases of flight.
Depends, I think. Some of the 400 series Cessnas it can mean quite a few knots of airspeed - not inconsequential if you have a long flight.tonyw said:
We often leave them closed on approach and landing to help control engine cooling rates. Just gotta remember to run the appropriate check list and open 'em back up if you do a go-around or aborted landing.
ComplexHiAv8r
Well-Known Member
tonyw said:
When I did my complex they had me leave the cowl flaps closed until on the ground in the event we needed to go around. I did my training in a 172RG.
Cheechako
Well-Known Member
Oh, yeah, cowl flaps... I forgot about those until just last week...
Flew a Cessna 207 for the first time in a year and didn't remember about the cowl flaps until leveled off at cruise altitude (600' in my case- I love flying in Alaska!). It was 33 degrees F so I don't think it really mattered!
Flew a Cessna 207 for the first time in a year and didn't remember about the cowl flaps until leveled off at cruise altitude (600' in my case- I love flying in Alaska!). It was 33 degrees F so I don't think it really mattered!
Nick
Well-Known Member
Performance
I have noticed an increase in performance in some airplanes and not much in others.
In the Mooney 20J there was a gain of 5-8 knots once they were closed. The engines in them had such a hard time keeping warm on cold New England days and nights that we'd often close them halfway at 1,000 AGL and then all the way once at cruise. The CHT would never make it past 1/3 of the way up.
In the C-172RG I noticed only a couple of knots gain, less than 5.
In the Piper Seminole, most of the time when I'd grab the lever to close them the knobs would fall off onto the floor and so I thought, if that's how important Piper thought they were, I'd just leave 'em where they were! Just like everything else in those airplanes that broke hourly.
tonyw said:
I have noticed an increase in performance in some airplanes and not much in others.
In the Mooney 20J there was a gain of 5-8 knots once they were closed. The engines in them had such a hard time keeping warm on cold New England days and nights that we'd often close them halfway at 1,000 AGL and then all the way once at cruise. The CHT would never make it past 1/3 of the way up.
In the C-172RG I noticed only a couple of knots gain, less than 5.
In the Piper Seminole, most of the time when I'd grab the lever to close them the knobs would fall off onto the floor and so I thought, if that's how important Piper thought they were, I'd just leave 'em where they were! Just like everything else in those airplanes that broke hourly.
hattrick
Well-Known Member
as said they are used to control engine temp (especially rate of temp change) with that in mind kbuf was talking about leaving them closed on takeoff in the cold. if i have a warm engine on a cold day i will leave them partially closed. mind you im talking really cold. it seems to keep the engine at a fairly uniform temp. but with a cold engine and temps above 0 or so ill leave them open so as not to heat my engine too quickly. on landing close those things up especially in the cold or you will shock cool the engine. not a good thing.
just a quick question though. how did you make it through commercial and cfi training without knowing what cowl flaps are. every complex airplane ive flown has them just wondering what doesnt
just a quick question though. how did you make it through commercial and cfi training without knowing what cowl flaps are. every complex airplane ive flown has them just wondering what doesnt
USMCmech
Well-Known Member
KBUF said:
Ditto all of the above with one exception.
Always open your cowl flaps when on the ground, even in Antartica.
On the ground with the cowl flaps closed there is no airflow through the engine. Air is NOT forced in by the propeler, it is sucked out by the airflow around the cowling. The open cowl flaps create a low pressure area which draws the hot air out of the engine compartment.
Running with zero airflow to cool the engine for even a few minutes can create localized hot spots damageing to the engine, regardless of what the CHT guage says.
, but now I know why they have to be left open on the ground, thanks