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1. 06:02 AM - Re: Re:cowling update (flyv35b)
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| Subject: | Re: re:cowling update |
I'll add some comments to Gary's (shown below)
1. The AA-1C POH says the plane should climb ABOUT 700 fpm at 77 kts betwe
en SL and 2000 ft at 1500 lb and 68 F with the cruise prop.
2. Opening the canopy greatly increases the drag and there is no data for
climb in that condition. Needless to say the ROC would suffer considerably
. Also the airflow around the cowling and windshield likely changed such t
hat hot air escaping from the engine compartment was getting sucked into th
e NACA fresh air ducts. This happens some anyhow with air that leaks out t
he cowl latches.
3. 290 F oil temp is way above the 245 F redline! What makes you say you
had 290 F=3F=3F Even 245 F is very hot for your ambient temp and the AA-1C whi
ch has an oil cooler, especially after only 10 min. Climbing at a slow spe
ed with the canopy open most likely adversely affects both oil and cylinder
head temperatures.
4. If you don't have a good digital 4 cylinder CHT instrument, I would buy
one as you may be cooking your cylinders as well. Also at least check the
accuracy of your oil temp instrument per the maintenance manual or install
a good digital instrument.
5. Don't climb with the canopy open if you want decent ROC and don't want
to cook your engine. And climb at a high speed than the POH says for best
ROC, probably about 90 kts.
6. Check your cylinder compression to see what the ring leakage is. Exces
s blow-by past the rings will overheat the oil.
Cliff A&P/IA
(Original Post)
hello all,
i have a 1978 grumman aa1-c with the original 0235 L2C i am located in sout
hern ca. my question is i recently flew with a passenger with only using 36
5lbs of my 489 useful load minus 6-8 gal of gas. i departed van nuys and sl
owly climbed to 2300' after about maybe 10 min of flight i noticed oil temp
was 290 or so ..close to yellow/red on gauge so i leveled out full rich an
d pull rpm back to 2100rpm it slowly cooled but what i noticed and what my
question is ...is that cabin heat was off and vents full open(oh by the way
i had canopy open) it was 70 degrees outside nice and cool but vents were
blowing out hot air i verified and cycled cabin heat it got hotter shut it
off but still warm....does anyone anything about this...thanks michael
(Gary's Post)
I'm sorry, but, I don't understand the question(s=3F).
(1) What I understand is: You had hot air coming out of your fresh air v
ents with an OAT of 70 degrees.
(2) What I understand is: When you open the cabin heat, the air from the
fresh air vents gets hotter.
(3) What I understand is: You were trying to climb a 2-seater at near gr
oss weight with the canopy open.
(4) What I understand is: Your average rate of climb to 2300 feet was 23
0 fpm.
(5) What I understand is: You had oil temps at 290 degrees.
======
(1) Check for a leak from your cowling
(2) There is no connection between the cabin heat and fresh air unless so
meone has modified the ventilation system
(3) Opening the canopy in flight increases parasitic drag. Climbing with
it open is a sure way to get behind the power curve. Ask me how I know.
(4) You need some serious engine work.
(5) You need some serious engine work. Then, install a quality digital o
il temp sensor. By quality, I mean, don't buy a Westac or some other cheap
, non-approved, instrument.
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