Finn Lassen wrote:
When I visited Tracy last Sunday I noticed some drops of fluid seeping
up on the upper left side of the cowling, but didn't investigate further
as water temp and pressure were ok. Seemed to happen at high altitude
(11,000') and high RPM (5,800).
Yesterday I flew over to the east cost of Florida to a couple of fly-ins
there. On the way back, I climbed to above 10,000' to get over the Tampa
Class B airspace. They couldn't understand my radio and told me to stay
clear of Class B, so I did a steep decent over the water north of
Clearwater to get down under 6,000'. I then noticed high water temps:
150C (302F) which is max for the sensor. Throttled back and limped over
to nearest airport which was Hidden Lake. Who did I find there? Bill
Hughes working on his 13B powered RV6. BTW, he has a peculiar cooling
installation. Two very thin oil coolers where Tracy and I have our water
radiators, and a bigger water radiator underneath the oil pan, being fed
by a small opening in the front bottom of the cowling. Not surprising
that he overheated his engine.
I took of my cowling and found that my overflow bottle had cracked. I
let the engine cool down and filled it with water. For good measure I
removed most of the duct tape I had put over half of my left radiator
(during the cooler winter temps).
On the short trip back to Clearwater (22 miles), temps were fine (max at
91C).
My theory on what happen is that a higher altitudes water in the engine
expands into the overflow bottle, and then when descending it contracts
and pulls the water back in from the overflow bottle to the engine. Only
in my case the bottle was cracked and so some air was sucked back in
instead of water. This probably happened gradually over the last 10 to
20 hours since I last checked the water level. Having done a bunch of
rolls probably didn't help either.
How do I find out if the engine was damaged? Do I need to drain oil to
see if there's water in it? Any other clues?
Looks like my water pressure sensor was damaged by the heat. Rated at
125C max.
I really need to implement the min/max warning feature in my engine
monitor.
BTW, Friday the 10 amp fuse to my leading coils again blew. I did notice
higher EGT temps, but didn't connect the two until I did
leading/training coil check before takeoff yesterday. Any suggestions as
to why it'd blow? Has happened now and then in the past, but for the
last many hours I've been careful to not turn on the power to the coils
until just before starting the engine.
Of course the recent high ambient temps (91F+) may have something to do
with all this.
I really need to get less complacent about popping the cowling a
frequent intervals to check that all is well in the engine compartment.
Finn
NetZero Platinum
No Banner Ads and Unlimited Access
Sign Up Today - Only $9.95 per month!
http://www.netzero.net
What does Bill Hughes's air outlets look like?
What does his intake duct and lips look like?
How large is his "thin" radiator?
Your theory on how the overflow tank works is correct if the the overflow
tubing goes to the bottom of the tank. The tank itself is vented to
the atmosphere at the top so a crack at the top will not effect it.
When the coolant heats up at low altitude it also expands. That is how
pressure caps and overflow tanks work. If the amount of fluid in the tank
is reduced for any reason the engine will suck air when it cools off.
All bets are entirely off if you fly inverted.
Slow rolls with negative G's alone will do it with or without cracks.
Also I think an overflow tank of at least one gallon is called
for. Perry noticed a small loss of coolant every time he flew his airplane
when using the stock one liter first gen RX7 overflow tank.
Paul Lamar
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/ http://www.linux.org