REFLECTOR: First flight

Grover McNair grover at mcnairperformance.com
Tue Jun 12 14:15:40 CDT 2012


Liquid cooled engines have the advantage of more even cooling. Liquid also
transfers heat better than air. Air cooled engines tend to have hot areas
and cooler areas. Tolerances are set to allow for expansion and contraction
with temperature change.

The limits on oil temp are due to the oil itself. Oil tends to break down at
higher temperatures. Generally I start getting concerned if I see 250 or
higher in a piston engine. Over 270 and you will start having problems.
Synthetic oil can stand higher temps than mineral based oils and still
retain their lubricating ability. Still I like 250 as a maximum. It allows
some margin. If it goes any higher I would change it as soon as practical.

In Mazda rotary engined cars the oil cooler has almost as much cooling
capacity as the radiator. These engines are very dependent on oil for
cooling. When racing we tried to keep the oil and water temps in the same
range, about 200 degrees. Mazda does not recommend using synthetic in
rotaries although I personally have used synthetic with no adverse affects.

Grover

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of John Dibble
Sent: Tuesday, June 12, 2012 8:48 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: First flight

 

I have some more thoughts.  Auto engines don't have oil coolers because they
have a big-assed radiator which provides adequate cooling over a broad range
of driving conditions.  Also the thermostat precisely controls the coolant
(cylinder) temp.  This allows tighter engine tolerances compared to
air-cooled engines where CHTs vary considerably requiring looser tolerances
for expansion.  Since no one seems to be installing car sized radiators on
airplanes, the cooling strategy shifts toward that of air-cooled engines
where an oil cooler is needed to supplement cooling.  Also there is the
possibility that cooling may be inadequate at times resulting in higher
temps.  The question is what should the temperature limits be?  Probably
less than for engines designed for air cooling.  Maybe someone has already
worked this out.

John

On 6/10/2012 8:20 PM, Grover McNair wrote: 


Having raced Mazda rotary engines for about 20 years I respectfully disagree
with the idea of not being concerned with the max temp of the oil. Rotaries
cool as much with oil as with coolant. Keeping the oil outlet temp below 230
was always best for engine longevity. I support the comparison to coolant
temp sensing.

I would put the oil coolers in series. Any fluid will follow the path of
least resistance.

Grover McNair

Sent from my iPhone


On Jun 10, 2012, at 3:24 PM, Chris Barber <cbarber at texasattorney.net> wrote:

Wow, thanks guys...funny, I get to a point that I think I am pretty versed
and then new info (well, new to me) come in.  It should not be too difficult
to add a sensor to the oil going into the engine after the coolers.  Thanks.

 

Chris

From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] on behalf of
Al Gietzen [alventures at cox.net]
Sent: Sunday, June 10, 2012 2:12 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: First flight

Chris; 

I agree with John. Engine out temp on the oil can be 250F without worry.  If
you have unused channels of the EM; rig a TC at the outlet of each cooler,
then you'll know the delta T on each and if they are considerably different
you can consider restricting flow to the one with the low delta T.  They
don't need to be the same, but you'd like the higher delta T to be less than
about 50F for best overall cooling. Will also indicate oil temp back to
engine; which may suggest you really don't have an issue. 

 

You can rig a TC to a metal line with a hose clamp and a pad of insulation
between clamp and TC; TC junction against the line. 

 

Al 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of John Dibble
Sent: Sunday, June 10, 2012 11:36 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: First flight

Ahh.  There's your problem.  You should be measuring the temp of the oil
going into the engine from the coolers.  So you oil wasn't as hot as
indicated.

John

On 6/10/2012 1:12 PM, Chris Barber wrote: 

Maybe, but both get hot.  I am taking the temp reading as it is coming out
of the engine at the filter.

From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] on behalf of
John Dibble [aminetech at bluefrog.com]
Sent: Sunday, June 10, 2012 12:57 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: First flight

Hmmm.  With the coolers in parallel, how do you know where the oil is going?
Seems like it will take the path of least resistance.  Maybe one cooler
isn't doing much?

John

On 6/10/2012 8:34 AM, Chris Barber wrote: 

I have two oil coolers already.  The standard cooler mounted under the
aircraft laid flat with the radiator to make one large unit and fed with a
large ram air scoop on the bottom of the cowl.  I also have a second oil
cooler (standard aircraft cooler as provided by Velocity) in the nose per
planes plumbed in parallel.  It was originally plumbed in series but since
it has smaller fittings, it was causing a pressure issue and oil would seep
out from around my oil filter.

 

I got some pondering to do.

 

I was just looking at the distorted video I took while in the pattern on
downwind.  It is only a few seconds long.  Very hard to see some of the
info.  It does show my rpm got up to 6870 rpm but the map on the RWS monitor
was only indicating 24.7. (?)  I am running a spring in the waste gate at
1.5 lbs. Coolant temps were 187 degrees while oil was 224 degrees.  GPS
speed showed 128 kts per the Dynon.  

 

The IVO in-flight adjustable prop was at full fine. The IVO pith range is 45
- 105 and IIRC it is 68 inches.

 

Chris

From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] on behalf of
John Dibble [aminetech at bluefrog.com]
Sent: Sunday, June 10, 2012 7:27 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: First flight

I second that for the oil cooler.  Are you using the standard oil cooler?  I
think a problem is that the standard oil cooler is intended for engines in
the 180-200 hp range and for engines with more hp, a larger cooler is
needed.  It doesn't take much increase in cooler size to make a big
difference in cooling, so a larger cooler (1" taller) may be all you need
and simpler than adding a second.

John

On 6/9/2012 8:28 PM, Al Gietzen wrote: 

Way to go Chris!!  That is a life-changing milestone.  Congratulations! 

 

Reminiscent of 1st flight with my plane - oil temp hit 225 and ended the
flight with one turn around the patch. As you said; not critical, but you
don't want to run a rotary very long above that temp.  For me it took some
work on the scoop; and eventually a second oil cooler to keep things in the
comfort zone on a hot day.  You might consider an auxiliary oil/coolant heat
exchanger. 

 

Now that you are a "real" pilot, get out there at 0700 when air temp is
below 80 and maybe you can fly long enough to enjoy it. 

 

Al 

 

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Chris Barber
Sent: Saturday, June 09, 2012 9:50 AM
To: REFLECTOR
Subject: REFLECTOR: First flight

Cleared to take active and hold. Taxied out. Lined up castering nose wheel
down center stripe. Cleared to take off. Added power and engine smoothly ran
up. Airspeed coming in. 30 kts...50 kts ....60 kts, approximate rotation
speed. Lots of runway (9000 ft).....hold it....70 kts....72 kts... Slight
pull on the yoke....AIRBORNE!!! Leaped into ground effect. Screw this,
pulled back on yoke and I am climbing. Jiggled the yoke a bit to verify
control authority. 

 

Climbed to about 400 feet and turned right pattern to crosswind. The Dynon
altitude and airspeed seem to be working. That's reassuring. Pattern
altitude is only 600 feet and I was there already as I turned to downwind.
Leveled off and noticed the clouds were lower than reported and appeared on
the ground. Also, noticed coolant temps had dropped to 190....but oil temps
were flashing at me and had reached 225 (synthetic Royal Purple). Damn. Ok.
Fly the airplane, the oil is not at not a critical level. , but let's just
finish the pattern and land. I grabbed my phone while on downwind and
attempted to record some data but while I can hear the engine the video is
awful....uh, in my defense, I was a bit distracted and way more concerned
with flying. I called the tower and informed them I was coming in. I think
they were looking out for me since as I turned to base I noticed the fire
department staged just off the runways threshold

 

I noted I was a bit far out on down wind so I stared easing over to turn
base. Wow. I really overshot it as I blew by the runway and had to use full
right rudder to get back to the runway. I wish I had had more rudder. In
hindsight I think I was not using much aileron as I was cognoscente that I
had no idea of stall characteristics so I did not yet wish too strep a turn.
I was able to get over the runway and dump some altitude as I got over the
numbers and pulled power. Crap, I am fast. I am lined up and right on the
numbers but at 95 kts. I come and touchdown and bounced. Pulled power to
idles and settled down easily but fast at 90 and rolled out and exited at
Delta. The tower was clearing me back to the city hangars as I was exiting
the active. I taxi back and noticed the oil temps had decreased but I don't
recall how much, just noticed they were lower.

 

I got back to my hangar and popped the door and shut her down. The engine
went silent without any hissing or gushing. 

 

I called my mom. 

 

I am mowing informing the world. 

 

I did a walk around and did not see anything missing. I am about to pull the
cowl and check things out. 

 

I did notice I did not develop a slight hand shaking untill after I landed
and exited the aircraft. ;-) Hey, how about that, it really is an aircraft
now. Ten years to the day following delivery. 

 

Thank you for your support. 

 

Christopher Barber, JD

Houston, Ellington Field (EFD)

Velocity N17010

Turbo Rotary 13b

RWS Re-drive and engine computers

Dynon Skyview

Mistral intake



Sent from my iPhone 4

 

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