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TJ, well I think the reality is, there will be a point where you have to draw a line and say, if it will do this under this, this and this conditions then I'm happy. The only reason I brought it up was because the way you'd layed it out, my 414 wouldn't fit, nor would a very large percentage of certified a/c. Yet I know my 414 to be an excellent aircraft, which in my opinion, has never let me down due to some part of it having a poor design. [well other than the water/oil seperator when flying in high humidity, winter conditions but .. thats more to do w/ the engines system design than the airframe, or its integration :-) ]

Now I'll tell you why I had an oil temp problem.

#1. I sat on the ground idling in Vegas [30dC outside] w/ a 27G37 tail wind for 1 hour and 47 minutes. It took 1 hour and 20 minutes before the oil temp got high, the last 27 minutes I was #1 for dept on Julite/hold Short on 19R and could turn into the wind to cool it back down. The oil temp never reached red line, and it may never have reached it, but it was high enough that I wasn't comfortable w/ it.

#2 I could climb at just over Vmca and it would overheat.. but I know of NO REASON to do so. First of all, Vmca is like 79 knt's. My Vx and Vy are both up around 120, at Vmca it's very possible that the a/c would hardly climb at all, at gross weight, but I could still fly at that speed. It would be a senseless act, but it still does fit your parameters.

The 414 I fly is a Ram IV, it has all the airflow do-dad's you could imagine [ I think RAM has come out w/ a couple new conversion's since this one but.. they only have a few more minor slow speed handling upgrades] It has cowl flap's as well as the top-of-the-cowl gill. The gill is behind the engine and allow's for cooling air to get to the turbo's during cool down [after shut down] and allow's the hot air out. I don't think it has a whole lot of effect while in flight.. [it must have some.. but I don't know how much.. and at this point it's irrelevent] well other than freaking my passengers out when they see the glowing turbo's through there at night.. It freaked me out for the first couple hundred hour's I flew it.. but after a while you just get de-sensitised to it :-)

There is nothing wrong w/ the cooling abilities of the airframe when flying it properly. I get 120dF oil temp's during the summer at cruise and climbout and 320dF cylinder head temp's as well. It is actually cooling too well! We had to block off 1/3 of the oil coolers to get the oil temp's up to where I was comfortable w/ them [over 150dF] and it had these in place when I had the hot oil in Vegas.

I guess the point I was trying to make is, there will always be a point where something won't work the way you want it to, if you have to sit and idle for just about 2hrs w/ a ~35knt tail wind in the desert, before the oil overheats, I think you have a very good system. If you tried to improve on it at this point, your just pushing yourself way down the efficentcy ladder. There's a reason the old Jenny's of the 1920's were soooo slow.. [amoungst other things] they had a 4ft x 4ft rad right out on the front of the airframe about 4" behind the prop.. I think they cooled good though.. :-)

I would re-write your cooling requirements to be something like this:

A) idle for more than 1hr on the ground w/ a outside air temp of up to 35dC, with a maximun tail wind of 15knt's.

B) Support 3 minutes of Run up into wind with zero ground speed at max power.

C) Support a max power climb for not less than 5 minutes at Vy or Vx [you pick] w/ an outside Air temp of not greater than 35dC.

Tempurature maximum's: Oil-225dF, coolant- 210dF [or whatever they might be]

Honestly I think under the exact same conditions in a car it would have overheated as well [that day I was in Vegas] It was #@#^$ HOT and the wind was like a furnace.

Anyway, we all know that designing a cooling system is going to be a compromise, I just don't think blanket spec's as open as what you'd listed are going to get you the system you need. We already fly our planes to fit parameters [ or in your case heli's :-)] we just have to continue in that vein and write spec's of which we'd be happy w/ and then tweak the system until we get there.

Not poking fun or trying to be facetious, I just wanted to shed some real world experiance "light" to the conversation.

Best

Jarrett

----- Original Message -----

From: Thomas Jakits <rotary.thjakits@gmail.com>

Date: Friday, May 25, 2007 9:30 am

Subject: [FlyRotary] Re: Marginal Cooling

> Jarrett,
>
> I know it will be tough to build my requirements, but with liquid
> cooling it
> should be possible.
> Smart ducting (I hope the smart part *does* arrive at my place
> sometime....), exhaust augmentation, should make it possible.
> I am in this for the fun of building and tinkering. My job gives
> me enough
> time in the air.... so going flying soon is not the driving force.
> Also, I do believe your (commercial) ride could be made to be okay
> on the
> temps, as it is certified, cost will play the major drum.
> Just for curiosity, does the 414 have rounded lower exit corners
> at the
> firewall? ...or is this one of those jobs where the hot air and
> exhaust exit
> on top?
> I choose "any speed", because I read all these reports about
> getting hot
> (short of overheating? :)) on climb, leveling off to cool, alright on
> cruise.
> I understand that excessive cooling will cause drag, but that's
> where I plan
> to use "airflow control".
> CMIIAW - a overspilling frontal intake will not produce any more
> drag than
> if there would be no intake at all.
> Same with Naca - if there is no flow through the Naca (and it is built
> correctly) there should not be a lot of drag.
> For my BD-4 the Naca is probably no good, but for any canard it
> will work if
> you take care of details.
>
> I believe in the "package" - the best intake will not work if the
> exit is no
> good - and everything in between.
> Sometimes I hear the "too complex" excuse. Look around and copy
> someone that
> works.
> Augmentation may be more complex to build, but there are no moving
> parts. A
> cowl flap is simple device, although - it moves :))
> In the end you will spend a lot more time to rebuild your simpler
> systemover and over again.
>
> TJ
>
>
> On 5/22/07, Jarrett & Heidi Johnson <hjjohnson@sasktel.net> wrote:
> >
> > I have no horse in this race at this time, however something
> that Thomas
> > wrote struck me funny. If this is the standard to which we
> should be
> > building our a/c then the Certified C414A that I fly in [one of
> my day
> > job's] wouldn't fit it in two area's.
> > A) I had a 1hr 47min idle on the ground in KLAS [waiting to be
> #1 for
> > dept] here a few weeks ago, I finally had to ask the tower to
> let me turn
> > into the wind as my oil temp's were getting too high.
> > C) If I was to climb out at just over Vmca I KNOW that the
> cylinders would
> > hit over redline in under the five minutes. I don't know why
> someone would
> > do this as Vx and Vy are both up around 100-120knts [Vmca=79knt]
> but you did
> > say ANY speed... Anyway, just another data point to hold up to
> the light and
> > compare w/ what you guys see as a need and a want..
> >
> > Jarrett
> >
> >
> >
> > Personally I believe that a cooling system should be able to:
> >
> > a) Run indefinite on the ground - like long waiting cues on taxi
> ways, any
> > wind direction
> > b) Support a min 1 min full power run-up
> > c) Support a min 5 min Max Power climbout at any possible speed
> (slower> being the worst....)
> >
> > I'd rather play with movable cowl-flaps, etc. than accepting
> that I might
> > not be able to pull full power at any point.
> >
> > What if you are already maxed out, because OAT is high, you are
> heavy, in
> > a nasty turbulence and have to do an "emergency" climb out.
> > You have an engine, that *could *do it easily, ....if you *had
> *a system
> > that *would* cool it.
> >
> > Plan starts with rereading all cooling posts, get the
> calculator, get
> > familiar with heat transfer tables, plan on spending some
> serious money for
> > custom coolers....
> >
> > Plan is to built for the worst case. I always can reduce cooling....
> >
> > Thomas
> >
> >
> >
>