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To: flyrotary@lancaironline.net
Date: Tue, 15 May 2007 16:01:13 -0700
Subject: Re: [FlyRotary] Marginal Cooling contributes to Crash.
Message-ID: <20070515.161008.1820.5.alwick@juno.com>
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From: al p wick <alwick@juno.com>

I know it's a tough sell. Hard to believe you have significant risk when
you are normally able to just throttle back, wait a while, and temps
start to drop. Tons of times I heard the same response in my
occupation...."If he just reacts to xxx, then the problem goes away".
Marginal systems place you closer to the boil over temp. It only takes a
20F rise in ambient temp to affect marginal system. It takes 80F rise to
affect robust system. If you heat soak a marginal system, that places you
right on the edge of boil over. Add a bubble of air to marginal system,
you are screwed. As your temps rise, your piloting skills drop off due to
anxiety. I've gotten a number of reports from guys who landed gear up
even though their warning horn was blasting away...just because they were
worried about the engine behavior. 

The incident I referred to was the guy that took off with marginal
cooling. Landed at Whyoming airport, changed to Evans, then took off and
bit it. Underlying root cause was marginal cooling. He never would have
changed to Evans if he had started out with robust system.

Our day to day problem solving skills set us up for failure. We are so
used to making marginal decisions, that we find it difficult to see the
significance of robust design. Easy to fly for years with marginal
system, then all of a sudden the other contributing factors stack against
you.......
High ambient temp, high altitude, heat soaked engine. Fortunately,
statistically it will only nail a few guys. A few for marginal cooling, a
few for marginal fuel delivery. One common cause....sys designed too
close to failure point.

Certainly agree, spray bar a good solution. 

-al wick
Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam
timing. 
Artificial intelligence in cockpit, N9032U 240+ hours from Portland,
Oregon
Glass panel design, Subaru install, Prop construct, Risk assessment info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html


On Tue, 15 May 2007 15:10:12 -0400 "Ed Anderson"
<eanderson@carolina.rr.com> writes:
> Hi Al,
> 
> I would be interested in these other factors you mention referring 
> to the 
> crash.  I have years of flying under cooling deficit conditions 
> right after 
> take off  as do others as you mention - without any problem.  Every 
> study I 
> have read on cooling indicates the designer strives for an optimum 
> cooling 
> system- for an operating regime - (frequently for the cruise regime) 
> and 
> then uses whatever, cowl flaps, exhaust augmentation, spray bars,  
> to cool 
> it under less than ideal conditions-  like immediately after take 
> off.  I 
> understand even the P51 faced that problem on taxi and take off on 
> hot days.
> 
> You can certainly design your system to not have a "take off" 
> cooling 
> deficit but, you are now starting to talk bigger radiators (may have 
> space 
> constraints), more weight, cooling drag, etc. for some airframes and 
> flight 
> regimes a bit more would not be significant, but for other airframes 
> and 
> speeds these factors become more significant.
> 
> Perhaps we need to be as bit more specific as to what degree of 
> "overheating" we are referring to.  My limit on oil temp is 200F, my 
> limit 
> on coolant is 220F and those only for the short duration of launch 
> and up to 
> 120 MPH IAS at which time my system is on the good side of cooling. 
> 10 years 
> of flying with that limitation has not yet revealed any problem so 
> far as I 
> can tell. Now with a rotary,  if your temps are going 240F on oil 
> and 
> similar on coolant then I personally would feel that is too high and 
> 
> something should be done.
> 
> A crash to which the overheating was apparently one of a set of 
> factor is 
> certainly something that I would be interested in.  How bad was the 
> 
> overheating and how did it contribute to the crash?  I (and I 
> believe all of 
> us) would be interested in the details of the crash you mention that 
> was 
> contributed to by marginal cooling - for lessons learned.  A spray 
> bar does 
> indeed provide a considerable margin, Tracy flew with one for a bit 
> (mainly 
> for racing I believe), I've never experimented with one since I 
> don't go 
> racing and once airborne and 120 IAS and my system is happy.  
> However, it 
> might be interesting to see exactly how much benefit such a simple 
> system 
> would provide.
> 
>   Gotta put that on my long list of  "to do" things.  Another thing 
> I have 
> been thinking more about is that my GM cores which have served well 
> are 
> approaching the 10 year point.  They are really not designed for 
> water flow 
> as we know, so  I would not be surprised that a custom made set of 
> radiator 
> cores might lower my coolant temps by 5-10F by simply providing 
> improved 
> coolant flow.
> 
> As always, appreciate your input and perspective, Al.  Any risk we 
> can 
> eliminate or reduce is worth examining and taking action on.  Again, 
> would 
> be interested in the details of the accident if you have them.
> 
> Best Regards
> 
> Ed
> 
> 
> 
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "al p wick" <alwick@juno.com>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Tuesday, May 15, 2007 12:08 PM
> Subject: [FlyRotary] Re: First Flight - Renesis in RV-7A
> 
> 
> >I know a lot of you guys are flying with conditions similar to what 
> Ed
> > describes. It gets hot during climb, but cools off during cruise. 
> It
> > seems manageable. I encourage you to not tolerate such a design. 
> This is
> > a root cause for crashes. You have marginal system, normally 
> easily
> > managed, but suddenly other factors come into play.  We had crash 
> last
> > year with marginal cooling as one of the root causes.
> >
> > One simple solution that provides extra safety margin is to just 
> add a
> > spray bar in front of radiator. It just takes a tiny mist of water 
> to
> > dramatically improve cooling. Strongly encourage spray bar at a 
> minimum.
> > Great solution for initial testing.
> >
> > Even then, I would seek improvements that eliminate need for spray 
> bar.
> > There are simple improvements out there. There are guys flying 
> exact same
> > hp as you, yet they have 10 to 20% better cooling efficiency. Find 
> out
> > what they are doing right.
> >
> > If you had everyone flying record their temp as they climb out 
> from sea
> > level to 12k ft, you would find a couple guys with better 
> efficiency than
> > the others. You'd have to record outside air temp. Coolant, oil 
> temp at
> > start and end of climb. Everyone would have to climb at same rate, 
> say 80
> > mph, then 90mph. Compare area of radiators. With some facts like 
> this you
> > could end up with some genuine breakthroughs. Speculations do not 
> lead to
> > breakthroughs.
> >
> >
> > -al wick
> > Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and 
> cam
> > timing.
> > Artificial intelligence in cockpit, N9032U 240+ hours from 
> Portland,
> > Oregon
> > Glass panel design, Subaru install, Prop construct, Risk 
> assessment info:
> > http://www.maddyhome.com/canardpages/pages/alwick/index.html
> >
> >
> > On Tue, 15 May 2007 07:47:09 -0400 "Ed Anderson"
> > <eanderson@carolina.rr.com> writes:
> >> Congratulations, Dennis.  A great day for sure!  A lot of work 
> and $$
> >> coming
> >> to successful launch.  Unless you make the cooling system 
> capacity
> >> considerably greater than you need at cruise, you will always run 
> a
> >> cooling
> >> deficit during climb - high power, low airspeed.  So long as it
> >> doesn't
> >> exceed your limits and cools off once sufficient airspeed is 
> reach,
> >> you
> >> should be fine
> >>
> >> Ed
> >> ----- Original Message ----- 
> >> From: "Dennis Haverlah" <clouduster@austin.rr.com>
> >> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> >> Sent: Monday, May 14, 2007 10:23 PM
> >> Subject: [FlyRotary] First Flight - Renesis in RV-7A
> >>
> >>
> >> >I made my first flight this evening!!  All systems worked fine 
> -
> >> cooling
> >> >was marginal in climb but we had a good inversion and the 
> outside
> >> air
> >> >temperature was quite warm.  Several neighbors videoed the 
> flight
> >> and I
> >> >heard several comments about how quiet the rotary plane was when 
> we
> >> played
> >> >the video.  We had a 180 hp RV-7A flying chase and on the video 
> it
> >> was much
> >> >louder!!  Only flew about 10 minutes but made an acceptable 
> landing
> >>
> >> >considering there were about 50 people watching.  I'll post 
> some
> >> picures of
> >> >the plane later tonight.
> >> >
> >> > Dennis Haverlah
> >> > RV-7A, Renesis, James Cowl
> >> > Radiators under engine
> >> > Catto 76 in dia- 8 in pitch
> >> > EC-2, Em-2, RD1-C
> >> >
> >> > --
> >> > Homepage:  http://www.flyrotary.com/
> >> > Archive and UnSub:
> >> > http://mail.lancaironline.net:81/lists/flyrotary/List.html
> >>
> >>
> >> --
> >> Homepage:  http://www.flyrotary.com/
> >> Archive and UnSub:
> >> http://mail.lancaironline.net:81/lists/flyrotary/List.html
> >>
> >>
> >
> >
> > -al wick
> > Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and 
> cam
> > timing.
> > Artificial intelligence in cockpit, N9032U 240+ hours from 
> Portland,
> > Oregon
> > Glass panel design, Subaru install, Prop construct, Risk 
> assessment info:
> > http://www.maddyhome.com/canardpages/pages/alwick/index.html
> >
> > --
> > Homepage:  http://www.flyrotary.com/
> > Archive and UnSub: 
> > http://mail.lancaironline.net:81/lists/flyrotary/List.html 
> 
> 
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   
> http://mail.lancaironline.net:81/lists/flyrotary/List.html
> 
> 


-al wick
Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam
timing. 
Artificial intelligence in cockpit, N9032U 240+ hours from Portland,
Oregon
Glass panel design, Subaru install, Prop construct, Risk assessment info:
http://