REFLECTOR: Speedbrake, descents, and shock cooling.

Fri Mar 16 09:10:38 CDT 2007

Hi all,
Dear all,

This is a great thread for me.  I am in the throws of finishing my XLRG
with speed brake (IO540) and debating with myself about connecting the
rudders so to use them as further drag devices.  Thanks for the comment
Joel, I think Dave Sharfenburg (sp?) has his that way too.  I am guessing
they are great for pattern work, but hard to sustain in a cruise descent.
Any other comments on this?

I fly in the NE too and am concerned about being able to meet ATC demands
and have all the performance and flexibility I can get.  I have heard of
the evils of shock cooling at 50 CHT per minute.  In the below Deakin
refutes some of this...

John Deakin has a series at AVcom on engine care.  Here's the extract from
his article.  

(The first paragraph below is a quote he is refuting in another article
from Shell Oil. 

Shell guy quote:
"Another common cause of plug damage is through rapid cycling of the engine
temperature -- power off descents after cruise, or excessive leaning, which
rapidly increases exhaust gas temperature (EGT), are typical scenarios. As
we have covered before, Lycoming recommend that the rate of change of
cylinder head temperature should not exceed 50¢ªF per minute."

Deakin write this:
The data suggests otherwise, as I mentioned above. We know of no data that
supports the popular concept of "shock cooling." I am unaware of any hard
data that supports the 50¢ªF per minutes "limit." On the other hand, one
has to work pretty hard to get a 50¢ª degree per minute change in the CHT!
I think some have transposed this CHT change to EGT, erroneously adding it
to their self-imposed "limits." 

One pilot I know used to recommend not reducing manifold pressure any
faster than 1" every two minutes! Now that is "Fear of Shock Cooling," and
utterly ridiculous. 

Terry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of lawrence epstein
Sent: Thursday, March 15, 2007 10:58 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Speedbrake?

I am not flying a Velocity yet, but I can tell you that a speedbrakeis a
big 
advanatge if you fly IFR in the Northeast. We get "Slam Dunks" here all the 
time. YOu can say "unable" but then you spend a lot more time flying in 
circles waiting for an approach clearance. The advantage of a speedbrake 
(over flaps in a spam cam) is you can retract at any time without losing
any 
lift. On a pusher, also keeps the gravel off the prop ;-)

Larry Epstein

>From: "Chuck Jensen" <cjensen at dts9000.com>
>Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>Subject: Re: REFLECTOR: Questions for those already flying
>Date: Thu, 15 Mar 2007 13:13:45 -0400
>
>XLRG, no speed brake.  Advantage of no speed brake is simplicity, no
>inadvertant deployment or failure to retract on TO or go-around.
>Dropping the gear will get rid of altitude promptly if power is chopped.
>Besides, using the speed brake to dissipate altitude and speed is an
>energy waste.  Preplanning can make good use of both to get there faster
>while using less energy.  It's actually a pretty rare instance that ATC
>slam-dunks a person such that the brake is needed.  Even then, "unable"
>works equally as well.  Speed brakes seem to be very much a personal
>preference.  The best value I've heard of for the speed brake is it
>seems to cushion the nose area such that at touch down, the nose doesn't
>"plop" onto the runway as sharply.
>
>Chuck Jensen
>
>  -----Original Message-----
>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>Behalf Of Scott Derrick
>Sent: Thursday, March 15, 2007 12:09 PM
>To: Velocity Aircraft Owners and Builders list
>Subject: Re: REFLECTOR: Questions for those already flying
>
>
>I have an RG,
>
>I have a speed brake, use it most landings.
>
>I accidentally replied  about cabin heating to another posting on "oil
>cooler issues",  I'll repeat it again.
>
>I had a cold airplane in the winter.  Mainly due to two reasons.
>Inadequate sealing of the nose gear  mechanism and using the nose oil
>cooler as the cabin heater.  When its -20 outside, the nose oil cooler
>as a cabin heater is trying to raise the temperature at least 100
>degrees, 120/140 would be better if the plane is cold to start with. It
>just can't do it.
>
>I have a internal oil heated cabin heater now that will recirculate the
>cabin air which should be able to roast us alive.  Its not flown yet so
>can't say if y design works well or not.
>   .
>
>Scott
>
>
>Jack Prock wrote:
>
>	Hi,
>
>	A couple questions for those already flying...
>
>	If you didn't install a speedbrake, if you were to do it again
>would you install it?
>
>	If you did install a speedbrake, are you glad you did? Do you
>use it often?
>
>	I have heard that with RG's it is hard to heat the cabin at
>altitude and/or winter. If you could do
>	it again, would you still cut the NACA for the oil cooler? I
>have heard people using two coolers,
>	one near the engine to be used during the summer,  and another
>in the nose that
>	is used as a heater during the winter. Any thoughts?
>
>	Thanks,
>
>	Jack Prock
>
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>--
>
>-
>     Liberty means responsibility. That is why most men dread it.
>
>     George Bernard Shaw, Liberty

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