REFLECTOR: Leaning at High DA Airports; was Re: Static RPM Question

Terry Miles terrence_miles at hotmail.com
Tue Aug 18 22:34:41 CDT 2009


Dear all,
Well I want in on this thread too.  It comes at a perfect time for me.  I am
planning a trip to APA which just S of DEN.  Fld Elv 5800.  Runway is nice a
long so that is not an issue, and I know to lean to peak and then enrich
back to +100 or so cooler.    

Here's the thing...While I am there, there is a fly in to KLMO which a
little NW of DEN.  Fld Elv is 5100 or so.  Rnwy length is 4800 x 75.  Temps
have been running in the 70's so I will estimate a DA of maybe 7000.  If I
said an XL w/ 3 people had a sea level take off run of 1200',  then the KLMO
takeoff run is going to be just under 3000 in calm winds.  I have been
watching DEN metar for a week now and in the afternoon hours they get is
cumulus build ups with virga reported and all hell breaks loose for big wind
shifts and big gusts. There is a small airshow that day.  I have to get in
by 1100L and stay until at least 1530L or so before they open the runway up
again.   

I have the 300 HP Lycoming, but my concern is coming up with a rule of thumb
on landing distance.  The landing runway is 29.  Let's say the fld temp is
75 and the winds are 250v330 10G17 (there is no weather reporting on the
fld). (Read I am getting thrown around pretty good in turb and the engine
response is sluggish compared to what I am used to.   If I said my personal
minimum runway length for my skill level with that wind report is 3000, what
should it be when DA is 7000?  I am thinking it ought to be more like 6500
for min runway length and 4800 is cutting close.  

I admit it.  I am a flatlander.  Do any of you mountain people have some
advice.  Does anybody have a rule of thumb for this?  The Koch chart really
only talks about tkof and climb and not approach and landing  

Thanks
Terry

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Tuesday, August 18, 2009 17:05
To: Velocity Aircraft Owners and Builders list
Subject: REFLECTOR: Leaning at High DA Airports; was Re: Static RPM Question

Never ever forget to lean a non-turbo charged airplane at high density
altitude airports!!  We have two crashes at GNT in 10 years that probably
would not have happened if the pilots had leaned the engine.

I was there for one and kept thinking "Lean it out! Lean it out!" but he
crashed instead.  The engine will run like SHIT, if you don't! 

In the summer afternoons in northern NM, just about every airport is above
8,000 DA, and some like GNT are pushing 10,000.  The DA is so high you can't
hurt the engine with full power and lean to max RPM, because the engine is
making way less than 75% power. 

If your a bit paranoid about it or DA is 6-8K, lean to best RPM, then richen
to get about 25-50 RPM drop., no more than that though.  Once your 500-1000
above ground level you can richen the mixture some to get some cooling if
you need it. Better yet go to 75 LOP and get your cooling that way!

Scott

nmflyer1 at aol.com wrote:
> Thanks for reminding me Doug,
>  
> I automatically lean for takeoff out of habit. I forgot some 
> flatlanders (no offense) don't have to do this.
> Make sure you lean properly for takeoff at higher density altitudes 
> (your engine manufacturer will have recomendations). It can mean a BIG 
> difference in power. In some cases I have heard aircraft that takeoff 
> without leaning actually lose RPM right after they lift off due to the 
> cylinders slowly loading up with fuel.
>  
> Kurt
>
>
>




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