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

Wed Aug 19 09:23:15 CDT 2009

Terry,

Three weeks ago, I flew into CO into JeffCo, aka, Jefferson County, aka Rocky Mountain Regional, aka Metropolitan, aka BJC.  After a 'wild ride' through the mid afternoon wind and turbulence dropping down off the mountains and nearby thunderstorms and virga, I was relieved to pull off the taxiway onto the ramp to head to the FBO.  As I reduced rpm, the engine started running real rough so I kicked on the booster pump (SOP on the flat land to add pressure to the fuel to overcome the tendency to vaporize the fuel because of heat in the overhead injection lines) on the IO-540, which promptly killed the engine.  I then remembered where I was at and the high 90F temps.  I restarted the hot engine (thanks to Odyssey and B&C) by pulling the mixture off until the engine caught and then ran with the mixture partially leaned for satisfactory ops.

I was number three for Jeffco after a wild ride through the turbulence east of DEN.  The turbulence seem to abate a little as I sat up for a right base, though another TS show was crossing the far end of the field.   Both the Cessna and Cirrus ahead of me report smooth air for landing.  Did I mention, things can change real quick?

After making an adequate landing (considering everything) and advising the tower that they could cancel the 'smooth air' advisory, I taxied to the ramp where a lineman signaled me into place (after the restart, right in front of the tower, mentioned above).  I cut the engine and reach around to gather up some stuff---when I looked up, I was starting to move across the ramp.  The wind was blowing like Hades out of the NW.  We got things tied down and the lineman gave me a ride to the FBO.  He said this was common for mid afternoon as the TS develop, even though it was just spotty cells, and the wind comes down off the mountain, then toward late afternoon/evening, it dies back down again.  A King Air landed right after me and the pilot came into the office and remarked, 'well, that was certainly fun'.

Since I wanted to fly from DEN to Knoxville, TN in a single leg, I topped off both tanks, but I was alone. From the postings on here by Kurt, Scott and other 'high flyers', I remembered to calibrate my mixture during run up to account for the density altitude, which was something in the double digits.  It's kinda spooky to take off and look down a couple minutes later and realize a person is already above 7000'.  The high density is when I fully appreciate the 300HP version of the 540.  It really wasn't doggy, but it certainly didn't climb like an F-15 on departure either.  On landing, I really didn't notice any difference because I was light and headed into a 'brisk' headwind, so landing distance was meaningless.

Terry, I would think (but don't know) that the 4800 foot of runway should be ample, especially if the temp isn't into the 90s, though just to be sure, it might be okay to have the passengers leave their steamer trunks behind and not top both sides off.  Happy flying and make sure you have all of the current DEN plates, particularly the departure procedures.  If you depart VFR, there's obvious some interesting vectoring if you are crossing the DEN airport area.

Chuck Jensen 

Diversified Technologies 

Thanks,
Chuck Jensen

Diversified Technologies
2680 Westcott Blvd
Knoxville, TN  37931
Phn:    865-539-9000 x100
Cell:    865-406-9001
Fax:     865-539-9001
cjensen at dts9000.com

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Terry Miles
Sent: Tuesday, August 18, 2009 11:35 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Leaning at High DA Airports;was Re: Static RPM
Question

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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