Mixture on app to high fields

[380]

You descend from 10000ft or above and want to land at a field at 5600ft(Guess which one, I think ir's the highest in Europe. During the descent you gradually enrich the mixture. Then you're on downwind and do the app check. QNH,lgd light... blah... blah, mixture rich! Hmm? How rich? Full rich? In the AFM there is written, at fields abv 3000 take off with best power. But on a downwind you won't have time to find peak-20F(or whatever is best pwr). But I'd like to have best power for the best G/A performance.
So, what would you do in such a situation?

[Tinstaafl]

Leave it at whatever mixture setting you have at bottom of descent.

In my experience this tends to be somewhat richer than a correctly leaned mixture for that D.alt.

On the go-around monitor EGTs & adjust the mixture.

At high altitude you are only likely to achieve something less than Max Continuous power, let alone Maximum Power. Full rich is not likely to be needed for cooling.

Next time you fly, or on the trip to this aerodrome, note the maximum power available as you climb throught the aerodrome's altitude.

If this is less than or equal to the approved power setting for leaning (typically 75% or less)fthen full rich won't be necessary.

NB: This presumes a normally aspirated engine. Turbocharged engines can developed full power up to rated altitude so Full rich is going to be necessary for full power!

For the turbocharged types I'd leave the mixture at the bottom of descent setting & then go to full rich just prior to advancing the throttle to apply full power.

[aztruck]

on a hot day into Reno nevada in a normally aspirated baron some years ago I had exactly the same dilemma. As I retarded the throttles to idle after touchdown the right engine promptly died. Not much you can do except leave them alone and enrichen slightly if they start to run a bit rough.
Egt helps of course-as long as it works!

[Tinstaafl]

Barons & Bonanzas have approximate mixture settings for 3000, 5000 & 7000' for Climb power (25"/2500rpm as I recall) calibrated on the FF gauge**

Makes it very simple to set an approximate mixture for that particular power.

Wish all the manufacturers did something similar.

--------------------
** 'gage' for our American readers :)

[380]

Thanks for the answers

380

[Ham Phisted]

C310B I've been flying lately has approx pressure altitude settings on the mixture levers. I haven't got the mental capacity to check whether they're helpful or not but it does assist in setting mixture.

[411A]

All fuel injected twin Cessnas have the fuel flow gage* marked for the power setting required. Remember however that this is a pressure instrument rather than a flow gage* and not all that accurate unless properly adjusted.

*"gauge" for our European friends.

[Tinstaafl]

I had forgotten about the Cessna injected twins have the same gauge* setup. Piper injected types don't seem to do it.

I wonder if it's a Continental vs Lycoming thing?

*gugea for our dsylexic readers

[This message has been edited by Tinstaafl (edited 27 May 2001).]