lml@lancaironline.net Mailing List Archive

In a message dated 12/29/2005 9:12:10 A.M. Central Standard Time, marv@lancaironline.net writes:

George,

Could you gather a little data for me?

Sure.

I know that the big bore TCM engines - - if set up properly LOP at high
power at altitude, will always operate nicely with no mixture
adjustment after a long descent.

Hmmm... At 2500 RPM and pulling back to 17-19 inches (maintained thru the descent), I always twist the Mixture vernier for a bit more fuel every few thousand feet as the EGTs change (rise) in a 400+ fpm descent that forces me to operate at 190-210 KIAS with ram air pressure greater than it was at cruise. Usually, when I level off, the mixture will be just about right to either finally slow down or reapply power back to 25" MAP.

But I don't have any recent experience (I owned a Mooney for 1500 hours
- - years ago <g>) with the fuel system on the Lycoming engines. What
happens to your engine if you have it well LOP at altitude and then
descend without adjusting the mixture and power up after a 10 or 15K
foot descent ???

Hmmm.... OK, at the next opportunity, I will perform a constant speed (135-140 KIAS) climb to 12000 feet (away from ORD), set up cruise at 30-40 LOP, and descend (say 500 fpm or so, I don't have TRU-TRAK) as you requested unless something exotic occurs - I will be writing furiously during this exercise unless the traffic alerter starts to nag at me. For those interested, I will be reporting LSE timing also.

Scott Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

Happy New Year to all!