George, et al,

 

Finally, on Sunday I was able fly after some unexpected maintenance on my nose gear.  Because of time limitations and other conflicts, I was able to only do a short run although simulating the altitudes used by the pilot with the "failed" engine.  In preparation for the test, I obtained a digital tape-less voice activated recorder and plugged it into the intercom headphone output - Voila!  A cockpit voice recorder. I don't have to write anymore, just talk to myself - something I am used to doing.

 

Remember my engine is an I/O 320 with a 9:1 CR and a ram air recovery system.  I climbed to 8500 MSL and leveled out (7C OAT, 29.44 Hg Baro) operating at WOT, 22" MAP, 2500 RPM.  Cyl #1 leaned to peak @1390 EGT and 7.6 GPH.  Adjusting the mixture LOP to 1370 EGT and 7.4 GPH, The cruise looked like this:

 

167 KIAS, 193 KTAS, 22.6" MAP, 2490 RPM and 27 DBTDC with a temp spread:

 

  CHT  EGT

1 350  1370

2 360  1400

3 360  1400

4 370  1400

 

From here on out only Cyl #1 is monitored with the RPM at 2500.  The throttle was closed to 17" MAP and a spiral descent was begun near an airport at a rate of 1500 to 1000 FPM (timing  to 32 DBTDC). 

 

At 5500 MSL and 188 KIAS, 18.5" MAP, 290 CHT, 1280 EGT, 4.9 GPH and 31 DBTDC.  Throttle to 17" MAP

 

At 4000 MSL and 196 KIAS, 17.5" MAP, 280 CHT, 1290 EGT, 5.0 GPH, and 31 DBTDC.  Throttle later moved to 17" MAP.

 

At 3000 MSL and 185 KIAS 17" MAP, 270 CHT, 1310 EGT, 5.2 GPH.

 

At 2000 MSL, slowed to 150 KIAS, 17"MAP, 270 CHT, 1340 EGT, 4.7 GPH, Oil Temp 155F.  Then, throttle moved to 27" MAP.

 

At 2000 MSL, Aircraft speeding up, 27" MAP, CHT?, 1370 EGT, 8.3 GPH, 25 DBTDC.

 

The throttle was moved back to 25" MAP and the mixture adjusted to 10.4 GPH, about 182 KIAS, CHT 350-360, EGT 1300-1310.

 

There was no stumbling or engine difficulty indicated at all when the power was applied. 

 

I will repeat this test several times including ROP.  I must, because most of my flying is done ROP and I could probably descend differently than I do now.  Currently, I reduce power  by MAP reduction rather than RPM reduction because I get vibration below 2300 RPM.  This power regime is probably not good for the engine.  I continue to reduce MAP because the power increase (natural MAP increase from higher speed and descent) changes the speed and pitch too much.  I tweak up the mixture to stop the EGTs from climbing.  At low power, this may not be necessary.  Just remember the usual rule for increasing power is to work the knobs from right to left - Increase mixture, prop and throttle in that order.

 

Anyway, I waited 'til after testing to re-read Deakin's 2003 AVWEB article (.....Part 4 -- Descent).  Below is the summary from that article followed by the URL.

 

Summary

Use full power on all takeoffs, with a "rich enough" mixture. FORCE your mechanic to set that fuel flow high enough to get roughly 1300 degrees EGT or a bit less, and CHTs in the low to middle 300s.

If you have that full-power mixture set properly, determine your "target" EGT right after takeoff, and lean in the climb to keep that same absolute value on the digital EGT. As you climb, that EGT will drop a little. Lean until it comes back up. Drops a little, lean and bring it back up.

For cruise, first determine your range needs, and set a power setting to maintain the AIRSPEED that will do the job you want. Set WOT, then the RPM and mixture you need to maintain that. LOP is much better, if it will do the job, but use ROP if needed. Cruise outside the red box, or at worst, on the fringes of it.

For descent, use mixture control and RPM to get the desired descent, switching to slightly rich of peak EGT, if you wish to keep the CHTs up. (Remember, 50 ROP on the EGT may be the same absolute value of EGT as 50 LOP, but the CHT will be much hotter when 50 ROP!) .........

 

 

It would be wise to read all four. 

 

OK, give me a break..  I'm working on it.  Some day I'll get it all together.  At least I climb in the manner he indicates.