J.P. Instruments EDM 930 Primary Pilots Guide User Manual

Page 29

For Your Safe Flight

Page 24

LeanFind Procedure—General Explanation

Lycoming and Continental established specific restrictions on
leaning that must be followed, such as percent power, climb
leaning, and TIT limits. Lycoming recommends operation at
peak of EGT at 75% or less power only. Continental
recommends operation at peak EGT at 65% or less power
only. This guide does not supersede specific
recommendations of the engine or airframe manufacturer. It is
your responsibility to know your aircraft’s limitations.

Pre-leaning: The leaning process typically begins with ‘pre-leaning’ to
insure all cylinders are operating rich of peak EGT (note: you can
optionally activate ‘Normalize’ - hold

until

NRM

appears - making it

easier to confirm all EGT’s decrease). Now enrichen the mixture to
achieve a 50° drop on the hottest EGT. Insure that all EGT’s decrease.
Wait one minute to allow temperatures to stabilize.

Lean Find-Initiation: The leaning process typically begins with ‘pre-
leaning’ to insure all cylinders are operating rich of peak EGT. This is
accomplished as follows. As you lean the mixture watch the hottest EGT
and note when it begins to decrease in temperature. Now enrichen the
mixture to achieve a 50° drop on the hottest EGT. Insure that all EGT’s
decrease. Wait one minute to allow temperatures to stabilize. Note:
When the first EGT peaks, you can optionally activate ‘Normalize’ -
hold

until NRM appears - making it easier to confirm that all EGT’s

decrease.

Lean Find-Initiation: Initiate the EDM leaning mode by tapping the

button. Note that the EDM displays its current leaning mode
momentarily:

‘ROP’

for operating Rich of Peak or

‘LOP’

for operating

Lean of Peak. To change, simply hold

STEP

and

until the display

shows the other mode. The EDM is now waiting for a 15° rise on any
EGT (this feature significantly reduces false peaks). Lean the mixture
without pausing to achieve about a 10 deg per second change. With the
vernier mixture control, turn the knob about a quarter turn every second.
With the non-vernier or quadrant mixture control, lean slowly and
smoothly about 1/16 inch every five seconds (note: leaning accurately
with a quadrant system is difficult due to its mechanical linkage).