Kirk Harrell's Mustang II - N22YR
Updated February 18, 2008
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On July 21,2002 MII N22YR had the flap fail on the air
diverter in the plenum box and the flap closed off the
injector servo, effectively choking the engine. In
the ensuing off airport landing the Hartzell prop was
destroyed. Airframe damage was limited to a slightly
sprung right gear leg and a small ding in the left
wing leading edge.
Since the Lycoming IO360-B1E had 1,500 hrs, it was
majored. All reciprocating parts were static balanced,
and piston and valve faces were ceramic coated.
The engine mount was rebuilt to reposition the engine,
and a new MT MTV-15 aluminum propeller with 4"
extension on the hub replaced the damaged Hartzell.
These changes necessitated a new cowl.
A new stainless 4 into 1 exhaust system was fabricated
using the EAA Cafe Foundation EPG data as a guideline
for optimum primary and collector tube diameter and
length. The system also incorporated anti-reversion
cones as outlined in Kent Paser's book "Speed with
Economy". After fabrication was completed the system
was ceramic coated inside and outside to keep heat in
the exhaust gas and out of the engine compartment.
The offending air plenum flap was replaced with a
double wall 4130 replacement flap, and the velocity
stack was modified to port match with the intake servo
opening. A NACA scoop was incorporated into the cowl
that is sized for open throttle 2,700 rpm @ 230 mph,
with an opening of about 3.5 sq. inches, but works
well even on takeoff at full throttle 2,700 rpm and
105 knot Vy.
The MT prop is very smooth, and quiet. It does not
have RPM restrictions like the Hartzell.
The cooling system was upgraded to include a separate
plenum for the engine, which allows better control of
diffusing inlet air. The system is still undergoing
some adjustments to get cylinder temps up to 380 -
390F in cruise. The annular inlet ring is fixed to
the plenum with a silicone baffle seal ring, and nests
in the cowl opening. This aides in getting a perect
seal while allowing engine movement, and also allows
modifications to the inlet opening size without
messing up the cowl.
While N22YR was down, the instrument panel was
upgraded to include PM1000 intercom and an artificial
horizon. Servo driven spring bias aileron trim was
installed. New upholstery was installed. The canopy
clamping mechanism was modified and beefed up to hold
the canopy tightly closed in all phases of flight, and
has proven to be one of the best mods during the cold
As of February 18, 2008 N22YR has logged 35.5 hrs
since mods were completed. The GPS odometer totals
5,802.1 nautical miles travelled (which includes all
taxiing as well as flight miles). Except for approach
and ground time, all flight has been performed at
breakin power settings of 24 - 25 inches manifold
pressure and 2,400 to 2,500 RPM.
N22YR is an absolute delight to fly, and now with
aileron trim and balanced engine, is smooth and nearly
a hands free bird, even without autopilot.
Some more links to photos of Kirk's airplane: S-N-F 2002 and here
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