More Performance Modifications
Mustang II Experimental Airplane N727RH

Updated July 16, 2004
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These photos incorporate deviations from the plans.
Use of this information for Your aircraft is obviously AT YOUR OWN RISK.

Modifications in progress

This page will be a 'work in progress' to share what I'm doing with modifications. On July 3, 2004 I started an attempt to reduce cooling drag by reducing the original Twin Comanche cowl inlets by 33%. Original openings totaled 55 inē, now at 36 inē. They are filled with balsa, foam and tape for trial purposes.

My goal with these modifications is to maximize the 75% power cruise at 2400 RPM (near 8,000' DA) - currently at 166 KTAS, while still being able to climb and cruise at 17,000' when tailwinds favor that.

Reduced cowl openings
Reduced cowl
openings
Previously 55inē,
now 36 inē
(107 KB)		 Top of climb at 17,000'
Top of climb
at 17,000'
GW=1509#
Climb power =
full throttle (15.0")
2500 RPM
(138 KB)		 Cruise at 17,000'
Cruise at 17,000'
IAS 107 K, TAS 144 K
FF= 6.2 GPH, OAT= -2.7°C
DA=18,900'
(136 KB)		 Cruise at 7,000'
Cruise at 7,000'
IAS 145 K, TAS 166 K
FF= 8.8 GPH, OAT= +17.6°C
2400 RPM, DA=8,900'
(Above optimum Density Altitude)
(133 KB)
The primary purpose was to collect CHT and oil temperature data to confirm that the reduced inlets would not over-temp the engine. They were normal even though the atmosphere was ISA +13° at sea level (28°C).
Cruise data was collected at 17,000'; 15,000'; 13,000'; 11,000', 7,000' and 6,000'.
I erred by reducing the throttle at 6,000' to set MP for 75% cruise for a standard day: 23.1" MP, when I should have corrected for the non-standard temperature by running at 23.6" MP - just about full throttle - which would have been very close to the optimum density altitude for a 75% power setting at 2400 RPM.
I estimate that approximately one more knot would have been achieved if I'd collected 75% data at the optimum altitude.
New data will be collected when the fiberglass work is complete, which should smooth the flow into the engine somewhat.
Plans are to also reduce the cowl flap outlet area and later, add exhaust nozzles.

"To be continued..."

Other links:

Previous modifications page (canopy / windshield in 2001)

"Speed with Economy" - the inspiration for these modifications:

SPEED with Economy

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