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Scott, Johannes, et al,
To add another set of data to the cooling analysis/discussion, here are some pressure measurements from yesterday. I took an extra airspeed indicator plumbed to a three way manifold. I could select from probes in the plenum above engine, at the cylinder exits, or the cowl exit. The static port was plumbed into the aircraft static system. Before taking the flight data, I calibrated both the extra airspeed indicator and the aircraft airspeed indicator with a water manometer. The aircraft ASI was reading low by about 2 knots across the entire speed range. The test ASI (non TSO'd variety) had a large excursion in the mid range, reading as much as 6 knots high. The data below takes both calibration curves into account.
The difference between the engine exit and the cowl exit is small, but certainly measurable.
Chris
cal. cal. cal.
cal. above below cowl
aircraft engine engine exit dP across
IAS pressure pressure presure engine
(kts) (inH2O) (inH2O) (inH2O) (inH2O)
90 3.6 1.4 1.4 2.3
100 4.8 1.5 1.4 3.3
110 5.6 1.6 1.5 4.0
120 6.5 1.6 1.5 4.8
130 7.4 1.8 1.6 5.5
140 8.1 2.0 1.8 6.1
150 9.0 2.2 1.9 6.8
160 9.9 2.5 2.1 7.4
170 11.2 2.7 2.4 8.5
180 13.1 2.9 2.7 10.2
190 14.6 3.2 2.9 11.4
200 16.3 3.7 3.2 12.6
Chris Zavatson
N91CZ
360std.
www.N91CZ.com
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