Buckaroo's Flightgear Projects
Guide To YASim: Contents

Tests of the YASim Flight Surface "idrag" Attribute

By Gary "Buckaroo" Neely

Test Conditions

Aircraft used in the tests:

Optica, DHC2, A-10, A6M2b, A4

Parameters used for the tests:

Alt: 500'
ASI: 50 kts (Optica), 60 kts (DHC2), 120 (A-10), 100 (A6M2b), 180 (A4)
AoA: ~6.4 (Optica), ~8.3 (DHC2), ~12 (A-10), ~3 (A6M2b), ~11+ (A4)

These profiles are meant to produce slow, relatively high angle of attack flight where induced drag should be a significant factor.

Heading, wind and aircraft configuration were constant for all tests.

The test consisted of determining throttle settings necessary to hold the above conditions using three different wing idrag values. The first test used the default idrag value of 1 (except for the A6M2b which uses 1.25 as its default setting. The second test used an idrag value of approximately 83% less than the default. The third test used a idrag value approximately 20% greater than the default. Throttle settings are expressed as percent of maximum throttle.

Test Results

idrag       Optica     DHC2     A10    A6M2b               A4
-----       ------     ----     ---    -----               ---
1(default)  28%        15%      34%    16.7% (idrag=1.25)  33%
0.83        35%        19%      40%    19.3% (idrag=1)     38%
1.2         22%        11%      27%    14.7% (idrag=1.4)   27.5%


Decreasing idrag from the default settings resulted in increased throttle requirements at slow, relatively high AoA flight. Trials using idrag values greater than the default resulted in decreased throttle requirements. This is the opposite of what is expected based on YASim documentation.