FAQ #404
Micro Class 2027 - Free Airstream

Last Updated On 10/22/2026 10:50:20 AM by

talmadge33

Question
We would appreciate some further clarification regarding the requirement for the external drag article (DA) to be exposed to freestream airflow.
Answer
Positioning a Drag Article immediately behind the propeller (in the slipstream) or behind nose landing gear (in the wake) would likely not meet the free airstream requirement in Section 9.3.3. Large downstream separation combined with angle of attack may mitigate. If challenged, it is your job to demonstrate (through analysis or testing) that the drag article encounters freestream airflow (at your cruise angle of attack). This might be a good topic to address/demonstrate in your written design report.
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Rule Numbers
2027:2027.9.3.3