Difference in Stall Speeds
During the performance testing of a single engine airplane we found a significant difference between the 1 g stall speeds of two identical airplanes. The test items are single engine piston with a high wing and a conventional tail configuration. Both airplanes are equipped with an on board recording system and the with a boom. Both of the recording systems were calibrated. Therefore it is very unlikely that the difference is coming from the instrumentation. The difference is almost 4 kts which is almost 10% of the stall speed.
Does anybody have an idea what the main contributor of this difference could be?
Thank you very much for your help.