Text in force at CS25-28: from CS25-0, effective 17 Oct 2003.
(a) A vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed.
(b) If there is a swivel, the tail wheel is assumed to be swivelled 90º to the aeroplane longitudinal axis with the resultant load passing through the axle.
(c) If there is a lock, steering device, or shimmy damper the tail wheel is also assumed to be in the trailing position with the side load acting at the ground contact point.
ED Decision 2003/002/RM · Source