Quote:
Originally Posted by nolimitfiend
How much distance is required for the various airliners to make turns? i.e. how tight of a turning radius is possible for various things, such as, downwind and base legs, go-rounds, 180 degree turns, etc...?
For airspeeds below 250 kts, we make turns at a rate of 3 degrees per second, i.e. a full 360 degree turn would take 2 minutes. This is called a Standard Rate turn.
Because the angle of bank required to achieve a standard rate turn is directly proportional to airspeed, we use a half standard rate for high airspeeds (above about 250 kts). The increased bank angle needed for a standard rate turn would result in noticeably higher G forces.
[The G force in a level flight turn is given by 1/cos(angle of bank). Thus, for a 60 degree bank level flight turn, the G force is 2.]
The SR-71, cruising at Mach 3+ requires about 100 nm to complete a course reversal. The radius required for a standard rate turn is given by:
When we practice diversions from the North Atlantic Tracks in the simulator, it takes just over 15 nautical miles for a course reversal at our cruise speed, i.e. by the time we are pointed in the opposite direction, we are just over 15 nm from the airway we were just on (that would be a little over 17 statute miles).
The only place where knowing your turn radius becomes something really nice to know is in the approach environment, when flying to intercept a perpendicular course line. A good rule of thumb in this case is to start the turn at a distance equal to 10% of groundspeed. So if we are at 200 kts, we start the turn inbound at 2 miles from the extended course centerline.
When making the turn from base leg to final, we are usually at around 180 kts, so we would be leading the turn by about 1.8 nm.
Last edited by W0X0F; 06-19-2014 at 07:37 AM.