HEAD WIND VELOCITY,  KNOTS  MOST ECONOliTCAL AIR SPEED, KNOTS  K-3  thru K-8  K-9 and Future  10  46.0  42.0  15  20  46.0  42.0  25  43.5  30  49.0  50.0  35  51.5  56.5  40  56.0  62.•5  45  58.0  64.0  50  Fig. XXV  Economical Air Speeds  -67-