Figure 5. Computing Ground Speed with Crab Angle 10 Degrees or Greater

T-45C TS INav-08

Fuel, Weather, and Alternate Airfield Planning

83 KTS

Step 5

OPPOSITE

CROSSWIND COMPONENT

READ CRAB ANGLE (13)

Figure 5 (Part 2): COMPUTING GROUND SPEED

WITH CRAB ANGLE 10 DEGREES OR GREATER

As previously stated, for wind problems where the crab angle is less than 10 degrees, the headwind or

tailwind component is simply applied to the true airspeed to obtain groundspeed. With small crab angles,

this is very close to being accurate, any inaccuracy being too small to be concerned about. With crab

angles of 10 degrees or more, however, the error is large enough to require the use of the EFFECTIVE

TRUE AIRSPEED (ETAS) (Cosign Scale) for obtaining more precise groundspeeds.

365 KTS

Step 8

ETAS 365 KTS

MINUS

HEADWIND COMPONENT 35 KTS

= GROUNDSPEED 330 KTS

Figure 5 (Part 3): COMPUTING GROUND SPEED

WITH CRAB ANGLE 10 DEGREES OR GREATER

(2-02) Original

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