180 knots ground speed. For example, if the aircraft had a 10 knot headwind, the indicated
airspeed would have to be increased by 10 knots to maintain 180 knots ground speed. The
increase allows the aircraft to maintain mission timing.
The aircraft must also be crabbed into the wind to prevent drift off of desired course. This is
critical to all aircraft engaged in any type of navigation, but more so during visual navigation due
to the close proximity of hazards, threats, and ground obstructions. In general, remember this
simple rule: the slower the aircraft speed, the more drift an aircraft will experience over a set
distance. Moving slower between two points allows more time for the crosswind component of a
given wind to move you further off course.
For your T-6A training, the low-level chart will display wind compensations based on preflight
winds. This will allow a rough estimation of the required airspeeds and headings to maintain
course. In subsequent phases of your SNFO/SWSO training, this "winding" of the chart will not
be accomplished and all heading and airspeed adjustments will be managed while airborne.
502. GROUND PROCEDURES, ROUTE ENTRY, TURNPOINT PROCEDURES, AND
T-6A charts will be winded on the ground just prior to the flight.
First, prepare the chart for expected speed and heading adjustments. Cut and tape a ½ inch by ½
inch piece of white paper next to the chart doghouse so that it does not interfere with the chart
information. Write your anticipated heading and wind compensations in this space based on
best-known wind information (current/forecast).
Second, obtain current winds along the route of flight from a qualified weather forecaster or
Flight Service Station (FSS). Wind velocity and direction can be obtained from forecast winds
aloft as well as current surface observations.
Next, determine crosswind and headwind components for each leg and record appropriate
compensations for heading and speed on the chart. See Figure 5-1. Place crab at the top of the
1/2 inch block and airspeed adjustment at the bottom. Use + and signs to indicate
amount/direction of compensation. Round all headwind and crosswind components to 5-knot
increments. Crab 2° for every 5 knots of crosswind (given 180 KTAS), which will be explained
later in the chapter.
In Figure 5-1, the example wind is 055 at 15 knots. This resulted in a 10 knot headwind and a
10 knot right crosswind. For this particular leg, the aircraft will fly heading 012 (4° right) and an
airspeed of 195 KIAS (assuming a 185 KIAS results in 180 KTAS).
Navigation will be conducted via a composite flight plan. Therefore, the departure to the route
will be via an IFR flight plan (using INAV procedures), followed by a transition to VFR flight
using Navigation procedures, then back to IFR flight for the recovery.