Corrections for Time

T-6A NAVIGATION

CHAPTER FIVE

turn, you must analyze the consequences of the turn geometry as it relates to timing.

Corrections for Time. In the T-6A, use a 20 knot speed change (10% of your mission ground

speed (18 knots) rounded up to 20 knots) or a 40 knot speed change (~20% of your mission

ground speed (36 knots) rounded up to 40 knots) to correct timing deviations. Choose an

appropriate correction to keep the aircraft within operating limitations. At 180 knots ground

speed, a 20 knot change will add or reduce 6 seconds each minute (40 knots will yield 12 seconds

per minute). These gains/losses result from the correlation that 20 knots is ~10% of 180, and 6

seconds is 10% of 60. To determine the length of time the 20 knot speed correction must remain

in, divide the number of seconds off preflight time by six. The whole number is the minutes and

adding a zero to the remainder will yield the seconds required (see example below). If you use a

20% correction (i.e. 40 knots), simply use one half of the 10% answer. That is to say, you are

correcting at twice the rate, so leave in correction half as long. In general, any time correction

you initiate will be left in for an increment of 12 seconds (at 20 knots) or 6 seconds (at 40 knots).

Seconds off preflight time = minutes needed of 10% speed correction

Example

To correct for 14 seconds late, adjust speed 20 knots for 2 minutes and 20 seconds (140 seconds).

For a compensated airspeed of 200, the SNFO/SWSO student would instruct, "Airspeed 200 KIAS

for 2 minutes 20 seconds. "Time in 10+10, time out 12+30."

Another solution would be to use the 40 knot increase which would be "Airspeed 220 for 1 minute

and 10 seconds."

NOTES

1. The time it takes for the aircraft to accelerate to the correction

airspeed and the time to decelerate afterwards cancel each other.

Timing starts when the pilot first advances/retards the throttle and

ends when the throttle is moved back.

2. Only 20 or 40 knot changes to compensated airspeed are

permitted. (Compensated airspeed = base airspeed (Temp

adjusted) + head/tailwind)

3. Corrections for time require at least 12 seconds off preflight.

Therefore, the minimum length of a speed correction is 2 min

minutes, except on the target leg.

4. Talk through your calculations to avoid making them in the

wrong direction.

FLIGHT PROCEDURES

5-19