(4). Correct: To correct for 14 seconds adjust speed 15 knots for 280 seconds
(4 minutes 40 seconds).
"Airspeed 325 KIAS for 4 minutes 40 seconds. Time in: 10+10. Time
To correct for 14 seconds adjust speed 10 knots for 420 seconds (7
"Airspeed 320 KIAS for 7 minutes. Time in: 10+10. Time out: 17+10."
NOTE: the above methods would not be necessary in T-39 operations, as that aircraft's
maximum low altitude speed is 350 knots.
The following notes also apply to time corrections:
Timing starts when the pilot first advances/retards the throttles and ends when the
throttles are moved back.
Compensated airspeed = airspeed (Temp adjusted) + head/tailwind.
Deviations of at least 12 seconds off preflight are required to initiate a correction,
except on the target leg. On the target leg, corrections for less than 12 seconds of
error are permissible.
For wind analysis, compare actual time to updated time; for corrections, compare
actual time to preflight time.
Talk through your calculations to avoid making them in the wrong direction.
EXAMPLE 7-6: The time across a railroad bridge (preflight for 10+12, updated 10+02) is
9+55. Base airspeed is 300 knots, and the previous turn point time was 6+50, 10 seconds early.
FIX: "The checkpoint was at 9+55, preflight was 10+12, resulting in 17
· Analyze: The aircraft is early indicating a tailwind. On this leg the aircraft
got 7 seconds earlier (17 seconds - 10 seconds) over a period of three
minutes. Using the equations, 7 divided by 3 is approximately 2. Seconds
per minute multiplied by 5 equals about 10 knots of tailwind.
Compensate: Compensated airspeed is 290 IAS (300-10).
Correct: The aircraft is 17 seconds early. "Decrease airspeed to 260 IAS
(290-30) for 2 minutes and 50 seconds. Time in is 11+00. Time out is
220.127.116.11. In the previous example, note the wind analysis was based on time gained or lost
between two points, but corrections are based on flight planned timing. At the first checkpoint
there was a 10-second error, so no correction was called for. However, the time to the next
checkpoint or turn point was updated to reflect the 10-second deviation. Had this not been done,
the wind analysis would have been for 17 seconds over 3 minutes, resulting in an estimated wind
of 30 kts; well outside of the 10 kts grading criteria.