If the above description is difficult to visualize, draw it out! Resolving the above information,
the aircraft is 2 NM left of planned course. With a time in of 6+40, options are as follows:
"Right 009, time in 6+40, time out 10+40."
"Right 019, time in 6+40, time out 8+40"
BDHI Corrections - This correction is typically a faster and less complicated means to return to
course centerline on the appropriate heading, but it has tradeoffs. Once you commence a BDHI,
for instance, you might not be able to fix how far off course you would have become, and you
have added a certain amount of time (by traveling a longer distance) to the ensuing checkpoint.
If able, attempt to estimate your distance off course before initiating a BDHI correction. This
will be helpful in later determining wind effects. You may utilize the BDHI correction with any
identified point along the route, whether a turnpoint or intermediate checkpoint.
The next turnpoint (a large lock and dam) is visible two minutes prior to the turn. Unfortunately,
instead of being at the 12 o'clock position, it is about 10º right of the aircraft track. It is obvious
the aircraft is off course, but by exactly how much is unknown.
This is the situation where BDHI corrections are most helpful. The goal of this maneuver is to
intercept the flight planned course inbound to the checkpoint on the correct heading. It is NOT a
homing maneuver! It is similar to intercepting and maintaining a radial to a NAVAID, only the
NAVAID is a visual checkpoint and the radial is our flight planned magnetic course (hence the
term "BDHI correction" - Bearing Distance Heading Intercept).
To perform a BDHI correction, the following conditions must exist:
For intermediate checkpoints, the point must be on or closer to course than the aircraft.
The point must be in sight and within 30º of compensated heading (11 to 1 o'clock). This
limitation prevents doing an excessive turning or "S-turn"
correction to course.
A standard course correction is not practical prior to passing the point. For example, your
turnpoint is in sight and the aircraft is approximately 1/3 mile off course. None of the standard
course corrections adequately apply (i.e., ½ mile and 1 minute increments).
BDHI corrections follow this basic format:
Call for a 30º turn from compensated heading towards the checkpoint.
As the aircraft turns to the new heading, the point will drift to the opposite side of
the 12 o'clock position. Call "steady up" after this occurs.