c. Allowance for Visual Course Guidance.
(1) Visual ground reference navigation is another form of course guidance. However, to take advantage of visual course guidance, a Flight Track Analysis must be performed.
(2) The ability to laterally avoid obstacles by visual reference can be very precise, if the obstacles can be seen and are apparent. It is the operator’s responsibility to operate in weather conditions, including ceiling and visibility at the time of the operation, that are consistent with the use of the visual ground reference points for the navigation upon which the obstacle analysis is based.
(3) To take advantage of visual course guidance, the flightcrew should be able to continuously determine and maintain the correct flightpath with respect to ground reference points so as to provide a safe clearance with respect to obstructions and terrain.
(a) The procedure should be well defined with respect to ground reference points so that the track to be flown can be analyzed for obstacle clearance requirements.
(b) An unambiguous written and/or pictorial description of the procedure must be provided for crew use.
(c) The limiting environmental conditions (wind, ceiling, visibility, day/night, ambient lighting, obstruction lighting, etc.) must be specified for the use of the procedure so that the flightcrew is able to visually acquire ground reference navigation points and navigate with respect to those points.
(d) The procedure must be within the one-engine-inoperative capabilities of the airplane with respect to turn radius, bank angles, climb gradients, effects of winds, cockpit visibility, etc.
(4) When visual course guidance is used for Flight Track Analysis, the following minimum allowances (in addition to turn radius) apply:
(a) If the obstacle itself is the reference point being used for visual course guidance, the minimum allowance is 300 feet for lateral clearance from that obstacle.
(b) When following a road, railroad, river, valley, etc., for course guidance, the minimum allowance is 1,000 feet on each side of the width of the navigation feature. This width should include the meandering and/or curves of the navigation feature being used or the definable center of the valley or river.
(c) When using a lateral visual reference point to initiate a turn, the minimum allowance is plus/minus 0.25 nm along the track at the turn point.
(d) When initiating a turn directly over a visual reference point, the minimum allowance is plus/minus 0.50 nm along the track at the turn point.
(e) When initiating a turn to avoid overflight of a visual reference point, the minimum allowance is plus/minus 1 nm along the track at the turn point.
(5) Visual course guidance may be used as part of an IFR procedure (e.g., SID, DP) or in conjunction with IFR flight during that portion of the operation which is in visual meteorological conditions (VMC). The visual course guidance may be used in combination with other forms of course guidance to construct a one-engine-inoperative departure procedure.