Monday, September 28, 2009

Visual Illusions - Descent into a Fog Bank

Descent Into A Fog Bank

Approach over water leaves little room for error. In IFR flying the transition from IFR to VFR holds hidden dangers. The existence of layers of clouds in the approach lulls one to the dangers of over-the-water approaches.

The sensation, visually, when penetrating a fog bank, is a sudden movement of the nose of the aircraft upward. You temporarily substitute the fog layer for the horizon which tricks you into thinking the plane is suddenly climbing.

If you don't anticipate this effect, before the event, you may instinctively lower the nose by pushing forward on the yoke.

The end result, on a close to minimums landing, may result in a crash. This is especially true for fast, high performance planes where quick movements of the elevator control may result in significant altitude loss.

I can think of a land based illusion that sometimes occurs when two cars are waiting for a light to change and, just before the light does change, one of the cars rolls backward a couple of feet. The stationary car thinks, incorrectly, his car is moving forward and slams on hs brakes.

I am sure you readers and experienced pilots can think of other explanations of these visual phenomenons that create that sensation that things are not quite right.