Instructor » Mountain Flying » Horizon
- The line where the sky meets the sea.
Identification of real or imaginary horizon
Accurate identification of a useable horizon and being able to reference nose attitude to that horizon usually requires a lot of concentrated practice.
It is essential to be able to identify a useable horizon and to be aware of some of the pitfalls involved.
When flying among the mountains, or anywhere the horizon is not visible, the pilot must learn to imagine that horizon.
If pilots try to follow the artificial horizon, they will only ever react to the instruments, when they should have their eyes outside and be anticipating the attitude changes. In bush-clad areas there is a good highlevel horizon reference – the bush line (ie, mean winter snowline).
In New Zealand the bush grows up to an altitude of around 3500 feet, and it is a good means of locating a useable horizon reference in steep mountainous terrain.
Super-imposing a useable horizon on any variable background
In the mountains, visualise where this line is as if the mountains were transparent, and superimpose it on the terrain.
In bush-clad areas there is a good high-level horizon reference – the bush line.
Relying on your instruments alone won’t work.
In a confined space with reduced visibility your eyes must be outside, and performance must be interpreted by any subtle change in nose attitude and only confirmed with instruments.
With reduced altitude and space the lag in instruments is too great to rely on them implicitly.
i.e. visualising where the real horizon sits as if terrain or obstacles were transparent
Illusions associated with inaccurate horizon definition
Hazard potential associated with illusions and poor horizon definition
The frequent lack of a defined external horizon can create aircraft attitude and airspeed problems.
A gradual valley gradient can seduce a pilot into subtly raising the aircraft nose resulting in a potentially unnoticeable loss in airspeed and RPM – until it is too late and there is insufficient height or space to recover.