High and Low Circuits
Chapter 13.11
Familiarisation with the Visual References of a Circuit
On a familiar circuit, you will gradually get accustomed during the training to the particularities of the terrain and to the local landmarks. You will consciously or unconsciously establish geographical references in respect to the distances to the runway and for the entry into BASE and FINAL.
This familiarisation always occurs when you are doing several CIRCUITS on the same aerodrome, so you gain confidence in estimating your spatial situation on the CIRCUIT.
Familiarisation with the Visual References of a Circuit
However, difficulties may arise when you need to approach from an altitude that is unfamiliar to you or at an unknown aerodrome.
Without the known references, you will have difficulty recognizing the different stages of the approach and estimating the approach angle.
Uncertainties and errors complicate the stabilization of the approach.
High and Low Circuits
In practice, approaches from unusual altitudes occur for the following reasons:
- The altitude of a circuit does not match that of a standard circuit
- Air traffic controllers may require an approach from a non-standard altitude
- Meteorological reasons may require an approach from a non-standard altitude
By training the high and low circuits, you learn a systematic method for non-standard approaches. You acquire the ability to recognize and reach the known visual glide path from unusual departure positions.
Performing the exercise
In aerodromes with air traffic control, the training of the high and low circuits shall be carried out in agreement with the control services.
It is important in these non-standard approaches to constantly perform the LOOKOUT and to announce additional POSITION REPORTS that make all traffic aware of this unusual maneouvre.
The training of the high and low circuits is done both during basic training and during conversion and familiarisation flights.
High Circuit
The DOWNWIND of a HIGH CIRCUIT is between 300 and 500 ft above the DOWNWIND of the standard circuit.
Low Circuit
The DOWNWIND of a LOW CIRCUIT is 200-300 ft below the standard circuit altitude.
High and Low Circuits
These procedures are applied only for training purposes! The goal is to develop the sense for correct altitude for a final approach.
Optical Illusions on High and Low Circuits
DOWNWIND higher than the STANDARD-CIRCUIT
By flying on a high DOWNWIND, the runway appears closer than it really is, so you tend to turn into BASE and FINAL too soon.
If you notice it in time, you can easily make a correction towards the CENTERLINE with a flatter turn to the FINAL.
Optical Illusions on High and Low Circuits
DOWNWIND lower than STANDARD CIRCUIT
On a lower DOWNWIND and especially on a lower BASE, you get the impression that the horizontal distance to the runway is greater than it actually is. Due to this illusion, you tend to turn into FINAL too late.
The following difficulties then appear:
Either you have to overcompensate the turn with an exceptionally large bank in the vicinity of the ground, or you cross the centreline of the runway, making it difficult for you to stabilize the aircraft in FINAL.