Jenx Aviation

The Constant Sight Line Angle PFL Technique

The Sight Line Angle (SLA) is the angle between the horizon and a point on the ground as seen by the pilot.

The Theory

In the Climbing and Descending lesson for the PPL we are taught about a non-moving point in the screen which is where we will land. If we consider a point on the ground on the extended wing, and we maintain that Sight Line Angle (SLA), we will describe a cone until impact. We will experience increasing bank and 'g'. Therefore, by adjusting Angle of Bank whilst maintaining optimum glide speed we can:
  • Accurately assess our ROD and range.
  • Remain in sight of our intended landing field.
  • Maintain a safe approach path.

Picking the field

We must pick the field in the normal way using the 5 Ss:
  • Size.
  • Shape.
  • Surface.
  • Slope.
  • Surroundings - obstacles.
We then pick an IAP (Initial Aiming Point) approx 1/2 way into the field which will result in a FAP (Final Aiming Point) in the first 1/3 of the field.

The Pattern

First we need to find out by experiment the height lost in our aircraft in a 360o turn at 30 and 45o angle of bank. We use this to manouvre as necessary to achieve a 'High Key' point (A) at 1500ft into wind and along the intended landing direction.
As the IAP passes down the side of the aircraft (B) we turn 90o and extend on a wind corrected heading until the IAP is 45o behind. We then turn at our estimated bank angle say 20o.
We are aiming to pass 180o downwind, abeam our IAP at 300ft plus your aircrafts height loss in 180o @ 30o AOB. This point (C) is known as 'Low Key' and will be 800-1000ft in most cases.

The Final Approach

The additional 300ft allowance in the pattern is to allow for wind effects and for the use of flap. If the surface wind exceeds 20kts the additional allowance should be increased to 500ft.
As we fly from 'Low Key' to short-finals we vary the angle of bank to achieve the IAP. As we turn, the AOB will increase as we turn into wind.
If we are low, we fly direct to the IAP and if high we slacken the turn and extend the ground track; we may fly through the centre-line. When we are certain of making the IAP we can use flap or side-slip to bring the touch down back to the FAP.
This page is maintained by Jenx
Last updated on 18 Dec 2002