If you only remove trees, telegraph poles and any other man‑made obstacles on the Chevin, but do not cut into the ground, the critical change is that the highest point on the approach path drops to the bare‑earth summit (approximately 282 m AMSL). The current displacement of Runway 14 exists mainly because a taller object—almost certainly the Chevin radio mast plus maturing trees—penetrates the Obstacle Protection Surface (OPS) of the 3.5° PAPI.
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With bare ground only (282 m) and the existing 3.5° glidepath
· The 3.5° PAPI OPS slope is 2.6° (glidepath minus 0.9°).
· Distance from the full runway‑end threshold to the Chevin critical point ≈ 2 500 m.
· OPS height at that point if the threshold were not displaced:
193.2 + 2500 \times \tan(2.6^\circ) \approx 193.2 + 113.5 = \mathbf{306.7\ m\ AMSL}
· This is 24.7 m above the bare ridge.
→ No displacement needed. The full 2 250 m runway could be used for landing.
Even if the glidepath were lowered to a standard 3.0°
· OPS slope = 2.1°
· Height at the ridge without displacement:
193.2 + 2500 \times \tan(2.1^\circ) \approx 193.2 + 91.7 = \mathbf{284.9\ m\ AMSL}
· Still 2.9 m above the bare ground.
→ No displacement needed for a 3.0° PAPI either.
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What about the OLS (licensing surface)?
The OLS approach slope is a shallow 1 : 40 (≈1.43°). From the full runway end its height at the ridge would be only 255.7 m, so it would still be penetrated by 26 m. However, an OLS penetration does not automatically force a threshold displacement – it requires an aeronautical study and obstacle lighting/marking, but the runway can still be used from the very end if the operational approach surfaces (like the PAPI OPS) are clear.
Summary
Action Result
Remove all trees, poles and the radio mast, leaving bare Chevin at 282 m Displaced threshold on Runway 14 can be eliminated for both a 3.5° and a 3.0° PAPI. The full 2 250 m runway becomes available for landing, with no earthworks needed.
Remove only vegetation, leaving the mast The mast tip would still penetrate – some displacement would remain (amount depends on mast height).
Do nothing to the ground The OLS would still be broken, but that doesn’t force a displacement; it would be managed through obstacle assessment.
Bottom line: you don’t need to shave rock off the Chevin to use the whole runway. Removing the man‑made and natural obstacles on top of the ridge – particularly the radio mast and tall timber – would very likely be sufficient.