Explainer27 SEP 20264 min readDromopedia editors

Uphill landings

Most runways are built as flat as the ground allows. A few slope on purpose — aircraft land up the hill and take off down it, and there is only one way to do either.

Altiport de Courchevel 2022
Courchevel Altiport · DimiTalen · CC0 · Commons

Airport designers work hard to keep runways level. ICAO recommends that the overall slope of a runway — the difference between its highest and lowest points, divided by its length — stay within 1% for runways used by airliners and 2% for small ones.1 The FAA sets similar limits: 1.5% for faster aircraft, 2% for slower ones.2

In the mountains that is often impossible. There is no flat ground long enough, and levelling a slope would mean moving a hillside. A handful of airfields took the other route: they kept the slope and built their procedures around it.

What a slope does

On an upslope, gravity works against an aircraft taking off and for an aircraft landing. The FAA's pilot handbook puts it plainly: an upsloping runway lengthens the take-off run and shortens the landing roll; a downslope does the opposite.3 The UK Civil Aviation Authority gives light-aircraft pilots a rule of thumb: a 2% slope adds about 10% to the take-off distance uphill, or to the landing distance downhill.4

On a steep strip the effect is large. French mountain pilots reckon that a 20% upslope roughly halves the landing roll.5 At 18.66%, the steepest section at Courchevel, the slope alone pushes against a rolling aircraft with about 0.18 g — around 1.8 m/s².6

So the steepest strips are used one way only. Aircraft land uphill, which brakes them, and take off downhill, which helps them accelerate. The price is that the approach becomes a commitment: below a certain point the terrain ahead rises faster than the aircraft can climb, and a go-around is generally no longer possible.5

Courchevel

CVFCourchevel Altiport FR · 2,007 M / 6,583 FT · RWY 536 M / 1,759 FTLand on 22, uphill; take off on 04, downhill. The steepest section climbs 18.66%.

The altiport above Courchevel in the Savoie Alps is the best-known example. The current French chart gives a paved runway of 536 × 40 m in three sections. From the lower threshold it climbs 12.5% for 134 m, then 18.66% for 280 m, and ends on a 122 m platform that is almost level (0.45%).7 Over its whole length the runway rises about 65 m, an average of 12%. That is also the figure the register gives, from the heights of the two thresholds.8

Arrival on runway 22 and departure on runway 04 are both mandatory. There are no runway lights and no instrument approach.7 Aeroplane pilots need either the mountain rating or an authorisation for this altiport specifically, and to keep it they must make two landings there as pilot in command every nine months.9 Only propeller aircraft of up to 5.7 tonnes are accepted, plus helicopters.7

The council approved the altiport in 1961, and the first aircraft landed on 31 January 1962. For the 1992 Albertville Olympics the runway was extended and realigned so that Dash 7 airliners could use it.10 That aircraft is now well over today's weight limit.

Courchevel is the steepest of the French altiports, but not the only steep one. At L'Alpe d'Huez the middle section of the runway climbs 15.5%; at Méribel the steepest part is 11%, and at Megève 9.3%. All three are also land-uphill, take-off-downhill fields.11

AHZL'Alpe d'Huez - Henri Giraud Altiport FR · 1,860 M / 6,102 FT · RWY 448 M / 1,470 FTMiddle section 15.5%; about 10.8% over the whole runway.

Lukla

LUATenzing-Hillary Airport NP · 2,859 M / 9,380 FT · RWY 527 M / 1,729 FTLand on 06, uphill; take off on 24, downhill. 11.7% upslope.

Tenzing-Hillary Airport at Lukla is the gateway to the Everest region. Its runway is 527 m long and 20 m wide, at about 2,846 m above sea level, with an upslope of 11.7%. Aircraft land on runway 06 and take off on runway 24.12 The airport authority lists the Dornier 228, the Twin Otter, the Let L-410, the Harbin Y-12 and the Cessna Caravan among the aircraft that use it.13

Nepal's rules place Lukla in category C, "altiport": fields at or above 7,000 ft where a missed approach is not advisable or possible after a certain point. Pilots qualify in steps. The intermediate category alone takes at least 100 missions on short-take-off strips and a year of experience. For a category C field, a pilot flies ten missions there and then a check flight with an instructor.14

The strip was built in 1964 by the Himalayan Trust under Edmund Hillary, to fly in supplies for the schools and hospitals it was building in the Khumbu.15

Strips without a chart

Courchevel and Lukla are documented down to the metre. Many steep strips are not. In the highlands of Papua New Guinea and Indonesian Papua, mission and bush operators fly short grass and gravel strips cut into hillsides. A pilot for Mission Aviation Fellowship in Papua New Guinea describes Maimafu as 460 m long with an average slope of 13%, varying between 5% and 16% along its length. In that country any strip shorter than 500 m or steeper than 10% is automatically rated class D. "There comes a point," she writes, "where you will be unable to outclimb the terrain or turn around, so you are committed to land."16

The steepest runways in the register are strips of this kind, in the Papua highlands. Their gradients are worked out from threshold heights in OurAirports, and no chart confirms them, so read those figures with care.8

Outside the rulebook

There are no ICAO standards for altiports at all. A draft regional guide from ICAO's Asia-Pacific office proposes limits: an overall slope of no more than 10%, no section steeper than 15%, and gentler segments at each end. It quotes the older ICAO definition of an altiport: one approach and departure area, landing up the slope and taking off down it.6 By those numbers, both Courchevel and Lukla would be too steep to build today.

Sources

  1. ICAO, Annex 14, Volume I — Aerodrome Design and Operations, 8th edition, 2018, §3.1.13–3.1.14: 1% overall for code numbers 3 and 4, 2% for code numbers 1 and 2.

  2. FAA, Advisory Circular 150/5300-13B, Airport Design, 2022, §3.16.1: ±1.5% for approach categories C–E, ±2% for A and B.

  3. FAA, Pilot's Handbook of Aeronautical Knowledge, chapter 11, "Runway Surface and Gradient".

  4. UK Civil Aviation Authority, Safety Sense Leaflet 7c, Aeroplane Performance, January 2013.

  5. BEA, report BEA2022-0264 on the accident to F-HIMY, May 2023, §2.4, citing the French mountain pilots' association (AFPM). 2

  6. ICAO Asia and Pacific Office, draft Regional Guidance for the Design and Operation of Altiports, AP-ADO/TF, 2024. The acceleration is g × sin α for the slope angle α. 2

  7. SIA, visual approach chart LFLJ Courchevel, French AIP, AIRAC cycle of 3 September 2026. Older charts, and most other sources, give 537 m. 2 3

  8. Dromopedia register: Steepest runways, the average gradient between the two thresholds, computed from the threshold elevations in OurAirports. Courchevel: entry data. 2

  9. Arrêté du 7 juillet 2023 amending the arrêté of 21 June 2019 on the use of altiports and mountain landing sites, in force since 25 October 2023.

  10. Mairie de Courchevel, history of the altiport.

  11. SIA, visual approach charts, French AIP of 3 September 2026: LFHU L'Alpe d'Huez, LFKX Méribel, LFHM Megève.

  12. Civil Aviation Authority of Nepal, AIP Nepal, AFIS AD 2 — Tenzing-Hillary Airport, Lukla, 30 April 2026.

  13. Civil Aviation Authority of Nepal, Tenzing-Hillary Airport, Lukla — airport fact sheet.

  14. Civil Aviation Authority of Nepal, Flight Operations Requirements — Aeroplane (FOR-A), 6th edition, July 2020, chapter 14. Twin-engine captains also need 2,500 hours and 18 months in command.

  15. Himalayan Trust Nepal, Tenzing-Hillary Airport, Lukla. The Nepali authority gives September 1971 as the start of operations, probably the start of government-run scheduled service.

  16. Bridget Ingham, "Pilot's perspective: short, steep and slippery", MAF Papua New Guinea, 19 May 2023.

Codes, elevations and runway lengths in the airport cards are from the Dromopedia register, built from OurAirports. Each entry’s data page names the source of every field; see also About the data.