By Robert N. Rossier, EAA 472091
This piece originally ran in Robert’s Stick and Rudder column in the November 2024 issue of EAA Sport Aviation magazine.
For a newly minted private pilot, the approach to Runway 35 at Sky Acres (44N) in New York looked pretty scary. The runway was somewhat narrow and sloped upward at a frightening angle. Undaunted, we stayed on our glide path as if it would all be normal.
Had I been at the controls, it would have been time for a go-around. We were clearly approaching at too steep an angle, and I couldn’t even guess when or where we should start our flare for the uphill touchdown. Fortunately, my friend — a 5,000-hour veteran who was at the controls of the Cessna 150 — was accustomed to such an approach and landing.
To my amazement, we rounded out, touched down, and easily made the turnoff for the taxiway. That was some four decades ago, but it’s etched in my memory. It remains a formative lesson in landing techniques. Up to that point, all my approaches and landings had been made to a straight and flat runway. As this experience highlighted, not all runways are level.
Pretty much everything we learn in private pilot training assumes a level runway: approach speeds, glide path, round-out, float, landing distance, braking, and stopping distances. While each is variable based on aircraft weight, configuration, wind, runway surface, and density altitude, all are predicated on a level surface on which to land. What happens when the runway is sloping is left as somewhat of a mystery.
In general, the rule of thumb is to take off and land as much as possible into the wind. But the geography and topography of some airport environments, combined with prevailing winds, may force us to consider alternatives. As we learn to operate at sloping runways, we’re generally taught to land uphill and depart downhill. But even that is not always a hard and fast rule, and few pilot’s operating handbooks (POHs) provide performance data for other than level runways.
A Different Environment
My years flying and giving flight instruction in Colorado provided me an opportunity to learn new lessons and practice alternative techniques. For example, flying a light training aircraft into Glenwood Springs, Colorado (KGWS), was pretty much a one-way in and one-way out situation. This was due in large part to airplane performance at high density altitude when confronted with steeply rising terrain.
The pattern for Runway 32, which slopes slightly upward, might include a pattern flown a bit higher than the normal 800 to 1,000 feet AGL, requiring one to lose a bit more altitude than normal on base and final. But more daunting is the fact that to the north of the 3,305-foot runway is rising mountainous terrain.
Generally, a touch-and-go or a go-around from a close-in final for Runway 32 was not an option. And although 3,305 feet might seem plenty long at sea level, with a field elevation of just under 6,000 feet, some would find the length lacking. Departures were to be made on the slightly down-sloping Runway 14, unless winds prohibited such.
A similar situation exists at Aspen airport (KASE) in Colorado, where field elevation is roughly 7,800 MSL and the runway is 8,000 feet long. The surrounding mountainous terrain is again an issue, and the runway slope is more exacerbated.
Runway 15 has a 2-degree upslope, which typically decreases the landing distance by about 20 percent. Landings are generally made to Runway 15 for precisely that reason, although the quickly rising terrain beyond the runway is a constant reminder to get the landing done right the first time. Runway 33 by contrast has a 2-degree downslope and is favored for departures.
The Uphill Struggle
So, what happens when we attempt to arrive or depart a sloping runway? It doesn’t take much imagination to figure out that an uphill departure is going to be a struggle. Fighting against the force of gravity, takeoff distances can be greatly increased, if a takeoff is even possible at all.
Landing uphill, while generally advantageous in terms of landing distance, comes with its own set of challenges. Perhaps the most difficult aspect of landing uphill is the one I observed on the approach to Sky Acres many years ago. When the runway before us is tilted upward, the perception is that we are high on the approach, so one common error is to fly a low approach, which can put us at risk for obstacle clearance, especially at night.
Next is the issue of kinetic energy. Since we’re actually landing on a rising slope, we tend to pitch too high in order to get the right landing picture, but instead we run out of energy and can end up slamming onto the runway.
One way to overcome the low approach issue is to use the spot landing technique, wherein we aim for a point on the runway at which we will begin our round-out. As long as we maintain the proper approach airspeed, and keep that aim point stationary on our windscreen, we’ll be on the proper glide path. Should the aim point move downward on the windscreen, we’re overshooting and need to reduce power. Should the aim point move upward in the windscreen, we’re undershooting and need to add power.
Once again, since the runway is sloping upward, the round-out is more abrupt than normal, so we need to anticipate the touchdown. A bit of soft-field technique might be valuable at this point. One reference suggests increasing the approach speed (1.4 VSO versus the normal 1.3 VSO) to compensate for the abrupt transition to touchdown.
Heading Downhill
Departing on a down-sloping runway doesn’t typically create a problem. With the attending gravity assist, the aircraft accelerates much more quickly, achieving flying speed with less distance than required for a level strip. The problem comes should we decide to abort the takeoff. Here we’re fighting the effects of gravity, and considerably more braking (and stopping distance) is required.
Landing on a downward slope is much more challenging. It is best avoided unless a particularly strong headwind is involved. The first challenge is the illusion that one is too low, so the common error is to fly a high approach. The real excitement can come in the flare. As the runway is dropping away from us, the sight picture may tend to prevent us from pitching up enough in the flare, and the tendency is to float much farther down the runway. Added to the high approach, it’s not unusual to overshoot considerably and land much farther down the runway than intended. After the wheels finally find the pavement, we have the gravity-assist factor that greatly extends the ground roll.
Here again, using a spot landing technique will keep us on the appropriate approach path to the aim point. At that point, we need to pitch a bit higher than we might normally expect. We can expect an extended float before touchdown and an increased need for braking. Should we add slick runway conditions or a tailwind, the conditions are even more challenging, often requiring more runway than is available.
Even if we’re not high in the mountains, sloping runways easily add an element beyond our basic flight training, and beyond the performance data in our POH. Our best bet may be to seek additional training from an experienced instructor to develop the skills and experience needed to successfully manage sloping terrain.
Robert N. Rossier, EAA 472091, has been flying for more than 40 years and has worked as a flight instructor, commercial pilot, chief pilot, and FAA flight check airman.