I do most of my flying from strips that are sloping / undulating. There are several factors to take into account.
First, preparation. Know what the slope / undulations are before you arrive. As a general rule, if you can see the slope from the air, it is quite steep. The undulations will probably therefore only become apparent when you're low, and you may not be in a position to land on the most favourable part of the strip.
Second, precision. This has been stressed by several people above. You need to choose your touchdown point, and make sure you touch down on it.
The best way to do this is to pick an aiming point a suitable distance before your touchdown point (the distance depends on the wind, the aircraft type, the slope, and the speed at which you have decided to fly the approach), and fly a constant-speed approach to that aiming point. You don't need low-speed back-of-the-drag-curve heroics. If the strip is short as well as undulating, you just move your aiming point a suitable distance before the strip to ensure you touch down right at the start.
Third, the flare. Chuck Ellsworth detailed this far better than I can recently. As gasax says, on an undulating / sloping strip there's no point in looking at the end of the strip, 'cos you often can't see it. An important point about the flare on a sloping strip is that it should be initiated at the normal height above your
touchdown point. This could mean that you are much higher than normal above the ground when you initiate the flare. You have to resist the urge to fly down to the normal height then pull up sharply to flare, or you will likely stall. It takes a bit of practice to get used to it, but is not a big deal.
Fourth, speed. The rule of thumb I use is as follows: normal approach speed for any slope up to 10%. Add 1km/h (one day the French will use knots for light aircraft...
) per additional % of slope after that. So for a 20% slope, my approach is 10km/h (about 5 knots) faster than usual.
Fifth, power. Landing on a sloping strip, gasax's advice is spot on. If you cut the power to idle as you start the flare, and then have to pitch up significantly to get a 3-point attitude above the slope, your speed will fall very quickly and you will probably have a very abrupt arrival some way short of your intended touchdown point. If instead, you leave a bit of power on during the flare you can reach the 3-point attitude (do you say 2-point in a Europa
)just above the touchdown point. Cut the power and you're down.
As a final comment, if you are able to choose your touchdown point I find it's generally preferable to land in the slope on an undulating runway. If you land in a "concave" section where the slope starts, the flare is more difficult - your pitch attitude needs to be continuously increasing to follow the slope. Landing in a "convex" section is harder still (but very satisfying if you get it right
). After the flare you need to relax the back pressure and follow the ground as the slope levels off. If you don't, you stall in from several feet up....
