Aaron Swepston tontar@mindspring.com wrote:
The reason for sending this along is not to point out any particular pilots, but rather to point out a recurring problem that pilots seem to have all over the country and all over the world: the too slow approach.
One reason that pilots MIGHT think that they are coming in with plenty of speed could be the ground rush perception. At 1,000 feet, the ground barely seems to move beneath us, but as we get progressively closer, the ground "appears" to move faster and faster, even if we ourselves begin to fly slower and slower. It is an optical illusion that speed is increasing as we approach the ground.
Now, consider that many pilots do not fly their approach with any great degree of excess speed, or speed above trim speed. Combine that with an optical perception that the ground is going faster and faster as the pilot gets closer and closer, and you have a perfect recipe for a pilot to believe that they are actually accelerating as they go through their final leg, and that perception gives them the subconscious (or conscious, as I have seen in some pilots) excuse to start slowing down. They slow down to maintain the "appearance" of a consistent speed as they descend, to the point where they are far too slow when they reach the ground, and definitely at the time that a flare should take place.
This may not be the one and only reason that pilots do this over and over again, but it seems to be at least one popular reason that some are consistently too slow to flare. Speed seems wrong when the optical experience of the entire flight has been one of virtually snail pace ground movement.
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Tryg Hoff HOFT235@LNI.WA.GOV responds:
This is THE most common problem in landing. I see too many pilots pushing further and further out as they near the ground then they whack. Why? The glider finally stalls and they no longer have any flair authority because they're already pushed out. The result is inevitable.
A solution: Keep your head between the downtubes on approach. This does two things.
1. It gives you a common reference for where the control bar should be.
2. It insures you are maintaining adequate flying speed all the way to the ground and you will have enough flair authority when you get into ground effect and do your round out.
This solution has worked for everyone I have suggested it to. It also maintains a safe speed for approach unlike the hotdogs that like to come in hot. Sometimes these guys loose their teeth in the process ;-)
A lot can be learned in the Hang Gliding community from just watching airplanes land. A controlled, stable approach with adequate speed is best.
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Aaron Swepston tontar@mindspring.com writes:
There's no question that the biggest problem with whacks is that the pilot will start pushing out gradually before flare to the point where they are actually mushing the root area of the glider, and then they have only a few inches more that they are capable of pushing out beyond that. The technical analysis is in the can, it's already a known quantity. The unknown is WHY the pilots do it in the first place. Why they want to actually slow the glider down below trim speed. Trim speed is an aerodynamic quantity that has nothing to do with any visual reference of the ground. The glider will "want" to be flared from trim speed, not from some ground speed reference that can have the actual airspeed varying by huge amounts.
In a wind, the ground speed can be almost nothing, but the "airspeed" is still up there at or above trim. In no wind, or even downwind, the ground speed can be horrendous, while the "airspeed" is or should be still up there at trim. But to make the ground speed look better when there is less wind, pilots will push out until the glider is flying below trim, and until the ground speed "looks" better. Problem is, looking for that comfortable ground speed is exactly what will force them into the ground a lot harder than they would prefer to!
My advice is always the same. Come in with excess speed. That means with the hands on the front of the basetube or downtubes, pulling in with some pressure. Once down to the ground, level off, don't balloon up, but level off. Speed should still be higher than trim, meaning the hands should still be putting pressure on the front of the tubes. As the speed dissipates, the pressure is relaxed, and then the hands gravitate to the back of the tubes. As the hands subconsciously want to push on the back of the tubes to slow the glider down, take over, don't be a passenger or a victim to automatic hand movement! When you feel your hands wanting to push out even a bit to slow down, push out to a full flare.
Giving up your pilot-in-command status at the end of the final, allowing some subconscious entity to push on those downtubes to slow you down, is crazy. Be in charge, be the pilot in command, do NOT allow anything or anyone to push that bar out on you to slow it down. Flare from trim, and you will get a decent rotation for the glider to stop.
Whenever I see the arms slowly pushing out to slow down, I think "passenger" and expect a whack.