(article) distance & speed

[Wilfred]

We've been reviewing the FAA's Top 10 list of pilot-error accident causes. Next up: "misjudgment of distance and speed".

 

What the Feds are really getting at here are two types of accident:

 

Runway undershoot, resulting in landing short of the runway and/or stalling on approach.

 

Landing long, and going off the far end of the runway.

 

Coming up short

 

Landing short of the runway is usually the result of flying at too low an airspeed on final approach. As angle of attack increases it takes more and more power to maintain a given glide path. If the pilot does not add power or adjust pitch (to reduce angle of attack) the "sink rate", or rate of descent, may become excessive, and the angle of descent take the airplane to a point short of the prepared surface. If the pilot is lucky the plane will roll onto the runway without damage. If not...

 

Of course if angle of attack gets completely out of hand the airplane may stall, potentially impacting the ground at a higher rate of descent and out of control, with even more dire consequences.

 

It's counterintuitive to push the nose down if the ground is coming up too fast. It's also considered bad form to have to add power on final approach, despite the real need when the glidepath is too steep. Making sense of the relationship between power and pitch, and angle and rate of descent, is one of the main reasons we have to practice landings so much before the first solo flight, and why pattern practice is a staple of flight reviews throughout a pilot's entire flying lifetime.

 

Landing long

 

Although (as the adage goes) it's better to go off the far end of the runway at, say, 20 knots than to hit the approach end at a much higher speed, running off the end of the runway is another common cause of mishaps. This usually results from too fast a speed on final approach. As a rough rule, for ever extra five knots of airspeed on short final a typical light piston airplane will increase its landing distance by about 10%. Come in 10 knots fast and you'll use up about 20% more runway, all else being equal.

 

If you misjudge your angle of descent and land farther down the runway than expected you're also more likely to run off the far end. Combine "hot" (too much airspeed) and "high" (too shallow a descent) and you may find yourself on the evening news as they hoist your airplane out of somebody's parking lot.

 

What's the answer to both scenarios? Good airspeed control. This comes from using a target power setting and pitch attitude. You may have to adjust these for any given landing, but you can't tell what adjustments to make unless you have a "standard" approach (and its resulting performance) in mind to start.

 

Aero-tip of the day: Practice precise airspeed control on final approach to make more accurate landings