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Is there a general vertical speed that pilots shoot for, or is it entirely by feel/trial-and-error?

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    $\begingroup$ -1 FPM, but it takes a looonngggg runway! ;-) $\endgroup$ – Lnafziger Jan 29 '14 at 22:34
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    $\begingroup$ I was just going to with 0 :) impossible? $\endgroup$ – p1l0t Jan 29 '14 at 22:43
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    $\begingroup$ @p1l0t That's what I thought initially too but then realized that you couldn't land! ;-) $\endgroup$ – Lnafziger Jan 29 '14 at 23:09
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    $\begingroup$ @p1l0t Theoretically the maths says you could land with zero vertical velocity. Consider the shape of the curve height=x^2. When x is zero (touchdown point) the rate of change in height is also zero (dh/dx = 2*x ), but only at the instant x=0. If you are out by any amount either way you either don't touch down, or you land harder. However real life also has other things to take into consideration that means this will never be practical. Such as transitioning from wheels touching the ground with zero force to all lift dumped ready for breaking. Or simply lumps in the runway. $\endgroup$ – BeowulfNode42 Feb 25 '14 at 14:09
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    $\begingroup$ There is a bit of discrepancy between simulation and real world here. Simulator obviously knows vertical speed at any instant while accurately simulating the shock struts response is hard because the exact properties are hard to get (the manufacturer knows them, but does not usually publish them). On the other hand in real life temporal resolution of vertical speed indicator is not sufficient to get accurate value at touchdown while peak acceleration is easier to measure, and risk of damage depends on the peak acceleration, so that is what is used. $\endgroup$ – Jan Hudec Jun 11 '15 at 7:57
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Are you talking the approach-to-land, or actual landing? Keep in mind, when you flare, you are technically arresting a descent, so the VSI should not read much more/less than zero. For a stable approach, 500-700 FPM on a 3 degree glide slope usually works out well for ILS approaches. Keep in mind, all instrument approaches terminate visually, unless you are in a CAT III capable aircraft, which I do not fly.

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I would argue that the way to think of the perfect landing is not in terms of vertical speed but rather in terms of the G-forces involved.

Thinking in terms of G-force, the perfect force depends on what you're landing on and how long it is. The various conditions I can think of offhand are:

  1. long dry runway, no wind or straight down the runway -- try for a greaser if you want, although arguably a greaser is not the safest landing.

  2. cross wind -- the higher the xwind the more you want a firm touchdown.

  3. short runway -- firm so you will have effective braking.

  4. wet runway -- firm, especially if the runway has standing water. The two times that I blew tires on landing was when there was standing water and I didn't plant it firmly enough. In the first case the tires blew before I used the brakes. It was an F27 and one of our pilots was in back at a window seat. He said the two right wheels never rotated at all. I had touched down with a greaser on a puddle.

  5. carrier -- I once checked out a Navy carrier pilot in a 182. It was really hard for him to flare for a landing, since they don't do that. As I remember, he said that they wanted a 4G landing impact.

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    $\begingroup$ Lol at the carrier pilot, totally understand that! But they definitely land exactly where they want to! $\endgroup$ – flyingfisch Jan 30 '14 at 0:55
  • $\begingroup$ The G-force experienced also depends on the shock-absorbing qualities of your mains, so it might be hard to figure out from the vertical speed, and it will definitely depend on the aircraft. Good answer! $\endgroup$ – falstro Jan 30 '14 at 7:55
  • $\begingroup$ @roe You're right, and as I think about it, it would not be an easy relationship to define mathematically, at least not for me. I edited out the last part of that first sentence. $\endgroup$ – Terry Jan 30 '14 at 8:15
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    $\begingroup$ @JayCarr It's hard to explain something I don't fully understand myself, but here goes. A too-smooth touchdown on a wet runway, especially if you touch down on standing water, fails to provide enough friction to start the tire rotating as the tire isn't really in contact with the runway. It's called dynamic hydroplaning. AS the aircraft continues, it's essentially surfing, and, as counter-intuitive as it might sound, the tire surface in contact with the water is super-heating. Finally, the superheated part of the tire fails. $\endgroup$ – Terry Jun 10 '14 at 18:53
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    $\begingroup$ I object to the concept of a Carrier pilot "landing" - no Carrier pilot has ever landed an aircraft, they simply crash it very accurately. $\endgroup$ – Jon Story Jan 8 '15 at 15:33
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In my experience it's feel/trial-and-error-and-error-and-error.

5 feet off the runway is not a good time to be looking at your VSI.


Edit

Since you're looking at a record of your vertical speed after the fact:

Lower numbers are better of course. The goal is to get the rate low enough that the landing gear can absorb the impact without passing on any of the energy. 60 FPM would be 1 foot/second. I'm sure most landing gear would soak that up and earn you praises from your passengers.

I've had exactly one "squeeker" - I didn't know I'd touched down until the wheels started moving. Naturally, I was in a single seat airplane with no witnesses :-(

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  • $\begingroup$ Yeah, actually I was wondering so I could analyze my landings in a flight sim. It tells me my touchdown FPM after each flight. ;-) $\endgroup$ – flyingfisch Jan 29 '14 at 23:05
  • $\begingroup$ Hmm. Lower numbers are better of course. The goal is to get the rate low enough that that landing gear can absorb the impact without passing on any of the energy. 60 FPM would be 1 foot/second. I'm sure most landing gear would soak that up and earn you praises from your passengers. $\endgroup$ – Dan Pichelman Jan 29 '14 at 23:08
  • $\begingroup$ if you want to edit your answer with that information I can accept it ;-) $\endgroup$ – flyingfisch Jan 29 '14 at 23:17

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