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The Art of Crashing


cdarza

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It's an interesting read. It seems logical to me (I'm not a physicist or medical doctor).

A couple of observations:

 

This article reinforces the old pilot advice, "fly the plane all the way to the crash", which means to me that one is putting the airplane in the optimal position at all times, even when the crash is immediately imminent.

 

The description of the set down does not include the phenomenon of ground effect. All of us are familiar with and deliberately use or deal with ground effect. Some may say to ignore ground effect, that you will be so busy you'll forget it or you may stall while trying to get into it. OK, one can say those things. It might be more useful to say that ground effect will have various affects in various approaches and it is best when one can treat it like any tool that is available for use as appropriate.

 

Now let the preferences and biases begin. None of us wants to crash. But the overriding message of the article is to reduce G loads and to spread them out. That means slow down the ground speed of the airplane. One way to become comfortable doing that is to practice landing slowly. A friend of mine and I are typically landing in the low 40's and high 30's with one person and half fuel. The stall horn on the Dynon is sometimes but not always squawking. Since my eyes are outside, I'm not sure where the bars on the AOA are, but they are probably in the red, probably about where the chevrons start. I think I can do better safely. One has to be very much in the moment or "in the groove" and can't be along for the ride when doing this. It means one is making appropriate inputs at the right time as opposed to trying to react after a digression has become evident.

 

An appropriate question for the physicists on this site might be to compare the G forces involved in a parachute deployment and touchdown as apposed to a traditional landing.

 

Useful article.

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I read one article, I think it was in Aviation Safety, about energy in crashes.  The gist was that at <40kt impact speed the chances of death are very small, a few percentage points, but at 60kt it's something like 50% and at 80kt it's 80%.  Above 80kt the chances of survival become...slim.

 

This is why stall/spins are so deadly, the impact is at a relatively high rate of speed and nearly perpendicular angle to an unyielding object (The Earth).

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Jim, when they say reduce G load and spread it out it simply means if you can use the crash to slow the de-acceleration. A good example is a race car running 200 MPH crashing into the wall. If it runs along the wall and scrubs off speed the driver walks away. If it crashed straight into the wall, well you can guess the outcome. You mention ground speed, but ground speed is not always a good measure. I would much rather crash at a flat angle with a higher groundspeed, than at a steep angle with lower ground speed.

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The Cirrus SR22 G5 has a new larger parachute (65 feet) to accommodate the increased weight up to 3600 pounds (now has a useful of 1260).  As of Jan 2014 the parachute has saved 85 lives, not counting the guy in the ocean yesterday.

 

The airplane will  descend under the canopy at less than 1700 fpm and ground impact equivalent to dropping from a height of 13 feet.   The seat and airbag belts will absorb most of that impact.

 

When the chute has been activated at or below 140kts (G5), above 400 in straight and level flight, or 920 in a spin, there have been zero fatalities.

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Tom, I mean under identical circumstances. If the only variable is ground speed, I'd prefer it to be slower rather than faster.

No matter what scenario is chosen, if the choices are land slowly or land fast but still flying and under control, I'll choose landing slowly.

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It is not fair state that is what you would do, until you know the circumstances that you are dealt.

 

Here is a hypothetical scenario. You are out flying at 3500 AGL, and a goose comes through the windshield. You are OK, and the airplane is still flying. You start to slow the airplane down and as you approach 70mph the nose starts to pitch down because the disrupted airflow is causing the tail to stall. You speed back up and have full control. You try it again with the same results. Would you land at 70 under control, or try and slow it down risking a hard pitch down somewhere below 70?

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There is a Latin phrase: ceteris paribus.

 

It means, "All things being equal".

 

All things being equal, slower is better than faster in accident scenarios.

 

I think that's what Jim was saying.

 

And I agree.

I agree if all things are equal, but that often is not the case. Almost nobody plans to crash, and when it does happen most times it is because of an emergency situation. I would much rather land in control at a faster speed if I thought the outcome would be favorable, as compared to out of control at a slower speed with the outcome in question.

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I agree fully that one would prefer to land in control at a faster speed than out of control at a slower speed. I hope none of us thinks otherwise. I certainly never intended to say or imply that I would want to land in a stall or otherwise out of control. I hope no one takes it that way.

 

The only question seems to be what is the lower end of the controllable airspeed. This is my point. That a skilled pilot who understands the effects of ground effect will use it to land under control slower.

 

I think I've stated my position about every way I can so I'll drop the subject.

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What matters is how they were taught to land the airplane, not whether they are skilled or understand ground effect. For the most part every landing every pilot has ever made is in ground effect. If the pilot is taught to land at the slowest possible speed during training then that is likely what they will do in an emergency. This happens not because they are skilled or have special understanding of ground effect, but because that is how they were taught.

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What matters is how they were taught to land the airplane, not whether they are skilled or understand ground effect. For the most part every landing every pilot has ever made is in ground effect. If the pilot is taught to land at the slowest possible speed during training then that is likely what they will do in an emergency. This happens not because they are skilled or have special understanding of ground effect, but because that is how they were taught.

Law of Primacy - when things turn brown you will revert to first learned actions. Something like that.

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