Why is this video of a G36 Bonanza so 'scary'?

If they had clipped the top of the trees, would it really have brought the plane down? (And even if yes, it looks pretty survivable).

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    $\begingroup$ On what basis do you think falling to the ground several hundred feet below while going 70 MPH is "survivable"? Such a car crash would frequently be fatal, and cars have far more safety features than small planes. $\endgroup$ – abelenky Jan 10 '19 at 15:05

Because those trees will kill them

If you look at this document regarding the Bonanza G36 performance you will note that the lowest stall speed written is 61 kts. 61 kts is 112 kph or 71 mph. We can assume they were going a little bit faster than that but let us say 110 kph / 70 mph.

In that clip, they are just barely keeping airborne. This means the aircraft is extremely sensitive to disruptions. Any loss of power — even partial — or getting knocked back by a collision and thus losing a few knots or upsetting the aerodynamics of the aircraft, is very likely to send it crashing into the trees.

Going 110 kph / 70 mph into a tree is rarely survivable even in a car, and then you have to remember that cars these days are built to withstand crashes while at least keeping the occupants alive, but that assumes crashing into something wide, that distributes the forces over a wide area, and that gives way, like another car. Trees fail that on both accounts.

A G36 does not even come close to any such structural integrity in case of a crash. The cabin will crumple like figurative tin foil, sending the occupants smashing into the trunks of the trees, or throwing them clear of the aircraft only to then smack into other trees or the ground from several meters up and at a high speed. And that is going to be fatal.

Hence, this is scary because if they clip a tree they are very likely to die.

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    $\begingroup$ I found out a bit more about this incident... it seems that one of the passengers wasn't honest about their weight and they had already dumped fuel to be inside the flight envelope (probably why the stall warning sounded as soon as they rotated?)... Thanks for the answer :) $\endgroup$ – Cloud Jan 10 '19 at 14:36
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    $\begingroup$ The survivability of that kind of crash is basically a crap shoot. The rear seat pax will almost certainly live if there's no post crash fire. The front seat occupants, it will depend on the sorts of things they run into during the crash sequence and how much the front end of the cabin is deformed. They might get lucky, they might not. Coniferous trees are better than deciduous trees and can be like landing in a big hair brush if they are small and dense. Bigger ones, not so good. If an engine quits while I'm over a forest carpet, I'm heading for small conifers if I can identify them. $\endgroup$ – John K Jan 10 '19 at 14:43
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    $\begingroup$ @JohnK I never knew dendrology would be useful in aviation ;) $\endgroup$ – Cloud Jan 10 '19 at 15:02
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    $\begingroup$ I was not criticizing your good answer @MichaelK. What I mean is that the pilot got in that position by not taking it into account, among other things. $\endgroup$ – GdD Jan 10 '19 at 15:32
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    $\begingroup$ @BluegillPrime Ingest a branch into the propeller, buckle a leading edge, cause a startle that makes the pilot make a maneuver... anything at that point may eat up the last little margin they have. $\endgroup$ – MichaelK Jan 14 '19 at 19:15

They Trimmed the Margins to Zero

In this video, the aircraft takes off and flies a straight course through the trees and continues a shallow climb out. To the uninitiated, this may appear innocuous, until one realizes that the aircraft was performing at it's maximum limits with near zero room for error.

The voice and narration of this video does a good job breaking down what happened in this scenario, to recap in writing:

The pilots appear to have calculated the takeoff performance, found it to be adequate and made their attempt. Their calculations were likely correct, but sufficiently lacking in margin so as to excite those on board who were cognizant of the situation.

It is reasonable to assume that aircraft performance tables are generated under near ideal and non-threatening conditions.

It is also reasonble to assume that:

  • A pilot who flies recreationally may not be able to squeeze every bit of rated performance out of their aircraft.

  • Mistakes can be made in the calculation of weight and balance which affect performance.

  • Conditions may change between the time calculations are made and time of takeoff.

Near the end of the commentary, the pilots can be heard verbalizing their learning experience. I think the lessons of the experience are not lost on them.

Lessons of aircraft performance are somewhat frightening to me as an aspiring instructor. Training usually occurs at one airport, often with a long runway, with one aircraft or type of aircraft and one loading scenario. If the training is compressed into a few months, the student may not even be exposed to a significant range of weather conditions.

I intend to teach my students to be awake to the amount of runway they are using and load the aircraft in multiple configurations as part of the training. I think many pilots have a moment of nervous surprise the first time they experience narrowing margins. I would like it to be less of a surprise.

Learn from this video, and from this other one, which had a less fortunate ending:

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  • $\begingroup$ As long and explanatory as this post is, it still does not answer the question: why is this (considered) scary. You are explaining how they go into the situation — and admirably so — but the question was not that, but why the situation is considered scary. $\endgroup$ – MichaelK Jan 11 '19 at 8:18
  • $\begingroup$ What was the cause of the crash in the video you posted? Was he intentionally flying low like that? $\endgroup$ – Cloud Jan 11 '19 at 10:00
  • $\begingroup$ @MichaelK To me, the human behavior of failing to provide margin is a hazardous, and potentially mortal error. That someone would entertain an attempt an operation on the grounds of a calculation with zero factor of safety frightening not only on account of the operation, but that they may have developed a habit of doing so. $\endgroup$ – 2NinerRomeo Jan 11 '19 at 21:09
  • $\begingroup$ @Cloud, very doubtful that the low flight was on purpose. The NTSB report cites a failure of the pilot to account for air density (density altiude), which is a factor in figuring takeoff performance. The air density was simply too thin for the aircraft to climb with the load it had. Additional scariness comes from how poorly this facet pf performance is understood and applied among pilots. app.ntsb.gov/pdfgenerator/… $\endgroup$ – 2NinerRomeo Jan 11 '19 at 21:21
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    $\begingroup$ Said another way, this video is scary because is represents an unfortunately too common occurrence of pilots being unfamiliar with performance limitations, or failing to recognize when they are near the edge of their aircraft's capability. This may merit another answer on it's own. So, @MichaelK, we have at least three reasons: 1. Trees will kill you, 2. These Pilots made a mistake (which they are less likely to repeat after this experience), 3. Too few pilots realize this problem and may have to learn it on their own, endangering theirs and others lives. $\endgroup$ – 2NinerRomeo Jan 11 '19 at 21:44

What makes it scary is just how close they did come to an accident. They attempted a takeoff using the performance calculations listed in the POH on a hot day at high field elevation. That’s fine assuming EVERYTHING works out just like the book ie no errors in calculating performance, aircraft and engine in peak condition, field atmospherics, perfect short field takeoff technique, etc. But as the video showed, they came damned close to clipping the tree tops on climbout.

The aircraft in question was a turbonormalized G36 departing from Mears Airport (3W5) in Concrete, Washington. The small country airport is located in a river valley surrounded by mountains. According to the pilot the performance calculations show that the aircraft could do it, and so he attempted to try it. Fortunately he managed to weave his way through the trees at just under stall speed to get clear of obstacles and clean up and accelerate the aircraft out of the reverse side of the power curve. The film is scary because it shows just how close he came to having a controlled flight into terrain or striking obstacles. Mountainous terrain quite often has downdrafts coming through the valleys on the windward side. Had he encountered one, he would have never made it.

The airport is built on a small flat land surrounded by rough terrain. Had a pilot collided with the treestops at the end of the runway, there was a good chance that he would have lost control and crashed. The likelihood of survival in a situation like that, particularly in a high-performance airplane like a bonanza climbing out at 80+ knots, is not great.

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