Altitude + Weight + Insufficient Curvature of Earth

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reubee
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Altitude + Weight + Insufficient Curvature of Earth

Postby reubee » Thu Aug 09, 2012 6:59 am

http://www.liveleak.com/view?i=835_1344412426

The long take-off roll should be a clue as to what eventually happens. Also note when the second camera angle is shown near the end, the angle of attack
Image

Ed
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Ed » Thu Aug 09, 2012 11:29 am

Tough to watch as you can see the plane struggling to even get airborne. The fact that he had that a/c loaded up like a clown car didn't help. Also, all this reference to 'air pocket'.....possibly, but also possibly the transition from flat to rough surface changed the shear conditions which to compensate required control surface input which will ever so slightly change the aerodynamics...in an aircraft which is obviously underpowered for the mission. Anyone who has flown a glider knows to beware the transition.....

Sort of reminds me of the L19 gaff:
http://www.youtube.com/watch?v=9AzXyAtOuG0

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Gabriel
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Gabriel » Thu Aug 09, 2012 4:19 pm

Air pocket my ass.
This plane didn't have the power to climb, be that due to density altitude (hot and high) or weight (or in fact, a combination of both).

- He most likely didn't do the take-off performance calculations. I know that they are mostly never done in these kind of flying, but the reason to justify that is that there is usually a lot of performance margin and pilots are used to do take-offs in usual conditions and they know how much margin they have. When the runway is somehow short (compared to usual), or the conditions are somehow questionable (high and hot), the above excuse is not longer valid.
- The pilot faces a first failure to climb when the plane settles back on the runway after the first lift-off. In this case, the expected conservative reaction would be to abort. Take-off is doubtful. Abort is easy and safe. And it gives you time to go check the numbers.
- Then there is a second failure to gain altitude after the second lift-off, still with runway remaining ahead. Now landing is more dangerous, there is a possibility of overrun. But the take-off has become highly questionable if not absolutely proven impossible by then. And a subsequent almost surely unavoidable contact with ground, gets much more dangerous. The pilot still takes the high risk stake.
- The runway is behind. Still flying low. Any attempt to climb results in a subsequent descent. THE PLANE WON'T CLIMB PERIOD! Flat field below and ahead. After that trees. Regardless of how reckless you are, is there any rational chance other than landing? A risk stops being a risk when the loss is sure. Playing Russian Roulette is risky. Playing with all bullets is irrational unless you are actually willing to loose.
- They barely managed to escape the first minor line of trees. Before the next forest we have a nice field. Miracle! God gave us another chance! Nah, let's keep going????

There is a speed called best rate of climb speed or Vy (which at the limit, when the best climb becomes zero, coincides with the best climb gradient speed or Vx, because any other speed, faster or slower, will result in a decent). Even if you have an ridiculously long runway, the best you can do is to accelerate on the runway (or just above it in ground effect) until you reach Vy, and then climb at Vy, thus converting any excess power that you had so far ONLY into altitude (the same excess power that so far let you keep accelerating to Vy). The Problem is that as you climb out of ground effect the drag increases, so the excess power can be not in excess anymore. What will happen, if you keep doing the best thing you can do that is keeping Vy by all means, the plane will settle at some point where the thrust equals the drag (somewhere between zero altitude and an altitude where the ground effect is negligible) and won't climb anymore (nor will it descend, or gain speed, or loose speed).

So, in short, no matter how f***ing good pilot you are. If you can't keep a sustainable climb at Vy then the plane won't climb period. Even ITS, Texan and all, can't beat Newton.

So, did the pilot really want to kill himself ad those with him? I don't think so.
He most likely was in disbelief. At some point he stopped being rational. He didn't "decide" to do what he did. He quit deciding altogether.
A pilot must be prepared to give up. Not "completely", but with the current objective.
At some point, the pilot must be ready switch from "what's the best I can do to make it" to "How can I NOT make it in the best way".
Accepting that you are going to crash and changing yourself from "mission" mode to "survival" mode is tough.
But usually, like in this case, the pilot has opportunities to stop the sequence short of that, at a point where the mission won't be accomplished (although it's not completely clear yet that it CAN'T) but an alternative safe course of action will (like aborting the take-off when the plane maybe would have been able to climb, or to stop for fuel when we still might make it to the destination, or landing in this nice field clearly within reach when we could maybe make the runway after passing that forest).

All the above said, the pilot at least made a nice job at not trying to make an impossible climb, stall, spin, crash, burn and die.

Ed
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Ed » Thu Aug 09, 2012 6:28 pm

That pilot was past his due date.

Also, they are lucky they jizzed into a bunch of small, dead and dry trees........

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3WE
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby 3WE » Fri Aug 10, 2012 11:05 pm

Two words:

"Tunnel Vision"
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

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3WE
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby 3WE » Sun Aug 12, 2012 8:43 pm

...that rule of thumb that you 'never' take your hand off the throttle...

...pretty compliant...
Commercial Pilot, Vandelay Industries, Inc., Plant Nutrient Division.

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flyboy2548m
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby flyboy2548m » Mon Aug 13, 2012 6:20 pm

Air pocket my ass.
This plane didn't have the power to climb, be that due to density altitude (hot and high) or weight (or in fact, a combination of both).
That's all you needed to say. Too bad it's not in you not to spew 8,000 words per minute.
"Lav sinks on 737 Max are too small"

-TeeVee, one of America's finest legal minds.

GlennAB1
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby GlennAB1 » Mon Aug 13, 2012 6:23 pm

But then we wouldn't have got your expert comment, FB!
you still have to find a crew willing to fly this "barely airworthy" heap
no such thing as "barely airworthy" it's either Airworthy or Not
100% incorrect Ever hear of Ferry Permit? issued for Non airworthy aircraft
LOL

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Gabriel
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Gabriel » Mon Aug 13, 2012 6:54 pm

That's all you needed to say. Too bad it's not in you not to spew 8,000 words per minute.
Parlor talker. You don't know how long it took to spew those 8,000 words. :?
(or in fact, to spew some 16,000 words and then edit it to half it, because it was too long)

PurduePilot
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby PurduePilot » Tue Aug 14, 2012 7:55 pm

But then we wouldn't have got your expert comment, FB!
What a shame...

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Ancient Mariner
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Ancient Mariner » Tue Aug 14, 2012 8:55 pm

That's all you needed to say. Too bad it's not in you not to spew 8,000 words per minute.
Parlor talker. You don't know how long it took to spew those 8,000 words. :?
(or in fact, to spew some 16,000 words and then edit it to half it, because it was too long)
Actually, it is just 775 although I do not know how long it took Gabriel.
Per

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Gabriel
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Gabriel » Tue Aug 14, 2012 9:36 pm

just 775
Thank you :?

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Not_Karl
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Re: Altitude + Weight + Insufficient Curvature of Earth

Postby Not_Karl » Wed Aug 15, 2012 2:34 am

Actually, it is just 775 although I do not know how long it took Gabriel.
Per
With a speed of 8000 WPM, almost six seconds. That's amazing.
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