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Author Topic: Did Earhart carry parachutes on the flight to Howland  (Read 319566 times)

Chris Johnson

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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #406 on: March 17, 2012, 05:56:00 PM »

Quote
Do you have any examples of a jumper hitting the tail of the plane he jumped from?

I was poking around on Youtube today and saw some chutes getting caught on the tail. People were getting sloppy at the door and almost lost their life. Interesting to watch.
Even in the u-tube video the jumper did not hit the tail, only the parachute did. Of course you are always careful to prevent the chute from opening prematurely, students are taught to protect the ripcord when moving about in the plane but that was always a danger that had been recognized and is the reason we jump pilots also wore chutes.

gl
« Last Edit: March 17, 2012, 07:17:10 PM by Gary LaPook »
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John Ousterhout

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #407 on: March 17, 2012, 06:00:13 PM »

My favorite professor (Wayne Phillips, RIP) was a WWII P-38 survivor of 5 parachute exits.  Note - when exiting a P-38 cockpit in level flight, the pilot leaves the cockpit at a level significantly above the horizontal stabilizer, making one think seriously of the laws of physics that Gary has mentioned.   Wayne said he perfected his exit procedure thus:  after verifying it was time to leave the aircraft, 1) cinch the parachute straps, 2) get rid of the canopy, 3) crank the seat all the way up, 4) release the seat belt, and 5) roll the plane upside-down, push the stick forward, and fall out, well-clear of the meat-cleaver horizontal stabilizer.
He also claimed to have invented a drink that combined French Gin and powdered orange juice, called a "Phillips screw-driver".  I miss him.
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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #408 on: March 17, 2012, 06:58:38 PM »


Gary
Yes, generally the "Jumper" will be below the plane since he/she has the same forward velocity as the plane when he/she exits, (now comes the "however") however the Jumper's body is less streamlined than the plane so it has a bit more drag (force in opposite direction to direction of motion) slowing it down relative to the plane.  Whether it would be enough to cause the Jumper to strike the "H" tail of an Electra?  Possibly.  Depends on the configuration of the Jumper's body.
Of course we have all seen a Jumper achieve a position where he/she can minimize that drag and actually appear to be "flying".

Of course, as a former artillery officer, you know that a body falling out of a plane, a bomb dropped from a plane, an artillery shell fired into the air travels in a trajectory that is roughly parabolic.  Thus, the Norden Bomb Sight solved the geometry (trigonometry) of that configuration and allowed nuch more accurate bombing.  That's why the development of that sighting devive was "Top Secret".
I just remembered Harry, you're a physicist, you can figure it out for us. I'll give you some data to work with. A skydiver, falling face to earth, grabbing as much air as he can in the maximum drag position, reaches a maximum terminal velocity of 120 mph IAS, say 180 feet per second. If you want to go faster you put your arms against your sides, spread your feet a little bit so that they act like the feathers on an arrow, and this makes you then fall head first in a minimum drag orientation so you then accelerate to a terminal velocity of about 200 mph IAS, say 300 feet per second. When you leave the plane  you are in the horizontal position so you present this minimum drag attitude to the relative wind. Let's say the Jumper weighs 200 pounds with his equipment and, to make this easy, let's say the plane is flying at 100 mph, 150 feet per second at 10,000 feet where the air density is .00175 slugs per cubic foot.

Never mind, I can do this one in my head. Since terminal velocity in this attitude is 300 feet per second we know the drag must equal the jumper's weight, a drag force of 200 pounds. Leaving the plane that is going half that fast, 100 mph, 150 feet per second will produce a drag force 1/4th of 200 pounds because drag varies with the square of the velocity, only 50 pounds, 1/4 of the jumper's weight and this will cause the jumper to accelerate towards the tail at 1/4th g, 8 feet per second per second. So after the first second the jumper will be 4 feet back but he will also be about 16 feet down. After two seconds the jumper will be 16 feet back, say about directly under the tail, and down about 64 feet. So the tail passes over the jumper 64 feet above him, about like a window in a six story building. Pretty hard to get hit by the tail.

gl
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Heath Smith

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #409 on: March 17, 2012, 08:22:19 PM »


That is an interesting discussion about the physics of the jump.

Looking around a bit I found this article about someone that died on jump hitting the horizontal stabilizer on a King Air. Apparently he had jumped up a bit on exit and this is what caused his untimely death.


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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #410 on: March 17, 2012, 09:28:58 PM »


That is an interesting discussion about the physics of the jump.

Looking around a bit I found this article about someone that died on jump hitting the horizontal stabilizer on a King Air. Apparently he had jumped up a bit on exit and this is what caused his untimely death.
Thanks, I forwarded that on to my daughter's fiance, he is a begining skydiver.

gl
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Harry Howe, Jr.

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #411 on: March 17, 2012, 10:13:40 PM »


Heath
Very interesting indeed.  In physics, as in life, and ocean currents, the Devil is in the details and in the initial conditions.  I must confess, I can't imagine why a "jumper" would jump up when exiting a plane.

Gary
In my post , when I was referring to a "jumper" I wasn't referring to one that conciously(sp?) exited the plane and achieved a horizontal "grabbing air" position and then went into the heads- down, low drag configuration.  I was more like thinking of someone exiting from a plane in trouble, not a trained chutist.

I do agree that in most circumstances hitting the tail would be an unusual occurrence.  I'm not sure about the possibility of hitting  a vertical stabilizer (two of them) on an "H" tailed plane like the Electra.
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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #412 on: March 17, 2012, 11:53:26 PM »



I remember one jump I made on which I talked the jump pilot into trying something different. After I was standing out on the wheel strut and holding onto the wing strut I had the pilot dive the plane to pick up some extra speed. He then pulled up into a steep climb using the extra speed to permit a high rate of climb. Then, while we were still going up, the pilot rolled to the left and pushed the nose down and I let go and, since the plane was still going up at the instant that I let go, I continued to go up for about 2 or 3 seconds, I could feel myself stop going up and then start going down (it was a weird feeling) and I remember looking down on the jump plane below me silhouetted against the ground and the pilot looking up at me through the open door. It was way cool but I could never talk the pilot into doing it again.

gl
I dug out my logbook and it turns out I  made this "Negative G exit" on May 31, 1971 as my 167th jump. The reason that the pilot wouldn't do this again is he said looking up at me above the plane scared him that I would fall down back into the plane. Explaining the physics to him didn't help. I find interesting the story posted by Heath about a jumper that managed to hit the tail by "jumping up" a foot  when he left the plane, on my jump I was well above the plane at the top of my trajectory. But I had worked it out beforehand and the key to my jump being safe was having the pilot roll left into a steeply banked left turn before I left the plane. This put the plane into a rapid left turn while I went straight ahead so the plane was never directly below me.

gl
« Last Edit: March 18, 2012, 02:34:23 AM by Gary LaPook »
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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #413 on: March 18, 2012, 03:15:24 AM »


Heath
Very interesting indeed.  In physics, as in life, and ocean currents, the Devil is in the details and in the initial conditions.  I must confess, I can't imagine why a "jumper" would jump up when exiting a plane.

Gary
In my post , when I was referring to a "jumper" I wasn't referring to one that conciously(sp?) exited the plane and achieved a horizontal "grabbing air" position and then went into the heads- down, low drag configuration.  I was more like thinking of someone exiting from a plane in trouble, not a trained chutist.

I do agree that in most circumstances hitting the tail would be an unusual occurrence.  I'm not sure about the possibility of hitting  a vertical stabilizer (two of them) on an "H" tailed plane like the Electra.
O.K. let's look at that. The worst case situation would be a person presenting himself to the airstream in the maximum high drag position. We already know that this is the position that results in a 120 mph terminal velocity and is the position normally used by skydivers. You can't get more drag than this. So let's do the math using a reasonable jump speed of 80 mph, which is the speed used for landing approach. Exiting at 80 mph will cause the jumper to accelerate towards the tail at a rate of 0.81 g since 80 mph is 2/3rds of the 120 mph terminal velocity and the square root of 2/3rds is 0.81. One g is 32 feet per second per second so 0.81 G equals 26 feet per second per second. The distance covered by a constantly accelerating body equals 1/2 acceleration multiplied by time squared (D= 1/2 at^2.) If we solve for the time necessary to cover a specified distance, the formula becomes t = square root (2 dist/a). It is 6.9 feet from the Electra's door to the horizontal stabilizer, I have attached a diagram of the plane and you can scale it off for yourself. Since the maximum acceleration towards the tail is 26 feet per second per second the formula gives 0.73 seconds to go back to hit the tail. But the acceleration towards the ground is 1 g, 32 feet per second per second, so the first formula shows that this same person will have fallen 8.5 feet in the time it would take to go back and hit the tail. And, unlike the King Air's tail, the horizontal stabilizer on the Electra is mounted on top of the fuselage, 4.1 feet above the bottom edge of the door, 0.8 feet higher than the King Air's. So assuming a jumper was bent over a little bit, he would already be below the horizontal stabilizer when he left the plane. Or using the same methodology used in the King Air case, the jumper's center of gravity is 2.875 feet above the bottom of the door and would fall 8.5 feet by the time the tail passed over, and since the tail started off being 1.225 feet above the jumper's COG, the tail would pass over the jumper's COG by 9.7 feet.

If we consider the very unreasonable jump speed of 150 mph, the cruise speed of the plane, and doing the same math we find that the acceleration towards the tail is 50 feet per second per second, the time to reach the tail is 0.52 seconds during which time the jumper's COG will fall 4.4 feet and pass 5.6 feet below the tail. The King Air discussion states that a miss distance of 5 feet will prevent hitting the tail.

As to hitting the vertical stabilizer, it is 7 feet out from the fuselage. Can you do a standing broad jump of 7 feet? I didn't think so.

gl
« Last Edit: March 18, 2012, 03:53:47 AM by Gary LaPook »
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Harry Howe, Jr.

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #414 on: March 18, 2012, 10:18:16 AM »


Gary
Thanks again for the refresher course in Dynamics 3101.  I remember taking that course in 1960.

I guess that in the King Air case, where the physics of the situation would predict that the "jumper" couldn't hit the horizontal stabilizer, there nust have been a problem with the initial  conditions assumed for the calculations because he did hit the stabilizer.


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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #415 on: March 18, 2012, 11:06:15 AM »


Gary
Thanks again for the refresher course in Dynamics 3101.  I remember taking that course in 1960.

I guess that in the King Air case, where the physics of the situation would predict that the "jumper" couldn't hit the horizontal stabilizer, there nust have been a problem with the initial  conditions assumed for the calculations because he did hit the stabilizer.
In the King Air accident the physics shows that he would hit the tail but nobody would have done that computation prior to the accident because common wisdom, as proved by millions of jumps, is that you can't hit the tail.

gl
a
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Harry Howe, Jr.

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #416 on: March 18, 2012, 11:16:14 AM »


I guess that "common wisdom" was wrong, oops the jumper died.
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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #417 on: March 18, 2012, 12:53:26 PM »


I guess that "common wisdom" was wrong, oops the jumper died.
Yep, but he had to work at it. It is also common wisdom that it is very unlikely to be struck by lightning but people get killed by lightning every year. An extremely rare event does not disprove the common wisdom.

gl
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Monty Fowler

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #418 on: March 18, 2012, 06:12:17 PM »

Getting back to the original question, there was a point to these, what. 30-plus pages of spirited debate and enlightened conversation, right?

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Monty Fowler, TIGHAR No. 2189 CER
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Gary LaPook

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Re: Did Earhart carry parachutes on the flight to Howland
« Reply #419 on: March 21, 2012, 04:41:06 PM »



A couple of things that I can think of. One, she was paranoid about un-necessary weight. In her telegram from Lae she indicated that she had never traveled lighter. In an interview with Putnam they joked about him coming along and she said that she would rather have the 180lbs of fuel. So she was always equating the weight of the object versus the equivalent fuel. I am not sure how much a pack weighed back in the day but I am sure they were not light light a modern parachute. What would you guess, 20 pounds times 2, 40 pounds for the chutes? 40 / 6lb = 6.6 Gallons?


That is because Putnam would have been of no use on the flight (maybe in the hotel...) so the fuel, which did have a use, was better to have aboard. However, parachutes might prove to be useful on the flight, and if the occasion actually came about, they would be VERY USEFUL, so it changes the equation to favor giving up 6.6 gallons and replacing that with parachutes. And, that is a false choice anyway since Earhart did not restrict her fuel load on takeoff from Lae because of concern about weight but because she believed she could get more power with undiluted 100 octane fuel. And she never flew any other leg with full fuel tanks  either. And 6.6 gallons equates to only 7 to 10 minutes of flying time, at most 25 miles, and the plane, according to fuel computations, had a very large reserve at the time of takeoff so 6.6 gallons was of no importance.

gl
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