Advanced search  
Pages: 1 2 [3] 4 5 6   Go Down

Author Topic: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?  (Read 56267 times)

h.a.c. van asten

  • T4
  • ****
  • Posts: 322
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #30 on: June 09, 2011, 02:10:15 PM »

My earlier post should have said Marshall Islands not Marianas. I just did a calculation on the back of an envelope. If I understand Archimedes Principle right. 1200 gallons empty tanks displaces 1200 gallons of water at 8.35 Lbs./gallon. 8.35 x 1200 = 10020 lbs. Empty weight of AE's plane = 7265 lbs. Yes, it would float. I welcome any corrections.

Right , we do not know of course , but when tanks !/2 filled with water as an average , A/c would have a mass of 7,265 + 5,010 = 12,265 Lbs , 54,505 N ,  against a boyancy force of 22,264 N .
Logged

Chris Owens

  • T2
  • **
  • Posts: 64
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #31 on: June 09, 2011, 05:52:55 PM »

My earlier post should have said Marshall Islands not Marianas. I just did a calculation on the back of an envelope. If I understand Archimedes Principle right. 1200 gallons empty tanks displaces 1200 gallons of water at 8.35 Lbs./gallon. 8.35 x 1200 = 10020 lbs. Empty weight of AE's plane = 7265 lbs. Yes, it would float. I welcome any corrections.

Right , we do not know of course , but when tanks !/2 filled with water as an average , A/c would have a mass of 7,265 + 5,010 = 12,265 Lbs , 54,505 N ,  against a boyancy force of 22,264 N .

I'm sorry, but in a thread that has had a lot of silly calculations in it, this one takes the cake.   I'll leave finding the error as an exercise for the reader, but  here's a hint: Take a barrel, with a mass (empty) of 10 Kg, a capacity of 200 liters, and an exterior volume of 210 liters.  Punch it full of holes all over, so as soon as you toss it onto the surface of the sea, it fills with water.  How many such barrels would you need to tie to a floating soccer ball in order to sink it?

Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2901
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #32 on: June 09, 2011, 08:09:41 PM »

Take a barrel, with a mass (empty) of 10 Kg, a capacity of 200 liters, and an exterior volume of 210 liters.  Punch it full of holes all over, so as soon as you toss it onto the surface of the sea, it fills with water.  How many such barrels would you need to tie to a floating soccer ball in order to sink it?

Does the composition of the barrel make a difference?

Wood, metal, fiberglass, plastic?

10 kg of balsa wood might float better than 10 kg of steel.

Ah.  I guess you've specified the density of the material by saying that there is a 10 liter difference in the interior and exterior volume.  Whatever it is, it has a density of 1 Kg per liter, which at standard temperatures is the density of water itself.  It will be neutrally buoyant in the water and so it should float just beneath the surface, which means that you could never get enough barrels to sink your soccer ball (so long as we are using ties that also are at least neutrally buoyant).
LTM,

           Marty
           TIGHAR #2359A
 
Logged

Chris Owens

  • T2
  • **
  • Posts: 64
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #33 on: June 11, 2011, 08:27:08 AM »

Take a barrel, with a mass (empty) of 10 Kg, a capacity of 200 liters, and an exterior volume of 210 liters.  Punch it full of holes all over, so as soon as you toss it onto the surface of the sea, it fills with water.  How many such barrels would you need to tie to a floating soccer ball in order to sink it?

Does the composition of the barrel make a difference?

Wood, metal, fiberglass, plastic?

10 kg of balsa wood might float better than 10 kg of steel.

Ah.  I guess you've specified the density of the material by saying that there is a 10 liter difference in the interior and exterior volume.  Whatever it is, it has a density of 1 Kg per liter, which at standard temperatures is the density of water itself.  It will be neutrally buoyant in the water and so it should float just beneath the surface, which means that you could never get enough barrels to sink your soccer ball (so long as we are using ties that also are at least neutrally buoyant).

Bingo.   

As goes barrels, so go fuel tanks.   As the tanks fill with water and you want to calculate whether or not the airplane will still float, you can't count both the mass of water in the tank and the reduced air space. You need to count one or the other, otherwise you're double counting.

Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2901
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #34 on: June 11, 2011, 09:14:17 AM »

As goes barrels, so go fuel tanks.   As the tanks fill with water and you want to calculate whether or not the airplane will still float, you can't count both the mass of water in the tank and the reduced air space. You need to count one or the other, otherwise you're double counting.

I have no doubt you're right, but my powers of visualization are not keeping pace with the scenario.

Would you need calculus to figure out the rate at which a vessel sinks?  It seems to me that you've got a lot of things changing simultaneously--the change in the buoyancy provided by some air pockets or material less dense than water vs. the tug exerted by materials beneath the waterline that are denser than water.  It's not the weight of the water that sinks the boat; it is the weight of the materials denser than water that sink the boat (?).
LTM,

           Marty
           TIGHAR #2359A
 
Logged

Brad Beeching

  • T3
  • ***
  • Posts: 158
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #35 on: June 11, 2011, 09:24:58 AM »

..... and if the tank or tanks had fuel in it (them), then the calculations change yet again! Gasoline is lighter than water so it should help the tank float. Didnt a deep submersible (Trieste) use gasoline in a bladder above the capsule to provide floatation?

Brad
Brad

#4327R
 
Logged

Chris Owens

  • T2
  • **
  • Posts: 64
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #36 on: June 11, 2011, 09:43:17 AM »

As goes barrels, so go fuel tanks.   As the tanks fill with water and you want to calculate whether or not the airplane will still float, you can't count both the mass of water in the tank and the reduced air space. You need to count one or the other, otherwise you're double counting.

I have no doubt you're right, but my powers of visualization are not keeping pace with the scenario.

Would you need calculus to figure out the rate at which a vessel sinks?  It seems to me that you've got a lot of things changing simultaneously--the change in the buoyancy provided by some air pockets or material less dense than water vs. the tug exerted by materials beneath the waterline that are denser than water.  It's not the weight of the water that sinks the boat; it is the weight of the materials denser than water that sink the boat (?).

That's right.  (And we're getting mighty far afield here)... but (discounting the weight of the tank walls themselves) the net buoyancy of a submerged 100 liter tank with 50 liters of air and 50 liters of water in it is the same as the net buoyancy of a 1,000 liter tank with 50 liters of air and 950 liters of water in it.   

My main point was, a comment which should have read, "Yeah, but bear in mind that the empty fuel tanks would lose buoyancy as they took on water," instead introduced a calculation that offered precision without accuracy.... Beware quantitative answers to qualitative questions.


Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2901
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #37 on: June 11, 2011, 09:43:26 AM »

..... and if the tank or tanks had fuel in it (them), then the calculations change yet again! Gasoline is lighter than water so it should help the tank float. Didnt a deep submersible (Trieste) use gasoline in a bladder above the capsule to provide floatation?

Yes, the Trieste did using gasoline in its float:

"The sphere weighed 13 metric tons in air and eight metric tons in water (giving it an average specific gravity of 13/(13-8) = 2.6 times that of sea water). The float was necessary because of the sphere's density: it was not possible to design a sphere large enough to hold a person that would withstand the necessary pressures, yet also have metal walls thin enough for the sphere to be neutrally-buoyant. Gasoline (petrol) was chosen as the float fluid because it is less dense than water, yet relatively incompressible even at extreme pressure, thus retaining its buoyant properties and negating the need for thick, heavy walls for the float chamber. ...

"Nine tons of magnetic iron pellets were placed on the craft as ballast, both to speed the descent and allow ascent, since the extreme water pressures would not have permitted compressed air ballast-expulsion tanks to be utilized at great depths. This additional weight was held in place actively at the throats of two hopper-like ballast silos by electromagnets, so that in case of an electrical failure the bathyscaphe would rise automatically to the surface."
LTM,

           Marty
           TIGHAR #2359A
 
Logged

Jeff Scott

  • T2
  • **
  • Posts: 93
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #38 on: June 12, 2011, 03:02:19 PM »

Another item that puzzles me is why did the plane in the Hudson float? Presumably they had full fuel tanks. Or did they? What if somebody goofed and they took off with empty tanks? The bird story was concocted, but the plane floated nicely on it's empty tanks. Far fetched? Do they have air spaces built into these new jets? I am an incurable skeptic.

Airbuses are fitted with a "ditching button" allowing flight crew to "seal the aircraft" during a water landing to maximize buoyancy as long as possible.  Once activated, external valves and openings are closed to reduce the rate at which water enters the aircraft.  Apparently this wasn't used during the Hudson landing, however.  The pilot said it probably wouldn't have made much difference since the landing tore holes in the fuselage.

So long as they ditch relatively intact, most planes will float for a little while because of the buoyancy of internal tanks and aviation fuel being less dense than water.  They generally will flood and sink within a matter of minutes.
It's not too late to be great.
 
Logged

david alan atchason

  • T3
  • ***
  • Posts: 113
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #39 on: June 13, 2011, 04:58:16 PM »

Quote
If the airplane has fuel tanks (with fuel jettisoning provisions) that can reasonably be expected to withstand a ditching without leakage, the jettisonable volume of fuel may be considered as buoyancy volume

This quote is from the link in the previous post. It does not say that the fuel tanks will fill with water due to water coming in the vent. So do modern airplanes have self sealing vents so if you land on water you can jettison fuel and make yourself buoyant or more buoyant? Did they have such a system in 1937? I would guess not, but if AE's plane did have that modification it might float for a while. To me, that might be relevant in some which way. That's all I'm saying, and that is why I originally raised this issue. I was just curious.
Logged

Chris Owens

  • T2
  • **
  • Posts: 64
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #40 on: June 14, 2011, 08:35:49 AM »

One can argue barrels and apples all day long, but planes sink - eventually.

Another crummy fact about ditching - there are too many variables and such an event is highly unpredictable. 

That was sort of my intended point... that the answer is, "A ditched plane will float for a while, depending upon how much damage you do during the ditching."  We have no way of knowing how much damage was done, so therefore we have no way of knowing how long "a while" is.  Attempts to introduce calculations are silly, especially when those calculations are wrong.
Logged

h.a.c. van asten

  • T4
  • ****
  • Posts: 322
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #41 on: June 16, 2011, 08:29:45 AM »

One can argue barrels and apples all day long, but planes sink - eventually.

Another crummy fact about ditching - there are too many variables and such an event is highly unpredictable.

That was sort of my intended point... that the answer is, "A ditched plane will float for a while, depending upon how much damage you do during the ditching."  We have no way of knowing how much damage was done, so therefore we have no way of knowing how long "a while" is.  Attempts to introduce calculations are silly, especially when those calculations are wrong.

In a  nosing down Electra due to the heavy engines ,   you can´t climb up to the tail door , so you must leave through the top cockpit hatch , making water immediately if you might succeed in opening it .
Logged

Chris Austin

  • T2
  • **
  • Posts: 58
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #42 on: June 16, 2011, 09:13:53 AM »

One can argue barrels and apples all day long, but planes sink - eventually.

Another crummy fact about ditching - there are too many variables and such an event is highly unpredictable.

That was sort of my intended point... that the answer is, "A ditched plane will float for a while, depending upon how much damage you do during the ditching."  We have no way of knowing how much damage was done, so therefore we have no way of knowing how long "a while" is.  Attempts to introduce calculations are silly, especially when those calculations are wrong.

In a  nosing down Electra due to the heavy engines ,   you can´t climb up to the tail door , so you must leave through the top cockpit hatch , making water immediately if you might succeed in opening it .

Without wishing to start another interminable discussion, that is pure conjecture (again), even with the extra tanks to crawl over. Many aircrew have escaped from seemingly impossible crash scenarios over the years whilst others have perished when escape seemed simple. It is amazing what can be achieved when your life depends on it.
Personally, whilst I (thankfully) have no experience of an air accident, I once crashed a race car that I had to wriggle into to get seated with getting out a similar experience. After the crash I was out like a greased eel, I don't think I touched the sides!
Logged

h.a.c. van asten

  • T4
  • ****
  • Posts: 322
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #43 on: June 16, 2011, 10:27:32 AM »

One can argue barrels and apples all day long, but planes sink - eventually.

Another crummy fact about ditching - there are too many variables and such an event is highly unpredictable.

That was sort of my intended point... that the answer is, "A ditched plane will float for a while, depending upon how much damage you do during the ditching."  We have no way of knowing how much damage was done, so therefore we have no way of knowing how long "a while" is.  Attempts to introduce calculations are silly, especially when those calculations are wrong.

In a  nosing down Electra due to the heavy engines ,   you can´t climb up to the tail door , so you must leave through the top cockpit hatch , making water immediately if you might succeed in opening it .

Without wishing to start another interminable discussion, that is pure conjecture (again), even with the extra tanks to crawl over. Many aircrew have escaped from seemingly impossible crash scenarios over the years whilst others have perished when escape seemed simple. It is amazing what can be achieved when your life depends on it.
Personally, whilst I (thankfully) have no experience of an air accident, I once crashed a race car that I had to wriggle into to get seated with getting out a similar experience. After the crash I was out like a greased eel, I don't think I touched the sides!

Of course it is , no discussion necessary but expectations for the Electra NR 16020 crew were not favorable to say the least . B.t.w. something better  is valid for the "van Asten sunrise" -fix : R.Nesbit , experienced A/c navigator in the Earhart era , later during WW-II in the USAAF , quotes the sunrise fix in Missing Believed Killed in a paragraph ´Fixing of Position based on Sunrise´ ; he also believes such sunrise fix was established between the 200 & 100 mls out messages of 1744-45 & 1615 GMT . The book is of 2002 , I have my knowledge not from this source , so it is an additional one I up to now did not know of .
Logged

Ric Gillespie

  • Executive Director
  • Administrator
  • *
  • Posts: 5320
  • "Do not try. Do or do not. There is no try" Yoda
Re: Could Earhart’s Transmitter Operate If Her Plane Was Afloat?
« Reply #44 on: June 16, 2011, 10:31:06 AM »

The book is of 2002 , I have my knowledge not from this source , so it is an additional one I up to now did not know of .

You have no monopoly on baseless speculation.
Logged
Pages: 1 2 [3] 4 5 6   Go Up
 

Copyright 2018 by TIGHAR, a non-profit foundation. No portion of the TIGHAR Website may be reproduced by xerographic, photographic, digital or any other means for any purpose. No portion of the TIGHAR Website may be stored in a retrieval system, copied, transmitted or transferred in any form or by any means, whether electronic, mechanical, digital, photographic, magnetic or otherwise, for any purpose without the express, written permission of TIGHAR. All rights reserved.

Contact us at: info@tighar.org • Phone: 610-467-1937 • Membership formwebmaster@tighar.org

Powered by MySQL SMF 2.0.15 | SMF © 2017, Simple Machines Powered by PHP