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Author Topic: Physics Question  (Read 3101 times)

Don White

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Re: Physics Question
« Reply #15 on: March 12, 2022, 12:04:17 PM »

Ric says: The steam from a coolant failure is purely my conjecture.

Which brings up a question I have had: is it known what, besides water, was in the cooling system? Antifreeze coolants were in their infancy; many drivers simply didn't drive in freezing weather or drained the system every night and filled it with hot water before starting in the morning. I have a 1920s book with recipes for making your own antifreeze (water, alcohol and glycerine). Hydraulic fluid, too (castor oil and kerosene).

LTM
Don W who is quite happy to be indoors watching the freezing weather today!
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Don White

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Re: Physics Question
« Reply #16 on: March 12, 2022, 12:08:33 PM »

Eyewitness accounts Ric detailed in the last TT describe the plane streaming white "smoke" or vapor, not black smoke as would be expected from and engine fire, so I doubt anything catastrophic happened until it touched down and hit the island.

To be clear:  Only one witness, John Dobbin (for whom we have only a second hand anecdotal account from 1993), said he saw smoke and he said nothing about the color.  The St. Mary's witnesses Cotton talked to in 1927 said only that they saw an airplane "on fire."  The steam from a coolant failure is purely my conjecture.

Good question. The only likely source of ignition in flight would be the engine ignition system. There would have to be a path for a spark to go where it wasn't wanted.

If the engine overheated due to a coolant leak, could that cause a fire? Probably not. But a coolant leak could have been the cause of the emergency landing.

Don W
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Don White

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Re: Physics Question
« Reply #17 on: March 12, 2022, 12:12:45 PM »

Ric - "But the landing at the Gull Pond was not a normal landing, so I would expect the crash trajectory would be shorter than a normal landing run."

Even less normal if the plane flipped over on hitting the water as was previously asserted that it would almost certainly have done.

LTM,
Don W
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Ric Gillespie

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Re: Physics Question
« Reply #18 on: March 12, 2022, 01:15:16 PM »

Which brings up a question I have had: is it known what, besides water, was in the cooling system?

That's not mentioned in any of the literature I've seen.
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James Champion

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Re: Physics Question
« Reply #19 on: March 13, 2022, 09:15:46 AM »

The "three explosions in rapid succession" heard by Nicholas McGrath may not necessarily indicate there were three explosions. McGrath would have been several miles away. Atmospheric acoustic ducting could have caused one explosion to be heard as several as the sound took different paths and different delays as the sound is refracted back towards the surface.
https://asa.scitation.org/doi/10.1121/1.1974646
Similar to the short cell phone video where the sound of the Tonga explosion was recorded some 40 km away. Multiple pops and bangs, as many as eight, are heard over several seconds.
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Ric Gillespie

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Re: Physics Question
« Reply #20 on: March 13, 2022, 10:48:24 AM »

Here's a question:
At what speed did Nungesser use to fly his approach to land on the pond?

It's important because the accuracy of his approach speed effects his ability to land where he wants to land, but to hit the spot you want to hit, you have to know the airplane's stalling speed at its current weight and configuration.

According to the French Ministry of Transportation Report, Nungesser made numerous test flights in the PL-8 but always with the landing gear in place and never at a takeoff weight greater than 3,500 Kg (7,716 lbs). Landings would presumably be close to the plane's empty weight, about 1,500 kg (3,300 lbs).  At that weight the wing loading was very low and the stalling speed would be around 35 mph.

 Faced with making an emergency landing at a weight far heavier than he had previously experienced, Nungesser was in unexplored territory.  At what speed would the plane stall?  At what speed should he fly the approach?  He undoubtedly knew how much fuel he had left so, in theory, he could calculate his weight and wing loading to estimate stalling speed but, under the circumstances, it seems more likely he went with his gut.  Get too slow and it's stall/spin, game over.  Safest to play if safe and come in hot. 

He makes his descent at his chosen speed and levels out close to the water (which can be hard to judge if the surface is calm) and waits for the speed to bleed off until the plane stalls onto the water - as in any full-stall landing. But if the stall speed is slower than he expected, the aircraft "floats" in ground effect much farther than he anticipated before touching down.  The normal solution to a misjudged approach is a go-around, but he didn't have that option.

This is all speculation, but it could explain how Nungesser ended up touching down much closer to the island than he ever intended.



« Last Edit: March 14, 2022, 11:00:33 AM by Ric Gillespie »
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Ric Gillespie

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Re: Physics Question
« Reply #21 on: March 14, 2022, 11:28:41 AM »

Another thought (does this stuff keep anyone else up at night?):

If the pieces of blue-painted sheet aluminum reportedly found on and near the island were fragments of the exploded fuel tanks, then the explosion occurred on or near the island - which makes sense because the island is the only place other than the shore for the aircraft to strike something hard.
We've accepted that the explosion of the fuel tanks did not appreciably add to the trajectory of the engine, but we still have to come up with a plausible scenario that puts the engine and prop far enough away from the island for them not to be found.

Consider this:
While exploding fuel would not blow the engine off its mounts, it would blow the tanks to smithereens and, with them, the surrounding plywood fuselage structure.  For the engine and prop to depart the rest of the aircraft with considerable speed, the engine does not need to come off its mounts.  The explosion of the tanks might separate the entire nose section from the rest of the aircraft.  How far it would travel would depend upon how fast the machine was traveling when it hit the island.  In what direction it went would depend upon how the aircraft was oriented at the time of impact/explosion.
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Bill Mangus

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Re: Physics Question
« Reply #22 on: March 14, 2022, 12:02:13 PM »

have we determined which side of the island was the impact side?

(Yes, I do my best thinking just before dropping off, then have to wake up and either write it down or get back on the computer!)
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Martin X. Moleski, SJ

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Re: Physics Question
« Reply #23 on: March 14, 2022, 12:15:26 PM »

Another thought (does this stuff keep anyone else up at night?):

Not in the last 3.7 years or so. 

I just finished reading 136,000 words (322 pages) for a PhD student.

It took me 90 hours.  I counted the minutes.

That gave me some agita.

Quote
The explosion of the tanks might separate the entire nose section from the rest of the aircraft.  How far it would travel would depend upon how fast the machine was traveling when it hit the island.  In what direction it went would depend upon how the aircraft was oriented at the time of impact/explosion.

Very ingenious!

But we have, I think, gotten the most favorable calculations of how far the engine might travel if it broke away on a horizontal trajectory or if it were sent off on the optimum parabola (45 degrees).

For the biggest possible circle under ideal conditions, enter the airplane's VNE and use the 45-degree parabola in this Ballistic Trajectory Calculator.

My guess is that the biggest possible circle is not going to be insanely big. 
LTM,

           Marty
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Ric Gillespie

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Re: Physics Question
« Reply #24 on: March 14, 2022, 01:24:17 PM »

have we determined which side of the island was the impact side?

To be fair, we haven't determined anything.  All we can do is look at the available clues - which may or may not have anything to do with the plane in the pond - and make guesses. With respect to which side of the island was the impact side, we have four types of clues:
•  The location of possible evidence of impact with the island.
•  The location of artifacts found.
•  The location of artifacts seen but not recovered.
•  The location of magnetic anomalies detected in the September 2021 drone magnetometry survey.

Let's take them one at a time.
•  The location of possible evidence of impact with the island.
When Mark Smith and I were at the pond last November, Mark got excellent low-altitude aerial photos of the island with his drone.  There's no discernible disturbance to the rocks on the island itself except for the construction of a cairn (stack of rocks), hard to see in this overhead shot, someone built at some time after 1970.  The rocks in the shallow water surrounding the island seem to be fairly uniform in distribution except for one small area at the southeast edge where there appears to be a hole maybe 2 meters in diameter.  It's entirely possible the hole is natural, but rocks don't heal.  If an impact created a hole 95 years ago it would still be there.

•  The location of artifacts found.
Most of the early witnesses say only that the pieces they saw were on or near the island but Anthony McGrath told me the three-foot long piece he recovered was on the “NW center of the island.  The artifact I recovered in 1992 was just off the southern tip of the island.  The two artifacts I found in September 2021 were under the edge of the big rock at the SE edge of the island.

•  The location of artifacts seen but not recovered.
In May 1994, two TIGHAR divers saw objects on the bottom from the surface they felt sure were not rocks and might be aircraft debris, but they were unable to re-locate them for further investigation so we have only a general idea of where they were.

•  The location of magnetic anomalies detected in the September 2021 drone magnetometry survey.
The contractor identified four spots where high magnetic return is outside areas of intense geologic magnetic activity.  They may or may not be manmade ferrous objects.  (Target #4 was only of medium intensity and was well north of Target #1.)

 

 
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Ric Gillespie

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Re: Physics Question
« Reply #25 on: March 14, 2022, 04:02:53 PM »

For the biggest possible circle under ideal conditions, enter the airplane's VNE and use the 45-degree parabola in this Ballistic Trajectory Calculator.

My guess is that the biggest possible circle is not going to be insanely big.

Thanks Marty  (Lordy this is fun.)

At VNE 40 mph (17.88 m/sec), I get 2.57 seconds in flight, a max height of 8.14m (26.7 ft), and a distance of 32.5m (106.6 ft)

A VNE of 50 mph is 22.352 meters per second.  At an angle 45°, the object is in flight for 3.22 seconds, attains a maximum height of 12 meters (39 feet) and travels 50.9 meters (167 feet).

If Nungesser comes in hot enough to smack the island going sideways at 60 mph (26.8m/sec), we get 3.8 seconds of flight, a max altitude of 18.3m (60 ft), and a distance of 73.2m (240 feet).

It's time to draw some circles (tomorrow with a fresh brain). 

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Don Yee

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Re: Physics Question
« Reply #26 on: March 14, 2022, 06:08:35 PM »

Consider this:
While exploding fuel would not blow the engine off its mounts, it would blow the tanks to smithereens and, with them, the surrounding plywood fuselage structure.  For the engine and prop to depart the rest of the aircraft with considerable speed, the engine does not need to come off its mounts.  The explosion of the tanks might separate the entire nose section from the rest of the aircraft.  How far it would travel would depend upon how fast the machine was traveling when it hit the island.  In what direction it went would depend upon how the aircraft was oriented at the time of impact/explosion.

So it is possible that the engine was blown off and fell to the ground while the rest of the plane kept going? In other words, could the engine be in a spot before the rest of the wreckage?
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Don White

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Re: Physics Question
« Reply #27 on: March 14, 2022, 07:37:30 PM »

Don Y says, "So it is possible that the engine was blown off and fell to the ground while the rest of the plane kept going? In other words, could the engine be in a spot before the rest of the wreckage?"

Maybe. Our physicists can calculate its trajectory. There's the downward pull of gravity and the forward motion imparted by the airplane (plus maybe a push from an explosion).

Consider that, if the engine detached from the airframe while in air, everything was moving together until that moment, and the pieces all have the same forces acting on them and will tend to follow the same path to the same point.

However, the airplane minus engine has more air resistance, which might deflect its course or slow it down. Also its control surfaces might still be affecting its direction. So the engine is still likely to arrive at the front of the rest of the airplane, with the distance from it perhaps influenced by air resistance.

LTM,
Don W
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Martin X. Moleski, SJ

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Re: Physics Question
« Reply #28 on: March 14, 2022, 11:05:52 PM »

If Nungesser comes in hot enough to smack the island going sideways at 60 mph (26.8m/sec), we get 3.8 seconds of flight, a max altitude of 18.3m (60 ft), and a distance of 73.2m (240 feet).

It's time to draw some circles (tomorrow with a fresh brain).

This Area of a Circle Calculator reports that a circle with a 240' radius has an area of about 4 acres.

That's a lot of ground, but it would, I speculate, only be difficult, not impossible to search. 

By which I mean "only difficult for young and healthy and motivated and well-equipped people with a surprising amount of free time on their hands."  I don't mean me.   ::)
LTM,

           Marty
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Ric Gillespie

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Re: Physics Question
« Reply #29 on: March 15, 2022, 12:52:27 PM »

This is what circles with radiuses of 32m, 51m, and 73m around the center of the island look like.
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