Advanced search  
Pages: 1 ... 4 5 [6] 7 8 ... 35   Go Down

Author Topic: The flight plan, magnetic course, headwinds.  (Read 377201 times)

John Ousterhout

  • T4
  • ****
  • Posts: 487
Re: The flight plan, magnetic course, headwinds.
« Reply #75 on: January 03, 2012, 07:48:49 AM »

"...the portable radio beacon on Howland.."
There was no portable beacon.  There was a portable Radio Direction Finding (DF) unit that could receive higher frequencies than the DF unit on the Itasca.  In theory it could have been useful for guiding the aircraft towards the island.
Cheers,
JohnO
 
Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2948
LTM,

           Marty
           TIGHAR #2359A
 
Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2948
Re: Question about the Ontario
« Reply #77 on: January 03, 2012, 08:14:21 AM »

It was night and dark, no moon. Ships are dark things at night, it is amazing that a ship could be spotted at night, was the Ontario shining a spot light?

I don't know anything about the laws of the sea, except that such things exist.

Were ships required to have running lights in mid-Pacific in 1937?  Were ships equipped with such lights? 

"Nightfall to Ship in Sight" by the amazing Randy Jacobson says this:

In 1990, a resident of Australia, Syd Dowdeswell, contacted TIGHAR .  Dowdeswell had been Third Mate aboard Myrtlebank and had the 8 P.M. to midnight watch on the night in question. He recalled that the night was "clear and fine" and the lights visible on the ship were the usual running lights, engine room skylights, and cabin portholes.

Around 10 P.M. Dowdeswell was surprised to hear the sound of an aircraft coming from the starboard quarter and lasting about a minute. He reported the incident to the captain who received it "with some skepticism" because aircraft were virtually unknown in that part of the Pacific at that time and neither Dowdeswell nor the captain knew about Earhart’s flight.


The complete list of Randy's articles on the flight appears at the top of the Final Flight category.  They are well worth reading (or re-reading), as the case may be.

From the old Forum:

Date:         Thu, 9 Nov 2000 20:15:59 EST
From:         Bob Brandenburg Subject:      Re: Midpoint Coordinates
Date:         Thu, 9 Nov 2000 20:15:59 EST

From:         Bob Brandenburg

Subject:      Re: Midpoint Coordinates

>From Ric
>

> That all makes sense, but Ontario - for some reason - was heading
> specifically for 3* 05 minutes South, 165* East.

Perhaps the navigator's chart was of small enough scale that he picked off  3*
05 South after laying the rhumb track to Howland.

Or perhaps the Ontario had slightly different coordinates for Lae and Howland
than we do.

Or perhaps the Ontario CO though it best to be a few miles off the track to
enhance the likelihood of his running lights being seen by Earhart if she was
on track - - ship drivers tend to assume that aviators know where they are at
all times.

> The similarity of those
> coordinates to the entry in Betty's notebook has got to be more than
> coincidence.

No doubt about it.

Bob

LTM,

           Marty
           TIGHAR #2359A
 
Logged

Chris Johnson

  • T5
  • *****
  • Posts: 1069
  • Trying to give a fig but would settle for $100,000
Re: The flight plan, magnetic course, headwinds.
« Reply #78 on: January 03, 2012, 08:18:15 AM »

There's no reason in 1937 to run with lights off so even if there were no running lights you would have lights from port holes unless everyone was tucked up in bed.
Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2948
Re: The flight plan, magnetic course, headwinds.
« Reply #79 on: January 03, 2012, 12:34:04 PM »

Not much of a 'Monte Carlo' in what I've said, but I suspect this mess boils down to something along my beliefs by all I've been able to absorb here.

We won't know for sure until we can examine Fred's charts.

Meanwhile, I've done more work wikifying Jacobson's Monte Carlo article and colorizing the transmission timeline to highlight the constraints on speculation, such as they are, for mental or mathematical reconstructions of the flight.  By my count, there is one (1) reliable position report in the logs, at 0718 GMT:  4.33S 159.7E.  It seems to be en route from Lae to Howland, northeast of Nukumanu.  All of the other reports are qualitative and open to lots of interpretation.
LTM,

           Marty
           TIGHAR #2359A
 
Logged

JNev

  • T5
  • *****
  • Posts: 778
  • It's a GOOD thing to be in the cornfield...
Re: The flight plan, magnetic course, headwinds.
« Reply #80 on: January 03, 2012, 01:24:41 PM »

Thanks, Marty - that is helpful.  The 'vacuum pumps' as a vacuum source was nagging at me.

I checked airplane and engine data sheets - vacuum pumps were installed on 'early' Wasps.  A distinction is made on the TCDS E-143 about a difference in drive-types for early and later Wasps of NR16020's type - 'tongue and groove' drive (early) vs. 'spline' drive (later).

That's not absolute proof that NR16020 had vacuum pumps in 1937 - but I don't recall a single picture showing venturis on NR16020 in all the views I've seen.  If NR16020 had them they would have been prominent enough to be noticed, I think.  NR16020 had to have had a vacuum source for sure.

For those who are not familiar, a venturi works by exploiting the total energy present in the ambient, subsonic slipstream of an airplane in flight: the air mass accelerates as it becomes constrained by the narrow portion which results in a decrease in static pressure, hence 'vacuum' (a relative term; it is really a relative low-pressure area). 

Mr. Bernouli as explained in Wiki makes more sense of this than I can relate here. 

Venturis are great - to an extent, and there isn't any free lunch.  They impose drag and are subject to failure in ice - and do nothing for running major instruments reliably until sufficient slipstream is present (read: airspeed; propwash alone doesn't do it).  They are also limited in power compared to pumps.  Pumps are far more desirable for these reasons.
- Jeff Neville

Former Member 3074R
 
« Last Edit: October 27, 2014, 12:01:24 PM by Jeffrey Neville »
Logged

Heath Smith

  • T4
  • ****
  • Posts: 391
Re: The flight plan, magnetic course, headwinds.
« Reply #81 on: January 03, 2012, 03:10:07 PM »

Quote
It was 23 knots, not mph, the wind was 26 mph. The problem with increasing airspeed to maintain the planned ground speed is that the fuel flow increases at a faster rate than the increase in the airspeed so the specific range goes down and they run out of fuel sooner. If that is your theory then that explains why she ran out of gas shortly after her last transmission at 2013 Z. You should be pleased that Elgin Long agrees with you.

Yes, it was a typo. 23 knots per hour is 26.5 mph (too much precision? ;). Unfortunately for AE the headwinds were going to reduce their fuel efficiency no matter what speed they chose, that is just the reality. Could a more optimum speed have been chosen based on the 487 Report, sure if you study them for a while. I highly doubt Fred did this. You have to also factor in the increasing efficiency as the weight of the fuel is burned off as well as the apparently efficiency of running at 10,000ft then 8,000ft for the long haul. They already had recommendations and I highly doubt that they took it upon themselves to optimize.

As far as running out of fuel, of the reports that I have read, including the documents from the Wait Institute, they are all making significant assumptions about the speeds and altitudes that do not match any of the evidence that I am seeing. Of the worst case scenarios that I have run in my simple model, they could have traveled at least a few hundred miles after the "we are here but you are not" message so I am not with the sank and splash crowd at this point. I do have more work to do and I do not have an agenda one way or the other, I only follow the leads and do my best to make educated guesses.

If you are somewhat convinced that the Ontario was spotted as stated earlier, and you assume that they were indeed roughly 200 miles out 17:42 GMT report, I am not sure how you could suppose a new ground speed achieved other than 150mph. We can be fairly certain it was not 122 mph. It was also more than likely not the "150 knots" (172mph) as supposedly reported by AE at around 5pm Lae local time (reported by Collopy). What does make sense is that if you assume that the radio data was not that far from the truth, or perhaps the position data was calculated in anticipation of the report, then you should use that data. If we always apply the worst case scenario, then all time stamps should be assumed to be 29 minutes old, rendering the data much less useful. While it would have been ideal for AE to state the time for her report, or to give more position reports (she only gave 2 from what I am reading), she didn't, that is life. All that is left is to the make the most of what she did report and make educated guesses as to what the reality was. My guess is that the reported positions and the time stamps can be reasonably assumed to be accurate.

If you instead assume 150mph ground speed achieved outside of Lae they would have passed Nukumanu Island almost 1.5 before reporting the position. I think this in itself is enough evidence to say that their ground speed was something less than 150mph. If we say Ok, but then they left Nukumanu Island, they might have gone 150mph, they should have spotted the Ontario at 9:58 GMT. They did not report this at 9:58 GMT or 10:15 GMT but instead 10:30 GMT, which was not a regularly scheduled broadcast time. If you say Ok, it must have been the Myrtle Bank, they would have spotted the ship 60 miles away (using TIGARs estimate of the Myrtle Bank's position) that was 27 miles roughly off the flight path (3 times the distance of the Ontario to the flight path). If we say that is Ok, it's possible, then we say that the "200 miles out" message was approximately accurate, then the ground speed achieved from spotting the Myrtle Bank to "200 miles out" implies a 138mph ground speed. As you can see, this becomes more and more of a stretch, changing speeds at least 3 times for the numbers to work out. I am already stretching enough to fall off the chair so I think we can stop there. If instead we use the 124.5 all the way from Lae to the Ontario, then 150mph from Ontario to "200 miles out" the timing works out simply enough. It might even make sense that Fred might have detected the more favorable head winds and adjusted the speed accordingly for the remainder of the trip. It would be a good time to change speeds since you had just left the mid-point of the trip, at the end of a 176 mile segment in the flight plan and you could start fresh with the original flight plan suggestions. He might also have noticed the worsening conditions and did not want more to add to his plate. Sounds reasonable to me.

Since Fred did have some time to report celestial navigation after departing Nukumanu Island that might explain why they did such a good job sticking to the flight path and spotting the Ontario. Unfortunately, after seeing the Ontario, the stars might have been obscured by overcast conditions whether or not you require them or not. Personally, I think if Noonan could have done his job, not fighting with the sky conditions, they would have landed on Howland and we would not be having this conversation. Amelia would have arrived home safely and started an acting career or at least banked a few dollars in the advertising business. The fact that they did not make it is compelling evidence that something kept him from being able to do his job. Everything I have read about him indicates that he was the best in the business. Being hamstrung but the sky conditions was not something he planned for, that is what happens when you take risks, often you pay for it with your life. No guts no glory as they say.
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: The flight plan, magnetic course, headwinds.
« Reply #82 on: January 04, 2012, 02:55:27 AM »

If the Myrtle Bank was lighted as described by her Third Mate and sky conditions like-wise as he reported, AE should not have had a problem spotting a ship on a dark sea.  Ontario is less clear, but if the intention of her stationing was to be used as a nav-aid then it is probably reasonable that she too was lighted well enough for sighting.

Whether AE spotted Myrtle Bank, Ontario, or another ship remains completely unclear to me and may never be answered.


LTM -
I certainly didn't mean that they were running without their navigation lights illuminated which would have been a violation of maritime regulations, but the running lights are not very bright. For the largest ships today the lights are only required to be visible from three nautical miles except for one masthead white light that must be visible from six nautical miles but that light only covers a sector over the bow from two points abaft the beam on each side. This means 22 1/2 degrees behind straight out to the side for the nautically challenged. The red left side running light shines from straight ahead to 2 points the port beam and the green light shines through the same sized arc to starboard. These are also the requirements for airplane position lights. These segments relate to the right of way rules. If you see only a white light then you know your are overtaking and you must stay clear. If you see the red light then you know the other ship is to your right and he has the right of way, you must stay clear. If you see the green light then you have the right of way. This is where they got the standard colors for traffic signals. The masthead light is not visible from behind the ship. These sectors have been required for over a century but the intensity requirement used to be lower. Earhart would have been overtaking Myrtlebank or Ontario from astern so would only have been able to see one white stern light visible only three NM or less.

Marine running lights incorporate fresnel lenses that concentrate the available light from the light sources horizontally (after all, that's where the other ships are, they don't expect to have a collision with a plane) so would be much dimmer or possibly invisible as seen from a plane. Earhart was flying at 8,000 feet, one and a third NM straight up so if we use good old Pythagoras we find that a three NM slant range extends horizontally only 2.7 NM so the plane would have had to been within a radius of only 2.7 NM to be able to see a three NM visibility light, and this assumes that the full intensity was available at a high angle up in the sky, and we know that it wasn't. Using these values and a little trig we see that at the point where the light could first become visible, within 2.7 NM of the ship, the angle from the ship's lights up to the plane would have been 26°, well outside the band of light coming through the fresnel lenses of the running lights so they would be invisible from 8,000 feet even if the plane passed within the 2.7 NM radius of the ship. Based on this I think we can eliminate the possibility that Earhart saw the running lights of either ship.

What about other lights on the ship? There are very few and those that are on deck are dim  so as not to interfere with the night vision of the crew, for instance the bridge is virtually blacked out.  What about the lights in the cabins shinning out through the portholes? Most cabin light are mounted on the ceiling just like your lights at home. To someone walking around on the deck of the ship these may appear bright enough but due to the height of the ceiling light and the portholes, which are lower, the light from the cabins can only shine downward, not up toward the sky. They may be visible from the ship or from nearby ships but unlikely to be seen from a plane. In addition, it was about 9:30 at night and many would have gone to bed already, turning off their cabin lights first. We know Itacsa was supposed to shine a searchlight up into the sky if the plane was going to arrive at night but there is no reason to think that Ontario was shinning a light since they didn't send out the per-planned radio becon signals because Ontario had never been advised that Earhart had departed from Lae. And, of course, the Myrtlebanks was not tasked to shine a searchlight that night.

In 2009 I crossed the Atlantic by ship on the Royal Clipper, a 437 foot five masted sailing ship, departing from Lisbon, touching at Casablanca and Teneriffe, then ten days at sea before arriving in Barbados.  I am a night owl and I spent a lot of time on deck at night doing celestial navigation and I remember how dim the few lights were. I have no reason to believe that the Myrtlebank or the Ontario would have had brighter lights on deck, and most cabin lights went out fairly early.

The first time I went to Europe, I took off from Newfoundland in the middle of the night, taking the route to the Azores which is the popular route when weather makes the shorter, northern route, iffy. About an hour after takeoff I started seeing lights ahead of me and I immediately thought, OMG, OMG OMG, I must be way off course, I'm heading towards a large city, I must have gotten turned around somehow. I checked my DG, still 145° and the compass too. The ADF needle was still five degrees right of the tail (I had a crosswind from the right) and this heading had kept me on the 139° radial of the Torbay VOR until I had lost its signal. This was like something out of the Twilight Zone, it didn't make any sense. As I got closer I could see the city spreading out almost horizon to horizon, WHAT IS GOING ON? When I got very close I recognized that I was looking at the the Grand Banks fishing fleet. These boats work all night with extremely powerful white lights for working with the nets. They are exactly like stadium lights or like the lights used for mining guano on Nauru at night in 1937! I've never seen a ship at night while flying over the ocean except fishing boats with the stadium lights.

I am coming to the conclusion that Earhart did NOT see either ship that night. The reports of her radio transmission at about 1030 Z say that she said either "ship in sight" or "lights in sight." It makes much more sense that she was reporting seeing the Nauru lights and they would have been close enough to have been seen from her altitude at that time.

gl
« Last Edit: January 04, 2012, 03:25:24 AM by Gary LaPook »
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: The flight plan, magnetic course, headwinds.
« Reply #83 on: January 04, 2012, 02:59:13 AM »

Quote
It was 23 knots, not mph, the wind was 26 mph. The problem with increasing airspeed to maintain the planned ground speed is that the fuel flow increases at a faster rate than the increase in the airspeed so the specific range goes down and they run out of fuel sooner. If that is your theory then that explains why she ran out of gas shortly after her last transmission at 2013 Z. You should be pleased that Elgin Long agrees with you.

Yes, it was a typo. 23 knots per hour
It's not knots per hour, it is simply knots since a knot is one nautical mile per hour. "Knots per hour" would actually be one nautical mile per hour per hour, a measure of the rate of acceleration.

gl
« Last Edit: January 04, 2012, 03:08:26 AM by Gary LaPook »
Logged

Heath Smith

  • T4
  • ****
  • Posts: 391
Re: The flight plan, magnetic course, headwinds.
« Reply #84 on: January 04, 2012, 04:16:39 AM »


Quote
I am coming to the conclusion that Earhart did NOT see either ship that night. The reports of her radio transmission at about 1030 Z say that she said either "ship in sight" or "lights in sight." It makes much more sense that she was reporting seeing the Nauru lights and they would have been close enough to have been seen from her altitude at that time.

If a human eye can detect a single candle flame at anywhere from 15 to 30 miles, I suspect that a single bulb on either ship could have been easily spotted at 10 miles out at 8,000ft. Looking out the window of a passenger jet at 5 miles up, you can easily spot a single street lamp from many miles away. It would seem common sense that if the Ontario knew that AE was flying over that evening that they would provide some illumination. To suggest they went lights out with only fresnel running lights seems to be another worst case scenario.

As far as spotting Nauru goes, it would have been 200 miles away assuming the < 150 mph ground speed after leaving Nukumanu Island at 10:30 GMT. Assuming ideal conditions, they would have been able to see roughly 120 miles out to the horizon. At the closest point, irrespective of all evidence of ground speed achieved, Nauru would have been 150 miles off the flight path. Assuming you had a light on a 100ft tower at Nauru, it still would have not been visible at an altitude of 8,000ft assuming they were on the flight line. For AE to FN to have spotted the lights of Nauru, they would have had to drift over 30 miles North of the flight path for this to be a possibility.

The simplest explanation for "lights ahead" or "ship ahead" would be that they spotted the Ontario. The position is well known and only 10 miles off the flight path. AE would have been keenly aware of the presence of the Ontario and would have used common sense to look for it along the way. They could have easily drifted North a few miles and nearly flown right over the top of the Ontario and this would not be that unreasonable.

Quote
It's not knots per hour, it is simply knots since a knot is one nautical mile per hour. "Knots per hour" would actually be one nautical mile per hour per hour, a measure of the rate of acceleration.


Yes, stupid mistake, thanks.
Logged

JNev

  • T5
  • *****
  • Posts: 778
  • It's a GOOD thing to be in the cornfield...
Re: The flight plan, magnetic course, headwinds.
« Reply #85 on: January 04, 2012, 04:52:10 AM »

If the Myrtle Bank was lighted as described by her Third Mate and sky conditions like-wise as he reported, AE should not have had a problem spotting a ship on a dark sea.  Ontario is less clear, but if the intention of her stationing was to be used as a nav-aid then it is probably reasonable that she too was lighted well enough for sighting.

Whether AE spotted Myrtle Bank, Ontario, or another ship remains completely unclear to me and may never be answered.


LTM -
I certainly didn't mean that they were running without their navigation lights illuminated which would have been a violation of maritime regulations, but the running lights are not very bright... Based on this I think we can eliminate the possibility that Earhart saw the running lights of either ship.

What about other lights on the ship? There are very few and those that are on deck are dim  so as not to interfere with the night vision of the crew, for instance the bridge is virtually blacked out.  What about the lights in the cabins shinning out through the portholes? Most cabin light are mounted on the ceiling just like your lights at home. To someone walking around on the deck of the ship these may appear bright enough but due to the height of the ceiling light and the portholes, which are lower, the light from the cabins can only shine downward, not up toward the sky. They may be visible from the ship or from nearby ships but unlikely to be seen from a plane. In addition, it was about 9:30 at night and many would have gone to bed already, turning off their cabin lights first...

The first time I went to Europe, I took off from Newfoundland in the middle of the night, taking the route to the Azores which is the popular route when weather makes the shorter, northern route, iffy. About an hour after takeoff I started seeing lights ahead of me and I immediately thought, OMG, OMG OMG, I must be way off course, I'm heading towards a large city, I must have gotten turned around somehow. I checked my DG, still 145° and the compass too. The ADF needle was still five degrees right of the tail (I had a crosswind from the right) and this heading had kept me on the 139° radial of the Torbay VOR until I had lost its signal. This was like something out of the Twilight Zone, it didn't make any sense. As I got closer I could see the city spreading out almost horizon to horizon, WHAT IS GOING ON? When I got very close I recognized that I was looking at the the Grand Banks fishing fleet. These boats work all night with extremely powerful white lights for working with the nets. They are exactly like stadium lights or like the lights used for mining guano on Nauru at night in 1937! I've never seen a ship at night while flying over the ocean except fishing boats with the stadium lights.

I am coming to the conclusion that Earhart did NOT see either ship that night. The reports of her radio transmission at about 1030 Z say that she said either "ship in sight" or "lights in sight." It makes much more sense that she was reporting seeing the Nauru lights and they would have been close enough to have been seen from her altitude at that time.

gl

See Mr. Dowdeswell's comments again -

"Dowdeswell had been Third Mate aboard Myrtlebank and had the 8 P.M. to midnight watch on the night in question. He recalled that the night was "clear and fine" and the lights visible on the ship were the usual running lights, engine room skylights, and cabin portholes."

That should make for a spottable ship.  The engine room skylights may be quite significant themselves (natural light by day, aglow with engine room light at night).  At the very least, AE reported spotting something that may well have been a ship.  Myrtle Bank is a possibility. 

The 'guano lights' are interesting - would like to know more about that.

Personally I have observed many boats and ships in daylight and at night - while at sea, in the air, and from shore.  They are often enough lighted somewhat as Dowdeswell described and easy enough to spot at great distances.  Typically other lights aboard are far more visible than the required nav lights, oddly enough I suppose.

LTM -
- Jeff Neville

Former Member 3074R
 
« Last Edit: January 04, 2012, 04:53:55 AM by Jeff Neville »
Logged

Dale O. Beethe

  • T3
  • ***
  • Posts: 118
Re: The flight plan, magnetic course, headwinds.
« Reply #86 on: January 04, 2012, 07:11:18 AM »

ANY lights on a ship at night show up extremely well, which is why light discipline was crucial during wartime.  Even a lit cigarette could be seen for miles.
Logged

Monty Fowler

  • T5
  • *****
  • Posts: 1078
  • "The real answer is always the right answer."
Re: The flight plan, magnetic course, headwinds.
« Reply #87 on: January 04, 2012, 01:39:30 PM »

While Gary's theory of the guano mining lights is intriguing, I can't buy it for one simple fact - Fred would have figured out what they were in the same way that Gary figured out that he was looking at a fishing fleet, would he not? Because Fred was a pretty competent navigator. So it would not have been, "Ship in sight ahead."

Even the few "normal" lights on a ship, at night, on the total blackness of the sea, can show up quite well from an aircraft flying at her altitude. And the Ontario would not have been "blacked out," it wasn't wartime yet.

Monty Fowler,
TIGHAR No. 2189 CER
Ex-TIGHAR member No. 2189 E C R SP, 1998-2016
 
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: The flight plan, magnetic course, headwinds.
« Reply #88 on: January 04, 2012, 11:06:39 PM »



If a human eye can detect a single candle flame at anywhere from 15 to 30 miles,

That is apocryphal and easily shown to be incorrect. If you were correct then you should complain to your congressman about all the money the Coast Guard has wasted putting those big powerful lamps in lighthouses when they could have saved billions of dollars by just using a birthday cake candle (O.K. two birthday cake candles for redundancy.) As I posted before, running lights on the largest ships are visible at three nautical miles. To make sure that the running lights comply with that requirement the government wrote specific regulations that specify the required lamp intensity for running lights. To achieve 3 NM visibility requires a lamp intensity of 12 candellas (11.77 candles, let's call it 12 candles too.) The regulations also require a 0.9 candella (candle) lamp to achieve visibility at 1 NM. So, either you are right, that one candle can be seen at 30 miles or the government is right that one candle is only visible at about one nautical mile, my money is on the government's engineers on this one. If you want to be exact, 0.9 candella is 0.88 candles. Since the intensity of the light is attenuated at the square of the distance, it takes a lamp four times brighter to be visible at only twice the distance, one candle would be visible at 1.06 NM. Since the power required increases at the square of the distance, to  be visible at 30 NM it would take 30^2 x 0.88 candles which is 792 candles so you are only short by 791 candles. If you want to do the rest of the math you will find out that this produces a light intensity at the eye of 0.000000024 foot-candles which your research will show is the minimum amount of light your eye can detect. Here is the actual regulation:
------------------------------------------------------------
Title 33: Navigation and Navigable Waters
PART 84—ANNEX I: POSITIONING AND TECHNICAL DETAILS OF LIGHTS AND SHAPES

§ 84.15   Intensity of lights.

(a) The minimum luminous intensity of lights shall be calculated by using the formula:

I=3.43×106 ×T×D2 ×K−D

where I is luminous intensity in candelas under service conditions,

T is threshold factor 2×10−7lux,

D is range of visibility (luminous range) of the light in nautical miles,

K is atmospheric transmissivity. For prescribed lights the value of K shall be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.

(b) A selection of figures derived from the formula is given in Table 84.15(b):

Table 84.15(b)
Range of visibility (luminous range) of light in nautical miles D   Minimum luminous intensity of light in candelas for K=0.8 I
1   0.9
2   4.3
3   12
4   27
5   52
6   94
--------------------------------------------------
I also pointed out before that the running lights are designed to shine the light out towards the horizon an ithey do this by using fresnel lenses that refracts the light that would be emitted at a high angle and bends it to go out towards the horizon so no light would shine up into the sky for Amelia to see. These steamships lights are designed to send the light out in a narrow 10° band in the range of 5° below the horizon to 5° above horizon. Lights for sailing ships cover a larger vertical range because sailing ships heal over so the greater vertical range in needed to make sure that the light is always visible from the horizon. Neither the Ontario nor the Myrtlebank were sailing ship. The government also has a specific regulation governing the vertical range of the running lights and here it is:

--------------------------------------------

§ 84.19   Vertical sectors.

(a) The vertical sectors of electric lights as fitted, with the exception of lights on sailing vessels underway and on unmanned barges, shall ensure that:

(1) At least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the horizontal;

(2) At least 60 percent of the required minimum intensity is maintained from 7.5 degrees above to 7.5 degrees below the horizontal.

(b) In the case of sailing vessels underway the vertical sectors of electric lights as fitted shall ensure that:

(1) At least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the horizontal;

(2) At least 50 percent of the required minimum intensity is maintained from 25 degrees above to 25 degrees below the horizontal.

(c) In the case of unmanned barges the minimum required intensity of electric lights as fitted shall be maintained on the horizontal.

(d) In the case of lights other than electric lights these specifications shall be met as closely as possible

-------------------------------------

Obviously these are the current versions of these regulations but they have not changed in any large way since the '30s.
gl
« Last Edit: January 04, 2012, 11:45:49 PM by Gary LaPook »
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: The flight plan, magnetic course, headwinds.
« Reply #89 on: January 04, 2012, 11:21:59 PM »


 It would seem common sense that if the Ontario knew that AE was flying over that evening that they would provide some illumination.
But Ontario did NOT know that AE was flying over that evening, they never received any message, so they did not send out radio homing signals and they had no reason to show additional lights either.

gl
Logged
Pages: 1 ... 4 5 [6] 7 8 ... 35   Go Up
 

Copyright 2019 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