Earlier in this thread Chris Johnson asked: given that, at 1030Z, AE probably saw the Myrtlebank, what if she misidentified it as the ship she expected to be there, the Ontario? Well, I wonder if that could give them a really nasty problem. The mistake would introduce a pernicious error into FN's navigation, and I hope someone with a better grasp of geography, time, and navigation will be able to correct the back-of-an-envelope calculations that follow. (I'm also aware that this account short-cuts a lot of possibilities like possible lights on Nauru and possible stellar fixes in the middle of the night).
So, they've been flying for hours into the Pacific night, with no landmarks since 0718Z at best; they're looking out for the lights of their waypoint, the Ontario; and they reach it, as they think, at 1030Z, which is on the late side but still not wrong enough to sound alarm bells. Thank heavens. They've got halfway, something important enough to merit her breaking her radio schedule to transmit the message "Ship in sight", that was picked up in Nauru. They now have, as they think, the thing they most want: an unambiguous fix on their position, since they know in advance the intended position of the Ontario. They can restart dead reckoning from a "last known good" position. Regrettably, if it's actually the Myrtlebank, the position is wrong, by about 112nm basically westwards.
They fly on for 5 ½ more hours, through the possibly overcast night, getting no help from celestial navigation as they go. At dawn (about 1800Z), Fred does the sunrise shot, and calculates the distance to the advanced LOP. All well and good. But his estimate of their current ground speed will be significantly too fast, by approximately 112 nm over 5 ½ hours, or 20 knots. As a result, they'll turn off onto the advanced LOP about an hour later and (say) 20 nm too early. They'll be short of their destination.
A couple of other points about this possible mistake:
• Wouldn't AE have been worried by the lack of radio contact with the ship in the night? No. She already knew the originally agreed radio protocol was made useless by the fact that the ship had no HF reception equipment. She had sent a telegram trying to change that protocol, but she knew it probably hadn't reached the ship yet. She wasn't expecting radio contact.
• Could she have mistaken the 400-foot Myrtlebank for the 150-foot Ontario? That begs further questions: how good was her ship identification at night? How much did she even know about what the Ontario was supposed to look like? Bear in mind she presumably didn't know that the Myrtlebank was in the area.
• How had they missed the Ontario earlier? Well, the Ontario's log mentions cloud cover from 20 to 40%; what's more, it wasn't precisely at the latitude she seems to have been expecting. All too easy to miss.
• What happens after they come up short? They end up flying the LOP south, and if they're starting short - from west of Howland - that brings them, as it happens, very nicely to Gardner.
• Finally, this makes sense of the conjecture that some of the numbers in Betty's notes represent the Ontario's intended position. If Fred is out of action, and AE can't take or doesn't trust her own measurements of where they are, the Ontario is still AE's "last known good" navigational position. Not so good, in reality.
Any thoughts?
Your post brings up a number of points to discuss. You correctly point out that IF they mistook the Myrtlebank for the Ontario, and IF they started a new dead reckoning from the coordinates they had been given for the Ontario, and IF they used this position as the starting point for calculating their ground speed with the sunrise line of position as the ending point for the ground speed calculation, and IF they got no celestial observations between those points, and IF they got no additional sun observations after the sunrise observation then they would have advanced the sunrise LOP an incorrect distance so that when they intercepted that advanced LOP and followed it they would not have flown over Howland. I have attached a file with several illustrations to help you follow along.
The first illustration shows the locations of interest, the position reported at 0718 Z and the positions of the Ontario and Myrtlebank. Illustration 2 shows the position reported at 0718 Z a few nautical miles west of the western end of Nukumanu. The radioed coordinates recorded by Chater are 4° 33' south, 159° 07' east. Noonan determined this position by visually observing the island because it was not possible to have determined it by celestial navigation due to being in daylight with only the sun available and the sun had not been positioned at azimuths that allowed for a running fix. Our modern chart shows these coordinates as being slightly west of the island but it is also possible that the chart Noonan was using depicted the island further west that it actually is. Some have mistakenly claimed that this position was too far west of Nukumanu to have allowed them to see the island but this mistake is due to referring to the published position of Nukumanu, 4° 35' S, 159° 30' E, which is 23 NM east of the Electra's reported position. However, the published coordinates are for the far south-east corner of Nukumanu and the island is 11 NM long, east to west so the Electra was, at most, 12 NM west of the western end of the island, and possibly less if the chart had it improperly placed.
Illustration 3 shows the course to the position of the Ontario at 1030 Z at 2° 59' S, 165̊ 23' E, a distance of 387 NM. Illustration 4 shows the course to the position of the Myrtlebank at 1030 Z at 2° 20' S, 167° 20'E, a distance of 501 NM. Jacobson provides incorrect distances of 350 NM and 462 NM respectively
in his paper. He does this because he incorrectly interpreted the coordinates from Chater for the 0718 Z position report as though they were decimal degrees, 4.33° S, 159.7° E (
claiming that the latitude was "four and a third degrees south," something no navigator would ever say) which is the same as 4° 20' S, 159° 42' E, about 38 NM closer to the ships. This is shown in illustrations 5 and 6. How do we know that
Chater's notation of “POSITION 4.33 SOUTH 159.7 EAST". used the "." to separate degrees and minutes and not decimals of a degree? That is easily determined because the Chater Report contains its own "Rosetta Stone" to decipher his notation with. His report also contains the text of the radiogram received from Nauru giving the coordinates of the light on that island. Chater writes it as "THE FOLLOWING FROM NARAU STOP NEW NARAU FIXED LIGHT LAT 0.32 S LONG 16 .55 EAST." We know the location of Nauru is 0°32'S., 166°55'E, see attached page from
Sailing Directions Pacific Islands. It is clear that Chater's ".32" is minutes of latitude and the ".55" is minutes of longitude. They are not decimals of degrees. Balfour used the same notation, using "." to separate degrees from minutes, see attached radiogram from Nauru.
We don't know the exact time that Noonan determined the position reported at 0718 Z but it seems unlikely that they just happened to arrive at the island at the exact time that Earhart was scheduled to call Lae on the radio at eighteen minutes after each hour. This is an unknown for us but not for Noonan. In his computations, Jacobson makes the assumption that they were there at 0700 Z, which is reasonable, and I will use the same time so they we can compare my calculations directly with his.
From 0700 Z to 1030 Z is three and a half hours so if the plane spotted the Ontario after flying 387 NM then the ground speed was 111 knots, Jacobson computed just 100 knots for his 350 NM distance. This is very close to the ground speed from Lae to Nukumanu, 105 knots for that 737 NM leg. If they were actually looking at the Myrtlebank then their ground speed would have to have been 143 knots (Jacobson, 132 knots) well above the already experienced ground speed and necessitating a tailwind since their normal cruising airspeed was 130 knots (150 mph), a highly unlikely situation since all the forecasts and weather reports showed consistent headwinds in the 20 to 25 knot range. Based on the highly unlikely high ground speed, we can eliminate the Myrtlebank. Also, the only reason to even consider the Myrtlebank is the report of hearing a plane pass over the ship made by the third mate in
1990, 53 years later. No one else reported it and there was no contemporaneous writing so all we have is an unsupported anecdote and a "long in the tooth" one at that.
Noonan, however, didn't know the location of Ontario or of Myrtlebank at 1030 Z, all he had were the coordinates for the station that the Ontario was supposed to maintain, 3° 05' S, 165° 00 E as shown in illustration 7. The distance from the 0718 Z position and the assigned station for Ontario is 364 NM so the ground speed determined by Noonan was 104 knots, 7 knots slower than the actual ground speed to the actual position of Ontario since the Ontario was actually 23 NM farther east than the coordinates that Noonan had. Ontario did not maintain its exact station, as the attached log of its positions for July 1 and 2 shows. During this period, when Ontario could expect Earhart to arrive, the ship moved through an area 17 NM from north to south and 41 NM from east to west as depicted as a box in illustrations 8 and 9. Illustration 10 shows that Ontario was at the northeast corner of this box when the Electra flew over. Ontario could not anchor in that deep water and had to maintain steerage way and had no pressing need to maintain an exact position since Ontario believed that they could send their correct position by radio to the Electra when the time came, they did not know that Earhart could not use the international calling frequency of 500 kcs. There used to be ocean station vessels positioned in the Atlantic and Pacific to take weather observations and to provide radio beacons for aircraft. These vessels also did not maintain exact positions but radioed their actual positions to aircraft passing over so that the aircraft navigators had the correct information for their computations. Because Noonan could not be certain of the position of the Ontario, it is unlikely that he would have used it as fix to restart his dead reckoning. It would make more sense for him to take a celestial fix in that area (Ontario reported good conditions for celestial sights) so he could be certain of his position and would know of the size of its uncertainty.
Illustration 11 shows the relationship of these ships and the points of no return based on several assumptions as previously
discussed on the Point of no return thread. Illustration 12 shows the rest of the flight to Howland and shows the position of a sunrise LOP at approximately 1749 Z which is about 180 NM short of Howland. The distance from the given position of Ontario to the LOP is 1128 NM covered in the 7:19 period making Noonan's computed ground speed 130 knots. But, from the actual position of Ontario, the distance is actually only 1104 NM so the actual ground speed is 126 knots. Using the 130 knot speed that Noonan would have had, he would compute that it would take 1:23 to fly the 180 NM to reach the advanced LOP through Howland so the plane would have turned onto the LOP at 1926 Z. But, flying 1:23 at the actual ground speed of 126 knots would make the plane travel only 174 NM so would turn 6 NM too soon and fly on an LOP 6 NM west of Howland. Looking at the scenario that you were interested in, that they actually saw the Myrtlebank, then the same computation shows that the plane's actual ground speed was 111 knots for the 811 NM from Myrtlebank to the LOP. They then would fly 1:23 at the actual ground speed of 111 knots, covering only 154 NM and so turn short by 46 NM onto a line parallel to the correct advanced LOP but 46 NM to the west.
gl