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Author Topic: Ontario vs Myrtlebank  (Read 923 times)

Christian Stock

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Ontario vs Myrtlebank
« on: April 29, 2020, 10:52:40 AM »

What is the prevailing thought on the identity of the ship sighted at 1030Z. Was it the USS Ontario or MV Myrtlebank? Would a smaller vessel like Ontario even be visible?
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Ric Gillespie

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Re: Ontario vs Myrtlebank
« Reply #1 on: April 29, 2020, 12:02:09 PM »

What is the prevailing thought on the identity of the ship sighted at 1030Z. Was it the USS Ontario or MV Myrtlebank? Would a smaller vessel like Ontario even be visible?

There's no way to know for sure but Ontario reported no contact with Earhart but a crew member on Myrtlebank named Dowdeswell said he heard a plane.

Nauru heard Earhart say "Ship in sight ahead" at 20:30 Sydney,
Australia time which which was 1030Z. Sydney was Greenwich minus
10. Nauru should be Greenwich minus 11, in which case Earhart was
heard there at 21:30.
Dowdeswell remembers that he heard the plane at about 22:00.

If we assume that Myrtlebank was on Nauru time (which they should
have been), then Nauru heard Earhart say she saw a ship in sight
ahead roughly half an hour before Dowdeswell heard the plane pass off
the ship's starboard quarter. If we take the times as approximations,
it all fits.
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Christian Stock

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Re: Ontario vs Myrtlebank
« Reply #2 on: April 29, 2020, 01:58:05 PM »

Myrtlebank seems to be the ship, except it's hard to believe they had a slight tailwind. 100 kts seems a little slow. 132 kts seems a little fast. Of course, we are think of the flight in terms of legs, and she might have had a huge tailwind for just a little while, encompassing parts of 2 legs.


I had an IP tell me once that I couldn't just plan every mission for 100 knots, then made me recalculate everything for KPH while we sat in a field.
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Ric Gillespie

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Re: Ontario vs Myrtlebank
« Reply #3 on: April 29, 2020, 02:49:04 PM »

Myrtlebank's position at 1030Z was 2° 20' S, 167° 10' E.   1,223 nm from Lae in 10.5 hours gives you an average groundspeed of 116.47 kts. 
Economical cruise was flight-planned at 130 kts once the aircraft reached a cruising altitude of 8,000'. The climb was expected to take about one hour. Airspeed during the climb was probably around 100 kts or a little less.  So, figuring one hour at 100 kts and 9.5 hours at 130 kts gives an average of 109.10 kts since departure in still air.  If her average groundspeed was 116.47 kts, she had a net tailwind of a little over 7 kts - maybe a little more if the climb was slower or longer - for roughly the first half of the flight.

(Unless I've screwed up the arithmetic, which would be normal for me.)
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Ric Gillespie

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Re: Ontario vs Myrtlebank
« Reply #4 on: April 30, 2020, 07:44:25 AM »

(Unless I've screwed up the arithmetic, which would be normal for me.)

True to form, I got the time zone wrong. Our Australian friend David Billings was kind enough to point out to me that Sydney is on the east side of the dateline so local time is GMT plus 10, not minus 10.  22:30 Sydney time is therefore 08:30 GMT.
It doesn't change the average speed estimate but it's good to have that straight.
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Christian Stock

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Re: Ontario vs Myrtlebank
« Reply #5 on: April 30, 2020, 11:50:43 AM »

I should have specified the 100 vs 132 kts is for the 0700-1030 leg, as shown on . Skyvector is giving me ~450 nm for that, so 129 kts (a slight headwind).

I've read here that it is either assumed or known that she did not take off until 0022Z. I'm hoping she did not immediately turn to 075° and try to fly over the mountains. My guess is that she flew 20nm to Lae proper and then picked up her heading there. That gives us 792nm to 0700 position report, and another 450nm to MV Myrtlebank.

Either way, she is dead nuts on course and roughly on time, until they hit sunset and overcast. It's DR until sunrise, which happens at about the right time for them. If they are too fast (past Howland), or too slow (>200nm short), they should have known based upon the time of the sunrise. So whatever happened weather-wise between sunset and sunrise did not affect their groundspeed very much, but pushed them way South or way North. If North, they are probably ditching and sinking, and if South, they find Gardner.
« Last Edit: April 30, 2020, 11:53:12 AM by Christian Stock »
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Ric Gillespie

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Re: Ontario vs Myrtlebank
« Reply #6 on: April 30, 2020, 01:43:44 PM »

I've read here that it is either assumed or known that she did not take off until 0022Z.
The only primary sources I'm aware of - Chater and Collopy - both say the plane took off at 10:00 a.m. local time (00:00Z). 

I'm hoping she did not immediately turn to 075° and try to fly over the mountains.

I don't think there's any question about that.  Collopy wrote:
"The take-off was hair-raising as after taking every yard of the 1000 yard runway from the north west end of the aerodrome towards the sea, the aircraft had not left the ground 50 yards from the end of the runway.

When it did leave it sank away but was by this time over the sea. It continued to sink to about five or six feet above the water and had not climbed to more than 100 feet before it disappeared from sight."

The takeoff was more hair-raising than it needed to be.  Earhart neglected to run the flaps down 30° as recommended by Lockheed.  As a consequence, her takeoff run was longer than would have been necessary and when she hauled it off the airplane would fly only in "ground effect."  She staggered along, straight ahead, until she burned off enough fuel to begin climbing.  Any turning was out of the question.

Either way, she is dead nuts on course and roughly on time, until they hit sunset and overcast. It's DR until sunrise, which happens at about the right time for them. If they are too fast (past Howland), or too slow (>200nm short), they should have known based upon the time of the sunrise.

Noonan's LOP after sunrise told him he was not past Howland.

So whatever happened weather-wise between sunset and sunrise did not affect their groundspeed very much, but pushed them way South or way North. If North, they are probably ditching and sinking, and if South, they find Gardner.

The post-loss radio signals leave no doubt about that.
« Last Edit: April 30, 2020, 01:51:55 PM by Ric Gillespie »
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Christian Stock

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Re: Ontario vs Myrtlebank
« Reply #7 on: April 30, 2020, 06:24:19 PM »

Ouch. Yeah, I didn't see much in the way of flaps in the Lae takeoff film.

Shouldn't sunrise have been about 11 minutes later since they were ~200nm West and at altitude? That should have been 13 minutes for the distance and -2 minutes for the altitude. They were calling 200nm out, presumably at sunrise, but they call it at 0612 Itasca time, which is 0712 Howland time, and 3 minutes before sunrise at Howland. For this to work they would have had an 18 kt tailwind overnight, averaging 148 kts from MV Myrtlebank to sunrise.

For grins I plotted the LOP and it passed about 35 nm EAST of Howland, then advanced it 200nm further East. The advanced 157/337 LOP passes about 7 miles East of Phoenix Island. I will just say that Enderbury Island and Phoenix Island are extremely similar in appearance to Howland and Baker. It's a little scary.

Tell me if I am off base or rehashing some old discussion.
« Last Edit: May 03, 2020, 07:50:01 PM by Christian Stock »
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Ric Gillespie

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Re: Ontario vs Myrtlebank
« Reply #8 on: May 01, 2020, 07:56:53 AM »

They were calling 200nm out, presumably at sunrise, but they call it at 0612 Itasca time, which is 0712 Howland time, and 3 minutes before sunrise at Howland.

Itasca logged "about two hundred miles out // appx" at 06:15 Itasca Time.  For Earhart the time was 17:45Z.  Earhart makes transmissions at quarter to and quarter past the hour, so her transmission at 17:45Z is right on schedule but it's not at all clear how old the "two hundred miles out" estimate from Noonan is or what it's based on.  It does seem to be too early to be based upon sunrise so it's probably just a DR estimate.  Her 06:46 Itasca Time (18:16Z) estimate "about 100 miles out" is more likely to be based on a sun shot.  People get all excited about her covering 100 miles in half an hour (200 knots) but assuming precision that doesn't exist.  Noonan could have the "two hundred miles out" estimate as early as, say, 17:20Z and he could have been way off.  The "about 100 miles out" estimate at 18:16Z, if based on a sun shot, should have allowed him to plot a reliable LOP of 157/337 on his chart.  He wouldn't know if his position on the line was north or south of his desired course to Howland but he'd know for sure that he was about 100 miles west of the line if it was advanced to fall through Howland.

Tell me if I am off base or rehashing some old discussion.
Not at all.  Rehashing old discussions is the way we check our work and catch old errors.
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Christian Stock

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Re: Ontario vs Myrtlebank
« Reply #9 on: May 01, 2020, 09:05:23 AM »

Ok, that makes more sense, and resolves the 100 mile out remark.

They were calling 200nm out, presumably at sunrise, but they call it at 0612 Itasca time, which is 0712 Howland time, and 3 minutes before sunrise at Howland.

Itasca logged "about two hundred miles out // appx" at 06:15 Itasca Time.  For Earhart the time was 17:45Z.  Earhart makes transmissions at quarter to and quarter past the hour, so her transmission at 17:45Z is right on schedule but it's not at all clear how old the "two hundred miles out" estimate from Noonan is or what it's based on.  It does seem to be too early to be based upon sunrise so it's probably just a DR estimate.  Her 06:46 Itasca Time (18:16Z) estimate "about 100 miles out" is more likely to be based on a sun shot.  People get all excited about her covering 100 miles in half an hour (200 knots) but assuming precision that doesn't exist.  Noonan could have the "two hundred miles out" estimate as early as, say, 17:20Z and he could have been way off.  The "about 100 miles out" estimate at 18:16Z, if based on a sun shot, should have allowed him to plot a reliable LOP of 157/337 on his chart.  He wouldn't know if his position on the line was north or south of his desired course to Howland but he'd know for sure that he was about 100 miles west of the line if it was advanced to fall through Howland.

Tell me if I am off base or rehashing some old discussion.
Not at all.  Rehashing old discussions is the way we check our work and catch old errors.
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