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    Re: Amelia Earhart navigation- basic information.
    From: Gary LaPook
    Date: 2009 Nov 29, 03:28 -0800
    Ronald P Barrett wrote:

    "You are right for the most part... however where is the dip correction allowance and how did that final celestial observation take place(mechanically)? The lack or the application of this celestial correction (dip) applied to the observation could well place one out of sight of the destination island. Being a former WesPac oceanic flight navigator in mostly unpressurized planes (C-124s) I can tell you the aircraft configuration will determine your possible observation points. And lil'flat islands are very hard to discern in the Pacific Ocean.

    To the point:the statement that a sun LOP of 337/157 is A-OK to state. That it was ever at some point in time, corrected for position, time, and passed through destination is highly subject to all corrections applied to the shot-LOP; the most critical being:how was the observation exicuted?

    Noonan could have shot off to the left(even though the bigger observation aft cabin window was on the right side of the plane). The on course-on-heading aft cabin off to the left shot, down (dipped) to the horizon was and may have been impossible in the L-10AE though. That visualization has as best I know, never been verified.

    The dipped-shot off the nose (from the front) of the L-10AE has not been verified either. "

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

    I don't understand your concern about dip since Noonan was using a Pioneer bubble octant and you do not apply a dip correction to bubble sextant observations. See:

    http://www.fer3.com/arc/imgx/A-5-Manual.pdf

    No correction for coriolis either since the flight was at the equator.


    If  by "dipped-shot" you mean visually observing the sunrise in relationship to the visible horizon then you would have to allow for dip the same as if you were using a marine sextant set for zero degree altitude. But why would Noonan do that since he had a bubble octant to use? The dip correction table in Dreisonstok only tabulates corrections up to an altitude of 4,000 feet so  to use that table he would have to be below 4,000 feet. Of course if he could do square roots in his head or on a slide rule then he could have computed the dip correction for any altitude (assuming he knew the formula.)  If using a marine sextant the sextant altitude (Hs) of the sun at sunrise (appearance of the upper limb) as observed from 10,000 feet is zero degrees, lined up with the visible horizon. The dip from this altitude is 97 minutes so the apparent altitude (Ha) that you would enter the refraction table with is minus 1 degree and 37 minutes. The refraction correction for a sight from 10,000 feet for an Ha of minus 1 degree and 37 minutes is minus 50 minutes. Include semi-diameter and the observed altitude (Ho) is minus 2 degrees and 43 minutes. If this sight was taken with a bubble sextant then the Hs would be minus 97 minutes, the same as the dip so you don't have to apply the dip correction. You then end up with the same Ho after applying refraction and semi-diameter..

    This brings out the real problem with taking an altitude below horizontal, that of determining the refraction correction. The 50 minute correction I just mentioned comes from the modern Air Almanac correction table and this table was not available to Noonan. He carried Dreisonstok and the Nautical Almanac for 1937. I have attached the refraction correction tables from these tables and the lowest altitude that they provide a refraction correction for is 6 degrees above the horizon. The other commonly available sight reduction tables of the time, H.O. 211 and Weems Line of Position Book, also had refraction tables limited to altitudes above 5 degrees 30 minutes. Noonan would have no way to compute a refraction correction.

    Some people have claimed that Noonan just observed the sunrise, computed an LOP from that observation, advanced it to pass through Howland, flew to the LOP using just DR based on his ground speed, turned on to the LOP and started looking for Howland. Basically they are claiming that Noonan must have opened the door and thrown his octant away after he saw the sunrise. Does this make any sense? The sun rose at Howland at 0615 Itasca time, 1745 Z ( I just noticed the typo in my prior post, 1645 Z should have been 1745 Z) and it had climbed above 6 degrees a half hour later at 1815 Z. We have all been taught to avoid low altitude sights due to variability in the refraction and Noonan would also have avoided low altitude sights. In fact, he was constrained to take sights above 6 degrees by his refraction table, he had no choice and he could not take a lower altitude. He would have continued to use his bubble octant to take sights after the sun was above 6 degrees and would have taken additional sights after he had turned onto the LOP to ensure staying on it to Howland. At this point he would have a clear view of the sun through the left window since the relative bearing would be 270 degrees (assuming he intercepted the LOP northwest of Howland which makes the most sense) and he had taken several sights near this relative bearing on the way to Hawaii. Another reason Noonan could not take negative altitudes is that the Pioneer instrument only has a scale from zero to ninety degrees, no negative altitudes. I have attached a photo of the scale of this type of octant showing it set on zero

    Another reason he could not use negative altitudes is that the sight reduction tables he was using, H.O. 208, Dreisonstok, had no provision for computing negative altitudes. In fact none of the other sight reduction tables of the time provided for computing negative altitudes, not H.O. 211, Weems, Hughes, or Nories. Even when inspection tables were developed they too did not provide for negative altitudes. H.O. 214 only has altitudes above 5 degrees, H.O. 218 only above 10 degrees, and H.O. 229 only above zero. The only tables that provide for negative altitudes in H.O. 249 which were a much later development and provided negative altitudes for use by our Air Force flying B-52s at high altitudes on the way to Russia in case the only available star might be a low altitude shot. But even then, B-52 navigators would prefer to use higher altitude sights.

    You seem concerned with the viewing opportunities for Noonan. AE wrote on page 47 in "Last Flight,"  "The plane had been fitted with special windows" for use by the navigator. These side windows were larger than standard and made out of flat glass to eliminate unwanted refraction. We know from the Hawaii and Atlantic charts that he was able to take sights in all direction and up to 75 degrees high. I have attached a table of the relative bearings and altitudes shot while flying to Hawaii and to Dakar. You can see that Noonan was able to take sights in every direction and at many altitudes. The Pioneer octant makes it easy to take high altitude shots because the index prism is located at the front of the instrument only one  inch back from the front. This allows you to place the octant right up against the window and it only takes an 8 inch high window to allow sights up to 80 degrees. Also the eyepiece in 9 inches back making it easy to place the octant well in front of you against the window. This is different from the MA-1 where the index prism is 4 inches back from the front requiring a much taller window to allow high altitude shots.

    gl


     


    Ronald P Barrett wrote:
    You are right for the most part... however where is the dip correction allowance and how did that final celestial observation take place(mechanically)? The lack or the application of this celestial correction (dip) applied to the observation could well place one out of sight of the destination island. Being a former WesPac oceanic flight navigator in mostly unpressurized planes (C-124s) I can tell you the aircraft configuration will determine your possible observation points. And lil'flat islands are very hard to discern in the Pacific Ocean.

    To the point:the statement that a sun LOP of 337/157 is A-OK to state. That it was ever at some point in time, corrected for position, time, and passed through destination is highly subject to all corrections applied to the shot-LOP; the most critical being:how was the observation exicuted?

    Noonan could have shot off to the left(even though the bigger observation aft cabin window was on the right side of the plane). The on course-on-heading aft cabin off to the left shot, down (dipped) to the horizon was and may have been impossible in the L-10AE though. That visualization has as best I know, never been verified.

    The dipped-shot off the nose (from the front) of the L-10AE has not been verified either.

    There is the possibility that Noonan could have had the plane turned (in this case, left or right) to do an abeam dipped observation of the sun rise. In this case it would have been a +90 if to the right, and a less-than 90 degrees if turned to the left. This sort of large turn would have been called for because of the fat-wing-nacelle and engine being in the way of the aft observation windows which were in the very aft sides of the plane. In either case the plane would have to have been steady and in level flight(to get a good observation) on this new heading for a period of minutes. Then they would have to get quickly back on course. I have done such navigating over the Pacific myself and the pilots never did like this! I also did "doubledrifts" this way. The pilots did not like this either.

    On the radio side: there were two radios on this L-10AE. One was a low KC RBN. The other was the HF. It was the HF reel/wire that was removed in Florida. NOT THE RBN LOOP! The RBN LOP (RCA) and sense antennas be seen on all of the L-10AE pictures published to date. The LOOP tuner was the radio/control head that was placed pver AE's right ear in the ceiling of the cockpit.

    The HF( Western Electric 130C-HF transmitter with 20B receiver) was in the aft cabin. The HF had two antennas(one having been removed, the reel in Florida) and the permnant wire which ran from the crown mast (shown atop the HF radio aft cabin location) to the tail fins and back to the fuselage feed through. Ref pages 20-21 of Missing Believed Killed, by Roy Conyers Nesbit.

    Pan AM Navs were use to this HF because Pan Am was a Pioneer in this radio and even manufactured them and there crews used them, as a first in the industry. So Noonan no doubt was one of the most skilled in the use of this type of radio because he was on the very lead crew exploring the trans Atlantic and Pacific flight routes. There is a very early (I think Pan Am  Number 2 HF) in the Airline History Museum here at Kansas City. I have opened it up and the design and manufacturing thereof can be seen to be excellent for the time it was built in.

    One of the problems with AE and the HF comm with the CG was that the CG had only one dedicated antenna on the Itasca! The CG had to switch back & forth to go to voice and/or to key code. No matter the CG could not R/T at any one time in both modes. So there were times the CG was totally off the air. Granted all the rest as far as a "Communications & Navigation plan" was loaded with miscues.

    Lucky for all, the Army Air Corps formally created flight "navigators" with the Coral Gables Class of 40-A which went forth and taught us all the skills needed to be able to navigate with great precision right up to the GPS. The first classes were all taught there at the University of Miami, Dinner Key and by Pan American Airways, led by Noonan's friend and Chief Nav Charles Lunn.

    I have been lost, but now I am found! Ron Barrett, President Air Force Navigators Observers Association (AFNOA)



    --- On Sat, 11/28/09, Gary LaPook <glapook---.net> wrote:

    From: Gary LaPook <glapook---.net>
    Subject: [NavList 10833] Amelia Earhart navigation- basic information.
    To: NavList@fer3.com
    Date: Saturday, November 28, 2009, 2:28 AM

    Amelia Earhart (AE) attempted to fly around the world in 1937 at about
    the equator. Some prior around the world flights had been made at higher
    latitudes so encompassed a shorter route. The original plan was to fly
    westward and refuel in the air over Midway Island since there was no
    airport there, only a seaplane base. The Navy put the kibosh on that
    plan because of AE's lack of the piloting skills for the in flight
    refueling. The next plan was to fly westward including a leg from Hawaii
    to Howland, about 1800 NM, where a runway was bulldozed for her use.
    (There is speculation that this also furthered the claim of U.S.
    sovereignty's over Howland and the other Line Islands. It may have also
    furthered Pan Am's plans for routes across the Pacific.)  The plan was
    for AE to be accompanied by Harry Manning as navigator and radio
    operator and also by Fred Noonan as navigator as far as Howland and for
    AE to continue on alone after that with Manning and Noonan to return
    from Howland by ship. It is obvious that everyone appreciated that the
    leg to Howland was to be the most challenging navigationally

    They flew from Oakland to Hawaii on March 18, 1937 (Z) as planned with
    Paul Mantz also aboard, he was a technical adviser to AE. Noonan and /or
    Manning took 14 celestial shots during this flight as well as a number
    of radio bearings. We have the charts used on this leg. On the
    subsequent takeoff with Manning and Noonan onboard AE lost control of
    the plane resulting in a ground loop and significant damage to the
    plane. The plane was crated up and shipped back to California on the
    Lauraline for repairs at the Lockheed plant in Burbank California. It
    was decided to reverse the route to travel eastbound after  repairs with
    the toughest navigation leg to be Lae New
    Guinea to Howland. This necessitated carrying a navigator for the the
    entire flight. Manning claimed that he had to get back to his full time
    job as captain on a ship but he was supposed to have said that he had
    lost confidence in AE's abilities so he did not participate in this
    second attempt leaving Noonan as the sole navigator. Noonan did not have
    Manning's radio skills which proved to be a serious problem later in the
    flight. They flew from Oakland down to Natal Brazil. On June 7, 1937
    they flew from Natal towards  Dakar Senegal but missed that destination
    and landed about 150 NM further north at St. Louis. We have the chart
    used on this flight showing five sun lines.
    They then continued on around the world and arrived at Lae N.G. on June
    29, 1937. On the 30th the spark plugs were changed and other maintenance
    accomplished. They had planned to depart the next day, July 1st, but
    were unable to get a radio time signal so put off the departure until
    the 2nd. They took advantage of the delay to do a test flight on the 1st
    to check out the operation of the RDF which didn't work. They ignored
    this problem and departed at 10:00 a.m. (ZD -10) on July 2nd, 0000 Z
    July 2nd, for a planned 18 hour flight to Howland. This leg is 2222 NM
    long and the course is 078º True approaching the island. The rumb line
    and the great circle differ by less than one degree and one-tenth of a
    nautical mile since the flight was along the equator. The Coast Guard
    Cutter Itasca was off shore of Howland ready to transmit a homing signal
    for AE to follow to Howland and had the capability of direction finding
    on transmissions made by AE if she transmitted on the correct frequency
    within the frequency range of the Itasca's equipment. Itasca had cabled
    to Lae on June 28th listing the frequency ranges of its radios. Its RDF
    covered only from 270 to 500 kHz. The Itasca maintained time with a ZD
    of + 11.5. AE maintained two way radio contact with Lae for five hours
    on her daytime frequency of 6210 kHz but contact was lost when she
    switched to her night time frequency of 3105 kHz to attempt to call Itasca.

    AE's radio could transmit on 500, 3105 and 6210 kHz only but she could
    tune her receiver to any frequency. Communications on he international
    calling frequency of 500 kHz was in Morse code and neither AE nor Noonan
    were proficient in Morse though manning was. Since they did not plan to
    utilize Morse code without Manning ,the 250 foot long trailing wire
    antenna used only for 500 kHz was removed in Florida to save weight. It
    is possible that her radio might still have been able to put out a
    significantly weakened signal of 500 kHz using the remaining antenna.

    Noonan and AE most likely planned to use radio navigation for terminal
    guidance as they approached Howland since radio navigation gets more
    accurate as you approach the antenna while celestial's accuracy remains
    fixed. AE could have done any necessary radio work by herself so did not
    need to carry Noonan all the way around the world if they had not
    planned to use celestial, at least as a backup method for finding Howland.

    When they were unable to get the radio signals they needed it is almost
    certain that Noonan would have turned off to the left to intercept a sun
    line LOP to the northwest of the island. From sunrise at about 1645 Z
    (0615 Itasca time) and for more than and hour afterwards the azimuth of
    the sun remained 067º T so the resulting LOP ran 157-337º T. Noonan
    would have intercepted this LOP and followed it to Howland using the
    "single LOP landfall procedure" popularized by Chichester as "deliberate
    error" and also known as deliberate offset. This method had sufficient
    accuracy to allow them to find Howland and was taught to all flight
    navigators and was used thousands of  times successfully during WW 2 and
    after to find small island destinations. In addition, the moon was also
    visible and provided  good cuts with the sun line to provide daylight
    fixes.

    AE's last transmission at 2013 Z (0843 Itasca Time) stated they were on
    the 157º-337 ºLOP


    More later.

    gl

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