A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Amelia Earhart navigation- basic information.
From: Gary LaPook
Date: 2009 Nov 29, 03:52 -0800
From: Gary LaPook
Date: 2009 Nov 29, 03:52 -0800
I need to correct a typo in my prior post. The sun rose at Howland at 0615 Itasca time, 1745 Z not the 1645 Z in my prior post. gl Gary LaPook wrote: > 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 078� 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 067� T so the resulting LOP ran 157-337� 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 157�-337 �LOP > > > More later. > > gl > > -- NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To unsubscribe, email NavListfirstname.lastname@example.org