A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Amelia Earhart navigation- basic information.
From: Gary LaPook
Date: 2009 Nov 28, 00:28 -0800
From: Gary LaPook
Date: 2009 Nov 28, 00:28 -0800
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 NavListemail@example.com