NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Amelia Earhart's aerial navigation
From: Greg Rudzinski
Date: 2009 Nov 19, 09:54 -0800
From: Greg Rudzinski
Date: 2009 Nov 19, 09:54 -0800
Excellent post Gary. Thanks. A few more questions. The abrupt ending of voice radio transmission implies trouble. Is it possible that the batteries/magneto and or fuel pump failed then causing a ditch short of Howland on the LOP approach ? What were there chances without a life raft? Greg On Nov 18, 9:59�pm, Gary LaPookwrote: > Greg Rudzinski asked: > > Maybe Gary can comment on the following: > 1. Time tick before departure. > 2. Sobriety of Noonan. > 3. Life raft. > 4. Radio antenna. > 5. Head winds. > 6. Celestial opportunities. > 7. Sleep deprivation. > 8. Was it possible to fly right over Howland Island and not see it? > 9. Was Howland charted correctly. > 10.What would have been a better less risky route? > > Gary wrote: > > Fred may have had a drinking problem but many people with such a problem > manage to show up sober for work on Monday mornings because their jobs > depend on it. Noonan had an even greater reason to show up sober, his > LIFE depended upon it. They landed in Lae on June 29th. The night they > arrived in Lae he went out drinking with Collopy and Heath and they got > toasted. Collopy took him back to his hotel about midnight and Noonan > was wobbly. On the 30th work was done on the plane and they attempted to > get a time signal so that they could leave on July 1st but were not able > to get the radio time signal so they had to delay the departure one day. > On July 1st Noonan turned down an invitation to go out again with > Collopy and went to the radio office where they finally got the time > signal at 10:20 p.m. Earhart and Noonan were back in their hotel by 11 > p.m. so no bender the night before departure. They took off at 10:00 > a.m. the next day, July 2nd and the flight lasted over twenty hours. > Even if Fred had had to be poured into the plane (and the movie of the > departure shows him steady as he got into the plane) he would have had > plenty of time to sober up on the way to Howland. Because of all this it > is very unlikely that any drinking problem Fred may have had contributed > to the disappearance. This story was pushed to put the blame on Fred and > totake the focus off of AE's actions. > > I have posted the following before on another forum and it will answer > some of the questions. > > "Paul, I for one never believed that Noonan made a navigational error. > He was too experienced, too motivated (his life was on the line) and > the techniques being used were well proven and of sufficient accuracy > to have allowed them to find Howland." > > There is a lot of evidence that he was careful and competent. I think > all the stories that came out after the flight besmirching him > personally and his abilities were for the purpose of exonerating the > popular and well known American heroine celebrity AE from fault for the > disappearance, Fred was made the fall guy since he was an unknown nobody. > > I posted before that Fred would have been motivated to do a very > competent job on this leg since it was the sole reason that he was > brought along. Further proof of that was written by AE in "Last Flight" > ( the book written by AE as she went around the world and sent back > prior to her last flight), > > �"Fred Noonan has been unable, because of radio difficulties, to set his > chronometers. Any lack of knowledge of their fastness and slowness would > defeat the accuracy of celestial navigation. Howland is such a small > spot in the Pacific that every aid to locating it must be available." > > They had to delay the flight for a whole day so that �Fred could get a > radio time signal (it was broadcast only once a day and there was > interference the first day) so he could check his chronometers to > determine how fast or slow they were. This would not have been necessary > if they were just planning to use radio bearings to find Howland. > > This necessity for very accurate time is probably not understood by most > people on this forum. The earth turns at a rate of 900 knots (900 > nautical miles per hour, or 1035 mph) at the equator which means that it > turns one nautical mile every four seconds. Without getting into the > details of how celestial navigation computations are done, it works out > that if your chronometer (a very accurate clock) is slow by just four > seconds then your celestial computations will place you one nautical > mile further west than where you actually are. If it is fast then you > will think you are east of where you actually are. It doesn't take too > many seconds of unknown chronometer error to cause you to miss Howland > if using only celnav. Since their course was mainly eastbound they only > had to be sure that they did not pass too far north or south of Howland > so as to be beyond the range of Itasca's transmitter. Precise longitude > would not have been needed if they planned to just use the radio > direction finder for final guidance to the island. Since they were > willing to wait a whole day just to get an accurate time check it shows > that they planned to have celnav at least as a backup to radio direction > finding and knew that they would need the maximum accuracy possible in > that eventuality. > > If they were just going to use radio bearings then AE didn't need Fred, > she could do that herself since the radio equipment was in the cockpit. > It is obvious, then, that the entire world flight was planned around the > need to use celestial to find Howland. > > I had also posted that Fred would have pre-computed the landfall > procedure so that it could be easily accomplished after a long and > tiring flight. I believe that he would have done this on the ground > before takeoff either that morning or the day before or early in the > flight before becoming fatigued. These computations would have only > taken about one hour using Dreisonstok and plotting the �altitude curve > on graph paper for the sun's and moon's altitudes as calculated at > Howland. With this pre computed he could take many shots with his > sextant and compare the measured altitudes with those on the graph and > know instantly if they were staying on the LOP to Howland. No further > complex computations would need to be done in flight while approaching > the island. > > Even if they were planning to use a radio bearing to find Howland and > celestial was planned only as a backup Fred would have known not to > count on the radio working since it had failed them approaching Dakar. > In fact he didn't have to think back that far. The day before the last > flight they had had their radio repaired and had test flown the plane to > check out it's operation. They were unable to get a null which meant > that the radio direction finder WAS NOT WORKING. For some inexplicable > reason they ignored that blatant fact and decided that the reason they > could not get a null was that they were too close to the station. > Certainly Noonan appreciated this was at least a potential problem and > would have redoubled his effort to make sure that he did everything > possible to ensure that celestial would get them to Howland. If he > hadn't been confident of this they would not have left with an unproven > radio direction finder. > > I don't know how many instrument rated pilots we have on this forum. I > am an airline transport pilot and I have also been an instrument flight > instructor since 1972 so I have some knowledge of how radio direction > finders work since they were common navigation equipment �in airplanes > used for flight in the clouds until the recent development of GPS. (I > also have a radio amateur operators license, call sign KA9UHH.) > > When flying on instruments you are inside the clouds and can't see any > landmarks, obstructions or airports. In order to navigate without visual > references you rely on different systems of radio navigation equipment > which for many years included radio direction finders very similar to > the one installed in NR16020. This equipment uses long wave radio > signals in the band of 190 to 535 kilocycles (now kilohertz) just below > the A.M. broadcast band and including 500 kcs the international calling > and distress frequency. This was the frequency that Itasca was > broadcasting on. AE's radio direction finder should have been able to > get a null and and so determine the bearing to fly to get to Itasca. > > Getting a null involves turning the loop antenna until it is lined up > with the direction of the incoming signal which is shown by the received > signal getting �weaker and weaker until it disappears, this is the > "null." If you turn the antenna past the null the signal starts to get > louder very rapidly. The width of this null is very narrow so that the > bearing can be determined very accurately. > > This type of equipment is good for a very long distance mainly > determined by the power of the transmitting station. For enroute > navigation, airways, like "highways in the sky" were created with radio > transmitters placed on the ground at each end of each leg of the airway. > The signals have to be strong enough so that you can receive them at the > halfway point of each airway leg. You track outbound from one station > until halfway to the next station then start following the signal to the > second station. As an example, a route I flew many times was �"A17" from > Bimini, Bahamas to Puerto Rico. You take off from Miami or Ft. > Lauderdale and tune in the radio station on Bimini which transmits on > 396 kcs with a Morse code �identification of "ZBB." You use the radio > direction finder to head for Bimini which is 55 NM from Ft. Lauderdale. > After passing over Bimini you turn to a heading of 121� magnetic and > track outbound until halfway to the next radio station located on the > island of Grand Turk at the very southeast end of the Bahamas chain. > Grand Turk transmits on a freq. of �232 kcs with the ident of "GT." > After passing GT the next station is located on the north shore of > Puerto Rico about 60 miles west of San Juan transmitting on the > frequency of 391 kcs, ident "DDP." Now here is the important part, the > leg from ZBB to GT is 516 NM (593 miles). This means that you can > receive the signal 258 NM at least from each station. It is reasonable > to believe that had AE's radio direction finder been working she would > have been able to hear Itasca at a similar distance. This is born out by > the fact that Itasca heard AE's much less powerful transmitter several > hundred NM out. > > Since the leg from Lae to Howland is 2222 NM and the common estimate of > DR accuracy is 10% of the distance flown then one could expect to fly > the distance from Lae to Howland solely by dead reckoning and still be > confident of coming within in 222 NM of Itasca and so be close enough to > pick up the radio signal and track inbound to Howland. So if AE was > willing to rely only on radio she didn't need Fred at all. In fact, they > saw Nauru island about half way so the dead reckoning leg would have > only been about 1,000 NM so the DR error should not have exceeded 100 > nm. But obviously they wouldn't just rely on radio. > > It is hard for young people today who have grown up with cell phones, > the internet, TV, satellite dishes and IPODs to have any gut feeling for > the unreliability of radio equipment in the 1930s. Modern equipment and > systems are so reliable people don't even think about it anymore. But in > the '30s comparing the reliability and trust in complicated pieces of > electronic equipment with resistors, capacitors, and tubes that burned > out without warning in your own equipment and in the transmitting > equipment that was not under your control with the proven reliability of > a simple sextant, a book of tables and a clock (or two clocks for > redundancy) and celestial won hands down. That was why AE hauled Fred > all the way around the world. > > Back to the use of radio direction finders. When flying on instruments > you eventually have to descend to land at an airport that you can't see > while you are in the clouds that might be in a valley surrounded by > mountains. You fly to the approach radio station on a specified course > and altitude and then after you pass over the transmitter's antenna you > know it is safe to descend �down to the minimum decent altitude that has > been established by the FAA for the approach to that airport which takes > into account the height of surrounding obstacles and the altitude of the > airport and the distance from the transmitter to the runway. When you > pass over the antenna and start your final decent you start a stop > watch. Your approach chart tells how many minutes and seconds it will > take you to fly from the station to the runway at various ground speeds. > After you descend to the minimum descent altitude you maintain it until > you see the runway of until the time runs out by which you know you have > passed over the runway without seeing it so you must climb and go to > your alternate. > > The reason I went through this long winded explanation is so everyone > will understand that the radio direction finder works right over the > transmitting antenna, you can't get closer than that. AE dismissing the > failure of her radio direction finder because she thought she was too > close to the transmitter shows either she didn't understand its > operation or she was satisfied that celestial alone was sufficient to > get them to Howland. I think the latter explanation makes the most sense > since they could have (and probably did) check the radio direction > finder operation as they flew farther away from Lae and continued on > even though it was apparent that it wasn't working. Again, this would > have made Fred work real hard on his celestial since he knew, actually > KNEW, that he couldn't depend on the radio. > > Based on all this I believe Fred knew he had to do an exemplary job of > celestial navigation and if the radio did per chance work when they got > near Howland then "no harm, no foul." He had confidence in celestial and > knew it had sufficient accuracy to locate Howland or he wouldn't have > gotten into the plane. > > gl -- NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com