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    Re: Amelia Earhart's aerial navigation
    From: Douglas Denny
    Date: 2009 Nov 20, 15:09 -0800

    Many thanks to Gary LaPook for the detailed analysis of the Erhart/Noonan flight in post 10745.
    Thank you. It has answered some questions I had thought of, and many more that 
    I had not. It also raises others, probably not answerable.
    
    Having flown light aircraft, trained with ADF, and having some knowledge of 
    electronics (I restore for the fun of it old radio equipment) I can 
    appreciate the very interesting points made by Gary about the radio direction 
    finding aspects of this.
    
    I find it truly astonishing that they would take off with a useless radio 
    direction finder when their lives might have depended on it. Which it did.
    -------
    
    Direction finding by radio was an important navaid in those days at both sea 
    and more so for aircraft when they started long distance flying at this time 
    in the 1930s;  with the techniques of radio DF firmly established and lifted 
    from the marine experience.
    
    I agree,  as Garry pointed out, that flying, in fact just taxying around the  
    airfield transmitter,  will give perfectly good DF indication;  and exactly 
    overhead is easily indicated and recognised with the needle (in modern 
    equipments) indicating a given direction, swinging around lazily anywhere for 
    a moment or two, then indicating the opposite direction.  They are very 
    sensitive.  The only problem with the type of equipment used by aircraft and 
    at sea then is the need for hand rotation of the DF antenna, and there can be 
    two DF bearings found at 180 degrees so it is easily possible to fly away 
    from the required radio station if you go over it without noticing with the 
    hand-rotated antenna method.  Usually though there is provision to have a 
    'sense' aerial which tells you the correct bearing, so if he had overflown 
    the transmitter he should still know which bearing is correct ... but only if 
    the DF equipment is working of course.
    
    Gary is also spot-on with his pointing out that tubes (English English:- 
    'valves') equipment of the 1930 was very unreliable indeed, and servicing 
    such equipment was a big industry in its own right both in civil radios and 
    military.  Further, it would have been part of provision of military 
    establishments, so I presume there would have been at least one electronics 
    (radio) specialist on Itasca who would have been able to at least try to 
    repair the DF radio before they took off.
    
    Gary has made a convincing case that they took off without DF available, 
    relying entirely on celestial navigation. If so, this was a highly dangerous 
    thing to do given the pioneering flight to be made, and it seems they may 
    well have paid the 'ultimate penalty'.  In those days, to take off without a 
    working DF radio if you have one, on a flight of that nature, is highly 
    suspect at best and unthinkable if your life could depend on it.
    
    That raises several other questions,such as:-
    
    In which case, were they under duress to continue regardless? and if so what 
    pressures brought that about? 
    Why not wait a few days more, get better time signal checks, and repair the 
    radio DF finder before continuing?
    And - what provision would Noonan have made or could have made, for the event of not finding the island? 
    The film shows them throwing out all of the safety equipment including a life 
    raft. Ok they might still not have any realistic survival possibilities 
    sitting in one for long but better than just ditching into the 'oggin without 
    one at all.
    
    Gary provides an inevitable conclusion and convincing case, that Fred Noonan 
    must have been 100% certain he could use celestial navigation for the flight 
    without recourse to DF. As a professional, with the world looking on, would 
    Fred Noonan really have done this with the risks before him?   Fascinating.
    
    Douglas Denny.
    Chichester. England.
    
    =====================
    
    Original posting:-  #10745
    
    From: glapook---net
    Date: 18 Nov 2009 21:59
    Previous messageNext message
    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
    
    
    
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