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Author Topic: RDF Training Manual  (Read 9069 times)

C.W. Herndon

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RDF Training Manual
« on: July 17, 2014, 01:37:46 PM »

For anyone who might be interested in learning more about the instructions for use of RDF equipment available in 1936, here is a portion of the Radio Materiel School Training Manual that covers the operation of RDF sets available at the time. It also has some interesting drawings of the equipment. The loop antenna shown on page 55 of the manual appears to be very similar to the one AE had on the Electra.
Woody (former 3316R)
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« Last Edit: July 18, 2014, 09:20:41 AM by C.W. Herndon »
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Jeff Victor Hayden

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Re: RDF Training Manual
« Reply #1 on: July 17, 2014, 01:57:56 PM »

Good find Woody!
This must be the place
 
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C.W. Herndon

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Re: RDF Training Manual
« Reply #2 on: July 17, 2014, 06:31:07 PM »

Thanks Jeff :D
Woody (former 3316R)
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Jeff Victor Hayden

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Re: RDF Training Manual
« Reply #3 on: July 18, 2014, 10:18:42 AM »

Up to page 20 of the manual and, I can see why AE was a tad reluctant to get too involved with the successful operation of the RDF. Still, if your life depended on learning it?

Back to page 1 as I have forgotten some of the important stuff already DOH!

"How is education supposed to make me feel smarter? Besides, every time I learn something new, it pushes some old stuff out of my brain. Remember when I took that home winemaking course, and I forgot how to drive?"

Homer Simpson
This must be the place
 
« Last Edit: July 18, 2014, 10:25:08 AM by Jeff Victor Hayden »
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pilotart

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Re: RDF Training Manual
« Reply #4 on: July 18, 2014, 01:50:53 PM »

Thank you Woody for finding that 1936 Manual   :)

(I read the whole thing.)

Up to page 20 of the manual and, I can see why AE was a tad reluctant to get too involved with the successful operation of the RDF. ...
Homer Simpson

This Manual had a lot more to do with the design, installation, testing and calibration of Radio Direction Equipment than Pilot/Navigator's proper use of the equipment.

The most beneficial method of teaching Radio Direction Navigation was (and is) the use of a simulator with a plotter and printer:

The original Link Trainer was created in 1929 out of the need for a safe way to teach new pilots how to fly by instruments.

Quote
"...The second major component is an external instructor's station, which consists of a large map table, a repeated display of the main flight instruments, and a moving marker known as a "crab." The crab moves across the glass surface of the map table, plotting the pilot's track. The pilot and instructor can communicate with each other via headphones and microphones. ..."
The above would have been the easiest way for Amelia and/or Fred to become a competent Instrument Pilot/Navigator. 

BUT...

Homing to a Station is briefly covered in Woody's Manual and could be easily taught without simulation to any Student Pilot (who was interested) in less than one day.

Where it becomes complicated and simulation helps is when you need to Navigate a Specific Path (or Track) To (or From is even more complex) while compensating for the effect of wind (drift).  They could have easily survived without this knowledge.

Homing to a Station is simply pointing your nose at it and as the Manual shows will result in a downwind curved track to the station, but it gets you there.

It was tragic that both Amelia and Fred considered Radio Navigation to be strictly the responsibility of the Radio Operator and they had absolutely no interest in learning anything about the subject.

Just the most basic knowledge (a one day course) would have saved their flight and lives.

The only need for Morse Code is to Identify the Transmitting Station and the two, three or four letters are constantly repeated at a slow enough speed for a non code reader to confirm identification.

All they would have needed to do after receiving and Identifying Itaska's 500 Khz* Beacon would have been to rotate that Loop to find the two Null's and determine which one was toward (rather than away) by a simple Heading Change to mark the direction of bearing change.

They would then have oriented the Loop Forward (as was pointed out in another thread) and keep the nose pointed at the Itaska.

*500 Khz was just one of several Frequencies that Itaska had in the range used for Radio Navigation, but Amelia requested that they transmit continuous A's (dit-dah, dit-dah, etc.) on 7,000 Khz which was well above the Frequency she needed to Home on.

From Half Way down this Wikipedia site:
Quote
In use, the RDF operator would first tune the receiver to the correct frequency, then manually turn the loop, either listening or watching an S meter to determine the direction of the null (the direction at which a given signal is weakest) of a long wave (LW) or medium wave (AM) broadcast beacon or station (listening for the null is easier than listening for a peak signal, and normally produces a more accurate result).
(LW) and (AM) refer to Frequency Ranges needed.

From Amelia's response to Itaska's 7 Mhz A's, she Knew to look for the Null, but did not know to request it on an LW (or AM) Frequency from Itaska...  She would have also needed to do the brief heading change to choose the correct one of the two Null's she would identify.

(As documented in that Wiki, there are ("Huff-Duff") Direction Finders which can determine direction from Higher Frequency Transmitters, but they would never fit in an Aircraft.  Itaska had installed one ashore on Howland Island, but had run its Battery Dead by playing with it before Amelia had gotten in range.)
Art Johnson
 
« Last Edit: July 18, 2014, 01:57:37 PM by pilotart »
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Monty Fowler

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Re: RDF Training Manual
« Reply #5 on: July 24, 2014, 04:33:58 PM »

It was tragic that both Amelia and Fred considered Radio Navigation to be strictly the responsibility of the Radio Operator and they had absolutely no interest in learning anything about the subject.

Just the most basic knowledge (a one day course) would have saved their flight and lives.

Exactly. Like the old saying goes, There are old pilots, or bold pilots, but never old, bold pilots. An ounce of prevention ....

LTM, who prefers to Be Prepared,
Monty Fowler, TIGHAR No. 2189 ECSP
Ex-TIGHAR member No. 2189 E C R SP, 1998-2016
 
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pilotart

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Re: RDF Training Manual
« Reply #6 on: August 07, 2014, 12:22:24 PM »

It was this post/thread (...Where is SHE ???) that came to mind when reading The Hooven Report:
But is 'loss at sea' such a fair assumption?  What does an able navigator with even a marginally-able transoceanic pilot do if faced with the prospect of failing to make planned landfall?  Does he drive the search until the fuel is gone, or does he drive toward a better prospect of alternate landfall?
Plan 'B' in my mind would be Radio Direction Finding, which we know they tried.  (of course Common Practice today and for many decades past has been to list one or two "Alternate" Aerodromes on an International Flight Plan, this might be plan 'C' and certainly must be completed before fuel reserves are gone...)

From the HoovenReport
Quote
...she did not realize that the loop would be substantially useless at frequencies above 1500 kc, either as a loop or as an antenna. Thus it was that she did not hear the Itasca’s signals until she was closest to Howland, at which time she finally reported hearing the signals but that she could not get a minimum.

Forty five minutes later came the final signal reporting the “position line” of 157-337. ...

It was receiving Itasca's Morse Code 'A's... (dit-dah's...) that she reported hearing through her Loop, but the 7500 kc frequency was way to high for her to get a direction (or minimum) from.  Notice that Hooven states that her Loop would work better as a receiver as well at frequencies below 1500 kc.

Forty-Five minutes that keeps them within range of Itasca's radio receivers, could they have been trying RDF for those :45 or flying a Gary LaPook Search Procedure (possibly both) before turning on the 337/157 line (or Heading).

I am well aware that continuing (after first attaining 'the line') on first a 357° and then a 157° Heading (in and out of the 'donut hole') for that :45 could still result in Itasca's reception as reported and get them closer to Niko with more fuel remaining and lower tide water level on that Reef/Runway.

Frederick J. Hooven goes on to say:
Quote
it is highly probable that Miss Earhart finally heard the Itasca’s pleas for her to transmit on 500 kc since it was not possible to take bearings on 3105, so she may finally have switched her receiver to 500 kc and have taken a radio bearing. Since the 157-337 line is one that passes both through the Phoenix group and Howland, it may also have been that Noonan advised her to go east until she made such a bearing, then turn and fly along that line.

Unfortunately the direction finder was unable to tell which direction to turn to go toward Howland due to the ambiguity of its loop signal.
She seems to have had a (good) habit of first announcing on old frequency before switching transmitter to new one and since Itasca's next reception was still on 3105 ks, it seems highly unlikely and of course if she had, then Itasca could have gotten her direction from their Loop Antenna. Although the Lockheed's Loop could take a Bearing on 500 ks it is unlikely that Itasca would be transmitting continuous A's, as that was the International Distress Call Frequency and Itasca would leave it open for their reception.

We know Amelia had requested 400 ks and Itasca had Voice and Code ability to transmit on a Low Frequency of 425 ks (as well as 500 ks).  Is it known if Itasca also did continuous transmitting on a Low Frequency such as they did on the High Frequency of 7500 ks?

They obviously were aware that you need 'Low Frequencies' to Loop for direction, yet their log only mentions A-s on 3105 & 7500 kc...

The Itasca Radio Log talks about 3105 and 7500 ks and only mention of 500 ks was their request for the plane to transmit dashes for the Itasca's Loop Direction Finder on 500 ks.

As far as "...ambiguity..." Hooven's Advanced RDF (which Amelia had removed) solved ambiguity, but surely he knew (as well as AE&FN ???) that ambiguity can be resolved by a simple turn to track the bearing's change.
Art Johnson
 
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