YE-ZB 'Hayrake' Radio Navigation (aka "Zed Baker")
Prior to WWII, the US Navy realized a need for an improved navigation system that would allow carrier-borne aircraft to find their way back to the ship in the open ocean.
The system devised and implemented was the YE-ZB 'Hayrake' system. The letters don't stand for anything, they were just equipment designations. 'Hayrake' presumably referred to the shape of the transmitting antenna.
YE = designation of the transmitter radio on the carrier.
ZB = the radio receiver on your aircraft.
[The discussion of the system that follows is somewhat simplified.]
In the F/A-18, we commonly use TACAN to find our way back to the carrier. YE-ZB is literally the predecessor to TACAN. TACAN replaced YE-ZB in 1960, but performs essentially the same function. YE-ZB is 'old school TACAN.'
Like TACAN, YE-ZB requires the carrier to transmit a homing signal. In WWII, all US aircraft carriers were fitted with YE transmitters and rotating 'Hayrake' antennas.
- zb antenna.jpg (51.74 KiB) Viewed 1774 times
In the older NDB (non-directional beacon) methods, the pilots had to turn their aircraft or turn a small external loop antenna and try to decide where the signal was strongest. This was not a particularly precise method, and precision was kinda the goal when you were low on fuel and looking for a good place to land. Also, the old omni-directional homing beacons worked great for the enemy, too, and would have made it easy for them to find our carriers as well. That would be a bad thing.
Since the 'Hayrake' antenna was constantly rotating, it did not provide a constant signal in any one direction, so the enemy could not easily home on it.
The ZB receiver on the Allied aircraft did not have a directional antenna. It could not physically determine the direction of the signal. It was a simple (i.e. reliable) radio receiver, and all the pilot heard was a Morse code signal when the YE beam swept over his plane.
How did the pilot know which direction to fly?? Here's where the real ingenuity came in: the YE transmitter was designed to transmit 12 different Morse code letters as the antenna rotated through 360 degrees.
Each of the 12 Morse code letters corresponded to a 30 degree 'slice' of the compass.
- diagram 03.jpg (11.4 KiB) Viewed 1774 times
But if you knew the secret code, like if you remembered to write it down before you took off, you could easily figure out what 'slice of pie' you were in, and therefore what direction to fly to get back to the carrier. Which is pretty cool.
Say, for example, today's secret code was: ABC/DEF/GHI/JKL
That code would lay on the compass 'pie' like this:
- diagram 05.jpg (24.06 KiB) Viewed 1774 times
Now, you're flying around with your ZB receiver on, tuned to your carrier's YE transmitter frequency, and every 30 seconds you hear the Morse code letter H.
You know that you are in the H pie slice, in a radial that is somewhere between 210-240 degrees from the carrier.
- diagram 07.jpg (24.82 KiB) Viewed 1774 times
It should be pretty clear that you need to fly a reciprocal course, or somewhere between 030-060 degrees to get back to the ship.
- diagram 06.jpg (27.86 KiB) Viewed 1774 times
If you are a little off course, you might fly into one of the neighboring pie slices before you get to the ship.
Then your ZB radio receiver would start reading a G or an I. You would simply adjust your course accordingly, and in the same manner.
Eventually you will get within visual range of the carrier, at which point you can switch off the ZB radio receiver. You're back to mother!
- back home.JPG (17.58 KiB) Viewed 1774 times
