[BACKGROUND]
At the start of WWII the USN used the YE-ZB homing system developed by Frank Akers for assisting aircraft return to their carrier. All US carriers were equipped with a device called the "YE" transmitter. This was a UHF system which transmitted a Morse code letter denoting a specific 15° arc of a circle with the carrier at its center.
A disk with twelve Morse code characters rotates in sync with a directional antenna aboard the carrier. The antenna transmits a signal which is heard by aircraft within range if they are equipped with the proper receiver. Every 30° (360/12) of antenna rotation, the transmitted Morse code character changes. The pilots hear only the Morse code character that corresponds to the carrier's transmit antenna being pointed in the direction of the aircraft.
The order and placement of Morse characters on the wheel changed daily. The transmitter used a double amplitude modulation scheme and operated around 240 MHz - the double modulation scheme ensured that a casual eavesdropper would hear only a dead carrier unless he had the proper demodulator in the receiver.
The Navy aircraft used the AN/ARR-2 UHF homing receiver sometimes called a "ZB receiver". The pilots were given copies of the "daily" wheel so they would know which direction corresponded to each Morse letter on that day.
If the pilot picked up a Morse "M" for instance, he would "home" on it by turning to its designated direction. If, after a short while, he started picking up another Morse letter, due to cross winds or carrier movement, he would know he was moving on a tangential course in relation to the carrier. He would then make a corrective course turn and continue to home on the "M" signal. Since this was a UHF device it had better range (line of sight) at higher aircraft altitudes. It wasn't extremely reliable and some pilots were better at using it than others, so pilots had differing levels of confidence in it.
[OPERATION]
This simulation is designed for FS9 only. It includes a F4F-4 and a SBD-3 aircraft equipped with the UHF homing receiver with 5 selectable pre-set crystal controlled frequencies for reception of the YE signals from up to 5 carriers and/or ground stations. It also specifies the location and ID codes for these transmitters, which do not "move" during the simulation. YE Transmitters on three aircraft carriers are simulated. The Hornet and the Yorktown, positioned north of Midway Island, and the Stennis, positioned near San Francisco. The Stennis is not period authentic (too modern), but it is part of the stock FS9 scenery in case you don't want to use the "Battle of Midway" add-on scenery package. Another system, not directly related to YE-ZB navigation, is the arrester gear simulator. You can activate the tail hook on the F4F-4 or the SBD-3 and have it land on a carrier (trapping), for the successful completion of a mission. Omitting it will not harm the YE-ZB simulation. With sufficient headwinds simulating the carrier steaming into the wind, you can land and take off if you are careful.
The screenshot above is of a FS9 map. It shows an example result from the use of the YE-ZB: An F4F took off from the Hornet just ahead of the strike group and headed out to the northwest sector as a "sweeper". It "rode" the 300° true beam for about 25 minutes, then turned to 180° true and ded reckoned until the pilot received a strong S signal, (the 270° beam). Then the F4F returned to the boat homing on that beam.
The screenshot above shows the F4F-4 Grumman Wildcat returning "in the groove".
[THE F4F-4]
Due to the fact that I'm featuring the simulation of a navigation system used during WW2, and not featuring a new aircraft, I have taken some liberties with the design of the Grumman F4F-4 fighter. It is a modified Microsoft CFS2 aircraft. Some of the things I usually add to an airframe are missing. This is due in some part to the fact that it takes several minutes for the ZB receiver in the plane to "warm up", and start producing sounds. The good news is the warm up occurs even if the volume is turned down. Automixture is enabled in the aircraft.cfg file. The mixture lever is used only to shut off the fuel to the engine to safely stop it without backfiring. Autolean is not simulated.
The plane doesn't trim very well, so I cheated with a very simple AutoPilot which simulates the elevator trim (altitude hold), and the rudder trim (heading hold) and the elevator trim again for climbing/descending (Attitude hold).
Water injection for Emergency Power is not modeled.
Cowl flaps do not increase drag when they are open. They cool the engine.
There is a "all tanks" trap to eliminate that un-realistic condition provided by FS9. You are using fuel from the tank selected by the Orange Tank Selector switch. The two fuselage tanks are not modeled separately, but combined as the "main" tank.
The wings realistically fold and unfold by manual labor, not hydraulics. Feel free to command the ground crew to fold/unfold the wings. (Shift + 0).
Since the gear and flaps are hydraulically operated, they won't move until the hydraulic pressure is sufficient. However, if you lose engine power you may have sufficient "residual" pressure to retract/deploy the flaps a few times.
You must use your imagination with the use of the drop tanks because they don't show up visually in this simulation, but they can be used to increase the range of the plane. Combined, they hold up to 150 gallons of usable fuel. You may also dump the fuel (drop the tanks) by using the keyboard command for "release all drop tanks" (Ctrl + Shift + D).
That said, I did spend some time trying to get the performance specs correct. You should find the climb and cruise and range data reasonably accurate. Don't overlook the NAVAER Airplane Characteristics and Performance data. It is saved in the Aircraft/F4F_Wildcat folder as "F4F_NAV.pdf".
[THE SBD-3]
Because the F4F-4 is a little 'unstable', with his permission, I have included a terrific SBD-3 Dauntless simulated by Paul Clawson for FS9 in this package. It has been modified for ZB use as follows:
The fuel tanks have been combined in a single tank and "quantity" gauge.
The check list includes many flight details and the kneeboard 'ref' has useful charts and tables.
The Holly carburetor in the Dauntless has period realistic automatic mixture control. It has 4 positions, full rich, auto rich, auto lean, and idle cutoff. My simulation defaults to full rich with no indicator lights on, and the mixture control lever on the throttle tower is full up. By clicking on the upper (autorich) indicator light, you set the mixture control lever to the auto rich position with an f/a of 0.083. Likewise, clicking on the the lower light will switch the lever to the auto-lean position and an f/a of 0.070. Clicking on a lit light will turn off the auto mixture controls, and you can go to the throttle tower and drag the mixture lever to the idle-cutoff position to stop the engine.
The Sperry Autopilot in the real Dauntless was a primative "direction and pitch hold" type. To operate the simulation, you must have electric power, the Master Switch must be on, and as desired, you can select either altitude hold, direction hold, or both. With or without power the direction indicator is active, and it shows the gyro direction. Also the attitude control indicator is active, displaying the pitch and bank. Proper operation is to turn off the altitude hold and use the elevator trim to change altitude, and to turn off the Heading Hold to make large turns. Small turns can be made by clicking on the direction indicator while it is "on".
Your cockpit provides gauges for the pressure altitude and Outside Air Temperature for determining the density altitude for known Pressure altitude and OAT. Use the chart included in the SBD folder to make this conversion. Using density altitude rather than pressure altitude gives a more accurate TAS for navigation purposes.
Flight planning aids are provided in the aircraft documentation. They are available from the kneeboard, or you may print them out. You usually start with the intersection of a proposed Altitude with TAS. This provides a GPH which with the TAS lets you compute the cruise range. Don't forget to allow for head winds here. Adjust as necessary. Once you are satisfied with the proposed Altitude and TAS, determine the proper RPM from your location on the chart. The manifold pressure should be adjusted in flight to maintain the desired TAS. A prudent navigator would cross check fuel consumption periodically to make sure things were "on schedule". Note that the majority of the time, you should use 1400 RPM. Above certain altitudes, and above certain speeds you need to increase the RPM as shown. In between the lines you will get the proper data by using interpolation.
Note that the use of high/low blower settings are not simulated. Also, for cruise, use auto-lean for horsepower settings below 618, and auto rich otherwise. The simulation yields a close approximation to the real SBD-3 in speed, range, GW and altitudes.
Specific YE-ZB Instructions:
This simulation adds the Midway Battle Group some 200 NM north of Midway Island. It is a ficticious location selected by the authors of the excellent Midway Island Battle Scenery which is available from flightsim.com as "uss_mdwy.zip". I cannot identify the authors to give them credit. The USS Hornet and the USS Yorktown have the YE navigation system installed (as part of the YE-ZB gauge). Another carrier, the USS Stennis (CVN-74) which is near San Francisco is also operational with the YE system if you don't want to download the Midway Battle Group scenery. It wouldn't be a problem to add other carriers, or land based YE transmitters. If you need help contact the author (see below). There is a gauge that has to be added to the F4F (or any aircraft) to turn on and tune in the desired YE transmitter. It is called ZB. Finally, carrier operations are a lot more fun if you do tail-hook capture on landings. The author of FS9 software to implement that is Richard Hogen. His software is available at flightsim.com as "arrcab26.zip" It is not Scenery, and it is not required for YE-ZB operation.
The YE-ZB concept is similar to the US Radio Range navigation system. It has 12 fixed beams, 30° apart, rather than 4 "adjustable" beams, and it works in the UHF rather than the MF band. The transmitter doesn't just use "N" and "A", but uses Morse Code to identify which beam "direction" is being received. In the real system, the Code was changed daily, but in this simulation it is fixed.
A disk was handed to each pilot/navigator with the code of the day set on it. The beams are not "continuous", but repeat every 30 seconds for about 2 seconds.
Operations are simple enough. You need to be within line of sight of the carrier for the signal to be heard. (Seems strange when you think about it. You need a navigation system to find a carrier that is within line of sight. But when you realize that at 20,000 ft, the line of sight to the carrier is over 200 NM, you know that even without clouds or haze you can't see a tiny carrier at that distance). Just tune in the UHF signal, confirm that you are hearing the Hornet or another Carrier by listening for the Station ID which is different for each nearby carrier, and is broadcast every 5 minutes. Based on what beam code you hear, you will know what direction to fly to reach the tuned in Carrier. Don't forget to include the Magnetic Variation to stay on the beam, which is based on true directions. Also, don't forget that if the code you receive from YE is an "A", the carrier is to your south (not north), so you need to fly the "reciprical" of the direction of the beam to approach the Carrier. When you overfly the Carrier the beam will switch from (in this case) an "A" to an "M" so you know you have arrived. (or more precisely, you just passed over it).
The ZB receiver control box is in the aircraft. The volume control is "off" by default, and turning it clockwise will increase the volume of the received signal. The "frequency" selector offers a choice of 5 transmitters on different UHF transmit frequencies, as follows:
| Num | Title | RWY | Location | ID |
|---|---|---|---|---|
| 1 | USS Hornet | RWY 0 | North of Midway Island | ID = OJ |
| 2 | USS Yorktown | RWY 0 | North of Midway Island | ID = BP |
| 3 | USS Stennis | RWY 7 | West of San Francisco | ID = BZ |
| 4 | Charleston WV | Test Site | ID = CY | |
| 5 | Danville KY | Test Site | ID = XO | |
You can easily change the names and locations of the aircraft carriers or test sites, but Not the ID's. Selection of the proper crystals for changing the YE-ZB frequencies is automatic. Using narrow band receivers and "crystal" tuners, the friendly's had hundreds of channels to select from, while the enemy had to search all the channels to try to locate a transmitter. Instructions on how to make the change are in the file zbmods.htm.
In the cockpit, the YE-ZB received signal strength display is a needle indicating the relative strength of the beam due to being "off beam center". The sidelobes are down 40 db, the beam center is down 0 db, and the beam signal is down 10 db when the plane is exactly half way between two adjacent beams. This display is "after" the radio frequency automatic gain control that sets the receiver front end gain. The needle will show active received signals regardless of the volume control setting.
To hear the YE-ZB signal, the volume must be turned up, the frequency selected, and the receiver must be within line of sight of the Selected Aircraft Carrier. Power must be available to the Avionics on the Receiving Aircraft to see the needle move, or hear the Morse code Beam and ID letters. When the volume control is turned all the way down, the power to the receiver is turned off. You may see a delay of up to 30 seconds after turning the receiver "on" before you hear the YE signal. This is because the transmitter doesn't transmit in your direction continually. You will hear only a few seconds every thirty seconds.
The default carrier frequency is the USS Hornet on "1". Each YE-ZB tranmitter is on a different frequency with a different but fixed ID code. To change frequencies, click on the displayed carrier number using the mapping in the table above. As in real life, if the transmitters are closer than about 3 NM of each other, the system will not work correctly and all the codes will "blend together". Likewise if the Aircraft is within a few miles of the Transmitter, the codes will "blend together".
YE-ZB Installation Instructions: 1. Unzip the file YE-ZB5_DB.zip to a convenient directory. 2. Copy the file 'hc.cfg' to the main FS9 "Sound" folder. 3. Copy the file 'dash_1020Hz_960ms.wav' to the main FS9 "Sound" folder. 4. Copy the file 'dsd_361b.gau to the main FS9 "Gauges" folder. 5. Copy the folder 'zb' to the main FS9 "Gauges" folder. 6. Print the file 'YE-ZB2.gif' to hard copy for quick reference. 7. Copy the folder 'F4F4_WILDCAT' to the Aircraft Folder. 8. Copy the folder 'Douglas_SBD-3' to the Aircraft Folder.
Usage: The point is to simulate the way the pilots could find their way back to a carrier which is probably moving (changing location during the mission). An example representing a documented use (1942 Midway Battle) of the system is a good starting place. Creating your own flight/mission is recommended. Use Real WX. If you are using Carriers, don't forget to add stiff (24 Knot) surface headwinds to simulate the Carrier motion. The link below will take you to a section titled "the Tide Turns". It covers Coral Sea, Midway and Aleutians. The section on Midway has a bunch of different enteries including the battle reports of all three carriers.
http://ibiblio.org/hyperwar/PTO/TideTurns/index.html
[CREDITS AND ACKNOWLEDGEMENTS]
Paul Clawson Provided the Airframe, model and textures without modification for the original SBD-3.
Jim Daigneau for Technical Expertise, Research, Photography, and Beta Testing.
Austin Davis for Technical Expertise and Beta Testing.
Douglas Dawson for his xml sound gauge and assistance with XML coding.
Richard Hogen for the tail-hook capture software.
Jean-Pierre Langer for bitmaps, gauges, and documentation from his upgrade. He asks that credit be given Kalamazoo Museum who gave him the pictures he used.
Microsoft CFS2 team provided the basic F4F Airframe, gauges, model and textures.
Bowen Weisheit for his book "The last flight of Ensign Kelly" that describes the YE-ZB system in detail.
[COPYRIGHT & DISTRIBUTION]
The software contained in this archive is supplied as "freeware", and as such no fee or charge may be made for its use.
The author grants permission for the limited distribution in its PRESENT FORM ONLY. The freeware files included in this package remain the exclusive copyright of their respective authors.
[DISCLAIMER]
There is no warranty or guarantee of any kind, expressed or implied, for any problems whatsoever resulting from the use of this software. The user assumes all risk related to the use of these files.
Dave Bitzer
Email: bitzer7@comcast.net
November 2011