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Sikorsky H-19 / S-55 Chickasaw

Add this to the ever-growing list of WIP vehicles that will never leave WIP status.

The
was initially developed by Sikorsky as a private venture, designed to act as a testbed for new configurations that could carry more while being easier to maintain than the pioneering helicopters of the 1940s. Its first flight was in late 1949, after which it was evaluated by the US Air Force and Navy, the Air Force model seeing service trials in Korea in 1951 which would lead to its adoption by the Marines.

After some years of operation in rough seas, it was found that the rotor on a pitching and rolling deck could be angled further than designed, resulting in tail boom strikes. In 1956, a modification was made to the design which included a 3 degree declined boom and a redesigned tail fin and rotor. The blueprints I used had this modification.

The most distinctive feature of the S-55 (and its future development, the s-58) is the nose-mounted radial engine and consequential high cockpit position. Some call it an ugly duckling, but I see a beautiful swan.

Most of the flight instruments that were present in the original H-19 are also present in this 1:1 recreation.

• ADI - Attitude direction indicator, as close as I can get to an artificial horizon on an instrument panel
  
• TBI - Turn and bank indicator, top needle shows turn rate and bottom needle acts as the turn/slip ball level
  
• BARO ALT - Altitude derived from air pressure, has provisions for future pitot icing realism, currently not implemented
  
• VS - Vertical speed derived from barometric altitude
  
• RADIO COMPASS - Compass / ADF combo, ADF channel can be tuned with the keypad
  
• DME - Distance measuring equipment, shows the distance to the tuned NDB for the ADF
  
• AS - Airspeed, pretty standard omnidirectional relative wind speed
  
• RADIO ALT - Radio altitude derived from a combo of distance sensor and fluid meter
  
• ERPM / RRPM - Engine and rotor rpms, currently only rotor rpm is realistic
  
• MAN PRES - Manifold pressure simulation

• Do NOT use control input while landed on the ground other than collective. The flight controls use a custom gyro stabilizer that resists changes to angular speed. The specific form of control loop used has an I term that accumulates independent of difference between setpoint and process. In practice, control input will accumulate when no feedback (or false feedback) is given by the gyroscope. The control assumes the helicopter is in the air at all times, so when the ground gets in the way of a commanded pitch, it will "power through" and accumulate until it measures the requested pitch rate. Hold 6 (plant) to reset the control loops to neutral. When taking off from pitching and rolling helidecks, hold 6 until the moment you attempt to lift off.
  
• The throttle system works on a semi-automatic governor. The engine will automatically hold its rps and resist changes without a specific setpoint. 1 and 2 tell the governor the new target rate-of-change for the rps and thus increased loads on the engine will require some manipulation of the throttle to maintain rotor rpm.
  
• The cockpit is constructed with a bird's nest of half block piston shifts and pivots. If the helicopter spawns and the cockpit looks asymmetrical, respawn and it should correct itself.

• Activate BATT switch on panel
  
• Activate INVERTER to give power to the flight instruments
  
• IGNITION
  
• Hold 3 to crank the starter until the engine fires
  
• Hold 6 for 1-2 seconds to reset the controls to 0,0
  
• Hold 1 to decrease throttle or 2 to increase throttle
  
• When rotor rpm reaches 2-o-clock tick mark on dial, reduce throttle and raise collective gently to lift off of ground
  
• Adjust engine rpm to keep rotor rpm at or beyond 2-o-clock

Pressing 4 in the pilot's seat will activate the on/off input of the cable anchor on the bottom of the fuselage as well as the rope disconnect. While the input is active, the indicator on the instrument panel will flash periodically. If an input is received through the cable, it will be OR'd with the flashing indicator.

The ADF (Automatic Direction Finder) installed on this aircraft will tell you the distance (via the DME gauge on the instrument panel) and direction (via the radio compass) to any transmitting RX antenna within range, that being being 4000m + the range of the transmitting antenna. This includes handheld walkie-talkies and remote controllers, offering a new way to pinpoint locate downed airmen using the same piece of equipment used for communication, though only effective within 4500m unless used with 20km range receiver antennas.

The system uses four antennas plus the communication antenna briefly to determine the maximum range of the transmitting radio, and a technique called quadlateration. If you are interested in the math behind this system, let me know and I will write a guide about it. It's a good way to introduce you to some basic linear algebra concepts.

Operation of the radio systems is pretty simple, the descriptions of the switches and buttons explain their use. The keypad isn't directly connected to any radio, rather the current input is saved when a switch is activated.

Interior lights:

• Cockpit spotlight, cycles between three modes: RED, WHITE, OFF
  
• Cabin domelight

Exterior lights:

• Navigation lights, tap the NAV button on the instrument panel to cycle through five modes: BRT CONSTANT, BRT STROBE, DIM CONSTANT, DIM STROBE, OFF
  
• Anti-collision beacon, hold the NAV button for half a second to toggle the beacon on/off
  
• Landing lights, two spotlights placed at the bottom of the nose cowling, activated by the LANDING LIGHTS switch on the instrument panel

5 will enable the seat's look-relative control mode. This control mode will change w/a/s/d to be relative to your current look angle rather than the helicopter, which has the potential to be helpful when trying to look out of the side window. It can be disorienting at first, but if you can get used to it it can be nice.

I would advise against using this control mode in third person, as it's designed specifically for first person.


If you're having trouble controlling the helicopter, please re-read the IMPORTANT INFORMATION section above and follow the steps described for takeoff.

If you have any questions, please don't hesitate to ask
If you have any feedback, please tell me in the comments and I'll see if I can fix

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