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HL-3 Valve Time - A coal-fired helicopter

An airworthy coal-fired helicopter. Didn't expect to get one done day one, but it flies! Stabilized and flyable (as long as you don't mind waiting 5 minutes for your helicopter to pre-heat). Now also features steampunk-themed avionics.

Operation:
WSAD Cyclic, arrowkey collective. Collective stabilization is of the altitude hold variety, like my other helos. Allow the boiler pressure to top off and the rotor to achieve somewhere over 70 RPS. Try to maintain an RPS greater than about 65-70 while in flight (avoid starting too early, or placing excessive stress on the collective) as the system will stall and start to cool down irrevocably. Sometimes this can be salvaged if you relight the boiler, but seems avoidable as long as you don't let it drop too low.
Edit: There seem to have been some buffs to steam turbines since I made this post. Careful RPS management is no longer as necessary.

If spooled higher, the higher number will be maintained for a long time, but will diminish over the course of the flight at about 1 rps every 15 or so seconds in straight and level flight. RPS appears to bottom out in the mid to high 40s to low 50s, but steam turbines are temperamental. Your milage may vary, especially if you're putting a lot of stress on the turbine by way of the collective with high angles of attack. It is possible to stall the turbine if the collective remains high for long enough, so sustained pitching attitudes under 45 degrees are recommended.