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Semi-rigid (teetering): two blades fixed to a hub that teeter as a unit — they can flap and feather but cannot lead/lag. Used on the R22 and R44. Simpler and lighter, but more susceptible to mast-bumping during low-G maneuvers. Fully articulated: each blade flaps, leads/lags, and feathers independently via separate hinges. Used on three- and four-blade systems (Bell 206, R44 four-blade, etc.). More complex and heavier, but absorbs vibration better and can suffer ground resonance — semi-rigid systems cannot.

US helicopters typically have a counter-clockwise (CCW) main rotor when viewed from above. Adding power applies more torque to the main rotor, which tries to rotate the fuselage in the opposite direction (clockwise, or nose-right) by Newton's third law. The tail rotor produces leftward thrust to counteract this — adding power means more torque means more tail rotor thrust required, which is right pedal input.

DA (Decision Altitude) is used on precision approaches — momentary descent below DA is acceptable during the missed approach if the visual references aren't established. MDA (Minimum Descent Altitude) is used on non-precision approaches and is a hard floor: you cannot descend below MDA without the required visibility and runway environment in sight. In short: DA is a decision point, MDA is a hard limit.

Only with SFAR 73 endorsements. A standard PPL Helicopter certificate authorizes most helicopters under 12,500 lbs — but the R22 and R44 are governed by SFAR No. 73, which requires ground training and a logbook endorsement before you may manipulate the controls for flight, not merely before acting as PIC. The SFAR reaches manipulating the controls, acting as PIC, giving ground or flight training, and conducting a flight review. Acting as PIC additionally requires either 200 flight hours in helicopters with 50 in that model, or the 10-hour training endorsement — and on the endorsement route, a recurrent flight review in the same model every 12 calendar months.

Two big ones. (1) 14 CFR 91.155(b)(1): in Class G below 1,200 AGL a helicopter may operate clear of clouds at ½ SM flight visibility, but only in an airport traffic pattern within ½ mile of the runway or helipad of intended landing. No day/night split, no see-and-avoid speed condition — that was the pre-2014 wording14 CFR 91.157 (Special VFR): helicopters can operate SVFR with no minimum visibility requirement, while fixed-wing requires 1 SM. (3) For IFR approaches, AIM 10-1-2 lets helicopters reduce the published Cat A visibility to half (or 1/4 SM / 1,200 RVR, whichever is greater).

They do — when the chart depicts one and SHARPTT doesn't apply, the same rules apply. But the helicopter community uses approaches more frequently with radar vectors or copter-specific approach plates that often eliminate procedure turns entirely. The 45/180, 80/260, and teardrop are the same; the difference is mostly in how often you actually fly one in operational helicopter IFR.

It's the autorotation technique used in IMC or at night when you can't see the ground in time to time the flare. Set a slightly lower-than-normal airspeed (~35–40 KIAS plus half the windspeed) and maintain that attitude all the way down — feed in collective slowly when the ground starts to make itself known, and accept the slight forward speed at touchdown. Do not flare — there isn't enough kinetic energy at the lower airspeed to change the flight path.

Carburetor heat introduces hot air, which is less dense than cold air. The carb cannot meter the same air mass at the same throttle position — effectively, the mixture richens and the engine produces slightly less power. The RPM drop is also a quick check that the carb heat is functioning; if the RPM doesn't drop, the carb heat may not be plumbed correctly. In a piston helicopter with a correlator/governor, the system compensates and the drop is small or absent.