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Slope Operations

Landing or taking off on sloped terrain — anything from a 5° tilt at a helipad to a 15° landing on uneven ground. The technique is simple in principle: uphill skid touches first on landing; downhill skid lifts first on takeoff. The technique is unforgiving in execution because slope ops are the leading cause of dynamic rollover. Once the lateral cyclic hits the stop, you have less than a second to decide.

Slope landing — sequence

  1. Approach into the slope — face the helicopter into the slope when possible (nose up the hill). This minimizes lateral forces and gives the best escape route on go-around.
  2. Establish a stable hover — adjacent to the touchdown spot, at normal hover height.
  3. Slowly lower the uphill skid — using gentle collective reduction. The uphill skid contacts the surface first.
  4. Apply cyclic toward the slope — into the hill — to keep the rotor disc level (relative to the horizon, not the ground). This counters the helicopter's tendency to drift downhill.
  5. Continue lowering collective slowly — the downhill skid descends toward the surface. As it does, you'll need progressively more cyclic into the slope to keep the disc level.
  6. Both skids on the ground — collective fully down. Pause to verify stability before relaxing controls.

If at any point the cyclic reaches its limit before both skids are down: go around. Smoothly raise collective, return to a hover, reposition. Don't try to force it — that's how dynamic rollover happens.

Slope takeoff — sequence (reverse)

  1. Cyclic into the slope — start with cyclic deflected toward the uphill side, the same position you'd need to hold a level disc on the ground.
  2. Smoothly raise collective — the downhill skid lifts first.
  3. As the helicopter lightens, gradually neutralize the cyclic — by the time the uphill skid is also airborne, the cyclic should be nearly centered.
  4. Stable hover — verify control margin and aircraft level, then transition to forward flight as normal.

The takeoff is essentially the landing sequence run backward: downhill skid lifts first, cyclic deflection decreases as the aircraft becomes airborne.

Why this is dangerous — dynamic rollover

Dynamic rollover happens when one skid acts as a pivot point and the helicopter rotates around it laterally. Once the rolling motion exceeds the cyclic's authority to counter it, the helicopter will continue rolling until the rotor strikes the ground.

Three conditions must all be present:

Slope operations satisfy condition 1 by definition. Slow, deliberate, smooth control inputs prevent conditions 2 and 3. Rushed inputs invite dynamic rollover.

Slope limits

Most training helicopters have a published slope limit, typically:

Beyond that limit, you can't keep the disc level with cyclic alone. Don't operate on slopes you don't know the limit for. Don't operate on slopes near the limit without margin.

Wind compounds slope. A 10° slope with a 15-kt downhill wind is more demanding than a 12° slope with no wind, because the wind adds a lateral component that further consumes cyclic margin.

Avoiding the rotor disc strike

On a slope, the rotor disc is closer to the ground on the uphill side than on level terrain. Several things make this worse:

Always survey the uphill side before committing. If the rotor disc would come within a foot or two of the slope when leveled, find a different spot.

Common mistakes