Some helicopters have wheels whereas others have skids. While skid gear is always fixed, wheels can either be fixed or retractable.
As one isn’t necessarily better than the other, the type of landing gear used really comes down to the primary use of the helicopter, with the tradeoff being between savings in both weight and cost, and utility and convenience.
Why Do Some Helicopters Have Wheels?
Helicopters with wheels that can be retracted are better at reducing drag and can therefore reach higher cruise speeds.
Depending on the primary use of the helicopter, for those times where getting from A to B as quickly as possible is key, a helicopter with wheels is clearly the better choice. This is why helicopters used for medevac are fitted with wheels.
Helicopters that are fitted with wheels are much better suited to taxiing for the simple reason that maneuvering a helicopter on the ground is much easier. Compare this to a helicopter with skids that needs to hover off the ground (air taxiing) that will also produce more rotor downwash, and pose more of a danger to passengers and other aircraft along the taxiway.
Skid helicopters require dollies and tow carts for ground handling, which isn’t exactly convenient, though in the case of a very small helicopter (such as the Robinson), ground handling wheels can be attached to the skids, requiring just one person to move the helicopter around.
Why Do Some Helicopters Have Skids?
Lower Maintenance Costs
Helicopters fitted with skids require much less maintenance than helicopters fitted with wheels. This is due to wheels having far more moving parts, including the tires, bushings, bearings, and actuators that all require at the very least inspection and eventually replacement. This costs both time and money.
If a pilot will regularly be landing on rough, uneven surfaces like grass, and swamps then skids are undoubtedly the better choice. This is down to the weight of the helicopter being spread over a larger surface area that prevents it from sinking into the ground. Helicopters with wheels are better suited for landing on more solid, even ground.