Helicopters with wheels

Why do some helicopters…especially the big ones… have wheels instead of a pair of flat skids like that on familiar news choppers which report on traffic?

Its not like they need to taxi down a runway or anything.

The wheels make it easier to roll the landed copter into the hangar for storage and maintenance, possibly towing it with a small truck. The smaller copters can be lifted using a special handcart which I can easily imagine being impractical for the big birds.

I’ve taxied in helicopters on many occasions. If you need to get from a hangar or a departure area to a runway (common if you take off from a commercial airport), having wheels saves a lot of fuel. Similarly, being able to do a rolling take off improves the gas mileage.

So maybe the question should be rephrased:

Why don’t smaller helicopters have wheels?

My WAG is that the skids are just simpler, cheaper and especially more aerodynamic than fixed wheels. (And much simpler than retractable wheels.) Also I’d imagine that you want the helicopter to stay put when it lands, so you’d also need brakes if you had wheels.

Wheeled helicopters can perform “roll-on landings” in the event of mechanical difficulty. Hueys and skidded types perform a similar maneuver, but with a bit more drama. Wheels are not generally retractable, but fixed. They even have brakes and it is vital to ensure the parking brake is set OFF. These differences led to a certain joke between Huey and Black Hawk crews. “Trikes are for tykes” versus “Skids are for kids.” har har.

I recall asking, many years back, why helos often took off in a slow forward pattern, gaining altitude slowly. I was told it was much safer, and less stressful on the aircraft, than a verticle takeoff.

Rolling takeoffs use much less fuel, too. Some higher-speed machines do have retractable gear. The drag reduction isn’t worth the weight and cost on slower aircraft, though. Just like with fixed wings.

Helicopters with skids do use ground-installed caster wheels for ground movements.

I flew in a russian MI-8 once in Angola. IIRC they can’t take off without a rolling start as I remember we brushed the top of the trees adjacent to the helipad as the ‘runway’ was too short…

The main reason for a rolling takeoff though is that if you are power limited (the helo is heavy, it’s hot, high alititude), a rolling takeoff into the wind uses much less power than a straight takeoff would.

And I’m seconding the above in regards to a rollon landing if they’re having mechanical difficulites. There are numerous emergency procedures that require roll-on landings. You do those if you need to maintain forward airspeed in order to keep falling from the sky or to keep the aircraft from flipping over because of the torque of the main rotor head.

All I know about helicoptersI got from this book. In it the author tells about how, with a heavy load, a helo needs to move forward out of its own downwash to gain more lift.

As we used to say in flight school, “Skids are for kids!”

Also lighter, which is an important factor with most aircraft, especially small ones like a Robinson R-22.

I’ve done ‘roll-on’ landings in a Robinson. I can’t seem to remember doing any in a Schweizer. Keep the skids level and straight and there shouldn’t be any drama. This maneuver is useful if you need to land in an area of higher density altitude where you don’t have the power to perform a normoal hover landing. I’ve also done a ‘running take-off’. Again, this can be used if you can’t perform a normal take-off because of high weight or density altitude. Taking off or landing on grass isn’t too bad, but I hate the grinding when on asphalt. (If the instructor says to do a running landing on a runway, you do a running landing on a runway. The skids have replaceable ‘shoes’, BTW.)

Have a look at the Height-Velocity Diagram. I haven’t read the article, but there’s an image of the diagram. Basically: Aircraft have performance envelopes. One part of the envelope for helicopters is the set of conditions from which the pilot can successfully perform an autorotation in the event of a power or mechanical failure. If the helicopter is below a certain altitude and below a certain airspeed, or below a certain altitude and above a certain airspeed, then recovery will not be possible. In a low-altitude, low-speed autorotation there mightn’t be enough room to enter the autorotation and cushion the landing. (A well-executed autorotation landing should be as smooth as any landing.) In a low-altitude, high-speed situation the pilot might not have enough time to enter autorotation before he hits the ground. But flying within the envelope allows the pilot to enter autorotation and land safely.

In training we operated outside of the envelope on occasion; for example, when taking off from an area with obstructions. The instructor advised that this was a calculated risk. The conditions would allow us to perform the maneuver as long as we didn’t have a mechanical failure, and such failures are extremely rare. So odds were that we’d be successful. But I was advised to always try to fly within the Height-Velocity Diagram if I possibly could, and to only fly outside of its boundaries after weighing all of the factors. The Height-Velocity Diagram is also called ‘The Dead Man’s Curve’.

Edit: Fixed coding. First post out of bed, caffeine deficiency, etc.