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Helicopters with wheels can take-off and land in a level or nose-up attitude (nose wheel off with main wheels on the ground). For example, the pilot of a VIP helicopter might want to take-off in a level attitude for max comfort of the passengers (some nose down will eventually be needed though for acceleration).

Per the above, is there a preferred attitude for take-off and landing of helicopters with wheels or is the attitude only based on performance and design parameters such as CG location, rotor downwash on aft fuselage, rotor mast angle, etc.?

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    $\begingroup$ Inverted attitude take-offs are generally frowned upon $\endgroup$
    – U_flow
    Commented Apr 24 at 13:07
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    $\begingroup$ Don't forget inverted landing. $\endgroup$ Commented Apr 24 at 19:53

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Helicopters with wheels tend to be the heavier ones, whose downwash while hovering near the ground is strong enough to be dangerous ("goes out and up hundreds of feet and can easily overturn parked aircraft"), says a blurb offering wheeled tugs for skidded craft.

So when taking off or landing, the longer you stay in translational lift, the briefer you need that dangerous full hover power. That argues for nose down soon after takeoff, or even where possible a rolling takeoff like a gyrocopter. Similarly when landing, prefer a rollout ("two-point landing" on the rear wheels), or at least not a long purely vertical descent.

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  • $\begingroup$ Thanks a lot Camille, just a quick question to clarify; when downwash is an issue, nose up first at take-off and main wheels down first at landing right? $\endgroup$ Commented Apr 25 at 8:28
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    $\begingroup$ For forward flight (so you can see where you're going), at takeoff nose down as soon as possible to quickly reach translational lift. At landing, nose up aka main wheels touch first, to stay longer in translational lift. $\endgroup$ Commented Apr 25 at 16:33
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In a conventional helicopter (main rotor plus tail rotor) the main rotor is normally tilted some 3 to 5° forward. This is done in order to give the thrust a forward component which partially counteracts the aerodynamic drag encountered during level flight. In this way the main rotor mast is relieved of some structural stress.

The attitude of the fuselage is normally chosen in such a way that in level flight it is horizontal. That means that the main rotor mast is not perpendicular with the floor but at some 85 to 87°.

When designing the landing gears then two choices arise:

  1. either you set the floor parallel to the ground - and therefore the main rotor mast remains tilted forward 3 to 5°; or
  2. you set the main rotor disk parallel to the ground - and therefore the floor remains tilted backward 3 to 5°.

If you select the option 1. then at takeoff as soon as the main rotor starts generating enough thrust to lift the helicopter, the forward component of the thrust (due to the 3 to 5° forward tilting) starts to push the helicopter forward: if you have skids, this forward sliding would obviously generate a lot of scary sparks and uncomfortable screech... That's why any helicopter with skids is built according to the solution 2.: on ground the mast (and the thrust) is perpendicular to the ground and the floor is tilted backward a couple of degrees. The H145 is a good example of that (picture source, plus a couple of lines from my side):

enter image description here

If your helicopter has landing gear with wheels, then solution 1. is convenient: being the main rotor tilted forward, as soon as thrust is generated the forward component pushes the helicopter forward giving it the possibility to move along the landing field.

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    $\begingroup$ That's not what I was after sophit but thanks for the detailed reply that had very useful info! $\endgroup$ Commented Apr 25 at 9:04
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The second part of your question is more correct. The pilot doesn’t “choose” a fuselage attitude by rocking the aircraft forward or back under the rotor. There isn’t a control that does that.

As the pilot picks up, the weight of the aircraft transitions from the landing gear (whether skids or wheels) to the rotor disk. So sitting on the ground, the attitude of the fuselage is whatever the lander gear configuration dictates. And once picked up, the fuselage hangs under the rotor mast at whatever angle its fairly narrow CG range dictates. The pilot doesn’t “select” or control the fuselage attitude.

The control inputs the pilot has is to move the cyclic forward… which increases the lift in the back of the rotor disk, which necessarily moves the helicopter forward over the ground. If continued this will gradually tip the fuselage forward, as it is a pendulum hanging under the disk that is now accelerating forward.

If the pilot pulls back on the cyclic, it increases the lift at the front of the rotor disk, which tips the rotor disk backward, which begins movement to the rear. Again if continued, the fuselage will gradually start to tip back, as a pendulum would.

But the fuselage angle is just a natural torsional and aerodynamic consequence of the changing rotor angle. The fuselage will naturally lean or tip into the direction of movement, and the pilot is controlling the movement, not the fuselage deck angle.

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