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This is inspired by a previous question

What would happen if I bank a helicopter then pull hard on the cyclic?

I've seen some pretty radical videos of piloting by Chuck Aaron, but I've not seen a helicopter perform a forward inversion (either by a flip or an inverted loop). I've seen helicopters invert backwards and perform rolls, but not in the forward axis.

Would such a manoeuvre be possible?

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  • $\begingroup$ I bet it's doable, question may be : How big can such a mechanic using rigid rotor head be scaled up? $\endgroup$
    – user21228
    Commented Jan 8, 2018 at 11:44
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    $\begingroup$ Possible duplicate of Why do helicopters not roll over when flying forwards? $\endgroup$
    – Pondlife
    Commented Jan 8, 2018 at 14:45
  • $\begingroup$ I've never seen Chuck do a full loop, from what I've seen he kind of twists out of it which keeps him from completely losing the load on his rotors (though he hits low-g for sure). Helicopters are basically very big pendulums, and when the balance of that pendulum is upset, bad things can happen. But yeah I mean, I think I did something like that in FSX. I know I did a barrel roll in a huey one time that was hilarious $\endgroup$
    – Noah Wood
    Commented Jan 22, 2018 at 9:50
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    $\begingroup$ @NoahWood, whether helicopters are big pendulums depends on the rotor design. Those with teetering rotors are, and don't tolerate unloading the rotor. Rotors with offset hinges and hingeless rotors however do exert torque directly between the fuselage and rotor and can therefore be controlled when the rotor is unloaded. $\endgroup$
    – Jan Hudec
    Commented Sep 12, 2020 at 21:13
  • $\begingroup$ It can be done with a gyro with teetering rotor, but the pilot has to know what he's doing... Has been done: youtube.com/watch?v=V8DxT7771vg $\endgroup$
    – xxavier
    Commented Sep 12, 2020 at 23:37

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Yes. This video at 0:50 shows a heli climbing into a loop, labeled at the top as 1.4 G and 25 knots, so it's still in forward flight when it reaches inverted flight. The view from inside the cabin at 0:58 confirms pitching without rolling.

(At 1:26 the heli does what's labeled as a front flip at low G's, but that includes a lot of roll too.)

The pilot is Aaron Fitzgerald, in a Red Bull helicopter with registration N154EH barely visible at 1:44, identifying it as a 1985 MBB BO105 CBS4, classified "experimental."

Wired magazine describes the crucial "hingeless" rotor head:

The rotor head is milled from a solid block of titanium rather than multiple components, skipping the hinges that typically allow the blades to bounce up and down to absorb aerodynamic forces. Instead, the blades are designed to be more flexible. ... The lack of up and down blade movement at the rotor head limits the “play” in the control stick, giving the pilot more granular control of the helicopter.

The video was published 2019 May 24-25. It is also available without ads here.
I could not determine the exact date of the flight, but Wired also said it was

a practice session for this Memorial Day weekend’s Bethpage Air Show

so that at least confirms it as shortly before 2019 May 27.

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