Collective Question?

[Vfrpilotpb]

I hope this question makes sense:-

In most Helicopters the collective lever is there to allow you to increase or decrease your altitude, by pushing down on the lever most Helis that I am aware of will start to descend through the erosion of lift by the blades being fined off or placed into a nil pitch situation.

Do any helicopter have the ability to actually tractor down in other words we have pitch change and power to go up, is there such a thing as reverse or negative pitch change, with power remaining up but craft rapidly going down under power?

Vfr

[bellfest]

Not that I'm aware of mate. Unless the engineers have stuffed up the rigging. Gravity does just fine when you need to return to earth.

[Arm out the window]

I haven't flown them, but I'm pretty sure the Westland Lynx has a negative pitch range to allow them to hold it down on a pitching and rolling deck until they get the lashings on.
Perhaps some pussers would like to elaborate on the accuracy of this?
Re the 'tractoring' down, I can't see that it would ever be necessary or desirable in flight. If you need to descend really quick, collective down and tight high AOB turns works a treat, caution the rotor revs but.

[helimatt]

Might be useful for inverted hovering though:D

[Wunper]

The RN Lynx rotor may be placed in subminimum pitch on the ground/deck.

The collective has a springloaded soft stop detent for minimum pitch which if pushed further down puts the rotor into -Ve pitch.

It is there to press it on the deck of a ship during the cycling time of the Harpoon deck lock device or any time the aircraft is running without the nylon lashings in place.

The rotor makes a dreadful din in this condition as the blade washout becomes washin and the rotor cones downwards. The cyclic has to be properly centered before this is done to prevent fatigue damage to the Rotor head.

I dont think any Lynx pilot has ever been stupid enough to attempt to apply submin pitch in flight , the only possible use in flight is as mentioned in the ealier post to accommodate a grossly mis rigged collective run when Nr is on the low side during autorotation but that will not actually place the blades in submin pitch it will just use the spring loaded arc of the collective travel in the submin range.

W

[Bomber ARIS]

The Wasp (another Royal Navy machine) had the old "negative pitch" ability to which you refer; for the reasons already stated.

[NickLappos]

So too the Skycrane, because the vast weight changes required that much bottom collective in the very light weight autorotation.

[Rotorbee]

Didn't have the BO 105 that Charlie Zimmermann flew negative pitch too? He needed that for flying upside down. Saw that somewhere.
Does anybody have that video?