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Sikorsky X2 snatches Lynx's speed record

Birdog8585

Birdog8585

Milk and Honey
pilot
Contributor
Sikorsky's X2 Demonstrator has just reached 225kts surpassing the Westland Lynx's record of 216kts set in 1986. STORY.

x2.jpg


and then...

X2_attack.jpg


...damn bell mafia...
 
phrogpilot73 said:
Maybe because it's a requirement?? The AH-1W Cobra can carry the AIM-9, and I'd be willing to be the AH-1Z probably is capable of it, too...
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You do realize that was mostly in jest right?

But still 400 lbs is a lot of On station time I could be giving a ground commander just for an ability that is pretty arguably useless given that we've never operated helicopters without Air Superiority.
 
We're still waiting for the Ka-50s to show up for the helo-to-helo dogfights.

The Z has AIM-9 as well. For as rare/nonexistent as helo air-to-air is, I'd think helo-mounted Stingers would answer the mail.
 
That's pretty sweet until they hang stub wings on it and attach a gun up front, then the top speed is about 160-ish.
 
Doesn't retreating blade stall come into play at those airspeeds? What effect does that have with the axial rotor system?
 
The idea behind the X2 is that the counterrotating rotors only produce lift when advancing; I assume they are reduced or flat pitch when retreating. At least that was the idea for the advancing blade concept. The wired article talks some weirdness about slowing Nr to increase the retreating blades airspeed.
 
phrogdriver said:
We're still waiting for the Ka-50s to show up for the helo-to-helo dogfights.

The Z has AIM-9 as well. For as rare/nonexistent as helo air-to-air is, I'd think helo-mounted Stingers would answer the mail.
Click to expand...

While they were airframe tested and wired for the Alpha model 64 we don't carry (and thanks to the CMWS mod can't carry) Stingers on the Longbow. However... RF Hellfires are capable of Air to Air shots.


Flugelman said:
Doesn't retreating blade stall come into play at those airspeeds? What effect does that have with the axial rotor system?
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Retreating blade stall is basically a growth of the "No Lift Area" on the retreating blade side of the rotor system. Eventually what small area of the retreating blade is still creating lift and control imputs are not enough to effect the dissimilarity in lift being created by the advancing side. It'd be like as a fixed wing airplane's speed increased if somehow you could make the right wing span increase while the left wing decreased (opposite wing sides for Euro helicopters). By Using a Coaxial Rotor system you negate this. You also save on the parasite effect of a tail rotor stealing torque away from the aircraft. This is especially critical at the high power settings we use when we are hot high and heavy. You can over torque the aircraft simply by letting the aircraft get into a high yaw rate where the sudden use of tail rotor authority to arrest the rate creates a transient torque increase and goes above the aircraft limits. However you pay for this by adding the weight of an additional rotor system which creates its own set of issues such as weight, drag, complexity, etc. The KA-50 for all its lauded ability is a very heavy helicopter without nearly the payload of similar weight class attack helicopters.

Bleeding edge speed with attack helicopters is often much more effected by flat plate drag than by the rotor system going into retreating blade stall. The only way Im gonna see Vne in an Apache carrying an FCR and a respectable load is to put the aircraft into a steep dive.
 
Flugelman said:
Doesn't retreating blade stall come into play at those airspeeds? What effect does that have with the axial rotor system?
Click to expand...

When I talked to one of the Sikorsky engineers about this at an NHA conference, he said that when the aircraft moves towards higher forward airspeeds, the rotor system transitions to just creating lift, and the pusher prop in the back takes care of thrust. When you get into the envelope where blade stall on the main rotor head would be an issue, the speed on the head is reduced, which negates (some of) the effects of retreating blade stall.

In simple terms, to go really fast (in helo terms) you push from the back, and the only demand on the main rotor head becomes lift.
 
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