Best way to quickly descend from high altitude

[Chad Vader]

Hi,

Ive picked up this module in the last few weeks, and im having an issue whereby when I try to descend from reasonably high altitude after going over a mountain, my rotors smash together.

Whats the best way to descend from high altitude without breaking the aircraft or entering VRS?

In the hind I can pitch down to some degree to follow the contour of the mountains but in the KA50 im finding I cant really do that.

Thanks.

[Boosterdog]

Ive always used a combination of dropping the collective and pushing the cyclic for fast terrain following drops.  The Shark will drop like a stone if you wish it to. (within reason). VRS is more easily avoided if you think of the tunbine/rotor relationship as eleastic and apply power earlier than you think you need it. 

[Chump]

Reduce the collective when diving. Watch the rotor pitch indicator on the left forward panel.

[Chad Vader]

HI all, ive tried reducing the collective and diving but i seem to always overspeed and then the rotors smash together.

[Boosterdog]

44 minutes ago, Chad Vader said:

HI all, ive tried reducing the collective and diving but i seem to always overspeed and then the rotors smash together.

I dont think there is a secret method. Its more a case of respecting the physics and limitaions of helos in general and co-axial rotors specifically. 

If its any consolation...

https://www.flightglobal.com/rotor-blade-collision-is-blamed-for-ka-50-crash/22585.article

[Chad Vader]

Tragic but does indeed make me feel better! lol

[Cmptohocah]

On 5/1/2022 at 1:00 PM, Chad Vader said:

Hi,

Ive picked up this module in the last few weeks, and im having an issue whereby when I try to descend from reasonably high altitude after going over a mountain, my rotors smash together.

Whats the best way to descend from high altitude without breaking the aircraft or entering VRS?

In the hind I can pitch down to some degree to follow the contour of the mountains but in the KA50 im finding I cant really do that.

Thanks.

If it helps, there are three conditions for VRS to happen:
1. powered flight
2. vertical speed (for Mi-8 it's around -4m/s and greater)
3. forward velocity less than effective translational lift (for Mi-8 less than 60km/h, I think)

Break any of these and VRS won't happen.

[Volk.]

On 5/1/2022 at 10:59 PM, Boosterdog said:

https://www.flightglobal.com/rotor-blade-collision-is-blamed-for-ka-50-crash/22585.article

That article...is not quite accurate. Wasn't 'standard terrain flight' at all - night flight acrobatics, 2nd flight he'd had in the Ka-50 after an 8 month gap, after doing a sortie the Mi-24. Apparently the maneuvers done weren't signed off by the Kamov team after modeling out the safety of those maneuvers.

But yeah, both cases of extreme maneuvers even for a helo allowed to do loops etc. just can't do like that. So like you say physics.

 

As for the descent - you need to corkscrew usually. As in enough pitch not to increase speed beyond the limits, with whatever descent rate you can (within main rotor rpm limits as Chump mentioned), then keep going lower in gradual circles.

Biggest factor with rotor intersections is probably the collective. If you're going to be doing something super-stressful/acrobatic or touching the speed limits, lower collective, then do whatever you need to do gently.

 

[randomTOTEN]

You don't need to be afraid of VRS when in forward flight and at low power.  Drop the collective fully if you need to.

[M1Combat]

Pay attention to the blade pitch angle, that's all you need to do.  It's above and left of your left knee.  Start your dive.  When you get to about 250 turn blade pitch down to ~3 degrees.  Pay no attention to the flashing red lights.  When you're getting to the bottom of your dive pull out of it and gradually increase blade pitch.  Stay below about 5 degrees or so until you're back below "safe" speeds.  The closer back towards ~275 you get you can turn the blade pitch back up...  but be careful.

 

You don't need to corkscrew unless you have a spot at the bottom of the decent that you don't want to overshoot.

The control inputs that cause blade collision are roll right, rudder right and collective (AKA blade pitch).

 

Also...  Turn off the Alt hold AP channel.  It will try to kill you.  You're welcome.

[Ephedrin]

I wouldn‘t use the AP channels at all if you don‘t want to take your hands off the stick or go very slow, low and search for targets. The Ka50 is extremely easy to fly manually thanks to the counter rotating rotors and VRS, as mentioned above, is no danger at all in forward flight faster than ETL. Vortex Ring State means that you descend into your own downwash but that can‘t happen if you‘re flying forward.
 

Nose down always results in a higher speed, regardless of the aircraft. You need to stay below Vne, again regardless of the aircraft. There is a limit you can dive at, more is not possible, that‘s normal. If you reach the limit and it‘s not enough you reach the limitations of your aircraft and need to adjust the route. It‘s really as simple as that.

[Mr_sukebe]

Just apply more mechanical sympathy.  Don’t overspeed and avoid VRS at low speeds.

 

When I first got the Mi8, I couldn’t understand why I couldn’t do combat landings as I could in the Huey.  The reality is that the real Mi8 can’t do it.  It’s just a case of learning a new set of limits for the aircraft

[M1Combat]

Pay attention to the blade pitch angle, that's all you need to do.  It's above and left of your left knee.  Start your dive.  When you get to about 250 turn blade pitch down to ~3 degrees.  Pay no attention to the flashing red lights.  When you're getting to the bottom of your dive pull out of it and gradually increase blade pitch.  Stay below about 5 degrees or so until you're back below "safe" speeds.  The closer back towards ~275 you get you can turn the blade pitch back up...  but be careful.

[Krez]

I have been flying he KA-50 for a few years now and I have never gotten into VRS. Out of all of the helicopters, the KA-50 I think is the most forgiving when it comes to VRS. The Hind on the other hand is another story.

[AeriaGloria]

I’m surprised no one said autorotation or letting there be up flow through the rotor system. Going low on the collective is fine, but you can full on put it at minimum, if you go too fast just nose up, control speed with cyclic like autorotation. 

[Krez]

When I'm in the KA-50, I rarely find myself above treetop level.

 

[3WA]

When I power dive, I flatten the collective and pitch the nose down.  When I reach near where I want to be, I slowly pitch the nose up and slowly pull up on the collective, cutting my blades into the wind.  If you bring the collective up too fast, you'll tear your blades off.

With the blades flattened, the rotors act like a wing, letting you glide down.

[Fastbreak]

On 6/14/2022 at 3:55 AM, 3WA said:

When I power dive, I flatten the collective and pitch the nose down.  When I reach near where I want to be, I slowly pitch the nose up and slowly pull up on the collective, cutting my blades into the wind.  If you bring the collective up too fast, you'll tear your blades off.

With the blades flattened, the rotors act like a wing, letting you glide down.

"I am a leaf on the wind. Watch how I soar!"