A barrel-roll-loop!

[Belphe]

Hi,

 

I was playing with my shark yesterday :megalol: and tried to perform something that seemed to be a mix of a barrel-roll and a loop. I climbed high in vertical, sped up to ~230 IAS and levelled up maintaining the speed with ~40% collective. I gently pulled the cyclic and started to roll right. The chopper went 50 degrees nose up and shortly after was flipped upside down (as I was still rolling). The manouver lacked a proper finish and I had to "save" myself with rough and aggresive steering but it all ended well and the barrel-loop as I called it was performed without loosing my rotor blades. :smartass:

 

However, I never managed to repeat this... :cry: I've no idea why. Everytime I am upside-down in the middle of the maneouvre and start falling down I get my blades torn apart. I know why! It's just I don't know how to prevent them from hitting each other. Could you guys give me any clues on how to perform this trick? How to make it at the right speed, alt and tempo so it looks smooth and is safe? Perhaps I should try rolling left instead of right, perhaps I should idle the collective while being upside-down? Please, elaborate! :book:

 

Thanks!

[Yo-Yo]

The first thing I can recommend is to use autopilot director mode to be sure there is no uncontrollable input from AP especially in rudder channel.

If you perform this maneuver gently you have good chances to keep you blades intake.

You can lower collective but I think it's not vital.

[Yskonyn]

A good barrel roll remains at or extremely close to 1g for the whole procedure. I don't know if you have sufficient control range to perform a barrel roll in the Shark, (after all it's not a fighter, nor an acrobat ) but if you do then a well executed maneuver wouldn't damage your rotors.

[EtherealN]

TBH man, it is an acrobat. :P

 

A good key to avoiding a rotor intersection when doing inversions and such that has worked relatively well for me (I still die occassionally and definitely wouldn't be doing what I'm doing if I was flying a real Ka-50...) is to first of all plan your airspeed (not too high and not too low) and plan the maneuvers to happen leftwards - and try to ensure that they won't force you to use too much rudder when exiting the maneuver.

 

I'll see if I can replicate your maneuver, seemed like fun. :)

[EtherealN]

I think I actually may have replicated that maneuver. :D

 

I did it mostly to the left though, and to make a clean exit I allowed it to go out of the maneuver perpendiclar to my original direction of flight. That seemed to allow me to have a very smooth rudder and cyclic input.

 

...then I died from excessive speed and right rudder during level flight when trimming. :P

 

I did save the track file (flew with that control indicator box thingie just for those purposes), let me know if you want it.

[Yskonyn]

How would left be more safe than right? The rotors rotate to counter eachother so it shouldn't really matter, should it?

 

Is the KA-50 licensed for acrobatic maneuvers? Could you name some?

[EtherealN]

Well, I don't know if it's licensed for acrobatics, I just meant that as far as helicopters in general go it certainly is an acrobat. Though for a helicopter this still doesn't make it better at acrobatics than the soaring trainer we have down at the club. :P

 

As for left and right, basically, the lower rotor flares up more than the upper one due to being in the upper one's downwash. When you then apply rudder controls, the rotor discs basically get a differential collective on them - for left rudder the upper disc gets an increased angle of attack (increasing torque) and the lower has decreased angle of attack (decreasing torque, total lift remains the same). In the case of right rudder, it's the lower disc that gets increased angle of attack, causing it to go upwards from an already high position, whereas the upper gets less angle of attack, causing it to droop low.

 

If you want to test it, take your chopper and speed it up to 300kph, then apply full left rudder. You should survive. Then repeat the maneuver and suddenly apply full right rudder. Most likely, you're now falling out of the sky. (Note however that the velocities where this happens varies with air pressure, temperature and humidity.)

 

EDIT: Oh, and if you want to be absolutely guaranteed to die, when at 300kph, apply both full right cyclic and right rudder. :D

Edited April 7, 2009 by EtherealN

[Jonay]

Acrobat= Gymnast (an athlete who performs acts requiring skill and agility and coordination)

 

so unless your Ka-50 is swinging from cloud to cloud I think you mean

 

Aerobat= an airplane perfoming maneuvers not necessary for normal flight, but used in air show, competition, or combat flying. Some example maneuvers would be loops, rolls ...

 

The Ka-50 will not in real life perform any of these maneuvers that you are discussing as the rotor head is not rigid. The articulated rotor head will not support the forces and strains that the hinged blades will go through during the maneuver.

 

The BO-105 and Westland Lynx are 2 examples of Helos that can perfom Aerobats due to the ridged or semi-ridged rotor head, where the blades are attached onto the rotor mast directly, the rotor mast is normally made of titanium in these instances.

[Yskonyn]

Yes Jonay, that's why I doubt the KA-50 is certified for aerobatic maneuvers and therefore non-aerobatic. ;) Don't be a smart-ass though. You knew we were talking about aerobatics, didn't you? ;)

 

Thanks for the clarification Ethereal, much appreciated! What's the max maneuvering speeds with full control deflection do you know that?

Edited April 7, 2009 by Yskonyn

[EtherealN]

Yeah yeah, if you're going to be a linguistic perfectionist I'll call it aerobics. :P

 

As for the articulated rotor head, cold you source this? I have seen the real Ka-50 perform loopings.

EDIT: I might have to back out of that - I haven't been able to find the same video again, but I've seen videos where it looks like a loop but on closer inspection might be an optical illusion.

 

---

 

Yskonyn, not certain of that unfortunately. From what I've understood it varies greatly with atmospheric conditions.

Edited April 7, 2009 by EtherealN

[Yskonyn]

Yeah yeah, if you're going to be a linguistic perfectionist I'll call it aerobics. :P

 

As for the articulated rotor head, cold you source this? I have seen the real Ka-50 perform loopings.

 

---

 

Yskonyn, not certain of that unfortunately. From what I've understood it varies greatly with atmospheric conditions.

 

That's why there's something called Indicated Airspeed. ;)

If you convert that to Calibrated Airspeed (corrected for intrument error and position error) that speed should always be the same to pull off maneuvers because of the correction.

Edited April 7, 2009 by Yskonyn

[Jonay]

Sorry, I used to call my flying club's 152 an acrobat when i first joined it.. just out of habbit ive corrected people like i was! :P

 

Acutally now that i think about it, I remember that the Ka-50 has shorter blades than other semi articulated rotors,so less strain is put on and also it doesn't have stubs like the AH-64 does.. it has wings which provide lift..

 

So totally going back on myself, the Ka-50 should be able to perform these, but not at the same rate a Lynx or BO-105 can. (these two examples can "backflip" from a hover, and have a high roll rate)

 

The Ka-50 would have to have a minimum speed at which it can perform the maneuver. The wings would have to be providing enough lift for it to go inverted without it putting too much strain on the rotor head, it would also have to have much wider turning circle becuase of this too.

 

eg, profile of a Lynx loop /barrelroll = o

profile of a Ka-50 loop/barrelroll = O

 

Sorry if i came across i bit snotty, no harm intended! :D

[Yskonyn]

No problem! ;) I was just teasing you as well.

I have absolutely 0 knowledge of helo's and their aerodynamic characteristics so you could fool me into anything regarding that matter. ;) I am a 'fixed winger'.

 

In one of the overview training missions you're being told that the stub wings provide weapon hardpoints as well as additional lift.

I am rather curious how much positive lift these small wings provide to add to overall maneuverability.

I can imagine there's lots of turbulence interference coming from the downwash of the rotors on top of the wings harming the airflow over them from the forward speed of the helo in level flight.

[EtherealN]

Aye Yskonyn, but unfortunately I don't think the Ka-50 does those conversions.

 

And no worries Jonay, I'm as guilty of bitching at people's terminology myself - though in my case it's usually IT-related since it is only relatively recently that I started flying IRL.

 

--

 

On how much lift the wings generate, I don't know any exact numbers, but if you've played the mission "Over on the other side" (or whatever it was called, in the Deployment campaign) you'll have noticed that you don't get over the peak if you try gaining the last altitude while in a hover - but it's very easy if you are at the optimal climb speed of 130 IAS.

Edited April 7, 2009 by EtherealN

[Yskonyn]

Right you are Ethereal. There's no CAS selector knob in the KA-50, but a bit of calculating can easily transform IAS into CAS. You do have IAS, don't you, or does the KA-50 correct for wind and show groundspeed in the hud? That would be weird because the only 'performance indicator' you have, while flying, is IAS or CAS. As for certification EAS is mostly used:

http://en.wikipedia.org/wiki/Calibrated_airspeed

 

As you told us you're a wikipedia nut I thought you might like this. ;)

Edited April 7, 2009 by Yskonyn

[EtherealN]

the HUD shows groundspeed, which it gains from a doppler sitting on the tail boom.

 

The Shkval shows indicated airspeed, though, as does the analog left of the Shkval.

[Yskonyn]

So much for reading my flight manual, I guess. ;)

So the Shkval is the instrument to watch while doing maneuvers then as is the analog IAS indicator in the cockpit.

 

Is there a way to alter the speed indication on the HUD, like, for example, you can do in the F-16?

[EtherealN]

Depends, I guess. Most of the time when I go for some pure joyrides (often ending in death) I have zero wind, so the ground speed works well then. :D

[Yskonyn]

Yeah but if you make it a habit to abide by the HUD speed to pull of tricks you're bound to die on a bad day during a mission. :)

[Yskonyn]

(...)but it's very easy if you are at the optimal climb speed of 130 IAS.

 

Just make sure you don't look at the HUD to get to that 130 kts is the morale of the story about now. At least not on a windy day. :P

[EtherealN]

Indeed. :)

 

Btw, a very nice video of the Ka-50 doing maneuvers: http://www.patricksaviation.com/videos/Force_Feedback/485/

[Yskonyn]

Rep inbound! very nice share, thanks!

 

I am stunned to see the stable control on the yaw axis. I tend to jiggle a lot in the sim and find it difficult to stay solidly pointed at a given object, for example.

[EtherealN]

Aye.

 

Also, keep your eyeballs on the stick and watch him trim that beast. :D

[Heiliger Bimbam]

Yeah, barrel rolls are fun. Uploaded a short vid on youtube. The first roll is nice, the second is ...

 

http://www.youtube.com/watch?v=47ImxzXy8EA

 

:pilotfly:

 

Edit: Only the HQ Vid works. Dunno why the standart is broken.

Edited April 7, 2009 by Heiliger Bimbam

[Belphe]

I am rather curious how much positive lift these small wings provide to add to overall maneuverability.

I can imagine there's lots of turbulence interference coming from the downwash of the rotors on top of the wings harming the airflow over them from the forward speed of the helo in level flight.

 

I think that at speeds that actually make the wings produce a significant amount of lift the rotor stream (downwash) actually disturbs a very small part of the airflow or doesn't disturb it at all... We're talking 150 km/h and more. At slower speeds the wings don't produce any force that could help in such manoeuvres so the downwash can disturb them as much as it wants... :thumbup: