Help needed for blade intersection avoidance

[mbolan]

Eagle states 'model produces natural helicopter dynamics such as ...“vortex ring” phenomena, airflow stall from the blades, blades intersection (collision)'.

 

I've been struggling to fly this fabulous program in sim mode and even with what I regard as modest flight inputs when turning, jinking or avoiding Shilka hits etc., I'm experiencing 'blade intersection' which means that the rotors suddenly hit each other and fly off in pieces in flight. This is catastrophic and usually involves my untimely death.

 

Does anyone know what I have to do to avoid this catastrophic result?

 

I flew Longbow for years but it only has a single rotor disk so this cannot happen.

 

As it stands the KA 50 should be known as the widowmaker as I seem to get no warnings, nor is there a big red section in the manual telling me how to avoid this phenomenon. It's so dangerous and so prevalent that it really needs to be up-front I'd have thought. Surely KA 50 pilots don't need to behave like bus drivers to avoid this do they?

 

A track file of the 'Shooting Range' mission showing the problem at the end of the file (about 7 mins into the mission) is typical.

 

All help greatly appreciated.

 

System is

 

English DCS BS 1.0 set on simulation

Win XP Home SP3

AMD 3700 1 Mb 2 Ghz

4 Gb DDR RAM

nVidia 9800 GT 1 Gb

What caused the crash.trk

[CAT_101st]

I will look at the trk file and get back to you

[EtherealN]

First of all - don't fly too fast. It is possible to get to speeds of 350km/h plus but generally speaking 300km/h is the limit of where you want to be. In certain atmospheric conditions, less. (Refer to the table on the left side of your cockpit.) Overspeed warning is a loud, high-pitch beeping sound. Whenever you heard that - SLOW DOWN FAST.

 

Secondly, the biggest danger is in banking right and/or giving right rudder. At low speeds this isn't usually a problem, but if you are doing something like 250km/h and suddenly slam your cyclic and pedals to the right you will die. Left is better in those cases.

 

Aside from those basics, I'll check out your track in a moment.

[WynnTTr]

Eagle states 'model produces natural helicopter dynamics such as ...“vortex ring” phenomena, airflow stall from the blades, blades intersection (collision)'.

 

I've been struggling to fly this fabulous program in sim mode and even with what I regard as modest flight inputs when turning, jinking or avoiding Shilka hits etc., I'm experiencing 'blade intersection' which means that the rotors suddenly hit each other and fly off in pieces in flight. This is catastrophic and usually involves my untimely death.

 

Does anyone know what I have to do to avoid this catastrophic result?

 

I flew Longbow for years but it only has a single rotor disk so this cannot happen.

 

As it stands the KA 50 should be known as the widowmaker as I seem to get no warnings, nor is there a big red section in the manual telling me how to avoid this phenomenon. It's so dangerous and so prevalent that it really needs to be up-front I'd have thought. Surely KA 50 pilots don't need to behave like bus drivers to avoid this do they?

 

A track file of the 'Shooting Range' mission showing the problem at the end of the file (about 7 mins into the mission) is typical.

 

All help greatly appreciated.

 

System is

 

English DCS BS 1.0 set on simulation

Win XP Home SP3

AMD 3700 1 Mb 2 Ghz

4 Gb DDR RAM

nVidia 9800 GT 1 Gb

Ah the memories.... I think we all used to have that problem starting out. I remember cussing the BS and thinking what a pos it was to fly. Now, it's like driving a car and I can't remember the last time I've had a rotor clash.

 

My problem was that I wasn't checking where my rudder position was. If you have too much right rudder, combined with high speeds and particularly if you're turning right, your blades will clash.

Use the Rctrl-Enter tool to see the position of your rudder and cyclic. This helped me greatly in gauging when a rotor clash might happen. Now I can fly without the tool just by the 'feel' of the helicopter.

[mbolan]

OK thanks, I'll check that out. At my stage of learning it's hard to believe that I'll get the hang of not crashing this beast so your description of your experiences is strangely motivating.

 

Cheers

[yehuda]

Secondly, the biggest danger is in banking right and/or giving right rudder. At low speeds this isn't usually a problem, but if you are doing something like 250km/h and suddenly slam your cyclic and pedals to the right you will die. Left is better in those cases.

 

Seems like that was the problem. Strong rudder to the right and ~270kph.

I usualy keep my speed at around 200kph (just to be safe I guess) when on route, and use very gentle movments on my stick.

[WynnTTr]

Seems like that was the problem. Strong rudder to the right and ~270kph.

I usualy keep my speed at around 200kph (just to be safe I guess) when on route, and use very gentle movments on my stick.

The BS can handle a lot more than that though. It is after all, a military attack chopper and you can be rough with it. It just takes time and getting to know the Shark.

[EtherealN]

First of all, your throttles are not set to auto. Page-Up twice after starting your engines (it's the yellow lever down on the far left). Your engines are not running at full power, which causes your rotor RPM to be very low, which in turn requires a huge angle-of-attack on the blades to get your airborne. (12 degree alfa is almost max range, and that's only to get you barely climbing...)

 

When you look at outside view in your level flight, the blades are very close to intersection as well, since you are at a very high speed. You are then also flying uncleanly (watch the ball under the Horisontal Situation Indicator), with the ball at the right asking for a right rudder, which would send the lower blades closer to the upper blades.

 

Combine all of this with your high speed... When you then applied right rudder and right turn, already being so close to the parameters and not having the engines running properly... That's what killed you.

 

I should also warn you that you never put the ejection seat system on... :P

Edited May 13, 2009 by EtherealN
Corrected an error

[CAT_101st]

Seems like that was the problem. Strong rudder to the right and ~270kph.

I usualy keep my speed at around 200kph (just to be safe I guess) when on route, and use very gentle movments on my stick.

 

I agree. I never go over 220 unless evading and have a half load. your just stressing the airframe to the limit. The hardest thing in a helo to get use to is the slow speeds. It is a pig of a aricraft and shuld be flown like a big buss. big turns slow and easy. Keep in mind that all the videos you see of the KA-50 doing tricks it is unloaded and has very little fule onboard.

[EtherealN]

Yeah WynnTTr, it is actually possible to fly it safe-ish at 350km/h, but that necessitates that one really really knows what one can do while in that regime - and the kind of atmosphere one's in, as well... :P

[mbolan]

Very helpful. Thanks a lot. You've brought up issues that I didn't even know existed.

 

I suppose I need to spend more time reading and less time flying - not easy with a sim like this to hand. I'm really impressed with the programming talent that produced something so clean and comprehensive.

 

Thanks again. I'll keep studying hard

[EtherealN]

Well, to be honest, do fly. And fly a lot. I'd recommend practicing on a map where it's just you and you start in the air, and activate crash recovery.

 

That way, you can have fun through flying and quickly recover from crashes to find out what caused it. (A luxury the real pilots don't have.)

 

But yeah, do study a bit, but generally speaking you can just start off with flying around like that and be sure to only make very careful inputs. Then as you are comfortable with that, slowly take the bird around for more rapid maneuvers, and do check the F2 view often to see how your rotors behave. Investigating the rotors can teach you a lot in a very visual way that reading just can't do.

 

And don't beat yourself up - I started conversion to a new aircraft type today IRL and made a very very embarrasing misjudgement on my landing circuit, with instructor in the cockpit and the tower right there to see me make a fool of myself. :P

Edited May 13, 2009 by EtherealN

[mbolan]

Yes, the idea of bus driver had sprung to my mind.

 

I think that many NewB's are going to need this info. I didn't get it from the doco's that came with the DVD, nor from the various videos I've seen. I guess my experience with throwing Longbow around the sky and the Campaign 'familiarisation' video that urges flying at 250 km over an area because it's 'dangerous' contributed to my obviously slack attitude!

 

Your description of a pig is helpful, as I can adjust my mental models from a high jinks machine to a bus full of queasy pensioners on a Disney tour.

 

They must have lost a few in the field if it really had these characteristics.

 

Who'd be a test pilot?

[EtherealN]

Well, the Kamov buerou has a tradition of designing helicopters with such co-axial systems, though they usually made aircraft for the soviet navy (which is why this is the first co-axial army attack chopper), so they had built up the knowledge of the problems over several decades. And there are some very big pros inherent to the design that might outweigh the risks of blade intersection and so on, mainly in efficiency (since you're not spending fuel and engine power on a tailrotor), and you won't be uncontrollable if you get your tail shot off. I've actually flow the Ka-50 back to base with no tail after a SAM took a liking to it...

 

It's basically a case of knowing it's limits, and of course the pilots flying these things professionally will already have a lot of hours in conventional helicopters, so they don't get the double-whammy of both chopper and co-axial at the same time. :P

[EvilBivol-1]

Hardly a pig:

 

Maybe it's not the animal, but the jockey? ;)

Edited May 13, 2009 by EvilBivol-1

[PeterP]

Very good summary/explanation of the limits of a coaxial rotor design:

http://forums.eagle.ru/showthread.php?p=671731#post671731

[159th_Viper]

....I've actually flow the Ka-50 back to base with no tail after a SAM took a liking to it......

 

Aye - same here.

 

Was wondering why I'm Top-Heavy all of a sudden..........mental flash saw me putting it down to pre-flight donuts until externals revealed missing parts.....:P

 

With EB on this one - It's not that the Kamov cannot take the punishment - she can, and a lot! It's in the knowing as to how to best deal out the Punishment.....and that takes practice!

 

So yeah - In the beginning treat her like a Bus full of Pensioners. However note that in a coupla months you'll be throwing her around like a Ferrari on the Nürburgring......:D

[EtherealN]

I've actually done that, almost literally.

 

I basically decided on a circuit around the taxiways and runway of an airport, and was practicing going as low as possible, as fast as possible, and as close to the tarmac (or well, concrete...) as possible, causing some rediculously sharp turns. And just to make it worse on me I did the circuit with right-hand turns. (The basic thought of the exercise was that if I, in a mission, get jumped by jets or something like that, it would be really nice to know exactly how fast I can flee to safety. If an F-15 has taken a liking to me I want to get to a masked position As Soon As...)

 

With enough practice in handling the shark, you can throw it around there like an absolute maniac. (I had generators dropping power all over the place due to the sharpness of the rotor flarings and so on, and I know I know, not supposed to let that happen, but hey - not supposed to fly like that at all... :P )

 

The key really lies in having enough practice that the limitations become hardwired in you. Then you'll find yourself doing those small adjustments to sharply decrease speed (while dumping collective) to get you down to a safe zone for a right turn without even thinking about it - it's just become a natural part of making a sharp right-turn from 300km/h. :P

 

Also, whenever you do stuff like that - be happy it's a sim. :D Absolutely no way I'd do something like that in the real thing...

Edited May 13, 2009 by EtherealN

[EinsteinEP]

http://forums.eagle.ru/showthread.php?p=671731&highlight=ghostbusters#post671731

 

[edit: Doh! Didn't see PeterP had posted this same link earlier. Thanks PeterP!]

Edited May 13, 2009 by EinsteinEP

[mbolan]

Help and descriptions greatly appreciated

 

Thanks all. I hope you all realise how useful it is to have a few savvy simmers out there to explain and focus we NewBies on this superb item.

 

I hope that the kind of problems that come up when struggling to learn something as complex as this, will be handled in the new manual. It sure would save a lot of struggle time and would also increase sales.

 

I'm still in awe of the programming and design talent that went into this. Things I thought were problems turn out to be real world issues with deep real world significance. The roots of a great sim.

 

Anyway, all thanks. I've been chucking this thing around the sky thinking that the explosions were some malfunction. As someone said, maybe it's the jockey not the horse.

 

Good cheer to everyone.

[EtherealN]

Agreed mbolan. You should have seen me when I first ran into a Rotor Vortex State. I was all "wtf just happened?" and then all "wait... they modelled THAT? AWESOME!". :P

 

I've had sooooo many close calls with Rotor Vortex States sending me plummeting to the ground mid-combat, but after enough cases of narrowly just slightly bumping the ground after a close exit from the Ring I've gotten enough of a habit to really pay attention to my variometer... :D