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Even the pros put their blades together


wickedpenguin

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Out of curiosity, I Googled "KA-50 crash" to see if there had been any real-life crashes of this excellent but rare bird. I was surprised by these two finds, talking about a crash in 1998:

 

Kamov Ka-50 crash kills Torzhok training base commander

 

Russian Army Maj Gen Boris Vorbiev was killed on 17 June, when the Kamov Ka-50 Hokum he was piloting crashed at the Torzhok combat training centre.

Vorbiev, commander of the Torzhok centre, was an experienced helicopter pilot.

 

 

 

According to witnesses, the accident occurred as the Ka-50 was being flown at low altitude over the test centre. The helicopter collided with the ground and immediately exploded.

 

 

 

The flight data recorder has been recovered from the crash site, and is being reviewed by the investigating commission to try to establish the cause of the accident.

 

 

 

A handful of Ka-50 attack helicopters have been delivered to Torzhok for combat evaluation.

 

 

 

The Hokum is in competition with the Mil Mi-28 Havoc to provide a successor to the Russian Army Aviation's Mi-24 Hind combat assault helicopter.

 

 

 

Despite years of evaluation, the Russian defence ministry has been unable to provide adequate funding for the army to begin procuring either helicopter in the numbers required to replace the Mil Hind. Kamov is also developing a night attack variant of the Ka-50.

 

Rotor blade collision is blamed for Ka-50 crash

 

A collision between the co-axial main rotor blades caused the fatal crash of a Russian army Kamov Ka-50 attack helicopter in June 1998, says an official investigation into the accident.

 

 

 

The helicopter's pilot Maj Gen Boris Vorobyev, commander of the Army Aviation centre at Torzhok in the Tver region, was killed. He was one of the most experienced Russian military helicopter pilots.

 

 

 

The enquiry's official findings say "-the cause of the crash was the unintentional entry into an unexplored flight regime during complex combat manoeuvring exceeding current flight limitations". Eye witnesses claim the pilot was flying a simple terrain-hugging flight profile.

 

 

 

Many Russian helicopter experts claim that there is an unacceptable risk of collision between the upper and lower rotor blades during harsh combat manoeuvring, especially if abnormal rotor conditions have been caused by combat damage.

 

 

 

The crash of a Ka-50 prototype and those of earlier Kamov helicopters have been attributed to the same cause.

 

Despite the obvious tragedy, it is rather refreshing to know that even the best helicopter pilots in the world can manage to put their rotors together accidentally.

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I kind of agree with the second quote. It is actually strange that the Kamov desingers allow blade clashes to happen so easy. It is evident that even the most trained and experienced heli pilot can enter this flight regime even during practice, which is something that clearly should not happened.

Of course I can agree that blade clashing for us flight-simmers is OK, but for it to happen in real life is not ok. ?

 

edit: as I read through my post I find it hard to understand wth I was intending to say with this post... I'll just leave it like it is in case someone understands it anyway. I guess it didn't add very much to the thread anyway ;)


Edited by Boulund

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I kind of agree with the second quote. It is actually strange that the Kamov desingers allow blade clashes to happen so easy. It is evident that even the most trained and experienced heli pilot can enter this flight regime even during practice, which is something that clearly should not happened.

Of course I can agree that blade clashing for us flight-simmers is OK, but for it to happen in real life is not ok. ?

 

edit: as I read through my post I find it hard to understand wth I was intending to say with this post... I'll just leave it like it is in case someone understands it anyway. I guess it didn't add very much to the thread anyway ;)

 

Like all machines you need to treat them with due respect and keep them within certain limits. Any aircraft can be pushed past a "safe flight envelope".

I would guess an event like this is the equivalent of a conventional helicopter boom strike.:)

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....According to witnesses, the accident occurred as the Ka-50 was being flown at low altitude over the test centre. The helicopter collided with the ground and immediately exploded....

 

Was there not a post not so long ago that questioned the In-Game Propensity of the Kamov to explode when contacting the Ground?

 

The Question has been Answered it would seem........

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I would guess an event like this is the equivalent of a conventional helicopter boom strike.:)

 

Or stuff like when a helicopter (can't for the life of me recall the type) that was approaching for inflight-refuelling managed to cut it's refueling probe with it's blades. :D

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The Ka50, as a design, is NUTS! I love the sim but you couldn't pay me enough to put me in the real thing. It's a near-miss 3000 times a minute! Kudos to Russia (and Turkey) for taking a more traditional, survivable approach to their attack helicopter programs.

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Nuts?

 

Go to youtube and search for videos of conventional helicopters who lost their tail rotors due to enemy fire, gearbox failures and whatever else you'll like.

 

I'd much rather fly in a Ka-50 where, if I cause a rotordisc intersection, I'll end up ejecting with my zero/zero ejection seat instead of just spinning rapidly to my death or mutilation with the ww1-style pistol solution as my only option.

 

Since you are talking about "more survivable" I'd like your sources where flight hours in various regimes have been tallied and compared.

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Or stuff like when a helicopter (can't for the life of me recall the type) that was approaching for inflight-refuelling managed to cut it's refueling probe with it's blades. :D

here you go.

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The Ka50, as a design, is NUTS! I love the sim but you couldn't pay me enough to put me in the real thing. It's a near-miss 3000 times a minute! Kudos to Russia (and Turkey) for taking a more traditional, survivable approach to their attack helicopter programs.

 

Oh I very much don't agree, flying sober I've only had a blade clash once and that was being under fire and panic. I've probably flown 150hrs sober or so.

No problem at all to keep it within safe limits I thinks.

 

I'd imagine that you'd get a boom strike with a normal helicopter in the situations you get blade clash in the Ka-50(?)

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here you go.

 

Jesus! That pilot looked lucky that all that all that happened was he chopped off his refueling boom. Those rotors almost hit the top of the canopy!

 

I don't see why there aren't limiters built into the Ka-50 flight control system that keep the pilot from performing manuvers that would cause rotor strike. Is it because the Ka-50 is an older aircraft before the advent of modern fly-by-wire systems?

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Speed_2, it's because to safely guard against that you would need to have such wide margins that the helicopter's performance is slashed pretty much in half. Better to just train the pilots. I haven't had a blade strike in absolute ages (like a previous poster: while sober :P ) since I've learned what to look out for.

 

Though, also with the exception that sometimes I go out of my way to really test the limits of the bird and I sometimes end up getting rotor disc intersections while performing barrel rolls and loops and such. Obviously not something I would do in real life but even then it is relatively uncommon for it to happen. :P

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I might not be correct, but I think if you REALLY push the AH-64D you can cut the front off with the blades :O

 

I know the AH-64A can do it. I was actually on the flight line once when one of our Apaches chopped off its own PNVS. There was a test pilot in the front seat during a maintenance run-up, and he got out while the aircraft was running and kicked the cyclic on accident.

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Speed_2, it's because to safely guard against that you would need to have such wide margins that the helicopter's performance is slashed pretty much in half. Better to just train the pilots. I haven't had a blade strike in absolute ages (like a previous poster: while sober :P ) since I've learned what to look out for.

 

Though, also with the exception that sometimes I go out of my way to really test the limits of the bird and I sometimes end up getting rotor disc intersections while performing barrel rolls and loops and such. Obviously not something I would do in real life but even then it is relatively uncommon for it to happen. :P

 

I don't buy that arguement. The way I figure, the chopper knows its three dimensional airspeed, it's attitude, its rotor RPM, g-loading, mechanical frequency response of the rotors, current weight (dynamically updated as weapons are fired/fuel burned, and air density. It also knows what those values were in the past (did I leave anything out? :)). SO with that information, it should know where the rotor disk is. From knowing that, it should be able to determine EXACTLY what kind of manuver would cause the rotor to collide with some part of the aircraft, and ONLY limit those manuvers.

 

NOW, say your pitot tubes iced up... you could have a control system, that if not programmed right, that could cause the problem it was designed to prevent. Combine that with the expensiveness and complexity of such a flight control system, and maybe it IS just better to train the pilots well rather than design a control system to prevent a problem that only occurs VERY rarely in well-flown aircraft.


Edited by Speed_2

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It should be capable of figuring that out, but with what level of confidence? For me to trust an aircraft to not break up whatever I do I want a lot of tolerances built into. The aircraft I fly IRL is rated to +5,3G and -2,65G. If this was defined as "go above this and it breaks" I wouldn't go near that. Fortunately, it's a definition with good margins, which means that I can actually trust those limits even if the aircraft has a couple thousand flight hours, as long as normal maintenance proceedures has been implemented.

 

Too little margin and it would be very few hours in the air before the airframe might be in a state of fatigue where the limits have moved, and there is no way to dynamically detect this in the air other than to try it and see if you survive. :P

 

How do you intend to dynamically keep an eye on the exact fatigue of your rotor blades and how it might influence the possibilities of rotor disc intersection? You end up needing WIDE tolerances, and at that point a hardcoded limiter system would end up limiting pilots that with their training would be able to go closer to the edge than the limiters permit. And in a combat situation specifically they might have to actually go close to those limits to survive at all.

 

Here's a video of a rotorblade:

 

I do NOT want to be the person charged with programming a system that accurately predicts that. Especially not when it's not one but two discs. ;)

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Too little margin and it would be very few hours in the air before the airframe might be in a state of fatigue where the limits have moved, and there is no way to dynamically detect this in the air other than to try it and see if you survive. :P

 

How do you intend to dynamically keep an eye on the exact fatigue of your rotor blades and how it might influence the possibilities of rotor disc intersection? You end up needing WIDE tolerances, and at that point a hardcoded limiter system would end up limiting pilots that with their training would be able to go closer to the edge than the limiters permit.

 

1) What are the blades made of?

2) I HIGHLY doubt that fatigue is going to be an issue, but I am not a materials engineer, so I can't say for sure. I'd think that any material that would change by more than several inches would a) badly in need of replacing and b) not something you'd want to make a rotor out of anyway. But again, I can't say for sure, because that would be something outside my area.

 

As far as the system for calculating rotor disk position, it shouldn't be THAT bad. Hell, we made the F-117 fly and that was in the late 70s.


Edited by Speed_2

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On 1) Varies. I'm not sure what the most common material in military aviation is, but I'd bet on composites.

 

On number two, fatigue changes a lot of things in aircraft, most importantly what kinds of forces they can withstand. I'm not a materials engineer either. But to make one thing clear: all aerofoils flex. And more than several inches - at cruise a Boeing 787 has it's wingtips a full 10 feet higher than when stationary. If wings did not flex, they would crack, because the flexing of an aerofoil spreads the stresses throughout the entire structure, rather than all stresses being taken out at a single weakpoint as would be the case in a stiff construction. I am not sure how much the blades of a helo like the Ka-50 flex, but as you could see in the video I linked that was how they flexed while in the air. That was not a stationary test. (I think it's a Cobra.)

 

As a side-note, this principle is also used in construction of tall buildings - they are made to flex with the wind, since that is a much better alternative than having them fall down in a dramatic fasion the first time there's any kind of wind on them. (Or, for that matter, an earthquake.)´

 

The theory of this is pretty simple to observe: take a piece of spaghetti with one end in each hand, and bend it. It breaks. Take an identical straw of spaghetti and boil it for a few minutes and repeat the experiment. It no longer breaks. Get the right material and you can make a rotorblade or wing that has sufficient stiffness to maintain the same shape and lift throughout the flight envelope but still flex enough so as to dissipate forces throughout the structure.

 

EDIT

And on calculating... Well, what kind of computation power do you want to bring along in the helicopter? Show me a computer strong enough to make all those calculations, with the detail of the flexing, fatigue and all other such factors, that will fit in a helicopter. And then figure out a way to make it do those calculations properly and with confidence enough to let you set the limits close enough that you won't badly handicap your pilot.

 

I mean, seriously, the Soviet Union, Russia and several other countries have operated coaxials for a LONG time and you'd think that if what you are asking for was feasible and practical they'd jump on it? So unless you know of a way to calculate this properly, in real time, with sufficient precision, I'm not sure you should be happy with a "shouldn't be THAT bad". If that is the case, design such a system yourself and become a multi-millionaire. ;)


Edited by EtherealN

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And on calculating... Well, what kind of computation power do you want to bring along in the helicopter? Show me a computer strong enough to make all those calculations, with the detail of the flexing, fatigue and all other such factors, that will fit in a helicopter. And then figure out a way to make it do those calculations properly and with confidence enough to let you set the limits close enough that you won't badly handicap your pilot.;)

 

 

I think you are underestimating the power of modern computers, especially military-grade computers. People often think that civilian markets offer the newest and the best; they don't. Governments and militaries always have stuff that is long ahead of what you can get as a civilian. You know the junk on the Apollo craft that went to the moon and back? Those spacecraft had to do calculations far, far ahead of what civilian computers were able to do in those days.

 

Even the civilian stuff you can find would be able to perform the complex calculations behind the effects of temperature, humidity, chemical makeup, etc. on rotor lift. Such advanced computing really took off when nVidia learned that their graphics cards could do so much more than graphics. This video card, which costs only $500 (compared to the millions that the entire helicopter costs), has 480 separate processing cores, each capable of doing their own independent calculation. The power consumption is forgettable compared to the amount of power needed to move rotors at speeds necessary to pull an aircraft as fast as they can. Size is no matter either, nor heat, since cooling can easily be tied in with hydrolics.

 

The card I linked to can easily do all of the calculations that NASA did when they sent their Apollo space craft to and from the moon with far more precision a great many orders of magnitude faster than anything NASA could get their government hands on back in the day.


Edited by Waldo_II
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The apollo craft were mainly navigated optically, not through computation. They did not make a calculation that said "point it over there, in this velocity, and sit there for the ride". They made a calculation that said "okey, here's about where we go, call back in a few hours with your observations and we'll figure out some corrections".

 

Same goes for space probes today. They undergo many course corrections during their flights.

 

And yes, the nVidia cGPU's are pretty amazing (if I had the spare cash I'd buy one of their blades just to kick ass on Folding@home :P ), but the point remains: if it was "easy" - why haven't the people who risk their lives in these aircraft already implemented it? The answer: it isn't easy.

 

But, to repeat the repeated-to-death Apollo analogy: the apollo spacecraft was navigated optically. The computers were an aid, and it probably would not have been possible without them, but they were a long time from sufficient. And even today NASA space probes do not get calculations with sufficient detail to just launch them and wait. Throughout their travel there is a team handling the flight that constantly takes measurements and observations to calculate what corrections need to be made.

 

What we are talking about here is to do real-time calculations with an incredible precision that need to take into account a lot of things that cannot be directly measured. You can kill pilots if you make errors in it and, since this is a CAS helicopter, you can also kill the people that it was heading out to help.

 

BUT: I still have not seen anyone come up with numbers to indicate that coaxial helicopters are sufficiently more dangerous to operate compared to conventional helicopters. What we have is one or two referenced incidents where intersection caused fatalities - but how common is it for conventional designs to suffer failures in their tailrotors?

 

In the end, the "danger" of this has been greatly exhaggerated by some in this thread, and the complexity of an automated solution has been shrugged off as "shouldn't be too difficult". My question remains: if it is so simple, why haven't they done it?

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One word: UCAV. :P

 

But they have relatively simple physics calculations to do compared to what's being asked for here. ;)

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If computers are so good these days why bother having pilots? ;)

 

We don't. I recall that in the bid for America's new stealth high-altitude bomber, there was debate as to make it unmanned or not. The tasks could easily be performed without a pilot, but people argued that humans should always be the ones to be in control of the most powerful ordnance on earth, not computers. Apocalypse theorists.

 

Next generation fighter aircraft also may not have pilots. The current limitation on maneuverability, speed, altitude, etc. is the pilot and keeping him alive. Without a pilot, a jet could hold a 11-g turn for quite a long time, an obvious dogfighting advantage. Also argued was that having a pilot in a cockpit would give better situational awareness and intuition, however with modern sensor technologies, having onboard computers locate, ID, and identify threat level is not unlikely (The AH-64D locates, identifies, and lists threat level by itself already). Calculating the best maneuvering path to obtain a missile lock isn't too far ahead either.

 

Check out the sensor technology on the F-35 if you haven't.

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You're confusing network and sensor fusion meant to give a pilot SA for something a computer can make use of. It can make use of -some- of those things ... but not all.

 

And it has no ability to deal with false positives or negatives.

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