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propeller crash


Xilon_x

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l9HoeHACrck?t=73

 

the set time option doesn't seem to want to work.

If you go to 1:11 & watch through to 1:18 you can actually see the effect happening.

 

(one of those things landed at the heli-pad outside my work once - they are loud !)


Edited by Weta43

Cheers.

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No thanks, I'm totally okay with you thinking it's wrong. I'm not in the business of changing your mind. I'm just posting this so future readers understand that I'm saying that the in-game behavior is correct. There are numerous online resources (not limited to coaxial rotor systems) that explain this better than I could. If you disagree with those explanations, I would suggest taking it up with the authors of those various online resources.

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Why should the highest point of tilt be at the highest point of blade speed?

:) People have already told you why, & the explanation fits with observed reality. Apparently you just don't accept their explanation.

The explanation in this thread seems trivial, but to my understanding it is wrong.

 

If the explanation given fits with observed reality, and your expectations don't, perhaps you should re-visit your own understanding of the situation & see what factors you're leaving out.

 

Edit - Remember that it's already been said that the highest point of the cone isn't actually at 90 degrees to the forward motion - there is some precession happening, there's just other forces at work too.


Edited by Weta43

Cheers.

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The less-than-90° due to the hinging being at a certain distance to the rotor shaft may indeed be the part I was missing.

 

Durnig fast forward flight the blades of the lower rotor will have the highest lift at the 3 o'clock position.

With a super rigid rotor the disk would tilt backwards and have its highest point at 12 o'clock.

With a hinged system and a reduced phase delay of lets say 70°, the disk will tilt mostly backwards, but also slightly to the left.

The upper rotor will tilt mostly backwards, but also slightly to the right.

The backwards tilt component of both rotors gets compensated by the pilot by applying forward cyclic, as you do in the DCS Ka-50 during forward flight.

With a single rotor helicopter the pilot would also add a certain ammount of roll to counter the smaller roll moment. But on the Ka-50 this would mean that the lower rotor needs right roll and the upper rotor needs left roll. As you cannot controll the cyclic independent on each rotor, there is no way to compensate for that.

 

As a result we end up with the disks tilting into each other.

 

While the source of the disk titt is dissymmetry of lift, it is not as simple as it was described here. The disks do not tilt left and right, they tilt backwards alot and a little to the side. The backwards tilt (pitching up) gets compensated by the pilot, the sideways tilt does not.

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  • 2 weeks later...

I recall that developers told at least once here at forums that the rotor blades clashing is not realistic, but it is implemented in DCS to overcome the difficult part of the simulations of the flight envelope and so on the clashing is there to make a pilot aware of the disallowed parameters.

 

It is similar thing as Mi-24 tail boom getting clashed by the main rotor. Or how Mi-24 can't hover because its torque will damage the hub etc.

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Incidents and accidents

 

Ka-50 "Bort 22" with a distinctive "Black Shark" livery was lost in a crash on 17 June 1998. Its pilot Maj. Gen. Boris Vorobyov was killed in the crash.[12] Cause of the accident has been attributed to the "helicopter's co-axial rotor blades hitting each other during hard manoeuvring".[40]

source:

https://military.wikia.org/wiki/Kamov_Ka-50

 

video:

cpUdxPZzETk

 

edit:

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.


Edited by Weta43

Cheers.

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source:

 

 

edit:

 

I know that accident, but still I only point out what I remember as I raised question about that back then.... Corresponding with that same claims by some experts.

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