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propeller crash


Xilon_x

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Send us a track. We can tell you what's wrong with your flight. Probably you fly too fast and/or you turning hard to right.

 

If you pay attention, if you fly faster, your upper and lower rotors come closer each other. You need to take care about it.

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There's overspeed warning light on upper-left dash and it beeps of course but, no indicator for rotors. You'll learn it overtime.

 

Plus, you don't need overspeeding to crash rotors. A very hard right turning can be cause that issue. Be careful on your stick movements.


Edited by Devrim

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you must watch the chopper in flight, you must save and re run every mission you have screwed up due to pilot error. Once the mechanics of the engine is understood.... you will realise that left is right and right is wrong!

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help I can not understand why the propellers are destroyed while you are flying.

 

 

Because Airflow will create more lift and more lift Creates more upflex of the Rotor Blade.

 

So if you fly forward with an Helicopter the blade which is moving forward into the Airflow will create more lift + more upward flex than the blade which is going out of the Airflow.

So on an KA-50 Helicopter in fast forward flight the lower rotor disk (Counter clockwise rotating) will create more lift on the right side whilst the upper Rotordisk(Clockwise rotating) will do on the left, which does bend them into each other.

 

 

For sure this can happen in maneuvers too. Regardless your speed.

 

 

You can see this in the outside view F2 just compare Hover to Fast forward flight appearance.

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Because Airflow will create more lift and more lift Creates more upflex of the Rotor Blade.

 

So if you fly forward with an Helicopter the blade which is moving forward into the Airflow will create more lift + more upward flex than the blade which is going out of the Airflow.

So on an KA-50 Helicopter in fast forward flight the lower rotor disk (Counter clockwise rotating) will create more lift on the right side whilst the upper Rotordisk(Clockwise rotating) will do on the left, which does bend them into each other.

 

 

For sure this can happen in maneuvers too. Regardless your speed.

 

 

You can see this in the outside view F2 just compare Hover to Fast forward flight appearance.

 

 

This is also the reason why any helicopter with any IAS, single rotor systems even too a larger extend, tilt to the side of the returning blade, the faster they fly the more they tilt until that part of the disc looses lift and stalls, that is also one of the reasons helicopters cannot fly beyond a certain speed, relative to their rotor system.

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This is also the reason why any helicopter with any IAS, single rotor systems even too a larger extend, tilt to the side of the returning blade, the faster they fly the more they tilt until that part of the disc looses lift and stalls, that is also one of the reasons helicopters cannot fly beyond a certain speed, relative to their rotor system.

 

Correct:D

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  • 9 months later...

Is the sideway tilt of the two disks correct in the DCS Ka-50?

 

When a heli flies forward, the blades on the advancing side produce more lift, the retreating side less lift. But that does not mean that the disk will tilt sideways. It should tilt backwards, because it is a rotating system and the inertia of the blades will cause the largest deviation of the disk angle to happen 90° after the position where the maximum perpendicular force (lift) appeared (gyroscopic precession).

 

This is why a heli will start to have a pitch up tendency the faster it gets, which needs to be countered with some forward cyclic.

 

But why do the rotors tilt sideways in F2 view? To me that seems incorrect. The explanation in this thread seems trivial, but to my understanding it is wrong. If it was true, any of the older RC helicopters would require roll input to stay level during forward flight. Which is not the case. They need forward cyclic input, because they will pitch up and not roll sideways.

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Retreating blade stall, mast bumping, rotor collisions... Not the way man was meant to fly - helicopters should be illegal - they're just wrong

:megalol:


Edited by Bun

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But what is causing the disks to tilt sideways? It cannot be the airspeed difference between advancing and retreating blade.

 

Perhaps the the rotor’s position (top or bottom) makes it more or less susceptible to retreating blade stall because of rotor wash effects. Then the stall induced roll would not be balanced out.

Just a thought, as I have not been able to find any literature to support this notion.

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It is just a function of the dissimilar lift from the counter-rotating blades in the airflow, and that's why it becomes more problematic the faster you go.

 

If you search the forum (or even look in the manual I think) you'll find lots of illustrations showing how the effect occurs.

 

If you don't want blade-clash:

1/ don't manoeuvre while at high speed

2/ if you have to manoeuvre at high speed, unload the collective before you do it.

Cheers.

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Even single rotor helicopters have their rotor discs "tilted." The advancing side "climbs" and the retreating side "dives." The faster you go, i.e. the larger difference in relative airspeeds of the advancing and retreating blades, the larger the "climbs" and "dives." The maximum flap angles (up and down, or in reality "most up" and "least up") occur at the point where the relative speed of the rotor blade is at its highest and lowest, which is right out to the sides in straight and level flight.

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Even single rotor helicopters have their rotor discs "tilted." The advancing side "climbs" and the retreating side "dives." The faster you go, i.e. the larger difference in relative airspeeds of the advancing and retreating blades, the larger the "climbs" and "dives." The maximum flap angles (up and down, or in reality "most up" and "least up") occur at the point where the relative speed of the rotor blade is at its highest and lowest, which is right out to the sides in straight and level flight.

 

 

I thought those Max flap angles were fore and aft.

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I thought those Max flap angles were fore and aft.

 

When I say flap angles, I'm referring to the apparent tilting of the rotor disc. The highest point in the tilt will be at the point of highest relative rotor blade speed, and the lowest point in the tilt will be at the point of slowest relative rotor blade speed.

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

 

It is a dynamic system. At the highest point of blade speed, the blade gets the most lift. So its upwards velocity is the highest. That does not mean that the blade will stop traveling upwards afterwards. It will still continue to travel upward until it is at the front of the helicopter.

 

It is the same as with the regular cyclic controlls. In order to pitch the helicopter backwards on a clockwise rotating rotor, the blade on the 3 o'clock side will have its lowest pitch angle, and the blade on the 9 o'clock side will have its highest pitch angle. So to pitch backwards, the blade on the right will have the lowest lift and the blade on the left its highest lift. Exactly the same difference in lift that happens during forward flight. And the result is, that the disk tilts backwards.

 

In fact, if the rotors should tilt to a side during forward flight, they should tilt in the exact opposite direction due to tranverse flow. The blade in front of the heli will have higher lift than the blade in the rear, because the air over the rear blade is already accelerated downwards. This means, that on a clockwise rotor the disk would tilt to the left. On the Ka-50 the bottom rotor would tilt to the right and the top rotor to the left, which is the exact opposite of what is happening.

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Disadvantages

 

(…)

 

Rotor self-intersection

 

A single rotor in forward flight will assume a slightly conical shape due to the lifting force on the blades. This cone will also be tilted sideways with respect to the direction of flight because the blades see different airspeeds at different points in their cycle. That is to say, the blades will generate more lift while they advance into the direction of flight, and less while they retreat on the opposite side of the helicopter. The higher the forward speed, the larger will this effect be (In fact, there will usually be an area on the rotor where the blades do not produce lift because the airflow over them is reversed: the forward speed of the helicopter is greater than the local speed of the blade).

 

In a coaxial design, both rotors turn in opposite directions, so their tilts will be in opposite directions too: the clockwise-turning one will tilt right, and the anticlockwise-turning one will tilt left (the actual locations of maximum bending are not quite as clear cut because of blade inertia, but this serves as a basic explanation).

 

The resultant problem is pretty obvious: the two rotors can intersect each other. This is a Bad Thing and will lead to all sorts of issues like rapid unplanned dissasembly of the rest of the rotor blades. A pilot in this situation will most likely make use of the conveniently installed ejection mechanism.

 

The actual forward speed at which self-intersection will occur is not published (to the best of my knowledge), but is probably somewhere above 250km/h. This is only taking forward flight into account... sudden collective or cyclic inputs at high but not critical airpeeds may have the same effect.

 

The overall effect is that coaxial rotor helicopters are more limited in their flight envelopes than conventional ones. Although this is not a fatal drawback, agility is highly valued for attack helicopters.

 

& this disadvantage can be largely overcome if you account for it in your manoeuvring (drop the collective to turn)

Cheers.

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