Loss of tail-rotor effectiveness

[Migow]

hi, is Loss of tail-rotor effectiveness implemented or will be?( mi8 and huey)

and Ground resonance ?

thx :)

[Rotorhead]

During one of my very first takeoffs, I found myself unable to control the yaw. At some point it worked normally, and all of a sudden, even a full pedals deflection couldn't stop my helo from spinning. Then back to normal flight, and back to uncontrollable spinning...

 

Somehow I managed to bring it back to the ground in one piece (this baby can take heavy impact pretty easily, I tell you), just to found I accidentally took off with my throttle lowered. As I raised my collective, the engines just haven't enough power to drive the tail rotor. After fully opening my throttle, voila - problem fixed.

 

About ground resonance, I'd like to know as well.

[Weta43]

Tail rotor effectiveness ?

Under what circumstances ?

If you accidentally reverse into a building, it'll become a lot less effective.

 

I think I read in the forum the intention is to implement the equivalent of VRS for the tail rotor, but I could be wrong.

[GunfighterSIX]

loss of tail rotor effectiveness isnt prevalent in large powerful aircraft such as mi-8's, it is more of an issue for small aircraft like jet rangers and oh-58's and maybe Huey's. They didn't even mention it when i moved up the the UH-60 course, but it was a big deal in the oh-58 and ranger. And Ground resonance hasn't been talked about much, i think it might be to knew helicopters having better vibration control and Resistance. Not total sure on that, i would have to do some research.

[AlphaOneSix]

loss of tail rotor effectiveness isnt prevalent in large powerful aircraft such as mi-8's, it is more of an issue for small aircraft like jet rangers and oh-58's and maybe Huey's. They didn't even mention it when i moved up the the UH-60 course, but it was a big deal in the oh-58 and ranger. And Ground resonance hasn't been talked about much, i think it might be to knew helicopters having better vibration control and Resistance. Not total sure on that, i would have to do some research.

 

Oh it's definitely a problem in the UH-1. The common thread from the bolded aircraft above is Bell Helicopters. Bell has an unfortunate history of designing helicopters that are to easier to get into LTE than any other manufacturer.

 

Ground resonance is mainly a problem with three-bladed, fully articulated rotor systems (well, first off it can ONLY happen on a fully-articulated rotor). I'm not sure I've heard of it happening to an aircraft with more than three blades in the rotor, although I'm sure it's possible. It just seems like it's much easier to knock a three-bladed system out of balance...just look at that Chinook video of the induced ground resonance test.

[Rammit]

The Wessex HU-5 had big problems with ground resonance if I recall, that has four blades

[Bushmanni]

Finnish Mi-8 pilot wrote in his autobiography that it's quite prone to LTE and you need to be extra mindful of the wind direction because of it.

[AlphaOneSix]

Maybe depends on the version of the Mi-8? This was true for the Mi-8T and Mi-8P and the like...tail rotor on the right (starboard) side. But it's rare to get LTE with newer versions (unless you put the helicopter into conditions where pretty much any helicopter would experience LTE). But yeah, crosswinds from the left make the tail rotor work much harder in a hover, and a strong enough crosswind will just push the tail around no matter how much pedal you put in.

[Yurgon]

Ground resonance is mainly a problem with three-bladed, fully articulated rotor systems (well, first off it can ONLY happen on a fully-articulated rotor). I'm not sure I've heard of it happening to an aircraft with more than three blades in the rotor, although I'm sure it's possible.

 

I think that's exactly what happened to this Lynx (fast forward to 3:25):

 

[AlphaOneSix]

I think that's exactly what happened to this Lynx (fast forward to 3:25):

 

 

Nah, Lynx has a rigid rotor hub, not capable of ground resonance. Besides, the out-of-balance situation results in lateral vibration, not vertical. The bouncing in the Lynx video may have something to do with the Lynx's ability to have negative pitch in the blades (most helicopters have a lower limit of positive 1 degree or so).

[Yurgon]

Nah, Lynx has a rigid rotor hub, not capable of ground resonance. Besides, the out-of-balance situation results in lateral vibration, not vertical. The bouncing in the Lynx video may have something to do with the Lynx's ability to have negative pitch in the blades (most helicopters have a lower limit of positive 1 degree or so).

 

I see, good to know. :book:

[heloguy]

loss of tail rotor effectiveness isnt prevalent in large powerful aircraft such as mi-8's, it is more of an issue for small aircraft like jet rangers and oh-58's and maybe Huey's. They didn't even mention it when i moved up the the UH-60 course, but it was a big deal in the oh-58 and ranger. And Ground resonance hasn't been talked about much, i think it might be to knew helicopters having better vibration control and Resistance. Not total sure on that, i would have to do some research.

 

 

The aero manual mentions that ground resonance is more prevalent in 3 bladed, fully articulated rotors systems. Hence this video:

 

[Bushmanni]

Maybe depends on the version of the Mi-8? This was true for the Mi-8T and Mi-8P and the like...tail rotor on the right (starboard) side. But it's rare to get LTE with newer versions (unless you put the helicopter into conditions where pretty much any helicopter would experience LTE). But yeah, crosswinds from the left make the tail rotor work much harder in a hover, and a strong enough crosswind will just push the tail around no matter how much pedal you put in.

 

Finnish Mi-8's had the tail rotor on the right side so yes, they were the older version.

[AlphaOneSix]

Finnish Mi-8's had the tail rotor on the right side so yes, they were the older version.

 

Older Mi-8s with the tail rotor on the right had the tail rotor spinning down into the rotor wash. When it was moved to the left side, all they did was flip the gearbox...the tail rotor on the left side spins up into the rotor wash, which increases its effectiveness quite a bit.

[Rotorhead]

The aero manual mentions that ground resonance is more prevalent in 3 bladed, fully articulated rotors systems. Hence this video:

 

 

Video description says: "A ground resonance test gone wrong..."

 

I'm no expert but wasn't that exactly what they wanted to achieve?

[heloguy]

Video description says: "A ground resonance test gone wrong..."

 

I'm no expert but wasn't that exactly what they wanted to achieve?

 

 

Yeah, who knows who posted the video, and how much they know about helicopters.

 

If you artificially induce ground resonance, I'm sure you understand that it will destroy the helicopter if you let it continue.

 

That test was done as a demonstration on what it will actually do. Probably in an old A model 47 that the Army was throwing to the boneyard already.

[Migow]

mi 8 old model LTE

:(

Edited September 10, 2013 by Fifou265