Meaning, happiness and the story of self

[Outrider]

Thanks O
When I asked that same question to one of the machanics who works on it every day he didn't give me a satisfactory answer only to say that's the way it is ??

It sort of is 'just like that' - it's a slight issue, but not enough of one that it was worth increasing the problems of logistics and manufacturing of having two mirrored sets of engines and props and the like, and the system of making sure you always used the right ones.

O.

[Walter]

It sort of is 'just like that' - it's a slight issue, but not enough of one that it was worth increasing the problems of logistics and manufacturing of having two mirrored sets of engines and props and the like, and the system of making sure you always used the right ones.

O.

cheers O.

Thanks for answering

I have many more questions if you're interested ?

[Outrider]

cheers O.

Thanks for answering

I have many more questions if you're interested ?

Sure   I'm in Health and Safety now, I have to put that degree study to good somehow, right?

O.

[Walter]

Sure   I'm in Health and Safety now, I have to put that degree study to good somehow, right?

O.

i always use a platform now , not step ladders , honest!

[Walter]

O.
My next question concerns helicopter main rotor .
In level forward flight one blade will be traveling into the direction of forward motion and another wil be travelling backwards from the forward motion which would suggest a twisting corksrew motion would result . Are the blades able to flex up and down at the root to counter this or is something else going on?

[Outrider]

O.
My next question concerns helicopter main rotor .
In level forward flight one blade will be traveling into the direction of forward motion and another wil be travelling backwards from the forward motion which would suggest a twisting corksrew motion would result . Are the blades able to flex up and down at the root to counter this or is something else going on?

So, helicopters have a number of effects due to the single  large rotor - the largest one is the torque effect that tries to skew the tail around, hence the tail rotor.  The second major one once the helicopter is moving is that each rotor spends part of its time moving into the wind and part moving away - this has the effect of increasing the drag on one side (which is also countered by controlling the tail rotor speed) and increasing the lift generated by the blade moving into the wind relative to that moving away.  This is countered in a number of different ways, from pilot input to slight automatic variation of the angle of attack of each rotor blade by rotating them at the hub where they attach to the rotor hub.

Helicopters with two (or more) rotors (i.e. Chinook, V-22 Osprey, KA-32, most publicly available drones) have contra-rotating or co-axial rotors to eliminate these effects.

Commonly the blades do flex with the lift effects, more from a materials strength point of view, although in some of the advanced and high-power instances this is designed to manifest in a controlled manner to avoid hyper-sonic shockwaves at the blade-tips and to create angle-of-attack changes along the length of the aerofoil of the rotor to maximise lift/efficiency/power depending on the need.

There has been some really advanced work on using electro-reactive materials to change the aerofoil cross-section rather than rely on mechanical linkages in the hub as a control mechanism, in order to reduce weight and avoid the mechanical wear and tear, but I'm not sure anyone's pursuing it as a realistic option at the moment, it's not even that commonly looked at for fixed wings.  I did hear some talk about some of the Formula 1 teams 'wondering' publicly if such a device would be considered a moveable aerodynamic part (which are banned at the moment) and it came back with fairly confident 'yes it would' so even they aren't looking at it right now.

O.

[Walter]

Thanks for a great reply O.
Am I right in thinking some helicopters have air jets along the tail boom to eliminate the tail rotor and its noise
I think the coanda effect is used used in this application ?

[Outrider]

Thanks for a great reply O.
Am I right in thinking some helicopters have air jets along the tail boom to eliminate the tail rotor and its noise
I think the coanda effect is used used in this application ?

The most common and effective system, Hughes/McDonnell Douglas 'NOTAR' system, does use the Coanda effect to give some control effects from varying the output, but there some less common systems which are simply jet outputs from the turbines to counter the torque of the rotors.  In general you get better control from a rotor than from a pure jet output, which is why they're not common (they don't respond as other helicopters, and need some getting used to as I understand it), whereas the NOTAR system does behave pretty consistently with 'normal' tail-rotor systems.

NOTAR is useful for city use because it's quieter (tail rotors, and the interaction of tail rotors and main rotor downwash are both very noisy) and it removes some of the physical hazard of the tail rotor when close to the floor and on the ground.  A lot of the development money was put up, I think, as it was seen from a military point of view to be more robust without a tail rotor that could be damaged, but the tail rotor is such a small target vs the main rotor that it didn't increase survivability much, and the dependence on the Coanda effect for manouevring meant it was less agile than conventional systems.

O.

[Walter]

Another great reply

Mind you you can't beat the sound of a Bell Huey 👍