Fenestron Question

[Cirrus]

Good Luck!! :lol:

 

 

That's constructive.

[Skids Up]

As was yours (which was my point) - but then that is the trend of these things it seems like most of the time...

[newfieboy]

A very interesting question, i have done some thinking about this and wonder too if because the fenestron is performing the same task as the traditional tail rotor and it is just a bunch of little airfoils, would it not be subjected to the same aerodynamic forces. I just don't know...... There is a related thread on Vertical Reference titled Fenestron, Lotsa flow and the posters name is DakarNick. Maybe you can have a look through that one and see if you can get some answers. cheers. L3driver.

 

Having flown both the Gazzelle in the AAC and the 365N2 on the North Sea was always aware that you could get into LTE in both types we just knew it as fenestron stall as oposed to LTE, but pretty much the same consequences. Happy New Year to all.

[firefly]

Does anyone know if the Fenestron is susceptible to LTE?

yes, it is.

and yes, it's called LFE.

but I always liked UGALY: Uncommanded Gradually Accelerating Left Yaw.

Aerodynamic conditions conducive & flight regimes susceptible are the same as conventional T/R.

 

 

 

[Phil Croucher]

Yeah, sure is UGALY when it happens

 

Phil

[Cirrus]

Thanks.

[What Limits]

Having flown large and small fenestrons, NOTARs and old-fashioned T/Rs I would suggest that it is possible to get into any kind of Loss of Yaw Control Event. It does not matter what you call it (and you can call it plenty of things) if you get to the limit of its capabilities it gives up.

 

Fenestrons do take advantage of the effect of ducting the airflow which makes it possible to reduce the size of the blades and therefore the power required to turn the thing is also reduced. Like any rotor system, if you screw up the airflow in any way, you are affecting the thrust produced. One of the other downsides is the fin effect. When hovering cross-wind, an excessive amount of angle of bank is required to keep the helicopter straight. I personally have seen 25 degrees and it ain't comfortable.

 

The manufacturer does not accept the term fenestron stall, in fact if you look on youtube I think you can find the video of the test pilot performing a recovery from max yaw rate. A number of helicopters have been lost to loss of yaw control simply because the pilot could not physically reach the pedal stop due to incorrect pedal or seating position. (Could you if you have to?)

 

Theoretically you could dip your tail in water, trees etc. if you have a NOTAR equipped helicopter. This is because the fan is at the forward end of the tail boom. Most of the anti-torque thrust comes from the slots cut the length of the tail boom (Google COANDA EFFECT for further explanation). The only rotating component at the back is the thruster can which is connected to the yaw pedals. When you want to spot turn in the hover, the can rotates and exposes more or less of the thrust aperture. Don't worry its only cold air!