Notar management with engine failure??

[rotorpol]

How does tail rotor system keeps on working, in Notar equiped choppers, during a real engine failure??

I,d appreciate some information regarding this issue.

Adios

:O

[NickLappos]

makes no difference, all notar air is delivered from a fan driven by the transmission.

why would you think to ask the question?

[rotorpol]

Mr Nick Lappos:

I simply didn´t know the exact way Notarl system worked.

I knew antitorque force was obtained fron an airflow blown over tail boom end surface, but ignored it came from a fan, it´s been a while without refreshing the manner Notar system works, and I had the idea of the engine delivering somehow this airflow for tail control purposes.

Thank you for the explanation:ok:

[Dave_Jackson]

It would be interesting to know what percentage of the yaw moment of a Notar equipped helicopter comes from the fan generated sideward thrust and what percentage comes from the Coanda effect.

It would then be interesting to know if the Coanda effect is lost when the airflow is from a rotor that is in the autorotational state.

[What Limits]

It is my understanding that the Coanda effect accounts for up to 60% of anti-torque thrust in the hover.

In autorotation anti-torque thrust required must be minimal so can be overcome by using the jet thruster.

[NickLappos]

the NOTAR derives no thrust from the Coanda effect except when in a steady hover, at speeds below about 10 knots (6 knots rearward). Only when a stream of air blows on the cone from the rotor (only in a low speed hover) can there be any coanda effect.

The NOTAR'S technology has been vastly oversold, it is mostly a tip fan device, the tailcone slots are effective across a tiny percentage of its envelope.

In hover, forward flight, low speed maneuvering the tip jet is the principal source of yaw control. Yes, in a steady hover at low speed, it is possible that half the anti-torque comes from the slotted tail cone, but minor fight deviations from that steady hover cause the Coanda effect to vanish.

[Dave_Jackson]

Thanks WL and Nick,

Perhaps the vertical stabilizer starts to take over a portion of the yaw stability from the Coanda effect as the forward velocity increases.

[NickLappos]

Absolutely, Dave, most helos use the vertical fin for the trimmed anti-torque in cruise, as a power saving trick, since fin thrust is much more efficient than rotor thrust.
Maneuvering is done through the rotor, though.
In most helos, the tail rotor power consumption in cruise is that necessary to turn the box and the blades at near zero thrust. NOTAR is no exception, in fact, in some NOTAR models the fins have a rudder so that even electronic stabiity is done through the fin.