Tail Rotor of AS350 B3(H 125)
 

Regarding tail rotor of AS350 B3(H 125) , i am unable to understand that why that "small flat rectangular surface has been provided on trailing edge of tail rotor". Is there any aerodynamic reasons behind it. Can somebody throw some light on this

It fools the pilot into thinking he has a bigger tail rotor.

It is a trim tab and it increases the chord of the T/R blade. Moves more air.

FWIW, calling it a “trim tab” implies it would be trimmable. It is fixed and not adjustable. It simply increases the chord of the airfoil and therefore the thrust-- remembering the equation for lift.

I believe it was added as an appendage starting with the BA version primarily as a consequence of increased power/gross weight. The yaw-load compensator followed shortly thereafter on the B1.

Initially the tab was attached via rivets, and subject to a recurring inspection for cracks initiating at the rivet holes. The rivets were eliminated sometime around the introduction of the B3 Mod or B3/2B1 aircraft. To my knowledge, the majority of the newer, rivet-less tail rotors are painted gray while the older style are typically blue.

If I recall correctly, the tab was added originally for the AS355 T/R blade which were modified AS350 T/R blades. Since the 355 was T/R limited, the tab gave the 355 greater T/R authority thus a higher useable weight. Since the basic 350 and 355 are similar, Aerospatiale installed 355 parts on the 350 as an upgrade starting with the 350B1. The upgrade included the 355F M/R blades (wider chord) and the 355 T/R blades (with tab). The original 350B/C/D had narrow chord M/R blades and no tab on the T/R blade.

W1

Okay..... by increasing the chord size helicopter is getting that extra lift which can be used at pressure altitude 6 KM above especially near Himalayas wherein winds around 17knots is very common. Maybe that extra rudder margin.....can somebody throw more light on this....

You understanding is so wrong in many ways. Its a trim tab. And mainly for T&B purpose.

I have never, nor have i ever known anyone who adjusts this "tab" for track and balance.
could you kindly point us in the direction of the applicable maintenance manual reference for doing so?
I could hope you're being sarcastic.

perhaps this is why the old ones had such a problem with cracking. Mee3 was off adjusting the track...

You can't touch it does not have any thing to do with it being a trim tab.
The old one was cracking because it was attached with rivets and they are now able to mold it in one piece with new precision mold. Still does not have anything to do with it not being a trim tab.