AS350B3 VERT FIN STRAKE?

[greenvalley]

Looking for some info on the difference between the long and short vertical fin strakes on the AS350B3? Aerodynamic differences between the two? And this is why..............

Recently had to have the tail chaged on a b3 due to bulging and cracking at the base of the left side of the vert fin Eurocopter said it was most likely due to improper riveting? The tail has been repaired multiple times withing the last year for the same problem. Mind you this is an EMS ship that really only flys straight and level.

Our vert fin was equipped with a full length strake, which i have never seen before on a b3. Could this have had some influence on the cracking and bulging of the metal on the fin?

We now have the short strake along with a new fin.

Thanks everyone!

[Firepilot]

There was an SB that came out in 2007 (Revised in 09) regarding the modification to the strake. http://www.eurocopter.com/techpub/doc_upl/SBAS350550014ENREV1.pdf

I was told it was partially due to cracking at the base/ attachment points of the upper vertical fin to the tailboom. The reasoning in the SB is:

" To:
- improve vertical fin's aerodynamic efficiency in order to increase yaw control margins in autorotation at airspeeds in excess of 100 Kts (MOD 073148),
- advise customers having equipped aircraft with vertical fins post-MOD 073148 that they must embody they ollowing modifications:
. MOD 073158 in order to restore yaw control margins,
. MOD 073169 in order to suppress the risk of interference between bearing
No. 5 of yaw control rod and a bolt of the load compensator,
. MOD 073205 in order to avoid end-of-travel abutment of tail servo-control during yaw control pitch adjustment.
If aircraft is equipped with AFCS, the following modifications must also be embodied:
. MOD 073170 in order to suppress the risk of interference between the rod
located downstream of the series actuator and the airframe (aircraft
equipped with AFCS only),
. MOD 073282 in order to restore minimum clearance between the new fool-
proofing device of the lever and the rod end, during flying control motion
towards low pitch (in yaw)."

We modded all of our aircraft when the SB came out and haven't had any issues since.

Hopefully the link works. It's a direct link from Eurocopter's TIPI site.

[victor papa]

The full length was fitted to the original B3 and the halve length came in with the B3+. it is aerodynamic differences between the 2 caused by the engine performance difference amongst a few other things. On the old b3 you had the stinger on the LH horisontal stabiliser as well and later you could remove it as part of a SB and cut the full length stinger in halve to gain VNE. Cant remember all the differences. On the B2 we had the stinger along the tailboom which neither B3 has-straight exhausts due residual thrust is my guess????

The B3e has got a suttle difference or 2 again. best make sure your machine has the correct configuration iaw the SB's and individual mod statusses as you can not just change the stinger.

[greenvalley]

Thanks firepilot! Our maint guys have complied with the SB after installing the the new fin and short strake. Hopefully this does indeed solve the cracking problem. Time will tell!

Thanks again!