Bell 212 Tail Boom Strakes
 

I would appreciate some inputs, from pilots with experience on them, on the benefit(s) of these strakes, with regard to Stability & Performance improvements, both HIGE & HOGE

They help on the UH-1H. It's difficult to quantify but I don't run out of pedal near as much as before the strake.

Helix, I don't know about the 212 but the Sea King had a strake welded to the port side of the tail boom to stop the rotor downwash producing lift on that side in a right crosswind. The strake slows down the air by breaking up the boundary layer and equalising the speed of the rotor downwash on both side of the tail boom. Running out of left pedal in a right crosswind was a regular occurence before the strake was added but now it's good for a 30 kt crosswind.

showing my ignorance of aerodynamics here . Does the strake have the effect to change the coriolis effect of the downwash over the tailboom ?. On Eurocopter models the B2 has them on the same side as the tail rotor but not the BA and B3 . On the 212 is the strake on the opposite side as well ? I recall an old article in r and w need to dig it out.

http://techreports.larc.nasa.gov/ltr...-93-tp3278.pdf

Link added , in nasa test strakes were at 2 o clock and 4 o clock position , on 350 strake at 3 o clock position

We have the strakes fitted to all our 205's. The effect is great, you really do need 50% less pedal input. You will probably notice it on the approach to hover when you suddenly realize that you've hardly moved your feet at all throughout the manoever.

I think the B3 is the only one fitted with strakes, I've flown B, BA and B" and they didn't have them.

Apparantly they are working on strakes for the 206 aswell, now that should really make a difference:)

Also the
 

Agusta K2 is fitted with strakes from the factory.

Widgeon, I think you mean Coanda effect not Coriolis. Coanda is the effect utilised by Notar technology where an injection of air onto one side of a structure (wing, tailboom etc) delays separation of the airflow and increases lift. Coriolis was a French physicist (i'm almost certain) who explained the apparent deflection to the right of an object moving in the Northern Hemipshere.

Thanks Crab me knowledge of Physics is nearly as great as that of aerodynamics . It was Coanda I was thinking of where air flowing over a tube causes lift.
Next question is the effect greater on a circular section boom ( 105 , 117 ,350) or a more square section ( UH1 , Dauphin etc ).

Ok... low timer input here...

I'm assuming any 'lift' effect would increase proportionately with the size of the lift surface (or boom)?

And would this effect even be noticeable on the tiddly 22's I get to fly (whenever the bank account can take it)?

Andy

Crabbo,

The NASA designed tail boom strake on UH-1 and now 212 series is almost identical to that in the Wastelands SK4.

Never flew the SK4 before the strake (assuming it wasnt a design fit?) but have flown the Huey before and after. The effect is significant esp at high DA....ie: tropics/mountains.
Also important is that in auto-rotation (with relative wind from 10-11 o'clock) there is an increased chance of encountering full right pedal.

I know this is obvious, just info for interested parties.


"Fear God Honour the King"

Handyandy, I think it is the amount of air energizing the boundary layer on the Notar-type blown slot that determines the lift created. I believe there was an experimental rotor with round blades and a blown slot that produced lift coefficients of nearly 4 (That is a lot Widgeon(tongue in cheek)). The downwash effect alone on a tail boom as spindly as a robbo(are you sure you wouldn't rather save harder and fly a 206?) would be negligible IMO.

Tone - a good point about the autos - when you airtest a Sea King you have to be able to yaw the ac right through 90 degrees in a 70 kt auto to prove the rigging of the TR.

Crab , I have 2 formulas I never forget 1/2 roh v squared S and M/I = F/Y = E/R . Just wish I could remember how to use em LOL.

Bell 212 Autopilots
 

Just wondering if any Ppruners have experience with B212 Autopilots. I am particularly intrested in any "single pilot IFR" certified systems (usually three axis).

I am told that Bristows used to fly a three axis autopilot in thier 212s, and may have even been involved in the design/certification.
Does any one have any experience with these?
Are they reliable, or are there lots of black box problems?
Are they "one offs" or are they likely to be supportable in terms of parts, actuators, etc?
Do they get in the way of lifting jobs (like the SCAS system does)?
Are they a heavy system?

Any technical or anecdotal info welcome.

Thanks, hf

Bristow did in fact have three axis autopilots....Bell Scas...Sperry Helipilots....and that wonderful French piece of crap SFENA. Helipilots by far the better of the three....although when the Bell SCAS was tuned and working right...it was very handy. On the North Sea, the machines had the coupled Flight Director for the Sperry which makes for a very nice setup. Upon being dispatched to Nigeria and other parts of the world....the Coupled Flight Director modules were removed (afterall who is going to pay for them old chap?).

You might seek "212man's" input.....although he is now the EC-155 TRE for Bristow....he might help you out a bit. The best source of info would be Peter Barnes, who was exiled to Scatsta upon falling from grace with the BHL management. He was the Senior Type training captain on the 212 for years and is a very professional pilot. Bob Jones, ex-BHL, now with the CAA would be another good source of information.

The Royal Brunei Air Force certainly found the Sperry system to be superb. Unfortunately they (the Sperry systems...) are now obsolete. 3-axis and generally very reliable in the hot/humid Borneo conditions, they were better than the Chinook 4-axis system in use at the time. However, you wouldn't want the a/c in AP mode when doing any hover or lifting work (I think the min IAS was 40 kts anyway...).

Thanks heaps so far. I am away for a few days now, so forgive the lack of prompt replies.

2 quick extras:

What is the problem with the SFENA?
Were any of the systems certified for SPIFR?

What is the problem with the SFENA?
 

We had the SFENA (I thought it was SFIM?) machine in the Brent Field for a short period. IIRC, it was G-BARJ, but the enduring problem was the system tripping off line in the slightest bit of turbulence. With rig shuttles, and a landing every 5 minutes or so, we eventually put a 2nd pilot in, to reset the SFENA when it tripped, usually on approach :rolleyes:

The French finally sent over a team to look at the problem, but, surprisingly, it "was not our fault. Your engineers have set the aircraft up so that our magnificent system cannot possibly manage".

About a month after we foisted the 212 onto another operation, the French provided a fix for the problem, which wasn't their fault, either.........;)

FWIW, this was the aircraft that was trumpeted, with much publicity, as the first SPIFR 212 to be developed.

As I heard it John.....the SFENA or SFIM as you will, was originally designed for the Mirage or some sort of fixed wing. It did have an altitude hold feature...which neither of the other two systems did. My recollection of the useless piece of kit was the unpleasant thrill one got when engaging the altitude hold mode.....at some point the aircraft either tried to pitch up and over onto its back or nose over and stick the nose into the dirt....which in a Bell can sometimes become very interesting. I dare say the quality of greenie support in Nigeria did add to the situation as did the lack of spare parts. I usually just left the SFENA in the "OFF" mode....and hand wrestled the bird. At least my blood pressure and heart rate remained somewhat more regular that way.

SASless,

Brunei B212s with Sperry most definitlely did have altitude hold (pitch function, as were RoC/D hold and glidepath/go-around modes).

Bell 212 type rating/check
 

Anyone out there that knows where I can get the best deal for a B-212 type rating (JAR) or type checkout (FAA).

I may be changing jobs soon and to avoid beiing bonded for 3 years, I´m looking into paying for the check myself.

Any information on cost and time required would be greatly appreciated.

I´m not to sure what the flighthour requirements are in the USA, but I would need 8 hrs in Europe (JAR) if no simulator is used and the skill check is an additional 1 to 1.5 hours x many $$, which will mean that the check is to expensive for an individual to pay here in JAR country.


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