B212 "Fast Fin" & tail-boom strakes

[Bernouli's what?]

I've seen the ads in the mags (I'm not a spotter, honestly!) but I'm curious to know if the product lives up to the hype.
The claims are of up to 1000lbs increase in payload, which we'd find pretty handy, but does anyone out there have any practical experience of this kit with positive or negative feedback? What's the cost per aircraft and is it a simple fit?
No company salesmen, thanks, I don't hold the purse strings (not even my own!)

[outhouse]

Cracks in the tail boom seem to come to mind with the strakes fitted.

outhouse

[ericferret]

Aren't BLR currently sueing Bell for incorporating this technology on the Bell 429 and infringing their patents.

If it doesn't work why are Bell using it or a variation?

[BlenderPilot]

Airlogistics has a pretty big contract here in Mexico, it involves something like 10 Bell 412's do do powerline patrol, construction, and other emergency duties when required, AND THEY HAVE MADE IT MANDATORY TO HAVE TAIL BOOM STRAKES ON ALL THEIR AIRCRAFT, at least here at altitude it makes a difference, as I doubt that the largest helicotepter company in the world would go to all the trouble of installing these if there was no difference.

[jab]

Nick

I believe this is the first time I have ever thought to disagree with you, even if not completely.

I don't know about a 1000 pound increase but I would not rule it out. My experience has only been with the UH-1H which I flew before, and after, strakes and fast-fin were added. I was doing fires and would run out of pedal at 48 pounds of torque (at altitude) so there were often times where I came out of the dipsite doing hover turns until I could get some speed to get the tail back in line.

After the strakes and fast-fin were added, I never ran out of tail rotor and as a result could lift a bit smoother using less pedal. That was operating at 10 000 feet in Utah. If the tail rotor is using less power, then there is more available to the main rotor so it should be able to lift more. They do make a difference and the 1000 pounds increase is not beyond the realms of credibility. I suspect more like 600 pounds but I have nothing to back that up with except what I felt in the helicopter.

[Matthew Parsons]

There are some benefits to this modification and some hype. Until I get around to testing it, I can't say what is a real benefit and what is hype. I do know that your tail rotor pedal margins are increased at high power settings. That enables you to lift more.

The 1000lbs would not be entirely from reducing tail rotor thrust by 1000lbs, but it may be that you approach maximum tail rotor pedal margins with 1000lbs extra weight, for a certain weight/altitude/temperature.

There are a number of helicopters around the world that are being built with strakes or are having strakes installed. I don't know anything about the popularity about the fast fin or similiar designs. It does make you think that the strakes do offer some advantage, but determining what that advantage is and whether you'd be able to use it in your operation is paramount.

Matthew.

[mfriskel]

Take a little 1960s tail design, add some 1980's aerodynamics testing, cut some airflow blockage from the supporting metal for the tail rotor- performance improvement by reducing tail rotor thrust requirement. Might not be a full 1000 pounds, but is definatly a good amount. It seems to give better payoff at higher DA, were the engine is the limiter and not the transmission.
When I worked at MDHI we made some pretty good gains with small bits of metal and a few inches of somposite tube. The claims do not surprise me at all.

[Brian Abraham]

Cracks in the tail boom seem to come to mind with the strakes fitted
Not just with strakes, which I know nothing about. 205/212 tailbooms were always in the shop being reskinned, and I don't mean that to be an archilles heel in the helo, just a reflection of the stress the boom is subject to. Could always build it out of boiler plate I guess, but the CofG may be a bit out of whack. ;)

[ericferret]

Come to think of it the 139 has a large strake down the left hand side of the boom.
So Agusta must think it works as well.

Mind you it also had a 7 inch crack through the boom skin originating around one of the strake fasteners.

[Shawn Coyle]

As far as I know, the strake first appeared on Westland Sea Kings in the Falklands crisis in 1982. It was a single strake, and resulted in improved tail rotor margins with a right side wind (encountered often when the helicopter was moving to the right to land on a deck). US Navy testing on the strake was not done with a lot of rigor and they didn't adapt it.
Later, NASA did some more work on a UH-1H and found that two strakes were better, and patented the idea. BLR picked up the patent and ran with it.
The main improvement is an improvement in tail rotor margin with a right side wind, and a reduction in pedal activity in the hover. Any improvement in payload due solely to the strake was only applicable in the right side wind condition, and this is where the advertising has been emphasized.
The Fast Fin is a beast I know little about technically, but it's obvious that it will improve the efficiency of the tail rotor to produce side thrust. That's going to reduce the power drain of the tail rotor, which might be available to the main rotor, but not to the point of a 1,000 pound increase, except possibly in a very specific set of circumstances.
Hover performance for civil helicopters is normally only presented for two conditions - an IGE hover determined using a fixed collective takeoff, and an OGE hover. Both charts assume takeoff power at the limiting conditions.
If these two devices in combination really did improve the payload that much, you would see different performance charts with the modification. I don't believe there are any new performance charts produced.
I had a short chat with a person intimately involved with the testing of these devices and he intimated that the difference in power required in the hover was closer to 2-3%, but nowhere near 1,000 pounds in payload.

[spinwing]

Brian.....

Over the years I have been flying the 212 and particularly the 412 I also have noticed that those tailbooms have required alot of re-work.

I wonder if in fact the tailboom strakes will allow for more "smoother" yaw control and effectively reduce the stress on those booms by eliminating the airflow breakaways and thus the sudden excursions which must put much extra stress on the boom as we correct them????

Mmmm :confused:

[3top]

Shawn,

a couple issues ago Rotor&Wing did a piece on BLR, the strakes and the Fastfin.

BLR is supposedly working on the legal requirements to be able to issue new performance charts for their STCs.....

.....according to R&W.


3top:cool:

[Lama Bear]

Six seasons in Mexico flying UH-1H's with and without the strake. They are worth the money! We had no tailboom cracking. AS355-F1 without strake on fires, it was common to be very near full pedal travel. Flying a B-2 at the same aircraft weight with a strake, T/R authority was never an issue. If you are operating hot and high I would recommend buying them.