Bell 206: JetRanger and LongRanger

[Saint Jack]

TQ Gauge Fluctuating Question

Super F is absolutely correct, don't pull it (the collective) aggressively - why do you? Similarly, go gently with the cyclic - smooth movements will greatly reduce the wear and tear on linkages, mounts and the airframe in general.


Having said that, the problems detailed by both Bell_Flyer and fokkerpilot are broadly similar and, as mentioned by others, the first thing to look at is the N2 rigging (provided the arm on the FCU is making firm contact with the max power stop it's unlikely that N1 rigging is the problem) One important point of N2 rigging is that the arm on the PTG must not touch either stop with the collective full down and beeped down or full up and beeped up. Check that the entire N2 control linkage is free of excessive backlash, replace any defective part/s.


Next, look for will be loose pneumatic lines on the engine, check for tightness and, if necessary, check the flares for cracks. Remember that pipe flares should align properly with the mating fitting - you're allowed to bend the pipe (gently) to ensure proper seating - a misaligned pipe is a strong candidate for cracking at the flare.


Following that, the next step should be to remove, check and clean the P3 filter. Also, as RVDT said, the PTG can get dirty and on some P/N's you can remove the Px and Py bleed orifices for cleaning - this is a very simple procedure but do one at a time to prevent mix-up.


If you find the Px and Py bleed orifices are dirty and the P3 filter requires cleaning and the engine is sometimes slow/difficult to start, then there's a
high probability the FCU start de-rich bellows bleed orifice also requires cleaning. Note that this is only possible on some FCU P/N's - check the MM.

[vfr440]

Px/Py & FCU/PTG

I thought that Px & Py bleeds were installed in the FCU, NOT the PTG. They absolutely are!)................ (But absolutely right to do them one at a time - given which I have never had any quantifiable improvement in doing so. Such a hassle to remove the FCU in the first place) I checked my reference manuals, and my 'experience notes' and stand by this statement (!) - VFR

[FH1100 Pilot]

If Bell Flyer were in a 206B I would say his problem is a bad (what the mechanics call a) "double-check-valve." Since I'm not sure the C30 has such a device I will not suggest that's it, but any time I've gotten such torque fluctuations in a C20 it was the double-check-valve going bad.

[Saint Jack]

TQ Gauge Fluctuating Question

vfr440 is absolutely correct that the Px and Py bleeds are in the FCU, my mistake - I haven't worked on this engine for some time. But I do remember removing and cleaning a bleed orifice (Pg?) on the PTG and that it can be done without removing the PTG from the engine - check the engine MM. Similarly, cleaning the double check valve, as suggested by FH1100 Pilot is a simple task but it has to be removed from the engine.


My reference to the P3 filter was also incorrect, it should of course be the Pc filter.


Bell_Flyer and fokkerpilot : let us know the outcome of your troubleshooting so that we can all learn.

[Washeduprotorgypsy]

Just listening inattentively in the back benches here.......

But the topic reminded me of a tour from hell in a remote area with a newly acquired bucking bronc of an L3.......

First of all is the torque fluction REAL and ACTUAL, that is; felt in the seat of the pants by way of yaw, heard, and correlated by a bouncing nr gauge?

Or is it just the torque gauge itself bobbing up and down 10 percent or so?

If you think it's ACTUAL. Start with the easy stuff mentioned so far PTG, FCU. But on the c30 don't rule out the combustion liner can. Yup, the combustion liner. Had very similar actual torque bob with a beat of about 40-50 beats a min.
Changed out parts willy nilly and low and behold it was the combustion can had shifted minutely causing a surging flame pattern.

If it's just the torque gauge and all the air has been bled from the system repeatedly then hate to say could be a gearbox issue with torquemeter system hydraulic issues.
Good luck

[RVDT]

DC valve is only fitted/required on the 206 Series from memory (fading a bit as haven't worked on one for about 20 years - FADEC these days!)
and it is there to stop the PTG reacting to the torque fluctuation inherent in the 2 blade rotor.

[Saint Jack]

TQ Gauge Fluctuating Question

RVDT I too seem to have a failing memory, mine is telling me that the second accumulator was an addition to the 206 engine installation to dampen out torque fluctuations. The 206 configuration being and accumulator on both sides of the double check valve.

[vfr440]

Nice one!

Hey Washed up (love the handle!)
Your recall is better than mine, NOW I remember about the C30 liner(!), though I never encountered a snag which required such action. Nice one There was also a requirement to monitor/retain the shims under the fuel nozzle too, but can't remember why - starting problems maybe?


Cheers - VFR

[Washeduprotorgypsy]

Thank yuh, thank yuh very much. Hey what are pprune noobs for?

In interest of furthering the "Alzheimer's support group" or God forbid the "pass it on" spirit. I'll chime in again.

Fuel nozzle shimming in regards to torque surging , mmmmm I dunno? But it definitely makes the difference between a fizzle-Boom! and a symphony at light off during starting.

In regards to the suspect combustion liner, it's getting pretty foggy but I do remember upon removal there were no visible cracks, defects, oxidation marks to differentiate it from a healthy liner. Well by having a quick look anyways. Lots of unseen black magic going on in there with temps, press, flow conditions and contraction, expansion so it's not completely surprising a liner could be the offending culprit.

Somebody mentioned pulling the collective fast. I d say when acquainting yourself with an unknown unproven machine definetly a good idea to "pop the clutch" and shoot a couple of power recovery autos. Just to be sure when you re flittering around in the hills and your judgement comes up a little short the power doesn't. Lots of unseen parts holding your ass in the air, and component duds never get passed around. Always nice to know the compressor, bleed valve, FCU,PTG, rigging etc. Etc . Are all up to the acceleration task before
Loading the station wagon up with the kids.

That's all I got. Happy flying.

[Carbonok]

Help please!

Hi guys.
First, very sorry for barging in here...
I've been looking for B206 drawings showing the early fully faired U/C legs and straight topped pop out float skids, like the JR in 'The Spy who Loved Me' and many others in this thread (thanks for the pictures all of you).
I'm a modeller and have longed for a really scale Jetranger for quite a while.
I first wrote to Corgi in about 1974 asking them to make one.
They did, but even as a 9 year old I could see the flaws.
See the 'Stromberg' and 'Chopper Squad' Corgi toys.
Now, in 2015, I have a really good fuselage and flybarless chassis with the T/R on the port side. Yes, this one will fly.
The windscreen is pretty accurate but the 'snout' needs a little work.
The professional modellers (plastic/ die cast) don't often get these shapes right.
I have not yet found a drawing showing the older high skids, nor a photo' that I can scale from (I need a straight on side and front view).
By now you must be bored!
After all there are many superb scale JR models out there.
However this one will be just 12'' long.
It will be as true to scale as I can make it (with your help!) and will fly in my lounge.
Once again, please help!
Many thanks and kind regards.

[206Fan]

Air Ocean (Connecticut)!

[Carbonok]

Scale 206

Thanks for your reply, superb inspiration.
Anyone else offering a great (blue if possible) paint scheme for a high skid early model?
3 views still most welcome.

Thanks and regards.

Carbonok.

[Panev]

Gurney flap on horizontal stabilizer on Bell 206 B3

Hi everyone.
I was wondering if anyone has a good explanation why there is a gurney flap installed on the leading edge of the upper side of horizontal stabilizer on Bell 206 B3. I think it has something with the stability in low airspeed, and that it spoils the airflow over the stabilizer during flare to prevent staying with high nose up position, but I'm not completely sure. Thanks in advance

[rotorfossil]

It prevents the tail plane applying excessive nose down pitch in autorotation by disrupting the airflow over the top of the tailplane, otherwise the rear cyclic travel would be restricted.
The tailplane is sized and configured to apply a download to keep the cabin approximately level in the cruise. The spoiler is simpler and cheaper than a moveable tailplane.

[paco]

What rotorfossil said , plus:

"The ... Gurney flap ... works by increasing pressure
on the pressure side, decreasing pressure on the
suction side, and helping the boundary layer flow stay attached all the way to
the trailing edge on the suction side. In short, the increased pressure on the
lower surface ahead of the flap means the upper surface suction can be
reduced while producing the same lift over a very wide range of positive and
negative angles of attack. For example, at one extreme, in a high-powered
climb, the negative angle of attack of a horizontal stabilizer can be as high as
-25°. In autorotation, it may be +15°.

On the 206, the Gurney flap corrects an angle of incidence problem in the
design that was too difficult to correct directly. Another reason is to induce
turbulence in autorotation, to spoil the lift and make its effect as small as
possible, otherwise the fuselage attitude would be too extreme."

Phil

[RVDT]

At the risk of being flamed I am calling BS so far -

It is not a Gurney flap otherwise it would be at the trailing edge. Its more like a fixed Krueger flap or cuff.

The story I was told is that it softens or makes the stall of the stab less abrupt.

Apparently it used to hang on a bit later than desired and stall abruptly with a sudden pitch change so Panev you could be right with your assumption.

Could also be BS as well but makes more sense than the other explanations.

Someone out knows the real answer.

[paco]

My explanation was from a Bell engineer, but you'll get a different story from each one of those as well

Phil

[wrench1]

Panev.

The piece you refer to is not a gurney flap. RVDT is correct, those flaps are only mounted on the trailing edge side. And mainly on vertical fins.

It's technically called a spoiler (per Bell documentation). The L models, 407, 222 series, etc. have slats.

Like others noted, you can get their purpose de jour depending which engineer you talk to. But its safe to say, the spoilers and slats are there to change undesirable airflow over the horizontal stab.

W1

[paco]

Spoilers do what they say, so obviously too much lift is being produced in some stage of flight.

Phil

[rotorfossil]

It's quite simple. The tailplane's primary role is to provide a downthrust in cruise flight to keep the cabin level. The upthrust from the airflow from below in autorotation is unwanted, hence the spoiler.
You can detect its effect if you enter auto gently with a fixed cyclic position. Initially the nose drops as the tailplane is unstalled in the negative sense. Then the spoiler disrupts the airflow over the top of the tailplane and the nose rises again.