1977 Bell 212

[Teton Rotor]

I delivered a friends 1977 Bell 212 the other day and was checking out the SCAS system. My previous time had been in a USMC UH-1N where we had both RadAlt and Baro Alt hold and AFCS.

In the helicopter in question I noticed the SCAS did its expected job of stabilizing the flight characteristics while above 40 kts. When I switched each channel to ATTD I did not notice any difference, nor would it would it hold a heading, pitch or yaw. The console panel had no effect either. The system checked out on the ground according to checklist procedures. Any thoughts?

[hueyracer]

Are you sure you operated it right?
Sorry for asking-but sometimes it´s just "finger troubles"…

The system had a "1 or 2" flight director mode-for each pilot?

Was it operating in the right mode (e.g. "2" if you were flying from the right seat)?

The ATT itself doesn´t do much-it just "freezes" the stick, and is supposed to maintain the aircraft attitude….only the operating modes (ALT, VS, IAS, HDG…..) will do the "work"….

[albatross]

Was it a Bell AFCS which gives you attd hold but there is no alt hold , heading hold or nav function.
Basically a glorified SAS but most useful for IFR.
Or was it a Sperry system? There was a "full Sperry" which had all the bells and whistles and the "1/2 Sperry" which was basically equal to the Bell AFCS.

There are some 212s which had a Sperry panel with all kind of options alt, hdg, nav ect but none worked and the placard that said they did not had long ago disappeared.

Long time ago but I am sure someone will be along with knowledge and truth directly.

[hueyracer]

Is this the one you´re talking about that has the two "wheels" on the panel as well?

The one "wheel" for adjusting pitch, the other one for bank?

[Ascend Charlie]

The name gives you a big hint:

SCAS = Stability Control Augmentation System. It is NOT an autopilot, all it does is give some extra stability to allow 2-pilot IFR. One to fly (with a bit of electronic help) and one to monitor the instruments.

[Teton Rotor]

Yes, I selected "Pilot" (did not have #1/#2 option) flight director. SCAS checked thru the "No Go" checklist, green lights when engaged and flew as advertised, but when each ATTD channel was engaged there was no change in flight characteristics and no associated control of the axis. I am thinking the system could be corrupted (inop) but wanted to check with regular users.

[Teton Rotor]

Yes, it is the basic Bell AFCS with pitch and roll wheels and a yaw dial. While I realize it is not an auto pilot I was surprised it would not "hold" the cyclic in a static position. Let go of the cyclic it slowly fell off center (roll right, pitched down). Checked the wheels on the panel, no difference. Also the coolie hat on the cyclic provided no difference in axis control.

[John Eacott]

While I realize it is not an auto pilot I was surprised it would not "hold" the cyclic in a static position. Let go of the cyclic it slowly fell off center (roll right, pitched down). Checked the wheels on the panel, no difference. Also the coolie hat on the cyclic provided no difference in axis control.

Did you have the force trim switched on?

[hueyracer]

That was exactly my thought as well the moment i read this…

:D

[Boudreaux Bob]

Adding Friction to the Cyclic is also a "Must". On the Sperry system there is a preset minimum Friction.

A question....in ATT Mode....did the two trim wheels get a reaction when moved back and forth? Did the Turn Knob....push and turn....left and right...get a reaction?

When the system is operating correctly in ATT mode...you can "fly" the machine with those control "Wheels" and Turn Knob.

Force Trim must be on as I recall.....and Trim Release not depressed.

The Attitude Reference can be re-set by means of the Force Trim Release and moving the Cyclic to the desired position....and re-engaging the Force Trim by letting go of the Force Trim Release Button.

As indicated by others....the SCAS will "hold" a selected Attitude with minor adjustments being made with the two Trim Wheels and Turns being made by use of the Turn Knob. Major changes in Attitude Reference requires the use of the Cyclic and Force Trim Release.

[Teton Rotor]

OK, now we getting somewhere. In the cockpit there was an abbreviated checklist and prior to take off two items that surprised me: SCAS-On, Force Trim-Off. Earlier in checklist it had Cyclic Friction-Off.

Now reviewing the AFM checklist does have Force Trim On prior to take off but nothing addressing Cyclic Trim to be set to any amount of friction.

So for normal ops: Force Trim-On and a medium amount of Cyclic Friction. On the cyclic I have both a Force Trim button and an AFCS release button (the same thing as Control Wheel Steering on fixed wing?), push, reset attitude, release and it will hold new attitude?

[Boudreaux Bob]

You got it!

Friction dampens any PIO from vibrations and other movements of the aircraft. Force Trim-ON sets an Attitude Datum until you over ride it by depressing the Force Trim Button and moving the cyclic. Set the Cyclic position you want, let go of the Stick Button and let the SCAS do the work.

Make your minor adjustments using the Pitch and Roll Trim Wheels.

Turns can be made by pushing and Turning the Turn Knob.

In SAS mode the SCAS will only "stabilize" the aircraft but not "Hold" an Attitude.

[Teton Rotor]

Outstanding, thanks to BB and the others on this thread. A/C will not vome out of annual until late August, will let you know.

[Boudreaux Bob]

Try this Download.


http://www.aavnc-school.com/ftd/rftb/212/bht-212-ifr-fm-1-03.pdf

This is good as a reference but of course your Aircraft should have the most up to date RFM with all the pertinent Supplements and Updates.

As you read down through the Checklist Items you will see where it states FORCE TRIM-ON and Cover Down.

It also states Cyclic Friction-As Desired (Add just enough that you can feel a small bit of resistance to movement)

Later on it takes you through the Functional Check of the SCAS.

[Reely340]

"Boudreaux Bob voted #1 resaon for misspent company time" :ok:

Thanks a lot for that upload Bob, made a very good reading during uhmm, extended lunch break. Although I - as a newbie (Hu269 only) - did not get the effective difference between AFCS and SCAS in flight. From reading the preflight checks they seem to be "either or". :suspect:
The wording regarding AFCS while on the ground insinuates that AFCS is an mathematically integrating closed loop, slightly adding control input as long as the AFCS-perceived "desired attitude/bank" is not reached, hence the risk of it maneuvering the controls to their respective stop when active while on the ground. That sounds like automatically held attitude to me.:8

I'd like to find out what pure SCAS mode (AFCS off) is doing for the pilot.
You don't happen to have a Bell AFCS/SCAS training manual/behind the scenes documentation you could upload :E

TIA
P.

[Ascend Charlie]

For an autopilot to work, the force trim has to be ON, or else the A/P has no "grip" on the cyclic. It would be trying to make inputs, but without force trim, there is no connection to the stick.

Cyclic friction makes it harder for the A/P to move the stick, so I always set the cyclic friction OFF.

[Shawn Coyle]

For any AFCS (in the broader sense of the word), to work, the Force Trim must be on, or the actuator will move the cyclic in the cockpit instead of the mechanics downstream to the rotor head.
I've never had any difficulty flying with force trim on all the time even in OH-58A/C or Bell 212. Wish the Jet ranger had it as basic kit, and we'd avoid a lot of later problems adapting to more complex machines.

[212man]

I've never had any difficulty flying with force trim on all the time even in OH-58A/C or Bell 212. Wish the Jet ranger had it as basic kit, and we'd avoid a lot of later problems adapting to more complex machines.

Quite! See my SNS EC-155 comments...

[Teton Rotor]

OK, have been off the grid for a couple of weeks since I brought the 212 down from Sandpoint.
First, Bob thanks for the link to the Manual. The full Bell checklist is better than my NATOPS.
Second, while I understand Force Trim-On in flight mode, it makes implicit sense and I did not understand why FC-OFF was in the checklist, I have to ask why do you want some light cyclic friction... doesn't that just make AFCS work harder? Or is the AFCS working "behind" the cyclic?
Third, I understand there is no collective friction in this setup, but in flat pitch to hover the collective movement is "sticky", it is difficult to make a slow smooth pull. Is that normal for this configuration?
Fourth, any scoop or tricks to filling the port aux fuel tank faster than slow gravity feed?

Thanks for the assist. Richard

[John Eacott]

Second, while I understand Force Trim-On in flight mode, it makes implicit sense and I did not understand why FC-OFF was in the checklist, I have to ask why do you want some light cyclic friction... doesn't that just make AFCS work harder? Or is the AFCS working "behind" the cyclic?

Light friction is always a matter of choice to suit flying FT off, whatever the machine. The AFCS is doing just as you say, working 'behind' the cyclic to move the jacks. It doesn't move the cyclic.


Third, I understand there is no collective friction in this setup, but in flat pitch to hover the collective movement is "sticky", it is difficult to make a slow smooth pull. Is that normal for this configuration?

No: I'd suggest that either the collective friction is on too tight or the collective control run needs some maintenance. When you say "there is no collective friction in this setup" have you inadvertently forgotten the normal collective friction further down the stick from the twist grips?


Fourth, any scoop or tricks to filling the port aux fuel tank faster than slow gravity feed?

The port aux tank is effectively waiting for the fuel to work its way across from the stbd filler point. Unless you can find a bit of sloping ground to raise the stbd side, or even use the ground handling wheel on the stbd side, it will be a slow fill. Don't forget to open the interconnect ;)

[albatross]

Re fueling:
Opening the interconnect helps a bit.

Also there must be minimum collective friction as per the maint. manual.
Bell AFCS does not interface with collective.
It is only Pitch, Roll and Yaw.

[fijdor]

Maybe I am mixed up in between the B205 and 212 but the fact of opening the Interconnect valve won't do much, the fuel comes in from the 3 rear fuel tanks and goes in the 2 forward tanks (lower)until they are full and then fills up the rear tanks. As long as you have fuel in the 3 rear tanks, they will feed the 2 front tanks interconnect or not. Again unless i have got my systems mixed up.

Also doesn't make no difference if you lift the right side, by the time the fuel gets close to the opening, fuel will be coming out from the left fuel tank vent to start and you can only go as fast as the air comes out of the aux tanks or any tanks when it gets there. If it's way too slow, check your vents.

I have been known to be wrong once in a while though.

JD

[Teton Rotor]

Thanks John, greatly appreciated.

[oleary]

For any AFCS (in the broader sense of the word), to work, the Force Trim must be on, or the actuator will move the cyclic in the cockpit instead of the mechanics downstream to the rotor head.

Dunno about that. You can fly the 61 beeper trim on or off and AFCS still works. Same on the 76A.

And if you really want to see a goofy attitude retention system try the 214ST - truly bizarre.

[oleary]

Second, while I understand Force Trim-On in flight mode, it makes implicit sense and I did not understand why FC-OFF was in the checklist, I have to ask why do you want some light cyclic friction... doesn't that just make AFCS work harder? Or is the AFCS working "behind" the cyclic?

Yes, with the Bell IFR package there is a collar installed above the cyclic friction to insure minimum friction. Pain in the ass because I like a light cyclic, but there ya go.

Third, I understand there is no collective friction in this setup, but in flat pitch to hover the collective movement is "sticky", it is difficult to make a slow smooth pull. Is that normal for this configuration?

Dirty collective friction (under the co-pilot's seat). Old problem.

Fourth, any scoop or tricks to filling the port aux fuel tank faster than slow gravity feed?

Nope, go for lunch, it's gonna take a while. Opening in the interconnect does absolutely nothing to speed it up. Some folks (214B guys) would remove the top cap and dump fuel straight in. We didn't do that on IFR ops.

[Drifter1980]

Hi to all and thanks in advance to all the answers,

Imagine that you take off with afcs off, and in flight you turn it on, put it in modes scas, and way before you land turn it off again.
Is it possible that the initial centered cyclic position when you took off, is changed because of turn it on and off in flight and the actuators and/or transducers are in a different position, and when you are landing just short after taking off, the cyclic are well off centered position, making you having your cyclic in an almost limit stop?

[Drifter1980]

Hello everybody,
Come on, does anybody have some experience related with this?
Mechanics and pilot... Come on!
Best regards to all.

[stacey_s]

If I remember rightly, SCAS Actuators (Hydro-Electric) will center when either electrical or hydraulic power is removed from them, not sure about Sperry electrical Actuators though.

S

[Drifter1980]

I had an experience with a 412 that I was flying always with AFCS off. One time, in maintenance flight, checking all the equipments, i only turn it on while flying, and because I already had a bad experience while on Scas and hovering, (That was that the AFCS on SCAS mode and with no force trim on starting kicking inputs, and had to switch it off), this time I turn it all off before landing.
Next couple of days, i had a flight, and I noticed in hovering with no conditions that should experience this, my cyclic was almost on the left limit position.
I reported that to the other guy that replaced me. I didn't had the chance to talk to him at that time but he solved it, and I think it was only by turn it all on on the ground.( when I managed to talk to him, some time had passed and he didn't remember of that).
So I'm still not exactly sure how this specific situation can or not work.
The B212 is slighty different but the principle should be the same, I suppose...
Thanks for the answer Stacey...

[Brent 1]

There are three types of afcs that I have worked on which one do you have? SI 54 SI 65 or 53 or similar with collective cyclic tail rotor interchange How is your maintenance done? Do you have an engineer who knows anything about afcs? do you have access to ground power and a hydraulic rig? If so the answer is to work through the checks. By the way glad to see you are still well Stace.