Archived from groups: alt.games.microsoft.flight-sim (
More info?)
BillW50 wrote:
> Hi boB... My first post was sort of misleading. The second post
> helped a bit I believe. But since I know RC heli terminology better
> than real heli stuff, I like to ask you some questions.
>
Hi Bill. I won't lie, it's hard to hold concentration throughout the
post but I'll try.
> Now in RC heli, collective and main rotor pitch is generally thought
> of one in the same. Oddly enough, they (in RC talk) generaly use the
> pitch statement for setting things up correctly and then switch over
> to using the term collective when it is set right. Which is a bit
> confusing if you ask me.
>
> One reason to say pitch instead of collective is that pitch can be
> negative, while I've never heard of collective of being so. Have you?
> This is useful for inverted and 3D flying in RC flying by the way.
"Collective pitch" is a correct term when teaching any maneuver which
requires movement of the collective. ie Autorotation or fixed pedal
emergencies to remember a couple.
When replacing rotor blades the test pilot had to place the PC Links at
a nominal setting to begin with. The aircraft is run-up and the blade
tracking is checked along with making sure the torque is showing
correctly for a rotor system at flat pitch. There is just a tiny bit of
negative pitch at the root of the rotor blades but it's inconsequential.
The real test is after all the work is done and the test pilot has had
his midday snack, (Pot of coffee and a bowl of cigarettes) the aircraft
is flown to check for vibrations and more important, where the rotor RPM
settles when the throttle is cut, collective down, flat pitch.
You can imagine, flat pitch where there is too much pitch in the blades
will cause the rotor RPM to decay after an engine failure. Most pilots
wouldn't like that. On the other hand, if the RPM increases at flat
pitch it can cause other, sometimes worse problems.
>
> Although in RC talk, the pitch (collective) is mixed together as one
> in what RC talk calls normal mode. And in normal mode we see a curve
> with both throttle and collective (with computerized transmitters
> anyway). And we can change that curve as well if we want to.
>
> But in 3D mode, meaning that the main blades can move both positive
> and negative (positive and negative collective), we keep the throttle
> pretty much constant (the throttle control is now mostly turned into
> a collecive control) and just change the pitch of the main rotor
> blades. Well not exactly, as we still use the curve and mixing to
> adjust. But anywhere besides zero or near zero on the pitch, the
> throttle is pretty much set at some premium RPM value. That's the
> default, although you can change it of course.
Sorry Bill, my brain won't comprehend that paragraph. I'll keep reading
it until I get it. Someone a few messages ago stated correctly that
throttle is maintained with a governor and collective movements do the
pitch changing. The governor holds the RPM constant.
>
> So are you following me so far? If so, how is this different from
> what you know?
>
> Bill
>
>
I hope I got most of it.
An after-thought. I commented some time
ago that the sim helicopter has a bad problem with the pitch settings.
Lowering the collective full down after shutting the engine down will
cause the rotor RPM to decay. To maintain proper rotor RPM requires a
small increase of the collective.
--
boB
U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)
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