Re: [Flightgear-devel] UAV Heli and Matlab

[Arnt K. <ar...@c2...>]

On Wed, 14 Jun 2006 11:57:39 +0200, Georg wrote in message 
<448...@ar...>:

> Melchior FRANZ schrieb:
> > * Georg Vollnhals -- Wednesday 14 June 2006 03:02:
> >> Take the BO105 and goo for a straight and level flight with 100-120
> > > knts. Then push the collective down. [...]
> >> Try it with the BO105 - see what happens?
> >> You are not only able to hold height with pulling the stick back
> >but to  > climb with up to 1500 ft/min until speed is low.
> > 
> > That's "translational lift". You know, the thing people are claiming
> > isn't implemented. :-}  It's not realistic (as Maik himself says),
> No. Translational list is an additional lift component related to 
> helicopter speed against the air and will start at about 12 to 20 knts
>  (depending on type of helo). This is a real big addition lift
>  component 
>    together with (an unwished) roll and yaw component.
> > but I'm not sure about the "dropping like a stone" thing. Normally,
> > people compare a fully loaded real helicopter (because they are
> > sitting in them as passengers together with several other people)
> > with an unloaded sim helicopter. Put more weight into the bo, and it
> > sinks faster, as one would expect in RL.
> > 
> > m.
> "falling like a stone" might be the wrong expression but was told me
> by  a RL pilot and demonstrated afterwards in a "hot" autorotation for
> a  short time from 2000 to 1000 ft. It is pretty impressive and the 
> vertical speed naturally depends on the type and configuration (ie 
> weight) of the helo that you fly, our BK117 should come up to more
> than  2000 ft/min, a BO105 will be have some other numbers but
> generally  comparable.
> You understand what one is doing when reducing collective? You reduce 
> the common blade-pitch angle to (nearly) zero (depending on the type
> of  helo you are flying). Of course, going into a heavy flare will
> give you  some lift for a short time until your horizontal kinetic
> energy (speed)  is reduced. But when I asked one of our experienced RL
> pilots 

..define "experienced."  We need somebody experienced in autorotation,
and these guys are rare and expensive.

> about this scenario and what would happen, he told me that he could
> (if ever) hold  altitude for a *very* short time by pitching back but
> could not make the  bird ascend remarkably (what our FG helo does).
> 
> OK, after all I want to say once again that I am not the real expert
> for  this, we should have an *experienced RL helo pilot* who is also 
> interested in flightsims to tell us what he thinks in general and
> detail about our FDM.
> But as I was very keen to learn all about helicopter flight behaviour 
> and technics and comparing different helo sim flightmodels by checking
>  the opinion of RL helo pilots I *just want to share* all I know with 
> you. People simply should be advised that there are very diffent views
>  regarding the actual helo FDM.
> 
> I would feel pretty bad if we announce our helo FDM as "realistic" as
> we  have some nice fixed wing aircraft with "real life pilots and a/c 
> owners" approved flightdynamics, this would be bad for FG in common.
> 
> Just my 2c, this discussion will probably never end :-)



-- 
..med vennlig hilsen = with Kind Regards from Arnt... ;o)
...with a number of polar bear hunters in his ancestry...
  Scenarios always come in sets of three: 
  best case, worst case, and just in case.