Gazelle Flight Dynamics... Again.

[Scarecrow84]

Bearfoot:

 

Yeah, I'm not sure I understood what he was saying the about arcade FMs...

 

ESAc_matador:

 

Yes, I know he is comparing without SAS. I am saying that I find it hard to believe the SAS makes such a big difference regarding the stick centering during high speed flight, turns etc.

[jjohnson241]

There's a video around these boards where our Gazelle is flown upside down from landing approach to a hover, rolled then to right side up and landed.

I can perhaps understand a high speed roll in a light weight helo with the right power but I can't understand sustained inverted flight.

Right or nearly correct flight model? I don't think so.

[BronzeYardNo11]

There's a video around these boards where our Gazelle is flown upside down from landing approach to a hover, rolled then to right side up and landed.

 

And it's GOLD

[ESAc_matador]

And it's GOLD

 

If i try to do this... I cant. Is it the real module? Or is it touched?

[Robert31178]

Lol flies like a damn 3D R/C heli

[TripRodriguez]

I very well be misinformed, but I was told that what was done in that video was fixed some time ago.

 

Still hilarious!

[Rangi]

I bet no one has tried it in a real gazelle, so how do we know it's not realistic.....

 

 

 

;)

[Coxy_99]

When this module first came out yea it was hard to master we learnt its flight model, polychop changed it and made it far to easy to fly that a six year old could fly it, The only people to know and have tested it with REAL gazelle pilots is polychop let them sort it out none of us have flown a real gazelle so we may aswell stop guessing pretty sure the thread has just about dried up

[Zimmerdylan]

 

 

There must be some kind of physics that could allow for a helicopter to fly inverted. I'm not saying that it is possible for a full size aircraft to fly that way, but there is a possibility obviously that this phenomena occurred in the initial Polychop FM. I don't find it to be too bazaar.

In of course there is the Red Bull Helicopter:

https://www.youtube.com/watchv=uYbx5H5e9Es

 

I find it to be pretty amazing. I've actually seen it do more amazing stuff than this at the D.M.A.F.B. airshow in person.

 

 

Edited April 24, 2017 by Zimmerdylan

[TripRodriguez]

Well we have plenty of RC helis flying inverted to more or less prove it is possible. Not that this means absolutely that we could build a full scale heli capable of the same thing, it doesn't always work that way.

[Zimmerdylan]

Well we have plenty of RC helis flying inverted to more or less prove it is possible. Not that this means absolutely that we could build a full scale heli capable of the same thing, it doesn't always work that way.

 

Yes I understand this. But an RC aircraft is a simulation with obvious different physics, as is DCS in the way that it's physics is all coded. All I am saying is that it is very conceivable that Polychop may have accidentally programmed the same general FM as an RC plane. To me.....it's not that far fetched and would be an honest mistake as it is shown to be possible in small scale.

They must have fixed it at some point as no one seems to be able to replicate it now.

That was all that I was getting at.

[Asset]

The reasons why RC helis can go inverted are:

1) insane engine performance compared to heli weight

As everyone can see from the mission editor, the Gazelle is already overweight as soon as you add a single drop of fuel. So there isn't a lot of headroom performance wise for toying around

 

2) range of blade angle adjustment

A regular heli needs only positive blade angle, because it needs to climb. Dropping down is a job for gravity. Ir you want to go inverted negative blade angle is the new positive. And why would you build a rotor system to be able to do that? Has no place in military operations.

 

 

3) fuel system capable of negative Gs

Must be able to pump fuel, that is trying to get away from the pump. Even the A10 can only do that for a few seconds before the engines die. And getting it inverted is already built into its physics.

[TripRodriguez]

I don't think anyone was suggesting actually building such a machine. The only application would be air show stunt stuff.

 

I'm just saying it's probably not physically impossible.

[FragBum]

Ah but wait,..

 

 

 

 

Alright not exactly flying inverted. :smilewink:

 

Even broke blades going inverted in RC heli s not to mention down is good and up is expensive. :music_whistling:

[CrashO]

Alright not exactly flying inverted. :smilewink:

The Apache does pretty well inverted (when empty).

Took these myself (no, they pictures are not inverted, gravity can be seen doing its thing on the flares :D )

 

#2016 Leeuwarden, Netherlands

 

#2013 Volkel, Netherlands

[lemoen]

Those aren't really flying inverted. Doing a loop or barrel roll is cool. I think he meant actually flying inverted like a plane (which RC helis can do)

[FragBum]

The Apache does pretty well inverted (when empty).

Took these myself (no, they pictures are not inverted, gravity can be seen doing its thing on the flares :D )

 

#2016 Leeuwarden, Netherlands

 

#2013 Volkel, Netherlands

Nice must have been impressive actually being there. :thumbup:

 

Those aren't really flying inverted. Doing a loop or barrel roll is cool. I think he meant actually flying inverted like a plane (which RC helis can do)

 

I'm also not sure how you would train for it in real life. :megalol:

[FragBum]

Only because if your ham-fisted with the Gazelle you can invert it pretty easily, usually only for a very short time, at other times I've just fecked up but it doesn't fly inverted any longer either, see my sig. :music_whistling:

[shagrat]

Okay there maybe something funny going on in turns, I thought about this and how I fly the Gazelle (well I mostly miss the ground so that's a start) whilst giving the Huey some love yesterday.

 

Depending on how you turn the Gazelle it doesn't always follow the turn, I mean it does in as much as doing the turn but the authority the tail has or should have doesn't seem to be there. I just tend to correct attitude going through the turn with pedal input (I learnt to fly the Huey first so it's automatic) I also think this effect isn't consistent but I'm not good enough to be sure.

 

Here is a short video, is this the effect we're talking about? at the point where the Gazelle starts to line up to the direction of travel I'm doing in excess of 100Klm/h more like 120 130 at a guess. I purposely do not correct this for a bit and I'm flying obliquely at about 45 degrees to direction of flight which after correcting attitude my IAS is 150Klm/H

 

Link here might be best to download then watch

 

Or have I totally missed something?

It may have been mentioned, already, but I would like to point out, the Stabilization system on the Gazelle.

It supports you in normal flight and you need to deactivate it shortly, when doing heavy maneuvering, especially at low speed.

In normal flight it wants to steady the helo in turns, which is "feeling" strange coming from the Huey with its direct controls. I also found gyroscopic precession is very pronounced and I tend to over control even with Y-saturation reduced, per advice of The_Fragger (Polychop).

 

I still need some time to adjust, whenever I switch from the Huey to the Gazelle or back...:hmm:

 

EDIT this post explains a bit about the SAS from the actual Gazelle manual (and keep in mind, the civilian SA-341 has no SAS...)

Edited April 24, 2017 by shagrat

[FragBum]

It may have been mentioned, already, but I would like to point out, the Stabilization system on the Gazelle.

It supports you in normal flight and you need to deactivate it shortly, when doing heavy maneuvering, especially at low speed.

In normal flight it wants to steady the helo in turns, which is "feeling" strange coming from the Huey with its direct controls. I also found gyroscopic precession is very pronounced and I tend to over control even with Y-saturation reduced, per advice of The_Fragger (Polychop).

 

I still need some time to adjust, whenever I switch from the Huey to the Gazelle or back...:hmm:

 

EDIT this post explains a bit about the SAS from the actual Gazelle manual (and keep in mind, the civilian SA-341 has no SAS...)

 

Yes I think I learnt the Gazelle backwards but yes I like flying it both with "ÄP" on and off, now mostly off. I get the difference in both states.

 

Maybe it should pull up more aligned (or not), however toque correction is trivial and sometimes desired, for better "framing". :thumbup:

 

Oh fly the Huey for some gyroscopic procession, much more mass.

 

I run X.Y saturation at 90 feels good.:joystick:

[shagrat]

Oh fly the Huey for some gyroscopic procession, much more mass.

 

Yep, that's the thing. Huey handles way easier, as it is slower to react and moves like a sedan, if you know what I mean.

Gazelle is reacting direct and the control input is still delayed, but if it reacts it reacts more extreme, by then you gave too much input already, as you are used to the slow reacting Huey... :music_whistling:

 

The characteristics of all DCS choppers are pretty different. I guess this is some of the problems people have here. You have very exact flight models, that are capturing the individual characteristics, quite well. Albeit, the helicopters modeled are totally different.

Now, everybody (me included) thought, "I fly Huey like a pro. How difficult can a Gazelle be... Wait, this is totally different. That must be wrong".

 

After a while you realize it isn't "wrong". Why else, would real life Gazelle pilots state it is accurate, if it was totally off, they would be the first to notice, right?

 

So after realization, that I am the one that needs to learn and train flying another helo, it is more like the difference between an old 1980ies sedan, with 60HP and a 2010 Nissan Micra "Rallye racer" with 95HP, 4WD, Anti-Skid, traction control, etc.

 

And it has cruise-control... :D

[Pocket Sized]

Re: flying inverted

 

Loops are fine in a helicopter as long as you're careful. The main limiting factor preventing inverted flight is the blades. They will flex down and hit the tail boom under negative G.

 

You don't necessarily need negative collective pitch to fly inverted, translational lift will hold you up if you have enough forward speed, in theory.

[Ramsay]

Ok guys, Ive been reading all about the FM of the Gazelle and all the complaints about it.

 

Im not a helicopter pilot, or any other type of pilot besides armchair although I have taken the controls of a Cessna 152 a few times.

 

But after reading the Gazelle operating manual, I would be led to believe that the FM is not too far off at all. First off, the Gazelle has not only an SAS system, it also has a flight director. For those complaining that they disabled the SAS and it does the same thing...Disabling does not disable the FD/Autopilot.

 

So to put the info in the manual to the complaints...

[snip stuff from manual]

The SAS/FD you cite is from the Sperry IFR avionics suite fitted to some SA341 G, so has very different cockpit/instrument layout and features to the SA342 modelled.

 

Page 122, Supplement No 13, I.F.R. Flight Package P/N 341 MR 0345

 

http://www.avialogs.com/en/aircraft/france/aerospatiale/as341gazelle/flight-manual-gazelle-sa-341g.html

[TripRodriguez]

You don't necessarily need negative collective pitch to fly inverted, translational lift will hold you up if you have enough forward speed, in theory.

 

I was thinking that might be the case myself, but wasn't sure.

[FragBum]

Yep, that's the thing. Huey handles way easier, as it is slower to react and moves like a sedan, if you know what I mean.

Gazelle is reacting direct and the control input is still delayed, but if it reacts it reacts more extreme, by then you gave too much input already, as you are used to the slow reacting Huey... :music_whistling:

 

The characteristics of all DCS choppers are pretty different. I guess this is some of the problems people have here. You have very exact flight models, that are capturing the individual characteristics, quite well. Albeit, the helicopters modeled are totally different.

Now, everybody (me included) thought, "I fly Huey like a pro. How difficult can a Gazelle be... Wait, this is totally different. That must be wrong".

 

After a while you realize it isn't "wrong". Why else, would real life Gazelle pilots state it is accurate, if it was totally off, they would be the first to notice, right?

 

 

I gotta say in my very limited experience with the "AP"off and hovering it feels kinda like a Robinson r44 in as much as there are a lot more fine corrections need to be added to maintain a hover compared to "AP" on.

 

I also agree coming from Huey a helicopter you would climb into in RL to a Gazelle that you kinda sit into in RL and the "AP" on, the Gazelle sometimes feels slightly counter intuitive until you get used to it.

 

So after realization, that I am the one that needs to learn and train flying another helo, it is more like the difference between an old 1980ies sedan, with 60HP and a 2010 Nissan Micra "Rallye racer" with 95HP, 4WD, Anti-Skid, traction control, etc.

 

And it has cruise-control... :D

 

Yep I'm off for some more practise too. :thumbup: