Gazelle Flight Dynamics... Again.

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.

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

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.

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:

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.

I'm pretty sure you do, ETL or not if you are inverted unless you can do negative pitch the rotor will suck you into the ground. Just think what happens when you drop collective let alone go neg AoA.

This 50$ argument is not good at all. A game (as opposed to a contract with a single client/government) might sell with 50$ but it can be sold to thousands or millions in case of a AAA title so at the end... the money bag might not differ in orders of magnitude but really be comparable.

This 50$ argument is not good at all. A game (as opposed to a contract with a single client/government) might sell with 50$ but it can be sold to thousands or millions in case of a AAA title so at the end... the money bag might not differ in orders of magnitude but really be comparable.

Yeah, there are 5100+ views on that statement by Polychop thread. I doubt many people are clicking on a thread with 0 replies more than once.

That's a way bigger "niche market" than I had assumed in the past.

So there goes that excuse.

Okay so after 11 plus pages apart from the OP no actual flight dynamics, Scarecrow you say delays in response are too slow yet sub 50ms to maybe 1/2 second seems to be about what I get for the air frame depending on flight situation. For me the Gazelle lacks stored energy in the rotor, the Huey's rotor stores much more energy but that needs to be balanced off against the Huey's mass and trajectory at any point in time.

As for the Gazelle try turning off the "AP"master switch, in that mode it feels very small helicopter-ish to me, however I'm not a real pilot. The "AP"system to me felt a bit off at first but it does seem to add a real benefit to control and attitude when you milk it.

YMMV. :thumbup:

Now could someone please explain the flight dynamics issue to me and no I'm not being a smart a..s I really want to know.

Okay so after 11 plus pages apart from the OP no actual flight dynamics, Scarecrow you say delays in response are too slow yet sub 50ms to maybe 1/2 second seems to be about what I get for the air frame depending on flight situation. For me the Gazelle lacks stored energy in the rotor, the Huey's rotor stores much more energy but that needs to be balanced off against the Huey's mass and trajectory at any point in time.

 

As for the Gazelle try turning off the "AP"master switch, in that mode it feels very small helicopter-ish to me, however I'm not a real pilot. The "AP"system to me felt a bit off at first but it does seem to add a real benefit to control and attitude when you milk it.

 

YMMV.

 

Now could someone please explain the flight dynamics issue to me and no I'm not being a smart a..s I really want to know.

Keep in mind, the Hueys blades in DCS are the metal ones, which huge inertia, compared to the Gazelles composite blades. ;)

Okay so after 11 plus pages apart from the OP no actual flight dynamics, Scarecrow you say delays in response are too slow yet sub 50ms to maybe 1/2 second seems to be about what I get for the air frame depending on flight situation. For me the Gazelle lacks stored energy in the rotor, the Huey's rotor stores much more energy but that needs to be balanced off against the Huey's mass and trajectory at any point in time.

 

As for the Gazelle try turning off the "AP"master switch, in that mode it feels very small helicopter-ish to me, however I'm not a real pilot. The "AP"system to me felt a bit off at first but it does seem to add a real benefit to control and attitude when you milk it.

 

YMMV. :thumbup:

 

Now could someone please explain the flight dynamics issue to me and no I'm not being a smart a..s I really want to know.

I could be wrong, but I was under the impression turning off AP does not affect the flight model.

I spelled out my biggest issue with the FM on a thread called "An answer to my flight model question".

The thing can fly at full speed in level flight with the cyclic centered.

I could be wrong, but I was under the impression turning off AP does not affect the flight model.

 

I spelled out my biggest issue with the FM on a thread called "An answer to my flight model question".

 

The thing can fly at full speed in level flight with the cyclic centered.

If you have SAS engaged or have it trimmed, or switched on "easier Flight model" yes, possibly.

With SAS channels off, no I can't remember any flight where I could let go of the cyclic... More on the contrary, it needs constant, very little, but controlled inputs, with stabilization off.

You have a master button on the Cyclic to quickly deactivate and reactivate the SAS in flight for effective maneuvering, especially at lower speeds.

Now could someone please explain the flight dynamics issue to me and no I'm not being a smart a..s I really want to know.

In short: it seems like polychop is using a "simpler" FM coding approach than the other helicopters in DCS. Their method is inevitably going to have limitations compared to a "physical" flight model. What do I mean by physical flight model?

[Youtube]ydvhyIJ-mCI#t=12s

BST and ED calculate flight dynamics by modelling the forces, paths, flexing, etc of each blade individually. I have yet to see anything that points towards the Gazelle using this type of FM.

That being said, with enough time, the current FM could be made quite accurate. I'm just afraid it will never really feel "organic" like the other helicopter FMs do.

Just my 0.02.

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.

No, the blades will only flex as much down if idoing -1G as they do up when flying with the normal +1G. The centrifugal force is the thing thats keeping them relatively straight out. Depending of helo type there will be a very little margin, so it is not recommended to try if not allowed for minus G's.

Translational lift wont help, you need negative pitch to do sustained* inverted flight.

But there are a lot of buts. All full scale helos have the blades twisted, with less blade angle at the tip then at the root. This is to give a good distribution of lift over the length of the blade.

Doing negative pitch with a blade twisted like that will give very bad distribution of lift, close to the blade tip will make most lift, and this will bend the blade an cause a lot of vibrations and so on. The fuel system of helis, in general, doesnt allow for negative g( it wount pick up fuel att minus G's, the same counts for the oil system.)

No full skale heli does sustained minus G or inverted flight.

*) you can fly at minus G for a short whiel with some helos. Pushing the cyclic stick forward when having good airspeed will produce negative G's. For example the Bo105 was allowed down to -1G where I flew it, and if flying fast forward and pushing the stick did produce minus G's for a short while, until the airspeed bled of. You could also roll it on to inverted and after that push the stick a little forward and then you got the feeling of inverted flight forma short while(airspeed dropped quickly...).

For the huey and all two bladed (teetered rotors) negative G is very dangerous because cause the helo is actually hanging free under the rotor and minus G will cause the rotor to hit the helicopter body. Then you die.

So do the bo105 vibrate when flying minus G's? Yes it does, and it also loose the oil pressure in engines.

Good explanation!

I didn't even realize the blades were twisted, definitely explains why the blades flex so much under negative G.

In short: it seems like polychop is using a "simpler" FM coding approach than the other helicopters in DCS. Their method is inevitably going to have limitations compared to a "physical" flight model. What do I mean by physical flight model?

 

[Youtube]ydvhyIJ-mCI#t=12s

 

BST and ED calculate flight dynamics by modelling the forces, paths, flexing, etc of each blade individually. I have yet to see anything that points towards the Gazelle using this type of FM.

 

That being said, with enough time, the current FM could be made quite accurate. I'm just afraid it will never really feel "organic" like the other helicopter FMs do.

 

Just my 0.02.

The Problem maybe it can't feel "organic" as it isn't like the direct model we are used to.

Keep in mind, the Hueys blades in DCS are the metal ones, which huge inertia, compared to the Gazelles composite blades. ;)

I know this and it's seems well modelled in both the Huey and the Gazelle. :thumbup:

I could be wrong, but I was under the impression turning off AP does not affect the flight model.

 

I spelled out my biggest issue with the FM on a thread called "An answer to my flight model question".

 

The thing can fly at full speed in level flight with the cyclic centered.

Okay I know you don't need much forward movement (well not a lot of movement in any direction) to make the Gazelle move so much that I found my control of the Gazelle (and Huey) improved when I modded my joy stick so there is no centre detent.

There was so much fine control and the centre detent made it difficult to use,. it seems to me that there is a small input required to maintain forward (or sidways or etc) flight and that movement was under the region of the centre detent.

Yes turning AP off means you need to input the fine corrections to maintain hover and under flight conditions.

I'll look into that a bit more latter.

cheers

In short: it seems like polychop is using a "simpler" FM coding approach than the other helicopters in DCS. Their method is inevitably going to have limitations compared to a "physical" flight model. What do I mean by physical flight model?

 

[Youtube]ydvhyIJ-mCI#t=12s

 

BST and ED calculate flight dynamics by modelling the forces, paths, flexing, etc of each blade individually. I have yet to see anything that points towards the Gazelle using this type of FM.

 

That being said, with enough time, the current FM could be made quite accurate. I'm just afraid it will never really feel "organic" like the other helicopter FMs do.

 

Just my 0.02.

Interesting although I now find the Gazelle organic if that means I get the same visceral fly by the seat of my armchair feel as I get flying the Huey. :thumbup:

Interesting although I now find the Gazelle organic if that means I get the same visceral fly by the seat of my armchair feel as I get flying the Huey.

Yep, if you adapt to the different characteristics it is as natural and organic as a Huey, Ka-50 or Mi-8. You need to understand and get used to the supporting systems, and how they affect the FM.

I guess that is why real life Gazelle pilots find the FM very accurate, as they are used to the difficulties we face.

Yep, if you adapt to the different characteristics it is as natural and organic as a Huey, Ka-50 or Mi-8. You need to understand and get used to the supporting systems, and how they affect the FM.

 

I guess that is why real life Gazelle pilots find the FM very accurate, as they are used to the difficulties we face.

Difficulties you say? ;)

Once you get the hang of the stability systems and it's good to get a feel for the raw aircraft as well, then you can appreciate how well the stability system is mostly, well it can't read your mind.

How explain this

I could be wrong, but I was under the impression turning off AP does not affect the flight model.

 

I spelled out my biggest issue with the FM on a thread called "An answer to my flight model question".

 

The thing can fly at full speed in level flight with the cyclic centered.

It shouldn't effect the FM but it will require you to provide the necessary control inputs to keep the air craft under control, I think some of the "off characteristics" are more to do with driving the stability system with you inputs and getting something you weren't quite expecting.

As for cyclic movement at 90% saturation it doesn't take much movement on the cyclic to go that way whichever direction you move it. However for forward flight wouldn't there be a component of force from the horizontal tail fins to set attitude at least close hence not much forward cyclic movement? I'm no expert but it knida makes sense that from forward flight you need to give the cyclic a bit if pull back to get it's attention.

Here's the back story to how getting rid of the centre detent function of the joystick made a difference.

Here

Just for comparison I run 100% saturation for the Huey.

How explain this

Interesting however I don't normally fly that way, I think I can get the Gazelle in a spin with AP and Trim off but I get giddy after a bit, :(

But how do you initiate the other modes?

I only have the Gazelle in DCS 2..x

Interesting however I don't normally fly that way, I think I can get the Gazelle in a spin with AP and Trim off but I get giddy after a bit, :(

 

But how do you initiate the other modes?

 

I only have the Gazelle in DCS 2..x

All tests with disable autopilot and without trimming

Yes that is how I am flying the Gazelle, but only for about 4 hours yet. :thumbup: