Gazelle Flight Dynamics... Again.

[Whisper]

@Whisper As far as I know we only have PolyChop's word that real Gazelle pilots said it was good. We (the community) are trying to get some Gazelle pilot opinions ourselves (got an iron in the fire on that one).

Actually, no.

From reports outside of devs I got (for example, on french CheckSix forums), directly from pilots, that "good shape" of Gazelle FM seems confirmed and the issues shown here blown out of proportion, though I'm pretty sure they do exist.

Just on this relatively recent topic for example, 2 gaz pilots posting in it : http://www.checksix-forums.com/viewtopic.php?f=465&t=196343

 

What do they say? That the gaz' FM is responding like real in 80% of the flight enveloppe, that it doesn't seem to be the case for every other helos in DCS (he pointed out the UH1, that he also flew, that seems too assisted for him). They find the Gaz FM bashing way too hot.

[cichlidfan]

What do they say? That the gaz' FM is responding like real in 80% of the flight enveloppe, that it doesn't seem to be the case for every other helos in DCS (he pointed out the UH1, that he also flew, that seems too assisted for him). They find the Gaz FM bashing way too hot.

 

I would not call 80% 'close' to anything.

[Whisper]

I would not call 80% 'close' to anything.

 

If you do, then head over Belsimtek forums, because from the same pilot tale, the UH1 behavior is not responding correctly for more than 20% of the flight envelop.

 

Our simulations are far farther from real than you seem to think, I'd say.

[shagrat]

If you do, then head over Belsimtek forums, because from the same pilot tale, the UH1 behavior is not responding correctly for more than 20% of the flight envelop.

 

Our simulations are far farther from real than you seem to think, I'd say.

 

Yupp! ...still it is closest to real life, that you can get apart from mil grade simulation.

[AlphaOneSix]

Our simulations are far farther from real than you seem to think, I'd say.

 

This is very true, in my opinion. (Although my opinion is really only valid for the Mi-8)

 

Yupp! ...still it is closest to real life, that you can get apart from mil grade simulation.

 

This is also true. :)

[myHelljumper]

Actually IIRC the ALAT pilots that used the DCS gazelle said that it was better than their military grade simulator :D.

[BIGNEWY]

Guys talk about the flight model by all means

 

don't be disrespectful doing it

 

forum rules and guides are in my signature, stick to them or find somewhere else to talk about it

[doodenkoff]

My comment was not disrespectful. It pointed out that in the Gazelle, a flat turn is beyond difficult. I can get beautiful hovers, I can take off smoothly, I can land the helicopter, but I cannot get a smooth, flat turn to either port or starboard. The variometer looks like a spastic one-handed clock; first heading south, then north, then south, then north. And I've watched this behavior in reviews and tutorials published to YouTube. The pilot starts a turn, and the helo immediately heads for the deck. They try and correct, and it's ballooning up into the atmosphere.

 

I'm entirely willing to concede it is me....but I have no other module that exhibits this recalcitrant behavior.

[BIGNEWY]

some of the posts were deleted as they related to the disrespectful ones not because they were disrespectful.

 

If you ever have a query about a moderation feel free to PM me.

[docWilly]

I did some posts on my experience with the FM in the past. I ´ve seen videos of DCS Gazelle flying upside-down, hovering upside-down, no response to asymetric load.

I have to state again: on my system, re-tested again on latest Beta release....

 

a) asymetric load leads the helicopter to roll in the direction of the load (expected)

b) unable to fly upside-down. Helicopter tends to dive then spirals out of control. Expected.

 

Unfortunately I am not a video maker nor do I have the time to do so.

 

I have no clue what you are doing on your side nor how you set up your system that this behaviour is possible.

 

Do you use an old and early FM to prove it´s wrong? Do you use "easy controls" checked in main DCS menue? Whatever I do I can not reproduce what some people show in their videos.

 

All I can say is such unrealistic flight attitudes are not present on my system. Conclusion for me: I am finished with this discussion, the Gazelle works well within it´s limitations, I am more or less satisfied - at least it does not spoil my simulation experience and I am looking forward to future improvements. I say this as "happy" customer and real life fixed wing (ok guys...yes different to helicopter flying) pilot with 12 yrs of flight experience (which at least means I have some idea about flight physics) and 12 yrs as medical doc on UH1-D (SAR German Aiforce, Ltg 61).

 

As said before....there´s room for improvement on the actual FM but it´s not crap or total desaster.

 

Just my 2 cents

 

Willy

Edited May 5, 2017 by docWilly

[some1]

I have no clue what you are doing on your side nor how you set up your system that this behaviour is possible.

 

My question is: what do you do, so you observe effect of asymmetric loads?

 

I just launched a basic mission without any wind and HOT's only on one side. With gyro on the helicopter stays leveled all the time. With gyro off, pitch/bank changes but very slowly, you need a minute or two two actually see it and the aircraft is still fully controllable with rudder only. You can nullify the bank and even bank it in the other direction with rudder input. If you keep it spinning and maintain a slow speed, then it looks exactly like on the video.

Edited May 5, 2017 by some1

[some1]

b) unable to fly upside-down. Helicopter tends to dive then spirals out of control. Expected.

 

Attached is a track with my quick attempt at flying inverted. It may not be as clean as the youtube video (no rehearsals), but I should get bonus points for descending inverted and backwards at the same time.

GazelleInverted.trk

[Holbeach]

@ DocWilly

 

There is no trick. Some people like shooting down F-15s with their never missiles. I like flying upside down.

Both are provided by the module we paid for.

 

The clue to how it's done is within the video.

 

 

..

[docWilly]

Well...all I can say is that I load asymetric (2 HOT on one side), take off with a fair amount of antitorque pedal (as the heli turns counter clockwise on takeoff as usual), straighten it out in forward flight and then it starts rolling to the sinde of the load...slowly (within say 5 sec) but it does.

The strange thing for me is that from the very beginning I had different findings than many people about the FM. I do nothing special than flying :-)

[docWilly]

Thanks for the video.

Unable to reproduce on my side. Now you may say my controls are the cause... I don´t think so because with all other modules I own (Huey, M2000, A10C) they work straight out.

Once again, I have no idea why my experience with the Gaz is so different to others concerning those "special" flight attitudes.

I keep DCS beta up to date, no FM tuning on my side, use the hardware in my sig, and fly it with "easy mode" unchecked in DCS main menue and some slight curves in controls that fit my "feeling". Thats it.

 

Nevertheless....thanks for the vid...impressive flying :-))))

[Asset]

Unable to reproduce on my side.

 

I tried the inverted flight just now. I managed to get inverted at my very first try but not again afterwards. Beginners luck I guess. However the one time I got inverted I could hold it stable all right for several seconds before I decided to roll out again.

So yeah, it is possible with the current DCS 1.5 stable version and I doubt it is possible with the real Gazelle.

 

Did not check on the asymmetric loads.

[MAD_MIKE]

Sorry my English. Being a real pilot does not guarantee full knowledge of flight dynamics as being a race driver does not guarantee full knowledge of race engineers job. Devs at first should rely on physics. Real pilots it's secondary. But in Polychop pilots point in first place.

How explain reverse speed 150 km/h? How explain lack of vortex ring on huge vertical speed? It's all only most visible things.

[tob.s]

well a game simulation isnt about having an exact 3d and physical model where every single part has its properties and interacts with everything around in realtime, maybee doing so would even be simpler than the devs actual work cause they have the hard task to take all that flight/perfomance data and create (mathematical) models that reassemble the behaviour. The further u push the plane into extremes, the less data there is - so its only logical that the models will allow odd things.

 

Short, if u want a realistic experience u dont just need a realistic helo-sim but also a realistic (simulated) pilot, if u fly manouvers noone would fly in real life u cant blame the model as its not doing what its meant to do.

 

Not saying that every odd behaviour should be ignored but theres a limit on whats possible / reasonable effort

 

Overall i realy love the gazelle - while the fm might still need tweaking ( i cant say cause i never flew a real one) lets not forget the gazelle was the first module after very long time to implement new and unique features and even a bunch off differnt versions so if its about the effort put into the module, i think u realy cant complain and i have no doubt that polychomp will keep up the great work once they figured out their legal stuff.

[BitMaster]

Just a dumb question from an R/C heli pilot:

 

How fast can it DECENT from high altitude if you LOWER pitch ALL THE WAY ?

 

Reason I ask this is simple and mechanical:

 

The rotor blades are controller by a Swashplate that itself is operated by multiple levers, either a 3-lever 120° fixture, 4-leaver 90° degree fixture ( usually, others exist too ).

 

To lift off and hover usually you need around 4° pitch angle on the blades, more or less regardless of size of the helicopter, amount of blades and their length as they usually are within a reasonable relation to each other.

 

The lowest angle you can set them to defines your maximum decent. I would not expect a full size and heavy helicopter to have less than 1° as it's minimum pitch for various reasons.

 

The rotorshaft above the cell would have to be longer, the levers need more travel as do thre actuators who drive the levers. Still, this would be possible but would make no sense as you would never need it in a Full Scale Heli imho. The force you will fuse into the mass directed downward would be so great that you would need either a LONG downpath to stop the decent or a full 15° pitch angle ( and the motor to hold the rpm ) to stop the decent before you hit the ground. Still, in limits this would work...still, it would make no sense.

 

In order to fly a sustained INVERTED flight path you need at least -4° to HOVER and some more negative pitch to gain altitude while inverted, which 1 pilot stated he achievded, so at least he needed -5 to -6 degrees negative pitch to do that. DO you know how much travel your swashplate would need to do that ? How long the shaft would need to raise above the cell with the last bearing giving stability to te shaft ? It's abnormal to say at least.

 

My friend is a multiple champion grade R/C heli pilot, RL pilot and one of the best guys on sticks I ever saw in person to operate a heli, his 1600mm diameter class heli has 13kW ( LiPo powered ). Standard helis of that size have 9.95cc -15cc( 0.61-0.9 cubic inch ) 2 strokes with about 1-3 kw, to give you an idea what he is capable to control in full inverted backward flight. He laughs about the Gazelle doing this, it's way beyond...for many reasons.

 

The Gazelle likely does not have that much negative pitch to do that, it may not even go below +1° pitch.

 

The blades would cut the tail off as soon as you would go lift up inverted at least, more likely way way before that.

 

Until someone can PROOF that the swashplate of the Gazelle has -3 to -6° nehative pitch this is pure nonsense.

 

As I said, I dont own The Gazelle, but there are things you can do to see how much negative power it can produce. Hover at high altitude and go to FULL DOWN...and see if you fall down FASTER than 1G would pull you. If it can ACCELERATE its downward movement it has negative pitch ( for whatever reason is then to be asked, if real or not ) and if it DOESNT it should NEVER EVER be able to fly sustained inverted.

 

DOing a barrel role or a loop is NOT the same, you can do this with A LOT OF positive Pitch, tho having the least pitch while inverted would look better :)

 

Hover high, lower pitch ALL THE WAY and see if you accelerate downward with a great force, you can measure the time and do the math with gravity equations to hit the nail precisely.

 

I would personally guess there is NOT one full size heli that has negative pitch at hand at all.

 

Thing is, if it doesnt have negative pitch and still is able to perform it in DCS something is badly wrong and likely effects other flight parameters in some strange way. It is unlikely that it would only result in an inverted flight and nothing else.

 

I will stay away from the Gazelle until this is fixed.

 

*edit* also of interest is the airfoil of the blades. Usually for 3D manouvers you need SYMETRIC airfoil. I doubt it has a symetric airfoil but rather a S-style airfoil for greater efficiency.

 

Bring prrof of the pitch angles and airfoil and you can tell directly if YES or NO from those numbers and shapes, that simple it is, no guess work needed

Edited May 12, 2017 by BitMaster

[borchi_2b]

You know there is a difference between a program and real phisics acting on a rotor? also there is a huge difference if we talk about 3d rc helos or real helos? Plus have you read the article?

 

Again, I am witing for detailed responces fom the french army. I will not spoil which department, cause it is a matter of trust, but yes, we gave 6 modules to them as a present to evaluate our product in terms of what we are allowed to change if we want and what we will have to look into from thier point of view. Unfortunately, as they have more serious stuff to do then play our game, they are fighting a war in mali still today, we all have to wait a bit for responses, which sometimes takes a bit.

And i hope you can comprehend, that we prefer to listen to the guys that fly them every day and as soon we have the aswers we need, we can get back to work on the fm.

 

I can only ask kindly to have patience. Who is not able to have patience is an unpatient personality :D :D :D

 

So in the meantime I et back to what I am working on and prepare further stuff for programming. enjoy your weekend

 

Just a dumb question from an R/C heli pilot:

 

How fast can it DECENT from high altitude if you LOWER pitch ALL THE WAY ?

 

Reason I ask this is simple and mechanical:

 

The rotor blades are controller by a Swashplate that itself is operated by multiple levers, either a 3-lever 120° fixture, 4-leaver 90° degree fixture ( usually, others exist too ).

 

To lift off and hover usually you need around 4° pitch angle on the blades, more or less regardless of size of the helicopter, amount of blades and their length as they usually are within a reasonable relation to each other.

 

The lowest angle you can set them to defines your maximum decent. I would not expect a full size and heavy helicopter to have less than 1° as it's minimum pitch for various reasons.

 

The rotorshaft above the cell would have to be longer, the levers need more travel as do thre actuators who drive the levers. Still, this would be possible but would make no sense as you would never need it in a Full Scale Heli imho. The force you will fuse into the mass directed downward would be so great that you would need either a LONG downpath to stop the decent or a full 15° pitch angle ( and the motor to hold the rpm ) to stop the decent before you hit the ground. Still, in limits this would work...still, it would make no sense.

 

In order to fly a sustained INVERTED flight path you need at least -4° to HOVER and some more negative pitch to gain altitude while inverted, which 1 pilot stated he achievded, so at least he needed -5 to -6 degrees negative pitch to do that. DO you know how much travel your swashplate would need to do that ? How long the shaft would need to raise above the cell with the last bearing giving stability to te shaft ? It's abnormal to say at least.

 

My friend is a multiple champion grade R/C heli pilot, RL pilot and one of the best guys on sticks I ever saw in person to operate a heli, his 1600mm diameter class heli has 13kW ( LiPo powered ). Standard helis of that size have 9.95cc -15cc( 0.61-0.9 cubic inch ) 2 strokes with about 1-3 kw, to give you an idea what he is capable to control in full inverted backward flight. He laughs about the Gazelle doing this, it's way beyond...for many reasons.

 

The Gazelle likely does not have that much negative pitch to do that, it may not even go below +1° pitch.

 

The blades would cut the tail off as soon as you would go lift up inverted at least, more likely way way before that.

 

Until someone can PROOF that the swashplate of the Gazelle has -3 to -6° nehative pitch this is pure nonsense.

 

As I said, I dont own The Gazelle, but there are things you can do to see how much negative power it can produce. Hover at high altitude and go to FULL DOWN...and see if you fall down FASTER than 1G would pull you. If it can ACCELERATE its downward movement it has negative pitch ( for whatever reason is then to be asked, if real or not ) and if it DOESNT it should NEVER EVER be able to fly sustained inverted.

 

DOing a barrel role or a loop is NOT the same, you can do this with A LOT OF positive Pitch, tho having the least pitch while inverted would look better :)

 

Hover high, lower pitch ALL THE WAY and see if you accelerate downward with a great force, you can measure the time and do the math with gravity equations to hit the nail precisely.

 

I would personally guess there is NOT one full size heli that has negative pitch at hand at all.

 

Thing is, if it doesnt have negative pitch and still is able to perform it in DCS something is badly wrong and likely effects other flight parameters in some strange way. It is unlikely that it would only result in an inverted flight and nothing else.

 

I will stay away from the Gazelle until this is fixed.

 

*edit* also of interest is the airfoil of the blades. Usually for 3D manouvers you need SYMETRIC airfoil. I doubt it has a symetric airfoil but rather a S-style airfoil for greater efficiency.

 

Bring prrof of the pitch angles and airfoil and you can tell directly if YES or NO from those numbers and shapes, that simple it is, no guess work needed

Edited May 12, 2017 by borchi_2b
smilies missing

[BitMaster]

Hold your horses :)

 

I was just outlining the physics involved in inverted flight "REGARDLESS" of the size of helicopter. For inverted flight you need at least the same amount of negative pitch as you need for standard flight, given a symetrical airfoil on the blades.

 

Either the Gazelle has that much swashplate travel or it hasnt and if it has a non-symetrical airfoil on the blades it needs even more negative pitch to compensate for the S-shaped blades. It's that simple !

 

there are more than ONE guy stating that they flew it inverted and at least ONE person who says he was even able to climb in inverted flight.

 

I can wait and I dont get personal, pure technical talk.

Bitmaster

[borchi_2b]

I have no idea how the guys managed to climb inverted, I have never managed to do so in the DCS:SA342M. I also faced numerous times VRS where others stated there is none or people state that there is no groundeffect, although i certainly feel it start at 1 dics and getting more pronounced at 3/4 of a dics and increasing.

Tereare certain ways to test things, but as said before, please, I can only ask for patience. In the meanwhile I keep on working on a Polychop Skunkwork/ Phantomworks project.

And no, the name has no relationship to the project.

[some1]

there are more than ONE guy stating that they flew it inverted and at least ONE person who says he was even able to climb in inverted flight.

 

Haven't seen any proof that it can climb inverted. Maybe for a brief moment using a speed you gained in a dive, but certainly not by just rotating and putting collective fully down.

 

The guys who flew it inverted (me included) did it while sinking. Though Gazelle can be kept inverted as long as you have altitude to loose and is fully controllable in this state.

[BaD CrC]

Thanks borchi-2b! Can't wait to see the outcome of this survey with the Gazelle pilots. I think everybody flying at BlackSharkDen would dream to be able to chit chat with Gazelle pilots (by the way, if one day you can do a live event with an IRL gazelle pilot where people can directly ask questions, you guys would be stars to all the community).

 

@Bitmaster: not sure I understood you well in your last post but are you assuming that real life helicopters can have negative blade pitch? Because they don't. That's an RC thing only.

[borchi_2b]

@BaD CrC:

The idea of havng a live event with one of the french guys sounds like fun, but I doupt that this would be possible at all, cause we also have the responsibility to protect our sources, cause as stated before, some of the sources are active pilots that do fight in not so pleasent wars too.

Maybe in the future, the department I am talking too at the moment, could open up and do an interview. I can ask them but the first question will be like, what is this for and what questions do the people of the community have, plus in that case it is a real department of the army, not just a single pilot.

 

Maybe I could arrange a live event where some people of the community could be invited into the comms chat and this could be published as livefeed throught twich or so. This depends on the availability of the pilots. I can imagine that one of them might be willing to do such, but that would have to be planned and there would be some questions that are no goes, for example names, or missions the pilot has been active in or where he fought in general, stuff like that. So for such an event, if the pilot is willing to do such, this would require some planning.

 

For a different helicopter that I am working on I know that this livefeed and interview would defenately be possible, cause as soon the pilot, I am working with in that project, hears about that idea he is more then happy to go for it, I can imagine, plus, he is a good friend of mine.

 

BaD CrC, thanks for the inspiration for some cool marketing events possible to get closer ties to the community in the future again after all this silence.

 

Maybe the best question asked that day, wins a price. Have to see.

 

Ok, back to work, need to get something finished so it can go into coding.

Edited May 13, 2017 by borchi_2b