Impossible to fly for anyone else?

[Weta43]

I know this analogy has been done to death, but would you, when you watch an F1 car leaping off the start line, carving through corners and stopping like it dropped an anchor, expect Joe Prius driver to get in and do anything other than kill themselves, if on their first drive they tried to achieve competitive lap times ?

 

Yet people think because the Su-27 can be flown in a similar way to an F-1 car, that it should be as docile as a Prius.

 

In a way the contrast between the F-15 FCS design philosophy & the Su-27's is a bit like the contrast between those of various car designers.

 

Some car designers (maybe think VW with the Bugatti) throw traction control, launch control, electronically controlled differential braking to provide stability control & a host of other driving aids at the car to help drivers drive it at it's limits.

Other manufacturers (Ariel Atom ?) just build a car that has naturally good handling, and provides the driver with proper feedback, then let the driver control the car.

 

In the hands of an excellent driver, there are pro's and con's to both approaches, but both are very capable.

 

The instability at negative AoA seen in the Su-27 PFM is detailed in the RL flight manual as a warning to pilots not to do what virtual pilots here keep doing. The change in pitch with change of speed is part of the design approach, the low stability in pitch is well documented in print, including by US pilots.

 

Almost all the complaints in this thread to this point seem to be the result of either unrealistic expectations (Why wouldn't you let the aircraft auto-trim? because the real aircraft doesn't), or limitations of the gear being used - a combination of short throw sticks & a lack of tactile feedback.

 

I use an MSSFFB II & as Ironhand says, if your speed is stable, the trim as implemented is quite capable of allowing you to easily trim to straight & level, additionally, the force feedback allows trimming to become quite a natural response to the information the aircraft is providing, including the 24 degree AoA kick & high AoA buffeting.

 

The Su-27 as modelled is NOT a hard aircraft to control or fly at the limits, but you can't just throw the stick around and expect the computers to reject any over the top inputs. You have to be mindful of what you're doing, as the aircraft won't stop you flying past its limits if you (intentionally or carelessly) ask it to, and will let you get yourself into trouble when you do so - but it will be you doing so, not the aircraft.

 

 

The real bird will 'kick' the stick back at 24 deg AoA. How does one simulate this in the game?

The DCS version 'kicks' the stick at 24deg AoA :)

[Mr Whippy]

Two things:

 

1) The FM is still beta-ish, but that's for Yo-Yo to answer. This means the physics may not be entirely correct, regardless of what the FBW is doing. The FBW may also require tweaking.

2) The workload IS decreased. Fly without stability augmentation and you'll fly yourself into bad situations much more often. The stability augmentation gives a fake positive stability behavior to the aircraft.

 

 

A heavily loaded aircraft isn't necessarily less stable, you'll just reach unpleasant AoA values faster.

 

Certainly a heavy aircraft will and should behave differently. Payloads can change the center of gravity which can give rise to unwanted behaviors -for example on the F-15 hanging a centerline tank on it immediately makes it more susceptible to yaw departures and other effects. The difference might be subtle in some conditions/aircraft, huge in others.

 

In the end, it is up to you to gain the necessary knowledge about how aircraft fly and why, and then the necessary skill and finesse to control that aircraft.

 

 

 

In the training mission for guns the SU27 flies like a dream. I can completely appreciate here that you'd have to fly like a complete idiot to do something wrong, and the stability control feels perfectly measured to keep the aircraft stable within the reasonable flight envelope any person would use.

 

 

But then in the quick intercept mission it seems really hard to fly hard without slipping into feedback loop levels of AoA that just leave you unable to correct and you just end up sat dead in the water at about 250kts.

 

 

 

But like we keep saying, it's apparently a beta, so to really say it's right or wrong right now seems fruitless I suppose.

 

I hope they finish it up soon. It's a bit gutting that it's unfinished as it's the main reason I bought the FC3 after seeing it on Steam... it didn't say it was a beta version :(

 

 

edit:

 

Hmmm, I think I spotted my problem. Replay view shows feet and kts, cockpit is showing kph and metres?

 

I was probably flying higher and slower than I thought???

 

 

My brain is conditioned for imperial units for flying ;)

 

As much as I bemoan imperial, for flying I've just got used to them over many years of flying Falcon and Tornado etc.

 

 

 

But I still think that at 20,000ft (6000m or so), and 400kts, even with my controller curve more S shaped (so about 15% input is probably about 10% request to the FBW), is ample to have my AoA be exceeded after a short while (ie, transient manoeuvre of a few seconds), and feedback loop ensues and I lose all airspeed and AoA runs up to some limiter.

 

Why wouldn't the controls be re-ranged for such flight envelopes? You essentially just have about 70% of your stick range made useless. Is this how it really is in such flight conditions?

 

Dave

Edited May 30, 2015 by Mr Whippy

[steve65]

This analogy might have been done to death Weta43 but you did it better than anyone.i like your explanation.:thumbup::thumbup::thumbup:

 

 

 

PS:I agree with Darkfire I think the trim is too coarse.maybe a finer trim would make it easier to trim

Edited May 30, 2015 by steve65

[GGTharos]

@Weta: Good info :)

 

@Whippy:

 

But like we keep saying, it's apparently a beta, so to really say it's right or wrong right now seems fruitless I suppose.

 

I hope they finish it up soon. It's a bit gutting that it's unfinished as it's the main reason I bought the FC3 after seeing it on Steam... it didn't say it was a beta version :(

 

That it's 'apparently beta' doesn't mean it's unfinished. We just don't really know.

 

 

I was probably flying higher and slower than I thought???

 

That changes everything.

 

But I still think that at 20,000ft (6000m or so), and 400kts, even with my controller curve more S shaped (so about 15% input is probably about 10% request to the FBW), is ample to have my AoA be exceeded after a short while (ie, transient manoeuvre of a few seconds), and feedback loop ensues and I lose all airspeed and AoA runs up to some limiter.

 

400kts true or indicated? That makes a huge difference. 400kts true at 20000' is close to 300kts indicated. In any case, the higher you go, the less g you can sustain. The heavier you are, the less g you can sustain. The corollary is that you reach higher AoA sooner for the same g (if it is above the ability to sustain g).

 

Why wouldn't the controls be re-ranged for such flight envelopes? You essentially just have about 70% of your stick range made useless. Is this how it really is in such flight conditions?

 

Yep. It's up to you to understand how an aircraft behaves and flies. No matter what the FBW does, it can't change physics.

[Ironhand]

...

 

But I still think that at 20,000ft (6000m or so), and 400kts, even with my controller curve more S shaped (so about 15% input is probably about 10% request to the FBW), is ample to have my AoA be exceeded after a short while (ie, transient manoeuvre of a few seconds), and feedback loop ensues and I lose all airspeed and AoA runs up to some limiter...

And here, I think, might be the problem. I assume you're in one of the A2A modes (rather than a NAV mode) so that, regardless of whether you are in F2 view or looking at the HUD, your speed is being reported as TAS. This is significant because at those higher altitudes your IAS will be much lower. Those 400 kts you mentioned is actually more like 285 kts at 20000 feet.

 

EDIT: GG got there first with the question. Darned customers keep interfering. I start to type and then...

[steve65]

And here, I think, might be the problem. I assume you're in one of the A2A modes (rather than a NAV mode) so that, regardless of whether you are in F2 view or looking at the HUD, your speed is being reported as TAS. This is significant because at those higher altitudes your IAS will be much lower. Those 400 kts you mentioned is actually more like 285 kts at 20000 feet.

 

EDIT: GG got there first with the question. Darned customers keep interfering. I start to type and then...

 

Ironhand or GGTharos is there someplace I can find information about TAS and IAS and how they relate to combat aircraft?i never knew they made such a difference in combat and I would like to learn more about the difference between them.

[DarkFire]

Ironhand or GGTharos is there someplace I can find information about TAS and IAS and how they relate to combat aircraft?i never knew they made such a difference in combat and I would like to learn more about the difference between them.

 

Wikipedia actually has some good articles on both true and indicated airspeed, as well as calibrated air speed (interesting... Why don't aircraft use this?) and some other peculiarities:

 

IAS: http://en.wikipedia.org/wiki/Indicated_airspeed

 

TAS: http://en.wikipedia.org/wiki/True_airspeed

[GGTharos]

They relate to all aircraft.

 

TAS - True Airspeed = Speed that you are moving at through the airmass. Basically if you measured speed with a radar gun, you'd get TAS.

 

IAS/CAS - Indicated/Calibrated airspeed = Speed that your aircraft 'feels'. This speed is measured by the aircraft's sensors and reported to you. Basic handling (roll and pitch moments for example) is usually consistent based on IAS/CAS. CAS is a more accurate version of IAS if I understand things correctly.

 

IMN - Indicated mach number. Knowing IMN is a bit like knowing TAS, but not exactly. Most performance charts for aircraft (sustained g) are related to IMN.

 

You can google things like TAS/IAS calculator and you'll find a lot of things that are useful :)

 

Ironhand or GGTharos is there someplace I can find information about TAS and IAS and how they relate to combat aircraft?i never knew they made such a difference in combat and I would like to learn more about the difference between them.

[steve65]

Thank you Darkfire and GGTharos for the information.looks like I have some studying to do.:book:

 

EDIT:ok I did some reading about TAS and IAS and if I understand correctly TAS is mainly used for accuracy in navigation and IAS is used for speeds in turns,stalls,landing and approach speeds etc.if I am correct.so in post 81 Ironhand replies to Mr Whippy that if he is in a A2A mode the HUD will show TAS which to me is totally opposite of what I read.if you are in a mode other than NAV mode shouldn't the HUD show IAS since it it mainly used for aircraft speeds while maneuvering?

Edited May 31, 2015 by steve65

[DarkFire]

I thought the HUD on the Su-27 always displayed IAS... Could be wrong though...?

[Svend_Dellepude]

In BVR mode (2) the HUD displayed TAS for some reason. All other modes are IAS AFAIK.

[Ironhand]

...if I am correct.so in post 81 Ironhand replies to Mr Whippy that if he is in a A2A mode the HUD will show TAS which to me is totally opposite of what I read.if you are in a mode other than NAV mode shouldn't the HUD show IAS since it it mainly used for aircraft speeds while maneuvering?

My apologies. It is only the BVR mode which reports TAS on the HUD. That mode used to report IAS but it was changed at some point. Not sure why except, perhaps, to make judging closure speeds easier?? Or it could simply be an error. But, when actively maneuvering, I tend to pay more attention to how the aircraft is handling than the speed displayed on the HUD. It's certainly helpful to have the IAS displayed, however, because it helps you anticipate how the aircraft will handle in various situations before you commit.

[GGTharos]

Judging closure and thus timing is of high importance in BVR. Your steam gauge should still be showing you IAS if you need it.

[Ironhand]

Judging closure and thus timing is of high importance in BVR...

Makes sense.

[Fri13]

Judging closure and thus timing is of high importance in BVR. Your steam gauge should still be showing you IAS if you need it.

Was about say same as firing missiles at max range can be tricky if not knowing distances etc correctly.

[Erdem]

I recently returned to DCS and of course, I had to check out the "new" Su-27. Lots of frustration, confusion and swearing ensued. This thing just doesn't want to fly stable, constant trimming is mandatory, tends to get into murderous spins at the slightest mistake and being in overall a pain in the ass to fly. For the first time in DCS I felt myself like "floating" rather than actually flying through the air. I never imagined Su-27 as being such "POS", I ended up switching to the 33 in the end to save myself the frustration.

 

Then jumped into the Eagle and it was just smooth sailing. Super responsive and precise, nearly impossible to stall, auto-trimming and great weapons. It was like easy-mode after the 27.

 

I wonder if the difference is 27 AFM being made by Eagle Dynamics themselves and the 15 being outsourced to a third party developer.

[steve65]

Judging closure and thus timing is of high importance in BVR. Your steam gauge should still be showing you IAS if you need it.

 

Makes sense.

[Weta43]

I wonder if the difference is 27 AFM being made by Eagle Dynamics themselves and the 15 being outsourced to a third party developer.

 

No :) The difference has to do with the flight characteristics of the aircraft themselves, and the quite different intentions of the designers of the two aircrafts' flight control systems.

 

The Su-27 was - apparently on the basis of feedback from their pilots - designed to 'react' like a conventional light aircraft, and so IN REAL LIFE needs constant trim with speed and weight changes.

 

Maybe it's lazy to link to my own post, but did you read this Erdem?

http://forums.eagle.ru/showpost.php?p=2404535&postcount=77

 

Most important point :

 

You have to learn to fly within the controlable envelope of flight, the aircraft doesn't discard any inputs just because they're taking you down a a path to trouble...

 

There are enough cues in the sim to allow you to do that, you just have to familliarise yourself with them.

 

Once you have, you'll find you have the aircraft you were expecting.

[Mowgli]

I recently returned to DCS and of course, I had to check out the "new" Su-27. Lots of frustration, confusion and swearing ensued. This thing just doesn't want to fly stable, constant trimming is mandatory, tends to get into murderous spins at the slightest mistake and being in overall a pain in the ass to fly. For the first time in DCS I felt myself like "floating" rather than actually flying through the air. I never imagined Su-27 as being such "POS", I ended up switching to the 33 in the end to save myself the frustration.

 

I also recently returned to FC3 with the intention to learn the new flight module of the Flanker - I understand your frustration but try to look at it as a challenge, like one member wrote here in the forum: "people ask for realism but when the get it they complain & unable to deal with it"

 

I'm still learning this amazing beauty, that's the reason why I'm not flying MP yet, but once U get to understand the importance of trim and the way she reacts to speed and weight changes your gonna enjoy every minute with her in the air.:pilotfly:

[*Rage*]

I recently returned to DCS and of course, I had to check out the "new" Su-27. Lots of frustration, confusion and swearing ensued. This thing just doesn't want to fly stable, constant trimming is mandatory, tends to get into murderous spins at the slightest mistake and being in overall a pain in the ass to fly. For the first time in DCS I felt myself like "floating" rather than actually flying through the air. I never imagined Su-27 as being such "POS", I ended up switching to the 33 in the end to save myself the frustration.

 

Then jumped into the Eagle and it was just smooth sailing. Super responsive and precise, nearly impossible to stall, auto-trimming and great weapons. It was like easy-mode after the 27.

 

I wonder if the difference is 27 AFM being made by Eagle Dynamics themselves and the 15 being outsourced to a third party developer.

 

We all had to 'relearn' to fly once the PFM was out. Bad habits die hard and I can tell you once you get used to it the new 27 PFM is a real joy!

 

To answer your question, The 15 and 27 flight models are developed by different teams and that may be a factor in why the 15 is easier to fly but I actually think that is only a minor factor in your frustration. You cant fly the 27 like you used to in SFM mode. ED have done a great job of modelling how it is in real life.

 

There is light at the end of the tunnel! Once you lose your old habits and relearn to fly and trim its a lovely airframe to fly and fight in:)

[IonicRipper]

Only thing bothering me with the flight model is how if you push the stick forward at speeds lower then say 700 kph (depending on altitude) it intermediately goes into an inverted stall with the pilot blacked out. Only way i've found to pull out of it is RAlt-J and let the AI with its SFM correct it and jump back in. Obviously that doesnt work in MP.

[Mowgli]

Only thing bothering me with the flight model is how if you push the stick forward at speeds lower then say 700 kph (depending on altitude) it intermediately goes into an inverted stall with the pilot blacked out.

 

Can someone from ED developers or Admin confirm how the Flanker Behaves in the situation described? in reality did Flanker pilots really encountered this problem or Does ED need to fix few things in the next patch?

[Weta43]

Somewhere on the forum there's a graphic taken from a Flanker manual with the AoA limits for various speeds & a discussion of how it fits with the current FM.

The negative AoA at which you'll invert in the SIM was outside the 'do not exceed' limits on the image.

If it's happening to you, you're doing something wrong...

 

(Edit : what's /below isn't the image I meant, but it gives you the idea)

Edited June 9, 2015 by Weta43

[Solway]

Only thing bothering me with the flight model is how if you push the stick forward at speeds lower then say 700 kph (depending on altitude) it intermediately goes into an inverted stall with the pilot blacked out. Only way i've found to pull out of it is RAlt-J and let the AI with its SFM correct it and jump back in. Obviously that doesnt work in MP.

 

1. it wasn't the blackout but redout which is much worse

2. Su-27 flight manual limits neg overloads (you can see below (3) but only in Rus but there everything clear):

- Nymin=-0,5g IAS <= 300 kmph (by inverted stall)

- Nymin=-2g IAS<=0,85M

- Nymin=-1g IAS>0,85M (both by AC destruction)

3. pls share your experience what jet AC aerobatics do you make with such negative overloads (I really do not know any ones) when she goes to inverted stall. I think it was a pilot mistake.

4. now Su-27 is beta but finally I hope real AC strength model will be realized and situation you've described will be impossible fundamentally.

Edited June 10, 2015 by Solway

[karambiatos]

Doesn't the real aircraft have some kind of limiter to stop the pilot from pulling too many - Gs