What is "aircraft stability" - IN VIDEO

[IvanK]

Here is a similar lecture by Dave Southwood on Youtube as linked by Richie a while ago.

http://forum.1cpublishing.eu/showpos...82&postcount=1

[ATAG_Snapper]

A great read, Slipball!

[SlipBall]

Thank you Snapper, please read aloud to Riley so that he remains up to snuff with the rest of us.

[Crumpp]

Christop55her says:
It takes more controlling on the part of the pilot.

Exactly. It must be controlled at all times and the pilot must watch his accelerations as he can overload the airframe much easier than other aircraft.

You can see the RAE measurements do not match the game in the most basic of stability characteristics.

The RAE measurements where chosen to be reproduced because of there can be no argument.

A small group of players felt like constantly attacking the NACA data as it was not gathered by the RAE. It was decided to concentrate on reproducing the RAE measurements.

The RAE measured the stability characteristics stick free by recording the oscillation over several minutes.

If you break it down into smaller time elements, you can see the Spitfire is rapidly changing speeds over just a few seconds.

Those oscillations must be controlled by pilot input and as the airplane is not stable, they must be constantly managed.

It is not a stick setting issue but one of the basic flying qualities of the aircraft. Joystick parameters have no effect on it.

Here is what the RAE measured:



Here is the results, the aircraft is neutral or unstable dynamically stick free.



Here is the result of the ingame testing. The conditions are the same. The stability is recorded stick free at 5.46 minutes. At that point the airplane is both static and dynamically stable, something the real aircraft was not during the Battle of Britain.

Dave Southwood

Never flew a Spitfire without an inertial elevator. In otherwords, he describes the aircraft AFTER the longitudinal instability was fixed.

[ATAG_Snapper]

Originally Posted by SlipBall

Thank you Snapper, please read aloud to Riley so that he remains up to snuff with the rest of us.

Absolutely! Will have to make a new movie, "Dogs of Dover" is so 2011! LOL

[Crumpp]

he also can't argue the fact that long period oscillations matter squat.

You seem to be confused about the ability to control something and it having no effect.

The pilot can control them. He has too or the aircraft will destroy itself left on its own. The oscillations increase in velocity and the airplane will reach its structural limits given enough time.

This is not a characteristics of a joystick setting, it is how the aircraft moves AFTER control input.

The NACA results were not tested in the game.

What was tested was the RAE conclusions to see if the game matched in the basic stability characteristics.

It does not. None of the RAE diagrams show the Spitfire statically and dynamically stable, dampening the oscillation in ~2minutes.

The RAE measurements show the aircraft neutral to unstable in normal and aft CG.

The Spitfire in CoD, is statically and dynamically stable stick free.


That means the player does not have to make double control inputs nor does he have to control the oscillation.

In CoD, a Spitfire can quickly achieve and hold a precise amount of acceleration without any careful flying or additional control inputs.

That is unrealistic and not representative of the early mark Spitfires.

That is something the real Spitfire could not do without careful flying and double control inputs from the pilot.

This is not an attack on the Spitfire, most people want realism and fun gameplay. In order to realistically model the Spitfire as used during the Battle of Britain, it must be neutral or unstable at normal and aft CG. The Operating Notes are filled with warnings and cautions as a result of the flying qualities.

The real aircraft were equal dogfighter. The flying qualities is one of the reason's why they were equals.

[Crumpp]

The Hurricane has unusual apparent longitudinal static stability characteristics (pitch trim change with speed). Depending on the c.g. position and the type of propeller fitted it varies from slightly stable to slightly unstable.

I have no idea what variant or set up of the Hurricane Dave Southwood is refering too here.

It is a fact, the Hurricane Mk I as it was used in service of the RAF during the Battle of Britain, was stable and near perfect in its longitudinal stability and control.

I love this part:

As a final thought, please note that it is easy to concentrate on the deficiencies of an aircraft and gloss over its other possibly excellent characteristics. The fact that the Spitfire has poor control force harmonisation and is easy to tip on its nose does not detract from its outstanding turn performance, superb low IAS and high Mach number controllability, and benign stall characteristics. It is a very charismatic and pleasant aircraft to fly overall. And the challenge of trying to master the Bf109 on take-off and landing makes it a very satisfying machine to fly once you have gained some confidence in it.

All the pilots loved the machine that took them home.

Myopically, some see modeling flying qualities as an attack or effort to "pork" their gameshape.

[klem]

Originally Posted by Crumpp

Exactly. It must be controlled at all times and the pilot must watch his accelerations as he can overload the airframe much easier than other aircraft.

You can see the RAE measurements do not match the game in the most basic of stability characteristics.

The RAE measurements where chosen to be reproduced because of there can be no argument.

A small group of players felt like constantly attacking the NACA data as it was not gathered by the RAE. It was decided to concentrate on reproducing the RAE measurements.

The RAE measured the stability characteristics stick free by recording the oscillation over several minutes.

If you break it down into smaller time elements, you can see the Spitfire is rapidly changing speeds over just a few seconds.

Those oscillations must be controlled by pilot input and as the airplane is not stable, they must be constantly managed.

It is not a stick setting issue but one of the basic flying qualities of the aircraft. Joystick parameters have no effect on it.

Here is what the RAE measured:



Here is the results, the aircraft is neutral or unstable dynamically stick free.



Here is the result of the ingame testing. The conditions are the same. The stability is recorded stick free at 5.46 minutes. At that point the airplane is both static and dynamically stable, something the real aircraft was not during the Battle of Britain.







Never flew a Spitfire without an inertial elevator. In otherwords, he describes the aircraft AFTER the longitudinal instability was fixed.

I don't want to get dragged into this but as its my chart that's being used, two things to observe:

1. It was a quick test which I would like to see others repeat although I did go to great lengths to ensure I was trimmed as stable as possible hands-off.
2. It isn't really stick-free as my stick is held central by the springs, so a 'light hand' on the stick if you like. We can't represent stick-free unless someone has FFB (I know nothing about how FFB sticks would be affected by this). That might do it.

[ACE-OF-ACES]

Originally Posted by klem

2. It isn't really stick-free as my stick is held central by the springs,

Agreed 100%

Originally Posted by klem

so a 'light hand' on the stick if you like.

Depends of the JS.. Some have very stiff spring, some don't. Just too many variations to say one way or another.

Originally Posted by klem

We can't represent stick-free unless someone has FFB (I know nothing about how FFB sticks would be affected by this). That might do it.

Maybe.. But there are variations even in FFB stick.. For example, the Microsoft FFB2, when you take your hand off the stick, the FFB is disabled, where as others will simulate springs and pull the stick back towards center.

In summary, apparently Crumpp has not thought this one through all the way.. There is limitations in the PC simulating a plane.. Flying qualities and seat of the pants types of feedback are something we may never obtain with a $1,000 PC and a $50 game. Long story short, no flight simulation ever was, is, or will be real, hence the name 'simulation'. Once Crumpp comes to grips with that simple truth, than and only than will he realize how silly most of his Spitfire simulation arguments are.

[bongodriver]

Even with a FFB stick the game will not recognise the user has taken their hands off the stick and therefore it will still assume it is just being held in whatever position the stick ends up, try it, move a FFB stick without covering the sensor to activate FFB and you can still make inputs, the game will just not simulate stick-free.