HT, a Question about the Spit FM:

[dtango]

Originally posted by MajWoody
...Very unrealistic. The weight of the engine should cause the nose to drop off like a lawn dart.

You need to think through the physics.  Most WW2 planes were designed to be positively stable.  Planes have a center of gravity which the forces are balanced around in flight.  Longitudal look at this means that the moment forces on either end of airplane balance each other out.  Granted this usually means the forces in play as the the plane is in normal flight.

But really you don't have to go far to look at this.  Again if the weight of the engine should pull the nose down all the time that means you would never have flat spins/stalls ever in real life.  We know this isn't the case.

Tango, XO
412th FS Braunco Mustangs

[dtango]

BTW - cool little film of a mossie pancake there WW .  I fly the Mustang exclusively so I only know about the nasty flat spins I get into with that bird.

Tango, XO
412th FS Braunco Mustangs

[MajWoody]

Ok
For the flat stalls & spins I will have to agree with you but a tail slide all the way down to the ground from10 k, is this realistic?

[Krusty]

I don't think so. Even if you were somehow in the position where you were sliding arse-first downward, with no roll or oscilation, you've got one thing to get you out.

The rudder is biting directly into the airstream, like a knife, even. There's no way it wouldn't respond. Kick a little rudder and all of a sudden the air has a huge flat surface to slam into (the stab), and now you're oscillating and can get out of it.

That doesn't work in AH. I think it's a bug when it happens in here.

[cav58d]

Originally posted by dtango


Here's an example of a real inverted flat spin done albeit on purpose by an acrobatic pilot in a stunt plane who can recover from it:
http://www.bulldogairshows.com/video/1997promo/flatspin.avi

[/B]

Prove it.  I see no recovery. HEHE

[MajWoody]

I have not flown the Ki in about a year so I tried to reproduce it off line. The thing I didn't remember was that it was a spinning tail slide. I finally was able to get the nose down but it was too close to the ground to pull out.

[Vulcan]

Originally posted by Krusty
I don't think so. Even if you were somehow in the position where you were sliding arse-first downward, with no roll or oscilation, you've got one thing to get you out.

The rudder is biting directly into the airstream, like a knife, even. There's no way it wouldn't respond. Kick a little rudder and all of a sudden the air has a huge flat surface to slam into (the stab), and now you're oscillating and can get out of it.

That doesn't work in AH. I think it's a bug when it happens in here.

Are you sure about that.

Imagine a parachute with a weight and rudder at one end. The rudder may oscillate a little bit it won't flip the chute over. Now think about the prop and the drag it produces in a tailslide.

[Charge]

Why does an a/c stay in a flat spin?

"With adequate training an incipient spin is readily anticipated and easy to correct – provided the aircraft weight and balance are within the stated limits – but if the correction is not done before the nose has swung maybe 90° or so, it may develop into autorotation where the aircraft is descending in a stabilised nose down rotation – rolling, pitching, slipping and yawing at a constant airspeed at or slightly above Vs1 – a full blown spin with each 360° rotation taking only 3–5 seconds. The height loss during each rotation – 150 to 450 feet or more depending on the stall speed – plus the considerable height loss during the pull out from the recovery dive, is insignificant at a reasonable height but will be critical at lower levels. "

http://www.auf.asn.au/groundschool/umodule8.html#turns

Notice: "aircraft balance" If, for some reason, the weight likes to stay behind the center of lift, maybe because of rotational forces, the a/c could be impossible to recover until the rotation speed is decreased. It does eventually when the a/c hits the ground... But seroiusly getting out of autoration spin needs timing to counter the movement and getting into a favourable position to establish positive control force.

Same page: "Aircraft which tend to spin with the nose pitched well down will recover more quickly than an aircraft where the spin attitude is relatively flat. However if allowed to continue past two or three full turns then centrifugal forces become well established – which tend to make all parts of the aircraft rotate in the same horizontal plane – and a nose down spin may turn into a flat spin, which will then speed up rotationally and break-out will take longer, or may not be possible because it may be impossible to lower the nose. Engine power – and its associated effects – also tends to flatten the spin. The flatter the spin the closer the spin axis is to the cg and the greater the aoa, maybe 60° or more! Also at such angles the rudder may be completely blanketed by the fuselage, making that control quite ineffective. Structural stresses increase as the spin progresses. A flat spin might be induced if, at the point of stall, full opposite aileron is applied with full rudder."

Same page still: "Spin restrictions are not confined to non-aerobatic aeroplanes, for example intentional spins were prohibited in the Seafire 47 and Sea Fury, very fast naval fighters of the late 1940s early 1950s, because of the time to recover and the consequent extreme height loss."

Interesting. These are Griffon engined Spits but what wing? The newer wing with laminar flow?

"The Spitfire Mk XIV (the massively over torqued one) had to be held in a spin or it would recover on its own after two or three rotations."

To left or to right? It has the Griffon, right? If it is spun into the same direction as the Merlin engined it probably likes to straighten itself by torque alone. But what happens if it is spun to direction it naturally likes to spin...

-C+

[Ghastly]

Another factor that I'm sure plays into the unrealistic behaviour of every flight sim I've ever played when it comes to modeling departed flight is that in real life, air isn't "perfect".  It has localized movements, and layers of varying densities and tempuratures, etc.

But in the sims, we have perfect air.  And if we have wind, we have perfect wind. It stands to reason that some events that are possible in sims "at the edge of the flight model" would be extremely unlikely in real life as a result.

In sims, if you hit upon the "ideal" balance of forces and conditions for some abherrant behavior, you'll have the same constant ideal conditions until you smacktard or manage to "break" the balance yourself.

Whereas in real life, the environment is constantly in change, so there is more of a chance that external factors would break the balance for you.  



Grue

[dtango]

Originally posted by Krusty
I don't think so. Even if you were somehow in the position where you were sliding arse-first downward, with no roll or oscilation, you've got one thing to get you out.

The rudder is biting directly into the airstream, like a knife, even. There's no way it wouldn't respond. Kick a little rudder and all of a sudden the air has a huge flat surface to slam into (the stab), and now you're oscillating and can get out of it.

That doesn't work in AH. I think it's a bug when it happens in here.

Read:...

Various things can go wrong with a hammerhead, including a tail slide if the pilot is late with rudder. If the airplane rotates about its spanwise axis, a startled pilot might suddenly apply forward stick together with the rudder and unwittingly set up the conditions for an inverted spin entry.

http://www.flyingmag.com/article.asp?section_id=14&article_id=699&print_page=y

Tango, XO
412th FS Braunco Mustangs

[Major Biggles]

some of you are confused about what i'm referring to. i'm not talking about spins, flat spin, high AoA stalls, or ANYTHING like that. the spit, and ONLY the spit, enters an inverted stall when you are moving slowly with flaps out, and you roll over the top of a rolling scissors and cut throttle slightly.

it turn the plane upsaide down and the plan drift straight downwards, lying perfectly still on it's back, 90 degrees to the vertical. it falls like that, no spin, nothing, just falls like a brick. in the spit5 the stall is just about recoverable if you have the altitude, as the engine doesn't cut and you can build up enough air over the controls to wriggle out.

in the spit 1 however, the engine cuts out so you have no chance at all of exiting this stall.


my point is:

this should not happen in either pane, the stall is not realistic, the stabilisers would right the plane, as it is travelling downwards. the airspeed on the stabs would act as it would on a windvane and puch the nose into the wind (straight down in this case)

perhaps it is this that is not modelled, the effect of the stabilisers when the plane is not moving (the plane moves down, but vertically upwards as it is inverted, if you understand what i mean). seeing as their is no forward motion, perhaps the game does not register any air resistance and the stabs have no effect?



HT, this is really a question for you, why is it that the spit does this? is it a bug? is it an unfortunate sacrifice in the spit FM? what's going on?

it would be great if i could get an answer to better understand why it does it so that i can avoid it. ideally, i would love it to be fixed, if it is indeed an error.

thanks HT

[Krusty]

Originally posted by Vulcan
Are you sure about that.

Imagine a parachute with a weight and rudder at one end. The rudder may oscillate a little bit it won't flip the chute over. Now think about the prop and the drag it produces in a tailslide.

No I'm not sure about it, but your parachute analogy isn't an accurate one. Most fighter aircraft in WW2 were well balanced. That is, they aren't very tail heavy and they aren't very nose heavy.

A parachute has all the weight at the very end, and is self-stabilizing. An airplane that is balanced around a central point is not going to self-stabilize in a tail slide, especially not if you kick rudder while it's biting into the wind.

[stockli]

wouldnt the tail stab act like veins on on arrow?

More wind resitance in the back of the plane than in front, so the nose would be pushed down?

Arrows have a center of gravity, mid shaft.

Given enough alt (read or speed), they will always fly tip down.

I assume the same would be true in a plane.

[Major Biggles]

Originally posted by stockli
wouldnt the tail stab act like veins on on arrow?

More wind resitance in the back of the plane than in front, so the nose would be pushed down?

Arrows have a center of gravity, mid shaft.

Given enough alt (read or speed), they will always fly tip down.

I assume the same would be true in a plane.

exactly my point, yet the plane just sits inverted, 100% chance of death...

the stabilisers would point the nose down.

[Jenks]

I posted about the Spit I Upside Down Float To The Ground issue back during BoB 2006. I think I posted first in the BoB forum and then Shatzi or someone suggested I post in the Bugs forum. I did so and never got a response from HTC about it.
 Your idea about the FM not recognizing the air traveling across the airfoils at 90degree from normal seems a likely reason but it is prolly more complicated than that.
 I have got into this attitude many times in the Spit I and have  NEVER been  able to recover.  I recall that there is a slight wobble in the pitch of the airplane with the stall horn going off and on but ther is no spin around the vertical axis.
 I did SOME research online about spins in the Spit and never found even a hint of anything like this.

Jenks