Leading Edge Slats on the Me-109

[robtek]

Originally Posted by ACE-OF-ACES

Don't be sorry

In that I fully expected you and yours standard off topic reply in an attempt to take the focus off what I said..

Not to mention how you and yours totally ignored the points I brought up about the historic accounts of the Bf109 slats causing more spin issues than they solved..

Now there you have to bring some proof that the assymetric action of the flaps, which was intended, was causing spins.

And the points you've brought are as usual black and white with no room for intermediate.

[Al Schlageter]

Originally Posted by robtek

Now there you have to bring some proof that the assymetric action of the flaps, which was intended, was causing spins.

And the points you've brought are as usual black and white with no room for intermediate.

Isn't this thread about SLATS?

[*Buzzsaw*]

Originally Posted by robtek

If you reduce it to that, the key point is that the 109 is controlable all the time, even in a high speed stall, and its adversaries aren't, which is a great achievement by itself and should be represented in game.

This is a fundamental misunderstanding which comes up again and again in the course of discussions re. the 109's 'controllability'.

An aircraft in a stall is out of control by the very definition of the word 'stall'.

It is no longer in flight. It has ceased to be anything but a falling object. Maybe the 109 will fall in a predictable and logical fashion, but it is still falling.

A 109 in a stall is out of control. No if's, and's or but's.

Can a 109 be recovered fairly quickly?

Yes, but a recovery requires the standard stall recovery procedure, ie. centered or slightly forward controls, allowing the aircraft to gain speed and lift, and gentle application of controls only after the normal conditions for flight have been re-acquired.

A stall in a 109 like any other aircraft is going to result in loss of control and height. Perhaps the stall can be recovered fairly quickly, but recovery is still a requirement. While the aircraft is out of control, it cannot be flown in any normal sense. Any attempt to 'fly' a stalled aircraft is going to increase the severity of the stall, and prolong the time the aircraft will remain in a stall. Want to put a 109 in a spin? Continue to try to 'fly it' after it has entered a stall.

To quote again the RAE report on LOW speed turn stalls:

When the slots were fully open the aircraft could be turned quite steadily until very near the stall. If the stick was then pulled back a little more the aircraft suddenly shuddered, and either tended to come out of the turn or dropped its wing further, oscillating meanwhile in pitch and roll and rapidly losing height ; the aircraft immediately unstalled if the stick was eased forward. Even in a very tight turn the stall was quite gentle, with no tendency for the aircraft to suddenly flick over on to its back and spin.

Note the requirement for the stick to be eased forward (brought forward GENTLY) to allow the aircraft to regain speed and lift. Standard stall recovery. Any attempt to use the controls to do other than stall recovery would result in a prolonged stall.

[*Buzzsaw*]

Originally Posted by robtek

As usual the answer is only refering with evidence that is supporting the posters opinion and hair-splitting.
1. Did the 109 recover from a high speedstall with only minimal control input? The RAE report says so. Hardly a uncontrolled flight situation then, i'd say.
2. Did the early Spitfire depart from controlled flight in a high speed stall with a flip over and a following spin? Afaik all sides so far have admitted that.

There is no dispute that the controlled stall in the Spitfire was not hard to manage, but then, that was not asked for.

As has been mentioned several times on this board, the Spitfire's stall was very easy to read and anticipate. Even rookie pilots were capable of learning this, and even in a high speed situation:

From FIRST LIGHT, by Geoffrey Wellum

"I start to black out. Must be pulling 6 G's. Lean forward, raise my feet on to the rudder pedal extensions; God, they're heavy.
The Spit judders, a high speed stall. You can hold a Spitfire on this judder if you're good. Hold on, Geoff! Hold onto this turn. Fly her like hell.

I reckon I'm just a little above, just a fraction, and therefore gaining.

The German pilot is trying to tighten his turn still more to keep up with me and I'm sure I see the 109 flick. I can see the shape of his head quite clearly and even the dark shape of his oxygen mask. Yet again, I imagine that the 109 gives a distinct flick, on the point of a high speed stall. He has to ease his turn a fraction. The Spitfire gains slowly.

I can quote quite a number of other examples.

The Spitfire's 'judder' or shudder or buffet happened before the stall, and it was quite possible to ride this edge for maximum turn rate.

Only those who were ham-handed or completely inexperienced would not know how to use this indicator.

Yes, if pushed beyond this, the Spitfire would flick over on its back and spin, but given the fact its stall speed was lower than the 109's, and it turn circumference was smaller, there was no need to for a pilot to take it that far.

Notice also in this description the 109 'flick' referred to. This is mentioned in many combat accounts, and tells us clearly that in an accelerated stall condition, there was the potential for a wing drop on the 109 if the stall indications are ignored and controls continue to be over-applied.

[Crumpp]

Taildraggernut says:

I am struggling to find an aspect in that report saying the Spitfire should spin wildly out of control

From the Spitfire Mk II Operating Handbook. The same warning appears in all early mark Spitfires:



Roll instability near the stall as noted the NACA agrees with the Operating Note warnings:



That help?

[*Buzzsaw*]

Thanks for providing that documentation to bolster my comments.

Originally Posted by Crumpp

Roll instability near the stall as noted the NACA agrees with the Operating Note warnings:

"The Spitfire possessed GOOD stall warning in the form of buffeting....
...the stick could be moved well back before lateral instability occurred"

"...rolling instability was noted AFTER an unmistakeable warning in the form of buffeting occurred."

Of course the Spitfire's capability of entering a spin off a high speed stall has nothing to do with the 109's slats.

However, I guess this thread has established two things which are incorrectly modelled in the game:

1) The 109's tendency to enter spins easily and the tendency for recovery from spins to be difficult.

2) The lack of modelling of the Spitfire's pre-stall buffeting.

The game Spitfire will clearly enter a spin out of a high speed stall through the path of a flick onto its back.

[Crumpp]

The lack of modelling of the Spitfire's pre-stall buffeting.

I agree.

The pre-stall buffeting of the Spitfire and its effects should be modeled.

it was quite possible to ride this edge for maximum turn rate.

Yes, except maximum turn rate occurs in smooth airflow not buffeting. The buffet is often used to find this point and then backing off to smooth air.

If you turn in the buffet, your rate will decrease and your radius increase.

The more high energy the buffet, the greater the effect.

[NZtyphoon]

Originally Posted by Crumpp

I agree.

The pre-stall buffeting of the Spitfire and its effects should be modeled.



Yes, except maximum turn rate occurs in smooth airflow not buffeting. The buffet is often used to find this point and then backing off to smooth air.

If you turn in the buffet, your rate will decrease and your radius increase.

The more high energy the buffet, the greater the effect.

Of course Crumpp fails to point out the pre-conditions noted in the NASA report, steeply banked turns with open gun ports; nor does the report state that the instability was actually dangerous, and it does not explain how all of this affected the Spitfire in combat or as a combat aircraft. Nor does Crumpp explain that the Spitfire's stall behaviour was more often praised than slated by NACA, in this and in another report on the Spitfire's stalling characteristics.

And, of course, this is not about the Spitfire anyway - Crumpp has obsessively chased this subject already in other threads - but as to modelling this pre-stall buffet, perhaps, crumpp could develop a program which will allow all gamers to feel this buffeting, either through their joysticks, or the seat of their pants?

[Glider]

Originally Posted by Crumpp

I agree.

The pre-stall buffeting of the Spitfire and its effects should be modeled.



Yes, except maximum turn rate occurs in smooth airflow not buffeting. The buffet is often used to find this point and then backing off to smooth air.

If you turn in the buffet, your rate will decrease and your radius increase.

The more high energy the buffet, the greater the effect.

For once a posting that I totally agree with.

As to how to replicate the buffet in the game, I suggested once that in the ideal world everyone would have a feedback controller which would vibrate. However we have to recognise that this will not be the case so I suggested a visual cue where the cockpit view would vibrate.

Now back to the question yet to be replied to

Crumpp
Do you tell your students that leading edge slats :-
a) are a device that delays the stall or
b) Is an anti spin device.

Do you agree that the correct solution is (a)?

[taildraggernut]

Originally Posted by Crumpp

From the Spitfire Mk II Operating Handbook. The same warning appears in all early mark Spitfires:



Roll instability near the stall as noted the NACA agrees with the Operating Note warnings:



That help?

Yeah, so only 'AFTER' the Spitfire has actually fired it's guns does it begin to suffer any form of lateral instability, just got to make sure the first burst counts then.
Like NZtyphoon says, Crumpp completely ignores the 95% of positive report on the Spitfire but emphasises the negative 5%, NACA summaried their report saying the Spits stalling characteristics were it's redeeming feature.