Spit IIa

[CaptainDoggles]

Do you have sources for those numbers?

[Crumpp]

You can look in the FAR.

http://rgl.faa.gov/Regulatory_and_Gu...4!OpenDocument

The stick rates comes from:

NACA RB No. L4E31

ORIGINALLY ISSUED

May 1944 as Restricted Bulletin L4E31

MAXIMUM RATES OF CONTROL
FROM GROUND TESTS

By De E. Beeler

[Crumpp]

As for the original premise of this discussion, the effect of a hard buffet for stall warning on turn performance:

Aircraft with shallow stick force-per-g gradients
can feel dramatically sensitive if your muscle
memory expects greater forces. Even
experienced aerobatic pilots stepping up to
higher performance aerobatic aircraft usually
find themselves pulling too hard, detaching the
boundary layer, and buffeting the
aircraft—especially in the excitement of
aerobatic competition. This is seen from the
ground as an abrupt flattening in the arc of a
loop, and from the cockpit as a sudden g-break.

http://www.flightlab.net/Flightlab.n...u%232BA152.pdf

In the absence of boundary layer devices, buffeting will increase the radius and decrease the rate of a turn. The harder the buffet and larger the buffet zone, the more dramatic the result.

Stall warning is another engineering trade off. If you produce an airplane with large amount of stall warning, it will not achieve best rate of turn at 2D CLmax. The less buffet with smaller buffet zone and less stall warning, the closer to 2D CLmax the aircraft can achieve best rate of turn.

[CaptainDoggles]

Originally Posted by Crumpp

You can look in the FAR.

http://rgl.faa.gov/Regulatory_and_Gu...4!OpenDocument

The stick rates comes from:

NACA RB No. L4E31

ORIGINALLY ISSUED

May 1944 as Restricted Bulletin L4E31

MAXIMUM RATES OF CONTROL
FROM GROUND TESTS

By De E. Beeler

Thanks

[RAF74_Winger]

Originally Posted by Crumpp

53lbs would be considered the minimum control force the pilot should experience at a 6G acceleration.

Originally Posted by Crumpp

7500lbs/140 = 53lbs

Selective reading, again. The linked document actually states this: (2) For stick controls, W/140 (where W is the maximum weight) or 15 pounds, whichever is greater, except that it need not be greater than 35 pounds.

The spit Mk1 MTOW is 5,844 lb BTW, gives me 42 lbs according to the FAA formula for chimp-proof civil aircraft.

Originally Posted by Crumpp

IIRC, in the case of the NACA test, the stick force at CLmax was ~22lbs.

At what speed? What was the resulting acceleration? You're only telling half the story.

W.

[IvanK]

NACA did not classify the Spitfire as Unacceptable what it actually said was .."therefore failed to meet the accepted requirements" (NACA's referenced requirements ... nobody else's) and to a specific item. If you read the various NACA reports in their entirety you don't come away with the impression that the Spitfire was a POS from a handling point of view.



They also said with respect to being able to rapidly pull to Clmax without the risk of stalling:



Something most Fighter pilots would consider a highly desirable characteristic.

CRUMPP you said above:

"As for the original premise of this discussion, the effect of a hard buffet for stall warning on turn performance:"

The premise of the discussion was NOT flying in Hard Buffet at all ! but on the very first indication i.e. The "Buzz" or the "Nibble" or the "Burble" ... what ever you want to call it. In a previous post you erroneously said the Buzz and Buffet I described was in fact the stickshaker going off even though in these aeroplanes no stickshaker system was fitted, you also told me that it was only valid technique in FBW aircraft ... even though we were talking about coventional cable/pushrod flight control systems ! You fail to accept that flying on the Buzz was/is a technique practised by Fighter pilots the world over and examples provided in this thread from at my count by 4 independent people/references ... by those that have actually used the technique....including a Spitfire pilot from the Battle Of Britain.

[Crumpp]

"therefore failed to meet the accepted requirements"

Ok - I admit I shortened "failing to meet acceptable requirements" to just "unacceptable."

Was I wrong?

you don't come away with the impression that the Spitfire was a POS from a handling point of view.

Nobody said it was a POS. There are some very good qualities the Longitudinal Instability gave the aircraft from a flying perspective. I love the Spitfire.

It was a two fingered aircraft and one can see how its pilots felt all you had to do was "think about it" and the plane responded. It is an airplane a highly skilled pilot would have love to fight in.

In rough air, Instrument conditions, as a gun platform, precision landing or precision aerobatic platform, the early marques could best be described as skittish. It certainly was not ideal for those missions and a more stable aircraft would not require as high a degree of skill to perform the same maneuvers.

In terms of your game, the excellent stall warning the type possessed means that any computer FM based on 2D Clmax calculated turn performance is optimistic.

They also said with respect to being able to rapidly pull to Clmax without the risk of stalling:

No they don't say CLmax, they say maximum lift coefficient and they list those coefficients achieved in the report. That makes it very easy for somebody who wants to program a computer game, btw.

That is the source of the confusion between the NACA and the RAE. Somebody at the RAE thought it was 2D Clmax too.

Something most Fighter pilots would consider a highly desirable characteristic.

Again, a skilled pilot would love it. He could pull very quickly to the burble and back off to the point just before to achieve that maximum lift coefficient to make his best rate of turn. All within ~3/4 of an inch of stick travel.

NACA's referenced requirements ... nobody else's

The United States had the ONLY stability and control standards during the war on the Allied side.

Only Germany and Japan had stability and control standards at the beginning of the war. The NACA was the first Allied organization to develop any standards. The British never did during the war and it was not until post-war that they came on board to develop any.

Remember, a stable airplane can do any maneuver an unstable aircraft can. The stable airplane can do it just as fast and more precisely requiring a less skilled pilot to do the same thing. It can also do things the unstable one cannot. Such as not destroy itself by overloading the airframe, shoot down other airplanes much faster, land with more control and precision, maneuver better in rough air, and hold a precise altitude/heading in instrument conditions.

[Crumpp]

It is amusing insight to human perception that some of the pilots were not happy when the RAE did address the Longitudinal Instability of the early marques. Some pilots actually felt the bob weights took away the maneuverability.

All they did was increase the stick force gradient to make the longitudinal control heavier. Bob weights do not effect the dynamic pressure acting on the control surface or even the hinge coefficients.

Bob weight force is simply added to the force gradient already present to achieve a higher stick force per G resulting in the perceived stick forces achieving the minimum standards.

[Crumpp]

Thanks

You are welcome!

[Crumpp]

The premise of the discussion was NOT flying in Hard Buffet at all ! but on the very first indication i.e. The "Buzz" or the "Nibble" or the "Burble" ... what ever you want to call it.

Why do you think I disagree with you?

Yes the correct technique to achieve maximum rate of turn performance without FBW is to fly to the first indication of flow separation and back off to the point just before that flow detaches.

Tell me this, does CoD model the effects of the stick shaker zone or does maximum rate of turn performance occur at 2D CLmax?