f6f-5 vs 109

[Soren]

But it's the same for every a/c Bill, that's really all I'm trying to point out here.

The high wing will always be creating slightly more lift, and so wether it has slats or not wont make a difference, it just means an increased critical AoA for both wings. The slats start to extend at around 10 to 11 degrees AoA and fully extend at around 14 to 15 degrees AoA, so when pulling hard turns the slats are deployed fully symmetrically.

[drgondog]

Originally Posted by Soren

But it's the same for every a/c Bill, that's really all I'm trying to point out here.

Soren - every wing exhibits same type behavior in a turn. Pause here and think about the relative chord angle from leading edge of each wing to the trailing edge of the aileron. They are at Different angles relative to the freestream AoA

The high wing will always be creating slightly more lift, and so wether it has slats or not wont make a difference, it just means an increased critical AoA for both wings.

Yes to the high wing having both a slight increase in lift, no to the low wing having a slight increase in lift.

The low wing has a lower critical AoA, particularly at the aileron area. It has an effective angle of attack due to the effective chord (leading edge of wing to trailing edge of flap) which Reduces the AoA to the lower wing aileron area.

The slats start to extend at around 10 to 11 degrees AoA and fully extend at around 14 to 15 degrees AoA, so when pulling hard turns the slats are deployed fully symmetrically.

Not likely.

With the lower effective freestream AoA (relative to aileron deflection change in effective chord) on the down wing it tends to enter the stall AoA for the aileron region later, after the high wing is already entering into stall AoA for the aileron region.

The high wing slat is activated by the impending stall before the low wing.

Statistically, because of wake turbulence that may be encountered in a turn chasing another a/c, the slat deployment may happen at the same time if the lower wing encounters indicial gusts which increase the relative AoA instantaneously over the freestream AoA.

[Soren]

I'm not entirely sure what it is you're trying to suggest Bill but it seems to go against what every pilot of the type says, and I certainly haven't experienced anything negative flying a slat equipped a/c. All I've experienced is a notable increase in turn performance, esp. a low speeds.

But to get back to the subject at hand;

Since the slats start to deploy already at 10 degrees AoA (On the 109 according to MTT documents) and are fully deployed at 15 degrees AoA (which is still 2 degrees from the original airfoils critical AoA), both slats will be fully deployed (aka symmetrically) in any form of high performance turn. The stall will occur at around 20 degree's AoA.

[drgondog]

Originally Posted by Soren

I'm not entirelysure what it is you're trying to suggest Bill but it seems to against what every pilot of the type says, and I certainly haven't experienced any of that flying a slat equipped a/c. All I've experienced is a notable increase in turn performance, esp. a low speeds.

But to get back to the subject at hand;

Since the slats start to deploy already at 10 degrees AoA (On the 109 according to MTT documents) and are fully deployed at 15 degrees AoA (which is still 2 degrees from the original airfoils critical AoA), both slats will be fully deployed (aka symmetrically) in any form of high performance turn. The stall will occur a around 20 degree's AoA.

I believe the data. Where we are bogged down is visualizing the physics of the outboard span of the wing where the outer edge of the slat exists and the aileron exists. These are two extra lift devices for the wing in flight

Soren, take the slats out of the discussion for now.

Break this down to a 'local wing-upsdide' and a 'local wing-downside'

The LW-U has a 'flap (aileron) which deflects down. This 'new' condition for that LW-U is now experiencing is one of a.) increased Lift, b.) increased drag and c.) an increase in the 'local AoA' of the Freestream to the 'new' LWA environment.

Bring the wing back in for the outboard span area.

With the deflection of the aileron for LW-U the effective chord line of the airfoil/aileron ('flap') from leading edge of the wing (and slat) to the trailing edge of the aileron. For small to medium deflections this local effect increases Camber And Chord angle to the freestream.

For the LW-U this results in an immediate increase in local AoA to the freestream, increased Lift (just like a flap deflection in landing) and increased drag.

Bring the slat back in. It senses the pressure distribution behind the outer region of the slat as the AoA of the entire wing closes on 10 degrees.

But the slat on the LW-U will experience that change earlier because the local AoA of the aileron region (and outboard slat region) is higher than the inboard section of the wing. This upwing slat should start the deployment slightly earlier than it would if the aircraft was in level, symmetric flight.

The lift distribution on the inboard span does not change perceptibly, but the outboard span increases its lift (and drag) contribution from level flight with same AoA to wing and airframe.

The exact opposite scenario will occur for LW-U which has equal but Negative lift and the same drag - but the new 'effective chord' and angle to Freestream has the Opposite effect on local AoA, which reduces the local Lift/Drag of that aileron region of span relative to the inboard wing.

On the lower wing, the inboard span experiences no perceptible change in lift, but the outboard span decreases its Lift contribution in comparison to level flight.

Think of this in a different way. When the Up Wing Aileron deflects down - it is similar to locally reducing the twist of the wing and locally increasing AoA and locally increasing Lift and Drag - whereas the Down Wing aileron deflection Up Increases local twist and Reduces local Lift, Drag and AoA.

The Up wing will 'tug' on the airframe more than the Down wing and in parallel the Up wing slat should start to deploy slightly sooner than the down wing.

The pilot flying this aircraft should not sense anything unusual except he will be applying slightly more rudder than he would if the slats are 'wired shut'.

I don't know another way to describe this.

[Soren]

Oh I understood from the beginning, but I've never heard anyone comment about using more rudder than usual in slat equipped a/c, and I've never experienced it myself. But if it is the case then it is extremely minute and insignificant, so much so that it really can't be sensed.

[drgondog]

Originally Posted by Soren

Oh I understood from the beginning, but I've never heard anyone comment about using more rudder than usual in slat equipped a/c, and I've never experienced it myself. But if it is the case then it is extremely minute and insignificant, so much so that it really can't be sensed.

>Since the slats start to deploy already at 10 degrees AoA (On the 109 according to MTT documents) and are fully deployed at 15 degrees AoA (which is still 2 degrees from the original airfoils critical AoA), both slats will be fully deployed (aka symmetrically) in any form of high performance turn. The stall will occur at around 20 degree's AoA.>

Where I underlined your comment would suggest that you didn't quite understand the concept of a modest asymmetrical early deployment of the high wing slat first. I am not suggesting it is a 'zero to full' slat deployment as they don't work that way.

Since you have to fly simultaneously in two exact same aircraft -one with/one without slats deployed - how would you know how much incremental rudder was required?

Which slat equipped aircraft do you have time in?

[Soren]

I haven't flown two otherwise identical a/c, one with slats and one not, but I fly the Cessna Aerobat, and I've tried several STOL a/c of the same weight, and they do turn a lot better.

Also we flew 3 STOL a/c in formation once, chasing each other, and I never felt any disturbance to the slats. Ofcourse I could feel the propwash, but so would I in any a/c.

And regarding what I said about the slats being deployed symmetrically, I was talking about a high performance turn where both wings have exceeded 15 degree's AoA, at that point both slats will be fully deployed and are therefore symmetric.

[Glider]

I only flew in an Aerobat a couple of times some years ago and could be very wrong, but I thought they had Fowler flaps, not leading edge flaps as in the 109 which would perform quite differently.

[Soren]

The Aerobat doesn't have slats.

[Glider]

Thats what I thought

[Soren]

I mostly fly the aerobat, but its' been a while now since I sold it. I worked out a deal where I can get to fly it when'ever I want though, as long as I pay for the gas. It's a great little a/c, but the STOL (A CH107 once IIRC) a/c I've tried were definitely better at tight maneuver, despite having roughly the same wing loading, and the slats were no doubt the reason behind that.

[Glider]

I admit that I didn't like the aerobat, it was tight for space and I didn't like the visibility. However I wasn't paying so wasn't in a position to complain.

[drgondog]

Originally Posted by Soren

I haven't flown two otherwise identical a/c, one with slats and one not, but I fly the Cessna Aerobat, and I've tried several STOL a/c of the same weight, and they do turn a lot better.

Also we flew 3 STOL a/c in formation once, chasing each other, and I never felt any disturbance to the slats. Ofcourse I could feel the propwash, but so would I in any a/c.

And regarding what I said about the slats being deployed symmetrically, I was talking about a high performance turn where both wings have exceeded 15 degree's AoA, at that point both slats will be fully deployed and are therefore symmetric.

That would be true... at the point of near stall.

I have never seen any data about the rate of deployment for the 109 so I really don't know what the characteristics would be from say, 13 degrees to 17 degrees. I suspect it is gradual (post E) and entirely dependent on the local pressure distribution of the airfoil behind the slats.

[88l71]

Originally Posted by lesofprimus

And for the love of God, would u please cease and desist in calling the Hellcats firepower "devestating/massive"... It was adequete for the job and should of had cannons...

The F6F was notoriously rugged, and hard for a Zero to bring down, and the Zero had double the cannon armament of the 109. The P-51, which had the same firepower as the F6F, had no trouble bringing down the Messerschmitt. So since we're comparing two aircraft in a hypothetical combat it's about relative firepower, not absolute. The Hellcat is a very large fighter, almost the size of a P-47, with a reputation for extreme ruggedness while the 109 is a much smaller and lighter airframe.

[DerAdlerIstGelandet]

Originally Posted by 88l71

The F6F was notoriously rugged, and hard for a Zero to bring down, and the Zero had double the cannon armament of the 109. The P-51, which had the same firepower as the F6F, had no trouble bringing down the Messerschmitt. So since we're comparing two aircraft in a hypothetical combat it's about relative firepower, not absolute. The Hellcat is a very large fighter, almost the size of a P-47, with a reputation for extreme ruggedness while the 109 is a much smaller and lighter airframe.

Would you like to explain "no trouble"?