Auto leading edge slats of the 109

[Crump]

 

You don't know what you don't know- just about everything you've posted is wrong

 

 

Present some documented evidence I am wrong and I will be the first to agree.  The A4 manual excerpt for the Aggressor modification is posted.   I have owned and flow aircraft with Handley Page LE slats as well as being well versed in the aerodynamics.

 

Rama,

 

 

Swinging a mass on a string requires string tension, and the mass will travel off in a tangential straight line if the string breaks.

 

http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html

 

Simply put your frame of reference on the carousel causes the confusion.  Inside the rotational frame of reference and object that looses centripetal force will appear to move in the rotation and fall away.  Outside of the rotational frame of reference it will move tangent to the circle.

 

 

 the non-attached objects in the planes are not directly affected by the lift, but only by gravity and forced induced by plane trajectory changes (so actually centrifugal forces in the case of a positive loop).

 

If you go back and read what I wrote to Bongo, you will see Rama I try to explain to him about the motion of objects not attached to the aircraft.  In fact that is key to understand what is going on.

 

If you ever experienced a loop while pulling a constant 4g, and have a pencil in your cockpit falling on the top of the canopy... then please make a video, because it would means you found the proof that the actual laws of physic are wrong.

If you fly formation and that to keep formation, at some moment on the top of the loop, you have to push the stick so you're pulling less then 1g... then yes, your body, and the non-attached objects in the canopy, will experiment negative g.

 

 

If you can get here, we will fly one today.  It is a beautiful afternoon!!  I would be happy to take you up for a loop or two.

 

My airplane does not have the thrust to fly a constant 4G loop though but it is not a modern jet fighter. 

Edited November 16, 2013 by Crump

[DD_bongodriver]

My airplane does not have the thrust to fly a constant 4G loop though but it is not a modern jet fighter.

 

 

So how will that help in regards to Ramas example of a constant 4g loop? more to the point even if you don't maintain a fixed g you will still in all probability maintain positive g, plus your Thorp has no slats.....what exactly are you going to show him?

 

If you go back and read what I wrote to Bongo, you will see Rama I try to explain to him about the motion of objects not attached to the aircraft.  In fact that is key to understand what is going on.

 

And herein lies the problem, you keep trying to explain things to people that appear to have a better understanding than you do, mainly because they are already qualified professionals.

Edited November 16, 2013 by DD_bongodriver

[Crump]

So a friendly offer to go flying is looked up with distain?

[Rama]

Simply put your frame of reference on the carousel causes the confusion.

There's no confusion. You don't understand what's a centrifugal force is.

 

I would be happy to take you up for a loop or two.

 

Don't need to.

Take a video of your g-meter during the loop, it should be enough to convince yourself about the reality of the newtonian mechanic.

With your alternative understanding of science, you will now try to convince us that one get a Redout while pulling on the stick and a blackout if pushing.

 

Now I'll stop there. I see clearly that continuing to try explaining you simple facts is useless.

 

I'll return to moderator's activities (not on this thread, I can't participate and moderate it, I'll leave it to other moderators).

[DD_bongodriver]

So a friendly offer to go flying is looked up with distain?

The offer was to Rama wasn't it? as yet I haven't seen him accept or turn it down, to be honest we don't even know if he could make you a better offer, if you are offering me the ride then I will decline with tanks for your kindness but I am already a qualified pilot with plenty of experience looping aircraft, as much as I'd be fascinated to try a new type I think travelling to North Carolina is not very cost effective for me.

[Crump]

How is that possible? neg g would push them closed

 

 

This comment was made about jet attack aircraft on an acro demonstration team.  Nothing in common with my Thorp. 

 

I pointed out the aerodynamics say that is not necessarily the case that the slats would be closed.

[DD_bongodriver]

This comment was made about jet attack aircraft on an acro demonstration team.  Nothing in common with my Thorp. 

 

I pointed out the aerodynamics say that is not necessarily the case that the slats would be closed.

Yes it was, and at the time nobody had even mentioned your thorp, what point are you trying to make now? not sure what you pointed out really, you started by talking about neg g in a formation loop and then illustrated an example with a constant positive g loop.

[Crump]

Good grief, like I said, you don't know what you don't know.  My Naval Aviator Wings, NATOPS Qual and experience in the very airplane in question are not enough- a FLAP knows better, after all, he has downloaded a maintenance manual for the wrong airplane. Guess I must have been hallucinating those hanging slats on all of those A4E, F and M's I fought. You know, the ones you looked for to reveal energy state while looking for to extend vertically for a kill maneuver?

 

Don't remember saying it did not happen.  Can you point that out?  I said it is not that big a deal once you are used to the slats.  Same thing Gunther Rall says or is he wrong too????

 

 

A constant 4 G maneuver in the vertical plane is not a loop.

 

If it goes in a circle....it is a loop.....

 

Just amazing at how many Embry Riddle boys and girls have similar attitudes. You may impress your dweeb buddies, but you look foolish to the Pro's.  Like I said, it is a waste of time arguing with someone who isn't technically versed to be able to understand.

 

Wow, most Embry Riddle boys are the pros......beat the hell out of the Naval Academy in Aeronautical Science/Engineering.

[MiloMorai]

[DD_bongodriver]

Same thing Gunther Rall says or is he wrong too????

 

Not sure, I seem to recall you not having much time for crediting pilots and their accounts........unless they back up 'your' arguments

 

 

If it goes in a circle....it is a loop.....

 

Technically but a real pilot would actually know what is being said here, the aerobatic manoeuvre known as a loop is flown with a finess that requires it to keep a good shape and result in minimal height loss, simply yanking the stick to maintain a constant g will result in nothing like an accurately flown loop.

Edited November 16, 2013 by DD_bongodriver

[Sternjaeger]

I know I'm gonna regret asking this, but... Crump, what did Gunther Rall say exactly?

[NZTyphoon]

 

[Gort]

Getting back to the salient point. I would guess, that having the Bf109 exhibit some uncommanded roll when the slats deploy when there is side slip present would replicate the real airplane. I am interested to hear from pilots who have flown the real one at high alpha, so if someone knows someone who has flown the airplane in this regime, please pass it along!

 

The other aspect is that if you do get some rolloff, you don't want to relax the pull, rather counter with co-ordinated aileron and rudder, especially when executing a vertical maneuver, and hold what you have in terms of aft stick. Otherwise, the slats retract, the enemy is still shooting at you, and you have to pull through the asymmetric slat deployment again!

 

I am amazed at the airplanes of the WWII era, and the guys and gals that flew 'em have my eternal respect.

Edited November 17, 2013 by Victory205

[Sternjaeger]

well sideslipping shouldn't be a problem, as long as you don't reach critical speeds. I'm sure you've seen this before, but if you haven't check out how this 109 is crabbed and landed 

 

 

http://youtu.be/5nj77mJlzrc?t=1m3s

 

To be honest I think we're all giving too much attention to the slats thing, when engine torque would be much more influential for roll stability.

[Gort]

Yes indeed, but the slats behave differently under high alpha, Q and G than during landing.

 

That said, I have no freaking idea as to how they behaved on the Bf109 in combat maneuvers or how much they influence lateral control by keeping the aileron effective. I hope the guys coding the sim do though!

[HeavyCavalrySgt]

Here we go again....

[Sternjaeger]

Yes indeed, but the slats behave differently under high alpha, Q and G than during landing.

 

That said, I have no freaking idea as to how they behaved on the Bf109 in combat maneuvers or how much they influence lateral control by keeping the aileron effective. I hope the guys coding the sim do though!

 

yep, the opening varied according to several factors, although the most influential ones were airspeed and AOA. With the introduction of the G series, there was a re-design of he opening mechanism, which now was on rollers, making the opening and closing of the slats more fluid and reliable.

 

Don't forget that the original design was the Handley-Page one, with the difference that they couldn't be locked. 

[Gort]

The A4's design was of the roller variety. The slats would bang out audibly, and on occasion, kept going. More than one Scooter came back missing a slat.

 

Calvary Sgt, crawl back into your tank, or onto your horse, or into your Warthog- which combined the two aforementioned concepts.

Edited November 17, 2013 by Victory205

[Quax]

Getting back to the salient point. I would guess, that having the Bf109 exhibit some uncommanded roll when the slats deploy when there is side slip present would replicate the real airplane. I am interested to hear from pilots who have flown the real one at high alpha, so if someone knows someone who has flown the airplane in this regime, please pass it along!

 

I thought i mentioned this, and that was why i was opening this thread. I wouldn´t have said anything, if i just quoted any net content.

 

 

 

During normal operations, approach and landing at one G, they were smooth and basically an afterthought. However, when maneuvering, you would get roll off during deployment, usually to the outside of the bank angle, associated with sideslip. The asymmetry caused guns tracking problems, and could also cause strange maneuvers during vertical pulls. 

 

This is pretty much, what my friend was telling me - and he got more than 1000 sorties on 109F,G with countless high G dogfights

 

And he said exactly the same thing than Rall: it was no problem, because you easily could avoid it. The issue is no big deal for the sim. But it would be nice, if it was modelled. 

Edited November 17, 2013 by Quax

[DB605]

I'm sure many of you have already seen this, but stil some interesting comments from Mark Hanna and Eric Brown.

http://www.eaf51.org/newweb/Documenti/Storia/Flying_%20109_ENG.pdf

Edited November 17, 2013 by DB605

[DD_bongodriver]

Yes, most of us have seen it, very good info and really goes most of the way to explaining everything needed to simulate their effect, the 109 slats were not a problem with asymmetric deployment as it was easily handled, they were essential for low speed handling and were not magic devices that 'stall-proofed' the aircraft......just like automatic slats on any other aircraft that employed them really.

[Kurfurst]

This article is good:  http://109lair.hobbyvista.com/techref/systems/control/slats/slats.htm

 

What is missing is the implication for the pilot:  They didn´t come out at the same time. Pilots tried to avoid them, because it could be very nasty in a close dogfight, especially on the deck.

It would be nice, if they wouldn´t come at the same time at least if the plane has a drift angle.

 

Even the E the only disturbance observed was some snatching of the ailerons as the slats opened (for 0,25 secs maybe?). The disturbance ceased when the slats were full open.

 

   Apart from their excessive heaviness at high speeds, the most serious defect of the Me.109 ailerons is a tendency to snatch as the wing tip slots open. This is particularly noticeable when manaeuvring. For example, if the stick is pulled back in a tight turn, putting additional g on the aircraft, the slots open at quite a high airspeed ; as they open, the stick suddenly snatches laterally through several inches either way, sufficiently to upset a pilot's aim in a dog fight.

 

   The snatch appears to be associated with the opening of the slots, for once they are fully open a steady turn can be done, with no aileron vibration, until the stall is approached.

 

   As mentioned in section 4.42 (ADM. 293) some aileron snatching also occurs when gliding near the stall with flaps up and slots open; it disappears on lowering the flaps fully, and so does not worry the pilot during the approach glide.

 

From: http://kurfurst.org/Tactical_trials/109E_UKtrials/Morgan.html , 4.6.

 

Apparantly with redesigned F/G/K wing and modified slat kinematic (rollers instead of swing arm) appeantly fixed this disturbance.

 

The idle power stall characteristics of the aircraft are very benign and affected little by undercarriage and flap position.  Stalling warning is a slight wing rock with the stick floating right by about 2 inches.  This occurs 10klph before the stall.  The stall itself is a left wing drop through about 15 degrees with a slight nose drop, accompanied by a light buffet.  All controls are effective up to the stall, and recovery is instant on moving the stick forward.  Stall speeds are 155kph clean and 140kph with gear and flap down.  In a turn at 280kphwith display power set, stall warning is given by light buffet at 3g, and the stall occurs at 3.5g with the inside wing dropping.  Again, recovery is instant on easing the stick forward.  One interesting feature is the leading edge slats.  When these deploy at low speeds or in a turn, a 'clunk' can be heard and felt, but there is no disturbance to the aircraft about any axis.  I understand that the Bf109E rolled violently as the slats deployed, and I am curious to know the difference to the Gustav that caused this.

 

http://www.109lair.hobbyvista.com/articles/airframes/black6/bk6_flight.htm

[Talisman]

I would like to be able to experience the feel of the aircraft and the snatching of the stick in relation to the wing slats through my force-feedback joystick, like I can with other aspects of flight.  It may not give me a 100% factual feel, but at least it would be something to simulate what the Bf 109 pilots felt and to have to react or manage the situation accordingly. 

Edited November 17, 2013 by 56RAF_Talisman

[Sternjaeger]

The snatching was more common in the series up to the F, and it was more due to mechanical limitations than anything. If the devs implement it, I don't think it'd be difficult to turn it into a FF input.

[Crump]

Yes, most of us have seen it, very good info and really goes most of the way to explaining everything needed to simulate their effect, the 109 slats were not a problem with asymmetric deployment as it was easily handled, they were essential for low speed handling and were not magic devices that 'stall-proofed' the aircraft......just like automatic slats on any other aircraft that employed them really.

 

I don't know where you get the idea for "stall proofed".  The term is actually spin and stall resistant.  Yes, slats are stall and spin resistance devices.  One can easily that in such reports as the RAE evaluation of the Bf-109 posted by Kurfurst.

 

 

 

Fixed slots in aircraft wings are used to increase the maximum coefficient of lift and delay the stall.

 

http://www.airspeedalive.com/writings/stallcharacteristics.html

 

Of course combine that knowledge with fact wings are designed to stall root first, putting the slats outboard over the ailerons adds greatly to the stall/spin resistance of the aircraft.

 

from the article entitled:

SPIN RESISTANCE

 

 

 

Wing leading-edge devices such as slots, slats, and flaps can significantly improve the autorotative resistance of unswept wings at stall, and early research at Langley by the NACA demonstrated the effectiveness of these devices.

 

http://whycirrus.com/engineering/NASA%20Stall%20Spin%20Paper%20from%201970s%20(WhyCirrus).pdf

 

 

 

Where the slots are located ahead of the ailerons, they provide strong resistance to stalling and may even leave the airplane incapable of spinning.

 

 

 

Quax says:

 

And he said exactly the same thing than Rall: it was no problem, because you easily could avoid it. The issue is no big deal for the sim. But it would be nice, if it was modelled. 

 

 

That was my experience in flying and owning a slat equipped aircraft.  The slats gave some fantastic low speed performance boost and their operation was not an issue to an experienced pilot.  In fact the only time it was even a cause for concern was my first landing when they banged out.  I thought something was wrong as the stick knocked and the noise.  Purely my inexperience with them.

[DD_bongodriver]

I don't know where you get the idea for "stall proofed".  The term is actually spin and stall resistant.  Yes, slats are stall and spin resistance devices

 

Yes, basically doing exactly the same thing as wing washout by ensuring the inboard section of the wing stalls before the outboard, I'm not the one who thinks they are 'stall proof' if you care to re-read my sentence.

 

That was my experience in flying and owning a slat equipped aircraft.

 

Just out of interest, what was this type?

[MiloMorai]

Does an a/c spin after a stall?

[DD_bongodriver]

Does an a/c spin after a stall?

Not always but it must stall to enter a spin

[Crump]

 

Me 109 G:

"- How often did the slats in the leading edge of the wing slam open without warning?

They were exteneded always suddenly but not unexpectedly. They did not operate in high speed but in low speed. One could make them go out and in by moving the stick back and forth. When turning one slat functioned ahead of the other one, but that did not affect the steering. In a battle situation one could pull a little more if the slats had come out. They had a positive effect of the slow speed handling characteristics of the Messerschmitt.

- Could the pilot control the leading edge slats?

No. The slats were extended when the speed decreased enough, you could feel when they were extended. "

- Kyösti Karhila, Finnish fighter ace. 32 victories. Source: Interview by Finnish Virtual Pilots Association.

 

Victory claims:

 

I would guess, that having the Bf109 exhibit some uncommanded roll when the slats deploy when there is side slip present would replicate the real airplane.

 

Unless there is a mechanical failure in the slat mechanism there will be no "uncommanded roll".  The slats work automatically and deploy as the wing section requires when the design coefficient of lift is reached.

 

In otherwords, what you claiming is an impossibility without a mechanical malfunction.

 

Kyösti Karhila anecdote illustrates this point.

 

 

Me 109 E/F/G: - The plane had these wing slats and you mentioned they pop open uneven?

"Two meter slots on fore wings.  The reason was to increase the lift during low speed take off and landing.  To reduce the length of runway you need.  In the air, if you make rough turns, just by gravity, the outer slot might get out.  You can correct it immediately by release of stick, you know? Only little bit, psssssssht, its in, then its gone.  You have to know that.  And if you know it, you prevent it."

- Major Gunther Rall. German fighter ace, NATO general, Commander of the German Air Force. 275 victories. Source: Lecture by general Rall.

 

What Rall is referring too is on occasion in hard maneuvering, one slat might bang out hard enough to malfunction. 

 

So modeling the BF-109 to have some uncommanded roll every time the slats deploy would be pure fantasy and nothing at representative of the flying characteristic of a slat equipped aircraft.

[Sternjaeger]

it is worth reminding that as long as the aircraft is above its stall speed, the uneven opening of the slats will not affect its stability. 

[DD_bongodriver]

What really doesn't make a shred of sense here is the claims that asymmetric slat deployment will not cause some uncomanded roll, think about it for a second, one wing has a slat deployed the other doesn't and we are not expecting an aerodynamic difference between the wings?

[Sternjaeger]

I think the "uncomanded roll" is proportional to the forces involved Bongo: as far as I know, a slat will only ensure a continuation of laminar airflow on the wing's upper surface. If you already have a laminar airflow, I guess all you might perceive is a judder on the roll axis? 

Edited November 18, 2013 by Sternjaeger

[Gort]

What really doesn't make a shred of sense here is the claims that asymmetric slat deployment will not cause some uncomanded roll, think about it for a second, one wing has a slat deployed the other doesn't and we are not expecting an aerodynamic difference between the wings?

Yes, you can stop asymmetric deployment by relaxing back pressure on the stick which reduces alpha which causes the slat to retract. Of course if you are pulling the aircraft over the top of a loop, or trying to keep your empennage from eating the lead of the bandit on your arse, it is a problem. He seems to be stating the obvious reaction for normal flying, not air combat.

 

It is something you learn to deal with, but it isn't optimum.

[NZTyphoon]

What really doesn't make a shred of sense here is the claims that asymmetric slat deployment will not cause some uncomanded roll, think about it for a second, one wing has a slat deployed the other doesn't and we are not expecting an aerodynamic difference between the wings?

AFAIK none of the British or American flight test reports on captured Fs & Gs mention any particular problem with the slats opening unevenly, although there is one report which states that at low speed the ailerons became noticeably lighter

 

http://www.wwiiaircraftperformance.org/me109/me-109g2-trop.html

 

The slats had a marginal effect on surface drag (page 2 of report):

 

http://www.wwiiaircraftperformance.org/me109/Hoerner-Me_109.pdf

[DD_bongodriver]

Yes, you can stop asymmetric deployment by relaxing back pressure on the stick which reduces alpha which causes the slat to retract. Of course if you are pulling the aircraft over the top of a loop, or trying to keep your empennage from eating the lead of the bandit on your arse, it is a problem. He seems to be stating the obvious reaction for normal flying, not air combat.

 

It is something you learn to deal with, but it isn't optimum.

Yes I know, Crump just told us that asymmetric slat deployment is impossible, despite the same pilot he has quoted explaining that it does happen.

 

Unless there is a mechanical failure in the slat mechanism there will be no "uncommanded roll".  The slats work automatically and deploy as the wing section requires when the design coefficient of lift is reached.

 

In otherwords, what you claiming is an impossibility without a mechanical malfunction.

 

Kyösti Karhila anecdote illustrates this point.

 

 

What Rall is referring too is on occasion in hard maneuvering, one slat might bang out hard enough to malfunction. 

 

So modeling the BF-109 to have some uncommanded roll every time the slats deploy would be pure fantasy and nothing at representative of the flying characteristic of a slat equipped aircraft.

The best part of this thread has been spent discussing how the slat deployment had to be 'managed' in accounts from pilots etc and now we are being told that there was nothing to manage.

 

AFAIK none of the British or American flight test reports on captured Fs & Gs mention any particular problem with the slats opening unevenly, although there is one report which states that at low speed the ailerons became noticeably lighter

 

http://www.wwiiaircraftperformance.org/me109/me-109g2-trop.html

 

The slats had a marginal effect on surface drag (page 2 of report):

 

http://www.wwiiaircraftperformance.org/me109/Hoerner-Me_109.pdf

Yes, and I have not suggested any problems, the term 'uncommanded roll' might sound worse than it is, in reality it was nothing more than a slight lateral jolt, any movement in roll that is not input by the pilot is still an uncommanded roll, might be enough to make a firing solution go wrong if you were turning to the limits.

[Dakpilot]

Okay I am confused, perhaps someone can enlighten me, with the slats on a 109, when they are extended do they increase lift? or are they solely their to maintain lamina flow and prevent the wing from stalling. I am not going to or want super technical answers but if they increase the theoretical wing area much like flaps, surely there is an increase in lift when they are deployed?

 

Cheers Dakpilot

[DD_bongodriver]

Not an increase in lift but an increase in the angle of attack before stall, for example if a wing stalls at 16deg AoA then a slat will increase that critical AoA and delay the stall.

Edited November 18, 2013 by DD_bongodriver

[Sternjaeger]

Okay I am confused, perhaps someone can enlighten me, with the slats on a 109, when they are extended do they increase lift? or are they solely their to maintain lamina flow and prevent the wing from stalling. I am not going to or want super technical answers but if they increase the theoretical wing area much like flaps, surely there is an increase in lift when they are deployed?

 

Cheers Dakpilot

 

slats are devices which, when deployed, are meant to enhance the laminar flow on the upper wing surface at high AOAs. But then again there is a theorist here that will tell you otherwise.. 

Edited November 18, 2013 by Sternjaeger

[JtD]

They also increase the maximum lift coefficient, but they don't immediately increase lift as they deploy.

[Dakpilot]

That I can understand, but if a slat extends and increases the wing area similar to the way a flap increases the wing area, surely as well improving critical AoA an element of increased lift must be generated, even at a smaller cost in drag?

 

Cheers Dakpilot