Auto leading edge slats of the 109

[Quax]

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.

[DB605]

"Pilots tried to avoid them, because it could be very nasty in a close dogfight, especially on the deck." This is only true till E model. From F to onwards, they were re-designed and did not cause any kind of snap when they come out. Pilot would only feel slight notching on stick.

[Quax]

My friend flew the F and G (no E). I will ask him about the experience in the G. But I don´t think the new suspension of the G solved the problem of the unsynchronized deployment.

[DB605]

http://www.virtualpilots.fi/feature/articles/109myths/

 

Scroll down until "Wing leading edge slats - good or bad?". You will find lots of pilots comments about it there.

 

" 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.

Edited November 16, 2013 by DB605

[Quax]

It looks like you didn´t understand me. I didn´t comment on "good or bad". I just said it would be nice, if it was modelled correctly. And this means, they are not coming out synchronized like in previous IL2 titles.

 

 

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.

 

There were surely pilots who didnt like them, and others liked them. But both wouldn´t have flown the speed, where they would come out and go at will. 

Edited November 16, 2013 by Quax

[Talisman]

Good post Quax.  This is just the sort of detail that I am hoping the BoS developers will pay attention to for all aircraft types.

 

In this case, Rall informs us that the pilot of the 109 has to 'manage' the characteristics of the wing slats.  Such pilot management includes trying not to make 'rough' turns and 'releasing' the stick to correct if need be.

 

I have not flown any flight simulator that depicts this level of detail, so as a virtual Bf 109 pilot I have not needed to 'manage' the characteristics of the wing slats.  I sincerely hope BoS will include this level of detail, as it will mean we can be nearer a better simulation of being a pilot and can get better job satisfaction in terms of the pilots tasks in the air for each aircraft type. 

 

The wing slats are one of the things that make the 109 the character it is, but up to now I have not found a flight sim that gives us the true character of the Bf 109 (or many other aircraft types too).

 

I am hoping that the BoS developers can get us nearer to the true character of some of the WWII war-birds.

 

Happy landings,

 

Talisman 

[DB605]

It looks like you didn´t understand me. I didn´t comment on "good or bad". I just said it would be nice, if it was modelled correctly. And this means, they are not coming out synchronized like in previous IL2 titles.

 

There were surely pilots who didnt like them, and others liked them. But both wouldn´t have flown the speed, where they would come out and go at will. 

 

You said "Pilots tried to avoid them, because it could be very nasty in a close dogfight, especially on the deck.". I meant that was only true with E model, with later models they did not have to avoid slats opening because it did not affect steering anymore. However it was good sign to pilot that stall was near and they could avoid it by releasing stick a little bit. But i agree about modelling them correctly in game would be very nice indeed.

[Quax]

You are right, I should have said "some pilots"          But the E and F had the same suspension. 

 

"The Me (Bf ) 109 "E" through "F" used the swing arm parallelogram mechanism to agitate the slats. From the "G" onwards the Me 109's used the roller-track mechanism to guide the slats in and out.  It all follows a patent bought by Messerschmitt from DeHavilland just prior to the war. The slats are driven out by means of low air-pressure if the AOA gets higher ( slow flight ) and retract by means of air-pressure when accelerating..."

Edited November 16, 2013 by Quax

[Gort]

Well, I've got a little over 1000 hours in the TA-4J, much of it as an instructor, and it had aerodynamic leading edge slats on swept wings. Not sure if the wing sweep made a difference compared to the Bf-109, but there were some handling quirks defined by the slats.

 

The slats required careful adjustment by someone who was an "expert" in their operation to avoid asymmetric deployment. We would check them during pre-flight for binding. Even so, they would regularly deploy asymmetrically under G. 

 

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. You'd start a loop, and end up doing a clover leaf. The problem occurred only when the slats deployed from retracted. Once they were out, the aircraft handled normally.  

 

I once got one stuck after fooling around with inverted flight. Slamming four or five positive G's got them both out, followed by normal retraction after easing the G. They would hang in the fully extended position on the ground, due to their own weight. During a cat shot, the inertia would slam them into the retracted position, so as you rotated off of the end of the ship, you'd get strong buffet until they deployed, hopefully symmetrically. They were also an issue during formation aerobatics. If the flight lead was rough, then he was setting the formation up for all sorts of issues with asymmetric deployment, usually a quick roll off as they deployed sequentially. The last thing you wanted to do was ease the pull if you got an asymmetric deployment, just counter with rudder and aileron and keep the pull coming.

 

Perhaps most telling is that the Blue Angels bolted their slats to the fully retracted position and just accepted the increased approach speeds and reduced turn rates. The reasons for doing so should be obvious. 

[Crump]

 

Perhaps most telling is that the Blue Angels bolted their slats to the fully retracted position

 

 

They used Adversary Skyhawks which is a variant of the A-4E specifically for the Aggressor squadrons.   It was a stripped down variant and bolting the LE slats had nothing to do with formation flying.  It had to do with stripping the plane down for fuel efficiency so it could reach the maneuver box 3 times a day to train fighter pilots.  The slats are identical to a normal Skyhawk, they were just bolted shut and the internal mechanism removed for weight.

 

It had a drag chute installed to reduce the landing roll. 

 

Here a good picture of a Skyhawk aerobatic team flying in close formation with normal slats.  You can see the slats are open.

 

 

Here is the LE slats on my first aircraft.  I filmed this for guys in another game wanting to know how they operate.  There is some notching of the stick if pulled hard but it is not an issue.  When they come out, the low speed maneuvering benefits are extremely noticeable.

 

http://www.youtube.com/watch?v=cTKquNQq9TU&feature=youtu.be

Here is the modification right out of the manual.  Notice you install shims to support the slat in the absence of the rails and internal structure.

 

[Crump]

 

 the weight savings would be inconsequential

 

 

The slats are not the only thing removed.  It is a fact they used the Aggressor variant of the A4E.    Nothing to do with "asymmetrical deployment".

 

The Navy had quite a few of the aircraft surplus when the F5 replaced them in a aggressor squadrons at the Top Gun.

 

I'll bet the New Zealand acro team didn't perform high G negative maneuvers

 

Would not be much of a acro team if they did not.

Negative G maneuvers were never an issue due to the slats.  It is more of engine fuel and oil feel issue.  The aggressor A4E had a Zero G fuel set up and could handle Negative G maneuvers, a normal A4E does not.

BTW, that picture at the top of a loop is negative G......

[DD_bongodriver]

BTW, that picture at the top of a loop is negative G......

 

How is that possible? neg g would push them closed

[AndyJWest]

How is that possible? neg g would push them closed

 

And the elevators seem to be in a position to be pulling positive G too...

[Crump]

And the elevators seem to be in a position to be pulling positive G too...

 

 

A loop in formation will experience Negative G.  Any aerobatic pilot should know that.

http://www.youtube.com/watch?v=38G9ZIBZzkk

That video has footage of the RNAF Skyhawks doing loops in formation......

[DD_bongodriver]

A loop in formation will experience Negative G.  Any aerobatic pilot should know that.

 

http://www.youtube.com/watch?v=38G9ZIBZzkk

 

That video has footage of the RNAF Skyhawks doing loops in formation......

And what does that have to do with the elevators in the picture clearly showing deflection that would result in +'ve g? ,what evidence do we have that your picture is taken at a moment of -'ve g? when under -'ve g the angle of attack is also likely to be -'ve and the slats are likely to be forced into retract particularly when the aircraft is inverted.....why do they open in your opinion?

[Crump]

 

How is that possible? neg g would push them closed

 

 

Bongo,

 

The slats open when a coefficient of lift is reached.  The aircraft in order to provide the centripetal force required to maintain the loop is still at the angle of attack required to maintain a high coefficient of lift in a maximum maneuver. 

 

Could a loop be flow such that the slats close?  Sure....but it would not be a steady state condition.

 

This is a steady state loop and accelerations experienced by the aircraft.  Notice the acceleration vector is always "up" to the wing....

 

 

Edited November 16, 2013 by Crump

[DD_bongodriver]

You just explained how a formation loop is going to experience negative g which is true, then you go and explain your theory using a non formation loop where g is positive throughout.

[Crump]

Don't confuse the negative G experienced in a bunt with the Negative G experienced in a loop, bongo.

[DD_bongodriver]

who is talking about 'bunts'?

[Crump]

 

You just explained how a formation loop is going to experience negative g which is true, then you go and explain your theory using a non formation loop where g is positive throughout.          

 

Anything not attached to the aircraft but only contained by the structure such as oil, pilot, dirt, pencils, fuel, will all now have the normal acceleration of gravity vector added to it.  Look at the diagram and try to understand it, please.

Edited November 16, 2013 by Rama
Removed provocative comment

[DD_bongodriver]

Can you just answer my question? or are you that insecure you need to start the insults immediately?

[Crump]

 

Can you just answer my question? or are you that insecure you need to start the insults immediately?          

 

Insults have not started immediately and let's not kid ourselves, you did not post to add anything except to try and prove me wrong in something.  It gets old, bong.

 

I really do have a hard time understanding why I am having to explain this to such an experienced aerobatic pilot as you claimed in the last tiresome thread.

 

Look at the acceleration of gravity vector. 

 

As the aircraft moves to the top of the loop the normal acceleration of gravity no longer opposes the weight but adds to it. 

 

 

Our lift production remains constant, the slats stay open, and pilot, pencils, oil, and fuel all move toward the center of the loop as the centripetal force increases.  Since our pencil is now falling "up" to our frame of reference, we are in Negative G's!!

Edited November 16, 2013 by Crump

[DD_bongodriver]

the picture you have used is showing 3 different loops with positive and constant g throughout, even though your diagram shows the g vector in the wrong direction I understand it's theory........can you please show me an example that explains my query using negative g?

[Gort]

I thunk I have Crump pegged here, and as such, it is a waste of time to argue with him.

 

For the rest of you, the slats are a combination of aerodynamic and inertial forces. They will, on the A4 at least, extend under negative flight, especially at high G, very dependant on the rate of onset.

 

A formation loop as taught and flown by the USN and the Blues generally targets zero to some positive G across the top.

 

The A4’s flown by the Blue Angels also had physical springs that put about a fifteen pound force on the stick in the plus X direction.

[Crump]

 

the picture you have used is showing 3 different loops with positive and constant g throughout

 

Look at the arrows for radial acceleration.  Lift has to meet the radial acceleration and approximates it.

 

The Ghz or normal acceleration is what we feel as occupants of the aircraft.

Edited November 16, 2013 by Rama

[DD_bongodriver]

it appears so yes, I know from practical experience that when I pull positive g force everything is being pushed through the floor of the aircraft i.e. the acceleration arrow in your diagram appears to be 180 deg out.

[JtD]

Just for a change, can you try and not get the topic locked? Would be a shame if Crump succeeded in adding another one to his long list of successful topic locks.

 

LE slats are a reoccurring topic of interest to many, and Victory205 has added some nice first hand experience here.

[Crump]

Bolting slats for what? Fuel efficiency to make it to a working area? That makes no sense whatsoever- the weight savings would be inconsequential. Hell, it probably didn't save anything.

 

I've got many hours fighting adversary A4F's  and A4M's, some of which were de-humped to save weight. These were from TOPGUN, VF126, VF43, VF45, and VFC12-  all had the slats functioning normally. You'd lose too much in terms of sustained and instantaneous turn rate. 

 

I've never heard of a US Navy A4, other than the Blue Angels' A4F's, having the slats bolted. If they were, I'd love to fight one. 

 

I'll bet the New Zealand acro team didn't perform high G negative maneuvers, like the opposing cuban eights the Blue Angel solos' performed. I also believe that the slats were normal on the Blue Angels TA-4J that was used for PR demos and flew in the slot from time to time.

 

 

You understand that page is the maintenance manual for the A4 Aggressor skyhawks???  That also does not mean that every A4 Skyhawk found in the aggressor squadrons is a special modification for that duty.  They typically take on a wide variety of aircraft and fly just about anything available to them.  Even USAF T-26 Talons.....so I am not surprised if you saw normal A4's.

 

Dehumping the avionics bay is not the only modification either, Victory, it is all in the manual. 

 

Once again, not flying High Negative G maneuvers has to do with the fuel and oil system on the aircraft and not the slats.

Edited November 16, 2013 by Crump

[Sternjaeger]

excuse me gents, could we go back to Bf109 slats? Last time I checked there were no Skyhawks over Stalingrad.

 

Thank you.

[Crump]

it appears so yes, I know from practical experience that when I pull positive g force everything is being pushed through the floor of the aircraft i.e. the acceleration arrow in your diagram appears to be 180 deg out.

 

 

Rama edited out the part about the diagram being from the USN FTM.  So you think they are wrong?

[DD_bongodriver]

Rama edited out the part about the diagram being from the USN FTM.  So you think they are wrong?

it appears so yes, I know from practical experience that when I pull positive g force everything is being pushed through the floor of the aircraft i.e. the acceleration arrow in your diagram appears to be 180 deg out

[Crump]

 

 I know from practical experience that when I pull positive g force everything is being pushed through the floor of the aircraft

 

 

That is correct!  However the USN FTM is not wrong. The diagram is from the frame of reference of the aircraft.

 

Are you attached to the aircraft?  No, therefore your body wants to go in a different direction unless something provides the centripetal force required to keep you in the turn.

 

What is stopping you from flying out of the circle and providing that centripetal force?  The floor....so you feel the floor pushing back.

 

When the aircraft gets to the top, the center seeking force now has the additional vector from normal gravity and the "push against the floor" is reduced accordingly.  The airplane is still in the same circle and the wing is still providing the centripetal force required to remain in that circle.

Edited November 16, 2013 by Crump

[Rama]

I don't remember editing anything but rude or off-topic comments.

But if you ask, the diagram is only on the forces affecting the movement of the plane and can't be used directly to determine the G-forces applying on the pilot. You confuse the acceleration of the plane mouvement, and the induced forces on the "non attached objects" inside the plane.

On these object, the gravity will sum with theses induced centrifugal forces.

 

If you place an unfixed object on a carousel and make the carousel turn, the object will be accelerated toward the oposite of the center of the carousel, and not toward the center of it.

You can check it, it's an easy experiment.

[Crump]

 

But if you ask, the diagram is only on the forces affecting the movement of the plane and can't be used directly to determine the G-forces applying on the pilot.

 

Think about this statement.

[Rama]

I actually thought before writing it... and read what's after, it make you understand.

BTW... you're not the only one with en engineering degree and a pilot licence there.

[Crump]

Here is the USN FTM Chapter on maneuvering performance. 

 

c61.pdf

 

 

The radial acceleration and lift production have a defined relationship in a turn.  Radial acceleration approximates lift but I did not say it equals lift.

 

In otherwords, what the radial accelerating is doing, the lift is doing too.

 

Tell me something Rama, how much lift does the wing have to generate if it is flying at a constant altitude upside down?

 

If you place an unfixed object on a carousel and make the carousel turn, the object will be accelerated toward the oposite of the center of the carousel, and not toward the center of it.

 

 

Sure in the absence of centripetal force...

 

 

Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path.

 

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

 

Hey look, I am not going to argue with you because you are just looking for an excuse to ban me. 

[Rama]

First do the experience with the Carousel, and then maybe (or not) I'll answer your easy question, which BTW, has nothing to do with what happens in a loop where a pilote pulls a constant 4g.

You may also find that if the lift forces (who don't depends only on acceleration), apply on the plane airframe to define its trajectory, 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).

All this is standard mechanics and dynamics, it's not even specific to aeronautics.

 

Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path.

Yes, of course, and that's exactly what apply to define the mouvement of the plane itself, to define it's trajectory, but NOT to the non-attached objects inside the plane.

 

Even for the carroussel, when you start to move it, in order to compute the trajectory of an object attached to the frame of the carrousel, you will use an acceleration directed toward the center of the carroussel (any object moving in a circular trajectory has this trajectory defined by an acceleration directed toward the center of the circle)... and the non-attached object above will be still expulsed toward the outside.

... again, this is basic mechanic.

 

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.

 

Hey look, I am not going to argue with you because you are just looking for an excuse to ban me.

That wasn't my intention...

... but actually, I could give you some vacancies for this very sentence, since it clearly states that my moderation is skewed, and is a direct breach of rule #6

Let's say I have not read it...

[Gort]

excuse me gents, could we go back to Bf109 slats? Last time I checked there were no Skyhawks over Stalingrad.

 

Thank you.

 

There would have been had the Russians gotten frisky in 1969…

[Sternjaeger]

That wasn't my intention...

... but actually, I could give you some vacancies for this very sentence, since it clearly states that my moderation is skewed, and is a direct breach of rule #6

Let's say I have not read it...

 

*sits comfortably, grabs some popcorn and awaits next move*

There would have been had the Russians gotten frisky in 1969…

 

LOL now that's a helluva "what if" scenario! 

Edited November 16, 2013 by Sternjaeger

[Sternjaeger]

I couldn't have said it better.