Could the slats be the landing problem on the 109

[thedab]

I reading this virtualpilots.fi: WW2History-MeAndTheGustav.html and had a bit about the slats causing alot
of problem on landing.so could it be the slats and not the undercarriage,which caused most of the landing accidents.

 

[pbehn]

Oh dear, I fear this will wake the beast in Adler.

 

[stona]

No. It was the geometry of the undercarriage (not the track which is so often quoted, compare it with a Spitfire for example) in combination with a lot of power and other minor factors, like a tail wheel which had no lock.
The complaint given in that link is that if the slats operated asymmetrically for some reason there would be a problem. There are lots of things on an aeroplane which can cause problems if they don't work properly. The Germans don't seem to have had problems with asymmetric slat operation under normal flying conditions. The slats were a passive system and there is no reason why they should malfunction if properly maintained.
Cheers
Steve

 

[Mike Williams]

This report may be of interest: http://www.wwiiaircraftperformance.org/me109/VB-109-10-E-42.pdf
The results section is translated here: http://www.wwiiaircraftperformance.org/me109/me109g.html

 

[stona]

And there you have it!

"The investigations have shown that the poor opening times of the slats on the 109 G are caused by difficulties in manufacturing; when the slats are perfectly stiff and installed correctly, flawless opening operation in climb and turning flight results."

If you don't build or maintain any system correctly it won' work properly. It seems credible that the Italians had problems with the operation of the slats. Maybe they were less familiar with, or less well trained than their German counterparts in the erection and maintenance of the type.
Oddly I can't find similar complaints about the slats on landing from German or Finnish pilots, they all seem to have appreciated them. Eric Brown did manage to get the slats to operate asymmetrically but describes the result as "unpleasant aileron snatching" rather than the catastrophe the Italians claim to have experienced. Even given the British tendency to understatement, "unpleasant" does not equate to disastrous or fatal.

Cheers

Steve

 

[GregP]

The observation I have is that the link mentions the same old things that Connie Edwards said when he was interviewed by the press ... that the flaps caused a large nose-down tendency. We had a former Luftwaffe pilot give a talk on the Bf 109 and he was asked about Connie's comments. His answer was eloquent.

He said that obviously Connie had not been taught to fly by the Luftwaffe! The flap wheel is right next to and the same size as the stabilizer trim wheel. They are separated by about 1 inch or so. In Luftwaffe training they were taught to move both wheels together and there was no trim change when that technique was used!

I also know some 5 - 6 pilots who have flown Bf 109s / Ha.1112s. All of them say the slats operate easily and cause no problem except for occasional symmetric deployment when you get to slat speed while the ball is not centered. The asymmetric deployment will not cause a flight control issue, but could cause an issue if you were actively shooting at a target because it caused momentary yaw until both slats were either in or out. That being said, the slats were both firmly out when in the landing pattern anywhere near touchdown speed, and retracted well before typical combat speed was reached. The Bf 109 was most comfortable in the 180 - 280 mph IAS range. Much faster and the Bf 109s stick forces became heavy, with the ailerons becoming heavy above above 310 mph and the elevators being almost immovable at higher speeds. The slats extend about 150 mph in normal flight, slightly higher if maneuvering.

So, according to German pilots, it was very good in typical combat situations and not at all difficult in landing configuration unless the pilot was inattentive combined with gusty crosswinds and a runway with a lot of traction, such as dirt. On a grass strip, it is said to be pleasant to takeoff and land. Unfortunately, the few Bf 109s flown today use pavement which exaggerates any bad tendencies. The aircraft might have a much better general modern reputation if they could be operated from grass, which was the wartime normal surface. If you watch the Bf 109s takeoff and landing runs on grass, such as at some UK airshows, you see nothing out of the ordinary. They do tend to look a bit snaky on pavement.

There is a lot of hogwash about the Bf 109 suffering some 30% or more takeoff and landing accidents, but little to no proof of that. If you look through German records (at least the ones I found some years back that were translated into English), I found nothing unusual about the takeoff / landing accident rates. It might be sobering to go look through the takeoff and landing accident rates in US pilot training. We were under no wartime stress there and were never under attack, but we had a lot of training accidents in initial fighter conversion training. It probably has more to do with transitioning from a trainer to a fighter with the quantum leap in power available than with the landing gear geometry. Shoving the power all the way in at low speed to effect a go-around has WAY different consequences in a P-40 or P-51 than it does in an AT-6. I'd bet the same can be said of transitioning from an Arado trainer to a Bf 109 or from a Chipmonk to a Spitfire.

 

[GrauGeist]

And there you have it!

"The investigations have shown that the poor opening times of the slats on the 109 G are caused by difficulties in manufacturing; when the slats are perfectly stiff and installed correctly, flawless opening operation in climb and turning flight results."...

Notice how this refers to the G, but doesn't take earlier models into consideration.

The difficulties in landing and takeoff were attributed to the maingear's wheel camber and strut pitch which required a pilot to be light and steady on the controls. The accounts I have read seem to show the Bf109 was easier to control on a grass surface rather than hardpan. The later models did have a tailwheel lock (located near the trim wheel and throttle quadrant) but if a pilot is inexperienced or not paying attention, this was not going to prevent a ground-loop or worse.

One of the things I remember most, was the stern warning to avoid a "three-pointer" when landing as it most often result in a wild and stressful situation.

But I haven't heard of any incidents where the slats caused trouble during takeoff or landing.

 

[kool kitty89]

I'd expect properly functioning slats helped a lot to improve take-off and landing characteristics due to totally eliminating tip-stall and resulting dangerous wing-dropping characteristics. (the F4U comes to mind there, P-39 too, not sure if the Fw 190 suffered from that at all, but the NACA 230xx airfoil series tended to lend to rather harsh stalls if careful wing design wasn't taken into account -beyond the typical margin of error for applying airfoil twist towards the outer wing; the F2A, F4F, and F6F used that airfoil too, but at much lower wing loadings)

 

[Shortround6]

Most important part of slats for take-off and especially for landing is that they maintained aileron effectiveness at low speeds. A malfunctioning slat could obviously affect handling on landing but slats/slots were used on a wide variety of aircraft to help landing issues making the claim that the 109 slats were responsible for handling problems or caused accidents (aside from the already mentioned malfunction/s) rather unbelievable. On many planes they could maintain aileron effectiveness even as the plane was stalling. .

 

[tomo pauk]

With Bf 109F, the design of the mechanism that controled the slats included the inter-connecting metal rod, that made sure both of the slats extend and retract in the same time.

 

[stona]

High accident rates usually have a lot more to with the training methods and systems than they do with any particular aircraft. If the Luftwaffe, or any other air force, noticed an unusually high rate of accidents on any one type that would be the first thing to look at.
Cheers
Steve

 

[stona]

With Bf 109F, the design of the mechanism that controled the slats included the inter-connecting metal rod, that made sure both of the slats extend and retract in the same time.

I can't find such a thing in the parts list

Cheers

Steve

 

[GregP]

Never have heard of interconnected slats on the Bf 109F and have NO idea where the pushrods might be routed, but have also rarely seen Tomo make a false claim. The wing is very crowded near the root.

I'll keep an open mind and try to find his reference independently if possible. If it is there, it SHOULD be in the pilot's manual and in the cutaway / parts list. Lack of finding it doesn't mean it isn't true. It might mean Tomo still might be right and I just can't find it. There is precious little useful design data around for the various Bf 109 systems. We have a CD with all the drawings for the Hispano. It definitely lacks any interconnect mechanism and is basically a Bf 109G-2 with a Merlin on the front.

 

[Milosh]

I can't find such a thing in the parts list

Cheers

Steve

Same here. The only thing I have come across is a design change, "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...".

 

[GrauGeist]

I wasn't aware that the Bf109's slats had an interconnecting rod on any of the variants. This is not to say that it didn't exist, it's just that I am not aware of that feature.

The slats were designed to deploy per that particular wing's load, which could vary greatly between port and starboard in a turning fight or under various conditions.

 

[stona]

I don't think Tomo has made a false claim, but I do think he is mistaken. The slats were not connected between wings. There is a connecting rod between the inboard and out board slat arms which would ensure that each slat came out straight and evenly.
Maybe this has caused confusion. I have seen this rod translated as "inter slat" connecting rod whereas "intra slat" would be better. I would call it the "inboard/outboard slat arm connector rod" because that is exactly what it is.

Cheers
Steve

 

[Airframes]

I agree. And if there had been an 'inter slat' connecting arm or rod, then sutely it would no be possible for assymetric deployment of the slats, a situation which has been mentioned when discussing any 'problems' surrounding the slats on this aircraft ?

 

[GrauGeist]

The Westland Lysander had a series of slats, inner and outer. If memory serves me right, the inner pair of slats were deployed when the flaps were extended via a connecting rod from the Flap's bellcrank.

I can't recall if the Storch did this too, although I know it had full length slats.

 

[Airframes]

I think they possibly did Dave.
In these two pics, the flaps are partly lowered, and it looks like the slats are deployed by a comparable degree.

 

[stona]

Aren't the slats fixed on the Storch? I don't think they were retractable.
Cheers
Steve