Me 109 ailerons and roll rate

[spicmart]

The roll rate of the 109 is said to not compare too well to other fighters of similar weight and dimensions such as the La-7 or Yak-3. Even the Spitfire with its much larger wing outrolls the 109 in many flight regimes.
The cause of this is apparently that the 109 wing (from the F-version onwards) has a relatively large tip so that the aileron does not extend to end of the wing.
I think it would have been possible to rectify this flaw by extending the aileron further as seen in the sketch.
What do you think?
Pardon the amateurish sketch.

 

[GregP]

The Bf 109 has decidedly manual controls. It also has a very narrow cockpit. Flight tests revealed that most pilots could not put more than about 45 pounds of side force on the stick at anywhere above about 280 mph or so, and that was not enough for full aileron deflection at higher speeds. The Bf 109 was very maneuverable at anywhere between 180 - 280 mph. Faster than 300 mph and the ailerons and elevator became hard to move. Above 350 mph or so, a Bf 109 was going fairly straight, even if you didn't want it to do so.

It had and has no rudder trim and, at anything 400 mph and above, it wasn't fighting, it was running to or from a fight. The mechanical advantage of the control stick was never really changed during the Bf 109 series, and it was never a good fighter when going fast, Bf 109 K-4 and onwards notwithstanding. Yes, the 109K could go fast, but it was not maneuverable when it was actually going fast. The Hispano Ha.1112 Buchon and the Avia S.199s with the Jumo engines were no better at speed. Still, the entire family of 109s were pretty hard to beat at 200 - 280 mph, and Allied bombers at any altitude were simply not fast enough to take the Bf 109 out of its best-handling speed envelope successfully.

As the vast majority of Allied pilots who were shot down by Bf 109s in WWII could attest, the Bf 109s limitations were not all that easy to overcome. Anyone who was shot down from ambush likely never saw the attacker and had no idea what speed the Bf 109 was going when it got them. The Bf 109 had a very steep angle of climb anywhere near best rate, and Bf 109 pilots tended to attack and stay in the vertical plane, while the Allied pilots tended to want to maneuver in the horizontal plane when fighting a Bf 109. Whichever one of them went the other way was giving up a bit, but it happened frequently.

The above makes the Bf 109 sound like it was a bad fighter aircraft. That is just NOT the case. The title of "Best fighter" generally swapped back and forth between the Spitfire and the Bf 109, depending upon timeframe, with the Fw 190 getting in there from August 1941, but the Bf 109 was never what you would call a bad fighter airplane. The pilots who flew it were well aware of its weak points and did very well minimizing them in combat.

If you were not aware of the 109s weaknesses as an opponent, you might not suspect them of existing. If you WERE aware of them, you had the task of getting veteran German pilots to a point where you could take advantage of them in combat. A great many Allied pilots failed to do just that, and a well-flown Bf 109G/K was as dangerous to a late-war Spitfire in 1945 as a Bf 109E/F was to an early-war Spitfire in 1940/1941, and vice versa.

When the two top fighters were on opposite sides, the outcome of individual fighter combat was more on the pilots and starting positions rather than on the airplanes. If you go to ww2aircraftperformance and look at the roll rate comparison chart, the Bf 109 is not represented. But it had a pretty competitive roll rate at 180 - 280 mph and tended to get much less competitive in roll and pitch as it got faster. Of course, all other fighters did, too. In fact, the Bf 109 was not a good roller, relative to other airplanes, much above 250 - 280 mph. But air combat is not cut and dried, and the Bf 109 more than held its own in almost any combat. If it couldn't out-turn you, it could generally out-climb you (not universal). That is, there was SOME area where it was quite good at any time, and the 109 pilots knew where those areas were and used them quite effectively.

So, all of the above does not detract from the fact that the Bf 109 has to be considered whenever one talks about the overall best fighter of WWII. If any two airplanes belong on that list of possible contenders, the Bf 109 and the Spitfire certainly do ... unless the list includes long range as a consideration. In that case, neither the Spitfire nor the Bf 109 would qualify. And, if neither of these airplanes qualify, I question the value of the list!

 

[Koopernic]

The roll rate of the 109 is said to not compare too well to other fighters of similar weight and dimensions such as the La-7 or Yak-3. Even the Spitfire with its much larger wing outrolls the 109 in many flight regimes.
The cause of this is apparently that the 109 wing (from the F-version onwards) has a relatively large tip so that the aileron does not extend to end of the wing.
I think it would have been possible to rectify this flaw by extending the aileron further as seen in the sketch.
What do you think?
Pardon the amateurish sketch.
View attachment 621589

The Me 109 series had an excellent bank rate and roll rate at low to medium speed. As speeds increased compressibility of the air or incipient shock waves would stiffen the ailerons and limit the pilots range of movement. This was due to a fairly thick wing. The Me 109F/G/K had freise ailerons to reduce aileron forces.

There is a British test that refers to aileron deflection in degrees versus pilots stick force in lbs. This stick force is lower for the Spitfire. However aileron deflection is not roll rate or bank rate. This is just a British test to evaluate one aspect of a machine. The Spitfire did not have a better roll rate because its wing would twist in the opposite direction (aileron reversal) and reduce the roll rate. Spitfire and Me 109 rolled at about the same rate at high speed even if 109 deflection was less and the ailerons were stiffer.

The P-51 due to its low compressibility in its laminar wing did not have this aileron stiffness, it also had 'internal balancing' where high pressure compressed air from the upper surface of the wing was channelled to a bellows to reduce forces. The P-51 also had a very stiff wing and so no aileron reversal.

The Fw 190 had a stiff wing and it was hardly any thicker than the Spitfires at the tip.

The solution for the Me 109 was 'spring servo tabs' in which small tabs are deflected by the pilots control column to push the aileron. They are finicky to set up and can easily create too low a force. Spring servo tabs were often refered to as fletner tabs in German. Some Me 109G6 built by WMF may have had them and so maybe some Me 109K4 but its a big debate though there are drawings.

The real solution was to build the Me 209-II, Me 309 or Fw 190 instead.

The next move was hydraulic assistance, which I know was used on the Do 335.

Increasing aileron area help roll rate at low speed but actually reduces it at high speed due to reduced deflection.

Note also the appearance of young German fighter pilots in short sleeves or shirtless in Africa, France or a European summer. These lean young men have surprisingly huge biceps and that is also a solution. Air to Air combat was physical and you better be fit and strong.

 

[Juha3]

In fact according to DVL wing twist tests on Bf 109F-2, which also gave roll rate for the plane, 109F-2 rolled worse than the standard wing Spitfire in the figure 47 in the NACA 868 report at all speeds, parameters used: around 3km height and with max stick force the test pilot could produce (44lb) because of the narrowness of the cockpit. The difference was marked (over 10deg/sec) at IAS speeds under 260mph, small (under 5deg/sec) from 275 to 300 mph IAS. It maxed at Spit's max roll rate speed 200mph IAS being 33deg/sec., and was smallest at 109's max roll rate speed 280mph IAS being 3deg/sec. At 390mph IAS normal wing Spit rolled 14deg/sec faster than the F-2 used by DVL. Of course it is not optimal to compare data for a Bf 109 F-2 taken from a DVL study and data for Spit V taken from a NACA study, but that is the best I can do now.

One must remember that 109G had a bit stiffer wing than 109F, wing skin at roots was a bit thicker and one must also remember that planes were individuals and at least Frise type ailerons were sensitive to rigging error.

A Finnish specialist and author Jukka Rautio writes that the max roll rate for Bf 109 F-2 was about 80 deg/sec at 267mph IAS at 3000 m (9,843 ft) with 44 kp stick force, max the test pilot managed because of the narrowness of the cockpit. Source: SIhL 3/2005 "Mäntämoottorihävittäjän suorituskyky". It is based on the DVL test report.

One other Finn gives the peak roll rate of 85 deg/s at 500 km/h TAS (267mph IAS at 9,843 ft) for the 109 G.

Also the British test pilot Trevor Sidney "Wimpy" Wade, e.g. in late 1943 he was made the Officer Commanding at the Air Fighting Development Unit (AFDU), disagree with the claim that that Bf 109 G rolled as well as later Spits. See the attachment

 

[GregP]

The chart you showed is nice, but doesn't say the altitude where it was generated or give stick force. When I said the Bf 109 was missing, I meant this figure:

http://www.wwiiaircraftperformance.org/naca868-rollchart.jpg

This one, too, is a nice chart, but there isn't a lot of information as the chart is only good at 10,000 feet altitude, and the Bf 109 is conspicuously absent.

 

[pbehn]

It is all very well drawing a line on a diagram of a wing, how does your new wing hinge the aileron? As with the Spitfire the curved end part of the wing is just bolted/fixed on, how does the aileron in the changed type work?

 

[nuuumannn]

A part of the problem with the Bf 109 and its roll rate was the deflection of the control stick between the pilot's legs in the cockpit. The Bf 109 had a narrow cockpit and moving the stick about its full arc of movement was very difficult because of the pilots' legs. If your pilot was a bit thicker in the thighs, that restricted the control column's movement even more. I read that Buchon display pilots often encounter this issue when putting their aircraft through manoeuvres when following other WW2 types.

 

[nuuumannn]

Great post on the Bf 109's advantages and disadvantages, Greg; the one thing about the Emil when encountered by the RAF during the Summer of 1940 was that its normal mode of attack was to use its superior altitude from which to dive upon enemy aircraft, then escape and return to height, which made it very hard to counter the type effectively, but it wasn't the best dogfighter.

Both the Spitfire and Hurricane were better scrappers in a close-in turning fight and combat at this time more often than not evolved into this kind of engagement, which also meant that the fight got lower and slower, an arena where both RAF types proved superior to the German fighter. As one RAF pilot once said when it was pointed out to him that the Bf 109 had better altitude performance than RAF types, "well, they have to come down here to get us".

As the battle hardened and German tactics evolved, Park, in particular, knew that the Germans were sending fighters over in mass formations to lure the RAF into a fight, but he was cannier than that and held back against the fighters until the bombers appeared. It didn't always work and the Bf 109's superiority came to the fore when the British fighters attempted to chase it in the vertical plane.

 

[Juha3]

Hello Greg
I answered to Koopernic and Wade's graph is one of many he produced, IIRC used during a lecture IIRC. It is not a gospel but an educated opinion. NACA did not have a Bf 109 test data, so could not put it into the graph (that in their report Nr. 868).

109 was a great fighter but it had its weaknesses but also its strengths, its forte was in vertical fight which in any case was usually the more effective mode than horizontal.

 

[Koopernic]

Hello Greg
I answered to Koopernic and Wade's graph is one of many he produced, IIRC used during a lecture IIRC. It is not a gospel but an educated opinion. NACA did not have a Bf 109 test data, so could not put it into the graph (that in their report Nr. 868).

109 was a great fighter but it had its weaknesses but also its strengths, its forte was in vertical fight which in any case was usually the more effective mode than horizontal.

Max roll rate of Bf 109F-2, at 30kg/66lbs stick force 3000m TAS from DVL report (DVL more or less German equivalent of NACA)

200 kph = 45 deg/sec (0.8rad)
300 kph = 68 deg/sec (1.2rad)
400 kph = 83 deg/sec (1.45rad)
480 kph = 20kg/44lbs limit
500 kph = 88 deg/sec (1.55rad)
600 kph = 91 deg/sec (1.6rad) - peak value
700 kph = 56 deg/sec (0.98rad)
800 kph = 23 deg/sec (0.4rad)

In IAS

600km/h TAS = around 510km/h IAS = 91°
700km/h TAS = around 595km/h IAS = 56°
800km/h TAS = around 680km/h IAS = 23°

So if we have a look at Me 109 roll rate at 700kmh (IAS 595kmh or 368mph) it is 56 degrees/second it is the same as a normal wing spitfire at the same speed albeit at 30kg (66kg) stick force instead of 50lbs.

Attached is the NACA report which has roll rates of various allied and axis fighters (albeit not the 109, which we have to use the DVL report)

The Me 109 was far from immobile in the roll axis. Why would the DVL produce a report based on 30kg stick force if a German pilot couldn't produce it?

Maybe don't arm wrestle with a Luftwaffe 109 pilot is one thing to be taken from this.

The Me 262 and Me 109K4 both had provision for servo tabs. The reason they didn't appear I suspect it that introducing and manufacturing such as device in post october 1944 was simply too hard.

The Me 262 had a neat trick: the joystick could telescope to provide more leverage to the pilot. I suspect the same solution could have been provided to the Me 109 if it became necessary. At high speed less deflection is needed.

 

[Juha3]

Hello Koopernic
see pp. 12 & 24 in the DVL report, notice the flown not calculated parts of the graphs.

Juha

 

[spicmart]

Sorry, but was does DVL stand for?

 

[GregP]

Hi nuuumannn,

Thanks for the shout out. I am a Bf 109 fan (actually, I like almost all airplanes), but it did have some idiosyncrasies, like any other airplane.

The Flying Tigers (or AVG, more properly) used the strengths of the P-40 to good effect when attacking the Japanese Ki-43s Hayabusas that they typically misidentified as "Zeros." Almost all fighters had some form of "preferred" attack methodology in an ideal world and the Bf 109 was no different. So, if you'll excuse a generality, almost every fighter had some weaknesses and some strengths. Very few if any were simply bad airplanes or else they would never have been selected for production in the first place.

The Hurricane was generally not as well thought of as the Spitfire, but its main disadvantage was that it was slow. In point of fact, as we all know, it actually shot down more enemy aircraft than the Spitfire in the Battle of Britain.

So, the Bf 109 is in some very good company when employing its strengths for attack. While its weaknesses were not critical, they were likely annoying, particularly the lack of rudder trim, but could be avoided (aside from the trim) using proper tactics. The Bf 109 airframe enjoyed huge success in WWII, weaknesses notwithstanding. As I said, altogether a VERY effective fighter aircraft, and it had the huge advantage of being quick to produce in man-hours.

A Spitfire required something like 15,200 man-hours to build and Messerschmitt could pop out a Bf 109 in about 4,000 man-hours. If the Brits had had the opportunity to swap Spitfires for Bf 109s, they might have done so (I'm not saying they WOULD have, only suggesting that it might have been considered) if only due to the manufacturing advantages. Sounds like sacrilege, I know, but an advantage of 11,200 man hours is hard to ignore. Basically, the Germans could field four Bf 109s in the time it too the UK to make one Spitfire. The Spitfire was a great airplane, but was it four times better than a Bf 109? No way. I'm sure this will cause a stir of argument, but that is not my intent. I'm only pointing out that, flawed though the Bf 109 may have been, it nevertheless swapped the title of best fighter back and forth with the Spitfire for years and, at the same time, could be produced in one quarter of the time as the Spitfire while simultaneously acquitting itself very well indeed in aerial warfare. What's not to like?



Nice post, Koopernic!

I am a bit confused, the first set of numbers appears to be TAS from the sentence above it and the second set of numbers appears to be TAS from the data, but you have the phrase "In IAS" between the two n umbers sets. Can you elaborate a small bit? The chart I posted was in IAS.

Cheers, guys.

 

[Milosh]

That 4000 hours is for late war production 109s and Spitfire production times came down.

 

[Greyman]

Ugly sketch I made for my own curiosity some time ago. Not the most presentable but it gives an idea.

Yellow - fabric aileron Spitfire
Dark purple - RAE tested 109E (points are given, line is my uneducated estimate)
Light purple - DVL 109F

 

[GregP]

Not too sure how to get from EAS to IAS in a Bf 109, but your chart looks pretty decent for 3000 m and 600 kph TAS data point. Even a Typhoon was better at 400 mph!

 

[Koopernic]

Hi nuuumannn,

Thanks for the shout out. I am a Bf 109 fan (actually, I like almost all airplanes), but it did have some idiosyncrasies, like any other airplane.

The Flying Tigers (or AVG, more properly) used the strengths of the P-40 to good effect when attacking the Japanese Ki-43s Hayabusas that they typically misidentified as "Zeros." Almost all fighters had some form of "preferred" attack methodology in an ideal world and the Bf 109 was no different. So, if you'll excuse a generality, almost every fighter had some weaknesses and some strengths. Very few if any were simply bad airplanes or else they would never have been selected for production in the first place.

The Hurricane was generally not as well thought of as the Spitfire, but its main disadvantage was that it was slow. In point of fact, as we all know, it actually shot down more enemy aircraft than the Spitfire in the Battle of Britain.

So, the Bf 109 is in some very good company when employing its strengths for attack. While its weaknesses were not critical, they were likely annoying, particularly the lack of rudder trim, but could be avoided (aside from the trim) using proper tactics. The Bf 109 airframe enjoyed huge success in WWII, weaknesses notwithstanding. As I said, altogether a VERY effective fighter aircraft, and it had the huge advantage of being quick to produce in man-hours.

A Spitfire required something like 15,200 man-hours to build and Messerschmitt could pop out a Bf 109 in about 4,000 man-hours. If the Brits had had the opportunity to swap Spitfires for Bf 109s, they might have done so (I'm not saying they WOULD have, only suggesting that it might have been considered) if only due to the manufacturing advantages. Sounds like sacrilege, I know, but an advantage of 11,200 man hours is hard to ignore. Basically, the Germans could field four Bf 109s in the time it too the UK to make one Spitfire. The Spitfire was a great airplane, but was it four times better than a Bf 109? No way. I'm sure this will cause a stir of argument, but that is not my intent. I'm only pointing out that, flawed though the Bf 109 may have been, it nevertheless swapped the title of best fighter back and forth with the Spitfire for years and, at the same time, could be produced in one quarter of the time as the Spitfire while simultaneously acquitting itself very well indeed in aerial warfare. What's not to like?



Nice post, Koopernic!

I am a bit confused, the first set of numbers appears to be TAS from the sentence above it and the second set of numbers appears to be TAS from the data, but you have the phrase "In IAS" between the two n umbers sets. Can you elaborate a small bit? The chart I posted was in IAS.

Cheers, guys.

To convert you need to know the relative density of the air at the altitude in question. IAS = TAS/Rd or TAS = IAS*Rd. Where Rd is relative density. You could substitute atmospheres atmospheres of pressure which is about same as re relative density of the air.

Quick formula:
TAS = IAS * [1 + (Altitude/1000 * .02)]
Altitude in feet
Or, TAS = IAS + 2% per 1000' altitude.

correction factor is more like 1.5% if Mach effects considered.


Dont forget DVL is at 30kg/66lbs stick force and NACA 868 at 50lbs so 109F2 might be only 75% if at 50lbs. It's still reasonale. Not sure if roll rate falls of linearly with stick force.

 

[GregP]

Funny, I always went from IAS to CAS to account for instrument errors, then to EAS to correct for compressibility and, finally, to TAS to correct for windspeed around the aircraft.

But, your formula is a good enough approximation for civil aviation and likely for most WWII situations.

Thank sand cheers.

Edit: How about: Or, TAS = IAS + (2% per 1000' altitude) * IAS.

 

[Juha3]

Sorry, but was does DVL stand for?

DVL = Deutsche Versuchsanstalt für Luftfahrt E. V.

 

[Juha3]

...
The Me 109 was far from immobile in the roll axis. Why would the DVL produce a report based on 30kg stick force if a German pilot couldn't produce it?
....

DVL was a scientific research institute, and the report is a scientific paper. One can see that also from the list attached to it showing the people who had read/looked at it. 8 persons, 5 first names are typed: Herr Dr. Conradis, Herr Prof. Tank, Herr Dr. Pabst, Herr Mittelhuber and Herr Multhopp, the other 3 names are listed in handwriting, the first one seems to be Herr Wehrse, the other 2 are bit more difficult to decrypt.

And IMHO the main point to us is what the test pilot(s) achieved with this particular 109 F-2, not what the author calculated that what was theoretically possible, if the pilot could achieve full aileron deflection at high speeds.