WWII Rate of Turns

[swampyankee]

I was really scratching my head with that one! If I read that correct if equal to or below that line, you could hold a level turn?

Also, regarding true airspeed and corrected airspeed, which is accurate? I assume corrected...

When you say propeller advance ratio, you mean pitch right? Regardless, normally I would be inclined to say "engine power only affects sustained agility", but with propellers, the slipstream does augment lift itself, so that is actually important.

Mach effects don't just affect the wing and tail surfaces, but the propeller too, the same for exhaust thrust (ram compression).

Roll rate is highly important actually...

Advance ratio is airspeed (ft or meters per second) divided by (diameter (ft pr meters) times rate of rotation(rev/sec); pitch is chosen from advance ratio. For more about prop parameters, see 11.7 Performance of Propellers

 

[Barrett]

Ref. the 109 v. the Hurricane. The Hurrybox certainly could out-turn the 109 (we tend to say THE Hurricane and THE 109 when of course there were model variations) but in any case the RAFish chap probably was purely defensive.

However, FWIW: the 109 pilots I knew said that an Emil/etc could stay with a Spit at typical altitudes/airspeeds if the 109 driver was willing to fight in buffet with the lats extended. Same applied to many Soviet fighters. I'm writing a detailed Topgun book with the school's founder, and he describes how (in specific circumstances) the F-4 could turn with other "fighterjets" if the Phantom pilot had trained to fight in deep buffet. McDonnell Douglas was appalled at first, then really impressed. Of course, the Phantom's main advantage was its vertical performance to negate a tighter-turning adversary.

 

[pbehn]

However, FWIW: the 109 pilots I knew said that an Emil/etc could stay with a Spit at typical altitudes/airspeeds if the 109 driver was willing to fight in buffet with the lats extended..

From what I read, with the top Bf 109 pilots the "fun" didn't start until the slats extended. It was then just a question of skill and nerve.

 

[Glider]

From what I read, with the top Bf 109 pilots the "fun" didn't start until the slats extended. It was then just a question of skill and nerve.

Unfortunately if you do that you will have lost all your energy and speed and would be a sitting duck if there are other enemy aircraft nearby

 

[pbehn]

Unfortunately if you do that you will have lost all your energy and speed and would be a sitting duck if there are other enemy aircraft nearby

It is way above my pay grade on aerodynamics but I was under the impression that the deployment was dependent on the wings angle of attack, in a combat situation no more or less dangerous than for an opposing Spitfire for example as the speeds were about the same.

 

[Deleted member 68059]

This is my favorite graph on this subject.
http://www.spitfireperformance.com/spit109turn.gif

Please note the variations in turning times, speeds, diameters. also note the line marked "angle of straight climb" as it pretty well defines the ability to turn without losing altitude. It pretty much explains why turning fights rapidly descended in altitude.

Not to be a party pooper - but I do not like websites that post odd pages of reports. Because you miss important things - I have photographed that entire original report, and I can tell you that all those graphs were constructed by a theoretical formula used to try to predict the turning performance at various speeds/altitudes because its basically impossible to actually conduct enough trials objectively to make a real data-table. Hence, sadly those charts are nothing but a mathematical contstruct.

This does not mean the results they project are totally wrong, but I think its very important to realise that they are theoretical projections based on an unsubstantiated set of equations someone was messing about with at that time - and are NOT - repeat..NOT test data. I quote from the real report below that I copied myself:

"In a recent report on the dog-fight Gates gives an analysis whereby the performance on an aeroplane in steady spiral flight at full throttle can be estimated from its measured full throttle performance in straight flight (partial climbs and top speed); the analysis leads to a compact diagram from which the radius and time of turn, and the corresponding rate of ascent or descent can be obtained at any given airspeed and normal "g", such diagrams have been constructed for the Spitfire and Me109, and are given in Fig 17 together with an explanation of their use"

(Figure 17 is the chart you posted)

Personally I regard the whole report as....well... I`ll give you another quote and leave it for you to decide.

"The tests have shown that as a fighter the Me109 is in general inferior to the Hurricane or Spitfire"

Possibly my favourite quote from any WW2 performance comparison report follows - which basically translates as "the Spitfire turns much tighter except when it doesnt". My view is that its almost impossible to compare combat aircraft of any kind unless the difference between them is almost a generation.

"The Me.109 pilot suceeded in keeping on the tail of the Spitfire in many cases, despite the latter aeroplane`s superior turning performance, because a number of the Spitfire pilots failed to tightern up the turn sufficiently." (page 32)

Incidentally if anyone wants to go read this themselves, they can do by going to Kew in London and asking for "AVIA-6-8714"

 

[Shortround6]

I don't particularly care if the chart isn't 100% accurate. I knew that it was a mathematical construct.
However it points out the absurdity of trying to pick one "test" such as the time to turn a 360 degree circle (especially with both speed and radius/diameter unspecified) and use it to decide which plane turned better. Or to try to come up with a "simple" equation/formula based on wing loading or some other basic parameter.
I would also note that the chart is figured for 12,000ft and that the ability to sustain a turn is tied to the surplus/excess power available.
Different wings are going to have different "lift" at different altitudes affecting the turning circles and since the surplus/excess also varies (by a greater amount) with altitude sustained turns are going vary considerably with altitude.
They are also going to vary considerably between different models of the same aircraft if the engines vary in power by much.

 

[pbehn]

I don't particularly care if the chart isn't 100% accurate. I knew that it was a mathematical construct.
However it points out the absurdity of trying to pick one "test" such as the time to turn a 360 degree circle (especially with both speed and radius/diameter unspecified) and use it to decide which plane turned better. Or to try to come up with a "simple" equation/formula based on wing loading or some other basic parameter.
I would also note that the chart is figured for 12,000ft and that the ability to sustain a turn is tied to the surplus/excess power available.
Different wings are going to have different "lift" at different altitudes affecting the turning circles and since the surplus/excess also varies (by a greater amount) with altitude sustained turns are going vary considerably with altitude.
They are also going to vary considerably between different models of the same aircraft if the engines vary in power by much.

To me the imaginary absurdity, held by many, is that in WW2 there were huge numbers of pilots who engaged in a turning radius combat. and the loser watched the victor closing in over a series of turns and then got shot down. Malans rules of air fighting stated, do not fly straight and level for more than thirty seconds, circling around for a period of minutes is even worse.

 

[Greyman]

Personally I regard the whole report as....well... I`ll give you another quote and leave it for you to decide.

"The tests have shown that as a fighter the Me109 is in general inferior to the Hurricane or Spitfire"

I would say the report is fantastic, and the RAE's conclusions on the 109's general inferiority are sound - based on their criteria - where overall dogfighting ability appears paramount.

 

[Zipper730]

Advance ratio is airspeed (ft or meters per second) divided by (diameter (ft pr meters) times rate of rotation(rev/sec); pitch is chosen from advance ratio. For more about prop parameters, see 11.7 Performance of Propellers

I'll take a look if I get the chance (I'm starting another criminal justice course -- I should major in this).

I'm writing a detailed Topgun book with the school's founder, and he describes how (in specific circumstances) the F-4 could turn with other "fighterjets" if the Phantom pilot had trained to fight in deep buffet.

Actually at the corner velocity, the plane could sustain around 7g, which would put it above the sustained turn rate of the MiG-21. The problem was the corner velocity was like 420 knots, and the MiG-21's was in the 300-knot range. The F-102's were about the same, the F-106 was probably somewhat higher (10-15 knots) because it had a heavier air-frame on a similar wing (the early F-102's has a wing of 661 square feet, later on 695; the F-106A's first had a 695 square foot wing, enlarged to 697) but with a cleaner frame, better inlets it'd probably have better sustained performance.

With slatted F-4E's, you would have a turning advantage even at lower speeds that would stay with the MiG-21's and equal or beat the F-106 at some altitudes, though once you got above 31,000-32,000 feet, the F-106 could stay with them or exceed their turn

It is way above my pay grade on aerodynamics but I was under the impression that the deployment was dependent on the wings angle of attack, in a combat situation no more or less dangerous than for an opposing Spitfire for example as the speeds were about the same.

Well, technically it was a function of dynamic pressure and g-load

 

[FLYBOYJ]

The F-4 required some skill to fly it, due to a combination of heavy adverse yaw and a highly swept wing, you'd be using fairly firm rudder inputs with aileron under some case, and at higher alpha, you'd just be using the rudder and centering the stick, pulling back as needed to hold the g-load.

And where are you getting your reference for this? I've flown in an F-4, did some aerobatics and found you needed very little rudder at lower speeds. At high speeds you didn't touch the rudder

 

[Zipper730]

And where are you getting your reference for this?

There was a book entitled "Clashes", but also this
View: https://www.youtube.com/watch?v=Y6RcTtGfG3E
which seem to have similarities in descriptions.

 

[Greyman]

I've wondered why that happened: There were some guesses about that, as well as some personal speculation.

5.1 Dog fights with Spitfire and Hurricane .

...

When the Me.109 was following the Hurricane or Spitfire, it was found that our aircraft turned inside the Me.109 without difficulty when flown by determined pilots who were not afraid to pull their aeroplanes round hard in a tight turn. In a surprisingly large number of cases, however, the Me.109 succeeded in keeping on the tail of the Spitfire or Hurricane during these turning tests, merely because our pilots would not tighten up the turn sufficiently from fear of stalling and spinning.

...

5.4 Discussion .

...

As mentioned in 5.1., the Me.109 pilot succeeded in keeping on the tail of the Spitfire in many cases, despite the latter aeroplane's superior turning performance, because a number of the Spitfire pilots failed to tighten up the turn sufficiently. If the stick is pulled back too far on the Spitfire in a tight turn, the aeroplane may stall rather violently, flick over on to its back, and spin. Knowledge of this undoubtedly deters the pilot, particularly if he is not very experienced, from tightening his turn when being chased.

 

[FLYBOYJ]

There was a book entitled "Clashes", but also this
View: https://www.youtube.com/watch?v=Y6RcTtGfG3E
which seem to have similarities in descriptions.

I could tell you that's very generic and probably the same on about dozen combat aircraft of the period. You could actually roll an F-4 with the rudder only (the aircraft shakes and buffets while this is going on). I would disagree that the F-4 "required some skill to fly it." Like any combat aircraft of the day, "training enables capability." Don't buy into many of those 1960's training clips, they could be a little over-dramatic.

It is a cool clip though!

 

[Shortround6]

I've wondered why that happened: There were some guesses about that, as well as some personal speculation.

• The Me-109's slats acted as a stall-warning device, which the Spitfire did not have: This allowed them to better gauge when they were getting close to stalling
• The Spitfire seemed to indicate a tendency for being potential twitchy on the controls (neutral stability), so some pilots might have feared snapping the wings off

Please remember that there were no anti-suits, and no "G" meters in the cockpit. Pulling 5-6 "G"s means you are near blacking out (or at least greying out) and your arms are 5-6 times heavier than normal while trying to control the stick. Nobody pulled a perfect 5 "G" turn. There was constant adjustment of the elevators to control the turn and the actual "G"s could fluctuate considerably from one second to the next even in a 10 second 180 degree turn.

I don't think anybody really worried about snapping wings off, this wasn't WW I. What they worried about was stalling the plane while turning at over a 70 degree bank and snapping into an inverted spin. Usually fatal if done at low altitude.
Low time pilots in just about all WW II fighters rarely pushed the aircraft to the aircraft's limits (official).

 

[pbehn]

5.1 Dog fights with Spitfire and Hurricane .

...

When the Me.109 was following the Hurricane or Spitfire, it was found that our aircraft turned inside the Me.109 without difficulty when flown by determined pilots who were not afraid to pull their aeroplanes round hard in a tight turn. In a surprisingly large number of cases, however, the Me.109 succeeded in keeping on the tail of the Spitfire or Hurricane during these turning tests, merely because our pilots would not tighten up the turn sufficiently from fear of stalling and spinning.

...

5.4 Discussion .

...

As mentioned in 5.1., the Me.109 pilot succeeded in keeping on the tail of the Spitfire in many cases, despite the latter aeroplane's superior turning performance, because a number of the Spitfire pilots failed to tighten up the turn sufficiently. If the stick is pulled back too far on the Spitfire in a tight turn, the aeroplane may stall rather violently, flick over on to its back, and spin. Knowledge of this undoubtedly deters the pilot, particularly if he is not very experienced, from tightening his turn when being chased.

All I read from this is that experienced pilots do better than inexperienced ones, which is well known.

 

[pbehn]

Well, technically it was airspeed and g-load...

I've wondered why that happened: There were some guesses about that, as well as some personal speculation.

• The Me-109's slats acted as a stall-warning device, which the Spitfire did not have: This allowed them to better gauge when they were getting close to stalling
• The Spitfire seemed to indicate a tendency for being potential twitchy on the controls (neutral stability), so some pilots might have feared snapping the wings off

Please explain how the g load deployed the leading edge slats? I believe it is the angle of attack of the wing because I read it here. (My bold) Leading-edge slat - Wikipedia

Slats were first developed by Gustav Lachmann in 1918. A crash in August 1917, with a Rumpler C aeroplane on account of stalling caused the idea to be put in a concrete form, and a small wooden model was built in 1917 in Cologne. In 1918, Lachmann presented a patent for leading-edge slats in Germany. However, the German patent office at first rejected it as the office did not believe in the possibility of increasing lift by dividing the wing.[4][5]

Independently of Lachmann, Handley Page Ltd in Great Britain also developed the slotted wing as a way to postpone stall by reducing the turbulence over the wing at high angles of attack, and applied for a patent in 1919; to avoid a patent challenge, they reached an ownership agreement with Lachmann. That year a De Havilland D.H.9 was fitted with slats and flown.[6] Later, a D.H.4 was modified as a monoplane with a large wing fitted with full span leading edge and back ailerons (i.e. what would later be called flaps) that could be deployed in conjunction with the leading-edge slats to test improved low speed performance.[7] Several years later, having subsequently taken employment at the Handley-Page aircraft company, Lachmann was responsible for a number of aircraft designs, including the Handley Page Hampden.

Licensing the design became one of the company's major sources of income in the 1920s. The original designs were in the form of a fixed slot in the front of the wing, a design that was found on a number of STOL aircraft.

During World War II, German aircraft commonly fitted a more advanced version that pushed back flush against the wing by air pressure to reduce drag, popping out when the angle of attack increased during slower flight. Notable slats of that time belonged to the German Fieseler Fi 156 Storch. These were similar in design to retractable slats, but were fixed non-retractable slots. The slotted wing allowed this aircraft to take off into a light wind in less than 45 m (150 ft), and land in 18 m (60 ft). Aircraft designed by the Messerschmitt company employed automatic, spring-loaded leading-edge slats as a general rule, except for the Alexander Lippisch-designed Messerschmitt Me 163B Komet rocket fighter, which used fixed slots built integrally with, and just behind the wing panel's outer leading edges instead.

 

[pbehn]

• The Me-109's slats acted as a stall-warning device, which the Spitfire did not have: This allowed them to better gauge when they were getting close to stalling
• The Spitfire seemed to indicate a tendency for being potential twitchy on the controls (neutral stability), so some pilots might have feared snapping the wings off

The slats did not act as a stall warning device with expert pilots because they continued to push in a turning combat after they deployed. The Spitfire had the same stall warning as most aircraft of the period, that is buffeting on the wings caused by the washout. In this respect the Spitfire was better than most. As previously, many pilots were in combat during the BoB with just 50 hours on type whereas 200 hrs is actually needed. With the extra 150 hrs pilots become familiar with stall performance and stall recovery. Did any Spitfire actually snap its wings off, ever, while turning?

 

[swampyankee]

The slats weren't stall warning devices; they were stall preventing devices. Also, the Tiger Moth, produced before WW2, had automatic leading edge slats. Like a lot of aero things, people talked.

Tapered wings, unless there is enough washout, will stall from the tips first, as tapered wings have greater lift coefficients towards the tips. This is bad, as that's where one puts the ailerons and the separated flow from the stalled wing won't hit anything, so there's no buffeting, i.e., no warning. In an aircraft like the Bf109, which was built with little washout in the wing, the tips would stall first, leading to loss of lateral control (this may lead to a problem known as "crashing," as it's likeliest to happen near the ground, on approach). By putting on the automatic slats, the tips don't stall, so lateral control can be maintained even after the wing is stalled at the root.

The Spitfire, by the way, had washout and an elliptical wing; it's wing may have stalled from the root out, which is what you want. The most extreme aircraft design to prevent tip stall was the XF-91, proof that US designers may not have been teetotallers.

 

[Zipper730]

When the Me.109 was following the Hurricane or Spitfire, it was found that our aircraft turned inside the Me.109 without difficulty when flown by determined pilots who were not afraid to pull their aeroplanes round hard in a tight turn. In a surprisingly large number of cases, however, the Me.109 succeeded in keeping on the tail of the Spitfire or Hurricane during these turning tests, merely because our pilots would not tighten up the turn sufficiently from fear of stalling and spinning. . .If the stick is pulled back too far on the Spitfire in a tight turn, the aeroplane may stall rather violently, flick over on to its back, and spin.

So the issue was the fear over being able to properly gauge when they'd stall?

Please remember that there were no anti-suits, and no "G" meters in the cockpit. Pulling 5-6 "G"s means you are near blacking out (or at least greying out) and your arms are 5-6 times heavier than normal while trying to control the stick. Nobody pulled a perfect 5 "G" turn. There was constant adjustment of the elevators to control the turn and the actual "G"s could fluctuate considerably from one second to the next even in a 10 second 180 degree turn.

That makes sense, different amount of stick forces are needed to pull a given g-load at a given speed.

What they worried about was stalling the plane while turning at over a 70 degree bank and snapping into an inverted spin.

Would that flood the engine?

Low time pilots in just about all WW II fighters rarely pushed the aircraft to the aircraft's limits

Makes enough sense: They don't know what they can and cannot get away with... there's natural skill in that, but also practice is often a helpful cure.

Please explain how the g load deployed the leading edge slats?

Automatic slats were extended through usually two means: Dynamic pressure and G-load

• Slats extend outwards and downwards opening up an aerodynamic gap between the slat and the leading edge, which increases lift and delays stall-onset
  
• G-load is correlated to lift, and lift is related to angle of attack and airspeed
• As angle of attack increases, g-load increases until a stall occurs; at low speeds, the amount of lift available ranges from being able to maneuver only to a minimum extent, to actually stalling at the point at which you are holding 1g (stall speed).
• The extension of the slats as a function of dynamic pressure ensures that when lift is very low, the slats will come out and increase it.
  
• The extension of the slats as a function of g-load ensures that they come out when angle of attack is high

The slats did not act as a stall warning device with expert pilots because they continued to push in a turning combat after they deployed.

It would provide a guide as to how close you were getting...