Roll Rates "problem"

[Roland_HUNter]

Greetings!
 

After testing several aircraft in-game under roughly identical conditions (~500 km/h IAS at ~3000 m altitude), I compared the measured roll rates against a simple aerodynamic approximation:

RR≈K×VbRR \approx K \times \frac{V}{b}RR≈K×bV

Where:

• RRRRRR = roll rate (deg/sec)
• VVV = speed
• bbb = wingspan
• KKK = empirical handling coefficient

This is obviously not a perfect engineering formula, but it provides a reasonable approximation for WWII fighter roll performance.

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Bf 109 F-4

Measured values

• Left roll with rudder assist: 3.8 sec
• Right roll with rudder assist: 4.2 sec

Calculated roll rates

360/3.8≈94.7∘/s360 / 3.8 \approx 94.7^\circ/s360/3.8≈94.7∘/s 360/4.2≈85.7∘/s360 / 4.2 \approx 85.7^\circ/s360/4.2≈85.7∘/s

Approximation calculation

Data:

• Speed: V=500V = 500V=500
• Wingspan: b=9.92 mb = 9.92\ mb=9.92 m
• Estimated coefficient: K≈1.6−1.9K \approx 1.6-1.9K≈1.6−1.9

Calculation:

1.6×5009.92≈80.6∘/s1.6 \times \frac{500}{9.92} \approx 80.6^\circ/s1.6×9.92500≈80.6∘/s 1.9×5009.92≈95.8∘/s1.9 \times \frac{500}{9.92} \approx 95.8^\circ/s1.9×9.92500≈95.8∘/s

Expected range

80−96∘/s80-96^\circ/s80−96∘/s

Conclusion

The measured values are believable and fit reasonably well within the expected historical range. The left/right asymmetry also makes sense due to:

• torque effects,
• slipstream,
• P-factor,
• yaw-roll coupling.

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Yak-1

Measured values

• Without rudder: 3.8 sec
• With rudder assist: 3.3 sec
• Left roll: 3.0 sec

Calculated roll rates

360/3.8≈94.7∘/s360 / 3.8 \approx 94.7^\circ/s360/3.8≈94.7∘/s 360/3.3≈109.1∘/s360 / 3.3 \approx 109.1^\circ/s360/3.3≈109.1∘/s 360/3.0=120∘/s360 / 3.0 = 120^\circ/s360/3.0=120∘/s

Approximation calculation

Data:

• Speed: V=500V = 500V=500
• Wingspan: b≈10.0 mb \approx 10.0\ mb≈10.0 m
• Estimated coefficient: K≈1.8−2.0K \approx 1.8-2.0K≈1.8−2.0

Calculation:

1.8×50010=90∘/s1.8 \times \frac{500}{10} = 90^\circ/s1.8×10500=90∘/s 2.0×50010=100∘/s2.0 \times \frac{500}{10} = 100^\circ/s2.0×10500=100∘/s

Expected range

90−100∘/s90-100^\circ/s90−100∘/s

Conclusion

The rudderless result (~95°/s) seems believable.

However:

• 109°/s with rudder assist,
• and especially 120°/s,

already place the Yak-1 near aircraft specifically famous for exceptional roll performance.

This suggests that rudder-induced yaw-roll coupling may be too effective.

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La-5FN

Measured values

• Right roll: 2.7 sec
• With rudder assist: 2.5 sec

Calculated roll rates

360/2.7≈133.3∘/s360 / 2.7 \approx 133.3^\circ/s360/2.7≈133.3∘/s 360/2.5=144∘/s360 / 2.5 = 144^\circ/s360/2.5=144∘/s

Approximation calculation

Data:

• Speed: V=500V = 500V=500
• Wingspan: b=9.8 mb = 9.8\ mb=9.8 m
• Estimated coefficient: K≈1.8−2.1K \approx 1.8-2.1K≈1.8−2.1

Calculation:

1.8×5009.8≈91.8∘/s1.8 \times \frac{500}{9.8} \approx 91.8^\circ/s1.8×9.8500≈91.8∘/s 2.1×5009.8≈107.1∘/s2.1 \times \frac{500}{9.8} \approx 107.1^\circ/s2.1×9.8500≈107.1∘/s

Expected range

92−107∘/s92-107^\circ/s92−107∘/s

Conclusion

The measured 133-144°/s values appear significantly above the expected range.

The La-5FN was a strong fighter, but historically it was not known for Fw 190-level roll authority.

The measured values place it extremely close to the Fw 190A-5.

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Fw 190A-5

Measured values

• Without rudder: 3.0 sec
• With rudder assist: 2.5 sec

Calculated roll rates

360/3.0=120∘/s360 / 3.0 = 120^\circ/s360/3.0=120∘/s 360/2.5=144∘/s360 / 2.5 = 144^\circ/s360/2.5=144∘/s

Approximation calculation

Data:

• Speed: V=500V = 500V=500
• Wingspan: b=10.5 mb = 10.5\ mb=10.5 m
• Estimated coefficient: K≈2.7−3.3K \approx 2.7-3.3K≈2.7−3.3

Calculation:

2.7×50010.5≈128.6∘/s2.7 \times \frac{500}{10.5} \approx 128.6^\circ/s2.7×10.5500≈128.6∘/s 3.3×50010.5≈157.1∘/s3.3 \times \frac{500}{10.5} \approx 157.1^\circ/s3.3×10.5500≈157.1∘/s

Expected range

129−157∘/s129-157^\circ/s129−157∘/s

Additional historical note

It is also worth noting that some reports place the Fw 190’s peak roll rate around 180°/s, especially at favourable medium-high speeds.

That means the Fw 190A-5 in-game result of:

360/2.5=144∘/s360 / 2.5 = 144^\circ/s360/2.5=144∘/s

may not be excessive at all. In fact, it may even be conservative compared to some historical reports.

Conclusion

The Fw 190A-5 measurements align well with both historical reputation and approximate aerodynamic expectations.

This aircraft was historically famous for:

• exceptional roll rate,
• excellent aileron authority,
• low stick forces,
• outstanding high-speed lateral control.

---

Final Observation

The problem is not that the Fw 190A rolls too fast. If anything, several reports suggest that the Fw 190 could achieve roll rates around 180°/s under favourable conditions. Therefore, the measured in-game value of 144°/s for the Fw 190A-5 is not unreasonable and may even be conservative.

The concern is that the Yak-1 and especially the La-5FN can approach or match Fw 190A-5 roll performance when rudder assistance is heavily involved.

Historically, the La-5FN was a strong fighter, but it was not known for Fw 190-level aileron authority or roll performance.

This may indicate:

• overly strong yaw-roll coupling,
• excessive rudder-assisted roll behaviour,
• or inflated low/medium speed lateral authority on some Soviet aircraft.

Thanks for reading.

Roland_HUNter

Edited May 19 by Roland_HUNter

[GiftGruen]

Interesting!

500kp/h IAS is maybe a somewhat high manoevring speed (?) … I‘d rather take 400 here. Not sure what IAS is typically taken as a good starting point.

Also 3000 is rather a height where the 190 feels not so good. Numbers at 1000 and/or 4000 could be interesting also. But this is just a feeling and/or a input that it could make sense to have more than one measurememt.

And .. yes - I admit - myself I am too lazy to support here 😉

Edited May 19 by GiftGruen

[LukeFF]

This report means nothing without (1) original source data attached and (2) track files. You know this, @Roland_HUNter.