Performance of the Fw 190A on the Deck?

[Boomerang]

Gentlemen:

Are there comments about the report in Don Caldwell's excellent JG 26 War Diary Vol 2 that 'The survivors claim today that the Fw 190A could outrun any Allied fighter on the deck, regardless of the official performance figures'.

This statement occurs in the section of the book dealing with JG26's role in Normandy after D Day, so it would apply e.g. to performance of the 190 A versus the Spitfire IX, not the Spitfire XIV, and similarly for the other Allied fighters.

I was a bit surprised by this statement, but presumably getting this sort of this correct was literally a matter of life or death. This forum has also taught me that assessing aircraft performance is more complex than reading simplistic tables of numbers.

On a technical level, would excellent speed on the deck relate to the radial versus in-line engine issue?

Thanks

Don W (Boomerang)

[Graham Boak]

The maximum speed at sea-level is linked to the maximum speed at full-throttle height, and has no connection to the inline/radial choice. For a first stab at understanding more, plot a graph of airspeed (x-axis) against altitude (y-axis). Many sources will quote speeds at different altitudes, usually sea level and at the full throttle height of each supercharger setting. You can draw a straight line linking the sea-level value and the first full-throttle height point. The slope of this line will be the same for all types of similar performance. (Not quite true, but good enough to make the point.) Thereafter, plotting any max. speed point will allow you to find an approximate sea level speed.

Beware aircraft with two-speed superchargers (eg Spitfire Mk.IX), use the point for the lower full throttle height not the absolute best.

The statement is clearly made by the survivors, as there certainly are Typhoon pilots who succeeded in catching and shooting down Fw 190 low-level raiders. Also the Spitfire Mk.XII, of course. In practice the types were so close that the difference between individual examples was more important: a "good" Fw would run away from a "poor" Typhoon, and vice versa. More generally, of course, successful pilots will always believe that their aircraft is better than the opposition, as long as the types are broadly similar. For them, it has been.

[drgondog]

Originally Posted by Graham Boak

The maximum speed at sea-level is linked to the maximum speed at full-throttle height, and has no connection to the inline/radial choice. For a first stab at understanding more, plot a graph of airspeed (x-axis) against altitude (y-axis). Many sources will quote speeds at different altitudes, usually sea level and at the full throttle height of each supercharger setting. You can draw a straight line linking the sea-level value and the first full-throttle height point. The slope of this line will be the same for all types of similar performance. (Not quite true, but good enough to make the point.) Thereafter, plotting any max. speed point will allow you to find an approximate sea level speed.

Beware aircraft with two-speed superchargers (eg Spitfire Mk.IX), use the point for the lower full throttle height not the absolute best.

The statement is clearly made by the survivors, as there certainly are Typhoon pilots who succeeded in catching and shooting down Fw 190 low-level raiders. Also the Spitfire Mk.XII, of course. In practice the types were so close that the difference between individual examples was more important: a "good" Fw would run away from a "poor" Typhoon, and vice versa. More generally, of course, successful pilots will always believe that their aircraft is better than the opposition, as long as the types are broadly similar. For them, it has been.

Excellent points.

Objectively, the P-51B-15 for example, had a 1650-7 engine with better low altitude capability than the -3 and was extremely fast on the deck.

Based on flight test data, and assuming both engines were operating correctly it is hard to expect a 190A7 for example, or even a D-9 to outrun this Mustang on the deck.. and the -15 was plentiful during the Normandy campaign

I forgot to mention one other fact about the 51 - namely the extremely low wetted drag of the airframe in comparison with the Spit and Fw 190A. The D-9 was closer to the 51.

[Nick Beale]

I go along with Graham's comments: the more Allied pilots' accounts I see, the more confused I get. One day they'll say they could easily catch a given type of enemy aircraft, the next " these [whatever] were too fast" or "we were unable to close" etc. The performance figures we all use don't seem to apply!

I'm sure a lot had to do with the particular situation of a combat but I also wonder whether individual machines of the same type were much more variable in performance than we now realise? Certainly you read pilots saying that a particular aircraft they flew was aither a good or a bad one of the type.

[Boomerang]

Gentlemen:

Now that the forum is running again, I can thank you for your responses.

I must say (based I'm sure on a much smaller sample) that I share Nick's thoughts - there doesn't seem to be the simple correlation between reports of fighter versus fighter combat that you might expect from published performance data.

One final point - is there any possibility that the fuel status of an aircraft would have a noticeable effect on performance i.e. an aircraft low on fuel would have greater speed than one with near full tanks?

Regards

Don W

[yogybär]

Yes, fuel status definitely is very important, especially on a P-51!

Apart from that some technical factors on the not exactly, maybe even misidentified Luftwaffe AC which influence these "races":
- subtypes of 109G-x; 109K; 190A-x; 190F-x 190D-x(MW-50 yes/no) with different engine-subtypes
- did the german use WEP-systems like MW-50 or GM-1 or "erhöhter Laderdruck" (if available&working on his plane).
- maybe the german had external loadouts like MG151/20-gondolas, a droptank, bomb(s) - bombracks themselves can cause ca. 15km/h difference in v_max!
- status of the german A/C's surface due to bad painting, dirt, bad repairs, removed covering etc. pp.
- trim status
...

We can see: A lot was possible.

[Crumpp]

If we examine the shape of the L/D curve for each of these designs, then we can see some important differences in the combat qualities.

All the best,

Crumpp

[Harri Pihl]

The correct way to to calculate the effect of the weight to speed is to calculate the change of the induced drag due to changed Cl and find the new balance between thrust and the drag by iteration method.

As an example if we assume that the Typhoon does 580km/h at sea level with 2200hp and 80% propeller efficiency at 4800kg. With these parameters a 500kg weight increase will decrease speed by 1,92km/h.

[Crumpp]

I'm guessing that a = loaded (bombed-up?) and b = unloaded, while the figures are kilometres per hour/kilometres of altitude (remembering that in German a comma is used where English uses a decimal point).

You are correct Nick! The speeds wouldn't be labeled Va, Vack, Vw, Vwck would they?

[Crumpp]

The correct way to to calculate the effect of the weight to speed is to calculate the change of the induced drag due to changed Cl and find the new balance between thrust and the drag by iteration method.

I assure, we are using the correct BGS Algebraic formulation to predict performance in the event of a weight change.

Credit to John E Lewis and Charles E Dole:

A former Marine, the late CHARLES E. DOLE taught flight safety for 28 years to officers of the U.S. Air Force, Army, and Navy, as well as at the University of Southern California.

JAMES E. LEWIS is a former aeronautical engineer for the Columbus Aircraft Division of Rockwell International and a retired Ohio National Guard military pilot. He is currently an Associate Professor of Aeronautical Science at Embry Riddle Aeronautical University in Daytona Beach, Florida.

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All the best,

Crumpp