Fw190D9 and Fw190A8 R1, weights and handling

[MANDO]

About empty weight, both aircrafts had similar armour, exactly the same wing area as well as main fuel tanks, radio and navigation equipment.

A8 had the 1228 Kg BMW 801D-2 engine while D9 had the 920Kg Jumo 213-A1 engine. We should add an unknown weight for 190A8 C3 injection system and MW-50 for D9. Few pounds should be also considered for the 1.24m extra airframe lenght for the Dora, probably compensated with two extra Mg151/20 for the A8.

Considering all the above, we still have an empty D9 44 lbs heavier than an empty A8 R1 (7694 lbs vs 7650 lbs). From where comes the extra weight of the D9?

On the contrary, operational weights for D9 (with ETC) are between 200 and 80 lbs lighter than A8 R1 (without ETC). And that weight should come from differences between B4/M50 and C3 weights as well as 20mm ammo for the outer A8 20mm guns.

Being these weights correct, D9 should be as maneuverable or more than the A8 in fighter configuration, but all and every simulation (including AH) give the turning advantage to the A8 R1, is there something that I'm missing here?

[Kurfürst]

Strange but interesting. I think the engines would be the key, the airframes were rather similiar, and the difference between the weight of C-3 or B-4 is negligable... altough MW is heavier than normal fuel, for CoG reasons the same weight was loaded in the rear tank with less volume.

Something to keep in mind that the listed weights for the engines are dry weights, without accessories. The latter can differ in total weight, and there`s a lot associated with the Jumo 213 that don`t exist with the radial BMW : weight of radiators, piping, coolant weight, also oil volume can be different.

[MiloMorai]

Tech Description #284 list the powerplant for the A-8 as 1661kg. The TU engines increases the weight by 35kg.

Be careful with liquid cooled engines. Sometime it is the 'dry' weight and sometimes the 'wet' weight that is listed.

[HoHun]

Hi Mando,

>Being these weights correct, D9 should be as maneuverable or more than the A8 in fighter configuration, but all and every simulation (including AH) give the turning advantage to the A8 R1, is there something that I'm missing here?

Carried over from Air Warrior ;-)

Regards,

Henning (HoHun)

[JB42]

Not so sure on the weight problem, but I may shed some light on the handling equation. While most say the Dora and A8 are "similiar", one needs to consider too many similiars and not enough exactlies makes the two planes not so similiar (think).

1) The obvious. The Dora is longer. Simply put, the difference between maneuvering in a Ford F150 and F250.

2) The Dora had larger vertical surfaces. Anyone who flies it in AHII knows the infinitely better stability the Dora has over the A8. Sometimes the ability to get to the threshold of stability plays a key part in handling.

3) The Dora was much more aerodynamic and sleek. While in most cases one thinks of things like drag as a negative, the A8s tendency to lose aerodynamics faster allowed for its ability to turn tighter (slower the plane, tighter the turn).

[MANDO]

1) 1.2m longer only. In any case, the longer tail will make the elevators lighter, this may help with hi speed turns.
2) The longer vertical stab will add a bit more of lateral stability and more rudder authority, it will not affect negatively the turn rate/radious.
3) If you mean that A8 will slow down faster, this will not help the turn, just the opposite. As a rule, the more time you are able to keep near corner speed, the better. Slower means thighter turn, but also slower turn rate. If you need to slow down with D9, simply use rudder and chop throttle. Tighting the turn at slow speeds, the D9 should still be able to outturn the A8, less wing loading, less drag, more power. All I see are advantages.

I'm still thinking D9 should turn better than A8 R1 and have a slower stall speed.

[Crumpp]

Depends on the Dora being modeled.  All Dora's weighed less but when first introduced had less Hp than the FW-190A8's.

They would have turned a little worse or the same.  The BMW-801TH, TU, and TS 190A's would have outperformed them in the turn.  The low altitude performance would have been very comparable in other aspects.  This is one of the reason's for the lukewarm reception the Dora first received in the Jagdwaffe.

Less than a month later, when the Dora was given more power, it outperformed the FW-190A.  The last Dora 9 models using C3 and MW 50 made the FW-190A series obsolescent as a fighter.

All the best,

Crumpp

[leitwolf]

The handling differences of the D and A series puzzled me to no end when i flew mainly 190s. It's an honest interest .. I'd really appreciate an explanation why those two would handle so differently.  

There was a huge thread about the D-9s engine quite a while ago in AH1 days. If i remember correctly the number was ~1900hp.

All I can think of is that the longer inline engine places more weight in front of the CG than the shorter radial engine. But then the D-9s tail is also longer...

[JB42]

But the elevators themselves remained untouched. I would imagine that even though they're "lighter" their authority through out the turn would have to decrease now being further from the fulcrum. More plane is still more plane, 1.2m or 10 ft.

Part of lateral stability is trying to keep the plane on the line its on. The increased stability is countering the urge for the plane to change direction.

Pull into your driveway tonight at 10mph, tomorrow at 30 mph. Get back to me which was not only tighter, but how fast you got to your garage door ( if you even wind up near your garage at 30mph )

[Glasses]

Then back slowly and forward into your garage and say to it was it good for you?

[Crumpp]

But the elevators themselves remained untouched.

The hingeing of the elevators was changed several times in the life of the FW190 design.

I would imagine that even though they're "lighter" their authority through out the turn would have to decrease now being further from the fulcrum.

Being further from the fulcrum is a good thing for force multiplication:

The further the effort is from the fulcrum, the easier a lever is to move so in general long levers are more useful.

http://www.scienceyear.com/under11s/index.html?page=/under11s/levers/

Facts are the Dora should outturn the FW-190A8.

All the best,

Crumpp

[Angus]

Allied fighter pilots looked at the "long nosed" 190's with some respect

[FUNKED1]

Tail length and maneuverability are inversely related.

[Crumpp]

Tail length and maneuverability are inversely related.

Read David Lednicers article on WWII Fighter Aerodynamics.  Kurt Tank was no slouch when it came to aircraft design.  The extended fuselage allowed a fixed neutral point shift in the CG to counter the FW-190A's rearward shifting CG trend in the design due to extra equipment being mounted in the aft fuselage (radios, Aux. tanks, etc...).  The extended fuselage kept the Dora "just statically stable, stick fixed and free, engine off" and "statically unstable to a slight degree, engine on."  

The Dora was lighter and could turn better than the FW-190A except for the very first few weeks of it's design life.

All the best,

Crumpp

[FUNKED1]

Longitudinal stability margin and maneuverability are also inversely related.

The tail was lengthened to increase stability margin, not to reduce it.

Or rather the tail was lengthened to maintain stability margin in the presence of an aft CG shift.

In any case, lengthening the tail makes an airplane more longitudinally stable, all else being equal.  Leverage works for the stabilizer just as much as for the elevator.  A good flight mechanics textbook will have all the derivations if you require further info.  Cheers.