Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: MANDO on March 14, 2005, 08:44:56 AM
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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?
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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.
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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.
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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)
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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).
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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.
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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
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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... :confused:
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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 :p )
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Then back slowly and forward into your garage and say to it was it good for you?
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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
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Allied fighter pilots looked at the "long nosed" 190's with some respect ;)
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Tail length and maneuverability are inversely related.
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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
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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 (http://www.amazon.com/exec/obidos/tg/detail/-/0471575062/qid=1110919422/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/103-7587601-1112663?v=glance&s=books&n=507846) will have all the derivations if you require further info. Cheers.
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Nice reply funked1. Thanks but already know the information.
Your "premise" that the fuselage lengthening canceled out the thrust gains and wingloading decrease is not correct by either the science or the pilots that flew both types.
For further reading I will direct you to:
http://www.enotalone.com/books/047168046X.html
The information is found in several locations in the book. Page 202 at the bottom explains it best.
In a nutshell, Minimum level turn radius occurs at CLmax provided Pa = > Pr.
If you require further information I am sure any good flight mechanics textbook can answer your questions.
Longitudinal stability margin and maneuverability are also inversely related.
Yes very true. Your implying a "degree" of stability that did not exist. The FW-190 was a fighter, not a trainer. Compare it to the Spitfires longitudinal stability and then come back.
All the best,
Crumpp
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Originally posted by Crumpp
Your "premise" that the fuselage lengthening canceled out the thrust gains and wingloading decrease is not correct by either the science or the pilots that flew both types.
That's not my premise. I just wanted to refute Mando's oft-stated claim that a longer tail will make an airplane more maneuverable due to some sort of leverage.
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Oh yeah and CLmax, Pr = Pa, good times, that will work. :)
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That's not my premise. I just wanted to refute Mando's oft-stated claim that a longer tail will make an airplane more maneuverable due to some sort of leverage.
Np! :)
All the best.
Crumpp
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came across some weights in Hermann's Dora book.
DD603E - 1644.75kg
Jumo 213 - 1642kg.
Heinz Lange IV./JG51 on the Dora
The 190A was slightly better in a turn, but had an outstanding RoC.
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There can only be one Dora
(http://www.nickjapan.com/img/Dora.jpg)
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Originally posted by MiloMorai
came across some weights in Hermann's Dora book.
DD603E - 1644.75kg
Jumo 213 - 1642kg.
Heinz Lange IV./JG51 on the Dora
The 190A was slightly better in a turn, but had an outstanding RoC.
These weights are wet, right? I think 1228Kg is for dry 801D2 weight, no idea about wet.
Is Heinz referring to 190A8 R1 (no way IMO)?
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Hi Mando,
I've prepared a turn rate comparison between the Fw 190D-9 (4250 kg, 2100 HP @ 0 km) and the Fw 190A-8 (4270 kg, 1800 HP @ 0 km), and that's what I came up with:
D-9 vs. A-8 turn rate:
0 km: 109%
1 km: 110%
2 km: 113%
3 km: 115%
4 km: 115%
5 km: 112%
6 km: 107%
7 km: 106%
8 km: 105%
9 km: 105%
So the D-9's turn rate should be superior to the A-8's at all altitudes - quite obvious, considering it has more power at virtually the same weight.
The elevator effectiveness certainly is sufficient to achieve the necessary angle-of-attack in a sustained turn, so the different fuselage length makes no difference.
(Fuselage lift, which I haven't figured in, might make a slight difference. I'd suspect in favour of the Dora with its larger fuselage, but that's only a guess.)
If the Fw 190A-8 is allowed to use Erhöhte Notleistung, it might catch up a little, but I don't have good data on the resulting power curve.
Regards,
Henning (HoHun)
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Nice Work Hohun!
Thanks for the calculations.
Milo, check out Ossenkop's evaluation in the same reference in comparision to the FW-190A8.
Thanks for digging out the engine weights.
Looks like it depends on the Dora and FW-190A being tested. Early Dora vs FW-190A8/A9 would have different results vs Mid/Late Dora.
All the best,
Crumpp
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Isn't the Dora with a slightly more span also?
(Silly question, could of course look it up somewhere)
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No Angus (at least for D9, no idea about D11 or D12).
Thanks for your calculations HoHun.
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For some reason I'd think the A to be slightly better in turns and in roll.
Maybe it is how I figure out the drag vector component location of the radial versus liquid cooled. According to my reasoning the D would be even worse if it did not have the radiators in the nose but under the wings...
I don't believe in leverage theory as the A version already was fully able to pull into an accelerated stall. The wing profile tolerates only so much AoA no matter how far the tail is from the main wing.
:confused:
-C+
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For some reason I'd think the A to be slightly better in turns and in roll.
It all depends on which Dora and which Anton your comparing.
All the best,
Crumpp
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Bring your Dora
Bring your Dora to the slaughter let her go let her go let her go Let Her go!< Drum solo!>
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If you just look at the latest books and veteran statements, it can be said that the D9 had in general a slightly better and tighter turn.
Lt. Crumpp flew a comparison flight in his D9 against and A9 from JG2 and could slowly gain in a low alt turning contest.
Lt. Ossenkop mentions both the better longitudinal stabiliy as the D9 had less tendency to swing on take off. He also mentions that the D9 could be turned harder because flow seperation accured later than on the A-Series. And he points to lower elevator forces in the D9 due to the extended fuselage.
Oblt. Romm tells us he could maintain a higher speed in turns with the D9 to follow Yaks and LAs that required him to slow do minimum turning speed in his A8. Indicating that the D9 had a slightly better turn radius and speed of turn.
At all no wonder, if we just compare a very early D9 with ca. 1750PS and 4250kg takeoff weight to the contemporay A8 with ca. 1800PS and 4270kg, take into account that the D9 airframe is less dragy and that the D9 in this case would benefit from the VS111 airscrew compared to the metal VDM prop of the A8.
Now as Crumpp mentioned it depends on which D9 you compare to which A8/A9, but in general you can say the D9 will be slightly better, cause when the A9 got increased boost pressure and benefits from more engine power the D9 also got this for its JUMO213 engine.
About the roll rate its a bit more difficult. Basicly they should be almost identical because wing design on D9 & A8/9 is identical and this has the greatest impact on roll rate.
Engine torque might have influeced the roll a bit, but not so much to get a clear winner here. Same goes for wing guns. Planes with them would have slightly reduced initial roll rate, but else no difference.
The statements in Caldwells JG26 book about the loss in roll rate of the D9 are no pilot quotes, it seems they were taken from books written in the 60s and 70s were this fact was simply quoted again and again without any real evidence.