Tempest and P 51

[unreasonable]

1 hour ago, -=PHX=-SuperEtendard said:

 

Sometimes the specifications aren't quite accurate, I don't know why that happens but it's noticeable with speed and climb rate numbers. If the Clmax was 1.39 that would mean a 176 kmh stall speed for the K-4 but you can well ride it into the 160s kmh without stalling pulling AoA with the slats opened. Just as it's about to stall you can get some grey zone but this happens at around 165 kmh.

 

The Teach Specs say K4's minimum stall speed is 167-190kph. 

 

I assume in my spreadsheet that the lowest number is at minimum weight - 3006kg - no ammo, 10% fuel, ie the state you might be in as you land after a sortie. With a wing surface of 16.1 m^2, the CLmax is  1.390

 

I assume that the highest number is at maximum t/o weight, given as 3891kg. That gives a CLmax of 1.390

 

Doing the same for all the other 109 types gives a very close result to this, (except the E)  almost all in the 1.38 -1.40 range. 

 

I cannot speak for the accuracy of the tech specs numbers except that we are told they were done with a bot, to ensure, for example, that the stall speed is measured at exactly zero sink rate. 

 

 

[Panthera]

 

3 hours ago, -=PHX=-SuperEtendard said:

@Panthera DCS is not a banned word in the forums ? 

Btw you said something about the lift coefficients specially with max power on, how can it be tested more or less accurately in game? with idle engine I get around 1.60-1.65 Clmax for the K-4 in game.

 

Aah ok, wasn't sure so just wanted to be on the safe side

 

You can test it by first getting into a stable sustained turn, and then when settled pull back further and note the max amount of G's you can reliably pull at a specific speed before you start feeling the inside wing dropping. 

 

The biggest disparity noted between the match up in DCS vs IL2 is found in the sustained turn performance however, in IL2 the 109 for some reason seems to be penalized a lot more in drag when turning than other aircraft, which is a mistake if its actually the case. 

 

Edited May 28, 2020 by Panthera

[=621=Samikatz]

I would avoid using other sims as a basis for flight model changes, they can get things wrong, too. The aforementioned sim had one of their flagship aircraft have ground effect reversed for several years so they're definitely not immune to mistakes

 

Compare to the real world, where you can

[Panthera]

2 hours ago, =621=Samikatz said:

I would avoid using other sims as a basis for flight model changes, they can get things wrong, too. The aforementioned sim had one of their flagship aircraft have ground effect reversed for several years so they're definitely not immune to mistakes

 

Compare to the real world, where you can

 

Yes ofcourse, the real world is for sure also my focus for comparison, and I find the DCS 109 FM does come the closest to what I consider the most reliable real world data available whilst at the same time standing up to scrutiny in mathematical aerodynamics.

Edited May 28, 2020 by Panthera

[357th_KW]

20 hours ago, MiloMorai said:

P-51 pilots were told not to get into turning battles with the 109. If a shooting resolution could not be obtained in a 1/2 circle or there abouts they were to break off and try again.

 

I'm curious what the source of this is.

 

The US 8th AF Fighter Command took a survey of some of their successful pilots in spring of 1944 and published a training pamphlet titled "The Long Reach" for their airmen.  Osprey republished this as a book some years back titled "VIII Fighter Command at War 'Long Reach'".  It contains a series of short essays by the pilots sharing combat tactics and tips. In it, Lt Col Everett Stewart of the 355th FG wrote: "The P-51 will out-turn the Me 109 at any altitude up to 25,000 ft (performance above that altitude is unknown).  Greater difficulty is encountered in out-turning the Fw 190."

 

'Kit' Carson (an ace of the 357th FG) put together some similar suggestions and tips for new pilots in his group.  He stated the following: "If you're jumped, remember in the P-51 you've got (other than the Spitfire) the best defensive fighter in the business.  Reef it in with full power and maneuvering flaps or shove the stick right into the instrument panel - do anything you can to break his line of sight on you.  Once you've done that, he can't lay a glove on you."

 

While I've seen statements of certain US pilots who preferred to stick to dive and zoom tactics, there were also plenty who chose to mix it up.  Mike Williams' website has a whole section of P-51 encounter report statements.  In it towards the bottom are a number of reports where 8th AF pilots describe turning fights against 109s and 190s and the use of flaps in combat.

 

Here are a few other period cases I've seen regarding this topic:

 

British test pilot Eric Brown was involved in testing captured German aircraft and flew the specific captured 109 (a 109G-6/U2, with 20mm gondolas, erla haube canopy and wooden tail, wr# 41 2951 that landed in the UK by mistake in July of 44) that was used by the RAF Air Fighting Development Unit to develop their tactical recommendations.  Brown mentioned the stall characteristics: "I was particularly interested in the operation of the slats, the action of which gave rise to aileron snatching in any high-g maneuvers such as loops or tight turns, so I did a series of stalls to check their functioning more accurately.  The stall with the aircraft clean, with half fuel load and the engine throttled right back occurred at 105mph.  This was proceeded by elevator buffet and opening of the slats about 20 mph above the stall, these being accompanied by the unpleasant aileron snatching as the slats opened unevenly.  The stall itself was fairly gentle with the nose dropping and the port wing simultaneously dropping about 10 degrees.  In the landing configuration the stall occurred at 99mph with identical symptoms apart from heavier elevator buffeting."  RAF test pilots cleared spent some time understanding the stall characteristics and recognized that slat deployment was not a stall, as postulated by another poster.  The AFDU's conclusion regarding maneuverability when compared to a Mustang III (P-51B) was this: "When dived and then pulled up into a climb there was little to choose between US and German fighter, but the Mustang could steadily outdive the Bf 109G-6 and had no difficulty in out-turning the Messerschmitt."

 

Hans-Werner Lerche, a Luftwaffe test pilot had a chance to fly a captured P-51B and wrote the following of its maneuverability: "When I had acquired some practice with the Mustang, I found it fun to take off with only a little fuel, i.e. at low weight, retract the undercarriage and landing flaps at once and then immediately fly a full circle close to the ground.  Apart from everything else, this maneuver really showed the agility of this fighter."  The Luftwaffe operated a test squadron similar to the RAF's AFDU, but sadly I've never seen any reports of theirs.

[Raven109]

Isn't using pilot reports about performance a bit like survivor-ship bias? The guys who have returned said that the 109 can't turn. What about the guys that didn't return? 

 

Can you say by looking at these reports that the 109 which could not turn couldn't do so because of aircraft design, or because of pilot skill, or because of different weights? Where those max performance turns, or sustained turns? Does "out-turning" mean flat turn, or any kind of maneuverability, i.e roll rate, etc...

 

What about comparisons against the G-14, K-4, those are more powerful aircraft than the Mustang and the G-6.

 

Perhaps a lot of questions, and I fear that the answer doesn't really matter for the in-game planes. An expert will take you down even if he's flying a brick, while the defender (who thinks turn rate is everything) relies on his ride to win.

Edited May 28, 2020 by Raven109

[Panthera]

29 minutes ago, KW_1979 said:

British test pilot Eric Brown was involved in testing captured German aircraft and flew the specific captured 109 (a 109G-6/U2, with 20mm gondolas, erla haube canopy and wooden tail, wr# 41 2951 that landed in the UK by mistake in July of 44) that was used by the RAF Air Fighting Development Unit to develop their tactical recommendations.  Brown mentioned the stall characteristics: "I was particularly interested in the operation of the slats, the action of which gave rise to aileron snatching in any high-g maneuvers such as loops or tight turns, so I did a series of stalls to check their functioning more accurately.  The stall with the aircraft clean, with half fuel load and the engine throttled right back occurred at 105mph.  This was proceeded by elevator buffet and opening of the slats about 20 mph above the stall, these being accompanied by the unpleasant aileron snatching as the slats opened unevenly.  The stall itself was fairly gentle with the nose dropping and the port wing simultaneously dropping about 10 degrees.  In the landing configuration the stall occurred at 99mph with identical symptoms apart from heavier elevator buffeting."  RAF test pilots cleared spent some time understanding the stall characteristics and recognized that slat deployment was not a stall, as postulated by another poster.  The AFDU's conclusion regarding maneuverability when compared to a Mustang III (P-51B) was this: "When dived and then pulled up into a climb there was little to choose between US and German fighter, but the Mustang could steadily outdive the Bf 109G-6 and had no difficulty in out-turning the Messerschmitt."

 

Well the problem with Brown's account is described by himself: The uneven opening and snatching of the slats when he attempted to turn. This indicates something was not right with the slats on that aircraft (AFAIK it was a crashed specimen?) and that they weren't functioning correctly (German maintenance manuals stress how important it is to keep the slats in prestine condition to avoid uneven deployment or even jammed slats which could be fatal). This would lead to premature wing drop in turns and not inspire any confidence to push any further.

 

As Dave Southwood who flies the 109G2 himself put it:

"The idle power stall characteristics of the aircraft are very benign and affected little by undercarriage and flap position.  Stalling warning is a slight wing rock with the stick floating right by about 2 inches.  This occurs 10klph before the stall.  The stall itself is a left wing drop through about 15 degrees with a slight nose drop, accompanied by a light buffet.  All controls are effective up to the stall, and recovery is instant on moving the stick forward.  Stall speeds are 155kph clean and 140kph with gear and flap down.  In a turn at 280kphwith display power set, stall warning is given by light buffet at 3g, and the stall occurs at 3.5g with the inside wing dropping.  Again, recovery is instant on easing the stick forward.  One interesting feature is the leading edge slats.  When these deploy at low speeds or in a turn, a 'clunk' can be heard and felt, but there is no disturbance to the aircraft about any axis.  I understand that the Bf109E  [I think he's actually refering to Brown's test of the 109G2 here]  rolled violently as the slats deployed, and I am curious to know the difference to the Gustav that caused this."

Edited May 28, 2020 by Panthera

[357th_KW]

Just now, Panthera said:

 

Well the problem with Brown's account is described by himself: The uneven opening and snatching of the slats when he attempted to turn. This indicates something was not right with the slats on that aircraft (AFAIK it was a crashed specimen?) and that they weren't functioning correctly (German maintenance manuals stress how important it is to keep the slats in prestine condition). This would lead to premature wing drop in turns and not inspire any confidence to push any further.

 

As Dave Southwood, who flies the 109G2 himself, put it:

"The idle power stall characteristics of the aircraft are very benign and affected little by undercarriage and flap position.  Stalling warning is a slight wing rock with the stick floating right by about 2 inches.  This occurs 10klph before the stall.  The stall itself is a left wing drop through about 15 degrees with a slight nose drop, accompanied by a light buffet.  All controls are effective up to the stall, and recovery is instant on moving the stick forward.  Stall speeds are 155kph clean and 140kph with gear and flap down.  In a turn at 280kphwith display power set, stall warning is given by light buffet at 3g, and the stall occurs at 3.5g with the inside wing dropping.  Again, recovery is instant on easing the stick forward.  One interesting feature is the leading edge slats.  When these deploy at low speeds or in a turn, a 'clunk' can be heard and felt, but there is no disturbance to the aircraft about any axis.  I understand that the Bf109E  [I think he's actually refering to Brown's test of the 109G2 here]  rolled violently as the slats deployed, and I am curious to know the difference to the Gustav that caused this."

 

That particular aircraft landed at Manston after the pilot got lost, so it was likely pretty close to "serviceable" condition.  Of course that became a looser and looser definition for German aircraft towards the end of the war.  That G-6 was far from the first captured 109 the British had played with.  It's hard to know what was typical - it's possible that they worked perfectly in most aircraft - or it's possible that Southwood's experience is the aberration. 

[Panthera]

12 minutes ago, KW_1979 said:

 

That particular aircraft landed at Manston after the pilot got lost, so it was likely pretty close to "serviceable" condition.  Of course that became a looser and looser definition for German aircraft towards the end of the war.  That G-6 was far from the first captured 109 the British had played with.  It's hard to know what was typical - it's possible that they worked perfectly in most aircraft - or it's possible that Southwood's experience is the aberration. 

 

Well I haven't heard of any other pilots on the type complain about it, and there should be no reason for them to snatch unless they're binding. 

 

One thing is for sure though, if the slats are binding and thus not operating as they should (opening unevenly/snatching etc), then turn performance will suffer a lot, which explains how the 109 came off so much worse than the 190 in terms of turning in RAF testing, the direct opposite of what German testing showed. 

 

Hans Werner Lerche, whom you qouted earlier,  also makes it quite clear that the 109 is a better turner than the 190 when he compared the two in his test report on the La5FN. So I think it's safe to say that the RAF test pilots were having issues due to the slats, either due to inexperience with or damage to the devices.

 

 

Edited May 28, 2020 by Panthera

[MiloMorai]

KW_1979, read some more pilot instructions in the book.

Edited May 29, 2020 by MiloMorai

[357th_KW]

18 hours ago, MiloMorai said:

KW_1979, read some more pilot instructions in the book.

 

Apparently you're referring a different book then the ones I mentioned above.  ?‍♂️

[Roland_HUNter]

On 5/27/2020 at 7:39 PM, Panthera said:

 

I only tried it near SL in both sims, but the difference is night and day. In DCS the K4 very easily outturns the P51(even in a 100 vs 25% fuel load match up) due to a combination of a higher powered lift coefficient + a much lower power loading. In IL2 the roles are oddly reversed and it feels as though the 109 is penalized with a lot of extra drag in turns (negating the power loading advantage) whilst also lacking the advantage of a higher powered Cl that the slats should provide.

 

I really believe the 109 FM in IL2 is in need of a revision, because something is definitely off.

100% agreed.
I remember(but everybody think I was crazy because sadly I not made videos about it) when in 2019 october IL_2 released a big patch with the pilot physics.
I outturned the yaks, mustang and tempest with 109. The 109 flying feeling wasn't like a brick anymore. I asked my squad members about it, it was my mind trick or what? They agreed something changed.
But after 3-4 hotfix it was bricky again.

[Panthera]

This probably deserves it's own thread though, I shouldn't really have started this discussion in this one.

[ZachariasX]

40 minutes ago, Panthera said:

This probably deserves it's own thread though, I shouldn't really have started this discussion in this one.

Slow speed performance (in this sim) of most aircraft (even the WW1 kites) deserves a closer look if reality is all we care for. The 109 is a very special case as it shows most prominently what I consider imperfect in our current FM.

 

Reagrding turn, the 109 and P-51 are about equal in wing loading and depending on configuration, also in power. They should turn the same for practical purposes.

[Panthera]

7 hours ago, ZachariasX said:

Reagrding turn, the 109 and P-51 are about equal in wing loading and depending on configuration, also in power. They should turn the same for practical purposes.

 

They really should not, and DCS has got this right.

 

The 109 enjoys more lift pr. square m of wing area (higher lift coefficient) than the Mustang, esp. in powered flight. In addition to this it has a higher aspect ratio wing, is much smaller in size and finally possesses a noticably better power to weight ratio.  It really should be night and day when it comes to turning between these two fighters.

[ZachariasX]

3 hours ago, Panthera said:

They really should not, and DCS has got this right.

I said „for practical purposes“ meaning that the respective aircraft with its configuration as well as pilot configuration will make the difference in the real world. 

 

Also, ED has to put in a lot of further work in the 109 to have this one right. The Mustang is is much more mature. But it shows that they had more access to the Mustang than the 109.

[Panthera]

On 6/4/2020 at 6:36 AM, ZachariasX said:

I said „for practical purposes“ meaning that the respective aircraft with its configuration as well as pilot configuration will make the difference in the real world. 

 

Also, ED has to put in a lot of further work in the 109 to have this one right. The Mustang is is much more mature. But it shows that they had more access to the Mustang than the 109.

 

The difference is quite significant between the two according to those who fly them, so not sure what you mean by "for practical purposes".

 

AFAIK they had access to flying examples of both aircraft, which is one of the reasons they got them flying so close to their real counterparts.

 

 

[JtD]

5 hours ago, Panthera said:

not sure what you mean by "for practical purposes"

 

He means that historically there are occasions of Mustangs outturning 109s and vice versa. Technically they were close enough in performance to allow pilot and circumstances to make the difference.

Edited June 6, 2020 by JtD

[9./JG27DefaultFace]

Well that's pretty much how it is in DCS. At high speeds and altitudes (higher Mach Numbers) the P-51 will beat the 109, but at low speeds the K-4 has the advantage. Even then if you put in some flaps in the mustang you can outturn at least 95% of people flying the 109 in DCS. A comparable fuel level helps as well, 30-40% is good, but ive done it with full wing tanks as well.

 

Same goes the other way, if you fly the K-4 well in DCS, as long as you can get the fight slow, no mustang will outturn you.

[Panthera]

3 hours ago, 9./JG27DefaultFace said:

Well that's pretty much how it is in DCS. At high speeds and altitudes (higher Mach Numbers) the P-51 will beat the 109, but at low speeds the K-4 has the advantage. Even then if you put in some flaps in the mustang you can outturn at least 95% of people flying the 109 in DCS. A comparable fuel level helps as well, 30-40% is good, but ive done it with full wing tanks as well.

 

Same goes the other way, if you fly the K-4 well in DCS, as long as you can get the fight slow, no mustang will outturn you.

 

Well in IL2 the 109K4 actually wont outturn the P-51 even at slow speeds, which is the problem, because it quite easily should be capable of doing so. Infact, power on, the K4 should be able to comfortably outturn the P-51 in both instantanous and sustained rate at all speeds up until the controls stiffen up around 500-550 km/h, which it also does in DCS.

 

7 hours ago, JtD said:

 

He means that historically there are occasions of Mustangs outturning 109s and vice versa. Technically they were close enough in performance to allow pilot and circumstances to make the difference.

 

Well a gondola equipped G6 engaging bombers at 25,000 ft will be at a disadvantage, but a clean K4 is a different beast, esp. down low where I wouldn't call it remotely close.

 

That said the pilot will always make a big difference, and by 44-45 Allied pilots were in general (safe from the few German experten left by then) much better trained.

Edited June 6, 2020 by Panthera

[Panthera]

Still no change to 109 FM I presume?

[Panthera]

Just some basic numbers to showcase just how unrealistic it is for the P-51D to be outturning the K-4 in IL2 (esp. sustained). be it 75" vs 1.8 or 1.98 ata:

 

Weight: 4,300 kg vs 3,362 kg

Engine power: 1,780 hp vs 1,775 hp (or 1,971 hp)

Power loading: 2.4 kg/hp vs 1.89 kg/hp (or 1.7 kg/hp @ 1.98 ata) 

Wing loading: 196 kg/m2 vs 209 kg/m2

Span loading: 381 kg/m vs 337 kg/m

 

The above suggests a significant advantage in sustainable turn rate for the K-4, whilst the higher powered Clmax afforded by the slats should allow it to attain a higher instantaneous rate as well below the speeds where the stick forces become excessive.

 

Hence why the disparity is so large in DCS.

 

Now I have a hunch that the reason the 109 in IL2 is underperforming in this respect might be due to 777 assuming that the slats add extra drag in the turn, where'as in reality they don't.  

Edited August 7, 2020 by Panthera

[ZachariasX]

20 minutes ago, Panthera said:

The above suggests a significant advantage in sustainable turn rate for the K-4, whilst the higher powered Clmax afforded by the slats should allow it to attain a higher instantaneous rate as well below the speeds where the stick forces become excessive.

 

Not so easy. First of all, during the sustained turn, you are power limited, not lift limited. Drag during the turn is for the largest part induced drag. You can see that in your spec list the Mustang has even a slightly lower wing loading than the K4. It has also less drag in general, as it is considerably faster per similar engine power. It can by all means be assumed that the Mustang has a far more efficient airframe.*) Weight alone doesn‘t tell you much about airspeed or turn times.

 

The Mustang has a tad less power, but it compensates it by less drag when lightly loaded. The configuration you posed result in almost identical turn times.

 

As the Mustang has very harmonized and effective controls, I‘d doubt that you‘d lose anything on instantaeous maneuvers, unless you fly way too slow.

 

“The other 109“ is, if anything, is too good; especially regarding the real world build quality of those kites. The Mustang with the same fuel loadout as the K4 performs very closely to the K4, slightly less on a prop hang climb.

 

 

*) This is why it has almost no competition in todays air races. Much of the courses are flown at high g‘s and you‘d never get a 109 in any version as fast, same as it is pointless to have a try with a Spitfire, even tuned Griffon ones. You either have a Mustang or a far more powerful aircraft (Bearcat/Sea Fury) as a base to compete.

[Aurora_Stealth]

The statement that the Mustang can be assumed to be a far more efficient airframe in general is a very misleading statement.The construction of the Bf 109 airframe and fuselage for example is far smaller, lighter and more efficient from a manufacturing and engineering standpoint with several advantages to its performance, deployment and maintainability in the field which is important for operational readiness. The US could rely on its better logistics to often make up those differences. Do you mean the airframe being more aerodynamically efficient? well the P-51 is still a considerably larger and heavier airframe, but it is more aerodynamic per square feet due to its low drag frontal profile and thin low drag wings (which also provide much less lift).

 

The Bf 109 K-4 still has a superior power to weight ratio at most altitudes below around 7km and produces more lift that the Mustang can rely upon, so it retains energy much better in maneuvering; which is helped further by the slats and it can also sustain that WEP for 10 minute bursts rather than 5 for the Mustang.

 

Higher weight means higher wing loading, and in almost all cases the P-51 weighs more due to its much larger airframe and significant armament weight so to overcome this you need more lift or you have a greater turn radius. The P-51 provides less lift due to its wing design, but it also has a much higher stall speed and quite vicious stall characteristics due to those thin low profile wings which limits how much you can push the aircraft around and how slow you can get without stalling.

 

Wing loading is an important factor, but it is not the only one as proven in the Bf 109 vs Spitfire turning contest which often ended up being down to the pilots G tolerance, their familiarity with the aircraft and the aircraft's prior energy state. While the USAAF used G-Suit's which helped a lot, the Bf 109 does have a very flat seat angle which helps the pilot counter G forces.

 

The Mustang is certainly very good at high speeds where that low drag plays a crucial part in its performance but the same reputation does not exist for it at lower speeds below 300mph even with low fuel loads. To make life worse, its not a particularly well harmonised aircraft in terms of stick forces, varying greatly at different speeds between being fairly heavily (somewhat like the Bf 109) and then becoming excessively light (causing the potential for a harsh stall if not treated lightly).

 

I posted a video recently from a pilot who is very experienced with flying both the Bf 109 G and Buchon in several iterations (yes its not a K-4 but still useful for comparison) and also the P-51 C and D, it makes for interesting comparisons regarding their relative qualities. The Mustang does not have a great reputation as a turning and burning aircraft on the warbird scene when put against its european contemporaries. If anything, the K-4 with its additional excess power should be very similar to the G model and its tall tail and aileron balancing should help it deal better with stick forces and keep in check that engine torque.

 

 

Edited August 7, 2020 by Aurora_Stealth

[ZachariasX]

6 hours ago, Aurora_Stealth said:

Do you mean the airframe being more aerodynamically efficient?

Yes. And it is.

 

6 hours ago, Aurora_Stealth said:

well the P-51 is still a considerably larger and heavier airframe

The Mustang has about twice the wetted area of the 109, yet it is faster at equal power applied. It is not a bit more efficient. This makes it far more aerodynamically efficient.

 

6 hours ago, Aurora_Stealth said:

The Bf 109 K-4 still has a superior power to weight ratio at most altitudes

You are aware that you can put almost the dry weight of a 109 on a Mustang and send it in missions?

 

Besides, that helps you more in climb and accelleration, not so much in turn and speed, where often other factors are king.

 

 

 

6 hours ago, Aurora_Stealth said:

Wing loading is an important factor, but it is not the only one as proven in the Bf 109 vs Spitfire turning contest which often ended up being down to the pilots G tolerance,

In sustained turn times, it is not an issue of g tolerance. That is what I was talking about and Pantheras gripe.

 

6 hours ago, Aurora_Stealth said:

I posted a video recently from a pilot who is very experienced with flying both the Bf 109 G and Buchon

Nobody today is taking these aircraft to the edge, today, neither in maneuvering, nor in loading them or using max. power. See such comments under these realities.

 

The Buchon is certainly a fun aircraft to fly... without guns and ammo... and armor... at 400 km/h. That it where it flies really well. You can have fun for one hour. And then you gotta stretch your legs. While tipping up the fuel tank up again.

 

The Mustang just turns as good as any 109 it might face if fuel is about equal as in the German plane. That is all I‘m saying. The pilot that can ride the edge of the enveloppe will win that contest.

 

6 hours ago, Aurora_Stealth said:

The P-51 provides less lift due to its wing design,

I said sustained turn. There, you are not lift limited, but power limited. Understand that. Hence both aircraft have all the lift they need. So no.

 

Taking you literally puts you wrong as well. The Mustang has a larger wing than the 109. At lower Clmax (and lower AoA) it can produce the same lift as the smaller wing going at higher AoA. If the wing is 30% larger, it can have 30% less Clmax for getting the same net lift.

 

In sum, both aircraft perform very much alike. It‘s just that the Mustang not only has the better mileage, larger gas tank, can carry far more weapons (like twice) and has far better creature comfort for the pilot. Also, taking off in a Mustang is not the same kind of adventure as in the 109.

Edited August 7, 2020 by ZachariasX

[Cpt_Siddy]

Why are y'all arguing when we have powerful computers and adequate fluid dynamic simulations to figure all these questions out computationally....

 

Anime weebs have settled the most important questions with simulations, you simmers are losing to weebs...

Edited August 7, 2020 by Cpt_Siddy

[Panthera]

 

10 hours ago, ZachariasX said:

Not so easy. First of all, during the sustained turn, you are power limited, not lift limited. Drag during the turn is for the largest part induced drag. You can see that in your spec list the Mustang has even a slightly lower wing loading than the K4. It has also less drag in general, as it is considerably faster per similar engine power. It can by all means be assumed that the Mustang has a far more efficient airframe.*) Weight alone doesn‘t tell you much about airspeed or turn times.

 

If only you realized how many times you contradicted yourself right there.

 

As stated in a turn the majority of the drag is lift induced (we're talking over 95%), which in turn is directly related to span loading. Hence whilst the P-51's cleaner airframe & shaper airfoil results in a lower Cd0, this doesn't really matter in a turn, as here lift induced drag is the primary source of drag.  As such the P-51's lower Cd0 only really benefits its level speed, hence why it is able to go faster in a straight line at the same HP than a 109 or Spitfire, but it won't outturn either.

 

Bf-109 Cd0 = 0.0223 (probably lower for the K4)

P-51 Cd0 = 0.0161

 

Drag equation:

Cd = Cd0 + Cl^2 / ( pi * Ar * e)

D = .5 * Cd * r * V^2 * A

 

I hope this clears up the confusion and you now see why power & span loading are so important to sustained turn performance, whilst Cd0 is not.  Ergo the K-4's substantial advantages here (21% & 12% respectively) is going to show, and be far more important to sustained turn capability than a 6% difference in W/L.

 

10 hours ago, ZachariasX said:

The Mustang has a tad less power, but it compensates it by less drag when lightly loaded. The configuration you posed result in almost identical turn times.

 

That it most certainly does not, the difference is infact very significant, which you should've even been able to predict based solely on the basic figures provided above.

 

I suggest that, if you can, then do the calculations. Then you'll see why the difference is so big in reality, and why they fly so differently between IL2 & DCS.

 

Edited August 8, 2020 by Panthera

[-=PHX=-SuperEtendard]

The G-14 seems to be a better turner than the K-4 and slightly better than the P-51, I wonder if getting the K-4 weight to G-14 levels would improve it's situation, other than that I guess the difference could lie in the propeller characteristics. For example the F-4 feels much better than the F-2 even at similar power levels (even while the F-2 is much lighter) and I think it has to do with the prop.

[Panthera]

4 minutes ago, -=PHX=-SuperEtendard said:

The G-14 seems to be a better turner than the K-4 and slightly better than the P-51, I wonder if getting the K-4 weight to G-14 levels would improve it's situation, other than that I guess the difference could lie in the propeller characteristics. For example the F-4 feels much better than the F-2 even at similar power levels (even while the F-2 is much lighter) and I think it has to do with the prop.

 

Lowering the weight will ofcourse always help, as it reduces the lift (and thus drag), needed to sustain a certain turn. However at the weights listed above, which is full fuel for the K4 and I believe around 70-75% for the P-51, the K-4 in reality would easily outturn the Mustang in a sustained turning contest, and it does in DCS as well.  

 

In terms of instantaneous turn performance, here wing loading coupled with Clmax becomes more important, and lightly loaded it is concievable the P-51 could get close to the K4 here, but I don't see it beating it as the Clmax of the 109 in the power on condition is going to be quite high thanks to the slats allowing the outboard part of the wing to match the energized (thanks to propwash) root section. 

[-=PHX=-SuperEtendard]

I meant as comparing G-14 vs K-4 at the same weight and very similar power (50 PS difference for 1.8 ata), if there is a significant difference between them I would attribute that to the propeller, seems the only thing left that could explain the difference I guess. There we could check how the propeller is supposed to behave and relay that to the devs, but I don't know much about that stuff.

[Panthera]

12 minutes ago, -=PHX=-SuperEtendard said:

I meant as comparing G-14 vs K-4 at the same weight and very similar power (50 PS difference for 1.8 ata), if there is a significant difference between them I would attribute that to the propeller, seems the only thing left that could explain the difference I guess. There we could check how the propeller is supposed to behave and relay that to the devs, but I don't know much about that stuff.

 

I'm pretty sure the K-4 & G-14 used the same propeller, the K-4 never being fitted with the experimental Dünnblatt meant for better high altitude & level speed performance.

Edited August 7, 2020 by Panthera

[-=PHX=-SuperEtendard]

5 hours ago, Panthera said:

I'm pretty sure the K-4 & G-14 used the same propeller, the K-4 never being fitted with the experimental Dünnblatt meant for better high altitude & level speed performance.

Looks like the DB 605D and DB 605 AS engined 109s had the wider VDM 9-12159, while the regular G-14 with the 605AM engine kept the earlier propeller used in the previous 109G models (VDM 9-12087?)

At least in game they have visually different propellers (G-14 left, K-4 right , both at 12:30 pitch).



Also just a small correction the Mustang does 75" with 150 octane mod, so the power at sea level would be roughly 1860 HP,  the power to weight advantage still goes to the 109 though.

Edited August 8, 2020 by -=PHX=-SuperEtendard

[ZachariasX]

3 hours ago, Panthera said:

(math & numbers)

...and what are the turn times then?

 

3 hours ago, Panthera said:

Ergo the K-4's substantial advantages here (21% & 12% respectively) is going to show, and be far more important to sustained turn capability than a 6% difference in W/L.

Going to show, like how? 5 seconds better turn? 20 sec vs 25? What is „very significant“ to you?

 

3 hours ago, Panthera said:

I hope this clears up the confusion and you now see why power & span loading are so important to sustained turn performance, whilst Cd0 is not. 

Well, that would depend on the spped, would it. I am aware of span loading, but thank you for listing it here. Still I am not sure how much you want the 109 „be better“. Just the DCS way and then you are happy?

 

3 hours ago, Panthera said:

which is full fuel for the K4 and I believe around 70-75% for the P-51, the K-4

That is about twice the fuel of the 109 (or more, depending on how you‘re counting).

 

 

 

[Panthera]

3 hours ago, ZachariasX said:

Going to show, like how? 5 seconds better turn? 20 sec vs 25? What is „very significant“ to you?

 

That would be two different worlds almost in my book.  We're talking in the range of 18.5-19 vs 21-21.5 sec. To me this is "significant" as in very noticable in combat.

 

At the same fuel load the difference would obviously be smaller, cutting about a second off the Mustangs time, which is still a noticable difference, as you see it in DCS.

 

3 hours ago, ZachariasX said:

Well, that would depend on the spped, would it. I am aware of span loading, but thank you for listing it here. Still I am not sure how much you want the 109 „be better“. Just the DCS way and then you are happy?

 

I believe the DCS K-4 & P-51 FMs to be basically spot on (in the air), so the answer to that question would have to be a yes. Their aerodynamic modelling is very impressive.

 

5 hours ago, -=PHX=-SuperEtendard said:

Looks like the DB 605D and DB 605 AS engined 109s had the wider VDM 9-12159, while the regular G-14 with the 605AM engine kept the earlier propeller used in the previous 109G models (VDM 9-12087?)

At least in game they have visually different propellers (G-14 left, K-4 right , both at 12:30 pitch).

 

Perhaps the G14 flew with both between different engine versions? I'm not sure.

 

That said I don't see it having a noticable impact on the turn performance, here the 100 kg lighter weight of the G14 would be more impactful.

[ZachariasX]

3 hours ago, Panthera said:

That would be two different worlds almost in my book.  We're talking in the range of 18.5-19 vs 21-21.5 sec. To me this is "significant" as in very noticable in combat.

Ah, I see we are indeed on the same page here then.

 

I just don’t think that to be significant, as the faster the differences are even less. Hence I took a little different meaning from your statement. And I should think a P-51 pilot should mind his speed in a fight, for sure.

 

If it came to near stall turn fighting, the 109 is probably the best (minus some Japanese makes), the Spitfire just being the better selection as you can fly slower without excessive drag penalty due to significantly lower wing loading at nearly the same weight. 

 

Other than that, I just don‘t think the average late war 109 didn‘t hit product soecs due to well documented manufacturing issues. But this is like, just my opinion, man. But it would be probably something that factors in on Mustang pilots facing 109‘s.

[Aurora_Stealth]

4 hours ago, ZachariasX said:

Ah, I see we are indeed on the same page here then.

 

I just don’t think that to be significant, as the faster the differences are even less. Hence I took a little different meaning from your statement. And I should think a P-51 pilot should mind his speed in a fight, for sure.

 

If it came to near stall turn fighting, the 109 is probably the best (minus some Japanese makes), the Spitfire just being the better selection as you can fly slower without excessive drag penalty due to significantly lower wing loading at nearly the same weight. 

 

Other than that, I just don‘t think the average late war 109 didn‘t hit product soecs due to well documented manufacturing issues. But this is like, just my opinion, man. But it would be probably something that factors in on Mustang pilots facing 109‘s.

 

Completely agree with you ZachariasX, its mentioned by pilots universally (including from the USAAF during WW2) that provided you keep your speed up (ideally above 300mph) and avoid energy intensive manoeuvres around that speed - the P-51 has the advantage including in agility. The problem is if you are caught in a low energy state then your options become thin very quickly and you can't rely on low speed manoeuvrability to get you out of trouble - add to that the Bf 109 can keep up with you in a climb or dive and you see the danger here.

 

Of course, we're not saying things are miles apart (we're talking a second or so of difference) but its disadvantageous enough that you wouldn't want to risk this situation in a close one-on-one as every second will count here. Because pilots flew together with wingmen, you can find plenty of exceptions or situations where they offset this disadvantage through teamwork and coordination. However its risky enough that most of the top P-51 pilots specifically mention it and describe close calls where they got a bit too slow for comfort.

 

 

Absolutely right, if we replicated 1944 - 1945 manufacturing issues with the Bf 109 or any other Luftwaffe aircraft we would almost certainly see some of them develop faults or under perform in some way that we don't see in-game... although some factories were better than others and some batches better than others in terms of quality. But I think you understand how unpopular that would be, and the game would be adding factors that are not directly influenced by the aircraft or pilot which would be deemed as muddying the water for people who want an equal opportunity to compete.

 

Just a quick one regarding the propellers, seems the standard G-14 had one variant of propeller and then G14/AS and later (incl. K-4) used another type to assist at high altitudes:

 

Quote

 

 

Cheers,

Edited August 8, 2020 by Aurora_Stealth

[Panthera]

14 hours ago, ZachariasX said:

Ah, I see we are indeed on the same page here then.

 

I just don’t think that to be significant, as the faster the differences are even less. Hence I took a little different meaning from your statement. And I should think a P-51 pilot should mind his speed in a fight, for sure.

 

Such a difference is quite noticable in combat though. Yet in IL2 the reverse is oddly the case right now, the P-51 for some reason being better, even at very low speeds, which is an error.

 

14 hours ago, ZachariasX said:

If it came to near stall turn fighting, the 109 is probably the best (minus some Japanese makes), the Spitfire just being the better selection as you can fly slower without excessive drag penalty due to significantly lower wing loading at nearly the same weight. 

 

It's between 250-400 km/h, so normal dogfighting speeds, where the K-4 enjoys a noticable advantage, about a 1.5 sec turn time advantage at same fuel load. It's esp. noticable since the 109 climbs & accelerates so much faster at these speeds as well, hence it will regain energy very fast should you decide to trade some speed for angles.

 

Now if we're talking high speed, 550+ km/h, then the high stick forces in the 109 will be limiting factor ofcourse. Interestingly though, many pilots claim the P-51 has similar stick forces in pitch as the 109, so I think you'd have to go very fast for the P-51 to get advantage here, but that's something only Skip Holm or Dave Southwood would be able to properly answer.

 

As for the Spitfire, if we're talking the beast of an airplane that is the Mk.XIV, it's got nearly the same span & power loading as the K-4 and a noticably lower wing loading on top, so obviously it will be the better turn fighter. The K-4 might be able to briefly match it in a stall fight thanks to the high overall Clmax allowed by the slats in the power on condition, but it would soon fall behind due to the extra induced drag that comes with such a high Cl.

Edited August 9, 2020 by Panthera

[SAS_Storebror]

On 5/26/2020 at 3:40 PM, 216th_LuseKofte said:

Now there is a discussion on these planes FM on Facebook. 
They use words as nerfed and its likes.

Sounds a bit odd.

If it was the Mustang only, I would chalk it on exaggerated expectations caused by the endless anecdotal accounts of "the plane that won the war" which, in some simple minds' language, translates to "the plane that beats each and everything". This has been causing fruitless debates before and probably always will.

The Tempest however...

Let me quote @SAS_Skylla's words about it: "If you die in a Tempest, you wanted to die."

That's pretty much about how that plane feels to me too, albeit I've managed to die without wanting to in it already 

 

Mike

[ZachariasX]

6 hours ago, Panthera said:

Such a difference is quite noticable in combat though.

Well that would go in the direction of noticeable:

6 hours ago, Panthera said:

where the K-4 enjoys a noticable advantage, about a 1.5 sec turn time advantage at same fuel load.

You shouldn‘t say stuff like this without backing it up with facts. Your assumptions go nowhere near of substantiating such statements.

 

If you were to go in asking for specific turn times, the lest you could do is do the whole math and don’t stop at „slats“. Here, somebody tried to make some doghouse plots, but Mustang vs 109G at altitude:

https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=2218&context=gradschool_theses

 

I‘m not that fond of the paper, but if you are to make preposterous claims about an aircraft, do it like the author did and better do the whole math.

 

Many take the slats as the „electrolytes“ of aircraft, so stopping there with your math really doesn‘t help making your point.

 

Besides, the Americans had a different opinion about the 109 than you do:

It is very light on all controls below 400 KPH but the turning radius is poor compared to our fighters. At high speed the controls become very heavy. The airplane is stable and should be a good gun platform but the vision is very poor under all conditions.

The K4 is not that different in general control layout. Did the pilot not know how to fly the aircraft and make everything wrong? If everything was as as I understand you explaining it, then the main difference would be just that the Gustav is a bit slower (yes, more seconds) in the turn than the K4, yet he should be able to fly similarly tight circles that you are speculating about.

 

Do you think the slats deploy in a steady state fastest turn scenario? Especially when reading the above conclusion of an American? The deploy around 240 km/h level flight. At what speed do you have your fastest turn at how many g?

 

Also, once you reach the AoA where the outer slatted section reaches its Clmax, what does that mean for the inner, non-slatted section of the wing?

 

Why do you think Willy put slats on the 109? For what?

 

If those „Hail Mary“ devices produce this OMG so superior „t&b“ qualities, why were they hardly put on British or American designs? I mean they were shooting thousands of 109‘s, so I tend to believe that they got some good idea about those crates. As posted above, they even flew the 109. Last but not least, Kurt Tank didn‘t use them either.

[Panthera]

That paper has a lot of figures wrong ZachariasX, he doesn't even list the Clmax figures he used.

 

The following fallacies really stuck out:

1. Incorrect stall speed for the 109G (It's below 95 mph, not 112 mph)

2. Incorrect AR for P-51 & P-47 (you can calculate this yourself: span^2 / wing area)

3. Incorrect engine HP for the 109 & 190

4. Incorrect drag areas

 

With so many incorrect base figures it's impossible to get an accurate result.

 

That said with those figures he actually has the 109G6 outperforming the P-51 pretty substantially in sustained turn rate (which he oddly describes as "yaw rate"), and at 25,000 ft no less.  

 

Quote

You shouldn‘t say stuff like this without backing it up with facts. Your assumptions go nowhere near of substantiating such statements.

 

Well if we're to keep it simple we can start by calculating approx how much thrust either aircraft would need to maintain a certain load factor (G) / turn rate at a specific speed and the same fuel load.

 

Let's say 3 G at 350 km/h,  sea level:

 

K-4

Lift required = 98,907 newtons 

Cl required: Cl*((1.225*97.22^2)/2)*16.15 = 98,907  (Cl = 1.057)

Cd0 = 0.0213

Cdi @ Cl 1.057 = (Cl^2) / (pi * 6.09 * 0.85) = 0.0688

Cd = 0.0213 + 0.0688 = 0.0901

Total thrust required:

Cd * A * .5 * r * V^2 = 8,423.9 newtons = 858 kgf

 

P-51

Lift required = 119,827 newtons
Cl required: Cl*((1.225*97.22^2)/2)*21.83 = 119,827 (Cl = 0.948)
Cd0 = 0.0161
Cdi @ Cl 0.948 = (Cl^2) / (pi * 5.82 * 0.85) = 0.0578
Cd = 0.0161 + 0.0578 = 0.0739
Total thrust required:
0.0739*21.83*0.5*1.225*97.22^2 = 9,339.3 newtons = 952 kgf
 

In summary, compared with the K-4 the P-51 needs about 11% more power to sustain 3 G's @ 350 km/h if we assume an identical fuel level of 400 liters for both.

 

3 hours ago, ZachariasX said:

Do you think the slats deploy in a steady state fastest turn scenario? Especially when reading the above conclusion of an American? The deploy around 240 km/h level flight. At what speed do you have your fastest turn at how many g?

 

The slats are AoA dependant devices, hence they start to come out as the stagnation point moves lower on the leading edge of the wing as AoA increases. As a result in a max rate turn, that is max instantaneous rate, the slats are out the whole time. In a sustained turn they may be fully or partially out, or even in, depending on the speed and resulting AoA required to maintain a specific turn rate / bank angle.

 

3 hours ago, ZachariasX said:

so, once you reach the AoA where the outer slatted section reaches its Clmax, what does that mean for the inner, non-slatted section of the wing?

 

This depends on wether we're talking a power on or power off condition.

 

In a power on condition it means that the outer  section is now able to match the inner section, which is already energized by prop wash, in Clmax. The result is a significant increase to the overall Clmax of the wing. 

 

In a power off condition it means that the outer section is able to substantially exceed the Clmax of the inner section, preventing a tip stall and providing full aileron control up to and in the stall, which in this case results in the aircraft sinking instead of dropping a wing - as you see described by pilots flying the 109  on landing approach. 

 

Aircraft without slats instead usually employ 'wash out', which is a term used to describe a downward twisting of the outer wing section, resulting in a lower AoA compared with the inner section, allowing the outer section to keep flying for longer and providing controllability near the stall. The down side to this is that you don't get an increase in the lift the outer section is capable of producing, the upside is that it's simple with no mechanical parts susceptible to failure.

 

3 hours ago, ZachariasX said:

If those „Hail Mary“ devices produce this OMG so superior „t&b“ qualities, why were they hardly put on British or American designs? I mean they were shooting thousands of 109‘s, so I tend to believe that they got some good idea about those crates. As posted above, they even flew the 109. Last but not least, Kurt Tank didn‘t use them either.

 

Mainly due to weight & complexity, and the fact that the big Allied aircraft companies simply hadn't experimented as much with these devices on fighters as the Germans (& later Russians) had at that point. That said post war this quickly changed and slats have been prominent amongst fighter designs ever since.

 

Edited August 9, 2020 by Panthera