P-51D maneuvrability - what it was in reality ...

[Juha]

Hello Kurfürst
Now Raunio reads the test so that at 600km/h (TAS) full roll took 7 sec. And looking page 12, Abb. 5, even 9 deg. line transformed from solid (gemessen/measured ) to dashed (extrapoliert) at little over 500km/h, and I'm not sure if the speed figure is compression corrected.

Now it's true that the tests didn't study roll rate itself and that 109G's wing was a bit stiffer, so we cannot read too much from the test. And of course a more muscular pilot might have been able to use a bit more force to turn the stick but still IMHO the tests indicated problems in Bf 109's ability at high speed roll.

Juha

 

[Hop]

The 109 roll rate stuff is discussed Aces High BB - DVL data on Bf 109 roll rates

On page 3 someone has posted the NACA 868 roll rate graph with the Bf 109 data overlayed. What's interesting is that at 400 mph and 50 lbs stick force, the 109 has a lower roll rate than any of the other aircraft listed, worse even than the Zero.

Tough question as they're so close.

What do you base this on?

 

[Soren]

What do you base this on?

Some of the very basic and some of the complex aerodynamics on this earth - and I will be happy to demonstrate this for you.

Now what do you base your question on Hop ? curiosity or disbelief ?

 

[Soren]

I would just like to add a few things, first about that turn-rate chart, it's a nice piece of info, but I found some contradiction looking at separate ADFU trials. For example look at this, MustangIII vs unknown FW190A:

Maybe it's just me but words like "not much to choose" or "slightly better", especially when used against a captured airplane in unknown condition don't sound too superiour do they?

As for combat reports, they are as all pilot stories of anegdotal value only, the guy that survived the fight had to out-something the guy that did not.
Note that I'm not saying that P51 was POS, far from it, but it wasn't a wonder weapon either believe it or not 8)

Yes Brain and the Fw-190 in question is infact a G-2 fighter-bomber.

Here's a pictrure of the a/c in question:

 

[Soundbreaker Welch?]

And Welchy, u'd have to go pretty far for me to ban u, as I think u have something to add to this place

Well, Thanks les. Yes, I do add polls to the forum!


Here's a soviet test video of the 190, but it's all in Russian so I can't understand the commentary. I do think the music sounds rather happy, considering this is an enemy plane the Soviets don't have!


View: https://www.youtube.com/watch?v=qayREUJe65w

 

[Hop]

Disbelief. I'd like to see the maths that suggest the TA 152 will out turn a Spitfire XIV, except possibly over a very narrow altitude range, or at extreme altitude. I haven't actually checked the figures myself, so anything's possible, I just find the idea unlikely.

 

[Kurfürst]

On page 3 someone has posted the NACA 868 roll rate graph with the Bf 109 data overlayed. What's interesting is that at 400 mph and 50 lbs stick force, the 109 has a lower roll rate than any of the other aircraft listed, worse even than the Zero.

Facts vs. Hop, as usual...

Errate : the '30 lbs' blue line label is for 50 lbs for the 109.

It should be noted that the Spitfire roll rate figures come from RAE, nder totally unknown circumstances. They contradict all other sources regarding both roll rate and characteristics. Ie. AVIA 6/10126 :

NACA trials showed the following for the Spitfire :


"Measurements of the flying qualities of a Supermarine Sptitife VA airplane." NACA Advanced Confidental Report, by William H. Phillips and Joseph R. Vensel.

The tests were conducted at Langley field, Va., during the period from December 30, 1941 to January 29, 1942. Sixteen flights and apprx. 18 hours flying time were required to complete the tests.

[...]

Desription of the the Supermarine Spitfire airplane

Name and Type : Supermarine Spitfire VA (Air Mininstry No. W3119).
Engine : R-R Merlin XLV
Weight, empty : 4960 lbs
Normal gross weight : 6237 lbs
Weight as flown for tests : 6184 lbs

Ailerons (metal-covered)
Lenght (each) : 6 feet, 10 1/2 inches
Area (total area, each) : 9.45 sq. feet
Balance area (each) : 2.45 square feet

[...]

A stick force of 2 lbs to the right and 3 lbs to the left was required to overcome aileron friction.

[...]

Lateral Stability and Control

Aileron-control characteristics : The effectiveness of the ailerons of the Supermarine Spitfire airplane was determined by recording the rolling velocity produced by abrubtly deflecting the ailerons at various speeds. The aileron angles and stick forces were measured. It should be noted that the airplane tested was equipeed with metal covered ailerons.

[...]

The ailerons were sufficiently effective at low speeds, and were relatively light at small deflections in high speed flight. The forces required to obtain high rolling velocities in high-speed flight were considered excessive.
With a stick force of 30 lbs, full deflection of the ailerons could be obtained at speeds lower than 110 miles per hour. A value of pb/2V of 0.09 radian in left rolls and 0.08 radian in right rolls were obtained with full deflection.

Rolling velocity (at 6000 ft altitude) of about 59 degrees per second could be obtained with 30 lbs stick force at 230 miles per hour indicated speed.

The ailerons were relatively light for small deflections, but the slope of the curve of stick force against deflection increased progressively with deflection, so that about five times as much force was required to fully deflect the ailerons as was needed to reach one-half of the maximum travel. The effectiveness of the ailerons increased almost linearly with deflection all the way up to maximum position. The value of pb/2V obtained for a given ailerons deflection was nearly the same in speeds and conditions tested. It may be concluded, therefore, that there was very little reduction in aileron effectiveness either by separation of flow near minimum speeds or by wing twist at high speed.

Fig 27 shows the aileron deflection, stick force, and helix angle obtained in a series of roll at various speeds intended to represent the maximum rolling velocity that could be readily obtained.

The pilot was able to exert a maximum of about 40 lbs on the stick. With this force, full deflection could be attained only up to about 130 miles per hour. Beyond this speed, the rapid increase in stick force near maximum deflection prevented full motion of the control stick. Only one-half of the available deflection was reached with a 40 lbs stick force at 300 miles per hour, with the result that the pb/2V obtainable at this speed was reduced to 0.04 radian, or one-half that reached at low speeds.

 

[Soren]

Disbelief.

I thought so.

I'd like to see the maths that suggest the TA 152 will out turn a Spitfire XIV, except possibly over a very narrow altitude range, or at extreme altitude. I haven't actually checked the figures myself, so anything's possible, I just find the idea unlikely.

Sure, lets say the matchup is at SL, I'll even provide the basic figures.

We'll assume a CLmax of around 1.45 for the Ta-152 as CLmax is going to increase slightly with AR. The Spitfire's CLmax is going to be 1.35 - Any objections ?. As to 'e' (Oswald efficiency factor), well I'm guessing the Spitfire's to be abit higher despite the aerodynamic twist of the wing.

The basic figures

Ta-152H CLmax: 1.45 (This is a low educated guess, it might be higher)
Ta-152H 'e': 0.8
Spitfire Mk.XIV CLmax: 1.35
Spitfire Mk.XIV 'e': 0.83

Cd0 is unknown for the Ta-152H so therefore total drag will be represented by the Cdi. (And don't worry, the Cd0 isn't a decisive figure)

Height: Sea Level
Temperature: 15 C
Pressure: 101325 Pascals
Atmosphere: 1.164 Kg/m^3
Speed of sound: 349 m/s

Speed is going to be 600 km/h, the absolute higest speed for both a/c at SL.

Ta-152H-1 Aerodynamics at SL

Lift:

L = 1.45*23.3*.5*1.164*600^2 = 7078633.2

Drag:

Cdi = (1.45^2)/(pi*8.94*.80) = 0.0935747393
Cd0 = -Unknown-

D = 0.0935747393*23.3*.5*1.164*600^2 = 456814.66

L/D ratio = 15.49
L/W ratio = 1487

Spitfire Mk.XIV Aerodynamics at SL

Lift:

L = 1.35*22.48*.5*1.164*600^2 = 6358512.96

Drag:

Cdi = (1.35^2)/(pi*5.61*.83) = 0.124588142
Cd0 = -Not included-

D = 0.124588142*22.48*.5*1.164*600^2 = 586811.345

L/D ratio = 10.83
L/W ratio = 1651
_______________________________

Ta-152 H-1 L/D = 15.49
Spitfire Mk.XIV L/D = 10.83

Ta-152 H-1 L/W = 1487
Spitfire Mk.XIV L/W = 1651

Thats an extra 43% of lift pr. amount of drag for the Ta-152 H-1 and an extra 11% of lift pr. weight unit for the Spitfire XIV. This indicates that the sustained turn rate of the Ta-152 H-1 is higher than the Spitfire MK.XIV's, while the Spitfire Mk.XIV's instanious turn rate is higher than the Ta-152 H-1's.

And this is at high speed and at SL mind you - for the Spittie's sake lets not go higher

 

[Soundbreaker Welch?]

Well, the big Griffon engine wasn't well liked anyway, except for high altitude flying, which was a good thing. Now Spitfire XVI had the same frame as the Spit XIV, excpet it was a low altitude Spitfire with a Merlin engine. I imagine it's turn rate was better than the Spitfire XIV.

 

[Hop]

What's interesting is that at 400 mph and 50 lbs stick force, the 109 has a lower roll rate than any of the other aircraft listed, worse even than the Zero.
Facts vs. Hop, as usual...

Um, Kurfurst, you've reposted the chart that shows exactly what I said. Apart from the Spitfire at 30 lbs stick force that you've drawn in, that is.

NACA 868 shows roll rates at 50 lbs stick force for all aircraft apart from the Zero, where the force limits are unknown. The 50 lbs line for the 109 falls below all the other aircraft I can see.

It should be noted that the Spitfire roll rate figures come from RAE, nder totally unknown circumstances.

No, as we have been over ad nauseum, they are tested results for the Spitfire V, given along with the Mustang and Typhoon figures by the RAE as a comparison with the Fw 190.

NACA trials showed the following for the Spitfire :

Four problems with the Naca roll figures for the Spitfire.

First, it was a very worn aircraft. Robert Standford Tuck:

It happened that Wright Field had the only Spitfire in America-a Mark V. Unfortunately almost every pilot in the Air Corps had had a go on her and like a car that had too many drivers, she was the worse for wear...'She was very tired, very sloppy-she'd had the guts caned out of her all right.

Second, it was a Spitfire Va. That's the last of the machine gun armed variants, and so didn't have the wing strengthening applied to the cannon armed aircraft. Va's also came from the factory with fabric ailerons, so we don't even know if the "metal ailerons" fitted were the standard production items.

Third, Naca published the report containing the 868 graph post war. They chose to use the RAE's figures for the Spitfire, rather than their own.

Fourth, the RAE tested the roll rates of the Spitfire against other aircraft. We'll leave out the fact they said it rolled much better than the 109s, because you will just come out with excuses that they couldn't fly the 109 properly. But they also tested against a range of American aircraft, which they used extensively, and with manufacturers support.

Vs P-47C:

The good aileron control gives the P-47 an excellent rate of roll even at high speeds, and during mock combats it was considered to roll as well as, if not better than the Spitfire at about 30,000 feet. At lower altitudes there is nothing to choose between them.

Vs P-51B:

Although the ailerons feel light, the Mustang III cannot roll as quickly as the Spitfire IX at normal speeds.

Edit: Soren, I'll reply later in the day. I need to wake up to do maths

 

[Brain32]

Interesting thing is Hop, that whenever we discuss a Spitfire testing, if the results are bad, heck, even if the paint job from artistic POV is being discussed and criticized you dismiss those results by whatever means possible, but in the same time tests of crash-landed, shot down, 190's and 109's maintained and flown by untrained personel, you take as apsolute truth and perfect example of a service plane. Now that's just funny
Fortunetly this is not ubi forum , so I think people see that...

 

[FLYBOYJ]

Four problems with the Naca roll figures for the Spitfire.

First, it was a very worn aircraft. Robert Standford Tuck:

It happened that Wright Field had the only Spitfire in America-a Mark V. Unfortunately almost every pilot in the Air Corps had had a go on her and like a car that had too many drivers, she was the worse for wear...'She was very tired, very sloppy-she'd had the guts caned out of her all right.

Hop - I'd like to know where that came from....

Listen folks - when I hear pilots (even the greatest aces and test pilots) make statements that the aircraft is "worn out," I have to laugh. Many of these folks had little or no maintenance backgrounds and made these determinations sometimes by outward appearances and comparing one same aircraft to another. What wears an aircraft out?

1. High engine or propeller time - flying an aircraft that doesn't have high compression, leaky superchargers, or a propeller that will not hold pitch. Maybe there are other conditions (bad magnetos) worn internal engine components etc. that was causing the said engine not to meet advertised performance numbers. I doubt Wright Pat would of operated an aircraft with an engine not meeting "book performance."

2. Airframe - If the airframe has been pranged several times, beat up and if major repairs were done to the aircraft that probably knocked out the overall asymmetry of the aircraft. If an aircraft with high airframe time is properly maintained, properly rigged and never suffered any major damage, it should fly almost as good as one straight out of the factory. The only thing an aircraft in service tends to do is gain weight because of dirt finding it way into the airframe structure over time.

As many of us seen, in the back of each Pilot's notes or flight manual are performance numbers. If the aircraft meets those numbers that's the bench mark of performance. Now if there is something physically wrong with the airframe, as stated it's a whole different story and none of these expert pilots ever specifically state what the problem is. I call this a "pilot placebo."

My 2 cents....

 

[Marcel]

I've read the same text as Hop mentioned in "Fly for your Life" by Larry Forrester and when I read it I was wondering the same thing as you Flyboy. I can only imagine that the cables would wear out, hence the slugginess, but then again, you probably know more about that than I do. Would be nice to have an explanation about this.

 

[FLYBOYJ]

I've read the same text as Hop mentioned in "Fly for your Life" by Larry Forrester and when I read it I was wondering the same thing as you Flyboy. I can only imagine that the cables would wear out, hence the slugginess, but then again, you probably know more about that than I do. Would be nice to have an explanation about this.

Correct Marcel - even with control cables wearing out, they could be adjusted and eventually replaced - this is a common maintenance action. Don't get me wrong, I have the utmost respect for those who flew these aircraft during these tests but I think those who recorded pilot statements as a result of these test did not press for real explanations or were not technical enough to understand what the test pilot was talking about. In either case I take with a grain of salt when I hear someone say "the aircraft had a worn airframe" when discussing these types of comparisons...

 

[Marcel]

Yeah, I would take the whole book with a grain of salt as it only seems te be written to tell everyone what a nice chap Tuck was. Not that I dispute he could have been a good fellow, but I rather read some more objective literature.

 

[FLYBOYJ]

I guess the whole point here is "specific" things will cause an aircraft not to perform as advertised. In the case of the Spitfire Va used on the mentioned tests, its best to compare the actual aircraft's performance against what the manufacturer said the aircraft can do...

The moral of this story folks is unless the pilots say specifically what was wrong with an aircraft "that wasn't performing properly," or "was worn out," take the comment with a grain of salt..

 

[Sgt. Pappy]

Well, the big Griffon engine wasn't well liked anyway, except for high altitude flying, which was a good thing. Now Spitfire XVI had the same frame as the Spit XIV, excpet it was a low altitude Spitfire with a Merlin engine. I imagine it's turn rate was better than the Spitfire XIV.

The Spitfire XVI had the same frame as the Spitfire IX but with an American-built Packard-Merlin 266 which was practically identical in performance to the Merlin 66. This difference is the only diff that all 100% of Mk.XVI's had vs. the IX. The new variant number was applied as the two engines required different tooling. Some pilots viewed the XVI's as a bit of a 'Mk.IX reject' due to the engine failing a little more easily.

The Spitfire XIV had the same frame as the Spitfire VIII; a variant that had shorter ailerons than the Mk.IX along with extra fuel tankage in the leading edge of each inboard wing section and a strengthened airframe in addition to a retractable tailwheel. All in all, the empty Mk.VIII weighed some 182 lbs. heavier than the Mk.IX while the Mk.XIV weighed a whopping 830 lbs. heavier empty.

For the record, the wing twisting of the Spitfire (wash out effect) allowed for a more gentle/obvious stall which was good for novice pilots. The disadvantage of this feature was the roll rates at high speed. No matter what wing - regular tip or clipped, the washout badly degraded roll at high speed. Plus, it is said that no two aircraft perform exactly the same; even a dent, scratch or lodged pebble may affect performance. The best we can hope to do is get the general idea of the plane's performance and go from there.

 

[AV8]

New member here, where in hell did you get the graphs above?

Been looking for that stuff for a long time! Is it available for other aircraft?

I have been looking for just such a comparison, but, of course, the altitude makes all the difference. Superchargers and turbochargers made a huge difference in the performance of the various airframes.

Example was the P-39. WITH the turbocharger it was world beater. Without the turbo, it was a world beater below 12 to 15 thousand feet, but was miserable above that altitide.

So the Soviets kicked ass with the P-39 while WE didn't use it much unless we HAD to.

So ... where are all these performance graphs located?

I have extensive files of air kills, conflicts, and pilot names, but all are by country and name. None are by what aircraft type the pilot was flying or what aircraft was killed. Seems almost like a conspiracy of disinformation ...

Anyone HAVE these data? If so, you are the savior of all WW2 aviation fans all over the world!

PLEASE post or send an email link!

 

[Jabberwocky]

New member here, where in hell did you get the graphs above?

Been looking for that stuff for a long time! Is it available for other aircraft?

I have been looking for just such a comparison, but, of course, the altitude makes all the difference. Superchargers and turbochargers made a huge difference in the performance of the various airframes.

Example was the P-39. WITH the turbocharger it was world beater. Without the turbo, it was a world beater below 12 to 15 thousand feet, but was miserable above that altitide.

So the Soviets kicked ass with the P-39 while WE didn't use it much unless we HAD to.

So ... where are all these performance graphs located?

I have extensive files of air kills, conflicts, and pilot names, but all are by country and name. None are by what aircraft type the pilot was flying or what aircraft was killed. Seems almost like a conspiracy of disinformation ...

Anyone HAVE these data? If so, you are the savior of all WW2 aviation fans all over the world!

PLEASE post or send an email link!

All the NACA historical documents are available at the NASA archives:
NASA Technical Reports Server

Diasgree that the P-39 was a "worldbeater" with the turbosupercharger.

Fundamental problem is that, due to many reasons, the performance of the XP-39 couldn't really have been replicated on production machines (combined with the philisophy of the USAAF at the time didn't really favour high altitude interceptors).

The excellent 390 mph top speed and 5 minutes to 20,000 feet climb figures that the turbosupercharged XP-39 achieved in testing were for an unarmed, unpainted, polished prototype without any military equipment.

The XP-39 that achieved them weighed just 3,995 lbs at empty (only 200lbs heavier than an empty A6M Zero and more than 1,400lbs lighter than P-40 protoypes). If you add military equipment, like self sealing fuel tanks, military radios, antenna, armour, guns, gunsights, gun heaters, ammunition, IFF and all the other stuff necessary to make the plane a workable fighter, performance is going to take a nose dive.

Aerodynamics get messed up by airframe projections (gunports, antenna, ejector chutes, ect) and camoflage paint. The RAF found they lost 7 mph in top speed at sea-level from the its Allison engined P-51s after painting them.

Just to give an idea of how much weight creep there would be; The empty weight of the YP-39 was 5,040 lbs, up just over a 1,000 lbs from the 3,995 lbs of the XP-39. That's a weight gain of just over 25% on the empty weight AFTER stripping out the turbosupercharger.

Loaded weight shot up from 5,550 lbs for the unarmed XP-39 prototype to 7,070 lbs for the armed YP-39, and it was still without internal or cockpit armour and had no self sealing fuel tanks. When these, and more guns and ammunition were added, combat weight climbed by another 500lbs.

So, a fully loaded, combat capable P-39D circa September 1941, weighed around 7,650 lbs combat loaded, almost a full 2,100lb heavier than its turbosupercharged XP-39 ancestor. That is a weight gain of about 38%. Its empty weight was 1,400lbs higher than that of the XP-39 prototype. That increase would markedly effect handling, speed and climb performance.

Would the P-39 have been better a better fighter in the ETO and Pacific if the USAAF had left it alone? Yes, but probably not by much. It would of been marginally slower and less manouverable down low, but progressively faster above 15,000 feet. Its problems with CoG and cannon reliability would of still existed.

To turn the P-39 into a combat capable fighter it needed all that equipment. So, the weight creep, that was always going to happen, meant that the performace exhibited by the prototype wouldn't of been achievable in real life until there was a serious jump in power in the military models.

 

[Jabberwocky]

I thought so.

Sure, lets say the matchup is at SL, I'll even provide the basic figures.

We'll assume a CLmax of around 1.45 for the Ta-152 as CLmax is going to increase slightly with AR. The Spitfire's CLmax is going to be 1.35 - Any objections ?.

Raises hand

NACA L-353 reports Spitfire CL max at cruise condition (2650 rpm, 3 3/4 lbs boost), gear up, flap up, ports open, as 1.68.

What does this do to the calculations?