dimanche 11 septembre 2016

The Junkers 87 Stuka, exaggeratedly vilified, but so efficient!



Obsession of the luftwaffe deciders: Enhancing the efficiency of aerial bombing 


After the end of WW I, all officers in charge of the aerial bombing were aware of its phenomenal power.
Knowing the new hazards induced by the completely restructured map of the Europe after 1919, they worked hard to enhance the efficiency of this power.  

  • The enhancing of the destruction ability implied to increase the total mass carried in each bomber, as, also, the individual mass of the bombs
  • The lessening of the number of out-of-the-way targets implied to increase the combat radius of the bombers, their true operational ceiling as, also, their ability to fly at night or in very bad weather. That was achieved by:
    • The use of more engines, each one being more powerful than the older ones.
    • The research of aerodynamic and structural breakthrough in the wings as in the fuselage designs, which, by increasing of the flying speed, diminished the time during which the bomber was vulnerable.
    • The development of navigational and aiming devices, allowing smarter approaches of the target...
  • The reducing of the losses of bombers and of their crew when they were under enemy fire implied several methods:
    • The armoring of the pilot seat and windshield induced some supplemental weight which had an adverse effect of handling and maneuverability.
    • Flying above the ceiling of the enemy AA cannons was efficient at the cost of the accuracy of the bombing impact on the chosen targets.
    • The escort of the bombers by fighters was not an easy method, because it was not totally efficient. Nevertheless, the losses were significantly reduced and the mood of the bomber's crew was the highest possible
    • The night bombing was very efficient (until 1942) to reduce the losses of the attackers, at the cost of the accuracy.


The last way was
the radical enhancement of the bombing accuracy at the target level. To give an idea of this problem, you have to see the results of the Allied Carpet Bombing during WW II.
  • 2,700,000 metric tons of bombs were released above Germany at the cost of 40,000 bombers downed.
  • 7,500,000 German peoples became homeless. Among the 1,080,000 civilian casualties, 305,000 were killed
If you look at the following picture, you may understand how such a bombing method is not fitted to eliminate any hard target.

That was only a political terror method, at first used by Hitler & Co, but more efficient when the Allied used it.




Impact dispersion of the bombs released by a B 17 flight.
One see also how the bombs are tightly gathered when they are 100 m under their bomber.

Today, with radar imagery and laser guided bombs, the accuracy of the bombing is often better than one meter! One may destroy one chosen 4x4 vehicle only...


But, in the 30's, the radar experienced numerous teething troubles and the laser was only the subject of the fantastic universe of cartoons... 

One needed of more simple and available methods.


Some data were immediately accessible:

  • The accuracy imply both a good view of the target and a very precise aiming.
  • So, it depends of the quality of the bomb-sight.
  • A lower bombing altitude, taking into account the hazard of the exploding bombs for the bomber itself, is good for the accuracy. But it will have a completely adverse effect on the bomber crew safety facing enemy AA fire.

During a horizontal bombing, one "just released" bomb is "flying" with the same parameters than the bomber. 

Few microseconds later, it became nose heavy and will be affected by his drag, inducing a semi-parabolic trajectory ending by a quite vertical segment just before its impact on the ground (and, may be, the target).   

During this "long journey", numerous factors may affect the expected trajectory.


The dive-bombing and its "perfect" accuracy...



Some spontaneous attempt of dive bombing were experienced in most of the involved military pilots of any countries fighting during WW I.


At the end of the 20's, the dive-bombing was well developed in the US Navy. 

However, the most impressive results were achieved in Germany with the works of Junkers (Ju 47) and Ernst Udet.


After some turns, a good dive-bomber was chosen, the single engined two seater Junkers 87.

They nicknamed the Ju 87 as Stuka (short for Sturz Kampf Flugzeug = Dive Fighter Aircraft).




Junkers 87 B Stuka - The fixed undercarriage was one of the elements which slowed the dive.


In her B1 variant, in May 1940, she used a Jumo 211 engine delivering 1,000 hp for take off. 

The fuselage was 11 m long.


The wings, affecting a W layout to minimize the length of the - fixed - undercarriage, had a span of 13.5 m and a wing area of 31.9 m².


The empty weight was 2,750 kg and the take off weight - with a bomb load of 500 kg - was 4,250 kg.


So, the wing loading was 133 kg/m² with the bomb and only 117 m², once the bomb released.


The top speed was 390 km/h at 4,400 m and the service ceiling was 8,100 m.


With a 
bomb load of 500 kg, the combat radius was 500 km. 

The cruising speed was 250 km/h. 

According to W. Green (famous bombers of the Second World War, 1959, MCDonalds), more than 600 Ju 87 B1 were built during the entire 1940 year (to be compared with the 134 built the previous year). 




The accuracy was sufficiently good to gather - with trained pilots - all impacts within a circle whose radius did not exceed 50 m

The bests German pilots were able to put all their bombs with a 10 m accuracy.



The time spent from the release of the bomb to the impact on the target (or the ground ;-)) was very short (a handful of seconds), so the adverse events that might affect the trajectory of the bomb became negligible.  



Typical bombing sketch 


At first, the Stuka flew at a rather high altitude (3,000 m to 5,000 m) to be out of range of the AA fire.
  • Once the target in sight, the pilot prepared his bomber to dive vertically, using the automatic device dedicated to ensure a perfect dive.
  • During the dive, the pilot had to stabilize the trajectory of his bomber which increased fiercely her speed up to 600 kph (= 167 mps). 
  • Aiming the target with a bomb-sight rather similar to a fighter gun-sight, at about 700 m AGL, the pilot released the bomb which evaded the air-screw circle with a dedicated fork.
  • Just after the bomb release, a recovery maneuver occurred, also automatically, to avoid the ground, obviously, and to fly out of the AA fire hazard. 
  • The lowest altitude currently achieved was about 400 m AGL and the crew was submitted to a 6 g stress. 
  • Obviously, at this very moment, the pilot might chose a new heading, differing from the one used before the dive, to jam the anticipation of the AA fire gunners.
  • In May 1940, the German pilots, at the beginning of the dive, made a half-roll, in order to be in inverted flight. So, they spent less time inside the enemy lines. 

For the Allied AA gunners, the defense against dive bombers was not easy at all:
  • The medium caliber guns - theoretically able to destroy any aircraft as far as an altitude of 10,000 m - were very difficult to reload when the gun was at an angle larger than 80°. 
  • Any aircraft diving  above infantry unit trigger to each soldier the mood to be personally attacked (Capt. JM Accart, On s'est battu dans le ciel, 1941). This explaining some panic of troops not trained to such an attack!.

All the dive-bombers of 1939-1940 shared many characteristics with the actual fighters: Huge toughness (to withstand to heavy acceleration constraints), good climbing ability, good maneuverability. 

Ok, you can read, especially in the literature written by British authors, the Stuka was not maneuverable. 

How can they explain that the very first aerial victory of the WW II was a PZL 11 fighter downed by a Ju 87? (The PZL 11 C was highly maneuverable!).

This legend, as some others, was stemming from the latest anti-tank variants - Junkers 87 G - fitted with two under-wings pods, carrying a 37 mm antitank cannon weighting 300 kg each!

Nevertheless, the Ju 87 was used as a night fighter against the U2 sovietic biplanes which were used to harass the German troops at night: Such an use is a excellent testimony of the maneuverability of this aircraft.


The Ju 87 Stuka and the British criticism about ALL the dive-bombers


The Junkers 87 Stuka is, by far, the most famous dive bomber in the World.

Ok, she was used by nazi officers during the very hard fighting of the WW II triggered by Adolf Hitler, an extremely bad man.

However, an aircraft is not a human being: She did not decide who she is attacking. So, even an aircraft used for bad ideas may be a very good aircraft. 


So I cannot support some criticisms which are not logically correct.  

The Stuka was first used, very successfully, in Spain since 1937.

In August 1939, just two weeks before the outbreak of the WW II, she suffered a dreadful setback, 13 Stuka (a full squadron!) were annihilated during a military exercise in Silesia.

Obviously, that was the result of insane orders which ordered a dive bombing through clouds which were too close to the ground level: About all the Ju 87 crashed. 
{A very similar fate was experienced by a squadron of Morane 406 three weeks later, resulting in 6 fighters written off, 3 pilots killed and three wounded.}


Some days later, during the Polish Campaign, the 335 available Stuka played an overwhelming role, paralyzing the movements of the Polish units. 

Moreover the first aerial victory of all the WW II was that of a Stuka downing a PZL 11 C the September 1st, 1939.

At the end of the Winter, she was very successfully used against Allied ships during the Campaign of Norway.

During the Battle of France, 300 Ju 87 B1 were used the 3 first days against the Netherlands and Belgium but, the May 14, they were all concentrated in the Sedan zone to silent the French heavy artillery (inducing the use of carpet bombing on the Rotterdam historic center with 80 Heinkel 111). 

The Stuka played an absolutely decisive part in the German war game against France: Each French counter-offensive was decimated by pin point bombing, even more devastating than the excellent German 88 anti-tank gun.


That was amplified also by the excessive reliance of most of the French infantry officers in their 13.2 mm AA machine guns, they preferred to the 25 mm which had twice the vertical range (3,000 m instead of 1,500 m)!


Nevertheless, as usual when fighter escort was not immediately available, they suffered casualties from French fighters, as all kind of bombers encountering enemy fighters. 

That was illustrated the May 22, when 18 Dewoitine 520, gathered in two groups, attacked a complex formation of Henschel 126 and Junkers 87, downing 8 Stuka, 2 Hs 126 and even an isolated He 111, at the cost of one D 520 downed (pilot POW) and another damaged with the pilot WIA.



British authors, relentlessly since 70 years, used the same fairy tale that wrote William Green in his book 
Famous Bombers of WW II (1959) to "demonstrate" the absolute failure of the Stuka, concluding about "the debacle of the Ju 87 in the Battle of Britain" after an, at least childish, aesthetic criticism about this aircraft.


You may read now, in En Wikipedia, the September 7, 2016, the following sentence which summarize the same idea: "It was withdrawn from attacks on Britain in August after prohibitive losses, leaving the Luftwaffe without precision ground-attack aircraft."

That expression is somewhat exaggerated and historically wrong, because at this very moment, Adolphe Hitler was preparing his Barbarossa Operation (the attack of the Soviet Union) for which he need absolutely all precision attack bombers.

Yes, as all other military aircrafts, the Junkers 87 was not invincible. 

However, telling of prohibitive losses or telling of the debacle of the Ju 87 is completely wrong.  

During the Battle of Britain, according to this site, 71 Ju 87 were downed, among the 280 Stuka initially engaged. These losses represent 25% of the aircrafts after about 100 days of combats. 

So, the Göring's Luftwaffe had lost only 0.7 Stuka / day!

Obviously, as in any war, some particular days were dramatic for the Ju 87 crews, but such tragedies are in the nature of any war.

{Personal comment: On this subject, I want to remind you the Fairey Battle experienced an average of 12 downed Battle / day in just five days. 

And I never thought the Battle was a bad bomber: She was, at worst, an average bomber which suffered especially from an incredibly unprofessional Command...

But the worst losses were that of the 40,000 Allied heavy bombers downed by the Luftwaffe over Germany between 1941 and 1945. 

These losses may be translated as 10,000 bombers destroyed each year, or 27.4 bomber each day or 1.14 bomber each hour... Ouch!!!

As usual, the responsibility of such huge losses was mainly that of those, among the US generals, who excluded the most efficient escort fighter for this job, the P 51 Mustang during about 2 years, they were not proficient at all !}


To assess the Junkers 87, one may also take into account the losses these bombers had inflicted to the Allied.


During the intense but short lived Battle of Dunkirk, the Allied had lost 29 among their 40 destroyers as also 89 merchant ships. 

One may also remember that was also thousands of soldiers and crews KIA and even more of WIA.
From the other hand, the losses of Hurricane fighters during BoB were 538. I'm not sure the RAF had 2,200 Hurricane at the beginning of this event...



Sure thing! An isolated Stuka was an easy prey for a pair of modern fighters, 
but, head to head, the fighter had to rapidly down the Stuka, which, once devoid of her bomb, was simultaneously very maneuverable, tough and rather well defended.


Several Allied fighter pilots involved in BoB had told later they have been 
fiercely attacked by Junkers 87 pilots.

It's not difficult to understand that the mood of the British authors was highly correlated to the huge losses occasioned by the Junkers 87 to the Royal Navy, as if they were not aware they have won WW II!

One of the few shortcomings of the Stuka was the need of a very powerful engine to carry the 500 kg bombs.

Before 1941, to carry a 1,000 kg, it was necessary to use of a twin-engined bomber. 

This induced the ordering of the Junkers 88, which was intended to be also a Stuka.

That order may appear as irrelevant when we remind the attack of the soviet battleship Marat  (23 September 1941) by the German pilot Hans-Ulrich Rudel and his team mate Lothar Lau with the 1,000 kg bombs they carried on their Stuka
  • This case is very special, involving two exceptional pilots as, also the complete air mastering of the Luftwaffe in Soviet Union during all the second half of 1941. 
  • Moreover, it is very likely that the take off airfield used by Rudel was very close from Leningrad. 
    • The Marat had a poor armored deck (only 50 mm thick, a fossil of the Dreadnought era)... The modern battleships used at least 150 - 170 mm thick armor (200 - 230 mm for the Yamato-class).

    The real question is: Was the Ju 87 Stuka efficient from a military point of view? 
    The answer is: Yes, she was extremely efficient! 

    She was one of the major asset for all the armies she supported.

    During all the German East front battles against USSR, she pave the way to the Panzer Divizionen. 


    The defeat of the VIth Army of von Paulus at Stalingrad resulted mainly from Hitler's refusal to retreat, a decision which was enhanced by some arrogant German top officers who promised they can delivered that army... 

    During the Battle of Kursk, the Junkers 87 units were able to disrupt the encircling of 2 German armies!


    The German deciders had made a big mistake when they ordered to transform twin-engined bombers in some kind of 
    powerful Stuka. But she never achieved such a role, because a she was too heavy to be sufficiently nimble.

    That explaining why the Junkers 88 was not as fast as expected and, also, why the Heinkel 177 was never perfected.  



    When USSR achieved to build and to manage more than 3,000 really modern fighters on the battlefield, about at the Summer of 1943, the losses of the Stuka increased dramatically. 


    That was not a sign of the obsolescence of the Stuka, but the conjunction of several adverse factors:
    • The number of German well trained fighter pilots was dwindling.
    • The most numerous German fighter, by far, was the Messerschmitt 109, not the tougher Focke-Wulf 190.
    • As a consequence, the grand total of German efficient fighters exceeded rarely 3,000, against about 10,000 Allied ones. So, the bomber escort became exceptional.
    • The Germans were late to develop smart airborne anti-tank rockets, allowing a longer range fire.


    It should be, theoretically, possible to compare the efficiency of the two best dive-bombers of WW II, i.e. the excellent Douglas SBD Dauntless.

    These two bombers had very close performances, except for the total range were the Dauntless was exceptional.  

    Both were also used for strafing, the Ju 87 G using 37 mm antitank automatic cannons but it's impossible to compare the soviet tanks with the Japanese ones, whose armor was only "symbolic".

    Both were built in rather similar number (6,500 Stuka and 5,900 Dauntless, according to En Wikipedia).

    But the Dauntless was especially used against naval target whereas the Stuka was used against much more diverse targets.

    The bombing methods differed: The Stuka was used in vertical dives, whilst the Dauntless was mainly used for 60° dives. 

    I suggest these methods had an impact of the duration of the effectiveness of the dive bombers during the WW II: 
    • The ultra accurate vertical dive method, even with the help of some automatic devices, need exceptional pilots, may be 1/10 among them having the fighter pilot level.
    • The 60° dive method was usable by all pilots having the fighter pilot level.
    So, the German set of Stuka pilots became even smaller, contrarily to the set of US Dauntless pilots. 


    Conclusion 



    The dive bomber Junkers 87 was a great bomber which changed the warfare (as wrote W. Green in the last sentence of his article in Famous Bombers of WW II, p.46).

    She was perfected by Ernst Udet to a point where her use minimized really collateral casualties

    She had also a psychological impact on troops not trained to aerial warfare, as were all Allied troops.




    The laser guided weapons of today used some of the concept of the dive bombing. They enjoy of a metric accuracy. 


    Nevertheless, they are extraordinarily expensive.


    One of the readers of my French blog suggested it may be possible to create a modern dive bomber.

    Some drones may be viewed as a kind of such a bomber...

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