Hs-129 Panzerknacker

I cannot find a production cost for this aircraft but supposedly it was inexpensive. Perhaps even less expensive then a Fw-189. There are plenty of sources which claim the Hs-129 was highly effective. So why did Germany produce so few and end production during September 1944? It seems like exactly what Germany needed to defeat the hordes of Allied armored vehicles.

Hs-129 Production.
German aircraft production during World War II - Wikipedia, the free encyclopedia
221. 1942
411. 1943
302. 1944

It was another airplane that could only perform with air superiority. It's ability to defend itself was minimal. Couple that with the French built engines, slow delivery? and non-existent delivery after August of 1944 and I think we can figure out why production stopped. The Gnome-Rhone factories were in a suburb of Paris and in Limoges, about half way between Bordeaux and Orleans.

From Wikipedia, take for what you think it is worth.

"With the fall of France in 1940, Gnome et Rhône was ordered to produce the BMW 801 under license, while the 14M saw limited use on some German designs. The company became infamous for slow production, building only 8,500 engines by May 1944, when the Germans had been estimating 25,000. An air raid by Lancasters of 44 Squadron RAF completely destroyed the original Gennevilliers factories on 9/10 May. Another air raid by Lancasters of 617 Squadron led by Wing Commander Leonard Cheshire had also severely damaged the Limoges factory on 8/9 February 1944."

The Germans had no other engine that would work on the airframe. The G-R 14M being a particularly small engine just a bit over 3 feet in diameter. Trying to substitute a 9 cylinder engine of 4 1/2 feet or so would would mean some rather restricted side vision, in addition to several months (at best) of re-engineering and testing.

That doesn't prevent a modern day A-10 from performing CAS. Why should the WWII era Hs-129 be any different?

As for engines....
The historical Hs-129 program got crumbs for resources. Hence the use of French manufactured engines. If the Hs-129 had a higher priority it could have been designed for a pair of 950hp BMW132 radial engines. The BMW132 was inexpensive to produce, reliable and in mass production by the mid 1930s. These more powerful engines would also give the aircraft better aerial performance.

A-10 has enjoyed air superiority. Not the case for Hs-129.

When has a A-10 ever performed without air superiority ?

WWII era German CAS aircraft such as Ju-87s and Hs-129s should have Me-109s for escort. The escorts provide temporary air superiority over the area where CAS aircraft are operating. Similiar to having P-51s escort B-17s over Germany except CAS missions are of much shorter duration.

davebender said:

That doesn't prevent a modern day A-10 from performing CAS. Why should the WWII era Hs-129 be any different?

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By 1944 the Luftwaffe was no longer capable of guaranteeing the needed air superiority for the strike aircraft. Imagine a couple of squadrons of Hs 129s on the Western front in the summer/fall of 1944. Even with Two squadrons of 109s/190s for every squadron of Hs 129s for escort the Allied fighters, available in much greater numbers, would have made the record of the Hs 129 resemble that of the fairly battle in 1940.

davebender said:

As for engines....
The historical Hs-129 program got crumbs for resources. Hence the use of French manufactured engines. If the Hs-129 had a higher priority it could have been designed for a pair of 950hp BMW132 radial engines. The BMW132 was inexpensive to produce, reliable and in mass production by the mid 1930s. These more powerful engines would also give the aircraft better aerial performance.

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The HS 129 was designed for Argus As 410 engines, Inverted aircooled V-12s of 12 liters displacement, about 450-465 hp for take-off weighing just under 700lbs dry and having a frontal area of 3.9 sq/ft. The engines didn't deliver the promised power and the air frame came out over weight. The French Gnome-Rhone's were 14 cylinder radials of 19 liters displacement offering 700hp for take off (and 660hp at 4000meters?) while weighing about 925lbs and having a frontal area of 7.6 sq/ft.

BMW 132s were developed versions of the P&W Hornet engine. Mass production in WW II terms is a far cry from mass production in mid 1930s terms. As an example Wright had made about 8,000 Cyclone engines (a 9 cylinder radial very close to the Hornet) from the mid/late 1920s until 1938. In 1942 alone Wright delivered over 9000 Cyclones with Studebaker supplying over 6000 more due to massive plant expansions. Many of the 21,000 or so BMW 132s built were earlier carburetor models used in the JU 52s. BMW may have had their hands full trying to produce enough BMW 801s judging by the number of French sub contractors brought into the 801 program.

In any case the BMW 132 was a 9 cylinder engine of 27.7 liters displacement offering anywhere from 880 to 1200hp for take off depending on model and water injection fitting while weighing about 1160lbs and having a frontal area of 16 sq/ft. This was a large engine, bigger and heavier than the Bristol Mercury used in the Bristol Blenheim. The weights given are dry weights and do not include propellers, cowlings, exhaust system and some engine accessories like starters or generators. It is also going to suck up more fuel than the Gnome-Rhone if the extra power is used requiring larger fuel tanks (protected?) It might be able to be mounted on a HS 129 but it is not going to be simple. Performance will be increased but the higher empty weight and gross weight and the additional drag of these large engines are not going to provide quite the increase in performance that a simple horsepower comparison would suggest. An easy estimate would be that the complete power plant installation would be 400-500lbs heavier per engine than the Gnome-Rhones. With the extra power the Gross weight of the plane could certainly go up if the structure can handle it or with your increase priority, parts of the plane re-stressed, redesigned and modified to handle the extra weight. Parts like landing gear and or tires might have to be changed. All of these changes increasing weight.
and when you are done you have added over 16 sq/ft of frontal target area to the plane.

IMO that was a poor decision. The As-410 was a nice little engine but they just aren't big enough for for an aircraft with heavy armor plus heavy autocannons.

The original Hs-129 specification was written in 1937. The Hs-129 entered mass production during 1942. 5 years is plenty of time for RLM to order an appropriate air cooled engine into mass production to power the Hs-129. If RLM doesn't want to use the BMW132 engine they might consider license production of a foreign design such as the 825 hp P&W R-1525 twin radial.

The chances of the Germans licensing any Western engine in 1937 would be vanishingly small, although in hind sight it might have been a smart thing to do. By 1938-1940 The Americans had decided that the R-1535 was too small to be worth bothering with. The same reason is why the R-R Peregrine and the Bristol Taurus never went very far. They were too small to power the planes being planned. Getting the Germans to waste resources licence building the R-1535 might have actually been smart. Aside from being useful for the Hs 129 (although that is debatable) it really has no other useful application for the Luftwaffe.
It is a heavier, more expensive alternative to the R-1690 Hornet offering little more than smaller frontal area. Up to 825HP from 21.6 liters it weighed about 1100lbs and had a frontal area of about 10.5 sq/ft.
Henschel had actually wanted to build a slightly enlarged version of the Hs 129 to use the Gnome-Rhone engines but was overruled by the RLM. Stuffing even larger engines into a tight design might be a bad idea.
An enlarged design using 800-1000hp engines might have been a good idea if started early enough but it would no longer be the Hs 129. Perhaps more thought should have been given to the Isotta- Fraschini Delta engine sooner. Although installation would still be a big problem. TI being the longest engine of the bunch and one of the heavier ones, getting the CG right might be troublesome.

Perhaps Do-17 in sclacht role would've been a better bet, than Hs-129? Say, pilot + rear gunner only, cannon armament in bomb bay, rockets bombs under wings. Not as cheap as Hs-129, but more capable on paper.

Dave, I'm certainly not on a par with these guys but from what I've been able to determine this is another German "too little too late" project. The engines were always to underpowered and the two prototypes almost impossible to fly. Improvements and redesign take time. By late 1942 reports were coming in about the ineffectiveness of the MK 103 against newer versions of the Soviet T-34 tanks. One solution would be to use the larger Bordkanone BK 37 gun, recently adapted from ground-based Flak 18. These guns had already been converted into underwing pod-mounted weapons for the Ju 87 and found to be a very effective weapon. When mounted on the Hs 129, the empty area behind the cockpit could be used for ammunition storage, which would address the only problem with the Ju 87's mounting: a limited ammunition supply.
Few Hs 129s were actually installed with the BK 37 however, and the Rheinmetall firm decided to adapt for the aircraft (as had already been done with the heavy-gunned Ju 88P-1) their semi-automatic loading 7.5 cm Pak 40 anti-tank gun into a lighter-weight, fully-automatic aircraft-mountable version, with a completely different and more aerodynamic muzzle brake, to produce the Bordkanone BK 7.5 model. A huge hydraulic system was used to dampen the recoil of the gun, and an autoloader system with 12 rounds in the magazine (easier to design and fit because of the PaK 40's already semi-automated loading) was fitted in the large empty space behind the cockpit, with the gun and its recoil mechanism occupying a gun pod under the fuselage and a hole in the rear end of the pod to allow spent cartridges to be ejected. The resulting system was able to knock out any tank in the world, but its weight slowed the already poor performance of the plane to barely flyable in this new Hs 129 B-3 version.
B-3s finally started arriving in June 1944, and just 25 were delivered by the time the lines were shut down in September. A small number were also converted from older B-2 models. In the field they proved deadly weapons, but with only 25 aircraft available they had no effect on the war effort.
The 1,200 kg (2,645 lb) Bordkanone BK 7.5 cannon installation in the Hs 129B-3 was the heaviest forward-firing "big-gun" installation ever made for a series production military aircraft, until introduction of the 1970s-era General Electric GAU-8 Avenger seven barrel 30mm caliber anti-tank Gatling cannon (as the A-10's main armament) at a total weight with ammunition of up to 1,830 kg (4,030 lb).
[edit] Hs 129 C
In order to address the poor performance of the aircraft, plans had been underway for some time to fit the plane with newer versions of the Italian Isotta-Fraschini Delta engine that delivered 630 kW (850 hp). The engine installation ran into a number of delays however, and was still not ready for production when the plant was overrun by the Allies in 1945.
So with new more powerful engines a deadly "safe-cracker" but still unable to perform without fighter escort

12,400 marks. BMW132. 1941 price.
27,970 marks. DB601. 1941 price.
30,875 marks. Jumo211. 1941 price.

The BMW132 radial was dirt cheap to produce. You can purchase two with change left over for the cost of one water cooled V12. It might be worth paying a bit more for an airframe which can accomodate this relatively large engine. You end up with an aircraft that is still low cost yet quite powerful.

Not to deflect the topic, but if I had been a LW pilot after 1941 I would NOT have wanted to use any equipment/supplies that came out of France. I think "quality-control" was - spotty .

Was there ANY ground attack aircraft that didn't need top-cover, air superiority when in the ground attack operational mode - I mean even P-47s and Typhoons would be vulnerable, no?

MM

the hs 129 was phased out or should ssay the sole unit with the rig was due to losses and no replacements. The Ju 87 G-1 and G-2 did the same and in more numbers and the Panzerblitz equipped Fw 190F and G variants which did not need high cover, of course we can also look at the ground attack work with the R4M with panzerschrek heads used on Soviet armor in spring of 45 by JG 7 and their Me 262A's.

the biggest foe for the low level flying hs 129's were the Soviet mobil flak units not Soviet fighters

The P-47s and Typhoons were vulnerable on the way out when loaded. Any plane is vulnerable to attack from above and if you are already operating on the deck that means most everybody is above you.
However, trying to bounce a fighter carrying rockets or bombs but doing 300mph plus might be a bit harder than trying to bounce somewhat slower dedicated ground attack planes. The bomb carrying fighters can also jettison the bombs (a mission kill for the defenders?) and put up a much better scrap than the ground attack planes could. Planes carrying large cannon either under wing or under fuselage usually performed worse than unloaded ground attack planes unless they could jettison the cannon installation and are pretty much useless in air to air combat because of the weight and drag of the cannon installations.

though OP may I suggest the HS 129 book by Martin Pegg from Classic publications.

P47s and Typhoons were ineffective at destroying tanks. If you cannot accomplish the primary mission then survivability is a moot point. Anthony Williams sums up the issue nicely.
TANKBUSTERS: AIRBORNE ANTI-TANK GUNS IN WW2

The ineffectiveness of air attack against tanks should have caused no surprise because the weapons available to the fighter-bombers were not suitable for destroying them. Put simply, the heavy machine guns and 20 mm cannon were capable of hitting the tanks easily enough, but insufficiently powerful to damage them, except occasionally by chance. The RPs and bombs used were certainly capable of destroying the tanks but were too inaccurate to hit them, except occasionally by chance.

Experience showed that the best way of knocking out tanks was to use a cannon powerful enough to penetrate the armour.

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The Ju-87G was a viable alternative to the Hs-129. Makes me wonder why the Hs-129 tank buster was built at all. RLM could have purchased cannon armed Ju-87s from the late 1930s onward rather then designing the Hs-129 and producing it in small numbers.

The best way to knock out tanks and other AFV was to knock out the supplies needed by them to operate. No fuel, no ammo, no fight.

best way to knock out tanks and other AFV was to knock out the supplies needed by them to operate.

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That doesn't help an infantry unit about to be over run by an enemy armored force. They need CAS that can kill tanks on the battlefield.

davebender said:

P47s and Typhoons were ineffective at destroying tanks. If you cannot accomplish the primary mission then survivability is a moot point. Anthony Williams sums up the issue nicely.

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I believe the P-47 and Typhoon were brought into the discussion as regards to vulnerability of ground attack aircraft, not as examples of tank buster effectiveness.

davebender said:

The Ju-87G was a viable alternative to the Hs-129. Makes me wonder why the Hs-129 tank buster was built at all. RLM could have purchased cannon armed Ju-87s from the late 1930s onward rather then designing the Hs-129 and producing it in small numbers.

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Why don't you read up on the subject.
How many Ju-87Gs were built?
Wing mounted large caliber cannon were less accurate than fuselage mounted guns.
A number of Hs 129s didn't carry big cannon but carried bombs.
Was the Ju-87G armored to the extent the Hs 129 was?
Early Ju-87 might not have been able to carry 37mm guns although high powered 20mm might have been enough against 1937-1940 tanks.
Changing "priorities" doesn't mean you got more of something at no cost. Cost is not money, It means you get more of one thing and less of something else. Why did the RLM want to use Argus engines to begin with? Because all the better engine capacity was already spoken for. You want higher priority for the tank buster, fine, for 800 tank busters with BMW 132s what 800 twin engined planes using BMW 132s do you want to give up? or 1600 single engine planes or what combination. Want another 800 Ju 87Gs? thats 400 JU 88s or He 111 not built. Airily saying 'just build another engine factory' doesn't cut it either. The steel structure and concrete have to be taken from another program along with building fixtures. The machine tools have to come from somewhere, so some other factory isn't built or equipped properly.