The Hs 129 idea done 'right', and for everyone

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tomo pauk

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Apr 3, 2008
Hs 129 was a result of specification that required a small 2-engined aircraft, powered by 'non-strategic' engines (ie. by the engines not required for the 1st line A/C), well armored, and with some meaningful firepower.
(the non-strategic engine part was flawed IMO - once you must manufacture two engines per A/C, and the total HP provided is lower than on a single 'normal' engine, while needing two propellers, two oil systems, that math falls in the water, but I digress)
Let's change the spec a bit, and apply it for other countries, too. Still a small 2-engined A/C is required, well armored, with very good firepower, preferably 1-seater, engines in question are preferred to be of non-strategic type, but without going into extremes so the AC is under-powered, IOW no need to go for 400-600 HP engines. Good guns' firepower is needed, so is the carriage of a lot of small bombs. No bomb bay is required.
Yes, some air forces don't have a thing for tactical A/C that much, let's have that changed for the purposes of this thread.
Aircraft needs to be in service by early 1940 in it's 1st version.
 
You probably won't get much more powerful radial engines in this size and weight class unless you want to stick much bigger ones onto it which would likely require to legthen the fuselage and increasing the wing area. Or going liquid cooled with armor on engines and coolers.
 
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One .50, one .30 and about six 50lb bombs ;)

Shows up a little late but there is nothing too tricky.

Staying away from 400hp engines is a bit tough.
 
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One .50, one .30 and about six 50lb bombs ;)

Shows up a little late but there is nothing too tricky.

Staying away from 400hp engines is a bit tough.

I was thinking more about something size and shape of the F5F, down to the size and shape of the Ro.57.

Sounds a lot like one of these:

Ok...it wasn't exactly small and it had a crew of 2 but it was in service in the summer of 1940 and it was well-armed.

For the British, a Whirlwind but with Mercuries instead of Peregrine?
 
I was thinking more about something size and shape of the F5F, down to the size and shape of the Ro.57.



For the British, a Whirlwind but with Mercuries instead of Peregrine?
Sorry, I misread it to mean using engines lower than 400hp :oops:

We do have problem with using 800-900hp 9 cylinder radials instead of the GR 14M radials on the Hs 129 and that is that 9 cylinder radials are freaking huge.
A tremendous increase in both drag and target area. Doesn't do lot for pilots vision either.

We also have problem with wing area. The HS 129 had 310 sq ft of wing and MAX take-off weight was 11,574 lb (5,250 kg) for the B2 (wiki)
Max wing loading is 37.3lb/Sq ft. For a front line ground support plane you need (or at least want) short field, rough runway capability so you can't go too small on the wing.

The Germans had the 30mm cannon early, at least around 100 of them (?).
Anybody else in 1940 is scrambling, Trying to fit 37mm infantry or AT Guns, or multiple 20mms (and you need something like the Hispano in order to be credible and that goes away in 1941/42), We know the US 37mm was not an anti armor gun, trucks and barges yes but not much of an improvement on the 20mm Hispano.

The Ro. 57 had a 250sq ft wing, Max wing loading is about 18% higher than the HS 129
The Fiat 14 cylinder engine was almost 300mm bigger in diameter the GM engines.
I will assume that more work on the structure will allow a fair amount of armor for no increase in weight ( :) )
Two Italian 12.7mm machine guns are not going to cut it for ground attack.

The US (or British) could have started with P & W R-1535s of 825hp and about 1100lbs and 44in diameter ( almost 180mm bigger than the GR engines).
P & W stops making them or continuous with improved model/s?
 
We do have problem with using 800-900hp 9 cylinder radials instead of the GR 14M radials on the Hs 129 and that is that 9 cylinder radials are freaking huge.
A tremendous increase in both drag and target area. Doesn't do lot for pilots vision either.

We also have problem with wing area. The HS 129 had 310 sq ft of wing and MAX take-off weight was 11,574 lb (5,250 kg) for the B2 (wiki)
Max wing loading is 37.3lb/Sq ft. For a front line ground support plane you need (or at least want) short field, rough runway capability so you can't go too small on the wing.

I'd go for a bit bigger A/C, ballpark of the Fw 187. Perhaps a short-stroke BMW 132 (or Bramo 323) can be produced in a pinch, sorta how Mercury came about? Or, have the Germans start out with these engines as-is, and adopt the Mercury as manufactured in Poland?

The Germans had the 30mm cannon early, at least around 100 of them (?).
Anybody else in 1940 is scrambling, Trying to fit 37mm infantry or AT Guns, or multiple 20mms (and you need something like the Hispano in order to be credible and that goes away in 1941/42), We know the US 37mm was not an anti armor gun, trucks and barges yes but not much of an improvement on the 20mm Hispano.

There was no 30mm-armed Hs 129 before mid-1942, so the other countries will have no problem in matching the initial guns' firepower of the Hs 129.
British can try with 25.4mm Vickers (as sold to Argentina) or the 2pdr pom pom; later improve to the Class S weapon.
Americans - six .50s for starters? Combine .50s with M4 37m until something better is around, like the M9?
Soviets - they have the best toys.
Italians - a lot of 12.7mm?
Japanese - 2x 20mm (no great shakes).

Don't forget to add the bomb and rockets :)
 
I'd go for a bit bigger A/C, ballpark of the Fw 187. Perhaps a short-stroke BMW 132 (or Bramo 323) can be produced in a pinch, sorta how Mercury came about? Or, have the Germans start out with these engines as-is, and adopt the Mercury as manufactured in Poland?
BMW 132.... 156 x 162 cylinders, 1690 cu in 54.3in dia?
Bramo 323...154 x 160 cylinders, 1636 cu in 52.7 in dia?
Mercury........146 x 165 cylinders, 1520 cu in 52in dia?

Size of heads/fins and two big valves ve 4 little ones?
Different length of con rods vs length of stroke?
Difference doesn't seem to be enough to worry about.
Frontal area of the Mercury 1.37 M2
Frontal area of the GR 14M 0.70 M2
or the 2pdr pom pom
weight of the 2pd Pom Pom was 784-918lbs (may include water? weight of barrel 125lbs
Grabbing a AA gun (especially a Naval one) for a quick and handy aircraft may not be a good idea.
115kg for the Japanese 25mm AA gun.
 
BMW 132.... 156 x 162 cylinders, 1690 cu in 54.3in dia?
Bramo 323...154 x 160 cylinders, 1636 cu in 52.7 in dia?
Mercury........146 x 165 cylinders, 1520 cu in 52in dia?

Size of heads/fins and two big valves ve 4 little ones?
Different length of con rods vs length of stroke?
Difference doesn't seem to be enough to worry about.
Frontal area of the Mercury 1.37 M2
Frontal area of the GR 14M 0.70 M2
Well, certainly the speed records will not be broken by our astute attackers :)

weight of the 2pd Pom Pom was 784-918lbs (may include water? weight of barrel 125lbs
Grabbing a AA gun (especially a Naval one) for a quick and handy aircraft may not be a good idea.
115kg for the Japanese 25mm AA gun.
Seems like the ww1-left-over was at 505 lbs without the water per this.
German MK 101 and 103 were at ~140 kg (~310 lbs) without ammo; Hs 129 carried one of these + 2x MG 151. Rarely the BK 3.7 was carried, the rare BK 7.5cm required deletion of the MG 151s, but it was a hefty piece anyway (not that I'm advocating for the 7.5cm to be carried en-masse).
 
Well, certainly the speed records will not be broken by our astute attackers :)


Seems like the ww1-left-over was at 505 lbs without the water per this.
German MK 101 and 103 were at ~140 kg (~310 lbs) without ammo; Hs 129 carried one of these + 2x MG 151. Rarely the BK 3.7 was carried, the rare BK 7.5cm required deletion of the MG 151s, but it was a hefty piece anyway (not that I'm advocating for the 7.5cm to be carried en-masse).
Well, if you are happy with just about 2000fps veleocity ;)
and ", but the automatic mechanism was lighter and less robust. As introduced, these guns used 25-round fabric belts."

the MK VIII gun
LV: 572 lbs. (259.5 kg)
HV: 850 lbs. (385.6 kg)
veleocity
LV: 1,920 fps (585 mps)
HV: 2,400 fps (732 mps)
Shell weight
HE LV 2.0 lbs. (0.91 kg)
SAP: 2.0 lbs. (0.91 kg)
AP: 2.0 lbs. (0.91 kg)
HE HV: 1.81 lbs. (0.82 kg)

Vickers gun used on the Hurricane IID
1,870 ft/s (570 m/s)with 3 lb (1.4 kg) shot
RR version
-Rolls-Royce_type_BH_40mm_Aircraft_Cannon_20100202.jpg


The problem with these big guns is the rate of fire. Around 1 1/2 to 2 1/2 shots a second. If they hit they were devastating.
However a 20mm Hispano fired about 5 rounds for every one the big guns did and you could mount two Hispanos for every one of the big guns and have weight to spare. A lot of weight, Maybe enough weight for 3-4 guns and ammo.

Hmmm, 5 rounds of 40mm fired in the attack run...............................................100 rounds of 20mm Hispano is the same attack run?
Unless the target needs the 40mm shell it is a poor trade off.
 
The problem with these big guns is the rate of fire. Around 1 1/2 to 2 1/2 shots a second. If they hit they were devastating.
However a 20mm Hispano fired about 5 rounds for every one the big guns did and you could mount two Hispanos for every one of the big guns and have weight to spare. A lot of weight, Maybe enough weight for 3-4 guns and ammo.

Hmmm, 5 rounds of 40mm fired in the attack run...............................................100 rounds of 20mm Hispano is the same attack run?
Unless the target needs the 40mm shell it is a poor trade off.

Hispano is all fine and dandy if you have it. British don't have it when Germans broke out in May of 1940, but they do have the 2pdrs. Hispano for the Americans - even the often bad-mouthed 1.1 in is better until well into ww2.
A 2pdr pom-pom will kill the German panzer in 1940.
 
Hispano is all fine and dandy if you have it. British don't have it when Germans broke out in May of 1940, but they do have the 2pdrs. Hispano for the Americans - even the often bad-mouthed 1.1 in is better until well into ww2.
A 2pdr pom-pom will kill the German panzer in 1940.
Well, they were putting Hispanos into Beaufighters in 1940, and into a few Whirlwinds and few Spitfires, even hung a few off of Lysanders and at least on top the wing of a Hurricane.
BTW the P-40D (Kittyhawk) was supposed to have provisions for mounting a 20mm gun under the wing. Instructions in the manual are rather sketchy.
The gun goes under the wing just out board of the outer .5in gun and may be mounted by making the proper skin cutouts and installation of the equipment.
Worse instructions than on 99% of the model kits in the world :)
Little wonder that actual photos are either very, very rare or nonexistent.

The US Navy had enough trouble making the 1.1 run on the deck of a ship with bunch of men available to beat on it. Stuck out in a wing (or under it) with a pull cable????
 
Well, they were putting Hispanos into Beaufighters in 1940, and into a few Whirlwinds and few Spitfires, even hung a few off of Lysanders and at least on top the wing of a Hurricane.

IIRC neither of these was there to stop the panzers rolling through the Belgian fields.

The US Navy had enough trouble making the 1.1 run on the deck of a ship with bunch of men available to beat on it. Stuck out in a wing (or under it) with a pull cable????

Under a fuselage in this case, one per A/C (provided that Navy will play the ball, of course).
 
OK, use 15mm Besa guns.
Some (not many) were in use in MK VIC light tanks.
In power it was between the German 15mm MG 151 and the Soviet 14.5mm AT rifle. It should be able to make holes in most 1940 German tanks. ;)

Very good call on the 15mm Besa. Just give it a proper AP shot (APCR preferably in 1939/40) and it will do the work.
 
Steel will work in 1939/40. This thing hits almost 3 times harder than British, Italian, Japanese 12.7mm and around 50% harder than Soviet 12.7mm. 1940 is the dividing time for US .50 cal In early 1940 the Besa has about double the energy of the US .50.
It does NOT have exploding ammo. Strafing troops is best left to the .303 guns for the British.
It was pretty much the size and weight of the Hispano so it is temporary place holder, when you get 20mm Hispanos pop them in place of the 15mm Besa.

However the comparison of the 12.7mm cartridges holds true for other nations.
The Italians can't use the normal aircraft heavy machine guns for shooting up British light armor. Not enough punch.
They need to go right to a 20mm gun and figure out how to feed one of their AA guns.
Same for the Japanese, not that they really worried about shooting up tanks but for that job they were working on the Ki-45.

French have the 13.2mm Hotchkiss which is marginal at best and with the 30 box round magazine aircraft use gets a bit dubious.
The French do have 20mm Hispanos.
The French 25mm Hotchkiss AA gun is just over twice as powerful as the as the Hispano but the increase in size means you are trying to make a hole that is about 50% bigger.
The 25mm AA is at least twice as heavy, it fires less about 1/2 as fast (depends on exact version) and as an AA gun it used 15 round magazines so you need to develop new magazines and/or drums.
The 25mm Hotchkiss AT gun used totally different ammo that was about 40% powerful.

Once you start looking at 37mm AA guns you really need a more substantial airplane.
 
Steel will work in 1939/40. This thing hits almost 3 times harder than British, Italian, Japanese 12.7mm and around 50% harder than Soviet 12.7mm. 1940 is the dividing time for US .50 cal In early 1940 the Besa has about double the energy of the US .50.
It depends what is the intended target.
German 15mm with steel projectile (72 g at 850 m/s) was good for 25mm or armor at 90 deg impact and at 300m. The Pz-I and -II is a fair game, while the Pz-III or IV will require an ideal hit from behind - not somthing we can count on.
The tungsten-carbide projectile on the MG 151/15 upped the penetration by almost factor of 2 - it was good for 42-44 mm at 90 deg and at 300m.
Besa 15mm fired a 75g projectile at 820 m/s.

French have the 13.2mm Hotchkiss which is marginal at best and with the 30 box round magazine aircraft use gets a bit dubious.
The French do have 20mm Hispanos.
The French 25mm Hotchkiss AA gun is just over twice as powerful as the as the Hispano but the increase in size means you are trying to make a hole that is about 50% bigger.
The 25mm AA is at least twice as heavy, it fires less about 1/2 as fast (depends on exact version) and as an AA gun it used 15 round magazines so you need to develop new magazines and/or drums.
The 25mm Hotchkiss AT gun used totally different ammo that was about 40% powerful.

Using bigger guns allows for non-ideal hits to still penetrate and do the damage, and don't require tungsten as much it will be necessary for the smaller guns. I don't have the pentration figures handy for the French 25; Soviet 25mm was supposed to penetrate 38mm at 90 deg at 250m (steel penetrator).
Yes, the 25mm will require a better ammo feed system, a 60-rd drum should come in handy.
French could also use the 37mm cannon, with a good feed mechanism that is, as it was the case with this weapon.

Once you start looking at 37mm AA guns you really need a more substantial airplane.

Ro.57 was eventually rated for a 1000 kg bomb, the Hs 129 for a 7.5cm cannon - I'd say that these compact aircraft were substantial enough for 37mm artillery :)
Hurricane carried two 40mm guns, that were much more powerful than the 2 pdr pom-poms.
 

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