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

[Shortround6]

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.

"Bullet weight was 1160 grains (75 grams)and the propellant charge was 325 grains of Cordite for the W Mark I and 370 grains of nitro-cellulose for the W Mark Iz.Velocity at 90 feet was 2,900 feet per second (883m/s) at a maximum mean pressure of 22 tsi and penetration was seven out of ten shots must penetrate 27mm armour plate at 100 yards."

Pz 35 (t) 25mm armor on the front. 15/16mm armor on the sides and rear.
Pz 38 (t) 25mm armor on the front. 15/16mm armor on the sides and rear. The versions with more armor don't leave the factory until Nov 1940
Pz IIIE in France had 30mm front and sides, rear of turret was 30mm, hull was 21mm. Any of the older versions with 14.5/15mm armor had been taken out of service in Feb 1940.
Pz IV B&C had 30mm front as built and 15mm sides and rear. some were up armored before France but not everywhere.
Pz IV D had 30mm front as built and 20mm sides and rear but again, not all were unarmored and not all got 100% coverage of up armoring (some were far from it).

British knowledge of the up armoring??

It is not ideal, it is what you have and the alternatives need more work (heck the 15mm may need work for aircraft mounting)

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.

Yes and no.
The Vickers 2pdr used in aircraft used a much longer recoil stroke than the 2pdr pom-pom. The peak recoil loads were less than a 20mm Hispano. The 2pdr Vickers delivered more total recoil but it was spread out over a longer period of time.

The Pak 7.5 cm AT gun recoiled over 1 meter in distance. Spread the recoil out so the gun didn't bounce around all over the place on it's wheels. The Tank cannon with about the same recoil only recoiled about 30-40CM (?) but you had a 20-25 ton vehicle keeping it in place. It also only a few shells per flight.

I don't know about the French 37mm, the Italian 37mm AA gun was noted for poor accuracy because it vibrated the deck mount/plates.

Not all guns are adaptable for aircraft use without a lot modification.

 

[tomo pauk]

British knowledge of the up armoring??

It is not ideal, it is what you have and the alternatives need more work (heck the 15mm may need work for aircraft mounting)

British don't know the exact armor thickness of German tanks in the 1st place. They do know that vast majority of French tanks have armor topping 40mm well before ww2, and can expect that Germans will try and match it.
Going with a more substantial gun = better safe than sorry.

Yes and no.
The Vickers 2pdr used in aircraft used a much longer recoil stroke than the 2pdr pom-pom. The peak recoil loads were less than a 20mm Hispano. The 2pdr Vickers delivered more total recoil but it was spread out over a longer period of time.
The Pak 7.5 cm AT gun recoiled over 1 meter in distance. Spread the recoil out so the gun didn't bounce around all over the place on it's wheels. The Tank cannon with about the same recoil only recoiled about 30-40CM (?) but you had a 20-25 ton vehicle keeping it in place. It also only a few shells per flight.
I don't know about the French 37mm, the Italian 37mm AA gun was noted for poor accuracy because it vibrated the deck mount/plates.
Not all guns are adaptable for aircraft use without a lot modification.

There will be a lot of work indeed. Better start with it ASAP so the workable firepower is to be had by 1939.

 

[GrauGeist]

The BK7.5 was a bit much for the Hs129 to heft around, though.

The BK3.7 did produce solid results against targets and weighed less, allowing for more stable flight.

I am surprised that the Luftwaffe didn't consider the BK5 as an option, though they did use it mounted in Me410s for anti-bomber operations.

BK7.5 weighed 1,554 pounds.
BK3.7 weighed 650 pounds.
BK5 weighed 1,190 pounds.

 

[wiking85]

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.

Simply, just build the HS123C en masse.

 

[tomo pauk]

Simply, just build the HS123C en masse.

Hs 123 does not apply - topic is about 2-engined attackers.

 

[wiking85]

Hs 123 does not apply - topic is about 2-engined attackers.

At a certain point you have to think outside the box to arrive at the right design.
But if you absolutely insist on 2 engines I'd say save DB601/5s from the DB606/10 project (which should have been cancelled) and instead build the Me109Z:

Me 109 Zwilling

This experimental aircraft was essentially two Bf 109F airframes joined together by means of a new wing centre section and new tailplane, both of constant chord. In the preproduction model, the...

www.nevingtonwarmuseum.com

Would have had all the necessarily firepower and hauling capabilities to conduct ground attack missions and ability to replace the Bf110, while increasing production overall from economies of scale.

If you insist on the non-strategic engines, then modify the fuselages to handle the Hs123's engine the HS132, but the late version W-series with about 1000hp.

Or a HS123Z...

 

[tomo pauk]

But if you absolutely insist on 2 engines I'd say save DB601/5s from the DB606/10 project (which should have been cancelled) and instead build the Me109Z:
Would have had all the necessarily firepower and hauling capabilities to conduct ground attack missions and ability to replace the Bf110, while increasing production overall from economies of scale.

Me 109Z is many times a very good suggestion. Would not be out of place here, too. A bit better armor protection should come in handy. I'd definitely go with both fuselages being 'populated' (as always for the 109Z IMO).
Another change that I'd make is having one pair of stronger U/C members vs. two pairs of historical U/Cs - saves internal volume, as well as some weight.

 

[mack8]

For what it's worth, i have read that there was a Henschel P76 project which was a slightly larger Hs-129 but with BMW-132 engines. So more power would be good, and as i understand the 132 was reliable while the 14M not so much.

 

[GrauGeist]

The Hs129B series was a result of the P.76 proposal, with the G-R 14M replacing the Argus 411 engines.

The Hs129C/D was planned to have either inlines or BMW801 radials.

 

[Howard Gibson]

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.

I figure the Hs 129 had the success it did because it operated on the Russian Front. If they had flown these things in Normandy, they would have been quickly and efficiently massacred. Use the biggest engines possible.

How about the tiniest aircraft possible, built around two BMW801s, and the BK7.5?

 

[tomo pauk]

How about the tiniest aircraft possible, built around two BMW801s, and the BK7.5?

Focke Wulf was pitching the BMW 801-powered Fw 187 in the same time they were making a pitch for a DB 605-powered version. Former was some 530 kg heavier empty than the later. Both were also supposed to carry up to 2000 kg worth of bomb, as well as to be outfitted with 4 cannons, as well as with two rear-firing MG 131s.
BMW-powered 187 was supposed to weight 8730 kg with 1000 kg of bombs, and another 1000 kg more with 2000 kg (doh).

So this is probably the tiniest aircraft that fits the description. Also makes P-47N not that heavy in comparison