SU1946 stands for Simple Universe 1946, it is a series of late-WWII (or prototypes) planes plus some fiction. Planes in this series would have significantly better performance than their historical counterpart, and would receive a "Z" in their names to distinguish them from other, more accurate replicas.

This is the Simple Universe version of the Alekseyev I-21, 5th design, tricycle undercarriage (I-215D). In real world it was a prototype jet fighter built in mid-1940s, but here in our SU1946 series, it plays a different role.
In the earlier days where the Me 262 HGII PR fought against Su-9 KZ TsPGO over the vast battlefield of Chinese Civil War, it used to be a somewhat fair fight: the Su-9 would have the advantage of "first strike, first kill", while the Me-262 HGII would dominate the dogfight should they successfully dodged the missile. However, the later HGIII changed this, now the Communists barely have any chance in their obsolete straight-wing Su-9s against the radically designed HGIII, who boasts both superior agility and speed. With the intel of Allied progress on fire-and-forget missiles and countermeasures, the Soviet Union and the Chinese Communists both concluded that they can't kill the HGIII, unless they kill it on the ground.
With that in mind, they turned to the OKB-21 and their I-21 project, hoping to build an attack aircraft that can penetrate any air defense, and dodge the HGIIIs should they encounter any. Alekseyev OKB-21's answer was the I-215DZ. With the ingeniously designed double-layer hull and cleverly distributed fuel tank compartments, the 215DZ boasts extraordinary defense and low-speed stability, while remaining highly mobile to evade the Nationalists' fighters once ordnance are dropped.
The Nationalists are having trouble intercepting these I-215DZs at the beginning, with some outrageous losses like losing a patrol fleet of one Tiny-class carrier and two destroyers to merely one flight of I-215DZs who weren't even carrying any bombs. However, they soon understood that they can harass them to buy the attack subject more time to either flee the battlefield or to take proper measures to fend off the attack. Still, the I-215DZs proved to be an effective surprise attack asset who can catch the Nationalists unprepared. With their mobility, firepower and the newly acquired element of surprise from the carrier operation and aerial refuel capabilities, the I-215DZ managed to help the PLAAF keeping their ability to push forward.

Performance:
Speed: can reach a safe speed of 1200 km/h, after that it would start to wobble up-and-down, shortening the life of the tailplanes. Only use for emergency situations.
Agility: 7.42 seconds to turn 360 degrees at sea level @ 1330 km/h

Armament:
3x 37mm NS-37 autocannons (750 damage, 6 rounds per second, muzzle velocity 690 m/s)
11x hardpoints for air-to-ground missiles, rockets and bombs.
Fuselage hardpoints are usually for bombs and reverse-engineered refueling pods, while outer hardpoints are for smaller missiles or rocket/ rocket pods. Cleaver missiles can hardly be carried anywhere beside the 2 inner wing hardpoints.

Activation groups:
AG1: Tail hook.
AG2: Drag chute
AG3: Jettison outer-wing ordnance.
AG4: Jettison inner-wing and under-fuselage ordnance.
AG5: Free for other assignments.
AG6: Refuel Probe.
AG7: Fold/Unfold wing.
AG8: Unlock/Lock wing folding mechanism (similar to how the HGIII works)
Trim: Flaps, mostly used for low-speed operations.

Caution: the inner wing was edited in XML to be a structural wing because I already finished the shape when I found out it is too weak to put it as a normal wing. It allows adding control surface at the moment, but I'm not sure what will happen if you actually do that. I might should have edited the "allowcontrolsurface" too....

I'm probably gonna build a super-armored RB-17 bomber next, and then maybe a reverse-engineered Me P.1102B (imitating the Soviets' double-layer fuselage).