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Junkers Ju 87 "Stuka"
Design & Structure

The Ju 87 was a single-engined all-metal cantilever monoplane. It had a fixed undercarriage and could carry a two-person crew. The main construction material was duralumin, and the external coverings were made of Duralumin sheeting. Parts that were required to be of strong construction, such as the wing flaps, were made of Pantal (a German aluminum alloy containing titanium as a hardening element) and its components made of Elektron. Bolts and parts that were required to take heavy stress were made of steel.

The Ju 87 was fitted with detachable hatches and removable coverings to aid and ease maintenance and overhaul. The designers avoided welding parts wherever possible, preferring moulded and cast parts instead. Large airframe segments were interchangeable as a complete unit, which increased speed of repair.

The airframe was also subdivided into sections to allow transport by road or rail. The wings were of standard Junkers double-wing construction. This gave the Ju 87 considerable advantage on take-off; even at a shallow angle, large lift forces were created through the aerofoil, reducing take-off and landing runs.

In accordance with the Aircraft Certification Center for "Stress Group 5", the Ju 87 had reached the acceptable structural strength requirements for a dive bomber. It was able to withstand diving speeds of 600 km/h (370 mph) and a maximum level speed of 340 km/h (210 mph) near ground level, and a flying weight of 4,300 kg (9,500 lb). Performance in the diving attack was enhanced by the introduction of dive brakes under each wing, which allowed the Ju 87 to maintain a constant speed and allow the pilot to steady his aim. It also prevented the crew from suffering extreme g forces and high acceleration during "pull-out" from the dive.

The fuselage had an oval cross-section and housed a water-cooled inverted V-12 engine. The cockpit was protected from the engine by a firewall ahead of the wing center section where the fuel tanks were located. At the rear of the cockpit, the bulkhead was covered by a canvas cover which could be breached by the crew in an emergency, enabling them to escape into the main fuselage. The canopy was split into two sections and joined by a strong welded steel frame. The canopy itself was made of Plexiglas and each compartment had its own "sliding hood" for the two crew members.

The engine was mounted on two main support frames that were supported by two tubular struts. The frame structure was triangulated and emanated from the fuselage. The main frames were bolted onto the power plant in its top quarter. In turn, the frames were attached to the firewall by universal joints. The firewall itself was constructed from asbestos mesh with dural sheets on both sides. All conduits passing through had to be arranged so that no harmful gases could penetrate the cockpit.

The fuel system comprised two fuel tanks between the main (forward) and rear spars of the (inner) anhedral wing section of the port and starboard wings, each with 240-litre (63 US gal) capacity. The tanks also had a predetermined limit which, if passed, would warn the pilot via a red warning light in the cockpit. The fuel was injected via a pump from the tanks to the power plant. Should this shut down, it could be pumped manually using a hand-pump on the fuel cock Armature. The powerplant was cooled by a 10-litre (2.6 US gal), ring-shaped aluminium water container situated between the propeller and engine. A further container of 20-litre (5.3 US gal) was positioned under the engine.

The control surfaces operated in much the same way as other aircraft, with the exception of the innovative automatic pull-out system. Releasing the bomb initiated the pull-out, or automatic recovery and climb, upon the deflection of the dive brakes. The pilot could override the system by exerting significant force on the control column and taking manual control.

The wing was the most unusual feature. It consisted of a single center section and two outer sections installed using four universal joints. The center section had a large negative dihedral (anhedral) and the outer surfaces a positive dihedral. This created the inverted gull, or "cranked", wing pattern along the Ju 87's leading edge. The shape of the wing improved the pilot's ground visibility and also allowed a shorter undercarriage height. The center section protruded by only 3 m (9 ft 10 in) on either side.

The offensive armament was two 7.92 mm (.312 in) MG 17 machine guns fitted one in each wing outboard of undercarriage, operated by a mechanical pneumatics system from the pilot's control column. The rear gunner/radio operator operated one 7.92 mm (.312 in) MG 15 machine gun for defensive purposes.

The engine and propeller had automatic controls, and an auto-trimmer made the aircraft tail-heavy as the pilot rolled over into his dive, lining up red lines at 60°, 75° or 80° on the cockpit side window with the horizon and aiming at the target with the sight of the fixed gun. The heavy bomb was swung down clear of the propeller on crutches prior to release.

Sources:
WikiPedia
Gunston, Bill & Wood, Tony - Hitler's Luftwaffe, 1977, Salamander Books Ltd., London
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