Junkers Ju-88
Structural features of Luftwaffe fighter-bomber

by Sgt William S Friedman

Late last year a young German pilot, a bit battle weary, landed his Junkers Ju-88 on a Mid-Eastern airdrome and turned it and himself over to the Allies. The ship he surrendered proved a veritable treasure-house of information to the United Nations. After a cursory inspection at Cairo, auxiliary tanks were added to increase its range from 1300 to 2000 miles and the ship was flown to Materiel Command Headquarters at Wright Field, Dayton, OH, in a little under five and a half days.

The Ju-88 family of aircraft should be considered as a basic airframe design, capable of broad modification and adaptation. Probably no single plane used by the Axis serves as many purposes. The United Nations have no direct parallel, but the Mosquito, Douglas A-20 and possibly the North American B-25 operate along somewhat the same lines.

In essence, all Ju-88s are structurally similar. They are twin-engined low-wing monoplanes with single fin and rudder and a conventional retractable landing gear. The Ju-88's all-metal wing is built with a constant taper in thickness. In plan form, the section between the engines and the fuselage is almost constant. Beyond this point, both edges have an irregular taper and raked tip. The wing has a conventional two-spar construction with flush-riveted stressed skin covering. The entire trailing edge is hinged, the outer sections acting as ailerons, the inner ones as landing flaps. Outboard of the engine nacelle, a venetian-blind diving brake is fitted to the lower surface of the wing, attached to the front spar. Four self-sealing tanks are carried in the wing between the spars, two between the engine nacelle and the fuselage, two in the outboard panels. A fifth tank is carried in the fuselage between the main spars.

The fuselage is the simplest possible oval semi-monocoque structure, built up of Z-section bulkheads and "top hat" section stringers, to which the skin is flush-riveted. All tail surfaces are cantilever type, with internal all-metal framework. On most models, the fixed surfaces are covered in flush-riveted metal, while the movable surfaces are fabric covered.

The retractable landing gear system, which draws the wheel inward and backward, rotates the main leg 90° on its vertical axis, so that the wheel stows in flat. The main support Vee and the anti-shimmy unit are made up of large aluminum forgings and castings, with ball bearings at every moving or folding terminal.

The power plant, in most of the modifications, consists of an inverted V-12 Junkers Jumo 211 series liquid-cooled engine, mounted ahead of the wing's leading edge. The radiator consists of several core units mounted radially around the drive shaft. Oil radiators and other auxiliary cooling units are also incorporated into this ring. The entire core system is enclosed by a cowl, not unlike an NACA ring, with controllable air gills at the cowl's trailing edge, the same as a typical air-cooled installation.

The ship is equipped with a solenoid-operated air pressure valve, which allows the rapid jettisoning of the fuel from tanks in case of emergency. The propellers are usually VDM full-feathering units with compressed wood blades.

The Ju-88 was among the first aircraft to be provided with exhaust-heat de-icing. Hot air, taken from a cuff from four of the engine exhaust stubs, can be directed by means of lagged flexible tubes to the leading edge of the wing, the front windshield or the rear of the cabin. The tail-unit, however, is protected by an ordinary pulsating type of de-icer.

The ordinary horizontal- and dive-bomber version, usually the Ju-88A series, groups its four-man crew tightly together in a section forward of the wing's leading edge. The pilot sits on the left, the bombardier alongside of him, but at a lower level, so that he can drop easily into the "Bola," an asymmetrical blister on the ship's right forward end.

In front of the pilot and bombardier is a multifaceted glass nose, which achieves a semblance of streamlining by the arrangement of glass in an all-magnesium spider casting. The windshield and top glass hooding are of similar construction. The radio-operator top-gunner sits in the rear of the cockpit, facing rearward, while the gunner's post is in the rear end of the bola, facing backward and protecting the belly.

The A-series Ju-88 has a wingspan of 65' 7", an overall length of 47' 1" and a standing height of 15' 5". It weighs some 16,874 pounds empty and 24,350 pounds for normal operation, With rocket-assisted takeoff, this load had been known to be boosted to 28,500. It is capable of a 281 mph top speed. while its cruising speed, with a normal operational load of 4400 pounds, is 213 mph.

Armament on the Ju-88 series varies with the individual modification and varies greatly from type to type. Generally, it consists of one semi-fixed 20-mm cannon in the nose, supported by either one 13-mm or 15-mm heavy gun in a flexible mount. This is sometimes supplemented by two flexible 7.9-mm guns. Two full-flexible 7.9-mm machine guns are mounted in the top rear section of the cockpit enclosure, piercing the glass in a sort of ball-and-socket arrangement. The belly gun position is either a twin 7.9- or single 13-mm installation. Adequate armor and bullet-proof glass are provided for all positions.

While the Ju-88 series began life as a medium bomber, used for horizontal bombing, the failure of the Ju-87 Stuka found the ship going into battle with venetian-blind dive brakes. From this series sprang an entire tribe of craft, covering in activity every phase of military use within the scope of this weight of aircraft.

The A series have all been powered by Jumo 211 liquid-cooled engines. Sub-types 1, 2, 9 and 13 were straight medium bombers, carrying a crew of four and having a standard 60-foot wing span. The A-3 was a dual-control trainer version of the A-1, one of the more widely used transitional aircraft in the Luftwaffe advanced training program. Sub-types A-4 and A-11 had a longer wing span (66 feet) and could be loaded to a maximum flying weight of 30,200 pounds with rocket-assisted takeoff. The A-5, 6 and 10 were for conventional takeoff operations with a gross weight of only 28,600 pounds. The A-7 and A-12, like the A-3, are also advanced trainers, but these have the 66-foot wing. The last of the A series is the A-14, whose bomb load has been increased to 8800 pounds. Its armament layout is similar to any typical German medium bomber, carrying one 20-mm cannon in a free flexible mount in the nose, one 7.9-mm machine gun through the front windshield, two 7.9-mm machine guns free in the dorsal position and a similar number in the ventral step below the fuselage. A few of the Ju-88, A-14 types observed is the P. An anti-submarine, ground attack type powered by Jumo 211A engines, it is similar to the A-4 but is reported to carry a heavy gun, probably a special 75 or 80-mm cannon.

The series B was an experimental unit, in which were adopted a greater wingspan and an all plastic nose, rounded off for better streamlining. Only a few of these were built, but much of the experimental data which went into the Ju-188, the successor, came from the B.

The entire C series were fighter conversions, usually used at night. The C-1, a three-place airplane, had its wings clipped to 60 feet. The C-2 and 3 have standard 66-foot wings. The C-3 and 6 are radar ships, with paneled-in noses, while the C-6 and 7 have eliminated the bola, and are powered by air-cooled BMW engines. The general armament for the C series is one to three fixed 20-mm cannons in the nose, supported by three 7.9-mm machine guns, one 13-mm machine gun in dorsal mount and either twin 7.9- or single 13-mm guns ventrally. The D series are straight photo reconnaissance craft, while the E is another experimental ship with a trick wing.

Ju-88Gs are specialized long-range fighters, powered by BMW engines. Their armament is like the C series. Little is known about the H other than the fact that it is a long-range reconnaissance plane with a special 55 foot fuselage and extra internal tanks.

The series P-1 to 4 are special anti-sub, boat and ground attack craft. These have been equipped with the Waffenbehalter, or streamlined container, which packs a full dozen 7.9-mm machine guns, set at a fifteen degree angle. Handy for ground strafing, they have also been used for hauling depth charges and torpedoes.

The series S planes are three-place reconnaissance bombers with the B series' streamlined nose. The last reported general sub-type is the T, which is the same airframe as the S but is powered by turbo-supercharged BMW 801G engines,

This is the Ju-88 tribe. While the ship is slowly being supplanted with the newer 188 designs, plenty of the predecessors appear to be in current production.

This article was originally published in the July, 1944, issue of Air Tech magazine, vol 5, no 1, pp 45-47, 78.
The original article includes 9 photos — one flight and 8 detail — and a labeled 3-view drawing (white on light blue, with black labeling.)
Photos credited to AAF Materiel Command, British Combine.