AEG’s first fighter design was the D.I, a short single-bay biplane of mainly steel tube construction under a fabric covering. A notable feature of the D.I was the use of single-spar wings. Three prototypes were built, and the first of these appeared in May 1917. Type testing took place later in August and September after the fuselage had been lengthened by 1 ft 3 ¾ in (0.4 m). The second and third prtotypes (D 440/17 and D 5002/17 respectively) differed by having cheek-type radiators, those of the D.III being longer than those of the D.II. The D.I proved difficult to fly, and one of the prototypes crashed during testing. Nevertheless, 20 pre-series examples of the D.I were ordered for front line evaluation with the standard fighter armament of two 0.312in (7.92mm) LMG 08/15 fixed forward firing machine guns with a synchronisation system to allow them to fire through the propellor disc. The contract was cancelled after the loss of a second prototype in a crash on 5 September 1917.

Type: 2 seat biplane fighter
Engine: Daimler D.IIIa inline, 160hp
Wing span: 27 ft 10.5 in / 8.5m
Length: 20 ft 0.5 in / 6.1m
Height: 8 ft 8.5 in / 2.65m
Wing area: 173.73 sq.ft / 16.14 sq.m
Empty wt: 1510 lb / 685 kg
MTOW: 2072 lb / 940 kg
Max speed: 137 mph / 220 kph
Climb rate: 2 min 30 sec to 3280 ft (1000m)
Armament: 2 x fixed 0.312 in (7.92mm) LMG 08/15 forward firing machine guns

The C.IV was a twin-seat biplane aircraft primarily fielded as reconnaissance platform from 1916 onwards though it also served as a bomber escort and saw service with the German air service through to the end of World War 1in 1918. The C.IV represented one of AEG’s most successful wartime ventures with production exceeding estimated 658 examples.

Designed by Georg König and a little larger than the C.III, the C.IV was a conventional biplane which introduced the D.III engine, a fixed forward firing machine gun for the pilot, and a three position variable incidence tailplane (ground adjustable). The wings featured and equal span upper and lower wing assembly with double bays and parallel struts. The wing main structure was welded steel tube, including main spars of 40mm tubes, with wooden ribs which were fabric covered.

The engine, a single Mercedes D.III water-cooled in-line type of 160 horsepower – was mounted in the extreme forward portion of the fuselage with the distinct radiator “horn” protruding the top. The engine powered a two-blade wooden propeller. The forward portion of the fuselage was contoured to an extent, producing a somewhat aerodynamic look while the rest of the body maintained a boxy-like appearance. The fuselage was a primary box structure of welded steel tube decked on top with plywood and covered at the sides and bottom with fabric.

Seating was for two, made up of the pilot and an observer in tandem, with the pilot in the forward cockpit behind a simplistic windscreen. The pilot had access to a single Spandau machine gun offset to his right side. The system was synchronized to fire through the spinning propeller blades without damaging them via an interrupter gear. The observer manned the rear cockpit, facing aft, and sat inside of a Schneider-type gun mount ring. His position was dominated by a Parabellum machine gun with adequate traverse to engage trailing enemy fighters. The J.1 version carried an extra machine gun firing backward and downwards at 45 degrees.

Over 900 lb of armour plate protected the crew and other vital parts.

The undercarriage remained fixed, characterized by the two large main landing gears at front and a simple tail skid under the tail section. The empennage featured a sharp-angled vertical tail fin with low-mounted horizontal stabilizers.

Performance was good for the time with the C.IV yielding a top speed of 98 miles per hour with a service ceiling of 16,404 feet. Endurance from the Mercedes engine was reported to be roughly 3 hours of flight time.

The C.IV entered service with Germany in early 1916 during the spring season. By June of 1917, no fewer than 150 examples were operating along the Western Front alone. The mount proved a success for the time it was fielded and several models continued in service after the cessation of hostilities. An estimated 400 C.IV and C.IVa models were constructed by Fokker factory at the Schwerin.

The C.IV was produced in two other lesser-known variants designated as C.IVa and C.IV.N. The C.IVa distinguished itself from the base model by fitting an Argus engine of 180 horsepower. The C.IV.N was the prototype form of a C.IV night bomber developed sometime in 1917 with increased span three-bay wings. The night bomber form was powered by a single Benz Bz.III series engine of 180 horsepower and would have carried 6 x 110lb bombs externally.

The C.IV was used by the air forces of Bulgaria (which declared war on Romania in September 1916) and Turkey (engaged in war from 1914, but most Turkish Flying Corps aircraft flown by German pilots).

The C.IV was also fielded by Poland in the years following the war (at least 64 examples).

C.IV
Engine: Mercedes D.III 6 cyl inline, 160hp
Wing span: 44 ft 1.5 in / 13.45m
Wing span: 44.16ft (13.46m)
Length: 23.46ft (7.15m)
Height: 10 ft 11.75 in / 3.35m
Wing area: 419.81 sq.ft / 39 sq.m
Empty wt: 1764 lb / 800 kg
MTOW: 2469 lb / 1120 kg
Max speed: 98 mph / 158 kph / 85kt
Cruise speed: 87 mph / 140 kph
Climb rate: 6 min to 3280 ft (1000m)
Service ceiling: 16,405ft / 5,000m
Endurance: 4 hr
Max range: 348 sm / 560 km
Seats: 2
Armament: 1 x fixed 0.312 in (7.92mm) LMG 08/15, 1 x trainable 0.312 in (7.92mm) LMG 14 Parabellum mg.

C.IVa
Engine: Argus inline, 180 hp

C.IV-N
Engine: Benz Bz.III, 150 hp
Wing span: 15.3m.
Bomb load: 6 x 110 lb (50 kg) bombs.

Following the C.II, an experimental C.III designed by Georg König introduced a deep fuselage filling the gap between the biplane wings to allow the crew a clear forward view over the upper wing. Seating the pilot aft gave the gunner a clear field of fire forwards. No production of the C.III was undertaken.