Flak Directional Arrows to Guide German Fighter Planes, WWII Tactical and Technical Trends, No. 22: April 8, 1943 (Lone Sentry)

a. General

When Allied aircraft approach behind cloud layers or out of reach of antiaircraft batteries, the Germans have perfected a method of "skywriting" a red arrow of bursting shells to point out their approximate direction and height to German interceptors. Red flak bursts have been frequently reported by pilots, unaware of its purpose, who were flying over occupied territories by day. The German instructions for firing this type of indicator have recently come to hand.

Although such a pattern itself has not been reported by pilots, red marker-projectiles are fired to form an arrow measuring 3,500 to 3,850 yards long. The "shaft" consists of four or five bursts spaced at about 700 yards, while six bursts form the "point." The arrow is almost horizontal, aligned on a bearing from the gun position to the approaching aircraft, and at approximately their height. (This may explain why the pattern has not been reported.) The arrow can be formed in from 5 to 15 seconds, and in calm weather lasts 3 or 4 minutes. Red practice ammunition is usually fired, but HE is used when other ammunition is not available.

b. Instructions for Firing Directional Arrows

(1) Instructions for Firing

Flak directional arrows are only fired if friendly fighters are aloft or in readiness, and if no hostile aircraft are in range of the gun position or likely to come into range shortly.

In accordance with a directive, flak directional arrows are also to be fired if hostile aircraft, flying above the clouds by day, can only be picked up by directional indicators, and are out of range of the flak. If friendly fighters are above cloud, the flak directional arrow must be fired at the height of the hostile aircraft. If these same fighters are below cloud, the flak directional arrow must be fired close beneath the cloud base.

(2) Firing Data

The height of the enemy aircraft is taken to the nearest 1,000 meters (approximately 3,000 feet), and a future bearing is obtained.

Two salvos each are first fired by three guns to form the "point" of the arrow, and then five (or, as the case may be, four) rounds by the fourth gun to form the "shaft."

(3) Procedure for Firing

(a) Preliminaries

At each gun, a table of quadrant elevation and fuze data must be provided for gun crew members numbers 1 and 6 (see table). Instead of tables, the data can be shown on the guns as follows: for No. 1, colored marks on the elevation scale, with corresponding height figures; for No. 6, data, in accordance with the table, painted on the left-hand side of the mounting.

Firing of flak directional arrows must be preceded by explanation and practice.

(b) Firing Drill

(1) The executive officer designates a primary gun for firing the "shaft." Taking the line from the gun position to the hostile aircraft, the firing of the "shaft" should be allotted to one of the center guns. As already stated, this gun has no part in firing the "point."

(2) Height and bearing are taken and called out. The executive officer takes height to the nearest 1,000 meters and calls it to the gun detachment commanders. He adds lateral deflection to the bearing; it should be about 350 to 400 mils. Future bearing is passed by the executive officer to the gun detachment commanders.

"Take post - aircraft 8 o'clock - flak directional arrow - height 4,000 (i.e. meters--14,500 ft) - primary gun "A" - bearing 6,300 (i.e., mils = approx. 354°) - fire."

No. 1 sets quadrant elevation for the height ordered (from his table) on the elevation scale. He reports, "No. 1 set." No. 2 sets the bearing ordered and reports, "No. 2 set."

With the 88-mm gun, models 18/ 36 and 37, No. 6 sets fuze for the height ordered (from his table) on the fuze-setting machine. When the fuze is set, the round is loaded at once. No. 3 fires on the order of the gun detachment commander.

With the 105-mm gun, models 38 and 39, fuzes for the height ordered (from the table) are set by means of two fuze-setting keys. No. 3 loads the first round on the order of the gun detachment commander.

Before firing the first salvo, the gun detachment commanders report "ready" to the executive officer after the required data have been set. The executive officer then gives the order "fire." Subsequent salvos, after the appropriate data are set, are fired as quickly as possible without further orders.

With the 88-mm (18/36 and 37), rounds must be fired at intervals of 2 seconds and with the 105-mm (38 and 39), at intervals of 2.5 seconds. Firing must be in the following order: 1st and 2nd salvos from three guns for the "point," followed by five or four rounds from the primary gun for the "shaft."

(d) Cease Firing

This is ordered by the executive officer as soon as he sees that fighters have recognized the hostile aircraft, or if hostile aircraft come into range. The appropriate order is: "Cease firing flak directional arrow." If this order is not given, firing of the arrow is repeated.

c. Firing Data Tables

(1) Tables for 88-mm, Antiaircraft Gun (18/36 and 37)

(a) Table for No. 6 (Fuze-Setting in Units from the Cross)*

Height   1,000 m     2,000 m     3,000 m     4,000 m   5,000-8,000 m

Arrow Point
   (1st and 2nd
   salvos) 180 230 290 330 340

Primary gun

   1st round 155 205 265 305 315

   2nd round 130 180 240 280 290

   3rd round 110 160 220 260 270

   4th round 85 135 195 235 245

   5th round 60 110 170 210 220

(b) Table for No. 1 (Quadrant Elevation)

Height Height

1,000 m = 15°
2,000 m = 23°
3,000 m = 30°
4,000 m = 37° 5,000 m = 43°
6,000 m = 50°
7,000 m = 55°
8,000 m = 60°

(2) Tables for 105-mm Antiaircraft Gun, 38 and 39

(a) Table for No. 6 (Fuze-Setting in Units from the Cross)

Height   1,000 m     2,000 m     3,000 m     4,000 m   5,000-8,000 m

Arrow Point
   (1st and 2nd
   salvos) 200 240 280 300 340

Primary gun

   1st round 175 215 255 275 315

   2nd round 150 190 230 250 290

   3rd round 105 145 180 205 245

   4th round 80 120 160 180 220

(b) Table for No. 1 (Quadrant Elevation)

Height Height

1,000 m = 15°
2,000 m = 20°
3,000 m = 25°
4,000 m = 32° 5,000 m = 38°
6,000 m = 43°
7,000 m = 48°
8,000 m = 53°

*Fuze-lengths are measured in degrees from a cross or zero mark; e.g., on the fuze-setting key. The German fuze scale reads from 0 to 350, the numerals being reference numbers which indicate definite times of flight.