Japanese Aircraft Online Model Contest 013

Wednesday, 30 October 2019

CINCPAC - CINCPOA Translations - Attacking Large Bombers Pt. 1

The next document, in three parts, is detailing ways to attack and shoot down heavy bombers and the results when Yokosuka and 301 Kokutai put these ideas to the test. A very rare and historically important document.


Source: Captured on SAIPAN.
Subject: Experiment and research on Methods of Attacking Large Bombers. Fragmentary document; undated; issuing authority unidentified, but this mimeographed reference work may possibly have been issued by the YOKOSUKA Naval Air Group.
Editor's Note:
This document was discussed at considerable length in CINCPAC-CINCPOA WEEKLY INTELLIGENCE, Vol. 1, No. 16, 27 Oct 1944, pages 28-32, and is reproduced here in full because of its value as a discussion of fighter tactics. 


                                                    (First Report) 
Attacks with Forward-Fixed Guns 
I. Object
To establish the most effective method of attack with forward-fixed guns, on armored, fireproofed, heavily protected large bombers.
II. Results and Comments 
A. Suitable methods of attack. 
1. Basic methods of attack.

a. Steep overhead (TN: Lit: from above & astern) attack. 
A steep overhead attack (angle at instant of firing:70°- 45°; firing range: 600 to 300 meters) is most effective and little damage is sustained by the attacking plane. It is considered the most suitable method of attacking large planes. Its advantages are as follows:
(1) Percentage of hits is good. For the reasons stated in paragraph (2), (3) and (4), a high percentage of hits is characteristic of this method.
(2) The approach and attack are simple; their essentials can he grasped by an inexperienced pilot with only a short period of training. 
(3) Execution of the attack is seldom affected by the enemy's formation at the time he is sighted or by his changing course during your approach.
(4) Errors in sighting, especially in firing range, are slight. 
(5) Since the relative angles of attack and breakaway are large, little damage is suffered from enemy defensive fire.
See Appendix #1 for essentials of the attack.
b. The effectiveness of the head-on attack, made from almost directly ahead (within 10° left or right and 15° above or below the enemy plane's line of flight; firing range 800 to 300 meters), is relatively great, and maneuvering for the attack is easy. This is considered a good method of attacking large planes.
See Appendix #1 for essentials of the attack. 

c. Firing with sights. The advantage of deflection (angle) firing ( ) are as follows: 
(1) Although deflection (angle) firing has the fault of making errors in the firing angle at once produce errors in deflection, it has little effect on errors in firing range. Because it is direct sighting, sighting errors are small, and the percentage of hits is higher than with deflection (amount) firing (). (2) In the overhead approach especially, the firing angle is large, producing some error in its calculation; but bullet drift is small, so from the practical standpoint the method is advantageous and there is no further need for consideration of it.
See Appendix #3 for the details of deflection (angle) firing. 

1. Attacking large planes provided with escort fighters. 

a. A combat air patrol (JOKU CHOKUEI TAI) is divided into a diversion unit (YUGEKITAI) and a bomber interception unit (BAKUGEKIKI GEKITSUI TAI).

b. The diversion unit will vary with the number of planes of each side and with the situation, but generally includes sixteen planes. It engages, checks and destroys enemy escort fighters, and gives indirect cover to the bomber interception unit.
The bomber interception unit usually consists of eight to sixteen planes. It avoids combat with enemy fighters and forcefully attacks and destroys enemy bombers. When necessary, the bomber intercpetion unit is divided into two parts, one concentrating on attacking the bombers, the other becoming a direct escort unit for the first.

c. Although it is preferable for the diversion unit and the bomber interception unit to be in strength when the number of planes on both sides is large, the optimum number is 32 planes, otherwise confusion in the air will result.

d. The diversion unit mast engage the enemy escort fighters before the bomber interception unit begins its assault. When the diversion unit is in strength, it is sometimes preferable to have it accompany the bomber interception unit to ensure coordination.

e. If a coordinated attack is executed by having a part carry out a frontal attack while the greater part makes an overhead assault, it gives the enemy no time to prepare and is very effective.

B. Improvements in armament.
In an overhead attack using 20 mm Mark II MG's (target speed being 250 knots), the deflection will be 9° 47' for the firing angle of 70° and range of 600 meters; or 7° for the firing angle of 45° and range of 300 meters. Because it is difficult to aim with the present sight and armament, the following is required:
1. Manufacture of sights with a good field of vision below and in front.
2. Elevation of MG's and sight at least 5° from the plane's longitudinal axis to improve the field of vision below and in front during firing.

C. Study of various methods of attack. 
1. If a stern attack from below is executed properly, it gets very good results with slight risk of damage. This attack requires great skill and will be difficult to execute unless by a pilot well practiced in the maneuver. 
2. The steep frontal attack and the side approach are not only difficult to execute and rather ineffective, but the risk of being damaged is great.

III. Summary of Fxperiments.
A. Participants
YOKOSUKA Air Group:       16 Zero fighters, 2 RAIDEN 
301st Air Group:                     16 Zero fighters, 2 RAIDEN
IV. Results
1. Essentials of basic approaches: Appendix #1
2. Attacking in formation: Appendix #2 
3. Deflection (angle) firing: Appendix #/3 

Appendix #1
Essentials of Basic Approaches against Large Planes
I. Head-on Attacks from Above and Below
A. Essentials of execution.
1. Angle of attack
2. Firing range: 800-300 meters
3. Deflection (Angle) firing:
The deflection is as shown in the annexed tables
4. Recovery
Whether attacking head-on from below or above, you should fly on opposite course, just clearing the enemy plane. If necessary, slip off to one side quickly to get out of the effective range of the enemy's guns. In doing this your angular speed relative to the enemy plane will be very great, rendering the enemy's fire ineffective. 
When a second approach is necessary after recovery, you must stay 1000 meters or more laterally from the enemy plane (outside the effective range of his guns).

B. Precautions 
1. There is a general tendency toward increasing the firing range. You should pay attention to the determination of the firing range, in order to avoid long range firing. During the experiments made by the YOKOSUKA Air Group, errors were made in estimating the 1400 meter maximum (TN: firing) range and 1000 meter maximum breakaway range. 
Because gunnery training has been carried out with sleeve targets, the firing range against real targets becomes excessive, as the target seems larger and the tension of actual combat predominates. Consequently, a medium attack plane should usually act as the target for photo-firing or simulated attacks. Or permanent targets the size of a large enemy plane may be laid out on the ground, so that planes returning from gunnery practice can make simulated strafing attacks. In any case, there must be a refinement in the judgment of firing range. 
2. To roll and turn directly in front of the enemy plane during your breakaway, while concentrating on the next approach, is very dangerous. This is because your angular speed in relation to the enemy plane is very small during a turn, and because your plane appears to be at a standstill for a moment. You present a large target to the enemy gunner, and cannot see his plane yourself; in other words, you're a fine target. Furthermore, during training the chances of a crash in mid-air are great.
3. When executing deflection (angle) firing during a head-on approach from above or below, it is easy to err in the direction of deflection, so care is required. 
4. In a concentrated attack the SHOTAI should be slightly more open than in patrol formation and should send in its four planes on successive attacks from directions differing by a small angle. 
II. Overhead attack. 
A. Essentials of execution. 
1. Approach and turn.
Your lateral distance from the enemy plane when making a frontal approach with an altitude advantage of 800-1000 meters should be small. When the target appears below and in front of you at 30° to 40° (target speed 250 knots), roll over with a half slow roll, keeping your sight on the target after the turn. If, imeediately after rolling over, you nose your plane down too much and withhold your fire, the target will then be beyond your guns, and the extreme difficulty of maneuvering to counter this will make effective attack impossible. On this account, it is necessary to keep the target in the sight from the moment of roll-over and to aim, maintaining a fixed lead. 
3. Firing range: 600-300 meters. 
Air speed is about 280 knots within firing range and about 325 knots at the break-away, but there is no need to fear for the strength of the airframe. (Air speed reaches 330 knots only after the plane has dropped 2500 meters following the roll-over, with the engine at full throttle. Terminal velocity is 340 knots.)
4. Leading your target and sighting. 
Although we rely on deflection (angle) firing, "leading" a target with the sight in present Zero fighters is impossible if the target speed is fast. Hence, the pilot's seat has been fully raised and your firing is sighted along the middle of the cowling. When this is done, the deflection is 6° - 7° (there is some variation depending on the fuselage).
5. Recovery.
When finished firing, continue diving to increase your angular speed to its maximum while within the enemy's effective firing range; then quickly retire out of effective range.
6. Repeated attacks.
After retiring out of effective range, nose your plane up slowly for another approach. With an altitude advantage of 5000 meters at a distance of 2000 meters, loop over and attack. If your lateral distance from the target is kept as slight as possible when starting your run, it will be easy to get lined up with the target's flight path and your attack will be facilitated.

B. Precautions.
1. Never make a flat diving attack. If you should fall behind the target after rolling over, give up the attack completely and recover as soon as you can. (Although it is better to continue diving after firing and then recover, a recovery above is possible when you still have considerable altitude advantage immediately after your roll-over, and when there is no fear of being under effective fire.) In attacks at an angle less than 45° your angular speed relative to the enemy plane is small, and the chances of your being damaged are great.
2. When holding your sight steady and making a persistent close-in attack, caution is required; your initial angle of attack must be good, or else it will rapidly flatten out as you close to firing range. You must concentrate on sighting and on the abrupt reduction in diving angle which accompanies your closing to firing range.
3. After rolling over and during your approach, you should constantly maintain the position you desire relative to the enemy. A "waiting attack" (MACHIUKE KOGEKI) is dangerous, since it is very likely to cause a mid-air crash.
4. A concentrated attack by a SHOTAI is rather difficult; consecutive strikes by BUNTAI at close intervals is more effective. In the formation for the latter approach there should be 30 meters distance between each plane, about 100 meters distance between BUNTAI, and about 300 meters distance between SHOTAI.

Reference data:
Observations made from a medium attack plane on an attack by 8 Zero fighters against 3 special training Type 96 land attack planes, 6-7 January 1944.
1. Overhead approach.
a. It is impossible to direct your MG's against a steep overhead approach, and firing with sights (SHOJUN HASSHA) is difficult as well. It is also difficult to fire on planes on opposite course and with an altitude advantage of about 1000 meters when they roll over, since they are at extreme range and will go into a steep dive immediately after rolling over. Because of the target's speed of movement gained from its fast dive, there is only a moment to fire lefore it breaks away.
b. It is easier to fire on those planes whose delayed run-in makes them fall behind or enter a shallow dive. Those who attempt close pursuit are similarly easy targets. In ceneral, the tailman ( ) of a SHOTAI has a tendency to be "pulled flat". 

2. Head-on approach.
During an enemy plane's approach from opposite course, its movement is slight, making it an easy target for the defending gunners. It is almost impossible, however, to fire on planes which continue on opposite course and recover above; they retire beyond firing range. It is easy to fire on planes which roll over in front of their target, especially on those which recover in inverted flight.

Appendix #2

Formation Attacks on Large Planes 
(Account of Experiments) 

I. Dates and Place. 
From 10 January 1944 to 13 January 1944. 
II. Personnel and Planes Participating. 
YOKOSUKA Air Group fighter personnel (16 Zero type carrier fighters) 
301st Air Group fighter personnel (16 Zero type carrier fighters)
III. Plan
A. Organization.
Force A    (9 Type 1 land attack planes 
                 (12 Zero fighters
Force B     20 Zero fighters
B. A combat air patrol of fighters would intercept some bombers with direct escort fighters (trying primarily to shoot down the large planes at one crack with a steep overhead approach), and the results of the attack would then be studied.
IV. Account and Comments. See annexed tables.
V. General Comments.
Since this experiment was carried out with a very small force and covered only one-phase of attack methods, there is still much room for further study. 

A. In addition to direct escort fighters, a strong diversion unit should be attached to the bomber interception unit.
B. The escort fighters should be disposed to provide protection against overhead attacks by enemy fighters approaching on opposite course. In addition to the usual direct escort disposition one unit (TAI) should be stationed 2000 meters in front and 1000-15000 meters above the attack plane unit.

Formation attacks on Large Planes (4 planes to a SHOTAI)
1. Formation Plan
Execute Weaving (BARIKAN UNDO)
2. Account
At 1310 the KISARAZU Air Group took off and gained altitude. The altitude of land attack plane unit was 2000 meters. The direct escort unit, taking position as shown above, proceded with a weaving maneuver.
The enemy was sighted at 1314, 6000-8000 meters distant.
When Force B's land attack plane unit attacked, Force A's direct escort unit had dropped too far back from its direct escort position to repulse the steep overhead approach of Force B's fighters in time. Although A's direct escort unit was directly above the land attack plane unit, the point where B's planes rolled over was 1500-2000 meters forward of it, so that A's planes were outdistanced and of no use in stopping the attack.
More study was needed on the disposition of direct escort units (cf. second trial). Since A's planes peeled off prematurely, B's patrol unit was late in assuming patrol formation. Tryout of a diversion unit in particular was impossible. (In the second trial, allowance was made.)

a. Some planes made shallow attacks because their roll-overs were poorly timed or executed too close together.
b. Whereas many planes did not get in the vertical plane of their target, they should have been as directly above and behind it as possible. CHUTAI and SHOTAI leaders needed more practice in the approach and run. (In selecting a target it is preferable to attack the wing-men first.)
c. Some pilots made poor recoveries. (They recovered by pulling out above.)
Break-away from the enemy after an attack should be rapid. (The superior speed achieved in the dive should be used in the break-away, so that the enemy direct escort fighters cannot jump upon you.)

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