according Naval Aviation Combat Statistics..
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ACTION SORTIES - Number of planes taking off on a mission which eventuated in an attack on an enemy target or in aerial combat, or both. This basis of tabulation was the number of planes of one squadron taking off on the mission. If any of these planes had action, the entire squadron's planes on the mission were counted as action sorties, including abortive planes, planes which reached the target but did not attack, and planes which escorted or patrolled but did not engage in combat. Thus if 16 VF took off as escort, 2 returned early, 2 engaged in combat, and 4 strafed, all 16 were counted as action sorties. Likewise if 8 planes took off for CAP, and only 2 engaged in combat, all 8 were action sorties. On the other hand, if 8 VF took off for escort, and none engaged in any sort of attack or combat, then none were counted as action sorties, even though they reached the target, and even though the escorted bombers attacked the target. Likewise, CAP planes missions, none of whose planes engaged in combat were not counted as action sorties.
LOSSES OF OWN AIRCRAFT - Loss data have come primarily from two sources: (1) action reports, squadron and ship, covering losses from all causes on missions involving actual combat with the enemy, and (2) loss reports, covering losses from all causes whatsoever.
The losses on action sorties reported herein have been taken primarily from action reports, in which the exact cause of loss can be determined more accurately. Two major exceptions to this practice may be noted: (a) losses on unreported or poorly reported combat missions have been added from loss report sources; these may sometimes be inflated, because of a tendency in the early loss reports to ascribe to "combat" or "enemy aircraft" losses whose cause was unknown; (B) aircraft listed in action reports as seriously damaged rather than lost, and later indicated in loss reports to have been scrapped or jettisoned because of this damage; these have been added as losses on action sorties.
Losses other than on action sorties have been taken from the loss reports, with some confirmation from carrier and squadron reports. The accuracy of loss reports, particularly with respect to cause of loss and date of loss, is frequently debatable, and many adjustments have been made where indicated.
LOSSES ON ACTION SORTIES - Includes all planes counted as action sorties, which failed to return to a friendly base or were destroyed in landing at base plus planes returning and later destroyed because of damage sustained during the mission, plus planes lost on unreported missions which apparently involved action with the enemy. All loses on action sorties have been classified by cause under the three categories Enemy A/A, Enemy A/C, and Operational. Where the exact cause was not given in the action report (planes reported missing) the cause most likely under the circumstances of loss described was arbitrarily assigned, or if the circumstances were not stated, the cause stated in the loss report was assigned.
LOSSES ON OTHER FLIGHTS -These are limited to losses, during each month, of planes assigned to squadrons which reported engaging in action against the enemy during that month. For these squadrons these figures represent all operational losses of airborne planes, on missions not involving action against the enemy; they include also planes later stricken because of operational damage sustained on such flights.
LOSSES ON SHIP OR GROUND - These figures are also limited to losses, during each month, by squadrons reporting action during the month. For these squadrons they included all losses, regardless of cause, of planes not airborne at the time of the loss, or at the time the damage was sustained that ultimately resulted in the loss of the plane. Principal causes of these losses included: struck by aircraft landing, taking off or taxiing, or by automotive vehicles; explosions and fires; storms, typhoons; enemy bombing or strafing or suicide attacks on carriers; own gunfire. It should be noted that all losses of grounded aircraft to enemy action are not included (some such losses were of aircraft assigned to pools or to squadrons not in action) nor is the greater part of the listed losses on ship or ground attributable to enemy action. The carrier losses in this category, however, do include all carrier planes lost in enemy attacks on carriers.
It should be noted, in connection with all categories of loss, that the figures for carriers represent all losses in active carrier combat operations (excluding strictly patrol and escort operations) in Pacific combat areas, while the land-based figures represent the bulk of, but not all, the losses of squadrons in active combat areas.
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'A/A' loss and 'A/C' loss in 'To Enemy' seems including scrapped, jettisoned and ditched planes which damaged by each enemy type.
'Operational' loss, it seems lost through fuel exhaustion or navigational errors or other pilot error or mechanical failure 'ON ACTION SORTIES', for example, crashed by losing engine power during combat missions - not by enemy but with action sortie.
and In the situation presented in main topic, Corsair engaged the enemy a/c.
so it's 'ON ACTION SORTIES' and 'To Enemy A/C' loss or 'Operational' loss.
if cause of the ditch is combat damage = 'To Enemy A/C' loss
if cause of the ditch is a pilot's mistake or mechanical failure(not by enemy) = 'Operational' loss