Up until 18 august, the german sortie rate sat somewhere below 1000 per day, give or take. After 18 august, the weather improved and with it the sortie rate for the LW. The average of 1,000 sorties per day was cracked 18 august and continued to be exceeded through to 6 September, with peaks of over 1,600 sorties on 30 and 31 August. This period saw the Luftwaffe continue the policy first seen on 18 August of attacking RAF bases further inland, and was the period in which the Germans came closest to victory. Correlating to this concentration on the sector fields was a decrease in RAF sortie rates, as might be expected. I haven't found a precise number on RAF sortie rates in this period, but some sources vaguely suggest an average of about 600 per day If correct, the RAF was turning aircraft around more effieintly than the LW given the much smaller size of FC.
In the earlier phase of the battle Tangmere was the only one of the crucial Sector Stations to be in a vulnerable position close to the coast, but the new deep penetration tactics used after 18 August saw the network of stations around London come under attack. The success of this phase of the German attack was partly accidental, in that they didn't know of the existence of the vital sector control rooms. If the control rooms had not been built at major fighter stations then this stage of the battle would have been rather less dangerous for the RAF, although the fighter stations and squadrons would still have come under severe pressure.
Although the first attack on the inland stations came on 18 August, a return of the bad weather prevented the Germans from returning in force until 24 August. This marked a period in which the Germans flew an average of 1,000 sorties per day, peaking at over 1,600 sorties on 30 and 31 August and lasting until 6 September. The gap saw two significant events. The first was a conference at Goering's palatial home at Karinhall on 19 August in which he repeated that the RAF was the Luftwaffe's main target. Enemy fighters were the first target, either in the air or on the ground, followed by the aircraft industry and the ground organisation of the bomber forces.
The second came on 20 August, when Churchill paid his famous tribute to the men of Fighter Command, remembered many for the line 'never in the field of Human conflict was so much owed by so many to so few'. What does still surprise is how early in the battle this speech was made - on 20 August the hardest part of the battle still laid in the future.
A key feature of this period of the battle was the repeated heavy attacks on the sector stations. North Weald was hit on 24 August, Biggin Hill twice on 30 August, Debden, Croydon, Biggin Hill and Hornchurch twice on 31 August. Biggin Hill was worst hit and the vital control room was knocked out of action. The staff moved to an emergency control room in an estate office in a nearby village, but this could only handle one of the three squadrons based at the airfield, so the remaining two were controlled from other sectors. 31 August also saw Fighter Command suffer its heaviest losses of the battle, with 38 aircraft shot down. The benefits of the RAF's 'home advantage' can be seen very clearly on this day. Of the 38 pilots shot nine were killed. Others will have been wounded and put out of action, but many were able to return almost immediately to the battle. In contrast very few of the crews of the 39 German aircraft lost on the same day will have escaped to fight again.
September started as August had ended. On 1 September Biggin Hill was hit for the sixth time in three days. Most of the buildings were now unsafe and most work had to take place outside, but the station somehow managed to keep working (largely due to the bravery of the WAAFs). Hornchurch was attacked on 2 September, North Weald on 3 September and Biggin Hill on 5 September. The aircraft industry also suffered. Vickers at Weybridge was hit on 4 September, Hawker on 6 September. The attacks also began to creep closer to London. On 5 September the oil farm at Thameshaven was hit and set on fire. The Germans returned on 6 September, and again during the raid on London on 7 September.
During 18 August 1940, Luftwaffe units flew a total of 970 sorties over Britain: some 495 by medium bombers, 460 by fighters and 15 by reconnaissance units. Of this total, about 170 of the bomber sorties were flown on the night of 17/18 August; the remainder were flown during the daylight hours on 18 August. Less than half of the available (or serviceable) aircraft on the
Luftflotte 2 and
Luftflotte 3 OBs were involved in the action that day, so it was clear that the Luftwaffe was not greatly extended in providing forces for the offensive. LF 5 did not take any part in the fighting, although its reconnaissance aircraft were active over Nthn England and Scotland
Altogether, the Luftwaffe lost between 69 and 71 aircraft destroyed or damaged beyond repair as a result of its operations over Britain on 18 August 1940. Of this total, 59 were lost to certain or probable action by fighters while two fell to ground fire, four to a combination of both and one collided with a British training aircraft. The remaining three crashed in German-held territory owing to technical failures. Altogether, the losses represented seven per cent of the force committed. Around 29 aircraft crashed in England. Personnel losses were 94 German crews killed, 40 captured and 25 returned with wounds. Some 27 to 31 German aircraft returned with damage.
The gross underestimation of Fighter Command's strength issued to Luftwaffe units meant the British reaction was much stronger than expected. During the 24-hour period, Fighter Command flew 927 sorties, slightly fewer than the Germans. Only 41 of these sorties were flown by night, 28 on 17/18 August and 13 on 18/19 August. The remaining 886 sorties were flown by day, a number almost exactly equal to the 861 serviceable Spitfire, Hurricane, Defiant and Gladiator day fighters available to squadrons.
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However, the average operational sortie rate of one per serviceable fighter was not spread evenly throughout the command, however. Nos 12 and 13 Groups in the Midlands and north of Britain, with a third of the serviceable fighters between them, put up 129 (or only 15 per cent) of the day sorties, and of these only three made contact with the enemy. No. 11 Group put up one-third of the serviceable fighters in 600 sorties, or more than two-thirds of the total; on average. Each of the serviceable Spitfires and Hurricanes flew 1.7 operational sorties. No. 43 squadron flew the most sorties: 63 operations including five each from the 13 serviceable at the beginning of the day.
Only 403 (45 percent) of the total number of sorties flown by Fighter Command were directed at the three major German raids. A further 56 (or just over 6 per cent) were standing patrols to protect shipping off the coast. Most of the remaining 427 sorties (nearly 50 per cent) were made to engage the reconnaissance aircraft. Usually several half-squadrons were committed. This was not excessive. But by sending more units to counter the flights, German aircraft were forced to fly higher and were denied the opportunity to drop to low altitude to take higher resolution photographs. This contributed to a lack of German intelligence which often failed to distinguish fighter, bomber and naval airfields from each other. Much of the time their strength was directed at non-fighter airfields on this date.
Of the 403 sorties put up by Fighter Command to meet the major German attacks, 320 of those made contact with the enemy, meaning 80 percent of the fighters sent to intercept the bombers did so. The percentage would have been higher, had the bombers on the afternoon raid not turned around short of their targets.
Between 27 and 34 RAF fighters were destroyed. One source of the battle indicated the figure to be 31 destroyed or beyond repair. Of these, 25 fell to German fighters, two to return fire from the bombers. One was shot down by British ground fire in error and the loss of the remainder cannot be established. Some 26 of the fighters lost were Hurricanes, and five were Spitfires. Personnel losses for the RAF amounted to 10 British fighter pilots killed on the day, and another who died of wounds. Around 19 pilots were wounded, 11 so seriously that they did not take part in the rest of the battle.
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Losses on the ground amounted to eight fighters (two Spitfires). Around 28 aircraft of other types were destroyed on the ground. The total destroyed or damaged beyond repair amounted to 68 aircraft, although 17 of these were trainers or non-operational types.
Perhaps the most dangerous aspect of this period of the battle was the slow but steady decrease in the quality of the British fighter pilots. As more experienced pilots were killed or wounded they had to be replaced with novices, many of whom would later become equally experienced, but that was in the future. The experienced squadrons were also becoming worn down, and under the Dowding system they were thus moved away from the battle and replaced with fresh squadrons. Unfortunately the intense nature of the battle in late August and early September meant that this policy failed. The inexperienced squadrons suffered much heavier losses than the tired units they were replacing, and in some cases had to be withdrawn themselves. But the system of squadron rotation meant at least that sortie rates would necessarily drop for the RAF as some of its units entered a rest period
On 8 September Dowding replaced the rotation system with a new 'Stabilization Scheme' (presumably because it was designed to stabilise the experienced squadrons). Fighter Command's squadrons were split into three categories. 'A' class categories were to be manned entirely with fully trained pilots and were to be used in No.11 Group and in the Middle Wallop and Duxford sectors of the neighbouring groups. Five 'B' class squadrons in No.10 and No.12 Groups were also to be kept up to strength and were to be used if an entire 'A' class squadron needed to be rested. The remaining squadrons, in every other group, became 'C' class squadrons. These had a core of five or six experienced pilots and were used to give new pilots enough experience to allow them to be moved to 'A' or 'B' class squadrons. At about the same time the number of pilots in each squadron was reduced from 26 to 16 - a move that in the short term allowed more squadrons to operate at full strength but at the price of eliminating each squadron's reserves, forcing just about every pilot to fly on every mission.
This period also saw an alarming trend in the number of fighters available to replace losses - the weeks ending 31 August and 7 September were the only two in the entire battle in which Spitfire and Hurricane losses greatly outnumbered the weekly output of new or repaired aircraft. Three more weeks at the same rate and Fighter Command might had run out of fighters, assuming it had enough pilots left.