Article: Battle of Britain
Section: Fighters

Question: What is the test service unit known as?

The "Luftwaffe"'s Messerschmitt Bf 109E and Bf 110C fought against the RAF's workhorse Hurricane Mk I and the less numerous Spitfire Mk I.
The Bf 109E had a better climb rate and was faster than the Hurricane Mk I, depending on altitude.
In spring and summer 1940, RAF fighters benefited from increased availability of 100 octane aviation fuel, which allowed their Merlin engines to generate significantly more power through the use of an Emergency Boost Override.
In September 1940, the more powerful Mk IIa series 1 Hurricanes started entering service in small numbers.
This version was capable of a maximum speed of , some more than the Mk I.
The performance of the Spitfire over Dunkirk came as a surprise to the "Jagdwaffe", although the German pilots retained a strong belief that the 109 was the superior fighter.
The British fighters were equipped with eight Browning .303 (7.7mm) machine guns, while most Bf 109Es had two 7.92mm machine guns supplemented by two 20mm cannons.
The latter was much more effective than the .303; many German planes landed despite large numbers of .303 hits.
At some altitudes, the Bf 109 could outclimb the British fighter.
It could also engage in vertical-plane negative-"g" manœuvres without the engine cutting out because its DB 601 engine used fuel injection; this allowed the 109 to dive away from attackers more readily than the carburettor equipped Merlin.
On the other hand, the Bf 109E had a much larger turning circle than its two foes.
In general, though, as Alfred Price noted in "The Spitfire Story":The Bf 109 was also used as a "Jabo" ("jagdbomber", fighter-bomber)—the E-4/B and E-7 models could carry a 250 kg bomb underneath the fuselage, the later model arriving during the Battle.
The Bf 109, unlike the "Stuka", could fight on equal terms with RAF fighters after releasing its ordnance.
At the start of the battle, the twin-engined Messerschmitt Bf 110C long range "Zerstörer" ("Destroyer") was also expected to engage in air-to-air combat while escorting the "Luftwaffe" bomber fleet.
Although the 110 was faster than the Hurricane and almost as fast as the Spitfire, its lack of manoeuvrability and acceleration meant that it was a failure as a long-range escort fighter.
On 13 and 15 August, 13 and 30 aircraft were lost, the equivalent of an entire "Gruppe", and the type's worst losses during the campaign.
This trend continued with a further eight and fifteen lost on 16 and 17 August.
Göring ordered the Bf 110 units to operate "where the range of the single-engined machines were not sufficient".
The most successful role of the Bf 110 during the battle was as a "Schnellbomber" (fast bomber).
The Bf 110 usually used a shallow dive to bomb the target and escaped at high speed.
One unit, "Erprobungsgruppe 210" – initially formed as the service test unit ("Erprobungskommando") for the emerging successor to the 110, the Me 210 – proved that the Bf 110 could still be used to good effect in attacking small or "pinpoint" targets.
The RAF's Boulton Paul Defiant had some initial success over Dunkirk because of its resemblance to the Hurricane; "Luftwaffe" fighters attacking from the rear were surprised by its unusual gun turret.
However, during the Battle of Britain, this single-engined two-seater proved hopelessly outclassed.
For various reasons, the Defiant lacked any form of forward-firing armament, and the heavy turret and second crewman meant it could not outrun or outmanœuvre either the Bf 109 or Bf 110.
By the end of August, after disastrous losses, the aircraft was withdrawn from daylight service.