Since when could the Bf 109 be considered inferior to Western Allied fighters?

During the first six months of 1941, Fighter Command lost 57 aircraft compared to some 20 German losses. Despite the cost, offensive operations over France continued in an effort to relieve the pressure on the Russians by tying down German aircraft in the West.

Towards the end of the year, the first squadrons with ex-patriate Allied personnel began to form.
Language difficulties, and the fact that, to open the throttle the lever was pushed forward - the opposite to most continental aircraft - led to a spate of early accidents until pilots became used to their new mounts. One welcome improvement to the Spitfire arrived in the form of a diaphragm-operated carburettor for the Merlin engine which solved the problem of the engine cutting out under negative.

 

" Hawker Hurricane " by Edward Shacklady

Battle of Britain

When the battle opened at the beginning of July...

Seventy-two percent of all Hurricane pilots had seen combat , compared with twenty-six percent of the Spitfire pilots.

Moreover, the Spitfire was still in advance of universal maintenance standards in Fighter Command, with the result that during July and August only eight airfields in No 10,11 and 12 Groups were fully equipped and competent to repair a category 1 damaged Spitfire. This imposed appreciable limitations on the deployment of Spitfires, as well as inevitably influencing pilots of slightly damaged aircraft in their choice of landing grounds.

 

During the Battle of France and Battle of Britain in 1940, RAF pilots discovered a serious problem in fighter planes with Merlin engines, such as the Hurricane and Spitfire. When the plane went nose-down to begin a dive, the resulting negative g-force would flood the engine's carburettor, causing the engine to stall. German fighters used fuel injection engines and did not have this problem. So in action, a German fighter could evade a pursuing RAF fighter by flying a negative g maneuver which the RAF plane could not follow

 

You are correct to point out the acceleration and high speed of the G or K. This power was added to a smaller airframe than the Spitfire and these variants were hard to fly and did not handle particularly well except in a straight line. The biggest threat to the aircraft was its (poorly trained) pilot on take off or landing.

The F was a good match for the Spitfire V and outmatched the Spit II, early Yaks and I-16s in 1941. The Gustav was faster, but inferior to the Spit IX and P51 at most things it tried to do. The Spitfire IX and P51 were very clean designs which retained energy in manouvres. In combat flight simulation, three or four merges would provide the Spit or P51 with an energy advantage over the late war Me109s - unless flown by a really good pilot/player. In WW2 combat few dogfights were decisive. Most aircraft were shot down by an enemy they never spotted. In air battles team work mattered as did numbers. In the historic simulations a good squad with Me 109G could beat a weaker squad with Spit IX or P51. Over the skies of France and Germany the Luftwaffe was outnumbered and its pilots were under trained.

By 1942 the Me109 was really the Luftwaffe's second choice fighter. The Fw190 was designed as a "troop horse" to the mid 1930s Me109 "thoroughbred". The Fw190 was a better low altitude fighter, more heavily armed and armoured and handled better landing and on the ground. By late 1944 the Me109 was the Luftwaffe's third choice fighter after the Me262 and Fw190.

 

The pilot's skill level and aggression level was damn near everything! If the aircraft were reasonably close in capabilities then only two things mattered: the pilots and who had the better tactical advantage.

Superior numbers didn't always confer an advantage. In 1944 Eric Hartmann, after sending his young wingman out of danger, took on 6 P-51s. Hartmann was able to survive because: 1. The P-51s got in each other's way. 2. The P-51 pilot's poor shooting skills. 3. Hartmann's superior aircraft handling. He finally had to bailout due to running out of gas. Unlike many other instances, the US pilots did not strafe him in his chute. Saburo Sakai in a similar encounter, bested an equal number of Hellcats and even managed to down one. This, with only one eye!

 

It is interesting as the Ju87 planes for the German carrier as I remember had fuel tanks.

 

The Ju-87C had extra internal fuel tanks, the later Ju-87E had the extra tanks + 2 drop tanks.