To be successful

The Bf109F-4 is a good fighter and quite misunderstood.   While people often relate all 109 variants to performance like the late models, especially the G10, this one is nimble and can quickly suprise unwary opponents.   It's more than 400lb's lighter than the G2 which gives a tremendous advantage in sustained turn-rate and all areas of handling.  Putting the guns in the nose made them much easier to aim and the upgrade to the Mg151 from the MGFF gave better ballistics.

The engine power is a little weak against most opponents you will face but is still pretty good.  Climb rate tends to be better than many aircraft though and is well sustained right up to high altitudes.  Top speed is a little low at most altitudes so you aren't likely to find yourself being able to pursue or retreat from most opponents if a straight chase. Acceleration is good though and the WEP lasts a long time so maximum use of WEP is not usually a problem.  WEP is a key too, the 109's all have long lasting WEP and it significantly adds to their performance but that comes at the price of increased fuel burn rate.

Maneuverability is very good and certainly the class of the 109 field (though the E tends to feel about the same).  I think the extra power of the F model allows it to sustain better turn rates than the E while the instantaneous turn is also good at speed.  Roll rate is a little weak and can be exploited by good rollers so be careful.  Speed really affects handling on most 109's though the F-4 is quite forgiving until you get to high speeds in excess of about 425mph at which time the roll and pitch become barely effective.  Still, the F-4 can give a lot of good turners a real run for their money and if someone underestimates you as a G10 you are going to shock him with your great turn rate.

The firepower of the F-4 is pretty average by 109 standards and not all that great, although the packaging is good.  The nose mounted Mg151 has 150 rounds which is pretty good, and being mounted directly infront of the pilot it tends to make aiming easier.  Convergence is not an issue and the cowl guns can be set out to the maximum of D650.  The cowl guns are not very effective though, being small calibre, and once you are out of cannon rounds you should pretty much consider reloading before attempting to attack anyone else.  The option exists to add 2 more 20mm cannons on gondolas on the wings if you want to increase your firepower.  While this is an aggressive upgrade that almost triples your firepower it also has a cost in terms of speed and maneuverability.  On the F4 the costs are managable but I usually don't recommend taking the gondolas unless you are expecting to have to take a lot of crossing or snap-shots, or will be attacking bomber (for which they are a must).

Your greatest advantage is the fact that a lot of people are going to think you are flying a 109G10, something that turns more like a dumptruck in heavy configurations (which lots of people fly).  Instead, the 109F4 is very light and can give even a Spitfire a bit of trouble in a turn-fight at medium speeds.  As speeds get slower the Spitfire will start to enjoy more advantage so try and keep to a comfortable 250-350mph range.  You will need to take shorter ranged shots or keep in tracking situations for a little longer than with a multi-cannon plane but the F4 has the turn-rate to maintain position for periods of time that should be long enough.  Top speed is not great so plan your exits from fights a little earlier and use your good climb rate and long WEP duration to maximize the lenght of time you can stay at maximum performance.

To beat it

The F4 can be slippery, it has some decent power and acceleration.  It climbs pretty well and turns ok too, plus packs a reasonable amount of speed though can't be considered a real speed demon by any stretch.  The cannon is effective so you don't want to give him close-range snapshots or any sort of tracking shot if you can help it because no planes in AH can really stand up to 20mm hits for long.   The 20mm Mg151 is not great at distance like the hispanos though so anything over about D550 is a fairly difficult shot against any sort of maneuvering target.

To identify the F4, look for the yellow tail (rudder) and relative lack of nose art (in the form of shaped or yellow bands).  The F4 can be a difficult plane to identify quickly and as such can leave you thinking it is a less maneuverable version only to prove you quickly wrong.  It you can, try and also identify if he is packing gondolas or not.  The gondolas vastly increase the firepower at the expensive of maneuvering and speed.  You don't want to get in the sights of a 109 packing gondolas as the 3 cannons can quickly ruin your day.

To defeat the F4 you need to quickly identify it and then not get into turning fights unless you are in a very good turner.  The F4 can easily turn with planes like the P-51 at most speeds and cen even give Spitfires a problem until the fight slows down.  The top speed is generally a little low though so you can probably expect you can have a speed advantage at most altitudes if you keep your speed up.  Take any shot you can on a F4, they are not terribly tough and have a tendancy to lose elevators, ailerons and the rudder.  Never Head-On attack one unless you think you can break off before you get too close and know he doesn't have gondolas.   This 109 doesn't have the option to pack a 30mm cannon so when only armed with one 20mm (and no gondolas) you can often win a HO engagement but you need to break off and let longer ranges guns (hispanos or multiple 50's) do there work from long range (D800) and then break off before he retaliates at short range (D400).

To defend against a F4 you need to exploit either a superiority in speed or maneuverability, as most planes will have one or another.   Typically a speed advantage is more likely if you are flying planes like the P-51.   The F4 does not perform well at high speeds, especially those in excess of 450mph where it can become all but uncontrollable.  If you have a F4 diving on you try and increase the speeds to the point where it will force him to pursue you at speeds over 500mph.  At those speeds the only thing a 109 driver can attempt is recovery because the controls will be locked up in what can become a terminal dive.  Always try and keep the firepower of the 109 at arms length, the 20mm cannon can hurt and has a good amount of ammunition but it tends to take a lot of time before enough rounds can be fired to kill an opponent.  Aiming is very easy for him though as the guns are center mounted and convergence will never be an issue.  If you hear the small cowl guns hitting you don't dive lower as that is likely where the 20mm's are passing.  If you can sucker the 109 into an overspeed dive though, over 500mph, you pretty much ensure your ability to escape as the 109 will be fighting to just regain control.  Always remember that the 109's all share fairly poor views from the cockpit with lots of frames in the windows that obstruct vision.  if you can slip into these blind spots you might not be noticed.