Yak-9U Overview Quite possibly the most under-rated aircraft in the game, the Yak-9U is a very capable and dangerous opponent in the hands of a decent pilot.  Excellent low level performance, maneuverabilty to match, plus a host of less tangible advantages in good vision, small size, and no-WEP worries combine to make this a real contender.  The biggest knock, and likely the reason it isn't more popular, is a perceived lack of firepower, though honestly it is nearly the same as most late 109's and better than more popular early 109's.  This is a wonderful little plane and well suited to most arena battle so if you are looking to fly something a little less common and still very capable, maybe the Yak-9U is for you.

Yak-9U

Engine Performance

The Yak-9U is tailored more to medium-low level work, having an absolute top speed of 415mph at about 16.5K and a top speed at sea-level of 355mph.  Unusually, the Yak-9U does not have WEP, instead achieving all these numbers without artificial extra boost.  With no danger of overheating, the Yak-9U can basically run all the time at full power and stay within 1-2mph of all aircraft except the absolute low altitude speed demons.  You never have to worry about running out of WEP, which can be a serious issue in many aircraft.  If not for WEP in other aircraft, the Yak-9U would be tied for 4th fastest plane in the game at sea-level.  A short climb to 6.5K and the Yak can cruise at 393mph, which is awesome.  Fuel duration is 28 minutes at full power which would normally be a little short but fuel never seems to be a problem in the Yak-9U.  Climb rates are very respectable, over 3,700ft/min at low level and retaining over 3,100ft/min at medium altitudes.  Given the quick climb, excellent transit speed, and no abuse of WEP, the fuel range of the Yak-9U is suprisingly long.  Acceleration is only average at low levels so make sure you keep your speed up and don't rely on acceleration to get you out of trouble.

Firepower

If there is a knock against this plane, firepower is likely it.  I think people expect a little too much. While they accept two 7.7mm + a 20mm in a 109G2 then can't accept two 12.7mm + 20mm in a Yak-9U.  I mean, the Yak-9U has virtually the same hitting power as a 109G6 or G10  (twin 13mm + 20/30mm cannon) that aren't packing the 30mm spinner gun (which is cool but very difficult to use against a maneuvering fighter).  Unfortunately, in the case of the Yak-9U there is less ammunition, 120 rounds of 20mm plus 170 rounds for each 12.7mm.  That puts the 12.7mm ammo at about half the typical amount available to a 109 with 13mm.  This means you need to make your shots count by getting in close and landed a solid burst of fire, not fire away at long ranges hoping to land hits.  This is where most Yak-9U pilots have the most difficulty spray-and-pray is simply not feasible.  The concentration of fire is very good though, the 12.7mm are cowl mounted and the 20mm spinner mounted, giving a nice convergence-issue-free cone of fire. Setting convergence out to D650 is typical though shots at that range are not all that likely to inflict serious damage or even land significant hits, usually a range more in the D275-D500 zone is used.  The Yak-9U isn't the best deflection shooter though, lacking the volume of fire of some aircraft for that purpose.

Maneuverability

The Yak-9U weighs in at only 7,000lbs, about the same as a Spit IX, which is very light.  For comparison, the P-51D comes in at 9,600lbs at typical load.  I find the Yak-9U has very good flying qualities, allowing wide speed changes without serious impact on handling.  Comparing the Yak-9U to the 9T version is not at all fair, the 9T is poorly balanced and often a bit of a handful to control.  The 9U simply feels more stable and direct, responding to the controls much more accurately and with confidence.  High speed handling is excellent with speeds in excess of 550mph being no problem with almost no loss of controllability or evidence of compression related issues.  High speed turn is excellent and even low speed turn isn't all that bad.  You won't out-turn a Spitfire, but you will scare the pants off any average turner you meet without having to resort to the use of flaps for temporary turn-rate enhancement (like in a P-51).  Roll rate is very responsive at all speeds.  Overall, the plane gives nice direct control and is a quality gun platform.

Flying the Yak-9U

The best use of the Yak9U is going to be where you can get set up for a short tail chase because of the relatively weak deflection shooting potential.  You only need a second or so in a good firing position and hold it for a second or two.  The 20mm and 12.7mm will do the job pretty quickly but not instantly.  A BnZ type role is good and probably preferred over slashing style attacks that would benefit from more cannons.  Your very good speed may also allow you to sneak up on people at high speed, firing at very short ranges with almost instant results.  Don't be afraid of chasing people lower as the Yak-9U retains excellent performance right down to the wavetops.  The rear view is also excellent and you should never miss detection of any enemy behind you.  I also find the Yak-9U an excellent rope-a-dope plane, zooming easily, reversing quickly, and then racing down

Defensively, the 9U has great speed and you should try to maintain that whenever possible.  The best operating altitudes for the 9U tend to be lower than a number of other planes (it is clearly a low-mid alt fighter) and you will find lots of people try and jump you from above.  Having good speed will help in your defense or escape.  You should be able to exploit a weakness of other planes though since you tend to have at least one advantage against most planes, though sometimes it might be only slight.  You are fast, dive well, can turn well at high speeds, and are small which makes you tough to hit.  Use all of that to your advantage.  Only a couple of aircraft should be able to stay with you in one of those aspects.  You should be able to create overshoots if you can effectively make high speed maneuvers with long paths that the opponent cannot follow.  I've used a large barrel style roll in the past which often causes minor overshoot, or at least closes the distance so that you can try to create overshoots more easily.  The Yaks small size makes it easy for an enemy to mis-judge distance and end up closer than they expect, which aids in the ability to get overshoots.

To beat it

The Yak9U is a deceptive target, typically maneuvering quickly and darting around.  This makes it a tough target for most types of shots since it slips through your grasp so easily.  The Yak also seems to attract a crowd of higher quality pilots who can appreciate the differences the Yak offers over some other planes, this tends to make most Yak pilots at least slightly better than average.   I'm never surprised when I see a Yak9U that defends itself well.

Overall you should always be concerned about a couple of key features of the Yak9U when trying to deal with one.  They are fast, and likely you cannot catch them at points of poor performance.  Driving them lower usually suits them just fine as engine performance improves and they are good divers.  The 9U is also small and nimble making for a hard target.  What I usually notice is that the Yak appears to be further away than it actually is.  This relates to the fact that the wingspan of the Yak is more than 5ft shorter than a Spitfire or P-51.  This makes judging distance on the Yak more difficult so be careful about getting too close or not realizing you are already in firing range.  The Yak has outstanding roll performance at high speeds and can combine that with instantaneous turn to make any tracking solution all but impossible for long.  The Yak is always at full power too since it does not have WEP so you know you will always have your hands full with one.  Finally, the Yak has excellent rearward views so it is unlikely you can sneak up on one effectively unless you are at the low 6 position.  The armoured glass behind the pilots head is very good at allowing unobstructed views to all areas to the rear not blocked by aircraft structure.

Offensively, you need to corner one as best possible and then try and land snapshots.  The chances of getting a good tail-shot are poor and even with longer ranged guns the small Yak can be tough to hit.  Most often they are rolling and darting from side to side so it's best to get in as many hits as you can.   The Yak is not usually considered fragile though I'm not sure if this is because it is tough to hit, or actually relates to the amount of damage it can absorb.  I tend to consider them a little bit tougher than something like the P-51.  Always be mindful of the unintentional overshoot.  It's not usually that the Yak slows down for you to overshoot, but often will make large displacement maneuvers to extend it's flight path and cause you to overshoot on a more direct path.  Always watch for that as once you are infront of a Yak 9U your odds of long term survival are not great.

Defensively, you want to avoid diving.  The Yak can likely dive at least with you and remain controllable up to your maximum speed.  The Yak 9 doesn't seem to compress or suffer from anything until it hits Mach buffeting but by that time you are likely in the depths of a similar situation so haven't gained much.   Also, diving takes the Yak9U down into it's "wheel-house" where it performs best.  As in the case of many Russian rides the Yak9U is best at lower altitudes so don't try and drag it low to escape unless you know you have a clear speed advantage.  Also remember that while you may have WEP to give you a brief speed advantage, the Yak doesn't rely on WEP and once yours is gone he may have the opportunity to catch you.  The Yak9 is small and it can be tough to judge closure but you may be able to force gross overshoots if the Yak has dove a long way or is packing a lot of speed.  The firepower on the Yak isn't terribly great in hitting power or range so if you can stay outside about D500 you are making his aiming job pretty tough.  I wouldn't be too worried about the instantaneous snapshot of the Yak9U, it is fair but the ammunition load doesn't typically allow a pilot to take these types of shots very often for fear of running out of bullets.

A final note, the Yak9U is a tough plane to beat and often is flown by above average pilots.  I never underestimate them and neither should you.   Against most of the typical opponents in the arena the Yak 9U is going to have at least parity in some flight aspect to anything else.