Overview from Soda's pages..
A rare aircraft to see in general play, the Ki-61 doesn't really have any type of consistent following. Nothing really stands out in terms of aircraft performance though so that is probably why it is the least common IJN plane to see. The lack of any one positive attribute is also probably the reason the Ki-61 remains a little obscure, but possibly it could also be a bit of a hidden treasure. The Ki-61 does have a couple of things going for it overall in high speed handling, stability and firepower, which I believe a lot of people don't realize.
Ki-61-I-KAIc
Engine Performance
The Ki-61 is a low-medium altitude fighter and the engine performs best below 15K. Cruise speed at sea-level is only 305mph (313mph with WEP), increasing by a linear rate ( increasing by about 3.5mph/1,000ft of altitude gain) up to a maximum of 357mph at 14.5K. WEP adds about 8mph at most altitudes up to 14K. Speed obviously is not much of an asset and a bit of a liability to the Ki-61. Climb rate is also pretty poor, 2,900ft/minute at sea-level, decreasing sharply when over 13K. Acceleration tends to be equally, or more, disappointing and the Ki-61 tends to feel quick sluggish, even in a dive. Fuel range is 37 minutes on internal with the option to extend that by 26 minutes with a pair of drop tanks. Releasing a drop tank immediately and only packing one is often a good plan to extend range and not hurt cruise performance too much, although be sure to drop your other tank and adjust your trim before entering battle.
Firepower
Firepower on the Ki-61 is strong, with a pair of wing mounted 12.7mm machineguns and a set of twin 20mm cowl mounted cannons. This is opposite to the layout of most packages and is one of the strongest assets of the Ki-61. The important cannons, being mounted near the centerline, don't have convergence problems at any range though the ballistics tend to be a little different and take some time to get used to. The wing mounted machineguns offer a decent secondary weapon. Ammunition provided includes 250 rounds/gun for the 12.7mm and 120 rounds/gun for the 20mm cannons. This is not overwhelming but sufficient and about average. Snapshots, deflection, and crossing shots are all pretty acceptable though you need to ration your ammunition a bit. Unusually, since the cannons are cowl mounted, the Head-On of the Ki-61 is quite dangerous. Most planes have wing mounted cannons so the true firepower in a Head-On is likely to only be effective at closer ranges, while in the Ki-61 the cannons fire almost in parallel and thus if you get a feel for the cannons you can fire at longer ranges. I wouldn't recommend taking Head-Ons in the Ki-61 though, it is not a very tough plane and tends to take damage poorly.
Maneuverability
Maneuverability in the Ki-61 is not fantastic. The roll rate is very nice at almost any speed, and the turn rate is decent down to 200mph but not slower. The plane really seems to struggle at low or very high speeds for turn rate. At low speeds (200mph) it tends to become very heavy and have problems maintaining a good turn rate, though this is likely because of the lack of horsepower and about average weight (~7,600lbs). Sustained turn-fights are not terribly good. At high speeds (450mph+), the plane handles about average and really doesn't stand out. Top speed in a dive is about 500mph since the plane becomes quite heavy above this speed and difficult to control. By 550mph handling is poor and by 575mph the Ki-61 is almost unrecoverable. Roll rate is very good though, right up to the unrecoverable point.
Flying the Ki-61
The Ki-61 is really a BnZ'r that should leave the fight early if things appear to not be going it's way. It has such poor acceleration and climb that any sort of energy fight is unlikely to be successful. An average turn-rate at low speeds spells trouble against any of the advanced turners (Spit or N1K). The best speeds to fight are between 300 and 500mph. The cannons and heavy machineguns should provide a good snapshot capability for knocking out enemy planes with only quick bursts. Enter the fight slightly above the crowd and make diving passes on opponents. Don't get into chasing people as most will be able to easily out-distance you and it might draw you away from friendly help. You are likely to be faced with a number of opponents who can turn about the same or better than you, have equal or better speed, or both. Thus the basic requirement for an altitude and energy advantage to begin with. Look to pick off one plane at a time, then re-establish your energy, and go after another.
Defensively, the Ki-61 can be a slippery target and with the good roll rate you may be able to force overshoots. You will typically have to trade altitude for speed so you can defend but don't give up altitude too quickly. If you sink all the way to sea-level you are going to be at your worst performance altitude for top speed and have little in the way of defensively options. Use scissors to get people out-infront of you since the Ki-61 tends to roll well and turn at least average, good attributes for scissors. If you manage to create an overshoot you have enough firepower to finish the job quickly. Try and extend your fight if defensive and drag enemy planes towards friendly support if you can. Speed is key, keep it as high as you can maintain since that buys you time and makes you a tougher target.
Fighting the Ki-61
The Ki-61 can be very dangerous since it has more than enough firepower to knock you out quickly. They tend to arrive at medium altitudes and will be looking for lower opponents. One key can be to make yourself an unattractive opponent by staying out of diving range of the Ki-61, either through horizontal or vertical separation. A good Ki driver is not likely to squander a whole lot of altitude in order to get only 1 kill. A poor one may, but you can use that to your advantage too.
Offensively, drive the Ki low and try to keep him from building any energy back. The Ki really struggles to build energy since it is such a poor climber and accelerator. That means that constant pressure will require the Ki to either lose speed, or trade off altitude to maintain speed. The Ki also gets worse and worse as it gets lower and usually can't survive very long at sea-level. Look to land hits whenever possible, even if small calibre, since the Ki is not very tough and seems to take engine damage easily. BnZ from above and there is little chance the Ki can come up after you and will likely be driven down after each pass. Slashing attacks can also be very successful although you need to worry about the Ki turning to face you and trying to Head-On attack you. Don't accept Head-On attacks from Ki's, it's just too dangerous.
Defensively, try and simply speed away. Most aircraft hold a serious speed advantage against an Ki-61 so simply try and extend away. If you have altitude and a Ki above you, enter a shallow dive to build up speed. If the Ki dives on you, use that speed to defeat his guns pass and then continue to extend away from him. If you manage to avoid only 1-2 passes you have likely drained a lot of his energy reserves and may have build up more separation than he can close. The Ki is so slow that it should not be too difficult to escape unless you are also in a slow plane. Don't let the Ki get good quality close in shots, or fly in straight lines away from one thinking you are outside of cannon range. Ki's tend to be pretty desperate and will take shots at almost any range or angle where there is even the slightest hope of success.
Shanes evaluation is spot on. There IS a small contingent of 61 pilots here that are quite dangerous, tho it is uncommon to see one.
Have you tried the zero's yet ??
Go here:
http://www.icongrp.com/~stagemon/ah/Mitsu's sound pack, Soda's A/C pages and tons of stuff..
Ya old goat..
