[Don Boose]

Karol –

Garry hit the main visual differences. Here are all the externally visible differences among the main production variants of the G4M.

Early Model 11: Smooth nacelles with exhaust stacks at the top of the nacelles (Kasei Model 11 engines), dorsal blister immediately behind the crew compartment, waist gun bulged sponsons, squared off angled wing tips and vertical stabilizer, tail cone with narrow slit.

March 1942: Kasei Model 15 engines. No visible external differences.

March 1943: 30mm thick rubber sheet laminated to lower wing surface as a self-sealing measure, addition of prop spinners, visible engine exhausts, and truncated tail cone. This was the Mid-Production Model 11. Some aircraft had flame dampeners added to the exhaust stacks at the top of the engine cowlings.

August-September 1943: Longer exhaust stacks, V-shaped tail cone. This was the Late-Production Model 11.

G4M2 Model 22: Newly-shaped nacelles with individual exhaust stacks (Kasei Model 21 engines), four-bladed propellers, redesigned wings with thicker airfoil and laminar flow that retained the rubber laminated layer on the underside, larger horizontal tail, rounded wingtips and tip of vertical stabilizer (this was a cosmetic change to make it easier for ground crews to recognize the difference between the Model 11 and the Model 22), power rotated nose cone, additional nose glazing, two additional 7.7mm guns one on either side of the nose, waist gun sponsons replaced by flat windows. An optically flat panel was installed, changing the shape of the nose. Some were fitted with bomb bay doors, but these were later removed.

During production, other changes were made, including redesigned waist windows and armament variations.

G4M2A Model 24: Kasei Model 25 engines – engine cowlings with a separate carburetor intake at the top front of the nacelle, bulged bomb bay doors now standard. Otherwise visually indistinguishable from the Model 22.

Model 24 Tei had the bomb bay doors removed and were fitted to carry Ohka suicide rocket glide bombs.

G4M3: Internal wing redesign, but the only external differences were small wing root filets, no rubber pads on the under surfaces, 20mm (vice 7.7mm) waists guns, and a completely redesigned tail turret similar to that of the B-17E or B-26 and dihedral on the horizontal stabilizers.

G6M1-L transport aircraft looked pretty much like Model 11s with no slit in the tail cone, no underwing rubber, and fairings over the bomb bays.

I'm also reposting the Mark Styling drawings from Sam Tagaya's book, Mitsubishi Type 1 Rikko ‘Betty’ Units of World War 2, Oxford UK: Osprey Publishing, 2001.

Sam Tagaya and Mark Styling concluded from the photographic images of the wreck that 323 (built in March 1943) had the spinners and truncated tail cone, but no rubber under the wings and no exhaust flame dampeners.

I’ll be glad to have anyone with greater knowledge fine-tune this. I haven’t tried to capture all the internal changes or field modifications, just the things that would be visible on a 1/100 model.

Don