"Welded drop tanks on Zeros" Topic

I understand that during the Guadacanal campaign Zero fighters carried external fuel tanks which were welded to the plane rather than conventional drop tanks. Does anyone know why this was done? I presume it is because drop tanks were too small but am not sure.

I understand that during the Guadacanal campaign Zero fighters carried external fuel tanks which were welded to the plane rather than conventional drop tanks. Does anyone know why this was done? I presume it is because drop tanks were too small but am not sure.

My thought would be that a jettisonable drop tank requires plumbing and a release that shuts off the plumbing when the tank is dropped.

If the planes were field modified for the tanks, they may not have had the hardware for safe jettison so they made them permanent by welding.

I do not believe this was the case. I have two references on Zero drop tanks during this period and they make no mention of such a practice.

A.I.2 (g) Report No. 2103, September 9, 1942, "Mitsubishi 00 ('Zero') Navy Single-seat Carrier-Borne Fighter", states:

"It appears that both metal and plywood external jettisonable tanks are in service. The following details have been given for three tanks (believed metal) presumably examined after being jettisoned from 00 Navy fighters."

The other document is the JOINT INTELLIGENCE SUBCOMMITTEE, WORKING COMMITTEE ON JAPANESE AIRCRAFT, PRELIMINARY REPORT ON JAPANESE FIGHTER PLANE PRODUCTION (Based solely on name-plate analysis).

APPENDIX TABLE "I" COMPONENT PARTS BY SOURCE OF MANUFACTURE

Type 0 Mark 1 and Mark 2 S.S.F.

Part No. 2085 Jettisonable belly tank, Supplier's Name – Nippon Kentstsu Kogyo and Osaka Arminiyumu, Zeke only

Part No. 2015 Jettisonable belly tank, Supplier's Name – Nippon Kenteysu Kogyo. Zeke only

Part No. -- Jettisonable belly tank, Supplier's Name – Hiro Naval Arsenal. Zeke?

I have come across accounts that said that because of a shortage of drop tanks some Japanese pilots would not drop their tank even after it was empty in order for it to be reused.

Ok, I was wondering about the "non droppable extra fuel tanks" included in the "Guadacanal The Cactus Air Force" scenareo book for Check Your 6

Not sure if I'm remembering this properly, but I think there were separation problems on the early model drop tanks, where they wouldn't drop off. Guadalcanal seems a bit late for this. They could also be A6M3 32s, which had shorter range and may have needed some drop tank fuel to get home (Rabaul was 600+ miles back thataway…).

Which scenario has this provision? I have some friends that I believe have that scenario book and I am very curious what is being portrayed. Or could you tell me what the time frame is for this particular scenario?

To add any wing tanks to the Zero means a major re-plumbing of the fuel system. It was done in 1944 for the bomb-armed A6M2 Zeros operating off of the carriers in the Battle of the Philippine Sea, but this was not a field modification. It may be possible to fit a larger centre-line drop tank to the Zero, but any larger tank would be constrained by the position of the inner landing gear doors and by ground clearance issues.

Scenarios F, G, J and K

I got a look at the Guadalcanal: The Cactus Air Force book. As you indicate, all the scenarios with the drop tank restriction are from August and September 1942. Note that in October the Japanese opened a new base at Buin so they could stage flights through there.

Now consider that the Zero drop tank carried 330 L and the internal fuel load of the A6M2 was 518 L. Fuel selection allowed the pilot to first use up the drop tank fuel and then switch to the internal fuel. It might be possible on the 650 mile flight from Rabaul to Guadalanal the drop tank was not yet completely empty and the pilots did not want to risk running out of fuel on the way home. That 650 miles was 34% of the 1900 mile range of the A6M2. The drop tank held 39% of the total fuel. If you plan to burn off fuel in combat over Henderson Field you just might not want to waste that last bit of gas in the drop tank.

The rule would read much more accurately as:

Drop Tanks: The long distance from Rabaul to Guadalcanal meant that the Japanese A6M Zeros risked fuel starvation if they jettisoned their drop tanks before they were completely emptied. Use the special Drop Tank A6M Zero Move Chart in this book for these aircraft.