J2M Raiden weight/load

[Tojo2]

I have a question about the '搭載量' for anyone knowledgeable in Japanese and aircraft terminology. I am just using google translate but in '5_J2M_table.jpg' the note at the bottom seems to say the tests were performed at "全備重量 (Full Weight)". Meaning for the J2M2 including the "Useful load" 2348kg + 862kg "搭載量 (Useful load)" = 3210kg "全備重量 (Full Weight)" Does that exclude things like bombs and external fuel? So would the 3210kg weight only be internal things like guns, ammo, internal fuel etc? Or also including external things like bombs and drop tanks?

Chat GPT said "搭載量 does include external stores, unless the document explicitly says otherwise." To me that would make sense as to the lower speeds and climb seen on this paper as opposed to US numbers. But I really don't have the knowledge to make an informed guess like that. Any help understanding this is appreciated.

 

[warbirdperformance]

Hello. "全備重量" can be translated as "gross weight", and usually external equipment is not included.
When carrying drop tank or bomb, it is called "過荷重量" (overload weight).
The word "搭載量" may include external things. But "搭載量" for "全備重量" does not include bombs or drop tank.

The U.S. figure is just an estimation and based on the early Japanese planned performance.

I hope this would help you.

 

[mad_max]

I have this paperback book that may interest you on goggle drive; use the link to view it.


View: https://drive.google.com/file/d/1wh9uqq5F6Ppchw4vbBipVrNmSSoPCwn2/view?usp=sharing

There's also some other data I've collected through the decades; use this link for it.

J2M – Google Drive

drive.google.com

 

[Tojo2]

Are there some examples of this you can point me to that reference this terminology for gross and overloaded weights in Japanese?

 

[ThomasP]

Maybe check out the aircraft data plate for the A6M2 below, along with other Japanese data plates that can be found online. The aircraft data plates usually (always?) listed the 'self weight', the normal 'installed load, and the 'full weight load' AS THEY WERE INTENDED WHEN THE AIRCRAFT LEFT THE FACTORY. AFAIK later modifications (either in the field or at modification depots) were not normally indicated on the data plates. I have several scans of A6M series data plates and they show the increase in the 'self weight', 'installed load', and 'full weight load' over their production time frame.

NOTE: AFAICT NONE OF THE WEIGHTS INCLUDE THE WEIGHT OF THE PILOT. The weights of the pilot, his flight suit, parachute, life-jacket, and odd bits he carried with him on the mission do not appear to have been factored in. The Japanese considered the average pilot weight with flight clothes and parachute to be 165 lbs, but when I go through the 'installed load' weights there is no way I can get the weight of the pilot to fit with the values.

On the data plate ;

1. 自 重 = 'self-weight' or 'by itself weight' is the equivalent of the British TARE Weight (no pilot, fuel, oil, bombs, ammo, and no normally removable equipment (radios, gunsight, guns, dinghy, flare gun & flares, miscellaneous bits and pieces, etc) that might have to be changed or maintained between missions, and no equipment that might be expended (fuel, oil, ammo, bombs, flares, etc) during a mission.

2. 搭載量 = 'installed load' or 'payload' is equivalent to the British Removable Load or Weight. This includes radios, gunsight, guns, ammo, dinghy, flare gun & flares, fuel, oil, miscellaneous bits and pieces, etc (ie all the things left out of the TARE weight).

3. 全備重量 = 'full weight load' is the total of No.1 plus No.2, and is approximately equal to what they considered the load for a normal mission (ie full internal fuel & oil, guns, ammo, and all normal operational equipment).

Not on the data plate:

4. 過荷重量 = 'over weight load' you see in the manuals is the equivalent to the British Overload Weight, which would include additional fuel in DTs or special long range tanks, additional oil, maybe additional ammo, bombs (for fighters any bombs appear to be additional weight), etc.

For the A6M the weight of the DT and the fuel it contained would be added to the 'full weight load' to get the 'over weight load'. The same applies to any underwing bombs and such. Here is a data plate for the early-war standard (I think steel) 328L DT carried by the A6M2. I am not 100% sure, but I think the Japanese used 0.735 kg/L (6.13 lb/USgal) for the weight of their aviation gasoline. It was definitely more than the US value of 0.72 kg/L (6 lb/USgal). The 32.5 on the data plate is the weight of the DT in kg.