Question about Japanese air-units' operational range early WWII

[HJ Tulp]

I'm planning for a TL about the Dutch East Indies in WWII. What I'm wondering about now is the operational range for Japanese air-units. I can easily find the range of the different airplanes but is that the same as operational range?

For example for the Mitsubishi G4M I can find a range of 1,771 miles. I know that the Japanese planes had a very large range but this seems excessive. That would mean that from their airbase near Saigon they would have the range to bomb the great majority of SEA (Surubaya, Singapore, Rangoon etc.) and almost Kupang and Colombo! For the A6M2 what I can find is a range of 1,900 miles.

So what I would like to know is the actual operational range (or combat-radius if you will) of the Japanese Army and Navy air units. How close would a airfield have to be to Java to be 'in range' for the Japanese invasion plans? From Kendari (important airfield for operations against Java) to Surubaya is almost 1,200 miles. Is that closer to the truth?

 

[Carl Schwamberger]

Operational range varies with the mission/payload. ie: the USN SBD dive bomber was capable of carrying a 1000lb bomb, & usually did for strike missions. But, for scout missions a 500lb bomb was carried, allowing extra range & retaining a attack capability.

For the G4M Greens 'Famous Bombers' has for the Type 1 Model 24: Range with 968 imperial gallons 2,269 miles at a speed of 196 mph at 9,000 feet.

I am assuming statute miles is indicated here, vs nautical miles. Also a full bomb load of four 550 lb bombs = 2,200 lbs

Altitude is important in determining mission range. The 9,000 feet altitude given above was a typical attack height for the G4M with bombs.

 

[fastmongrel]

Commonly maximum range is calculated with maximum fuel and zero or very small payload. Combat radius or Operational range with a useful war load is usually about a a quarter to a third of maximum range. Combat Radius with maximum war load is usually about a fifth (or less) of maximum range. Japanese planes often looked very long ranged but they didnt break the laws of physics they sacrificed things other airforces considered vital to get the range. Also as Carl said above altitude makes a big difference, if the Japanese had to fly at 20,000feet or above the range would go down.

 

[CalBear]

The Japanese raided Wake Island from Kwajalein in the Marshall Island, a roughly 1,450 mile round trip using G3M. At the end of the war, the IJN was planning to conduct a large airborne commando attack on Tinian using converted G4M in a transport role. While a one way mission the flight distance would have been ~1,500 miles.

The Japanese, with some regularity would attack Tinian from Iwo Jima (1,450 mile round trip). In one notable attack in November 1944 the IJN conducted a 12 aircraft strike using A6M flying at extremely low level to avoid radar (low enough that one aircraft sustained damage when a propeller blade struck a wave). A6M routinely made 1,200 round trips during the Solomon campaign (these missions were not considered to be successful by pilots due to severe fatigue).

IJN aircraft had incredible range, at the expense of survivability.

 

[Carl Schwamberger]

.... Also as Carl said above altitude makes a big difference, if the Japanese had to fly at 20,000feet or above the range would go down.

As the US 8th AF repeatedly proved. The 9th AF or 2d Tactical AF could consistently knock down tiny bridge spans from under 15,000 feet. From 23,000 the B-17 or B24 could not hit a five acre factory roof consistently.

 

[fastmongrel]

From 23,000 the B-17 or B24 could not hit a five acre factory roof consistently.

I came across a quote once "The 8th Airforce precision bombed area targets and RAF Bomber Command area bombed precision targets". Even with GPS, Lasers and Computers modern airforces still regulary miss the correct target.

 

[CalBear]

I just realized I forgot to actually suggest something useful to the OP rather than some specific on individual raids -

When calculating actual combat range/radius it a useful rule of thumb to reduce the stated maximum by between 20 and 40%. This allows for fuel usage spent on the ground waiting to take off, spent forming up into formation, and for weather/navigation issues (WW II aircraft couldn't climb over serious weather which forced them to fly around heavy squalls or thunder storms). Fighters tend to take the biggest hit since their max range tends to be on super lean, low throttle configurations that have to be abandoned when in combat, with the resultant major impacts on usable range.

Overall additional impacts on range can also include the selected flight path of a strike. It is generally a poor decision to make a straight line point A to point B attack profile. The enemy knows what the threat axis is and will tend to ensure the more direct routes are much more heavily defended (this was, in part, why Allied bombing raids, especially unescorted raids, against Germany tended to avoid direct flights across France, instead looping out over the North Sea before turning into Germany towards the eventual target (often with a few feints thrown in for good measure).

 

[HJ Tulp]

Thanks for your input guys!

I'm now realising that my question is more doctrinal than technical. You see, in my TL there will (probably) be far less (if any) airfields in the DEI outside of airfields. These airfields were barely defended OTL and served as ideal stepping stones for the Japanese invasion. As the TL will have barely any butterflies on the British Empire until 1940 there will still be airfields to capture in Malaya and North Borneo.

So what I'm really asking is what the Japanese saw as sufficient coverage for their invasion fleets and if they would find the bases on North Borneo sufficient to cover the Makasar Straight.

 

[Carl Schwamberger]

I came across a quote once "The 8th Airforce precision bombed area targets and RAF Bomber Command area bombed precision targets". Even with GPS, Lasers and Computers modern airforces still regulary miss the correct target.

Very true. I don't know details for the 2d TAF. Have read about the 9th AF wrestling with the accuracy problem. during 1943 the 9AF was put through a really rigours navigation and attack training. They found early on a lot of the assumptions from tests and training in the US were wrong. The really critical factor in getting decent accuracy was attacking from lower than 15,000 feet. Frustrated attack leaders were putting in their post attack reports that they were dropping from 10,000 or less to ensure they did not have to com back to the same bridge or railway repair shop later that week. I've run across a few cases where bomb runs as low as 1,500 feet were claimed by 9th AF aircrew.

 

[Carl Schwamberger]

...

So what I'm really asking is what the Japanese saw as sufficient coverage for their invasion fleets and if they would find the bases on North Borneo sufficient to cover the Makasar Straight.

Were they dependent on fighter escort in these attacks?

 

[CalBear]

Thanks for your input guys!

I'm now realising that my question is more doctrinal than technical. You see, in my TL there will (probably) be far less (if any) airfields in the DEI outside of airfields. These airfields were barely defended OTL and served as ideal stepping stones for the Japanese invasion. As the TL will have barely any butterflies on the British Empire until 1940 there will still be airfields to capture in Malaya and North Borneo.

So what I'm really asking is what the Japanese saw as sufficient coverage for their invasion fleets and if they would find the bases on North Borneo sufficient to cover the Makasar Straight.

The DEI was the underlying reason the Japanese attacked in 1941. Oil was the major goal, but so was other resources ranging from rubber to palm oil. If necessary, they would have sent the Kido Butai into the region or simply stair stepped, building rough airfields as the went, which was what they did across the South Pacific IOTL.

 

[Carl Schwamberger]

... building rough airfields as the went, which was what they did across the South Pacific IOTL.

That worked as long as all weather fields were not needed, and the construction battalions were following the schedule. In the autumn they tried to establish some supporting fields for the Guadalcanal & new Guniea campaigns. Problems developed and construction slowed to a inadequate pace.

 

[CalBear]

That worked as long as all weather fields were not needed, and the construction battalions were following the schedule. In the autumn they tried to establish some supporting fields for the Guadalcanal & new Guniea campaigns. Problems developed and construction slowed to a inadequate pace.

True, but the Japanese offensive into the DEI was in Southern Hemisphere high summer and before the monsoon.

 

[HJ Tulp]

Were they dependent on fighter escort in these attacks?

OTL they were. However, thinking about it I realized that in ATL this would be (far) less necessary as without Dutch airfields there will not be be Dutch fighters to escort against. Will the Japanese risk relying on unescorted bombers as they move south? OTL there were secret Dutch airfields on Borneo the Japanese knew nothing about.

The DEI was the underlying reason the Japanese attacked in 1941. Oil was the major goal, but so was other resources ranging from rubber to palm oil. If they need to they would have sent the Kido Butai into the region or simply stair stepped, building rough airfields as the went, which was what they did across the South Pacific IOTL.

Oh I have no illusion that this will save the NEI in the long run. This is not even the main focus of the TL. In the end the Japanese will probably always get the NEI with a POD in the Netherlands. Either they succeed in their first attempt or they realize they have underestimated the task and resolve the matter using a sledgehammer aka the Kido Butai.

This will change things though. If they send in the Kido Butai then it will not be used somewhere else and it's rate of attrition could be higher. If they have to build airfields it will take time. Do you have any idea how much time?

 

[Zheng He]

As a general rule, I usually take a commonly listed range and use 1/3 of that for a useful combat radius although depending on what I am doing it may be longer or shorter depending on the bomb load or whether or not an auxiliary tank has been added.

I also recommend reading up on some of the OTL missions that took place to see how far planes actually flew. For example, I've found examples of SBDs with 500 pound bombs flying missions as far out as 300 miles.

 

[marathag]

To find out what aircraft can carry, look at empty and maximum take off weights. the difference is payload.
with that, you can add fuel and other engine fluids, crew, weapons/amount of ammo, and bombs

With some digging, you can find out internal fuel carried: it's around 6.5 pounds a gallon for the maximum fuel load, and with more research, how much fuel is burned per hour in cruise
then some math, and you can guestimate range.
To do it properly, you need the flight 'computer' or Slide Rule the Flight Engineer or pilot had

 

[Carl Schwamberger]

...

With some digging, you can find out internal fuel carried: it's around 6.5 pounds a gallon for the maximum fuel load, ...

Don't forget your temperature adjustment.

 

[eltf177]

In his autobiography SAMURAI Saburo Sakai mentioned he and his fellow pilots spent a lot of time practicing adjusting fuel mixtures to get maximum range without stalling.

 

[HJ Tulp]

As a general rule, I usually take a commonly listed range and use 1/3 of that for a useful combat radius although depending on what I am doing it may be longer or shorter depending on the bomb load or whether or not an auxiliary tank has been added.

I also recommend reading up on some of the OTL missions that took place to see how far planes actually flew. For example, I've found examples of SBDs with 500 pound bombs flying missions as far out as 300 miles.

Yeah I think I'll use 600 miles as the range in which the Japanese think they can comfortably command. 1/3 of the range of the G4M Betty is 590 but I think they would make do. Of course missions at a longer range are a given.

This means that the capturing the British airfields at Sarawak will be sufficient to cover most of the operations on Eastern Borneo (Tarakan, Balikpapan) and the Western Java Sea. From Davao the landing at Menado (if it would take place ATL) would be covered as well.

After that decisions will have to be made though. An airfield at Balikpapan would solve most of the problems for the operations against Java and possible landings on southern Celebes. It doesn't help operations in the Molluccans and Timor though.

To find out what aircraft can carry, look at empty and maximum take off weights. the difference is payload.
with that, you can add fuel and other engine fluids, crew, weapons/amount of ammo, and bombs

With some digging, you can find out internal fuel carried: it's around 6.5 pounds a gallon for the maximum fuel load, and with more research, how much fuel is burned per hour in cruise
then some math, and you can guestimate range.
To do it properly, you need the flight 'computer' or Slide Rule the Flight Engineer or pilot had

Don't forget your temperature adjustment.

Ok I'll forget about doing a ATL if I need to do all this

 

[vizzer]

If they're operating from captured or newly constructed airstrips how are they supplied?
Aircraft, aircrew, mechanics & spares can be flown in but it's not very efficient to fly in bombs or fuel.