Tuesday, January 26, 2016

Catalina - ASW

Catalina Flying Boat

Coastal Command - ASW
https://youtu.be/uTE-jHVIKJU?t=19m3s
Inside The Cockpit - Short Sunderland - MAH > .
Sub Chasers of the Civil Air Patrol > .
Why Aircraft Patrols Were a Source of Fear for Nazi U-Boats > .
Why Depth Charges Don't Have to Touch a Submarine to Sink It > .

Catalina - ASW

Other work by the Coastal Command's Operational Research Section (CC-ORS) indicated that on average if the trigger depth of aerial-delivered depth charges (DCs) were changed from 100 feet to 25 feet, the kill ratios would go up. The reason was that if a U-boat saw an aircraft only shortly before it arrived over the target then at 100 feet the charges would do no damage (because the U-boat wouldn't have had time to descend as far as 100 feet), and if it saw the aircraft a long way from the target it had time to alter course under water so the chances of it being within the 20-foot kill zone of the charges was small. It was more efficient to attack those submarines close to the surface when the targets' locations were better known than to attempt their destruction at greater depths when their positions could only be guessed. Before the change of settings from 100 feet to 25 feet, 1% of submerged U-boats were sunk and 14% damaged. After the change, 7% were sunk and 11% damaged. (If submarines were caught on the surface, even if attacked shortly after submerging, the numbers rose to 11% sunk and 15% damaged). Blackett observed "there can be few cases where such a great operational gain had been obtained by such a small and simple change of tactics".
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"The "exchange rate" ratio of output to input was a characteristic feature of operational research. By comparing the number of flying hours put in by Allied aircraft to the number of U-boat sightings in a given area, it was possible to redistribute aircraft to more productive patrol areas. Comparison of exchange rates established "effectiveness ratios" useful in planning. The ratio of 60 mines laid per ship sunk was common to several campaigns: German mines in British ports, British mines on German routes, and United States mines in Japanese routes."

http://www.feightstudios.com/navalasw.htm .
https://en.wikipedia.org/wiki/Operations_research .

Saturday, January 16, 2016

Martin JRM Mars


The Martin JRM Mars is a large, four-engined cargo transport flying boat designed and built by the Martin Company for the United States Navy during WW2. It was the largest Allied flying boat to enter production, although only seven were built. The United States Navy contracted the development of the XPB2M-1 Mars in 1938 as a long-range ocean patrol flying boat, which later entered production as the JRM Mars long-range transport.

The Glenn L. Martin Company scaled up their PBM Mariner patrol bomber design to produce the prototype XPB2M-1 Mars. The XPB2M-1 was launched on 8 November 1941. After a delay caused by an engine fire during ground runs, the aircraft first flew on 23 June 1942. After flight tests with the XPB2M between 1942 and 1943, she was passed on to the Navy. The original patrol bomber concept was considered obsolete by this time, and the Mars was converted into a transport aircraft designated the XPB2M-1R. The Navy was satisfied with the performance, and ordered 20 of the modified JRM-1 Mars. The first, named Hawaii Mars, was delivered in June 1945, but with the end of World War II the Navy scaled back their order, buying only the five aircraft which were then on the production line. Though the original Hawaii Mars was lost in an accident on the Chesapeake Bay a few weeks after it first flew, the other five Mars were completed, and the last delivered in 1947.

Four of the surviving aircraft were later converted for civilian use to firefighting water bombersIn 1959, the remaining Mars aircraft were to be sold for scrap, but a Canadian company, Forest Industries Flying Tankers (FIFT), was formed and bid for the four aircraft and a large spares inventory. The company represented a consortium of British Columbia forest companies, and the bid was accepted and the sale completed in December 1959. The four aircraft were flown to Fairey Aviation at Victoria, British Columbia, for conversion into water bombers. The conversion involved the installation of a 6,000 imp gal (27,000 l; 7,200 US gal) plywood tank in the cargo bay with retractable pick-up scoops to allow uploading of water while the aircraft was taxiing. The scoops allowed 30 tons of water to be taken on board in 22 seconds. Later some of the hull fuel tanks were replaced with water tanks.

Two of the aircraft still remain based at Sproat Lake just outside of Port Alberni, British Columbia, although neither are operational.

sī vīs pācem, parā bellum

igitur quī dēsīderat pācem praeparet bellum    therefore, he who desires peace, let him prepare for war sī vīs pācem, parā bellum if you wan...