Neptune wrote:

AIP wasn’t planned back when this design was being made. First design was ready in 1977 (that was just an improved Zwaardvis), yet the second design, with many revolutionary improvements like Mk48 torpedoes, Subharpoon, TAS etc. Was only ready by 1986. The second design won and became the Walrus class.

The biggest problem of it all, was that the Royal Netherlands Navy decided to give the go-ahead to RDM in 1979… So the design was far from finished. In 1979 the keel for the first of the class was laid, yet they soon found out that all kinds of new calculations and design features had to be done. They even had to make an entire mock-up of the engine room and command post!
Normally she would be ready in 1985, yet in 1982 they already shifted that date by 3 to 4 years.

I have read this text on Dutch fleet forum (with help of babelfish of course 😉 ), but not sure if all info there is correct:
– the date 1986 of finishing development of Walrus class IMHO means date when all changes and additional demands of KM were included
– in some other sources have read the date 1982, which is IMHO more realistic for the original second design (compared with first less evolved design finished in 1977)
– this also support first expected date of testing the Walrus in 1985
– also the thing with 1:1 mock-ups, not sure if this had to do something with delays in development, mock-ups are often used in develpment stage

Those 3 flank arrays on your pics are for sure TSM2225 (DUUX-5).
But dutchsubmarines mentioned also one other flank array:

The Walrus-class has an ahead looking sonar, a 24 element single line flank array and a towed array. It also has three hydrophones spaced along both the port and starboard sides for passive ranging.

TinWing wrote:

In retrospect, it would have been advisable to repeat the Zwaardvis class design. However, the Walrus class was originally intended to be a 6 unit class. A mid-1980s RDM proposal lead to the cancellation of the last two units in favor of the smaller, more exportable Moray class.

This is completely new info to me. Never heard that KM wants Moray class.

Of course, the Walrus class was nearly reduced to 3 units when the lead ship of the class was badly damaged by fire while under construction. The damage amounted to more than $100+ million, a huge amount by the standards of two decades ago. The Dutch government of the day considered scrapping Walrus, but eventually decided to pay for the repairs – which seems outrageous because the sub was still in the hands of the builders when it burnt.

Well, now I am completely confused, see this info found on Dutch fleet forum few days before (crude babelfish translation):

Still during the development and construction of the first walrus class onderzeeboten in 1983, the RDM were found by a bankruptcy. Datzelfde year by the company in an adapted form herstart were made, as a result of which construction could continue still. During this whole development – and construction project has been within the DMKM (Executive Board materially royal Navy) a large wisseling of staff and also talk has been of personeelstekort. Expertise had be built and experience had be obtained as the project progressed. The bezetting of the project team became thus by some sneering compared to “a wheelbarrow full jumping frogs”. staff problems binnenin a project where a complete new and technically sophisticated design had be developed thereby also once more parallel ran to the construction of the first onderzeeboot (with all daily bay heavy rings to let go that to the work), upheavals their stamp on all people concerned. Many have shown thereby an extraordinary commitment and in spite of the overload which they felt they quality centrally the end product for eyes has nevertheless always loved. Beside all these problems this construction project was also once more charged with supply problems. Thus pale the supplier of the wheel automat to its obligations satisfy to be able and bankruptcy did not go. These were vervolgens ordered at another supplier, who had start the development and production of the wheel automat on that moment still to. It is, however, clear that apart from the cost increases which were the consequence of technical modifications in the design particularly the costs which the consequence was rapidly of the delays lanes. How longer a ship stays in building on the yard, all the more expensive it becomes. The second serial of two onderzeeboten was already given in august 1985 in task. These ships had been intended as substitutes for the second serial driecylinder onderzeeboten (HrMs tuna and cachalot). Initially it the intention was these placing order just in the course of 1986, but by advancing KM this wild the overlevingskansen of the new RDM larger makes. A third serial of two onderzeeboten, in substitution for the swordfish class, was incorporated in the plans for 1991. Until excess of calamity break during the run-down of the first onderzeeboot of this class on 14 augusts 1986 fire. In spite of a thorough research was possible cause the exact and also the exact place where the fire broke out never is retrieved. It is suspected that the fire has arisen at the wasplaats – corporals and manschappen by a failure to provisional electrische work reduction or by direct contact of of the construction lamps with a poetsdoek. The financial impact of this fire (fl 125 millions) was covered by the building insurance, which has conducted later to drastic premium increases of new Navy ships to build.

:confused: