[Stiebler]

U-boats sailing out of Bergen in late 1944 or 1945, in the NYGM mod, have been increasingly afflicted over several releases by sudden air crashes. The symptom is always the same: the U-boat is fitted with Tunis, is sailing on the surface, is attacked by a long-range bomber near the Faeroe Islands (where there is an airbase), and the U-boat gives a warning of radar detection. Almost immediately afterwards, the aircraft vanishes and is replaced by a 'ship-sunk' symbol on the map. A cruise from Bergen to square BD can sometimes result in a trail of 'sunk ships' along the U-boat's route!

The problem is intermittent and random, and originally so very rare that it escaped detection during testing, and subsequently was sufficiently unusual that it seemed to be a program bug. However, as NYGM became more complex, the problem became more noticeable. It was when air crashes occurred in late 1943, with bombers based on the airbase in the Azores crashing after radar detection with Metox, that it seemed necessary to investigate further.

It took ages to discover the cause of the problem, involving changing airbases to display single types of aircraft and slowly adding new features back into a stock version of SH3. At first, it seemed to be a cloning problem for different aircraft/radar/RWRs, or a problem with bomber load-outs. However, to cut a long detective story short:

The SH3 program has an intermittent problem with radar warning ranges set to 30,000 metres or more. For NYGM, this affects the Metox and Tunis radar-warning receivers (RWRs), which both have a range of 30,000m. Actually, in real life, both had a range of around 50,000 metres, but the range was cut down in NYGM to 30,000 metres, which is the limit of the real-life horizon.

The extraordinary thing about this program bug is that (with NYGM), it only affects the standard Liberator. The Sunderland and Halifax, both long-range bombers with the same radar equipment in November 1944, are unaffected. (Typical of a possible memory leak in the code, devs please note.)

If the ranges for Metox and Tunis are set to 24,000m, the air crash problem disappears completely. After extensive testing, it is clear that this range is easily sufficient for the U-boat to dive to avoid an aircraft, even at time-compression = 1024.

I intend to release a patch, with other small fixes, for NYGM shortly. Anyone who has used in the past the ancient (2005) Stiebler 'Radar_Detection' fix (a stand-alone mod, also used in the old RUb mod from which other super-mods have been derived subsequently) should use a hex editor (or, better, SH3 Mini-Tweaker or SH3 File Analyzer, or S3DEditor) to change both MaximumRange and PreciseRange for the Metox and Tunis RWRs to 24000 from the existing 30000 (thus four changes in all).

The affected file is silenthunteriii\data\library\sensors.dat.

I have also checked GWX3 RWR ranges. These are set for Metox to 22000 and for Tunis to 25000, so probably users of GWX do not need to make any changes.

Stiebler.