S-39 AAR

[TorpX]

[The following is a patrol summary (edited to be brief) of S-39 (SS-144) on it's 2nd war patrol. I had originally intended to post the 1st war patrol report, but in fact, there were no contacts made, so it would make for very dry reading.]

S-39 (SS-144)

2nd War Patrol, Feb. 8, 1942 ___________Wind 5, clear
We quickly make last minute checks and shove off from base at Surabaya at 0600. It is still dark, and we are to be on are way before dawn. I order watch to be vigilant; enemy subs could be lurking anywhere.

Our operational orders are to proceed to the Molucca Passage and patrol within 100 nm of map reference. Additional orders will be sent later.

We have 12* Mk. 10 torpedoes, 125 * 4 inch HE shells, a full load of fuel, and provisions for 60 days. Hopefully, we can find targets and be back earlier than that. After the disappointing 1st patrol, the crew is eager for action, and are keen to prove themselves.




http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/Leaving%20Base_zpsetzyokqq.png
0627 exit harbor. XO plots course to our objective: 1,450 nm. We discuss the fuel situation in light of our orders. Unspoken, but not forgotten, is our lack of any contacts on the first patrol.

Our options boil down to 2 basic alternatives. We can transit to our PZ at 2/3, so we reach the objective in about 7 days, and have enough fuel to patrol about 15 days, provided we are careful, then go back at the same speed. Our second option is to transit at 1/3, reaching our goal in about 10½ days, and having fuel to operate for 25 or 30 days. Travelling at 2/3 doubles our fuel consumption, and only saves us 3 days. I decide on the second option.

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/Route%20to%20PZ_zpsleq4rmrf.png
Note that I do make some minor deviations from a direct route, in the hopes of finding some enemy ships on the way. Given that IJN is advancing everywhere, there is no telling where they might be found.


Feb. 9 ______W0, clear _______ 134 mi. steamed

Feb. 10 _____W0, clear _______ 143 mi. steamed

Feb. 11 _____W0, clear _______ 139 mi.
pass within 40 nm. of Makassar.

Feb. 12 _____W0,14,15, clear ___144 mi.

Feb. 13 _____W15, clear _______110 mi.
We pass ~100 nm SSE of Kendari.

Feb. 14 ______W3, clear _______ 140 mi.

Feb. 15 ______W0, pt. cloudy ____137 mi.
Pass N of island Burn.

Feb. 16 ______W5, 3, 2 pt. cloudy ______136 mi.
Passing W of Obi.

Feb. 17 ______W2, 0, pt. cloudy _________137 mi., fuel 87%
Enter patrol area. Cross Equater today.
Sight six aircraft today. We are patrolling submerged at about 3 kn.
2300 Pass 20 nm W of Ternate.

Feb. 18 ______W15, 4, overcast, rain ______124 mi.

Feb. 19 _______W0, 6, clear _____________ 71 mi.

Feb. 20 _______W0, 9, clear _____________ 72 mi.
1840 20 nm. E of Kema.

Feb. 21 ________W15, 12, overcast, hv. rain _____93 mi.

Feb. 22 ________W15, 1, clear ________________ 53 mi.

Feb. 23 ________W1, 7, 15, overcast, to cloudy __90 mi., fuel 81%
One week on patrol.

Feb. 24 ________W15++, pt. cloudy ________ 31 mi.
Minor shorts in electrical equipment.

Feb. 25 ________W15++, 3+, 8+, clear _____45 mi.
Stormy weather, waves severe.

Feb. 26 ________W15++, 1, 0, cloudy ______ 42 mi.
Weather calms.

Feb. 27 ________W0, 6, 0, clear ___________ 58 mi.
Crew reports corrosion on deck gun.

Feb. 28 ________W0, pt. cloudy ____________ 43 mi.

Mar. 1 _________W4, 7, pt. cloudy, rain ______39 mi.

Mar. 2 _________W7, 3, 0, 7, 12, clear to overcast ____36 mi.
Radio message: Base moved to Fremantle.
2nd week of patrol done, fuel 76%

Mar. 3 _________W12, 15 _______________ 91 mi.
We contact base: No new orders; we are given liberty to play our hunches.
Radio on the fritz later.

We have a routine where we patrol submerged with a periscope watch, at min. speed, (usually ~3 kn.), as we take a E-W course across the Molucca Passage. At night we surface and charge batteries, and move a short distance, unless we decide to try a different part of our area. In this way, we are using less than 1% of our fuel each day.

Mar. 4 _________W15, 12, __________ ~113 mi.
1732 sound reports light screws! GQ! We work up to ahead full and come to 348 T, NAC. Cannot ID ship, but it is a lone merchant. It becomes apparent our position is not favorable and the battery is already down to 66%, so we will have to surface and attempt to get ahead of it.
1820 surface. Ahead flank. We can make ~11 kn. As there is an island ahead, the ship changes course and ends up behind us. We dive and allow it to pass close by at 500 yds. We see it is a Dutch composite superstructure freighter. We are naturally very disappointed.
1905 Secure from GQ. Resume course 042T. Battery 56%, fuel 73%.

[TorpX]

Mar. 5 _____ W12, 15, 10, pt cloudy ______ 75 mi.

Mar. 6 _____W10, 14, pt cloudy__________ 41 mi.

Mar. 7 _____W14, 15, 9, clear, hazy _______38 mi.

Mar. 8 _____W9, 12, hazy, overcast _______41 mi.
2349 we are about 8 nm off coast of Mindanao.

Mar. 9 _____W12, 15 __________________71 mi.
0313 plot course to mouth of Davao Gulf. We have been on patrol for 3 weeks now. Fuel 69%. 0800 sonar
malfunctions.. fixed by 1400. Bad time for this.

Mar. 10 _____W15 __________________ 33 mi.
From our present position, it is 2,900 nm to Fremantle, by way of Balikpapan. 1548 large a/c spotted. It is too
close, we dive to 160 ft. 1645 another a/c, unk type.
2320 plot course SW through Celebes Sea, speed 1/3, ~4 kn.
We can maybe patrol that area for a week, before supply issues force us to return. This is our 31st day at sea.

Mar. 11 ______W15, 5, 12 ______________86 mi.
We submerge and continue at 46 ft.

Mar. 12 ______W12, 5, 3 _____________95 mi.
We decide to transit on surface from here; speed from 4½ to 6 kn.

Mar. 13 ______W3, 0, 14, ____________ 116 mi.
1900 overcast, hv. rain. speed drops.

Mar. 14 ______W14, 8, 3, rain to pt. cloudy ____119 mi.

Mar. 15 ______W3, 7, _______________95 mi.
0000 enter Makassar St. patrol area. All stop. Fuel 62%.
We patrol submerged in day going across the strait.
0620 crew reports engines made funny sound before dive, but seem ok? We don't need any engine problems!

Mar. 16 ______W7, 0 _______________ 38 mi.

Mar. 17 ______W3, 0, 8 _____________49 mi.
0722 ship sighted! bearing 212°, long range. We are on course 137T. Ring up standard speed, course 260T.
0733 Sound GQ.
We are in a bad position, and must make a series of high speed sprints, then slow to take observations. We are losing bearing, so we must accept a longer shot than I would like. After 5 observations, we set gyros, and make ready all tubes.

Tracking Data Sheet:
time ___sub c/sp ___ Ms, Mt ___Tgt id ___ Range ___Aob ___ Bearing ____ Speed/ Course
0739 ___254T _____#1, #2 _____MR ____9850 yd.__70P ____084° ______
0744 __3 to 8 kn. ___ #3, #4 ____ _______8250 yd. __75 P ___082° ______9.5? course 222?
0750 __ _________#5, #6 __ Med. Eu.___ 6750 ____75 P ____078° _______C 212
0757 ____________#7, #8 __ composite __4950 ____70P ____073° ______S 11? C 210?
0803 ___________#9, #10____________3600 ____80P ____065° ______10 kn.

Set gyros at +40°, Track angle 133 P. (This gives a TTa of 93° P.)
Longitudinal spread.
Torpedo run estimated to be 2,900 yds. for a time of 2:27.
Launch on bearing 53.75°.

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/Tracking%20Party%20plot_zpsvlbi1wv1.png
[The first points in line correspond to the last observation in the data sheet. After this point calculations are made and gyros are set.
The second points are the positions at torpedo launch.
The last points are the positions at impact.]

I planed to use all four torpedoes, but the last one is delayed and I check fire, as the target has moved too far along. 2:33 after launch, at 0809 hrs., the first one hits after the stack, the second hits near the stern. The third misses aft.
0816 target is burning, and seems to have lost propulsion.
0830 target appears to be slowly settling.
0834 target sinks.


Medium European composite freighter, 5,186 tons [0-56N, 119-20E]

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/First%20target%20hit_zpslu0ifn2m.png

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/Target%20sinks_zpssrbwiwjr.png
0840 resume course 135T, secure from GQ.

I am very pleased with the tracking party; we were in a difficult position, but were able to calculate and execute an effective attack.
We were using full speed, which gave about 8.5 kn. This was necessary, but also required about a minute to slow to 4 kn. for a periscope observation. The average speed at this run was 7 knots. This, and the long range, precluded a larger number of observations.

The Academy could put this one in their book.

[TorpX]

[I, perhaps, should have mentioned beforehand that this patrol is in a high-realism career, the only option I allow myself is the external view, and I am careful not to use it to gain an advantage.

Also, I follow orders, at least to the extent they make sense.
I am using my mechanical breakdown rules.
I am using strictly full manual targeting for the S-class (i.e. no TDC).
I am keeping to a max. of 32x (64x submerged) time compression.

.........in case you were wondering why I seemed to be so excited when I finally sunk a lone freighter. :woot:]



After the attack, I did some supplementary calculations. If I had wanted to do a 'straight shot', we might have gotten to about 2550 yds., but the track angle would have been 130 or 135, so I don't see that it would have been an improvement.
Mar. 18________W8+, 7+, 15++ overcast, rain _________40 mi.
Fuel 59%

Mar. 19_____W15++, 0 ________________________ 53 mi.
1752 sound contact! Merchant 301°, long range. GQ, come to 320T.
1826 after sprinting off and on for 25 min., we find ourselves too close, and in danger of being run over.
I dive to 120 ft. It is too dark to use stadimeter. This is making things very tough.
1839 secure from GQ.
1850 surface. CO2 31%, Batt. 66%. W6+, clear vis. not good. We pursue. It is rapidly becoming very dark.
1910 GQ - gun action!
It is very hard to see the target, and it is doubtful if we can get into position for a torpedo attack, without slowing them down.
We manage to get hits on target - maybe 3/4 of our shots hit somewhere, but placing hits along the waterline would be sheer luck.

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/Gun%20action_zps54ivrkpm.png [If you can barely see anything, that's what it looked like for us.]


We periodically see fires on the target, but these go out after a while. We are in danger of losing sight of them. We seem to be gaining a bit, but dare not get close, as they are likely to be armed. After a while we are down to 50 shells, then 25. I had hoped to retain 25 or 30 for a reserve, but what can one do with only 25 shells, anyway? We've put in too much effort to stop now. I give the order to keep firing...

Finally, the crew fires off the last round. Just moments later, my sharp-eyed XO says 'she's goin' down'. All I can see is two small fires, but it turns out he's right.
We log it: Large old split freighter 8,203 tons [0-52N, 119-29E].
2022 crew stands down, resume course 249T. We pursued about 25 mi. at speeds up to flank.

Mar. 20_________W6+, 11+, 4+__________59 mi., fuel 57%

Mar. 21_________W15++, stormy________ 36 mi.

Mar. 22________W15++, 8+, 3+ pt. cloudy ________47 mi. 0829 sound contact! GC, come to 290T (from 111T). Target zigs and again, we find ourselves in a bad position. Also, though we get close, we cannot see it well enough to ID it.
I decide to attack regardless. I attempt an improvised shot with a 16° lead angle, 100 to 110 starboard track angle.
We launch 4 torpedoes, but all miss. Most likely target was slower than thought. I can see target zig in the distance.
0920 surface. W8+, pt. cloudy 'good' vis., we can make 11 kn. at full.
1000 we get ahead of it, but seems we've been spotted?
We dive. Target looks to be zigging again, so I try another improvised shot.
We must turn almost 180, they zig, and it is now very close!
I order full reverse, and launch 3 torpedoes 10° ahead. The track is nearly a 90 ° track, so we should get hits.
1023 fire 3, longitudinal spread, 28 sec. later, explosions; all 3 hit.
It sinks quickly.

1029 we log it: Medium old split freighter 5,457 tons [0-36N, 119-17E]
http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/3rd%20Target_zpszeap8fgv.png

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/3rd%20Target2_zpsf0ybfqb9.png

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/3rd%20Target3_zpsiy8ta4ox.png

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/3rd%20Target4_zps0bich75d.png
1036 secure from GQ. Resume course 091T, at 3½ kn. I estimate we travelled about 16 mi. off course.
1534 sound contact! 101 °, long range.
1540 GQ, full speed, come to 300T.
1547 reduce speed to 3 kn. We are close now.
1556 we see the ship is Dutch. What are they doing out here alone? Secure from GQ. Resume course 095T.
1835 surface. CO2 17%, Batt. 70%.

Mar. 23________W3+, 1+, 15 _________ 62 mi.
Near tip of Borneo.

Mar. 24_______W15, 0, ______________ 88 mi.
1600 PO Root reports radio out of commision.

Mar. 25______W 0, 5, 15, 8, overcast _____99 mi.
We are exiting out PZ to the South. We still hope to find a use for our last 2 torps.
33 days on patrol, 45 days at sea.

Mar. 26______W8, 5, 15, ___________97 mi.

Mar. 27 ______W15, 9, 8, 7, _________133 mi.

Mar. 28______W7, 15 ____________117 mi.
1345 Plot course to Lombok Strait, 359 nm.
I plan on cutting in toward Java, in the hopes of finding another Jap ship, but later think better of it. The seas are rough and it will take too long. This change shortens our course about 120 nm.

Mar. 29 _____W15, 14, overcast, hv. rain_______118 mi.

Mar. 30 ______W14 ____________________
0420 enter Lombok St. ahead standard.
1054 exit strait. Plot course to Fremantle, 1,591 nm., ahead 1/3.

Mar. 31______W14 _________256 mi. (today and yesterday), fuel 42%
We should be able to use 2/3 speed or better from here.

Apr. 1______W9____________148 mi., fuel 38%
Reduce speed to 1/3.

Apr. 2_______W15, 15++_______179 mi.
It is unlikely we will reach base on schedule. I tell the cook that he may have to stretch our food supply.

Apr. 3______W15++, 15_______134 mi.
Dive part of day. Weather is awful.

Apr. 4______W15_________99 mi.

Apr. 5______W15, 15++_____184 mi.
We are only making about 4 to 4.5 kn. at 2/3 now.

Apr. 6______W15++______116 mi.

Apr. 7______W15++, 15_____105 mi.
Storm abates somewhat. Fuel 20%.

Apr. 8______W15, 15++____178 mi.
Use standard speed.

Apr. 9______15++________144 mi.
2328 batter suffers damage. No point in fixing it now.

Apr. 10_____W15++______114 mi.
Food running low, I order crew to break out emergency rations.
61st day at sea!

Apr. 11_____Winds reduced near shore._____100 mi.
0001 Finally reach port. 61 days at sea.
2 torpedoes remaining. No 4in. shells.
4% fuel remaining.
3 merchants sunk.

Note, that from the time we passed through Lombok St. until reaching port, the weather has been very rough. Many hours at W14 or higher. I am glad I didn't try to hang around Java for a few days. No doubt the crew is equally thankful, being in the habit of eating meals every day and all.

It was, I think, a long patrol for our humble sugar boat.

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/patrol%20route_zpsyiibz4il.png [The zones marked in pink were patrolled extensively. The route marked is only approximate.]
Our score:

http://i1130.photobucket.com/albums/m526/TorpX/S-39_2/Score_zpsetywv8ve.png

We thought we would be warmly welcomed, but perhaps the higher-ups are miffed about our first patrol.
We received no decorations or commendations whatsoever!

I guess there is no glory in the Pineapple Navy.

[Hitman]

Niiiiice :up:

I am using strictly full manual targeting for the S-class (i.e. no TDC).

But you mentioned the use of Gyro Angle in the report instead of straight shot. How are you calculating the torpedo GA and also the convergence correction? External tool or the TDC as calculator?

And, how are you setting the torpedo GA overriding the TDC? Maybe setting speed to zero in the TDC and aiming with the periscope?

Must be a hell more complicated than in real life was :ping:

[TorpX]

I am using the method outlined in THIS (http://www.subsim.com/radioroom/showthread.php?t=200846&highlight=AFS+I%2C+firing+solution&page=2) thread, starting at post #45.

There is an associated program to crunch the numbers HERE (http://www.subsim.com/radioroom/downloads.php?do=file&id=4236).

I had tested the method in easy bathtub type missions, but, of course, there is a greater challenge in action, where there are unknowns to contend with.

I should mention another thing about the "Tracking Party" program. There is a 'high-realism' mode where you enter a value for the expertise of your crew, and the results you obtain are subject to error. Using this, along with the inevitable errors that are due to foregoing map-contacts, makes for a challenging game, I think.

The way I set the Gyro Angle is to dial in the highest possible range in the TDC, zero speed, as you guessed, and turn the scope to that bearing. There is a calculator in the program to address this, but I think in RFB, if you use a range of 11,000 yds., you don't really need it. The program does the math, and will make the sketch, if you want.

The basic idea is to simulate the limitations that existed in relying on the Mk. VIII angle solver, instead of the TDC. Firing solutions had to be calculated in advance, and couldn't be changed, or updated in real-time.