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USN AEW radars - October 1945

 
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USN AEW radars - October 1945 - 3/8/2021 11:18:14 PM   
Ian R

 

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Status: offline 		This following emerged from an unrelated discussion thread in the general forum.


quote:

ORIGINAL: Ian R

quote:

ORIGINAL: JohnDillworth

Well how about the declassified ship damage reports?
https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/w/war-damage-reports.html


Very good, and navigating back to the Reading Room unearths a lot of other stuff.

Edit-This is interesting:

https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/a/anti-suicide-action-summary.html

quote:

1. AEW.--This is a powerful airborne radar which will detect aircraft at ranges up to 70 miles and surface vessels at ranges up to 150-175 miles. Radar returns are relayed from the aircraft to a surface display console on a ship having AEW receiving equipment.

This equipment is being installed in two types of aircraft--the TBM, which will carry 2 radar operators, and the B-17, which will accommodate an airborne CIC. One 4-plane TBM unit will be equipped by 1 October 1945, and 5 other units by 1 November. The first 4-plane element of B-17's will be ready about 1 December, and other units, to a total of 16 planes, will follow as completed through January 1946.

Four surface units are being installed in ESSEX class carriers, and units for smaller ships and amphibious application are expected to be ready for shipment in November. Trained personnel will accompany all AEW installations.


I don't think the game has code for AEW per se, so I'll need to do something Dunniganesque with this. Something like a very long ranged radar that can be acquired by taking an Essex off line for an upgrade, perhaps.


So, what we firstly have is, starting October/November 1945, TBM-AEW aircraft operating from Essex class carriers equipped with the surface unit component of the radar. As far as I know, there is no exe code for AEW, and to the extent that there is A2A intercept radar, it is carried by the all weather (night) aircraft and only helps them (If I was wrong about that that would be helpful).

One way to abstractly simulate that would be -

- don't worry about actually depicting the aircraft; - and instead

- have a new radar device (actually two, one SAR, one SSR) that can be acquired by Essex class carriers in an upgrade in October 1945.

- the range of the radars should be the sum of (the ranges quoted in the report + orbit radius of the aircraft), which might be uncovered by some more research.

- there is a problem in terms of vectoring the search. It will work 360 degrees. There may need to be a trade off for that.

Another way to do it would be to actually have a TBM AEW element with very powerful on board radars... but I can see problems - if it is rated as a fighter it might not be in the air, and if it is rated as a search aircraft, it might RTB after detecting an xAKL. Also, airborne radars accuracy/effect is rated well below ground (and ship) radars.

The second thing we have is the B17 flying AEW and "CIC". If the actual aircraft are "factored in" to the device, as JFD would say, that neatly sidesteps the problems of base, range, search station, etc. It seems to me that the B-17 is still relaying detection data to the ships - the reference to a CIC may simply be to something a bit more capable than the 2 operator system on the TBM.

Looking at (US) ground radar device numbers, the mid late war types have accuracy 70, and effect 7. The range can vary considerably though. The SU SSR in slot #1606 (available 4112, but very short ranged) has accuracy 75, effect 8 - so heeding Alfred's advice to look at known values, so as to keep modifications within ranges consistent with the code algorithms, that looks to be about the maximum. There are a couple of later war sub mounted ASRs in with accuracy of 72, but they are also very short ranged.

The values for airborne search radars are much lower than ground radars, e.g. the 1945 ASH radar is Accuracy 40, effect 5. Note that APS-15 (SSR) is accuracy 60, effect 7, but is only carried by PB2Y and PBM.

At this stage the solution seems to be to add the AS radar to the ship, give it accuracy 75, effect 8, and range of, for the air search 124 + aircraft orbit radius. The SS set would be 265+ orbit radius.

Thoughts?

Criticisms?


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RE: USN AEW radars - October 1945 - 3/8/2021 11:32:05 PM   
Ian R

 

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RE: USN AEW radars - October 1945 - 3/8/2021 11:36:48 PM   
Ian R

 

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From: Cammeraygal Country
Status: offline 		In postwar service with the JMSDF



< Message edited by Ian R -- 3/8/2021 11:38:03 PM >

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RE: USN AEW radars - October 1945 - 3/9/2021 6:35:10 AM   
Hrafnagud

 

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Status: offline 		The AN/APS-20A was fitted to the TBM-3W aircraft, for use off of carriers.

The larger-capacity AN/APS-20B was fitted to B-17Gs converted to PB-1Ws by the Navy, and intended for land-based use.

They had the same pulse widths, but the B-model had double the peak power. The B model was able to detect aircraft at around 65 nm and ships at 200nm, so one can assume the smaller-capacity A-model probably had half that detection range (since energy is dependent on peak power and pulse width), i.e. say 30nm for aircraft and 100nm for ships.

The problem is that both models were "look-down" radars and therefore could only detect aircraft flying at a significantly lower level than the aircraft carrying the AEW radar. So it's a bit difficult to model a device that limits the heights at which aircraft are detected.

To answer your question, I would probably create two devices. The first, an upgrade to US carriers from October 1945 onwards called, say "TBM-3W AEW System". Simultaneously, you would need to decrease the carrier's aircraft capacity (by the number of TBM-3W aircraft you are assuming is part of the system) and probably maximum sorties too (to reflect those TBM-3W's using fuel).

The second device would be a land-based device, say "PB-1W AEW System" with a larger detection range than the carrier device. This device would then be transportable by ship or strategic movement. There would need to be a house rule about only deploying that device to a base with an airfield that would be large enough to support a B-17G.


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RE: USN AEW radars - October 1945 - 3/9/2021 10:58:59 AM   
Ian R

 

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From: Cammeraygal Country
Status: offline 		Thanks, food for thought.

I think there is need for both AS and SS devices because the range is different.

Have you seen any technical specs documentation on the AN/APS-20A?

The ranges given by you for the -B are similar to the ranges quoted in the historical document, but it also suggests the -A had that range capability.

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RE: USN AEW radars - October 1945 - 3/9/2021 12:38:51 PM   
Hrafnagud

 

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Status: offline 		You might find this interesting - detection tests run in 1947 by the Evaluators squadron, who flew PB-1Ws:

https://apps.dtic.mil/dtic/tr/fulltext/u2/a060603.pdf

They don't specify which AN/APS-20 is being utilised - but I assume it's a AN/APS-20B (being PB-1W).

The critical thing to remember with radar is detection range is "up to" - there is a very small chance of detection at the furthest possible detection range. The detection chances then improve the closer the range.

The detection tests indicated that there were two main variables involved with detection likelihood in the PB-1W AEW, being relative speed of the intruder aircraft and sea return (heavy waves create radar echoes that obscure target identification).

These tests indicated that under ideal circumstances, with slow-flying intruders, you got up to around 98% likelihood of detecting a single aircraft at 20 miles lateral range. Once range increased to 60 miles lateral, your chances of detection decreased to around 70%, and at 80 miles lateral, it dropped like a stone to around 15% detection chance, until finally almost no detection chance at 100 miles lateral range. If the sea was rough, your chance of detection at ranges below 60 miles were basically zero due to sea return.

The faster the intruding aircraft, the less your chances of detection - under ideal circumstances, an aircraft with relative speed of 400 knots would be detected 90% of the time at 20 miles lateral, whereas an aircraft with 600 knots relative speed would be detected 76% of the time.

The conclusion at the time was that, on direct approach, you had 50% probability of detecting a single fighter at 45 miles lateral range.

< Message edited by Hrafnagud -- 3/9/2021 12:40:08 PM >

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RE: USN AEW radars - October 1945 - 3/9/2021 12:41:48 PM   
Hrafnagud

 

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Status: offline 		Also bear in mind that these detection tests were run in 1947, after they had had some time to iron out teething issues with these AEW sets.

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RE: USN AEW radars - October 1945 - 3/9/2021 2:39:24 PM   
Alfred

 

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Status: offline 		Ian R,

Be very careful, the code is not set up for an airborne CIC.

1. The range you have in mind is not consistent with how the code handles it. Note the comments from michaelm75au and theElf in this thread:

https://www.matrixgames.com/forums/tm.asp?m=2251019

In AE radar does not operate outside of the hex. Radar range translates in chances to detect within the hex. If you give a range of 265+, that is roughly giving 6+ chances to detect. You need to determine whether the real value of these late 1945 radar sets was to increase early warning or improved efficiency at short range, which in the context of the game means 40nm.

2. Night air combat is different from day air combat. In very general terms, view night as a global negative modifier and radar carried by aircraft acting as a global positive modifier whose purpose is to neutralise the negative night modifier.

3. Ship upgrade time will be tricky. Is there any real guidance from prior upgrades as to the appropriate time for this upgrade. It is one thing to fit the hardware but how long before the crew is trained up to speed.


Remember, there is no real electronic warfare in AE.

Alfred

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RE: USN AEW radars - October 1945 - 3/9/2021 11:22:32 PM   
Ian R

 

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From: Cammeraygal Country
Status: offline 		Thanks Alfred, am reading that now. The 265 was k yards, not NM - 244k yards is about 120NM, see below.

quote:

ORIGINAL: TheElf

Radar detects Airplanes. The longer the range the sooner it does so. The higher the effect the more accurate the data and the better your CAP will perform. There really isn't much more to it.


The intention, reading the Cominch summary, was to give earlier warning further out, rather than improve short range efficiency. As it is not possible to directly simulate the former, the AN/APS-20A in game will just be a better shipboard AS radar, with the TMB-3W component not directly depicted.

I'll go with effect 8 and accuracy 75, which is the highest values seen on other devices.

quote:

ORIGINAL: michaelm75au

While radar can have a range in excess of the 40NM hex, it does not extend outside the hex.

Instead, if the radar has a range of more than 40NM, it gets a number of extra chances to detect the raid equal to the number of hexes it could have reached. (range of 120NM would get 3 chances to detect raid, while a 40NM radar only the one).


I wonder if fractions get you a fractional chance, or its like the sets of 10 pilots in TRACOM?

The SC-2 ASR on a standard Essex has a range value 120, which is <60nm. The SK ASR has a value of 182, meaning a range of <90nm. I should give AN/APS-20A a value above that, abstractly representing the patrolling TBM-3W reaching out, to paraphrase MichaelM. At this point I am thinking of a range of 244 (k yards) which = 120.48 [edit - nautical] miles. (243k yards equates to just under 120nm).

That seems to comply with the way this is handled in the code - but no doubt you'll tell me if I'm wrong.



< Message edited by Ian R -- 3/10/2021 6:19:34 AM >

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RE: USN AEW radars - October 1945 - 3/10/2021 12:12:01 AM   
Ian R

 

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From: Cammeraygal Country
Status: offline 		@Hrafnagud - Given what you say about the -B radar and the PB-1Ws, including the actual aircraft is beyond the game code per Alfred. An abstract simulation of the flying AEW/CIC would be to increase the range/accuracy/effect of a shipborne radar so "the better your CAP will perform", but putting big numbers in there might provoke the law of unintended consequences.

I did find this interesting document while searching around for reliable range information:

https://maritime.org/doc/radar/part4.htm#pgSCSK-1:

quote:

Ranges obtained on planes will vary greatly with the altitude of the plane, because of fade areas and the curvature of the earth. Large, high-flying planes have been observed at 120 miles. Average ranges on medium altitude planes are from 60 to 70 miles, and on low-flying planes from 20 to 40 miles on the SC-1, with better results on SC-2 and SK.


The claimed reliable "small plane" range on the SK is 150 k yards, large planes 250 k yards. In game SK (device #1643) is given a range of 182 k yards.

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RE: USN AEW radars - October 1945 - 3/10/2021 5:31:58 AM   
Alfred

 

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Status: offline 		AE code is written on the basis of integers.

Fractions aren't manipulated. Most often they are rounded down to the integer level but depending on the specific algorithm they may be rounded up to the next integer.

Alfred

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RE: USN AEW radars - October 1945 - 3/10/2021 6:18:11 AM   
Ian R

 

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quote:

ORIGINAL: Alfred

AE code is written on the basis of integers.

Fractions aren't manipulated. Most often they are rounded down to the integer level but depending on the specific algorithm they may be rounded up to the next integer.

Alfred


There are plenty of fractions of 40nm in the radar ranges assigned in the 'official' scenario data. However, rather than drawing a possibly incorrect inference from that, I'll just make it a touch over 120nm.

In terms of upgrade times, I already have a "valley Forge" sub-class of the Essex class, which commission with the new 5"/54 DP gun. Those and the Midways arrive starting late 1945, so the AN/APS-20 will be aboard as standard equipment in addition to the SK ASR, with a reduction of 4 to aircraft capacity.

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RE: USN AEW radars - October 1945 - 3/10/2021 10:08:14 AM   
Sardaukar


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quote:

ORIGINAL: Hrafnagud


To answer your question, I would probably create two devices. The first, an upgrade to US carriers from October 1945 onwards called, say "TBM-3W AEW System". Simultaneously, you would need to decrease the carrier's aircraft capacity (by the number of TBM-3W aircraft you are assuming is part of the system) and probably maximum sorties too (to reflect those TBM-3W's using fuel).




Only Offensive actions use Sorties (except Sweep). Fuel is basically unlimited. CAP, Search and other Defensive actions do not use sorties.

Sorties is abstraction of Ordnance used. Sweep, CAP etc. do not use up Sorties since bombs and torpedoes are not used.

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RE: USN AEW radars - October 1945 - 3/10/2021 2:11:18 PM   
Hrafnagud

 

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Status: offline 		Thanks for clarifying. It seems the max sorties field in the database for carriers correlate closely to a fraction of the actual bulk avgas storage those carriers had in real life, hence my assumption.

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RE: USN AEW radars - October 1945 - 3/10/2021 2:18:07 PM   
RangerJoe


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Status: offline 		Except that there is no AvGas in the game, nor MoGas either. Those are all lumped into supplies, hence sorties reloaded from a port, AE, and/or an AKE.

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RE: USN AEW radars - October 1945 - 3/10/2021 2:42:49 PM   
Hrafnagud

 

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Status: offline 		Sure - was just indicating that from a modding point of view maximum sorties appears to be derived from maximum Avgas storage, in case someone wants to mod a new carrier.

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RE: USN AEW radars - October 1945 - 3/10/2021 3:02:38 PM   
Sardaukar


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Status: offline 		Sorties are maybe calculated as some mix of available AvGas and Ordnance...or just ordnance. Torpedoes are calculated separately.

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