James posted the same photo and question over on the Warbirdz.net forum and below is the amalgam of two posts I made there trying to identify the aircraft in the photo.
It seems clear its a round nose B-18 not a B-18A or B-18B with the later stepped or pointy nose.
Robert Kelly's excellent research on Allied Air Transport Operations South West Pacific Area in WWII covers this aircraft in Volume 1.
It was one of four B-18's that fled 28th Bomb Sqn - Clark Field Philippines to Australia, with only two remaining on strength with the US Air Transport Command by March 1942 that later became the 374th Troup Carrier Group under the 5th Air Force.
These 4 were:
36-338 - Shot down by Japanese fighters off Soerabaya NEI - 3/2/42
36-343 - Robert lists this aircraft as being scrapped at Townsville post June45 with a photo of it on page 320 at Townsville early in 1942.
(this same photo linked in Setters post and captioned as Nedland WA @1941 by the AWM? - note the Anson in the background)
36-434 - Destroyed on ground in NEI 6-22/02/42
37-016 - Robert lists this as a B-18A("pointy" nose), with a photo on page 321 at Townsville showing that feature, but also lists it as having callsign VH-CWB.
Neither of his photos show the aircraft carrying VH- callsigns at the time.
Robert lists both 36-343 and 37-016 serving with the 21st and 22nd Troop Carrier Squadron from February to December 1942 and then being transferred as staff aircraft with Air Service Command, although from his lists there is confusion which squadron each aircraft was actually with, which may also explain confusion over the call sign?
The photo of the B-18 over the Brisbane River is clearly an earlier model B-18 with the "round" nose.
The photo of the B-18 over the Brisbane River is captioned in the above wikimedia site as being in 1943 so its certainly not likely to be 36-338 or 36-434 which were both lost to enemy action in NEI in early 1942, and may never have ever actually made it to, or served in Australia or near the Brisbane River, hence its either 36-343 which apparantly ended its days at Townsville in 1945 or 37-016 (which despite having a "37" number is apparantly a round nose B-18 too - see later information below)
According to the wiki page there are only 5 survivors worldwide, all now located in the USA,
I note consisting of 1x B-18, 2x B-18A, 2x B-18B.
http://en.wikipedia.org/wiki/Douglas_B-18_BoloQuote:
Only five B-18s still exist, preserved or under restoration in museums in the United States:[10]
B-18 Bolo, s/n 37-029, is on display at the Castle Air Museum in Atwater, California. Dropped from USAAF inventory in 1944, it was registered as NC52056 in 1945, later to N52056. The B-18 was used by Avery Aviation and then Hawkins and Powers, as a firebomber, dropping borate for many years.[11]
B-18A Bolo, s/n 37-469, is on display at the National Museum of the United States Air Force, Wright-Patterson AFB, Ohio. One of the first production Bolos, was delivered to Wright Field in 1937 for evaluation testing. Sold as N56847, converted to crop sprayer; by May 1969 stored derelict at Tucson, AZ. Sat outdoors for many years before being restored to static display condition. This aircraft has an incorrect dorsal turret. The museum has been attempting to locate a correct turret for this aircraft for many years.[12]
B-18B Bolo, s/n 37-505, is under restoration at the McChord Air Museum, McChord AFB, Washington. Sold as N67947, then Mexican registration XB-JAJ. Acquired by Tucson Air Museum Foundation of Tucson, AZ and stored at Watsonville, CA. This was the last flyable B-18, making its final flight to Tucson on 10 April 1971. At Pima county Air Museum by Oct 1973, it was subsequently acquired by US Air Force Museum in 1981 and moved to Davis-Monthan for storage, then in 1983 put on display at McChord Air Museum (museum not open to the general public).[13]
B-18B Bolo, s/n 38-593, is on display at the Pima Air & Space Museum Tucson, Arizona. This Bolo spent the early part of World War II on anti-submarine patrol. In 1943 began use a light transport. She was retired and struck from the inventory in 1945. Was operated as a firebomber as N66267 1954–1970. In storage at Litchfield, AZ by September 1969, then delivered to Pima on 5 September 1976. The aircraft sat outside in the desert heat and sun for many years before been restored and moved indoors for display. The aircraft is still equipped with antisubmarine search radar dome.[14]
B-18A Bolo, s/n 39-025, is on display at the Wings Over the Rockies Air and Space Museum in Denver, Colorado. This Bolo spent World War II bouncing around a number of airfields serving as a bombardier trainer and as a light transport. It was dropped from inventory on 3 November 1944, and was later sold, acquiring the civil registry NC62477. It spent 14 years on the civil registry before ending up in Cuba in 1958. In November 1958 the aircraft was seized in Florida by U.S. Treasury agents when it was discovered hauling guns to Fidel Castro. In 1960 the aircraft was parked at Cannon AFB, until being presented to the National Museum of the United States Air Force at Wright Patterson AFB in Dayton, Ohio. It flew to the Museum in April 1961. In 1988 the aircraft was transferred to the Wings Over The Rockies Aviation and Space Museum where it was restored though the 1990s. It is displayed there as 39-522.[15]
There is a 6th well known B-18 "sitting" precariously straddling a deep ravine in the Hawiian Islands that is well known but as yet un-recovered, although there has been recent discussions of its recovery to the Pacific Air Museum.
It is 36-446 a roundnose B-18, ie the second only survivor of that version, and in fact would seem to be the oldest B-18 surviving.

http://www.pacificwrecks.com/aircraft/b-18/36-446.htmlThe B-18 at the Castle Air Museum has the serial number 37-029 but is NOT a B-18A with the pointy nose but is a B-18 with the round nose.

Given its serial is later than 37-016 which is shown in Roberts book on page 321 to definately be a B-18A pointy nose example, it is confusing as to the correctness of the Castle Museum's B-18 serial number, or Robert's identification of his photo as 37-016, or overlapping/intermingled serial numbers of B-18 and B-18A's?
The following information is taken from the NMUSAF website B-18 factsheet who have a pointy nose B-18A on display
http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2457Quote:
The Douglas B-18 was originally designed and built as the DB-1 (Douglas Bomber #1) for the Army Air Corps 1934 requirement for a long range bomber. The DB-1 was based on the Douglas DC-2 and retained many of the latter aircraft's features, including the wing and aft fuselage. The DB-1 was in competition with the Martin Model 146 (an enlarged B-10) and the Boeing Model 299. Although the Boeing entry was clearly superior, the DB-1 was initially favored by the Army General Staff for two reasons. First, the Boeing Model 299 crashed during testing. The crash was the result of pilot error but was technically disqualified from the competition. Second, the DB-1 could be built for about half the cost of the Model 299 (B-17). The General Staff considered the B-17 too expensive and opted for an order for 99 B-18s and only 13 Y1B-17s in 1936.
Thirty-five more B-18s were ordered in 1937, including the last B-18, which had a power nose turret and was designated DB-2 by Douglas. The Army continued to favor the B-18 into the late 1930s when 217 more were ordered as improved B-18As in 1937-1939.
That implies there was a production run of round nose B-18 aircraft in 1937 as well as pointy nose B-18A aircraft in the same year.
Joe Baugher has a website listing all the USAAC/USAF tail numbers, and it suggests 37-016 was a B-18 (and carried callsign VHCWB) and therefore would have had a round nose?
http://www.joebaugher.com/usaf_serials/1930.htmlQuote:
37-1/33 Douglas B-18 c/n 1748,1749,1864/1894
3 (5th BG) destroyed on ground at Hickam Field Dec 7, 1941.
4 (5th BG) destroyed on ground at Hickam Field Dec 7, 1941.
9 crashed on takeoff at Albrook Field, Canal Zone May 11, 1943.
11 (5th BG) destroyed on ground at Hickam Field Dec 7, 1941
12 destroyed on ground at Hickam Field Dec 7, 1941.
16 (19th BG) escaped to Australia, operated as VH-CWB by 21st TCS Jan-Sep 1942
19 (5th BG) destroyed on ground at Hickam Field Dec 7, 1941.
21 (7th BG) crashed at Uniontown, AL Dec 23, 1939, all on board killed.
22 to N67931
29 (c/n 1890) converted to B-18B, registered NC52056 in 1945, later to N52056. After use by Avery Aviation as tanker and then Hawkins and Powers, later put on display at Castle Air Museum, CA
37-458/634 Douglas B-18A c/n 2458/2634
458 (c/n 2458) became N67946, then TG-CIL-54 Dec 1957.
463 converted to B-18B. w/o at Beane Field, St Lucia, British West Indies Oct 22, 1942.
469 (c/n 2469) to N56847, converted to sprayer, by May 1969 stored derelict at Tucson, AZ, then put on display at USAFM, Wright Patterson AFB, OH
472 converted to B-16C. With 7th ASS, w/o in landing accident at Edinburgh, Trinidad, British West Indies Jun 5, 1943.
474 converted to B-18B. With 417th BS, crashlanded at Camaguey, Cuba Jun 6, 1943.
481 crashed near Waller Field, Trinidad, British West Indies Jul 13, 1942.
.
.
through to the last one
.
.
619 (1st Recon Squadron, Westover Field, MA) crashed into Mt Watermomee, NH Jan 4, 1942 after getting lost while returning from U-Boat patrol over the Atlantic. 2 killed, 5 survived.
630 MIA 2/16/1944, Alaska.
It seems clear that the Castle Air Museum aircraft is a round nose B-18 and was built in the same order, but after 37-016 which also seems was built as a B-18 not a B-18A, it would then it would seem it "IS" the aircraft that carried the VHCWB callsign and is therefore the aircraft in the OP photo by James flying over the Brisbane River.
Which then raises the question, which is the pointy nose B-18A identified as 37-16 in the photo on page 321 of Robert Kelly's book. (its clearly not one of the other 3 escapees from Clark that fled to Australia as they are all 36-serials and clearly then also round nose B-18s as well?).
While searching information above I came across this rare colour photo of early B-18s in service over the Phillipines.

Both seem to be round nose B-18's not pointy nose B-18A's?
Regards
Mark Pilkington