Wirraway batch numbers – Mark I aircraft

For reference purposes I’ve collated a list of production batch numbers for the CAC Wirraway aircraft delivered to the RAAF between July 1939 and July 1946. This page contains the batch numbers for Mark I Wirraways, which were delivered under the CA-1 production “contract” number. This contract number was an internal number used by CAC (similar to the accounting “charge number” system used by North American Aviation) and was not the actual contract number from the Defence Contracts Board.

Wirraway typeCAC Contract NumberRAAF Contract DemandOrdering entityOrder NumberQuantity deliveredCAC Constructor’s NumbersRAAF Serials
Mk ICA-1T.374DCB(unknown)401 to 40A20-3 to A20-42

DCB = Defence Contracts Board

Batch numbers
During construction, each aircraft was given a batch number, for the ordering of parts and materials. Batch numbers consisted of a letter for each batch followed by a number for each aircraft in that batch (e.g. A1, A2, A3, A4, etc). Wirraway production was generally planned in batches of 10 aircraft. But there were exceptions, as it appears the first 10 aircraft were produced in two batches of five (more on that below).

The letters I, O, Q and V were generally not used as batch numbers, as they could be confused for numbers. Usually a new contract (such as CA-1, CA-2, etc) started with batch “A”.

The definitive source for batch numbers is a ledger book kept by Mr Gordon Parker, Supervisor in the Sales Department, and one of CAC’s earliest employees from 1936. This book is now held in the collection of the Australian National Aviation Museum at Moorabbin Airport.

During production, batch numbers were temporarily attached to the firewall and then the rudder (once the engine was mounted). These temporary numbers are sometimes visible in factory photos.

Constructor’s numbers
These were a sequence of numbers allocated to each aircraft in the sequence that they came off the line. For example, Wirraways delivered under the CA-1 contract were given constructor’s numbers from 1 to 40.

RAAF stores number
All equipment in the RAAF was allocated a stores number for tracking and accounting purposes. Aircraft were tracked under the category “A” and each aircraft was given a specific number, Wirraway aircraft being allocated the category A20. These numbers are often referred to as the “serial number” of the aircraft in RAAF service.

Linking batch numbers, stores numbers and constructor’s numbers
Here are several photos showing Mark I Wirraways under construction, allowing us to link the batch codes to RAAF stores/serial numbers.

The photo below (Figure 1) shows a group of fuselages under construction at the CAC factory. This is very early in the production (note the two Gannet aircraft near the hangar doors), and the batch number C2 can be seen attached to the firewall. Unfortunately no serial codes are evident, and so we can’t definitively connect this batch number to a serial number. But by tracing back from other aircraft in batch C (explained below), C2 would have been A20-9.

Figure 1: Early Wirraway Mark I production at CAC. Batch code C2 is visible on the firewall of this fuselage (Aircraft, August 1, 1939, p. 17)

Another photograph of early Wirraway production (Figure 2, below) shows A20-21 on the production line, with the batch number D9 on plaques attached to the firewall and also the rudder. The camouflaged Wirraway behind A20-21 has the batch number E1 on its firewall, corresponding to A20-23 which was the first aircraft delivered to the RAAF in camouflage.

Figure 2: Wirraway A20-21 on the production line, with batch code D9 visible on the firewall (RAAF Museum).

Taken immediately beside the photo above, Figure 3 below shows A20-20 on the production line, with its engine installed. The batch number on the rudder is not readable, due to the angle of the rudder. Immediately behind sits another silver-doped Wirraway with batch code D10 on the firewall (corresponding to A20-22, although the serial number is not visible in the photo), the last silver-doped Wirraway.

Figure 3: Wirraway A20-20 in final assembly at CAC (RAAF Museum)

Unfortunately Gordon Parker only started recording the batch numbers from H8 onwards (A20-60, well into the CA-3 contract). So we need to “reconstruct” the earlier batch numbers based on other evidence including:

  • Photograph above (Figure 1) shows D9 was A20-21 (c/n 19)
  • The  Clyde Engineering tag on A20-10 at the Australian National Aviation Museum reads “SERIAL 01/3124/C3”, linking batch number C3 to A20-10 (c/n 8)
  • A frame in a private collection which is identifiable as a CA-1 forward frame has  the original CAC identification tag which reads “Serial 01-3124-C2“, meaning that C2 was a CA-1 contract aircraft, most likely A20-9 (c/n 7) – see Figure 1 above

Counting back from D9 (A20-21, c/n 19) we can postulate that D1 was A20-13 (c/n 11). If we then assume that batch C was 5 aircraft, then C5 would be A20-12 (c/n 10) and C1 would be A20-8 (c/n 6). This fits with A20-10 (c/n 8) being C3. 

This then leaves the first five aircraft and two batch numbers, A and B. It is possible that the first five aircraft (which were assembled from imported components manufactured by NAA in California) were batch B and perhaps the two imported airframes (A20-1 and A20-2) were considered as batch A. But this is just speculation. Until further evidence can be found, I will describe the batch numbers of the first five aircraft as “unknown”.

Thus we can arrive at the table below showing the batch numbers for all Mark I Wirraway aircraft delivered under the CA-1 contract.

Caveat lector: These batch numbers were current at the time the aircraft left the factory. During RAAF service, various parts could be changed during repairs, resulting in possible differences between batch numbers and serial numbers as listed below. So one should not expect that this list will perfectly match with frames in existence today, and if trying to identify a particular frame from its batch number tag, additional evidence should be sought.

CAC Contract Number CA-CAC Constructor’s NumberRAAF SerialBatch Number
11A20-3Unknown
12A20-4Unknown
13A20-5Unknown
14A20-6Unknown
15A20-7Unknown
16A20-8C1
17A20-9C2
18A20-10C3
19A20-11C4
110A20-12C5
111A20-13D1
112A20-14D2
113A20-15D3
114A20-16D4
115A20-17D5
116A20-18D6
117A20-19D7
118A20-20D8
119A20-21D9
120A20-22D10
121A20-23E1
122A20-24E2
123A20-25E3
124A20-26E4
125A20-27E5
126A20-28E6
127A20-29E7
128A20-30E8
129A20-31E9
130A20-32E10
131A20-33F1
132A20-34F2
133A20-35F3
134A20-36F4
135A20-37F5
136A20-38F6
137A20-39F7
138A20-40F8
139A20-41F9
140A20-42F10

I welcome feedback on the table above, with supporting evidence of any possible inaccuracies.

References:

Commonwealth Aircraft Corporation. Sales Department Aircraft Delivery Ledger; Kept by Gordon Parker. CAC Collection, Australian National Aviation Museum.

Commonwealth Aircraft Corporation. Aircraft Drawing Office Manual. Incorporating up to Amendment List No. 2, Melbourne, Australia, 1946.