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CAC Wirraway Target Towing Conversions

More than 50 CAC Wirraways were converted for target towing duties. This page describes the background to the development of target towing Wirraways, the modifications carried out and how these aircraft were used.

Aircraft converted

Conversion details

Acknowledgements

On August 4th 1941 a request was made by R.A.A.F. Southern Area Headquarters to Number 1 Aircraft Depot at Laverton to make an experimental installation of a Type "D" winch in a Wirraway aircraft. A series of drawings were provided showing the details of the installation, and it was mentioned that this installation should be similar to that of the American "Grumman" target towing gear which had been recently fitted to Wirraway A20-183 at No. 1 A.D.

By August 30th 1941 the installation of the equipment into Wirraway Mk II (CA-8) A20-283 was well under way, with all the brackets, clips and stay tubes having been fabricated according to the supplied drawings. A Type "D" winch was borrowed from No. 1 Bombing and Gunnery School and overhauled prior to installation. Flight tests were carried out at Laverton and by September 24th it was reported that the operational figures and airspeeds were similar to those found in trials of the "Grumman" style winch in A20-183. Two American A5 sleeve type targets and one Astern Attack target were streamed successfully and the operation of the winch and target exchanging was found to be satisfactory.

During December 1941 A20-283 was tested at No. 1 Armament Training Station at Cressy, and a number of suggestions were provided to Southern Area Headquarters regarding additional equipment which should be supplied with target towing aircraft equipped with the Type "D" winch, including:

• a "combination spanner" for removing locking nuts on the drum spindle and assembly shaft;
• an electric-powered bench winder for re-winding cables onto drums;
• a field winder for similar purposes; and
• spare drums (6) and shafts (2) for each aircraft.

Modifications to the test aircraft A20-283 were also suggested, including:

• cutting away the bomb-aiming doors to clear the pulley;
• adding a sliding shutter to the port side of the fuselage (just forward of the fire extinguisher access) to allow the drum spindle to be easily removed;
• finding a method to secure the free ends of each cable to its respective drum;
• adding a protective cover or shield over the drums to protect the operator from any loose cable ends as the drums unwound;
• installing a voice tube for communication between the pilot and the winch operator;
• adding a harness anchorage point for the winch operator;
• fitting a small canvas satchel to store tools and attachments used with the towing gear;
• supplying a small pair of bolt cutters to remove any tangled cables in an emergency; and
• supplying an Aldis signalling lamp along with a stowage bracket

A series of detailed sketches of some of these modifications were provided.

In January 1942 A20-283 returned to No. 1 Aircraft Depot for a short trial of a modified target towing "fish", the fitting on the end of the cable which allowed for the exchange of targets during flight.

Wirraway Technical Instruction number 24 "Preliminary practice target towing" was issued prior to November 1942. (more details to follow)

On September 1st 1944 a conference was held to discuss future RAAF training needs. One of the many recommendations to come out of this conference was that the ageing Battle target towing aircraft should be replaced by Wirraways and Vengeances suitably converted for this activity. It was estimated that a total of 72 Wirraways equipped for target towing would be required for use by Air Gunnery School (66), Air Armament & Gas School (3) and Central Gunnery School (3).

This recommendation was forwarded to the Air Board, and was minuted in paragraph 5 of Air Board Agendum 6079:

That action be taken to replace Battle target towing aircraft with Vengeance fitted with type "B" Winch at O.T.U.s and Wirraways fitted with type "D" Winch at A.G.S., C.G.S. and A.A.&G.S. When replacement of all target towing Battle aircraft has been made the Battle may then be declared an obsolete type, there being no further training commitments for this type of aircraft.

This recommendation was approved by the Air Board on September 22nd 1944.

Rather than replacing the target towing Battles only with Vengeances, it was determined that converted Wirraways should be adopted at three specific units for the following reasons:

• Difficulty in Battle maintenance
• Vengeance are too fast to co-operate with Ansons and Wirraways at A.G.S., C.G.S. and A.A.&G.S.
• The reduced maintenance effort required by employing Wirraways instead of Vengeance

It was initially estimated in September 1944 that there would be a need for approximately 70 Wirraway conversions, but by January 45 the requirements had been re-calculated as follows:

To implement the Air Board decision, RAAF Organisational Memorandum No. 608 was issued as follows:

Target Towing Wirraways (231/9/798)

It has been decided that the Wirraway Aircraft, suitably modified, will satisfactorily replace the Target Towing Battle Aircraft in Air to Air Gunnery practices.

As a result, action will be taken to modify a number of Wirraways, sufficient to meet all requirements for establishments, reserves and wastage in Air Gunnery School, Air Armament and Gas School and Central Gunnery School. The number of aircraft required will be based on a rate of effort of 40 flying hours per aircraft per calendar month.

When the Target Towing Battles have been replaced, there will no longer be any use for Battle aircraft of any type and steps will be taken to declare them surplus to R.A.A.F. requirements.

For information.

(Signed) J.R. Bell
Group Captain, D. of C.

By May 1945 it was realised that training requirements would not be as great as was expected in 1944, hence the number of Wirraways planned to be converted was reduced from 70 to 45 as follows:

Based on this requirement the block of aircraft from A20-660 to A20-704 inclusive was reserved for conversion. These aircraft were all held at Number 7 Aircraft Depot at the time.

Details of the operation of the Type "D" winch were issued as Wirraway Technical Instruction number 44 "Target towing operation of Type "D" triple drum gear using automatic target exchange attachment". This Instruction was issued around December 1942 and was divided into 8 parts, covering the following areas:

1. Introduction
2. Assembly of drums to winch in aircraft
3. Launching the first target
4. Exchange of targets
5. Release of towing cable
6. Breakage of cable or failure of target exchange "fish" to operate
7. General
8. Tools and spare attachments

The Type "D" winch was not powered, and was simply a set of 3 removable drums mounted on a shaft together with a brake to control the unwinding of each cable one at a time. In operation, one cable was unwound and trailed behind the aircraft. Then the first target was launched onto the cable, out of the bomb-aiming doors under the fuselage just aft of the wing. Once the first target was damaged by gun-fire, the second target was launched onto the cable. A fish-shaped fitting on the end of the cable allowed the first target to drop from the end of the cable when the second one reached the end, allowing several targets to be streamed from the same cable one after another without having to retreive the cable to exchange targets. If a cable became damaged or a target refused to un-clip, then the cable was dropped (over the airfield for retrieval) and the next cable was unwound from its drum.

The Type "D" winch showing the support frame and 3 drums mounted on a common shaft.

Aircraft converted

Wirraway aircraft which were converted to target towing configuration are listed in the table below:

(missing conversion dates are still to be added)

Conversion Details

Details of modifications required for target towing were issued as Wirraway Technical Order number 101 "Towing gear - Fitting of "D" Type winch" (which superseded Wirraway Instruction number 24) issued on December 16, 1944. This Order was divided into 5 parts covering the installation of all the equipment needed:

1. Jockey pulley and bracket
2. Installation of "D" type winch
3. Empennage guarding system
4. Operator's seat
5. Installation of Aldis lamp, tool bag and sliding trap door

The conversion to target towing configuration using the Type "D" winch involved a series of minor changes to the airframe, none of them structural:

• The rear seat, flexible gun rail, gun hoist and fittings were removed;
• The Type "D" winch was installed on two tubes mounted across the top rails of the steel tube framework, with additional bracing stays attached to several points on the aircraft framework;
• A jockey pulley was installed on a short post below the rear seat pivot. This pulley extended out into the airstream below the aircraft through the bomb-aiming doors under the position of the rear seat. Bracing tubes were added to support the pulley;
• A new folding seat (facing forwards) was installed for the winch operator, further aft of the position of the original rear seat;
• A shelf for stowing the folded targets was installed behind this new seat;
• A canvas satchel was installed on the starboard side of the rear cockpit for stowing tools and fittings;
• An Aldis signaling lamp was installed along with a bracket for storing the lamp when not in use;
• Four protective wires were installed between the horizontal stabiliser, the fin and the aft fuselage to prevent the towing cable from fouling the elevator or rudder control horns;
• A guard was fitted to the port side of the tailwheel to prevent the towing cable from wrapping around the tailwheel axle

More details and drawings coming soon...

Acknowledgements

Many thanks to Steve MacKenzie and Tim Bishop for their assistance with information used in this article.