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If equipment configuration records existed for each Avenger variant that's exactly how they  would they would be listed. Since these lists are not available, the Avenger's electronics have been arranged into three broad categories. These are: tactical, communications and  navigation. "Textbooks" were prepared by the School of Naval Aircraft Maintenance (SNAM) but the MICN from which some of the low res photos are derived  is silent on the electronics details. American manuals were used as a baseline and any differences in the Canadian Avengers were explained in training/reference manuals produced by SNAM.

The list below shows all the equipment that was ever fitted on all variants of the Avenger even it was only experimental. Many of these equipment designators were recorded from display boards which accompanied newly converted Avengers in photos which appear in the previous document . These photos are captioned “mock-up of AS 3M (above) and first prototype AS 3 Mk 2 (below).”  Every effort has been made to ensure the highest accuracy. If there are errors or omissions, please contact :jerry.proc@sympatico.ca

William Nye published data sheets for the Avenger TBM-3 in the August and September 1962 issues of the magazine Model Airplane News.  .”  It is believed that most of the equipments listed in his sheets and reproduced immediately below were carried in the RCN AS 3 Mk 1s. There were two minor errors in the original  list which have been corrected.

Radio communication equipment
AN/ART-13 transmitter
ARB receiver and ARC-5 series equipment
AN/ARC-1 VHF transceiver

Radio navigation equipment
AN/ARR-2 VHF homing receiver
AN/APN-1 radio altimeter

Tactical Equipment
Search radar       AN/APS-4
IFF                     AN/APX-2 IFF

RADIO COMPASS (ADF)

 In 1954, the Lear Radio ADF-14,  and the Canadian Marconi CMA-301 were being evaluated for use in the Avenger based on the current information at hand. It would appear that the Lear device was adopted as the Avenger's radio compass but in its military version, the AN/ARD-7 [2] . There is at least one photo showing the ADF-14 installed in an Avenger cockpit but no photos of the Marconi CM-301A.

 The receiver in the ARD-7 system appears physically identical to that of the ADF-14.  A comparison photo of the ADF-14,  ARD-7 and CM301A can be found here. There is one difference between an ADF-14 and a ARD-7. The ARF-7 should have name a nameplate affixed to the front panel.

There is a bit of a mystery concerning the corrector strip. The corrector strip is used to electrically compensate for an ADF bearing error that is caused by the antenna effect of the aircraft fuselage. It was part of the ARD-7 and ADF-14 kits but so far there is no photographic evidence to indicate that it was fitted on the Avenger. A photo of a Sea Fury fighter bomber also shows a loop antenna without the corrector strip so its lack of use remains a puzzle.
 

The ADF installation on this Sea Fury also lacks the corrector strip.   (From the collection of Leo Pettipas)

This illustrates the ADF loop antenna mounting in a test aircraft of VX-10 squadron. The lack of a corrector, especially during an evaluation, is a mystery. In service, the loop antenna was mounted directly above the Observer's Mate in the mid-upper cockpit section. (DND/PAC/PA-136529 from the collection of Leo Pettipas)

The "in-service" location of the radio compass loop antenna in the 3M and 3M2 variants. (Graphic via  Leo Pettipas)

This photo shows the placement of the ADF-14 in the cockpit of an AS3 Mk2 prototype. It is assumed this is the commercial version otherwise the military version would bear a nameplate with its JETAS registered number of ARD-7.

The radio compass indicator. (Extracts from photo DND/DNS-11279 held by the Shearwater Aviation Museum)

PILOT'S RADIO CONTROLS

These were the Pilot's radio controls in an operational Canadian Avenger. The AN/ART-13 transmitter and ARB-4 receiver control boxes have been removed and likely relocated to the Observer’s Mate’s action station. This control box relocation would have relieved the Pilot of having to operate the ART-13/ARB-4 HF radio combo.  1) AN/ARC-1 VHF control box. 2) C38/ARC-5 control box.   It controlled up to four receivers. The controls for the AN/ARR-2 receiver were to the right of the white dividing line. The leftmost portion controlled the audio volume up to three other receivers.  This would include an AN/ARC-5 VHF receiver (position A) ,  AN/ARC-5 MF or HF receiver (position B) and  AN/ARC-5 MF or HF receiver (position C).  3) This addition in the vacated space is a Canadian modification. It is believed that a second ARB remote tuner was  installed at the OM's station. If that is true (and it seems logical from a crew ergonomic viewpoint) it would follow that the unknown panel in question incorporates a switching function that allows either the pilot or the OM to control the ARB receiver through their respective ARB remote tuners, but not simultaneously. The normal switching matrix protocol  would be for the last position (pilot or OM) to depress the button on the unknown panel (there would need to be a similar panel at the OM's station) to select their ARB remote tuner to control the receiver. 4) AN/APX-2 IFF controls  5) ARB-4 receiver  remote tuner. The ARB remote tuner allows the pilot to manually tune the ARB MHF radio to a frequency in one of the radio bands selected on the ARB receiver by the  Observer's Mate.  (Photo via Shearwater Museum)

Ernie Cable, Shearwater Historian, provides this explanation for the Pilot's radio controls. "The missing Pilot radio control panels in the AS 3 are for the ART-13 (MHF) transmitter and the ARB (MHF) receiver. Now the Pilot has no control over these radios, but he can still listen to the ARB and ARC-5  receivers through the Rec B and Rec C switch functions on the C38/ARC-5 control panel (The ARC-5 receive frequencies are the same as the transmit frequencies selected for the ART-13, with some exceptions.) This tells us that the ART-13 and ARB controls have been moved to the Observer's Mate’s stations since he is the one who operated the HF radios. More importantly, note that an ARB remote tuner still remains in the Pilot's cockpit; but, for the remote tuner to operate, the proper frequency band must be selected on the ARB receiver control panel which is no longer in the Pilot's cockpit. So, the unknown panel with the single push button in the place of the ART-13 and ARB control panels is "probably" a "push to control" button for the ARB remote tuner that allows the Pilot to assume control of the ARB remote tuner from the OM station.

This makes sense in that the wiring for the Pilot's ARB control panel was already in place from the previous TBM-3 configuration. Under normal operating procedures in the AS 3, the OM would have control of the ARB remote tuner.

In contrast to the previous photo, these are the Pilot's radio controls in an American Avenger. (Via Google Books)

RADIO CONTROL PANEL

June, 1953. This is believed to be the  AN/AIC-501 fitted into a test aircraft.   Click to enlarge. (From the collection of Leo Pettipas)

WIRE ANTENNA DETAILS

Feed through insulator for wire antenna feed line. (Photo PA-136533 DND/PAC by William Parrell)

On this AS-3, the forward end of the wire antenna was attached to the top of the ARC-1 antenna using strain insulator 126-SE-100. (Photo  DND/PAC PA-136533 by William Parrell)

Wire antenna, aft end detail. From left to right: Tee splice 126-TS-100, strain insulator 126-SE-100 and tension unit 126-TU-100. The Tee splice was usually at the mid point of the span.  Shown, is the installation on a TBM-3W2 (Photo PA-136539, DND/PAC by William Parrell)

This was the primary method of securing the wire antenna to the tail of the aircraft, likely an AS 3 Mk 2 in this example. (Photo PA-136538, DND/PAC by William Parrell)

AN/UPD-501 SHF DF RECEIVER

The UPD-501 was a High Probability Radar Early Warning directional finding receiver which was used to detect radar emissions on the SHF radar bands and gave some indication of the frequency in use, bearing, and the antenna rotation period. The receiver was connected to an airborne version of an horn antenna assembly.

This device was the outcome of a project initiated by Naval Headquarters, and was a contemporary of the early MAD work.  It was a wide-band dual-band electronic countermeasures (ECM) receiver system.  This project was started in the early 1950s by the National Research Council who undertook to develop "a simple ‘instantaneous’ direction-finding receiver-display for detection of non-co-operative radar transmissions expected to be of short duration".  It was designed to listen for radar emissions from submarines, surface vessels and even aircraft.  The aeronautical version featured two antennae with feed horns on them, one for X-band and the other for S-band radars, the expected enemy frequencies.  The antennae had to be in a container of proper aerodynamic design to shield them from the slipstream.  The chosen container turned out to be nothing more than a common aluminum soup pot.  A task for VX 10 was to determine the feasibility of belly-mounting the unit on the Avenger.  Although only S-band horns were fitted, a preliminary trial showed good results; in fact, a cross-country flight in early 1954 picked up all the (classified) Pinetree Line radar sites then in operation.

The original single-can unit was not practicable for housing both S- and X-band components and switching relays, so a double-can affair, with one can situated on top of the other, was devised.  Two of these two-can sets would be fitted to each aircraft, and it remained for VX 10 to determine where on the aircraft they should be mounted.  Two options were available: (1) fore and aft, with one set suspended beneath the engine cowling, the other on an arm extending rearward from the tail cone; or (2) one set on either wingtip.  The fore-aft configuration was the one chosen for the Avenger AS 3M operational aircraft, which is curious because it suffered from shielding by the fuselage and anomalous propagation of signals.  Furthermore, reception in both locations was hampered by lack of directional accuracy and false echoes from reflections of incoming signals off the fuselage and other parts of the aircraft.  The superior wingtip-mounted option was not taken for the Avenger. Interestingly enough, this somewhat problematic fore-aft configuration was also applied to those Air Force Lancasters that were fitted with AN/UPD-501.

Airborne version of the UPD-501 antenna with radome removed. (Photo courtesy RCN)

December 1953: A closer look at the early UPD-501 "soup pot" antenna enclosure on the AS3 Mark 1. (Photo by William Parrell DND/PAC/PA-136535)

AN/UPD-501 receiver. The system was made by Cossor Canada Ltd. (Photo by Jerry Proc)

Observer's Mate Action Station.  The UPD-501 receiver indicator is at the top right and a two band antenna switch is positioned to its left. Below is the AN/APS-4 display . (From publication - Operating Instructions for R.C.N. A/S-3 and A/S-3M Aircraft.  MICN. 3.10.11A , courtesy Leo Pettipas).

AN/APS-20 RADAR

The AN/APS-20 radar was first flown in an XTBM-3(W) Avenger on 5 August 1944. Responding to the system's promise, and to the increasing Kamikaze threat, the US Navy ordered co-production of the APS-20 while it was still in development. TBM-3Ws fitted with the AN/APS-20 radar entered service in March 1945, with some 36-40 eventually being constructed. Eight of these aircraft would see service with the RCN in 1952.

A TBM-3W2 prepares for takeoff from the aircraft carrier HMCS Magnificent. The bulbous APS-20 radar was employed for both air search and for ASW in order to detect periscopes and snorkel masts. At this time, it is not known what variant of the APS-20 radar was fitted into Canadian Avengers. (RCN photo via Google Books)

With APS-20 radome open. The addition of the bulbous antenna and radome gave the aircraft the sobriquet of "Guppy" (Source: U.S. Navy Naval Aviation News April 1946)

AN/APS-20 principal parts. Not all of these components were used in the Avenger. (Photo courtesy Tpub.com)

SONOBUOYS

Sonobuoys have three classifications; Passive, Active and Special Purpose. A Passive sonobuoy listens quietly for submarine sounds in the sea; this has the advantage of not alerting the submarine that it is being hunted. An Active sonobuoy uses sound pulses projected into the sea to produce an echo from a submarine, similar to “ping” from sonar. Although an Active sonobuoy locates a submarine more accurately, the sound that it actively generates into the sea has the disadvantage of warning the submarine that it is being hunted. Special Purpose sonobuoys have unique functions such as a bathythermograph sonobuoy which measures the sea temperature at various depths.

During the 1950’s, Canada, UK and USA entered into a tripartite agreement to standardize sonobuoys to facilitate interoperability. It was agreed to standardize on a common “A” size sonobuoy, 4 7/8 inches (124 mm) in diameter and 36 inches (910 mm) in length. The standardization included using common VHF radio frequencies  to transmit information from the sonobuoys to the aircraft. Today, this agreement is still adhered to by NATO countries and their allies. Originally, it was agreed to standardize on sixteen VHF channels with each sonobuoy allocated one of the  sixteen channels during manufacture but sixteen channels; however, later on, this proved to be inadequate.

After the sonobuoy enters the water, a hydrophone drops from the buoy on a suspension cable to listen for submarines. The WWII era sonobuoy, namely the CRT-1A, had its hydrophone suspended at a depth of 26 feet (8 meters) below the surface as this was thought to be the best depth at which to detect U-boats. However, as the science of transmission of sound in water and submarine technology advanced, 26 feet was deemed too shallow; therefore, the hydrophone of the SSQ-2B (next generation ) sonobuoy was suspended 40 feet (13 meters) below the surface.

To "fix" a submarine meant to ascertain its position while either on the surface or attempting to evade being tracked and attacked while submerged. The Avenger dropped smoke and flame floats to indicate to surface vessels or other aircraft the submarine's last known position as determined by visual or radar contact.  Another device used in fixing submarines was the SSQ-2B omni-directional sonobuoy, a cylindrical floating body containing a sea water activated battery, a VHF transmitter, antenna and a hydrophone. Upon entering the water the hydrophone dropped from the floating body and was suspended 40 feet (for SSQ-2) below the surface where it could detect the propeller sounds from a submerged submarine. If a submarine was detected while diving, a sonobuoy and a smoke float were dropped at the target's last known position (At night, a flame float which produced a yellow flame was dropped). The aircraft then flew a "cloverleaf" pattern around these indicators, dropping four additional sonobuoys and smoke floats at a maximum radius of 2,000 meters (2 km) in a 90° position relative to one another. By aurally monitoring and comparing the relative strengths of the submarine sounds transmitted from the sonobuoys, the Observer in the Avenger could plot a rough fix of the submarine's position, commence tracking the target and direct other cooperating ships and aircraft towards the submarine's latest fixed position for further localization and attack. The sonobuoys VHF transmitters in use during the first half of the 1950s had an effective range of about 10 miles. Internally, the Avenger could carry as many as sixteen, SSQ-2B sonobuoys, which measured 4 7/8 inches in diameter by 36 inches long (124 mm x 910 mm). The sonobuoy VHF transmissions were received by two rod antennae fitted to the bomb bay doors and fed to the AN/ARR-26 sonobuoy receiver in the Observer's station.

MAGNETIC ANOMALY DETECTOR (MAD)

This photo of an AS 3M clearly identifies the forward UPD-501 antenna beneath the engine cowling and the aft UPD-501. Also obvious is the MAD boom attached  the rear port side of the fuselage. Four zero-length rocket rails are in evidence on the lower surface of the port wing. Most photos show the MAD boom in the stowed position. (DND photo DNS-19010)

One disadvantage of the sonobuoy was that the submarine had to be making noise before it could be pinpointed. By shutting off the engine and gliding, the submarine could effectively slip out of the sonobuoy range and escape. To counter this tactic, the Navy introduced the MAD-equipped variant of the Avenger. The Magnetic Anomaly Detector, as the name implies, relies not upon the sounds made by the sub, but by changes caused in the magnetic field as it moves. Because of its limited range, MAD was unsuitable for area search. However, it was useful in pinpointing a target that had been detected by other means.

A major drawback of the available MAD equipment lay with the fact that the aircraft had to be flown at very low altitudes (50 feet was optimum) to ensure that maximum signal strength was obtained. This meant that there was very little warning when a submarine was detected. Sometimes the pilot subjected the crew to some tight, and at times, uncomfortable manoeuvers. In addition, certain constraints were imposed while the MAD head was extended: positive accelerations were not to exceed 2.5 g, and maximum permissible indicated air speed was to be 196 mph.

HOMING

During WWII, the USN started using the YE-ZB homing system on its carriers, a UHF line-of-sight system developed by Frank Akers.

A disk with twelve Morse code characters rotates in sync with a directional transmitting antenna aboard the carrier.  The antenna transmits a signal which is heard by aircraft returning to the carrier. Every 30 degrees (360/12) of antenna rotation, the transmitted Morse code character changes.  The pilots hear only one Morse code character, and that character corresponds to the carrier's transmit antenna being pointed in the direction of the pilot.  If the received letter changed, the pilot knew that the aircraft was moving tangentially to the transmission point. The pilot usually found the strongest signal and followed it back to the aircraft carrier

 The order and  placement of characters on the wheel changed daily, possibly even with each mission. The transmitter used a double amplitude modulation scheme and operated around 240 MHz -  the double modulation scheme ensured that a casual eavesdropper would hear only a dead carrier unless he had the proper demodulator in the receiver.

 The Avenger used the AN/ARR-2 VHF homing receiver sometimes called a "ZB receiver". It is fairly certain HMCS Magnificent was fitted with the YE transmitter to facilitate homing capability. Click here to see a photo of a Morse disk used in the YE system . (Ebay photo)

Location of the "homer" antenna on the Canadian Avenger. It was in fornt of the pilot , off centre towards the starboard side.

On the American Avenger the ZB homer antenna is mounted on the aft end of the starboard bomb bay door. For some inexplicable reason, the antenna on Canadian aircraft was in front of the Pilot near the starboard side. Homing antennas were usually located on the underside of the aircraft to eliminate signal shielding from a surface-based transmitter.

The Observer's main  function was navigation, hence this compartment contained instruments essential to that trade. The forward facing panel was rather sparse when compared to the aft facing panel.

The Observers Position looking aft in a AS 3M variant. At the top centre is the radio compass. To its right is the scope for the APS-4 radar. (From publication - Operating Instructions for R.C.N. A/S-3 and A/S-3M Aircraft.  MICN. 3.10.11A , courtesy Leo Pettipas).

Looking forward - port side in both the AS 3 Mk 1 and AS 3M. Not much here at all.

Looking directly forward. Note the absence of instrumentation in the lower half and the two ARR-26 sonobuoy receivers in the upper half.  This arrangement would be found in the AS 3M and 3M2 variants.

Looking forward -  starboard side. All that was here was a compass that sat in the upper right-hand corner, facing forward.  It was standard in both the AS 3 Mk 1 and the AS 3M.

All photos in this table from publication - Operating Instructions for R.C.N. A/S-3 and A/S-3M Aircraft.  MICN. 3.10.11A.

Observer's station port aft quarter in a AS 3 Mk1.(Operating Instructions for R.C.N. A/S-3 and A/S-3M Aircraft.  MICN. 3.10.11A , courtesy Leo Pettipas).

Observer's station starboard aft quarter in a AS 3 Mk1.(Operating Instructions for R.C.N. A/S-3 and A/S-3M Aircraft.  MICN. 3.10.11A , courtesy Leo Pettipas).

RADIO CALL SIGNS

When the Navy took delivery of their TBM-3E Avengers the aircraft were painted overall blue and still bore their American markings and insignia. As a preliminary measure, the American identifiers were replaced by Canadian letter codes, roundels and fin flashes.  Each machine carried three white radio call sign letters forward of the roundel on both sides of the fuselage and on the underside of the port mainplane. The first two letters were invariably "AB," the standard 826 Squadron code. The third letter was the individual aircraft's identification number and was also shown above the fin flash on both sides of the fin and each side of the cowling ring. When the aircraft were repainted in the two-tone grey scheme the radio call sign lettering remained in the same positions. Later there were minor variances in the radio call sign markings.

In 1952, the above-described system of letter codes was abolished and operational aircraft were assigned radio call numbers that for the most part corresponded to the number of aircrew carried.  Since the early AS 3 Avenger was manned by a crew of three, each machine was, in theory, scheduled to receive a 300-block number.  The system broke down when there were more aircraft than there were 300-block numbers to go around.  Since there were more Avengers than there were 300-block numbers, some of the aircraft had to be assigned numbers from another block until 300-series numbers were freed up due to write-offs of aircraft that initially carried them. At the outset, the eight Guppies were allotted the numbers 411 to 418 inclusive even though the number of crewmen normally carried was less than four. In due course, the 400-block numbers were replaced with 300-series numerals.
 

TBM-3W2 "GUPPY"AEW ELECTRONICS

	This cutaway of an American TBM-3W illustrates the amount of Air Early Warning (AEW) electronics that were jam packed into the "Guppy". The majority of it was AN/APS-20 equipment. There is no cutaway available for the Canadian TBM-3W2 at this time. (Graphic by Research Laboratory of Electronics, MIT)
	This TBM-3W cutaway gives a better idea of how the crew sat in front of Control Central. (Graphic courtesy tailhookdaily.typepad.com)

FOOTNOTES:

[1] This was noted by Keith Harrington when the Avengers were being converted to their civilian roles.

[2] With reference to manual TM 11-487D, Directory of U. S. Army Signal Equipment Radio Direction Finding Equipment (1958), it does not state who built the AN/ARD-7.  It does, however provide the Signal Corps Stock Number.  SIG 5 is (was) the Signal Corps stock list or catalog.  SIG 5 Subclass 2S lists complete equipment (sets).  The Sig Stock Number for AN/ARD-7 is 2S9300.  In the 1955 edition of Subclass 2S,  the 2S9300 entry describes AN/ARD-7 functionally, and ends with:  Lear #ADF-14 or equivalent.

[3] From "The Naval Institute Guide to World Naval Weapons Systems, 1991/92"  by Norman Friedman.

QUESTIONS:

1) Was the forward UPD-501 antenna for the X or S band in a two antenna configuration?

2) Who made the CAM-1 interphone system?

3) On page 62 of the book "Certified Serviceable" it clearly states the ARC-27 UHF radio replaced the ARC-1 VHF radio. Can anyone confirm if the Avenger was then left without any VHF capability?  It's hard to imagine an Avenger operating ashore in a civilian air traffic control environment without a VHF radio in the 1950's.

Please reply to: Jerry.Proc@sympatico.ca

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Credits and References:

1) Leo Pettipas <lpettip(at)mts.net> Associate Air Force Historian. Air Force Heritage and History 1 Canadian Air Division.
Winnipeg, Manitoba.
2) White Paper:   Grumman ASW Avenger Variants in the RCN by Leo Pettipas. June 2008
3) White Paper: Early Cold War Anti-Submarine Warfare Development in Canada by Leo Pettipas. June 2008
4) Ernest Cable - Associate Air Force Historian and  Shearwater Aviation Museum Historian <erncar(at)ns.sympatico.ca>
5) Robert  Langille  (ewcs(at)ewcs.ca>
6) ARR-3 photo http://www.history.navy.mil/library/online/radar-14.htm
7) ARR3 info  http://www.vk2bv.org/museum/arr-3.htm
8) AN/APX-2    http://www.ibiblio.org/hyperwar/USN/ref/Radar/Radar-13.html
9) ART-13 photo -  Collins Club  Radio page   http://www.collinsclubs.com/carc/b-29/radio.html
10) Keith Harrington    va7ssb(at)hotmail.com
11) Robert Downs  <WA5CAB(at)cs.com>
12) ASQ-8 http://www.tpub.com/content/radar/TM-11-487C-1/TM-11-487C-10951.htm
13) ARC-1 Control Panel. Google Books: Grumman TBM Avenger Pilot's Flight Manual
14) APN-20 Control Box  http://www.bpbsurplus.com/lc/cart.php?target=product&product_id=17878
15) ANP-1 photo  http://www.vk2bv.org/museum/apn1.htm
16) ARC-27 photo http://www.radiosamling.dk/Specifikationssider/Military_Radios/Mi_021.html
17) ARC-1 photo.  Surplus Conversion Handbook #122 by Tom Kneitel. 1964
18) ARR-2 photo http://en.wikipedia.org/wiki/File:ARC-5_RCVR.jpg
19) ARR-2 info    http://noding.com/la8ak/61.htm
20) ARC-9 info http://www.radiomilitari.com/arc9.html
21) ARR-3 diagram http://www.history.navy.mil/library/online/radar-14.htm
22) ARC-9 photo  http://www.radiomilitari.com/arc9.html
23) ARN-21 photo  http://members.home.nl/a.k.bouwknegt/
24) ART-26 info: http://www.tpub.com/content/radar/TM-11-487C-1/TM-11-487C-10945.htm
25) CMA-301 info http://www.flightglobal.com/pdfarchive/view/1957/1957%20-%200498.html
26) APX-6 http://members.home.nl/a.k.bouwknegt/index_bestanden/APX6.htm
27) TBM-3W cutaway http://tailhookdaily.typepad.com/tailhook_daily_briefing/2009/01/fligh
tdeck-friday-history-of-carrier-aew-ii.html
28) David Ross <ross(at)hypertools.com>]
 

Jul 31/10