IR and Aerial Reconnaissance

[Smiffy]

I know that infra-red photography was used in aerial reconnaissance from about 1917, but it wasn't widely used until the 1970s.

I read recently that shortly after the outbreak of war, in 1939, the Royal Navy used catapult aircraft, from cruisers, particularly "HMS Ajax", to conduct IR photo-recon of the Brazilian coast, because it was thought that the Germans might try to establish a secret U-boat base there.

Given the state of the science of IR photography at that time, and the high daytime temperatures, would this have been possible in daylight? Would there have been enough temperature differential for the camera to pick out detail through the forest cover, by day, or did they have to operate by night?

I asked my father, who had some experience of catapult aircraft, if they ever operated at night. He said it was not unusual to launch an aircraft an hour or so before dawn, but he never saw a recovery attempted at night.

[Ed Rotondaro]

I know that infra-red photography was used in aerial reconnaissance from about 1917, but it wasn't widely used until the 1970s.

I read recently that shortly after the outbreak of war, in 1939, the Royal Navy used catapult aircraft, from cruisers, particularly "HMS Ajax", to conduct IR photo-recon of the Brazilian coast, because it was thought that the Germans might try to establish a secret U-boat base there.

Given the state of the science of IR photography at that time, and the high daytime temperatures, would this have been possible in daylight? Would there have been enough temperature differential for the camera to pick out detail through the forest cover, by day, or did they have to operate by night?

I asked my father, who had some experience of catapult aircraft, if they ever operated at night. He said it was not unusual to launch an aircraft an hour or so before dawn, but he never saw a recovery attempted at night.

Smiffy:

Now that's interesting stuff. Dennis, time to step up to bat and find the info!

[Smiffy]

I forgot to mention my source, it was Richard Woodman's new book about the Battle of the River Plate.

[old_pop2000]

I forgot to mention my source, it was Richard Woodman's new book about the Battle of the River Plate.

With the war starting in September 1939 and HMS Ajax being involved in the Battle of the River Plate then going to Chatham Docks for repair in December, it does not leave much time for this type of survey, but does not exclude it.

On 3 Sept. she was off of the coast of Uruguay sinking A German ship.

On 4 Sept. she did the same thing again, same location

On 5 Dec. She intercepted the German ship Ussakuma off of Argentina

On 10 December. She was involved in the Battle of the River Plate.


The photo reconnaissance mission was probably conducted from 3 September to 5 December. Bahia Blanca where she intercepted the Ussakuma is located south of the River Plate. Near IR photography was possible during that time period, and she was in the area at the time. Nothing precludes a catapult aircraft from flying at night, except that she would have to land in the water, in the early morning hours. So, If she left just before dawn, she could perform such a mission. I can't see anything that would preclude such a mission. I haven't found anything concrete that says that she did.

[Smiffy]

I would assume that making reconnaissance overflights of a neutral nation was something that the British would wanted to keep quiet about. These missions would surely have been classified Top Secret and the records were probably filed away under the "50 Year Rule".

Most of the books about the Spee / Plate campaign were written within 50 years of the events and their authors would not have had access to this information. When the records were released, in 1989 or 1990, I suspect that no one thought it was of any significance any longer.

I assume they were flown in darkness, because of the state of the art of IR photography at the time and also the need for secrecy. I can see no major problem in launching from a cruiser at night, as long as there was a reasonable calm sea. The ship could use a searchlight, or, more likely, a signal projector, to illuminate the surface of the sea in order to give the pilot a reference point.

Recovery would have to have been in daylight. Night landings, on the open sea, especially in a seaplane like Ajax's Seafox, are very risky and only attempted in an emergency. Even landing in twilight is difficult and trying to crane the aircraft back aboard in the dark would have been inviting disaster. I know that a Walrus could be recovered while the ship was doing 15 knots, but the Walrus was a flying boat and much more seaworthy than a seaplane.

Ajax had time to carry out this mission in September, before the "Admiral Graf Spee" made her first kill on 30th September.

[Ed Rotondaro]

I would assume that making reconnaissance overflights of a neutral nation was something that the British would wanted to keep quiet about. These missions would surely have been classified Top Secret and the records were probably filed away under the "50 Year Rule".

Most of the books about the Spee / Plate campaign were written within 50 years of the events and their authors would not have had access to this information. When the records were released, in 1989 or 1990, I suspect that no one thought it was of any significance any longer.

I assume they were flown in darkness, because of the state of the art of IR photography at the time and also the need for secrecy. I can see no major problem in launching from a cruiser at night, as long as there was a reasonable calm sea. The ship could use a searchlight, or, more likely, a signal projector, to illuminate the surface of the sea in order to give the pilot a reference point.

Recovery would have to have been in daylight. Night landings, on the open sea, especially in a seaplane like Ajax's Seafox, are very risky and only attempted in an emergency. Even landing in twilight is difficult and trying to crane the aircraft back aboard in the dark would have been inviting disaster. I know that a Walrus could be recovered while the ship was doing 15 knots, but the Walrus was a flying boat and much more seaworthy than a seaplane.

Ajax had time to carry out this mission in September, before the "Admiral Graf Spee" made her first kill on 30th September.

Smiffy:

It's important to keep in mind that the RN led the world in night time naval aviation as witnessed by the raid at Taranto.

[Smiffy]

My Father was an air gunner in Swordfish from 1936-41. He has a lot of night flying hours in his log book. All from carriers or land bases. Night flying by catapult aircraft, he tells me, was rare but not unheard of. He, personally, never came across a night time recovery of a catapult aircraft at sea. Before the wartime intake of aircrew began to come out of training, the pilots in the ships' flights were usually Lieutenants with several tours in carrier squadrons behind them, so they would have been competent night flyers.

I believe that the RN passed a lot of expertise in night operations to the USN during the "USS Wasp's" time with the Home Fleet in 1942, while proving that a "Wasp can sting twice," as Churchill put it.

[Ed Rotondaro]

My Father was an air gunner in Swordfish from 1936-41. He has a lot of night flying hours in his log book. All from carriers or land bases. Night flying by catapult aircraft, he tells me, was rare but not unheard of. He, personally, never came across a night time recovery of a catapult aircraft at sea. Before the wartime intake of aircrew began to come out of training, the pilots in the ships' flights were usually Lieutenants with several tours in carrier squadrons behind them, so they would have been competent night flyers.

I believe that the RN passed a lot of expertise in night operations to the USN during the "USS Wasp's" time with the Home Fleet in 1942, while proving that a "Wasp can sting twice," as Churchill put it.

Smiffy:

It is interesting to note that the USN relied very heavily on radar for night operations. At first it was radar equipped TBF Avengers and PBY Catalinas (a very effective night bomber by the way).Then the Avengers acted as spotters for Hellcat fighters (Butch O'Hare the famous USN pilot was killed during a night action, possibly by friendly fire). Finally Hellcats and Corsairs were equipped with radar and operated on their own. Did the Swordfish ever carry radar? Doesn't look like it would have the space to do so, but I could be wrong. Hats off to your Dad for his brave service. I'll hoist a pint for him.

[Smiffy]

Smiffy:

It is interesting to note that the USN relied very heavily on radar for night operations. At first it was radar equipped TBF Avengers and PBY Catalinas (a very effective night bomber by the way).Then the Avengers acted as spotters for Hellcat fighters (Butch O'Hare the famous USN pilot was killed during a night action, possibly by friendly fire). Finally Hellcats and Corsairs were equipped with radar and operated on their own. Did the Swordfish ever carry radar? Doesn't look like it would have the space to do so, but I could be wrong. Hats off to your Dad for his brave service. I'll hoist a pint for him.

The Swordfish could carry anti-ship radar. Lots of space in the cockpit, if you don't take the gunner along. Aerials rigged between the wings. Very effective as A/S aircraft flown from MAC ships and also night coastal patrol.

I believe the first air intercept radars in the FAA were fitted in Fireflys. I know some Fulmar squadrons trained as night-fighters but I don't think they had radar.

Incidentally, the gunner of a FAA Avenger, flying a night anti-E-boat patrol in the Straits of Dover, once shot down a V-1 flying bomb. Probably the only time a turret gunner ever did so, I believe the Avenger was being overtaken by the V-1 at the time.

[Ed Rotondaro]

The Swordfish could carry anti-ship radar. Lots of space in the cockpit, if you don't take the gunner along. Aerials rigged between the wings. Very effective as A/S aircraft flown from MAC ships and also night coastal patrol.

I believe the first air intercept radars in the FAA were fitted in Fireflys. I know some Fulmar squadrons trained as night-fighters but I don't think they had radar.

Incidentally, the gunner of a FAA Avenger, flying a night anti-E-boat patrol in the Straits of Dover, once shot down a V-1 flying bomb. Probably the only time a turret gunner ever did so, I believe the Avenger was being overtaken by the V-1 at the time.

Smiffy:

That makes sense, you don't need the gunner at night on anti-submarine patrols.

[Smiffy]

From 1943 onwards, Swordfish flown both by the Fleet Air Arm and RAF Coastal Command, in the primary ASW role, carried Air to Surface radar mounted under the fuselage, in lieu of a torpedo. The main offensive armament being 8 rocket projectiles with 60 pound HE warheads, or 25 pound solid (steel spear) heads.

The very last operational sortie flown by a British aircraft in the European Theatre in WW2 was a patrol by a RAF Coastal Command Swordfish.

[Ed Rotondaro]

From 1943 onwards, Swordfish flown both by the Fleet Air Arm and RAF Coastal Command, in the primary ASW role, carried Air to Surface radar mounted under the fuselage, in lieu of a torpedo. The main offensive armament being 8 rocket projectiles with 60 pound HE warheads, or 25 pound solid (steel spear) heads.

The very last operational sortie flown by a British aircraft in the European Theatre in WW2 was a patrol by a RAF Coastal Command Swordfish.

Smiffy:

The UK certainly got their pound's worth out of the Stringbag in my opinion.