Early in the War, the Accuracy of Bombing and the loss of RAF Aircraft and their Crews caused considerable concern. The highly critical “Butt Report”, published in 1941, concluded that a large percentage of RAF Bombers & Bombs were not reaching the actual Target, despite Crew’s claims to the contrary. The Government and the Air Ministry were extremely embarrassed about the findings and set about improving the situation.
Establishment of the Pathfinder Force
As part of the effort to improve accuracy, the Air Ministry agreed to form a Specialised Force, which became known as the Pathfinder Force (PFF). PFF Crews were Trained to accurately follow the agreed Navigational Route, marking the “Turning Points” with Coloured Flares. Having reached the Target area, they marked the start of the Bombing run with Flares and then dropped Flares and/or Coloured Markers on the Target. Bombers in the Main Bomber Stream were able to use these Indicators to identify their Turning Points & Bombing Targets. Pathfinder Techniques changed considerably throughout the War as new Technology became available.
No 8 Group (Pathfinder Force)
The Pathfinder Force (PFF) was upgraded to Group Status on 8 Jan 1943 and became No.8 Group Bomber Command.
The redoubtable young Australian Commander, Group Captain (later Air Vice Marshal) Donald Bennett, was to mould the PFF into a Force that led the way in bringing Bomber Command into the Electronic Age, and in developing Target-Marking Techniques that enabled the PFF to literally ‘Light the Way’ for Bomber Command to achieve the Accuracy & Concentration that had previously eluded it. No 8 Pathfinder Group was the only officially recognized Elite Unit of Royal Air Force Bomber Command during WW2.
Recruitment & Training
The PFF Crews thereafter found their way in the Force via varied routes; Crews or Individuals could volunteer at any time while serving with Main Force Squadrons, while Aircrew who showed promise in their Training could also find themselves Seconded into the Force. Some Crews in mid-Tour could also be transferred into PFF when numbers were needed to be made up to an Establishment where required. Recruits were given a 2-week Course in Marking Techniques at RAF Warboys before posting to a Squadron. Bennett addressed each intake personally and the Crews came to have an intense sense of loyalty, pride & professionalism in their Membership of 8 Group. The PFF Crews were also granted a Step up in Rank, & Increase in Pay, but had to do a 45 Trip Tour rather than the usual 30 Trips, for as long as they were serving in PFF. By volunteering for the PFF Airmen were initially committed to another 60 Operations which were later reduced to 45 to encourage more to join. As your number of Operations increased, your odds of surviving were radically reduced and without any doubt, regardless of their skills or Professionalism, the Key Factor to surviving was simply Luck! In the end, Arthur (Bomber) Harris was proved wrong about PFF’s effect on morale – the coveted PFF Badge allowed to be worn on their Uniforms was genuinely a sought-after achievement.
RAF Pathfinder Force 7th – 35th & 156 Squadrons – We Light the Way –
With the advent of Pathfinder Force (PFF) the Aiming Point was marked by Target Indicators (TIs). The use of TIs for Target Marking was code-named Newhaven and could be Ground Marking (Paramatta) or Sky Marking (Wanganui). The story goes that when Newhaven was being developed and they were looking to name the 2 Systems, someone asked an Australian and a New Zealander involved where they came from, and their answers became a part of the History of Bomber Command.
Pathfinder Force used 2 Navigators in each Aircraft, 1 termed the Observer, the other the Plotter. On completion of the course at PFNTU (Pathfinder Force Navigation Training Unit), after discussions amongst themselves, and with the Instructors, they were paired up and it was decided who would function better as the Observer and the other would be the Plotter. They operated in a completely blacked out Compartment. The only illumination was a small lamp the Plotter used to be able to see his Charts & Dalton Computer, and the illumination from the Observers GEE Set & H2S Cathode Ray Tube, the Plan Position Indicator. They sat side by side on a narrow bench and unless they made an effort to pull the Blackout curtain and stand up to have a look around, they saw nothing but our Instruments for hours on end. All Aircraft used were Lancasters, the Navigation Equipment was the latest, and the Pilots were all Veterans who had completed 1 Tour of Ops, and were adept at assessing them on their in-flight competency, clarity, and compatibility with the other Navigator.
Philip Dalton was a Cornell University Graduate who joined the United States Army as an Artillery Officer, but soon resigned and became a Naval Reserve Pilot from 1931 until he died in a plane crash with a Student Practicing Spins. He, with P V H Weems, invented, patented & marketed a series of Flight Computers. Dalton’s 1st popular Computer was his 1933 Model B, the Circular Slide Rule with True Airspeed (TAS) and Altitude Corrections Pilots know so well. In 1936 he put a Double-drift diagram on its reverse to create what the US Army Air Corps (USAAC) designated as the E-1, E-1A & E-1B
Squadron Crew Ranking – Every Squadron had its Crews qualified for different categories. These were…
Supporters. – These were usually the newest Crews. They flew in Support of the rest of the Squadron, same timing, same Target, and carried the same Bomb Load as the Main Force. Their Role was to support the Early Marker Crews and help achieve saturation of the Ground Defences. Their 1st Duty was to arrive at the Target on Time. Their Log & Camera picture of the Target were analysed, as were all the Logs & Camera pictures taken during all Training Flights. On all these Flights a high standard of H2S Operation was required. As they became more efficient they could be qualified for a higher ranking, and assigned to more demanding Marking Duties with Bombs & Flares.
The Categories were, in ascending order of Competence from Supporter were…
Primary Visual Marker.
Primary Blind Marker.
The names generally indicate their Role in the Attack, and exceptional standards had to be met before a Crew could qualify for the next step. Except on special Flights, Pathfinder Force did not use a Front Gunner nor a separate Bomb Aimer. The Flight Engineer was given the Training to enable him to Operate the Bombsight with additional information from the Observer. Depending on the Raid, either the Flight Engineer would drop the Bombs Visually, with information from the Observer & Plotter for Setting the Bombsight, and the Pilot would be given the Course to Fly to bring us over the Target on the proper Course. Then it was just set the Bomb Release Switches, hold the Plane steady and level for the last 5 miles to the Release Point, push the “tit”, and “Bombs Away!” and immediately change direction to get out of the way of Main Force. When it was a Blind Bombing Raid, the Observer Set the Release Switches, timed & released the Bombs & Flares from his position, based on his reading of the H2S Scan.
Aerial vertical image taken over the Moabit District of Berlin during a Raid by 33 De Havilland Mosquitos of the Light Night Striking Force. The Track of a falling Target Indicator (TI) can be seen on the right, illuminating the River Spree, and the Charlottenburger Chaussee, running from top right through the Tiergarten to the Brandenburger Tor & Unter den Linden. The other Light sources are German Searchlights.
In late 1944, the PFF was utilising a number of specific methods to carry out their roles, based on the likely visibility over the Target Area. These included:-
The “Parramatta” Ground Marking method, which was used when the Weather Forecast suggested good visibility over the Target Area.
The “Newhaven” Ground Marking method, which was used when the Forecast suggested some visibility over the Target Area.
The “Wanganui” Sky Marking method, which was used when the Forecast suggested minimal visibility over the Target Area.
Each Pathfinder Aircraft was assigned a specific Role for each Mission, based on their skills & experience. These Roles were dependent on the method(s) being utilised for the Mission.
Parramatta required “Blind Markers” and/or “Visual Markers” to drop coloured Target Indicators (TI’s) to identify the Aiming Point. “Blind Markers” utilised Navigational Aids to identify the Target “Visual Markers” utilised Visual contact through the Bombsight to identify the Target.
Newhaven required “Blind Illuminators” and/or “Visual Illuminators” to drop Flares to light up the Target Area. When the area had been lit up, “Visual Markers” would visually identify the Target and drop their Coloured Target indicators (TI’s) to identify the Aiming Point.
Wanganui required “Blind Markers” to drop Coloured Parachute Flares (Sky-Markers) to identify the Aiming Point. As well as being a standard method, it was used in an emergency if Cloud Cover, Smoke Screens etc obscured the Target on Arrival. The following is an example of part of a 1944 briefing outlining the Pathfinder Method(s) to be used:
As the Flares and Target Indicators only burned for a short while (approximately 3 minutes), Pathfinder Aircraft were spread throughout the Main Bomber Stream to repeat the marking process. These were known as “Backers Up” or “Visual Centrers”. To gain experience, a new Pathfinder Crew would be assigned the role of “Supporter”. They would fly as part of the initial wave of Pathfinders to “Support” the Markers. The Raid would be coordinated by a “Master Bomber”, circling above the Target. He Broadcast Instructions to Crews advising them on where to drop their Flares, Target Indicators & Bombs based on his view of where the Target was in relation to the Coloured Indicators on the Ground.
Primary Blind Marker, if Cloud conditions were less than 7/10ths (10/10ths is Full) and conditions appeared favourable for Visual Marking, were to mark Aiming Point blindly with Target Indicator Green and also drop bundles of Flares White Hooded.
If more than 7/10ths cloud they were to drop Target Indicator Green and Release Point Flares Red/Green Stars. Visual Markers were to mark Aiming Points with Target Indicator Red after definite visual identification, otherwise retaining their Target Indicators. Flares White Hooded could also be dropped at the Captain’s discretion to assist Visual Identification.
Blind Backers Up, if Visual Marking was possible, were to retain their Release Point Flares (Red with Yellow Stars) and drop Target Indicator Green and Bombs blindly.
If their Special Equipment was unserviceable (HS2 Primitive Radar) a long way from the Target, they could revert to Visual Backers Up.
If Cloud conditions rendered Visual Identification impossible, they were to drop Release Point Flares and Target Indicator Green blindly. Visual Backers Up were to keep the Aiming Point marked throughout the Attack with Target Indicator Green, aiming at the Target Indicator Red in the early stages if visual marking was possible, otherwise Target Indicator Green.
If Cloud obscured Target Indicator, they were to retain Target Indicators and Aim Bombs at the Release Point Flares. Supporters were to Bomb the Aiming Point by Special Equipment. If unserviceable they were to bomb visually or on good Dead Reckoning unless markers had already dropped, in which case they were to Bomb the centre of Target Indicators seen or the Release Point Flares.
The Initial Ground Marking (Newhaven) was done by PFF Mosquitoes Flying at 30,000ft using a system code-named Oboe which, like Gee, was line-of-sight. It was claimed that a Marker could be placed within 100 yards of the Aiming Point. (The Americans claimed they could plant a Bomb in a Pickle Barrel from 25,000 feet using their Norden Bomb-Sight). Targets beyond the Range of Gee & Oboe were located by the use of Loran & H2S and marked either Visually or with H2S. The use of Target Indicators also solved the problem of the Main-force finding the Target. On deep penetrations beyond the Range of Gee, even after a long period on Dead Reckoning, the 1st of the Main-force would be able to see the TI’s go down, and once the Attack started the Fires could be seen from far away by the later Crews. Control of the Attack by a Master-Bomber, which was 1st used in the Attack on the German Experimental Station at Peenemunde where the V1 & V2 were developed, involved the Master Bomber going down to 3500 ft to see which TI’s were closest to the Aiming Point, and calling the Main Force to ‘Bomb on Red‘ or ‘Bomb on Green‘ as the case may be. At 1st this was done in a Lancaster, then in a Mosquito, and on occasions, Leonard Cheshire used a Mustang. Other PFF Aircraft known as Backers-up were spaced along the Stream to re-Mark the Aiming Point at regular intervals as the TI’s burned out or were blown out by Bombs.
The RAF’s pyrotechnics were brilliant, with the Sky Marking being particularly spectacular as brilliant Red parachute-flares dripping brilliant Green stars or Green Flares dripping Red stars were suspended in mid-air. Unfortunately, Sky Marking was probably even less effective than Bombing with H2S because the Parachutes drifted with the Wind. It was probably only used as a last Resort, and seldom used on Operations. Having gone say all the way to Chemnitz (almost on the Czech Border) we found the Target under 10/10ths Cloud. Presumably, it was better than carting the load home again.
GEE is actually a short-range (250 mile) hyperbolic curve Navigation System, same principal as LORAN. Measures difference in time of arrival of Radio Pulses transmitted exactly at the same time from 2 Towers about 70 miles apart. Measurements in microseconds (millionths of a second or 1⁄1,000 of a millisecond). The Oscilloscope shows the relative timing of the 2 Radio Signals and is displayed on a Cathode Ray Tube. Places Aircraft or Ship on a hyperbolic curve. Two separate Towers transmit a 2nd Signal providing a position fix where coloured hyperbolic curves Cross. The time required 15 seconds. Accuracy 25ft at sea level. Two traces are shown on the CRT and permit landing an Aircraft in a pea soup English Fog. The GEE Box is user-friendly, easy to operate, and was used very effectively by both the RAF, USAAF & Navy. The night of D-Day would have been a disaster of collisions in the Channel & the Air without GEE.
WWII Bombing Navigation System – GEE-H was the successor to OBOE because OBOE could only handle 1-Aeroplane in a period of 1000 Plane Bombing Raids. GEE-H could handle 8 Bombing Formations at a time. The Navigator of the Aircraft became the Operator and the Cat and Mouse became Transponders
WT Broadcasts to Aircraft
Group made a WT broadcast on the hour & ½-hour, and the W/Op would listen out for Messages. In the early stages of the Outward journey, it was possible that the Operation may be scrubbed – though it seldom happened – and the prospect of pressing on when everyone else had turned for home was an incentive not to Miss a broadcast. Sometimes if Pathfinder Force, who were ahead of the Main-force, discovered that winds were significantly different to those that were Forecast, this information would be sent back to Group which would relay it to the participating Aircraft. Occasionally, Main-Force Aircraft would take part in Jamming German Fighter Frequencies – known as ‘tinselling‘. The W/Op would tune his Transmitter to a nominated Frequency and Transmit the noise picked up by Mics placed in the Radio Power-packs (motor-generators). The din was considerable.
In addition to the normal Navigational Aids (see also ‘Blue Book Series’, Book 7: British Navigation Systems) the Aircraft carry the following Special Equipment:
- 4-engined Aircraft (Lancaster and Halifax):
- Rotterdam (H2S) for the location of Target and bombing without ground visibility;
- Hyperbola Navigation Instrument (Gee);
- Identification Friend-Foe (IFF); acoustic Night-fighter warning instrument ‘Monica‘;
- Visual night-fighter warning instrument (Cathode Ray Oscilloscope) ‘Fish Pond‘
- Provision for Bomb-release in the Cabin as well as in the Navigation Room.
To perform their role, Pathfinder Crews were provided with Aircraft equipped with the latest navigational technology, including Gee, Oboe & H2S. Their Bomb Loads were mission specific and, depending on their role, contained a mixture of Bombs, Flares & Target Indicators. Target Indicators were specially adapted 250lb Bomb Casings containing 60 coloured pyrotechnic candles (red, green, yellow). At the designated height, the casing would explode, releasing the ignited coloured candles which would float down to the ground. These would burn for about 3 minutes, providing a coloured “Aiming Point” for the Main Bomber Stream. Sky Markers consisted of an encased candle flare attached to a large parachute. When released it would float down to the ground, igniting at a designated height; pieces of the candle would fall off, creating a vertical chain of light.
H2S (Mapping Radar) – (The Start of Television)
Another new and wonderful piece of equipment followed at least it seemed marvellous at the time was the H2S. This was an early sort of television. Radar signals were sent to the ground area below the Aircraft and repeated back to a receiver in front of the navigator. The ground appeared grey on our little TV screens, Towns were black and Water white or no colour. We were thus able to get a picture in black & white (somewhat fuzzy at times) including Coast Lines, Rivers & Towns. So when we arrived at our area where the GEE was not accurate, the H2S gave us pictures for identification purposes and worked even through heavy cloud. H2S was a triumph of ingenuity with the development of the cavity magnetron, cobbled together with string, sealing wax & the shell chamber of a 6-shooter (or was it an 8-shooter?) to generate a radio frequency with a 10 cm wavelength for mapping Radar. H2S had its limitations. It gave its best result when there was water in the picture, either Coastal or Rivers & Lakes to give a good definition.
Unfortunately, despite assurances to the contrary, the German Night Fighters could ‘home’ on it. For propaganda purposes, much was made of the ability of the Allies to Bomb through the cloud, when in fact, blind bombing was just that. The great weakness of H2S in this regard was that the scanner, housed in a half-teardrop fairing on the underside of the Fuselage behind the Bomb-bay, rotated in a horizontal plane and produced a blank hole in the centre of the Screen. In other words, you could see where you were going and where you had been, but you could not see the bit that was of greatest interest to you – what was directly underneath – so bombing with H2S involved a timed run from some point before it disappeared from view, which was rather hit & miss. H2S was best used selectively & briefly.
Fortunately, Aircraft G George was fitted with Loran instead of H2S, although the installation of Loran was the exception rather than the rule in Main-force Aircraft. LORAN, short for long-range-navigation, was a hyperbolic Radio Navigation system developed in the US during WW2. It was similar to the UK’s Gee system but operated at lower frequencies in order to provide an improved range up to 1,500 miles (2,400 km) with an accuracy of 10’s of miles.
There were 3 main methods of Target Marking; the 1st was visual ground marking which had the codename NEWHAVEN. The 2nd method was blind ground marking; predominately using H2S ground mapping radar to locate the Target, this method had the codename PARRAMATTA. The 3rd method was sky marking when the Target Indicator parachute flare slowly descended into and coloured the cloud; this method had the code name WANGANUI. If OBOE equipped Mosquitos undertook this method it had the code-name MUSICAL WANGANUI.
These codenames were derived from the Hometown of 3 Members of Bennett‘s HQ Staff. The code words were initially chosen by asking 3 Bomber Command Personnel in the Operations Room where they came from. One was from Newhaven, England, one from Parramatta, New South Wales, & one from Wanganui, New Zealand. PFF crews found themselves given ever increasingly sophisticated & complex jobs and tasks that were constantly modified & developed tactically during the Bombing Campaign from 1943 until the end of the War. Some of the more usual tasks were as:
“Finders“; these were 8 Group Aircraft tasked with dropping sticks of illuminating flares, firstly at critical points along the Bombing Route to aid Navigation and keep the bomber stream compact, and then across the approximate Target Area. If conditions were cloudy then these were dropped using H2S Navigational Radar.
“Illuminators“; were PPF aircraft flying in front of the Main Force who would drop markers or Target Indicators (TI’s) onto the designated ‘Aiming Point‘ already illuminated by the “Finders“. Again, if conditions were cloudy H2S Navigational Radar was used.
These TI’s were designed to burn with various colours to prevent the German defences lighting decoy fires. Various TI’s were dubbed ‘Pink Pansies’, ‘Red Spots’ & ‘Smoke Puffs’. “Illuminators” could include Mosquitos equipped with ‘Oboe‘ if the Target was within the range of the highly accurate Oboe Bombing Aid.
“Markers“; would then drop incendiaries onto the TIs just prior to the Main Force arrival. Further “Markers” called “Backers-Up” or “Supporters” would be distributed at points within the Main Bomber Stream to re-mark the original TI’s as required. As the War wore on, the highly dangerous role of “Master Bomber” was introduced as a sort of Master of Ceremonies, the appointed Pathfinder (usually a highly experienced Senior Officer) circling the Target and broadcasting instructions to both Pathfinders & Main Force Aircraft, correcting Aiming Points and generally coordinating the Attack. The proportion of Pathfinder Aircraft to Main Force Bombers varied enormously according to the difficulty and location of the assigned Target; 1 to 15 was common, though it could be as low as 1 to 3.
By the start of 1944 the bulk of Bomber Command was now Bombing within 3 miles of the PFF Indicators; a huge improvement in accuracy. The success or failure of a Raid now depended overwhelmingly on the Pathfinder’s Marker Placement and how successfully further marking was corrected. No.8 Group PFF flew a total of 50,490 individual Sorties against some 3,440 targets. The cost in human lives was grievous. At least 3,727 members were killed on Operations. Bennett was very much a hands-on Commander who kept in close touch with the Men & Stations under his Command. He never allowed himself to become removed from the actualities his Crews were facing, and even went to the extreme of flying surreptitiously on Operations, something which had been categorically forbidden by Harris. Bennett could be coldly ruthless towards those who did not achieve the high standards he demanded. Yet he was not a hard man, and his involvement was such that he was emotionally affected by the loss of his Crews. As the pressures of the Bombing Campaign mounted, he lost many people whom he regarded as good friends. He got to know most of the Senior Pilots fairly well, and when they went missing it was a personal blow. Occasionally, when driving home from a Squadron Base in the early hours of the morning after learning of yet another tragic loss, he found it hard to avoid breaking down and shedding a few tears.
The Mosquito was used highly effectively, forming its own unofficially titled Light Night Strike Force which operated virtually continuously, harassing the Enemy even when weather conditions kept the ‘Heavies’ on the ground.
About an hour from home there would be a Weather Report, and occasionally, a diversion to another Airfield when Fog closed your Base. On one such occasion, we landed on FIDO – ‘Fog Intensive Dispersal Operation’. Petrol in pipes on both sides of the runway was ignited to burn off the Fog. As I recall, it was said to consume 1500 gallons of petrol per minute at ‘startup’, and 1000 gpm in ‘cruise’. There would have been more than 2 miles of pipe. I believe that the number of installations and the uses of FIDO were few, but it was considered that under certain circumstances it would be cost-effective. It was also rather lumpy.
RAF 156 Squadron at Upwood
Photoflash Bomb was used for Night Photography and developed so that planes engaged in night photography reconnaissance need not be limited to low altitude. In appearance, the Bomb resembled a conventional light case bomb. It used an M111A2 fuse in the nose but was issued unfused. It also had 2 suspension bands for rack and shackle suspension. The Bomb had a box-type tail with a square drag plate closing off the tail vane assembly. When the bomb was dropped the arming wire was pulled, starting the mechanical time fuse. When the time set on the fuse had elapsed, the fuse booster ignited the flashlight powder. The resulting flash of light lasted for about 1/5th of a sec and had a peak intensity of approximately 500,000,000 candlepower. Because of the brilliance of the Flash, it would have been detrimental to the Observers vision to watch the explosion of a Photoflash Bomb. Extreme care was needed to be exercised in handling these Bombs as the charge was very sensitive to Friction, Shock & Temperature.
Radar Devices in a Lancaster
A fully equipped Plane had 40-50 Radio “Boxes” using more than 300 valves. This diagram indicates how many navigational aids radar provides.
(1) H2S Scanner, housed in a blister below the RAF roundel.
(2) Wireless telegraphy link with Group HQ
(3) “Gee” System of Navigation, based on information from a series of Ground Stations.
(4) As homing Bomber approaches the Coast, radio track guides (using Standard Beam Approach aerial) assists the Navigator.
(5) Medium Frequency Beacons provide Direction-finding facilities, using loop aerial inside plane.
(6) Main Beam Approach Beacons give steady signal tone if Pilot is on the correct line of approach to Aerodrome; too far to Port, he hears series of Morse Dots, too far to Starboard a series of Dashes.
(7) Airfield Signals Operations and flying control are all linked by ‘phone with
(8) the Airfield’s high-frequency D/F Station, Flying Control has a VHF link with aerial
(9) & (10) the Inner Marker Beacon on the Aerodrome boundary, and Outer Marker Beacons 2 miles away give the Pilot his distance from the Runway in final stages of a Beam Approach, using the dipole aerial.
(11); and a “Darky” or emergency radio-telephone link to the ordinary R/T aerial, if all other Radio aids fail.
(12) VHF communication with other Aircraft.
(13) Medium Frequency D/F Stations, which are widely spaced, up to 6700 miles apart. The Aircraft uses trailing aerial wound off a drum.
(14) IFF-Identification Friend or Foe – system with a special aerial. IFF distress version is used by Aircraft in difficulties to call the ground stations attention.
(15) Fighter warning equipment, warns Bomber Crew against aerial attack.
(16) “Mountain Goat” device gives audible warning of nearby Mountains; ground installations need to be erected on the Mountains.