How did RAF ground crew set up a fighter aircraft so that it would be an accurate gun platform for its pilot? What was the layout of RAF Kenley like in 1940? What was the daily routine of ground crew servicing the fighter aircraft based at Kenley?
In 2005 Chief Technician Ronald Pountain BEM, who had been a young armourer working on Spitfires with No. 64 Squadron at RAF Kenley between 16 May and 18 August 1940, recorded his WW2 experiences in 47 closely-typed pages which now reside in the Imperial War Museum.1
Table of contents
Harmonising an aircraft’s guns
Aircraft pens at Kenley
A tour of No. 64 Squadron at Kenley 1940
… and return
Harmonising an aircraft’s guns
‘Harmonisation’ ensured that all the bullets fired from a fighter’s eight machine-guns converged at a single point several hundred yards ahead of the aircraft. Chief Technician Pountain explained how it was achieved:
A strange discrepancy in some histories is that of the harmonisation of aircraft guns. I recently heard one TV programme claim that harmonisation was carried out by setting up the aircraft in front of a stop butt and firing the guns. What rubbish!
Aircraft were jacked up and levelled in the fore and aft and lateral planes. Plumb lines were dropped from fixed points on the underside of the fuselage on the precise centre-line.
A harmonisation diagram was lined up on the plumb lines exactly 50 yards from the front plumb line. The harmonisation diagram was a metal frame, with a centre upright carrying horizontal arms on which were eight discs – one for each machine gun. These discs, from inboard to outboard, were coloured red, blue, yellow and green. Also there were two discs, one red with a white vertical cross for the camera gun and one while with a vertical black cross for the gunsight.
The guns were cocked and a bore sighting instrument inserted into the breech which allowed the armourer a clear view down the barrel. The gun was then adjusted until the appropriate disc was centred in the barrel. A sighting unit fitted into the camera gun in place of the film magazine held the shutter open and allowed a view of the disc. The gunsight was viewed direct.
The harmonisation used on particular squadrons was often determined by the squadron’s Commanding Officer. Certainly on 64 Squadron the harmonisation was determined by Squadron Leader McDonnel in consultation with Sergeant Spencer, the Sergeant Armourer. Our guns were harmonised to give a six-foot diameter cone of fire at 200 yards.
Compared to old-fashion gunsights made of metal and wire, by the time of the Battle of Britain aircraft fighter gunsights were remarkably sophisticated, as Chief Technician Pountain explained:
What of the gunsight? It was a Mark 5 Reflector Gunsight, made of bakerlight in the form of a vertical tube. The bottom was closed by a removal filament (lamp) holder and above the filament was a graticule.* The graticule’s image was reflected up the tube, through a lens to enlarge the image, and then onto a reflector screen.
The pilot, looking through the reflector screen, saw the graticule image apparently imposed on his target aircraft. The image consisted of a central dot with two concentric rings around it. There were also two horizontal lines level with the central dot. The distance between the inner ends of these two ‘range’ bars was adjustable.
There were two adjusters on the sight casing, formed of knurled rings. The upper ring was calibrated in yards from 100 to 400, in 50-yard increments. The lower ring was calibrated in feet from 40 to 100 feet, in 10-foot increments.
The pilot was required to set the range at which he intended to attack, recognise the target aircraft and remember its wingspan in feet. He set this value on the gunsight before starting his attack. When carrying out his attack, the pilot knew that when the wings of his target aircraft just filled the gap between the inboard ends of the target bars he was at the correct range to open fire. But remembering an enemy aircraft’s wingspan and making two separate adjustments in the heat of air combat was not very practical.
What we did, therefore, was to set the range adjuster to 200 yards and secure it in place with a piece of sticky tape. We then set the span for a (German) Messerschmitt Bf 109 fighter and painted a red dot on the span adjuster to coincide with the setting arrow. This position was also close enough to serve for the Junkers 87 (Stuka dive bomber). Then the span for a Junkers 88 bomber – mark it with a yellow dot. Finally, the span for the Heinkel 111 bomber which we marked with a green dot which served also for the Dornier 17 and 215 bombers. With this arrangement, the pilot had only to identify his target aircraft and set the appropriate coloured dot. Just one of three choices.
* A grid of horizontal and vertical lines.
A single round of ammunition comprised a bullet and an explosive-filled brass cartridge case. When Chief Armourer Pountain spotted a photo of an armourer with a belt of ammunition draped around his neck he was not amused:
He would have been shot! Ammunition belts were made up by the station’s armoury personnel in the ammunition dump.
Cartridges were linked together by spring-steel links. Each link had two circular clips on one side and a single clip on the other side. The single clip fitted between the two clips and the inserted cartridge held the links together. On firing, as the cartridges were withdrawn (from the gun’s breech) the loose links were ejected, together with the empty cartridge cases.
Belts were made up generally with two ball (solid bullet) cartridges, two armour-piercing cartridges and two ‘De Wilde’ cartridges, followed by two more ball cartridges etc. The De Wilde cartridges had a hollow bullet filled with filled with an explosive/incendiary mixture and they were very effective in setting target aircraft on fire.
Belts were assembled on an assembly jig and then passed through a belt-positioning machine which positioned each cartridge in the belt very precisely. Every armourer knew that one cartridge in a belt that was as little as one-sixteenth of an inch out of place would ALWAYS cause a gun stoppage, so belts were handled with great care and never thrown about – or carried around the neck.
Aircraft pens at Kenley
Work on lengthening Kenley’s runways and building its aircraft dispersal points, or pens, was completed by March 1940, just time for the Battle of Britain. Two months later No. 64 Squadron arrived and Chief Technician Pountain described the aerodrome’s pens:
All RAF Stations had aircraft dispersal points constructed in the years before the war; the stations in the south-east had blast pens built also and they were of two types. ‘C’ type pens were built as three-sided pens capable of housing two aircraft side by side with enough room for either aircraft to taxi away without disturbing the other. ‘E’ type pens were similar but with a dividing wall between the aircraft.
The walls of the pens were some 10 feet high and shaped like a truncated triangle. The back wall formed an air raid shelter with a massive steel door. Crews working in a particular pen used the air raid shelter to store toolkits and other items of equipment. The armourers stored re-arms of ammunition in the shelters and on 64 Squadron we always tried to keep six re-arms available in the shelter at all times.
A tour of No. 64 Squadron at Kenley 1940
Chief Technician Pountain takes us for a tour of the airfield as it was in May 1940. Starting at what is now the site of No.615 Gliding Squadron’s green hanger:
Travelling around the peri-track at Kenley from east to west one came first of all to three ‘C’ type blast pens housing 64 Squadron’s ‘A’ Flight aircraft. There were never more than six aircraft in the pens, so where the seven or nine pilots were running to (he was referring to newsreel films of the day) is a mystery: perhaps they were playing musical chairs with the fighter aircraft.
Next came a large wooden hut housing ‘A’ Flight and ‘B’ Flight offices and the groundcrew crew room with lockers, toilets and wash basins. On one side of the hut was a half-height shelter which housed oxygen trollies and charging points for trolley accs. A trolley acc was a two-wheeled cart housing large lead acid battery and it had a 12-foot long heavy-duty lead with a connector plug on the end.
An on-off switch was fitted on the cart body and the lead plugged into a socket on the starboard (right) side of the Spitfire’s fuselage just forward of the leading edge of the wing. The trolley acc provided power to the aircraft while it was being serviced and also power for starting the might Merlin engine. These trolley accs were serviced, checked and re-charged by the Flight electricians.
Continuing around the peri-track next came another large wooden hut. It housed the 64 Squadron’s op room and the pilots’ crew room and a locker room with toilets and wash basins.
Next came a further three ‘C’ blast pens housing ‘B’ Flight’s aircraft. A couple of hundred yards further on and this set up was repeated. This was the home of No. 615 Squadron.
Ground crew worked incredibly long hours during the Battle of Britain. They were up a little earlier than the pilots to ensure the aircraft were ready to fly as soon as possible each day. And a lot needed doing before they could confirm the aircraft was ok to fly. Chief Technician Pountain explains what a typical day was like for an armourer, including what was required of ground crew during a “Scramble”:
Reveille was at 4.30am, breakfast from a quarter to five until a quarter past and we had to be at the hangar, washed and shaved, and having had breakfast by 5.30. Flight Sergeant Wilson did a quick head count and we boarded the lorry to be taken round dispersal.
First job, daily inspection. For me, an armourer, that meant:
- First of all, taking off the 14 access panels. A Spitfire armourer’s most important tool was a good screwdriver ground to exactly fit the DZUS fasteners which secured the aircraft’s panels.
- Next was to unload the eight guns and clean them using a cleaning rod and 4 by 2. This was a flannelette cleaning material supplied in rolls four inches wide and with red cross lines two inches apart. One piece, torn off the roll and fitted to the cleaning rod cleaned a gun barrel perfectly. Other pieces, oiled with anti-freezing oil, were used to clean other parts of the gun. A really clean piece was used to clean the gunsight lens and reflector glass.
- Having cleaned the guns, I checked that the trolley acc was plugged in and switched on.
- I then went under the starboard (right) wheelbay and set the ‘safe and fire’ switch from Safe to Fire. Fighter aircraft sitting on their wheels had the gun firing mechanism disabled: as soon as the aircraft lifted off its wheels on take-off, the disabling switch closed allowing the guns to fire. In order that the guns could be tested on the ground, the override switch was fitted to the starboard wheelbay.
- Having set the switch to Fire up into the cockpit and sit in the pilot’s seat. Switch on the gunsight and test all functions, including the dimmer switch. Clean the lens and reflector glass. Very important. No armourer wanted his pilot to go chasing a speck of dirt on the reflector glass halfway to the Pas de Calais. Switch off the gunsight.
- Turn the safety ring on the pilot’s firing button from Safe to Fire and press the button while listening for the breech blocks to clang forward. Set the safety ring back to Safe,
- Remove the filament from the gunsight. It will have cooled down by now. Replace it with the spare filament from the filament holder next to the gunsight and fit the original filament in the holder. Test the gunsight again.
- Down to the ground again. Set the Safe/Fire switch back to Safe.
- Check that all the breechblocks are forward and using a special feeler gauge check that all the firing pins have all released.
- Re-load the guns and replace all the access panels.
Next was to go off to the flight office to sign the Form 700 (the aircraft’s log book). By now the Squadron state will be up on the board as well as the allocated pilot. The states would be either “Readiness from a stated time” or “30 minutes standby” or “one-hour standby”.
Then back to the aircraft to await whoever was to run the engine up. We had about four people on the flight with the authority to run engines. So, with the trolley acc plugged in and switched on, and positioned as far out along the starboard wing as the cable would allow and the wheel chocks kicked in hard in front of the wheels, we waited for the engine man.
With Dave Foster in the cockpit to give the ‘all clear’ and ‘ready’ signal he would start the Merlin engine and set the throttle to ‘fast idle’ until the engine had warmed up to operating temperature. He would then test the magnetos by switching off each mag in turn and noting the rev drop. There was a specified value for each mag test. Open the throttle to high revs, test the mags again. Then, with a signal to myself and Joe Lister to go and lie across the tailplane, he opened up the engine further, tested the mags again and finally took the revs up to take-off power for the final test. Everything being okay he would shut down the engine. We are ready to go.
Joe Lister would then go to the Ops Room and, having confirmed the allocated pilot, would seek out the pilot and go with him into the locker room to collect his parachute and helmet.
He would then bring these out to the aircraft and fit the parachute into the pilot’s seat. He would then carefully lay out the straps. Sutton Harness first and then the parachute straps. The Sutton Harness holds the pilot in his seat. Helmet on the control column; never on the gunsight as is often in photographs. If hung on the gunsight it could, as the pilot snatched it off, displace the gunsight alignment.
Check that the trolley acc is correct, chocks tight and we are ready. Nothing to do now but sit against the pen wall and wait.
As soon as we hear the scramble bell we take up our positions. Joe will follow the pilot up the wing to help him strap in and close the fuselage door. Dave will stand in front of the wing and give the ‘start-up’ signals. I go to my place on the trolley acc.
As soon as the pilot is strapped in and has his helmet on, he will signal to Dave that he is ready to start up. Dave will give him the ‘all clear’ to start. As soon as the Merlin engine is running smoothly, the pilot will set his power switch from ‘external’ to ‘internal’ and give me the thumbs up to clear the trolley acc. I will switch off the trolley and go in along the leading edge of the starboard wing, unplug the cable and close and secure the panel cover.
As soon as the pilot is ready to taxi away he will wave to us to pull the chocks away and, on a signal, from Dave he will taxi out. We always stood to watch our aircraft take off.
Once the aircraft were away we would coil up the trolley acc cable on top and park it against the pen wall well out of the way. We would then go into the air raid shelter and bring out eight boxes of ammunition ready for the re-arm and stack them against the wall next to the trolley acc. I would always check that the lids were on tight: a flying ammo box lid could be a dangerous missile.
When the aircraft returned we would always watch them carefully as they broke formation and turned onto the downwind leg [at 1000 feet above the aerodrome in preparation to land]. Looking, of course, for “SH/E” to make sure it had returned. We were a lucky crew. Throughout the Battle our aircraft only failed to return on three occasions. Twice when flown by a sergeant pilot and once when flown by our regular pilot, Flying Officer O’Meara2. On each occasion, the aircraft landed away and later returned safely. It did, on occasion, suffer significant damage but was always repaired on the Squadron.
Watching the aircraft on the downwind leg, groundcrew with experience could detect the different noises the aircraft made. After re-arming a Spitfire or Hurricane, the armourers always secured a linen patch over the gun ports using red ‘dope’. If the guns had been fired these patches would have been blown away and the aircraft would have a very distinct whistle caused by the air passing through the gun ports and out of the ejection openings. If the guns had not been fired, and the Squadron did not always find a target when scrambled, the distinctive whistle would not be heard. The patches were to help keep the guns clean and help prevent freezing [at high altitudes] before they were fired.
As the aircraft taxied in, the six of us in the pen would take the first aircraft right into the pen and, with three of us hanging on one wingtip, turn it precisely into its place. The second aircraft we would turn in front of the pen and then push it back into its place.
Next task was to push the petrol bowser into place in front of one of the aircraft. Our bowsers were all trailer bowsers brought to dispersal by a tractor. They had small donkey engines in the back to pump the fuel, but no engines to move them.
If the pilot had fired all the ammunition I could re-arm the aircraft inside twenty minutes. If there were stoppages, or if I had to strip out unused ammunition it would probably take about half an hour. Part way through I would have to stop to help push the bowser across to the other aircraft.
This activity would continue throughout the day with the readiness status changing with time. Dinner (lunch) would be served on dispersal from ‘hayboxes’. The NAAFI 3 van would appear morning and afternoon to provide ‘tea and wads’4. Eventually we would be stood down. Sometimes it would be as late as 9.00pm before we stood down. That made a 15-hour day.
- “Wartime Reminiscences of an RAF Armourer by 633697 Chief Technician Pountain BEM” – held at the Imperial War Museum (IWM Docs 14379). Ronald Pountain joined the RAF in 1938. He went on to serve with RAF fighter squadrons in the Middle East (El Alamein), Sicily and Italy (Monte Cassino) and remained in the RAF after the war.
- Flying Officer O’Meara retired as a Squadron leader in 1959. During the Battle he probably destroyed a Ju88 on 21 May and an Me109 over Dunkirk on the 31st. He claimed an Me109 destroyed on 19 July, two Ju87’s and probably another on the 29th, two probable Me109’s on 11 August, an Me109 destroyed on the 12th, an Me109 and a Ju88 destroyed on the 13th, two He111’s damaged on the 15th, an Me110 damaged on the 16th and a Ju88 and a He111 shared on the 18th. See: [http://www.bbm.org.uk/airmen/OMeara.htm ]
- NAAFI – “Navy, Army, and Air Force Institutes”: an organization set up in 1921 to provide canteens, shops, etc, for British military personnel at home or overseas.
- “Tea and wads” – ‘Wad’ was popularised in the military from around the time of the First World War and was slang for a cup of tea and slice of cake or a sandwich.