202 Squadron Association


Meteorological Reconnaissance

A Brief Introduction

I have learned to my horror at our social functions that many (most?) of our members are very vague about 202's raison d'etre pre Search and Rescue. While I know little about the early Coastal Command work, I can help on Meteorological Reconnaissance. This note gathers together, from many sources, including The Met Office Library, John Malcolm and personal memory, the story of Meteorological reconnaissance in the Royal Air Force from the early days of World War 2 till the mid sixties particularly as practised on our Squadron. It does not pretend to be a precise history; it is only information and entertainment for our younger members. Perhaps someone will have to do the same some day for Search and Rescue!

Meteorological Reconnaissance Pre 202 Squadron

Even now with the advent of remote sensing systems like artificial satellites, the main method of finding out about the weather over the oceans is still to persuade merchant ships on passage to observe and report the weather every six hours. Sixty-odd years ago there was nothing else

With the outbreak of the Second World War, ships in the North Atlantic could no longer report their positions and weather and the Atlantic became what is known in the jargon as a "data sparse area". As an aside, the rate of attrition of merchant ships in wartime is demonstrated by the size of the British Voluntary Observing Fleet: the 995 British ships reporting weather in 1939 had been reduced to 480 when peacetime reporting restarted in 1945. The target number in 1945 for a reasonable network of ocean observations was 1000 British ships.

Knowledge of the weather, particularly predicted weather, is essential to the prosecution of modern (1900s onwards) warfare and those countries who had weather data during the war classified them SECRET. Other sources of information had to be found. One method used was long range aerial reconnaissance and, in Britain, the bulk of the task fell to Coastal Command.The use of aircraft for sounding the atmosphere over a spot from ground level to their ceiling began in the 1914-1918 war, mainly as an aid to artillery work, and had been routine since 1925; these provided early examples of the acronym - "THUM" from "Thermal Upper-Air Measurement" and "PRATA" from "Pressure and Temperature Sounding". (Nowadays we would have used the letter "S"). One such sounding was made at Worcester using Spitfires for many years until well after the war.

Long range reconnaissance, the kind done later by 202, began in Spring 1941 with three Met Flights, 1403, 1404 and 1405 , being established at Bircham Newton, St Eval and Aldergrove respectively to fly Blenheims. Soon afterwards 1407 Met Flight was formed to operate out of Reykjavik.1406 Met Flight was formed at Wick and absorbed 1408 Met Flight. These, however, were PRATA flights using Spitfire 2s. Flights were also formed to operate out of Tiree and Gibraltar. The image on the right "Tracks"shows the network of long range meteorological reconnaissance flights available in the latter part of the war, by which time some thirty flights a day were being made. There were also flights operated by the United States Army Air Force (and possibly Navy?) from Burtonwood, Newfoundland, Bermuda and the Azores. The principal Squadron involved was the 652nd Bomber Squadron of the 25th Special Reconnaissance Group operating Flying Fortresses. 269 Squadron RAF also operated out of Lagens from 1944.Initially these Flights were equipped with Blenheims, but soon progressed through Hampdens to Hudsons allowing them to progress towards truly long range work.

In 1943 Halifax and Ventura aircraft were approved for long and medium range reconnaissance and new squadrons, 517, 518, 519, 520 and 521, were formed or or moved into the reconnaissance field subsuming the earlier Flights. Brawdy, Tiree and Langham were added to the stations operating Met Flights.You will believe that the above is actually a drastic simplification of the formations, amalgamations and moves that took place then and the re-equipping was nothing like as simple as I suggest with each Command and Squadron claiming higher priority for available aircraft.

Two operational successes other than weather watching were recorded about this time: In April 1941 Flt Lt Douglas Bisgood was nearing the end of a RHOMBUS sortie when he came across three Junkers 88 returning to Germany from a raid over England. Bisgood, a former fighter pilot, gave chase and one of them was shot down with the Blenheim's forward firing gun. He was awarded the DFC (or probably a Bar).

On 12 August 1942 the EPICURE (fig 1) flight from St Eval (Flt Lt Dennis Wykeham-Martin) spotted a u-boat on the surface and attacked. The boat crash dived, but was blown out of the water by two anti submarine bombs and sunk. The crew were commended by AOC 19 Group.

An indication of the spirit on those early Met Flights (and an inkling of what it must have been like to be Flight Commander) comes from the No 1403 Flight Line Book: "If the cloud base is more than 10 feet, a Blenheim can land because it is only 9 feet high". Initially the weather observing on RAF flights was done by the Navigator - a class of men that I have long regarded as the brains of the RAF. The decision to create a Meteorological Observer Section of the General Duties Branch of the RAF(VR) was promulgated late in 1942 and sufficient volunteers rapidly came from the mostly civilian Meteorological Office. Training began early in 1943. By the end of the war 20 RAF officers and 80 NCOs had been trained in addition to a number for the USAF. In addition to weather observing, training included navigation and air gunnery; in fact the first observers wore the AG Brevet. They didn't hang about in those days: from basic training to operational was not much over two months!
Sorties varied from day to day to suit operational requirements, but a typical triangular flight would be two low level legs with one high level one. The first, outward leg, would be about 700 nautical miles in length and would be flown at a pressure height of 950 millibars. This was achieved by the Met Observer using his barometer to talk the pilot onto that height and then the remainder of the leg was flown on the altimeter with no alterations to the sub-scale. If the mean sea level pressure made 950 MB an unwise
height, 930 or even 920 could be used. Weather observations were made every 50 NM with a descent to 50 feet asl at every fourth position to measure the sea level pressure. On these "sea level" runs the height was estimated by the pilot. Enough said, though radio altimeters did come along later!

In addition to the barometer, the Met Observer had two main instruments: the psychrometer and the air speed indicator. This latter was essential to apply corrections for the effect of air friction to the temperature readings. The psychrometer was an aviation version of the familiar dry and wet bulb set and was mounted on a strut outside a window close to the observer with water being supplied to the wet bulb by pumping from a tank inside the aircraft.

Another example of the spirit (or something) prevailing in those days happened at Gibraltar when the Halifaxes were being modified and were not available for Met use and the Met Air Observers (as they were then called) flew with 202 Squadron on Catalinas. There was no provision to mount the external psychrometer strut and the temperatures were obtained by the MAO strapping the psychrometer to his arm and leaning out of a hatch for some minutes until the thermometers settled down and could be read accurately. At the end of the low level leg a climb was made from 50 feet to 500 MB with temperature measurements being made every 50 MB. More details of this procedure will appear in part 2 of this article.The return, low level leg was a near mirror image of the outward one.
By 1945 some 30 long range meteorological reconnaissance flights a day were being made the by the RAF in the Eastern Atlantic in addition to those being made by the American air forces. There were now some 100 Meteorological Air Observers at work. But, up to this point, 202 Squadron had played rather a small part

When peace broke out there was immediately a reduction in the requirement for meteorological reconnaissance flying: the need for accurate weather forecasts was less acute and civilian ships were once again able to report positions and weather in real time.

The Atlantic, however, remained the source of most of Britain's weather and the weather forecasting techniques of that era required the analysis by hand of charts plotted by hand with as much detailed weather data as possible. Professionally made weather observations from an area chosen by the forecasters were invaluable and the answer was still Meteorological Reconnaissance.

At the time 202 Squadron was performing anti-submarine duties at Castle Archdale. In 1946 they were disbanded for a short time before designated as a meteorological reconnaissance squadron up the road at Aldergrove with Halifaxes'.The Halifax lasted until 1950 when the Squadron re-equipped with the Hastings C Met Mk 1.The establishment was five aircraft on the Squadron and three in the hanger or at the MU.

The crew for a reconnaissance flight was 2 Pilots (one being Captain), Navigator, Engineer, 2 Signalers and 2 Air Meteorological Observers as they were now known. The "on duty" AMO occupied the right hand pilot seat.

AMOs were selected from experienced airfield observers of the Met Office and had perhaps unique conditions of service: they were signed on for two and a half years with an extension for a further two. This was a cunning Air Ministry ploy to ensure that no one qualified for any terminal grants or similar. It was not too unfair, however, as return to a job in the Met Office was guaranteed.

During the period of flying the Halifax the Squadron lost 32 aircrew in accidents; an enormous number for what may have seemed to many to be a cushy peacetime job. No further lives were lost in the following fifteen years of Hastings operation though one was written off and two were very seriously damaged in crashes.

The myriad of reconnaissance tracks being flown by several squadrons round the UK was rationalized into three: EPICURE from St Eval, NOCTURNAL from Gibraltar and BISMUTH from Aldergrove. By 1950, 202 Squadron flying BISMUTH from Aldergrove was the only one left. The Code name "BISMUTH",was formerly one single triangular track flown from Tiree by 518 Squadron, was adopted for the whole system with fifteen individual tracks being lettered from A to O. Normally only one track, chosen by the Meteorological Office's Chief Forecaster, was flown in daylight each day, but occasionally during exercises and alerts two or more, including a night one, were flown. Tracks fell into two main types: triangles and probes.

Triangles (A to G) were similar to the wartime ones but with the distance between observation positions increased from 50 to 60NM. The introduction of a radar altimeter (SCR 718) meant that the low level legs could now be flown at a fixed height of 1500 feet above sea level allowing the measurement of surface pressure at every observation point instead of only at the "sea level" ones as previously.

As an observation position was approached, the AMO, in the right hand front seat, would set his pressure altimeter accurately to 1500 feet and the pilot would copy this to his and fly at a precise height and steady airspeed until all measurements had been made. Steady airspeed was very important because, with dynamic heating and other factors varying with at least the square of the airspeed, small fluctuations in IAS meant a few minutes for the thermometers to settle down.

High level legs were still flown at the standard pressure level of 500 MB, just above FL180, but the advent of the SCR 718 meant that this height above sea level could be measured - a very valuable meteorological parameter. In fact the height was calculated from the temperature profile at the climb and descent positions and the radar altimeter was used to measure changes from that.

Remember that this was the infancy of civil trans-Atlantic flying creating a great need for upper air data and there were only nine ocean weather ships to provide it in the whole Atlantic. The high level observations from BISMUTH and its American cousins FALCON and GULL were invaluable.

The procedure for the soundings had been developed over years of experience and required a high standard of flying and crew co-operation. At the climb position the AMO made the routine 1500 feet observation and then the aircraft was taken down to 200 feet with heights being called out by the AMO from the radar altimeter until it went off scale around 700 feet when the second pilot standing between the pilot and the AMO took over giving heights from the radio altimeter, which was much more precise at low levels. Not wishing to hang about too long at that height, the AMO rapidly read his instruments and the climb began. This part of the trip was more comfortable than the estimated 50 feet of earlier years, but it was still not easy for the pilots to hold a precise height this close to the wintry North Atlantic Sea; I recall one occasion, with a very senior, but out of practice pilot, when the trailing aerial vanished. Sea King pilots may snort at this point if they wish.

On the climb from 200 feet to 500 MB stops were made every 50 MB to measure temperatures. As already mentioned, precise, constant airspeed is very important for accurate temperature measurement and any fluctuation in the IAS necessitated a wait while instruments settled down. Fuel considerations and the crew's temper required that such delays were kept to a minimum. Close co-operation between Pilot, Engineer and AMO did the trick. As the required pressure level was approached, the AMO would call out, "200, 100, 50 feet, on height". The pilot would ease the aircraft from climb or descent to level flight while the engineer gradually adjusted the power. With a practised team the transition could be achieved with no change in the IAS allowing the AMOs to do their work rapidly and the sounding to be resumed without delay. This [unusual] teamwork with pilots co-operating with the rest of the crew, is probably similar to that found in 202's present work.

The dry and wet bulb psychrometer is not really suitable for measuring humidity at temperatures well below freezing - though it can be done with patience. For high altitude humidity the dew or frost point was measured using a Dobson-Brewer Frost Point Hygrometer, in which a sample of the outside air was cooled using a "slush" of alcohol and solid carbon dioxide until the Observer, looking through a lens, actually saw the dew or frost forming. In theory this operation was supposed to take about 20 minutes (the Meteorological Research Flight took rather longer), but, that being impractical for fuel reasons, the Bismuth Observers were rather proud of rarely taking more that three or four minutes even down to minus 40 degrees Celsius or lower. This instrument was usually mounted in the galley and operated by the second AMO nowadays we would say that the Met Observer/Cook was "multi skilled".

Probe tracks, H to N, were flown when a weather system beyond the reach of the triangles had to be investigated. They were designed to fit the prudent range of the Halifax. In this case the outward, low level leg was rather longer than a triangle one, but, on completion of the climb, a cruise descent to FL90 was made and the flights returned along its outward track at that height. 9000 feet is as close to the standard pressure level of 700 MB (9882 FT) as one is allowed to fly without oxygen.

A third type of track was BISMUTH O in the North Sea. This quite complicated, if short, track was flown at lower levels with a number of sounding ascents; it was used on occasions of Easterly airflows across the North Sea threatening the East Coast fighter bases with haar, fret or just clag.Flights were timed so that the climbs and descents were close to the international radio-sonde time of 1200 GMT and this was usually achieved with an 0800 take-off. So keen on this were some Captains that it became the practice to have the BBC Light Programme on the radio compass (well, what else would you use it for?) and for the wheels to leave the ground precisely on the sixth pip of the Greenwich time signal. As I recall, those same Captains expected a cup of coffee to be placed in their right hand within an infinitesimally short time of safety speed being called.

By the time that 202 Squadron was disbanded again in 1964, in addition to their other duties they had made over 4000 BISMUTH sorties entailing 40,000 hours of flying. On an individual basis, it was considered to be a great achievement if a Squadron member made 400 BISMUTH flights. This was certainly achieved by Master Pilot Radina and Master Signaler Stratton and would have been done by Flt Lt Ignatowski had the Squadron just lasted a few weeks longer. There are probably others (Flt Lt Dinnes?) and I apologize for not mentioning them. It is unlikely that modern management would approve the practice of marking the 400th BISMUTH by greeting the returning aircraft on the pan with a barrel of beer.

The photograph shows The Air Met Observer Section at the time of disbandment. At least three of those pictured are members of the association.

All photographs Courtesy of
John Malcolm / Hugh Cumming