World War Two
1939 - 1944 RAF Ronaldsway
A limited civil air
service was continued during WW2 using Dragon Rapides to Liverpool and
Belfast. Ronaldsway was taken over by the RAF in 1940 but apart from a
remote direction finding station to the north east, I'm not sure if any
military air traffic control facilities were provided at the airfield,
possibly just the ubiquitous Runway Control Caravan.
As far as I can tell,
Civil or possibly a joint ATC continued operating from its pre-war location
until the airfield was extensively re-built for the Royal Navy in 1943,
construction of tarmac runway 13/31 necessitating demolition of the original
terminal building and ATC Watch office.
    
RNAS HMS Urley -
The Royal Navy take over Ronaldsway
In 1944 the Royal Navy
took over a completely rebuilt airfield with four asphalt runways, numerous
buildings and hangers and a brick built control tower used for military
movements only, control of the civil air link being transferred to the
'barn site' on the former Ronaldsway Farm on the 1st April. This occasionally
lead to some disputes between civil and military controllers as to the
runway in use. It probably took considerable effort for the RN to change
runways with the Runway Control Caravan (and Radar talkdown vehicles) having
to be moved from one site to another, however the Dragon Rapides really
needed to land into wind, there are at least two recorded instances of
them leaving the edge of the runway due to crosswinds. They were probably
much happier with the smaller grass airfield!
    
Civil control was still
by 'procedural' means with the help of D/F, but the Navy had an early Surveillance
and Precision Approach radar which operated from a moveable vehicle which
would be located close to the upwind end of the runway in use, loop roads
and electrical power points being provided for this. Also mentioned as
being installed at Ronaldsway is BABS (or possibly Lucero), an airbourne
radar derived approach aid. Control over both civil and military aircraft
landing and taking off on the runways would have been by Aldis Lamp or
Very pistol flare from the Runway Van located on concrete loops constructed
close to the threshold of the runway in use. Royal Navy aircraft practising
aircraft carrier landings would be 'batted down' by the Landing Signals
Officer standing on the side of the runway, dummy arrester wires were painted
on the runways. Interestingly, most of the operational airfield would have
been invisible from the civil control window at the Barn Site.
    
    
   
(Above picture
set is © Fleet Air Arm Museum, Yeovilton)
Ground Controlled
Approach (GCA)
Developed during the
1940s by the Massachusetts Institute of Technology, GCA allowed a ground
controller to offer a 'talkdown' service using Precision Approach radar
to aircraft in poor weather conditions. No specialist equipment was required
on the aircraft, just a two way radio for communications. The radar consisted
of two elements, a 'search' or surveillance radar that scanned through
360 degrees (much like our current radar at Ronaldsway) and the talkdown
element which scanned the final approach track with separate horizontal
and vertical radar beams. The 'search' controller would radar identify
inbound aircraft and marshall them onto a closing heading for the final
approach track until they came within the beam of the 'Precision Approach
Radar' (PAR) and the aircraft would be transferred to a separate frequency
for the talkdown. The controller would give the pilot heading corrections
to remain on the final approach track and at a predetermined point instruct
the pilot to commence descent. The controller would monitor the descent
profile and instruct the pilot to alter descent rate if the aircraft started
to drift either high or low and continue giving heading corrections to
keep the aircraft on the centreline. The talkdown would commence at about
5 miles from touchdown and be continued to 1/2 a mile from the touchdown
point althoough the equipment was capable of displaying the aircraft right
down to the touchdown point. Early PAR systems used 'trackers' manning
the radar tubes who keep electronic markers centred on the aircraft return
which would drive two meters in front of the controller showing lateral
and vertical displacement. In later systems the trackers were dispensed
with and the controller sat in front of a cathode ray tube displaying both
the lateral and vertical radar traces.
'Flight' photographs
of an early post war GCA system
  
The whole set-up was
mobile, consisting of a caravan for the operators, another housing the
actual radar and radio transmiters/receivers/aerials and a truck
to tow them around, often housing a generator to power the installation.
It would be towed to the appropriate hardstanding for the runway in use,
powered up and then aligned using radar reflectors. Changing runways would
obviously take a little time. There are still traces on the airfield today
of where the PAR and runway vans were located.
 
PAR radar is no longer
used in civil air traffic control, but still extensively at military airfields,
RAF Valley on Anglesey being the nearest to the Isle of Man. The radar
information is now also remoted into the Approach room, so no more draughty
caravans out on the airfield!
  
Eureka, Rebecca &
Babs
Three elements of a
radar homing and approach aid operating on frequencies around 200Mhz. Eureka
was the ground based radar responder beacon. Rebecca was the aircraft fitted
element of the system and would interrogate the Eureka beacon to obtain
a range and bearing from the airfield to enable the aircraft to home in.
Babs was the approach element and when interrogated by Rebecca would provide
an indication of final approach track and distance from the airfield. This
was presented to the aircraft navigator on the airborne radar CRT screens
and the navigator would talk the pilot down until he became visual with
the runway. The Ronaldsway based RN Barracuda aiircraft would most likely
have been fitted with Rebecca Mk11B.
Link
to external page with details of Eureka/Rebecca/Babs
Post War Operations
After WW2 the airfield
and all facilities was bought by the Isle of Man Government and civil air
traffic control moved into the former Royal Navy tower building, where
it continued into 2010. In the late 1940s Air Traffic Control was being
carried out by 'procedural control' using a mixture of M/F, H/F and VHF
radio frequencies, the PAR radar and radar beacons would have been taken
by the Royal Navy when they vacated the airfield. Air Traffic Control procedures
seem to have continued much as they were before the war, with very little
regulation of en-route traffic. There was a 'North West Flight Safety Region'
covering the area, administered by Speke ATC at Liverpool using M/F frequencies
339-341 KHz. Direction finding stations at Speke, Ronaldsway, Carlisle
and Manchester Ringway could provide bearings to plot aircraft positions.
Presumably 'traffic information' would be provided on other aircraft, but
it was up to pilots to arrange their own separation, either visually or
by flying at different heights. Ronaldsway ATC would provide control services
with its 10nm Controlled Zone in 'QBI', i.e. poor weather conditions.
  
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