The Vulcan was a machine of the 1950’s, and the navigation equipment shows that. For all that, it could be used to give very accurate results.

Photo of Nav Radar station Equipment at Nav Radar station Radio Altimeter display

[There will probably be more on the GPI6 in later updates.]

The Navigation System was an integration of the equipment used for route navigation, and that used for weapon aiming and delivery.  As will become obvious in the description of the NBS equipment, this was all designed a long time before PCs, it was very mechanical, a truly analogue computational machine rather than a digital computer.  For all its crudity (or sophistication as it may have seemed to a WW2 navigator) you could navigate accurately and you could put a weapon relatively close to the aiming point. As the weapon was intended to be nuclear, a few yards off was not expected to matter too much, and 'collateral' damage was not the consideration that it is to today’s targeting teams.

The photo below (source unknown) was probably taken in one of the aircraft used in static displays after the Vulcan was withdrawn from service.   I may be wrong. The equipment looks pretty complete, and in good repair.  On this and the accompanying pages I will give some outline of some of the major units, and their function.  The photo is taken from between the seats of the nav Radar (on the left of the photo) and the nav Plotter (on the right of the photo). The backs of both of their seats just intrude into the photo.  On the right of the Plotter, but not in the photo, is the AEO station. The view in the photo is towards the rear of the aircraft, as the rear crew sit facing backwards, so the small ‘porthole’ on the left of the photo is in fact on the right (starboard) side of the aircraft.  There is a similar vision panel by the AEO, as you can see these are quite small, and they also have a small blind that is wound up.  When the nav Radar is working on a fix or a bomb run he will drop the blind to keep the light off the radar screen. You can see that the desk area in front of each navigator is quite restricted and leaves little room for maps, equipment, almanacs etc. One thing you learn quickly is to be organized.  The equipment will be discussed elsewhere, but a couple of points to note.

Hanging from the ceiling, with a white ‘bobble’ on the end is a ‘grab handle; this is to make it easier for the navigator to haul himself out of his seat, especially if he is moving around with his parachute and survival pack strapped to his bum.

There are two black ‘wander lights’ on flexible mounts.  When night flying cabin lighting is kept to a minimum to help preserve pilot ‘night vision’, so these wander lights allow the two navigators to focus light on their maps etc. without upsetting the pilots.  The AEO has a similar facility. The Green Satin is immediately to the left of the black shade on the right hand wander light.

‘The Office’ for the Nav Radar and Nav Plotter.  I don’t know the source of the photo.

So, when the navigators sit at their stations, what do they have around and in front of them?  The first comment is that as you look at the photo you will see that, as with the pilots, the instrumentation is from another age; it looks old, it uses mechanical dials and pointers and much of the equipment has substantial cables and military specification connectors.  In front of the Plotter are the main tools of his trade, an altimeter for height, Green Satin giving him groundspeed and drift and the GPI6 with his position in Latitude and Longitude, and with the facility for this to be updated manually or from the NBS kit.  The Plotter also has an RDF repeater giving relative bearing from a selected radio beacon, he also has a TACAN readout giving range and bearing from a selected TACAN beacon.  These facilities allow the Plotter to maintain a log of aircraft position and control the en-route navigation of the aircraft.

I’ll spend a little more time on the equipment at the nav Radar station, as that was my workplace.

The station was on the Plotter’s left, on the starboard side of the aircraft, facing backwards, this configuration could get a bit of getting used to at low level; for one thing it was a little easier to start feeling airsick, and you had to remember to give the right changes of direction to the pilots, remembering you were facing the wrong way. Behind the seat was the large drum containing the ‘Calc 3’ for the NBS, this unit accepted the film cartridge to feed weapon ballistics to the bombing computer, it also contained the ‘height chain’ analogue units for feeding height calculations into the weapon forward throw, so computing release point. Target height and other height inputs were set on this unit by the Radar. 

Sitting at the desk you can see in the photo a small round window, there is also one above the AEO, when using the radar on a bombing run I would normally have the blind drawn across this window to keep light off the screen.  On the side panel by the Radar’s left arm, just above the desk are two control panels, one for the bombs and one for the different radio frequencies and crew intercom that the Radar would want to ‘listen in’ on.  Normally you would always have the crew intercom and probably one outside frequency, depending on the activity at that point in the trip; various frequencies might be the Radar Bomb Plot, ATC control of the low flying area, ATC for the route navigation, Local or Approach controlers when returning to base for time in the circuit. Above both of these is the panel controling the elecrical power to the nav kit and this was normally operated under the checklist control of the AEO. The power required for the radar etc would only be available when the AEO had main busbar power from all 4 alternators, so nav power would be selected during start-up checks when cleared by the AEO.  Similarly, if there was an electrical emergency, or when exercising the Ram Air Turbine, non-essential equipment would be switched off, again under the control of the AEO.

Directly in front of the Radar is the H2S display screen and mounted above that is the R88 camera for taking photos of the radar display at points in the trip. To the left of the screen are controls for the antena, allowing it to be tilted, for rotation to be varied, for the range to be selected, basically this unit allows you to control the picture. To the right of the screen are the controls for the Internal Offsets, used during bombing. On the desk in front of the screen is the small control stick, the 626 which will control the display and markers on the screen, this is described elsewhere, but basically it allows the operator to ‘drag’ the PPI display or the markers around the screen, depending on how the operator has set up his system.  On the left of the 626 is a small switch, the ‘wind switch’ which the operator can use at the same time as he is using the 626.  Above the screen, but to the right, is the Main Panel with the large heading repeater and a large dial readout of groundspeed.

You can see on the photo that above but to the left of the screen is the small round screen of the radar altimeter, a fairly ancient piece of kit which sticks out quite a lot because of the old cathode ray tube display.  The screen has a circular scale which (If I remember correctly) can be switched to give a scale for low level and one for high level.  Although old technology now, it was pretty accurate.  The display had a circular trace with a ‘spike’ showing the aircraft height.  The value was that as this was a radar altimeter rather than a pressure instrument, it gave a height above ground level (AGL), this was particularly important at low level.  As a simplistic example, if you were briefed to fly low level at 300ft and the ground height in the area of the target is 300ft, then you would want 300ft on the radar altimeter, but 600ft (depending on local pressure setting, QNH) on the pilot’s pressure altimeter. It was part of the nav Radar’s flight safety role to monitor this instrument at low level and give periodic warnings to the pilots if he felt that the height was creeping down.

In the diagram below the altimeter has been set for the 0-5000ft range, and is indicating a height of 3,500ft.

Diagram from OCU notes.  J Dillon

The photo below is one of Damien Burke’s and may have come from the Thunder and Lightning web site.

The photo shows a little more of the nav panel than the previous shot, but appears to have come from an airframe in a bad state of repair, it also has perspex covering some instruments and controls so I suspect it is a static display from somewhere and the public are probably allowed to go inside.  This photo shows more of the GPI6 than the previous photo.

The GPI6 (Ground Position Indicator) was the unit into which other navigation aids were fed to produce the aircraft ground position in Latitude and Longitude.  The inside of this large box was a truly wonderful mix of finely machined metal cogs, cams, electrical relays switches and dials.  Again, a testament to analogue computation as opposed to digital.

Before the start of a sortie the Plotter would set the GPI to the known, surveyed coordinates of the 'pan' or hard-standing that the aircraft was on and the main compass system, HRS (Heading Reference System) was checked against the known orientation of the specific 'pan'. From this point on, if all equipment functioned correctly, if none of it went into standby mode, then the GPI would receive feeds relating to heading, groundspeed and drift and would give an accurate readout of the aircraft ground position.  However, due to inherent small errors in any integrated system as mechanical as this, there would be small errors, and these would be corrected by periodic 'fixes' during the trip; these fixes could be from the radar, from Tacan or other radio aid, or at night, from astro star fixes.

This is a good shot taken from one of Ken Townsend’s photos. It is from XL360 at Midlands Air Museum, Coventry.  It shows the Plotter’s favourite toy, the GPI6  In the centre are the DR readouts showing N/S & E/W positional readout according to the nav kit, or DR if the Plotter is working in ‘limited’ mode.  On the left are the FIX readouts.  The GPI6 can have its positional information updated by radar fixes.  The lat/long of the fix point is set up on the FIX counters and then during the fix operation the radar markers are driven by the GPI. The DR counters will have run out to the same value as the fix counters during this operation. If there is no system error then the radar markers, driven by the GPI, will have fallen over the fix point.  There was invariably some error. This error is corrected by the Nav Radar using the 626 control to reposition the markers correctly over the fix position. In doing this, the error correction involved will also have been fed to the DR counters. When the fix operation is complete the counters unwind back to the aircraft position rather than the fix point position. During the fix operation the aircraft movement will have been stored on cams in the GPI6, these will update DR counters with the aircraft movement so that they should now read the corrected true aircraft position.  It was easier to do than describe!