Technical Notes

I have written the following technical notes on some of the Javelinís systems, after having read one of the Javelinís technical manuals belonging to the Midland Air Museum.

I'd like to thank the many ex-Javelin techs, specialists in airframes, engines and radar; who've been in touch with me about this page! I now stand corrected on a few items and it's been very interesting to hear from you.

Iíve seen quite a few books and articles written about the Javelin and it is unusual to see this level of detail in any text book, so much of this information wonít be available elsewhere. Also Iíll be adding to it in the future as I work on the aircraft and learn more about it. Be warned, as information goes Iím treading the fine line between Ďinterestingí and Ďuselessí! I hope you enjoy reading it anyway.

 

The Front Cockpit

To begin with, let's take a look around the front cockpit and start to become familiar with the Pilot's controls.

These pictures appear in the Pilot's Notes for the Javelin, showing the port console, the main instrument panel and the starboard console.  I can't identify exactly which mark of Javelin they apply to, except to say it's not a mark 5.  Their date stamp of 14 Feb 64 would almost certainly put it as a later one, so it's quite likely a mark 9.

With thanks to Ham.

(Images © Crown Copyright)

A few items on the Port console are the throttles (port 13, starboard 17), airbrake controls (14), hood open/close switch (19), undercarriage selector (20), hood jettison (24) and emergency tailplane trimmer (29).

The main panel includes the standard RAF blind flying panel.  There is a machmeter at the top right plus Instrument Landing System (80), AYF indicator immediately above (not numbered), Zero reader indicator (54) and course selector (81).  Note also the fuel gauges (79) on an angled panel at the bottom.  Along the top is a g-meter (50), clock (57), cabin pressure altitude (63) and engine fire warning lights (58, 64). On the panel to the right are the engine instruments: RPM (69), Oil pressure (70), exhaust gas temperature (71); also the parking brake (72).  The rudder pedals have toe brakes and negative-g straps.  The square shaped thumb control on top of the stick is the tailplane trimmer control.  The gun firing trigger (not visible on the far side of the stick) is operated by the right index finger and can be locked by a safety latch just above it  
On the starboard console are the oxygen regulator (85) and contents (83), battery isolation switch (115), emergency oxygen control (108), electrical master switches (105), engine starter buttons (97).

 

Power Supplies

Electrical power for the aircraft is produced in a similar way to a car, which has an alternator wired through a voltage regulator and connected across a battery.

Both of the Javelinís engines are coupled to an accessories gearbox so either or both engines are capable of driving its two DC (direct current) generators.

With the requirements of aircraft systems being so much more complex than those of a motor car, AC (alternating current) at a higher voltage must also be provided to power some of the flight instruments and radar systems. This is achieved by a device called an inverter, which is an AC generator powered by current from the aircraftís DC generators. Inverters make the characteristic high pitched humming noise heard in jet aircraft cockpits.

The Javelin is equipped with:

DC: Two Type 507, 6 kilowatt DC generators, wired in parallel.
Output was 28 volts, with a maximum output of 200Amps at 30 volts. 
One Type J, 25 amp. hour 24 volt battery wired across the two generators. 
One emergency alkaline battery, 24 volts, 0.4 amp. hours. 
AC: One Type 103A main inverter producing 115 volts, three phase AC at 400Hz. 
One Type 100A inverter (standby). 
One Type 201B inverter producing 115 volts, single phase AC at 1600Hz. 
Two Type 200 inverters producing 115 volts, single phase AC at 1600Hz. 

Engine Starting

In common with many other jet aircraft at the time, the engines on the early marks of Javelin (Mks 1 through 5) were started by a cartridge. The cartridge was in fact a five inch diameter shell containing an explosive charge made of cordite. Two cartridges would be loaded for each engine, one being a reserve, and they were fired electrically by an automated start-up sequence which was controlled by a motor-operated time switch.

First the pilot would set the battery isolating switch ON which would prevent damage to the dc supply as the generators were started up with no load. He would then switch on the fuel pump circuit breaker, the starter master switch, the ignition isolating switch and no.1 generator reverse-current circuit breaker. Next he would hold down the first engine start button for about a second.

What followed was controlled automatically by the time switch. A special circuit was energised which would hold down the starter button for the next 30 seconds, to disable it from being pressed again too soon. Meanwhile an electrical supply was fed to the fuel spill valve and the high energy igniter units on the engine. A further supply was then fed to the selected cartridge for 5 seconds then disconnected, which would cause it to fire. The expanding cordite gases were forced into a turbine starter which would spin the engine up to 2000 rpm then automatically disengage. Fuel would be drawn through the engine by this process and ignited.

Javelin start upThe cartridge start created lots of noise and black smoke as the picture shows.

Later marks of Javelin used an AVPIN start. This used a much smaller cartridge that was used to ignite a charge of AVPIN, a very inflammable fuel. The expanding gases from the burning AVPIN would be used in the same way to spin up the turbine starter.

SAC Terry Jones has kindly sent me this description from when he worked as a member of a Javelin ground crew:

"I served with No 1 GWTS at RAF Valley in 59-61. We had six Javelins with Firestreaks doing the missile trials. The cartridges they used were about 1.5" dia 6-7" long. Black Plastic bodies and the breech took three. 'WET' starts, when the thing did not fire up on the first or second shot, were always an exhilarating sight, with many yards of flame from the tail pipe. Incidentally, I have had many a meat pie from the NAAFI wagon re-heated in the tail pipe after a sortie!"

Allen Mawby remembers the AVPIN starter:

"[...] the Mk 7 and 9 used AVPIN start. A small cartridge similar in size to a 12 bore pressurised and ignited the highly volatile Avpin which powered a small turbine which in turn started the engine.

This system was truly bad as the Avpin often either exploded the high pressure pipe lines, which ran through the main electrical and hydraulic bay in the underside or caused the turbine to overspeed, shed all its small blades through the engine intake which normally resulted in an engine change.

If the pipe lines exploded the wings were removed and the remainder was sent to be rebuilt!

I cannot remember a black powder cartridge start system ever causing damage. Avpin starts caused immense damage."

Mike Guy remembers similar problems:

"[...]later marks of Javelins were fitted with 'AVPIN' starters. Avpin was a very volatile fuel and the starter plumbing supplying the Avpin to the starter was prone to leaks.
As I remember fires during start up were not too uncommon & it wasn't unusual to see a ground crew member "legging" it across the tarmac closely followed by the flight crew."

Radio and Radar Installation

The Javelin carried a number of electronic systems which at the time were very sophisticated. To enable it to fly and fight at night and in all weather conditions, it was fitted with various pieces of radio and radar equipment.

Using the radar scanner mounted in the nose it could locate its target at a distance and present this information initially to the navigator then later on in the interception to the pilot through his gunsight. This was a device called a ĎCollimatorí which projected signals from the radar system onto an angled piece of glass in front of the main reflector gunsight.

Donald F. MacLean served as a Radar operator on Javelins and has sent me the following notes: 

In your technical notes you say that the airborne radar had a range of twenty miles. As a Nav/rad i.e. a Navigator/radar who served with 72 Squadron could I say that such a short range would not have had much value at closing speeds of around 1,000 mph! In fact the maximum range was in excess of fifty miles. The Ground Control Intercept (GCI) controller would vector us towards the target(s) until we could take over having acquired the target on the radar screen. After which the navigator took over and [hopefully] instructed the pilot to manoeuvre into a firing position. As we were still only cannon equipped that meant closing in to about 300 feet in trail until we could visually see the target.  If the target became aware of us, and commenced evasive action, this could become quite hairy! In fact, at one point of lessening confidence on my part, I was beginning to have difficulty in pushing the interception to this point. I had to pace out 100 yards on the apron, behind a parked aircraft, to convince myself that this was a pretty fair distance, and at a matching speed with the target, it was perfectly safe!

The designer of the radar must have had a warped sense of humour. The 'joystick' with which the navigator controlled the azimuth and the elevation of the antenna was definitely phallic in appearance! And it had a little 'tit' on the end which enabled you to 'lock-on' to the target once it was well acquired.  After that the radar tracked the target to the exclusion of all else!  In other words, you were now completely blind to any other aircraft in the sky.  This could be quite exciting, in the dark, with no lights, and a mix of 'bombers' and other intercepting fighters.
[...] Returning to the range of the radar. If, as happened sometimes, we got exceptional range from the equipment we always put in a fault report on landing as it was an early indication that the magnetron was about to blow!

Another specific Javelin-related thing that might be of interest is the fact that the Javelin had ejector seats - unlike the Meteor 12/14!  Escape from the Meteor entailed a good chance of the navigator wrapping round the tailplane - with predictable results!  Unfortunately, there was a down-side to the Javelin radar equipage that we had on our aircraft.  All navigators, before converting to the aircraft, had to be measured from hip to kneecap.  Why? the radar set, in its operational position, projected far enough back in the cockpit to ensure that, if one's thighs exceeded this critical measurement, then one's lower appendages might be left behind on ejection.

The joys of nav-radding!

 

A GEE navigation system was installed which worked by measuring a phase difference between signals from two ground stations. When this information was transferred to a special map showing intersecting hyperbolic curves, it provided the navigator with a position fix.

A special type of radar altimeter allowed blind flying to very precise heights above the ground and there was also an ILS (instrument landing system), which could guide the aircraft through cloud or fog down a predetermined slope to the runway threshold until the pilot could see the runway lights.

The Javelin also made use of two special identification systems.
IFF (Identification Friend or Foe), a ground-to-air system; and
FIS (Fighter Identification System) an air-to-air system.

Cpl. Maurice Saltmarsh served with No.29 Squadron as a radar technician and has sent me the following notes: 

"The Javelins I worked on did have IFF equipment ... triggered from a signal from the ground radar station. If the aircraft being "interrogated" had IFF fitted (and had the correct mode selected) then a response signal was transmitted back to the ground station which appeared as a secondary blip adjacent to the target echo on the ground PPI screen."

"[...]FIS (Fighter Identification System) with a Trans/Rec. unit at the trailing edge on the top of the tailplane. The Navigator in the aircraft behind pushed a button on the main search radar indicator unit which caused his FIS to interrogate the FIS in the aircraft in front of him. If the one in front was fitted with FIS, the one behind would receive a blip under the blip from the search radar. If the front aircraft did not have FIS fitted, I assume it would be treated as "the enemy"." 

Some of these systems are described in more detail below.

Radio Systems

ARI 1801

This is the telebriefing system. The crew could be briefed before take off whilst sitting in the aircraft, by means of a land line from the briefing office connected to a plug inside the port wheel bay. The lead was incorporated into the port wheel chock and disconnected automatically as the aircraft moved off.

On the pilotís port console is an amber warning lamp which is lit when the cable is connected, next to this is his press-to-transmit switch. Both the pilot and navigator were able to speak to ground control.

When the telebriefing cable is plugged in, the MIC/TEL connections to the radio are isolated which prevents telebriefing information from being inadvertently transmitted over the UHF system.

ARI 18124/1

This is the UHF radio transmitter/receiver, it covers the band 225.0 to 399.9 MHz using 1750 channels spaced 100KHz apart. Nineteen channels are preset. The control unit is mounted on the pilotís port side at the top left corner of the panel. Next to this is a tone ON/OFF switch which permits Morse signals to be transmitted by modulating the carrier wave with an AF (Audio frequency) signal.

Three radio change-over switches are located on the pilotís port inner instrument panel. They are the intercom switch, the normal/standby set selector, and the power supply switch to select normal bus-bar or emergency battery.

Two UHF aerials are fitted and the pilot could select which one to use with a switch on the starboard throttle lever. The reason for switching aerials is that occasionally the aircraft itself could cause an obstruction in the line-of-sight between an aerial and the aircraft or ground station being worked.

ARI 5284 (AYF)

AYF is a development of the radar altimeter. An FM radio signal would be transmitted from an aerial near the front of the aircraft, (the blade aerial under the port intake) reflected back from the ground and picked up by a similar aerial mounted further back along the fuselage. Both outgoing and returned signals were fed into a detector unit which superimposed them and amplified the resulting Ďbeatí frequency. This was fed through square wave limiter and counter stages to produce an electrical signal in exact proportion to the aircraftís height above the ground. This was presented to the pilot and navigator using a calibrated dial and, for the navigator, a row of three lamps coloured green, amber and red. The pilotís display includes only the red lamp. Green means the aircraft is at the preset altitude, amber means any altitude above this and red means below. Two ranges, high and low, could be selected by the pilot; high measuring 0 to 4000 feet, low was from 0 to 400 feet. This would have been a valuable aid to blind flying, in the Javelinís role as an all weather night fighter.