Sea Vixen avionics

[zen]

Searched a lot have'nt found much, and nothing here on this. So since I'm interested thought I'd start a thread and see what people know.


Seems from testimonials on the SeaVixen site the AI.18 set had a average detection range of just 20nm. Apparently has a lock on feature.

The dish is 28 inches diameter.

Also from that site the FAW.2 had wide band homers for X and S band radars.

Skomer says it had a Violet Picture UHF set by Plessey.

 

[overscan (PaulMM)]

Not got much on AI 18 (been researching AI 23 instead

Took these at the De Havilland Heritage Centre...

 

[glmm]

From Tony Buttler`s "De Havilland Sea Vixen", published by Air Britain:

GEC AI.18 Radar: This was an X-band 180Kw airborne interception radar four use in 2-seat fighter aircraft. The maximum scanner coverage was +/- 100º in azimuth, +50/-40º in elevation and +75º in roll. It used a 29in parabodoidal scanner capable of tracking a target automatically in range and angle from very low ranges to 25nm. By mid-1958 airborne test had shown a 75% probability of detecting a Camberra bomber head-on at a range of 28nm at altitudes greater than 20.000ft and a closing speed of 900knots. An American B-47 bomber was also detected at 38nm. On its longest range setting of 10o miles it could also be used fro ASV and ground mapping. The later AI.18R provided all the facilities offered by the earlier mark but with the guided weapon outputs scaled for Red Top.

 

[zen]

Right now I've read Black Box Canberras by David Forster ISBN 9 781902 109534, which certainly deserves a plug!

We can say AI.18 started life as the successor to a conceptual dual band system, using S-band for Search and X-band for 'lock-follow'. AI.18 was simpler using just X-band and was decided to use a 160kW system with a 29" dish and raster scan aiming to detect a Canberra sized aircraft at 15nm, though clearly a larger dish option was being mooted as well.
Clearly this is was also aimed at intigrating the new guided missile efforts Blue Jay and Red Dean.
ISD was intended to be 1956, but by '52 delays in agreeing the spec pushed this back to '59.
Contractors where:-
G.E.C for the main system
DHP for the dish and it's actuator system.
with TRE (Malvern) acting as design authority.

Intention was a initial experimental system, proving the basic technology, Followed by a A system semi-engineered which would lead to a B system fully engineered before final production.
By '57 performance was much better than the initial requirements, and detection of a Canberra at 28nm being regularly achieved.
Trails of the basic AI.18 system for the RN's Sea Vixens came to an end mid 1960.

Additional was the Red Dean computer, development contract was placed with G.E.C. and planned trails for Feb-1956.

AI.18B (not to be confused with the B model) was a early '58 G.E.C and RRE study into improving the performance of the system. Intention was to equip follow-on orders of Sea Vixen FAW with the new set, but the RN decided to economise and fit subsequent batches of Sea Vixens with the basic set instead.
Trials however continued and G.E.C constructed a second model incorporating a switchable transmitter pulse-width and switchable receiver bandwidth which was never flown.This by '61
AI.18 achieved it's goal of extending detection ranges to 45nm against a Canberra sized aircraft.

AI.18R (Red Top Capable) added a collision course attack computer replacing the existing tail chase only Firestreak (Blue Jay) set. Introduced Angle-lock, Track-on-Jam, and improvements to Lock-Follow to cope with the higher speeds of closing supersonic targets. Program from Autum '61 to May '65.
AI.18R units delivered by mid-'64.

AI.18 AMTI, secomnd half of '58 G.E.C was working on the quartz delay line system.This was flown first in a Varsity and later a Canberra in 1960.Addition of Automatic Gain Control in '61 proved Lock-Follow was possible. G.E.C attempted to interest the Admiralty in adding this to the Ai.18Rin early '62 and with lack of interest the effort wound down by the start of '6
3. Though they did Development Cost Plan laying out the cost of addting AMTI to the AI.18R should the Admiralty change it's mind.

A second effort in AMTI using the AI.18 using transistors rather than quartz delay lines, was started in '65, flights in a Canberra in '67 and ceased in '68. System detected a Canberra flying at 500ft from 20,000ft at 20nm, system proving very successful despite it's limitations. This being the use of just 126 range gate filters for just a 5nm section of the radars range, though operator selectable.

 

[pathology_doc]

Is there anything available in detail on the attempts to incorporate a SARH illuminator for radar-guided AAMs? IIRC from BSP4, this had at least two false starts. The Sandys cancellation of all manned interceptors except the Lightning seems to have killed its impetus, but it's a surprise that there wasn't a push to develop it as add-on capability for both Sea Vixen and Javelin, both of which (as subsonic interceptors) would have benefited from the ability to give incoming enemy fast bombers a salvo of in-your-face missiles. Particularly true of the Javelin, which for reasons I have never understood seems never to have been updated for Red Top.

 

[Maury Markowitz]

AI.18 AMTI, secomnd half of '58 G.E.C was working on the quartz delay line system.

To what end? As an interceptor system, MTI would seem to have limited utility unless they were trying for sea search as well?

 

[zen]

AI.18 AMTI, secomnd half of '58 G.E.C was working on the quartz delay line system.

To what end? As an interceptor system, MTI would seem to have limited utility unless they were trying for sea search as well?

Oh I missed this, what it's achieving is look-down and lock-follow on low level targets. The prerequisite for shoot-down.

 

[Maury Markowitz]

AI.18 AMTI, secomnd half of '58 G.E.C was working on the quartz delay line system.

To what end? As an interceptor system, MTI would seem to have limited utility unless they were trying for sea search as well?

Oh I missed this, what it's achieving is look-down and lock-follow on low level targets. The prerequisite for shoot-down.

You don’t need MTI for that, inverse monopulse offers this with less complexity and was available from AI.23. AI.18 was a magnetron, IIRC, which means COHO MTI, which means serious suck on a rapidly moving platform.

 

[zen]

1. Why are you asking me?
2. I'm just reporting what they did. So obviously they felt it made sense.

 

[overscan (PaulMM)]

AI.18 AMTI, secomnd half of '58 G.E.C was working on the quartz delay line system.

To what end? As an interceptor system, MTI would seem to have limited utility unless they were trying for sea search as well?

Oh I missed this, what it's achieving is look-down and lock-follow on low level targets. The prerequisite for shoot-down.

You don’t need MTI for that, inverse monopulse offers this with less complexity and was available from AI.23. AI.18 was a magnetron, IIRC, which means COHO MTI, which means serious suck on a rapidly moving platform.

I'm not sure what you are talking about here. I'm not aware of any airborne radar using inverse monopulse techniques for clutter rejection. Semi-active seekers of this kind rely on a reference signal from the parent aircraft radar. AI.23 was 2 channel amplitude comparision monopulse as compared to modern 4 channel phase comparison.

GE did publish a patent for airborne radar monopulse clutter rejection but other analysis showed it was at best a very minor improvement when combined with MTI.

NAA pubished a patent on a monopulse clutter rejection method but it featured a dial-driven phase shifter which the pilot twiddled with while looking at the radar screen for which targets remained stable and didn't disappear. Not exactly ideal.

Low PRF MTI was sufficiently useful to form the basis of the E-2 Hawkeye's radar system. With the addition of DPCA it was useable over land too.

 

[Maury Markowitz]

1. Why are you asking me?
2. I'm just reporting what they did. So obviously they felt it made sense.

1. You posted it. Who should I be asking?
2. Sure, but the claim as to why doesn't. I believe you may be conflating two different features that were included for different purposes.

 

[Maury Markowitz]

I'm not sure what you are talking about here.

I am talking about look-down/shoot-down. You do not need MTI for look-down/shoot-down. One can imagine ways to use it for this role, with considerable difficulty using electronics of the era, but other solutions already existed and were being produced that would solve this problem.

Low PRF MTI was sufficiently useful to form the basis of the E-2 Hawkeye's radar system.

And the E-2 does not carry missiles and cannot perform a shoot-down role, It is a long-range, low-rate, low resolution EW concept. So its design parameters are dramatically different than an AI and different solutions can be used.

In contrast, Vixen has a specific design role that demands a higher angular resolution, PRF and sampling rate. This is why they selected a Culter feed conscan system in order to cue down to a couple of mils - this is demanded by SAHR and to only a lesser extent by IR, especially Firestreak which required relatively high angle resolution in caged mode. And COHO MTI is literally of no use whatsoever using the other design of the era, Red Dean, as it would require the same MTI system aboard the missile.

COHO MTI of the era was pulse-to-pulse, and even the changes in angle due to conscan would seem to make it difficult to use. As the system ultimately outputs changes of phase, and spinning the feed causes changes of phase, I am not clear how one would accomplish this, at least using a fixed-delay system like a quartz line and contemporary tube electronics.

So if the original reference said something like "MTI was considered to improve the Vixen's performance in the secondary strike role against small surface targets", then that makes sense. But claiming that they were considering it for shoot-down literally makes no sense.

Does anyone know how to remove all that quoting cruft above? I tried select/delete, but it did not work.

 

[starviking]

Does anyone know how to remove all that quoting cruft above? I tried select/delete, but it did not work.

If you delete the text you don't want, the nested quote brackets disappear.

 

[zen]

So books in storage, answer in Black Box Canberras.

Memory (dodgy) says late transistorised AMTI is AEW related, but earlier quartz delay line circuits effort AMTI is fighter AI related.
Lock-follow was achieved or sufficient for that.
Red Dean is early-to-mid 50's, Red Hebe mid-to-late 50's, AMTI is very late 50's to mid 60's. So more likely late Radar Red Top and next gen AAM related.

 

[Maury Markowitz]

If you delete the text you don't want, the nested quote brackets disappear.

So here is what I did:

1) press reply
2) selected starting with my text
3) result above. I can't seem to kill off empty sections like zen's innermost section there

Ohhhhhh... it disappears when you post, not during edit. Didn't notice that.

 

[zen]

If you delete the text you don't want, the nested quote brackets disappear.

So here is what I did:

1) press reply
2) selected starting with my text
3) result above. I can't seem to kill off empty sections like zen's innermost section there

Ohhhhhh... it disappears when you post, not during edit. Didn't notice that.

It's even more of a head twister when you're doing it on a smartphone.

 

[yellowaster]

The projected AI Mk 18 AMTI used a non-coherent clutter-referenced (not COHO) technique - which worked reasonably well over the sea. It would have given the Sea Vixen the ability to detect and (under more limited circumstances) lock-follow a low-altitude airborne target from medium altitude - a useful capability for any fighter. Various implementation techniques were investigated - delay line, storage tube and multiple range-gate and filter.

 

[starviking]

If you delete the text you don't want, the nested quote brackets disappear.

So here is what I did:

1) press reply
2) selected starting with my text
3) result above. I can't seem to kill off empty sections like zen's innermost section there

Ohhhhhh... it disappears when you post, not during edit. Didn't notice that.

It’s very non-intuitive.

 

[Maury Markowitz]

The projected AI Mk 18 AMTI used a non-coherent clutter-referenced (not COHO) technique - which worked reasonably well over the sea. It would have given the Sea Vixen the ability to detect and (under more limited circumstances) lock-follow a low-altitude airborne target from medium altitude - a useful capability for any fighter. Various implementation techniques were investigated - delay line, storage tube and multiple range-gate and filter.

Do you have any details on this, or sources?

AI.18 DID use a magnetron, right? And it clearly used conscan for lock-follow, you can see the Culter feed. I'm lost as to how you do clutter rejection while using conscan.

 

[yellowaster]

The projected AI Mk 18 AMTI used a non-coherent clutter-referenced (not COHO) technique - which worked reasonably well over the sea. It would have given the Sea Vixen the ability to detect and (under more limited circumstances) lock-follow a low-altitude airborne target from medium altitude - a useful capability for any fighter. Various implementation techniques were investigated - delay line, storage tube and multiple range-gate and filter.

Do you have any details on this, or sources?

AI.18 DID use a magnetron, right? And it clearly used conscan for lock-follow, you can see the Culter feed. I'm lost as to how you do clutter rejection while using conscan.

There are various references publically available on the non-coherent AMTI technique, especially the delay-line cancellation variant. I believe it originated at MIT (Butterfly/Firefly). As for AI Mk 18, primary sources are mainly RRE reports. AI Mk 18 did use a magnetron and also conical scan for lock-follow. The AMTI technique requires amplitude comparison of returns from three pulses (double delay-line) - I seem to recall they had to add AGC to get it to work in lock-follow . But in any case, the trials results show it worked reasonably well and that the technique was practical - sufficiently so that GEC was asked to propose a delay-line AMTI for retrospective fit to AI Mk 18R.

 

[Maury Markowitz]

There are various references publically available on the non-coherent AMTI technique, especially the delay-line cancellation variant. I believe it originated at MIT (Butterfly/Firefly). As for AI Mk 18, primary sources are mainly RRE reports. AI Mk 18 did use a magnetron and also conical scan for lock-follow. The AMTI technique requires amplitude comparison of returns from three pulses (double delay-line) - I seem to recall they had to add AGC to get it to work in lock-follow . But in any case, the trials results show it worked reasonably well and that the technique was practical - sufficiently so that GEC was asked to propose a delay-line AMTI for retrospective fit to AI Mk 18R.

Thanks, this is very useful!

 

[yahya]

The images on this website suggest that the Sea Vixen used the ARC-52 UHF radio:

Thunder & Lightnings - de Havilland Sea Vixen - Walkaround Photos

Cold War British military aircraft, including history, surviving airframes, profile drawings, photos, walkarounds, links, references. Also viewing guides for UK airfields and the Test Flying Memorial

www.thunder-and-lightnings.co.uk

Also, this bird was AGM-12B Bullpup-capable, so I presume it must have been equipped with the AN/ARW-73 Radio Guidance Transmitting Set or its British clone.

 

[yahya]

@zen
Did you managed to compile the list of the Sea Vixen avionics? I got interested in this bird, but indeed there is a scarcity of technical information on its avionics suite. What I managed to assess mostly from online pictures and a website on that jet, is that these items were most likely used.

• Either the Collins ARC-52 UHF or Plessey's PTR 175 VHF/UHF comm sets;
• Perhaps a single-channel emergency UHF set; something like the Burndept TR.2002, but operating in UHF, not VHF;
• British-made TACAN ARI 18107 by STC or US-made Hoffman ARN-72;
• The IFF is a mystery. The incomplete manual says that the Mk 10 (ARI 23187 ?) was used, but there are photos clearly showing a US-made APX-6A IFF with an APX-25 SIF on the vertical console between the pilot's and radar operator's seats';
• I am not sure where the control panel for the the ARI 18012 Intercom with telebriefing was located in the cockpit unless a dedicated ICS was used.

What I cannot match with the avionics list is a small round instrument in the bottom center of the instrument panel in the axis of the control column, which displays two white lines crossed. It looks like a VOR/ILS indicator, but I cannot find any associated control panel. TACAN usually used two separate indicators in that time with different appearance. I guess that it was the Violet Picture UHF DF indicator.

Also, there is a big round instrument with four yellow "rays" on the top left side of the instrument panel, and I have no idea what its purpose was. At first, it looks like an RWR, and not like undercarriage control lamps.

I am still trying to verify the above mentioned list, so any comments are welcome.

 

[yahya]

Could someone explain please what was the strange round instrument with four yellow stripes that is visible on the top left corner of the instrument panel on picture from the link below?

https://www.jetphotos.com/photo/8296344

 

[Flame2512]

Could someone explain please what was the strange round instrument with four yellow stripes that is visible on the top left corner of the instrument panel on picture from the link below?

https://www.jetphotos.com/photo/8296344

It is the Red Top ready Indicator.

From the pilots notes:

4 Pure air system
(a) Two air bottles, one each side of the nose-wheel bay, are ground-charged with pure air to a pressure of 4,500 psi for cooling the detector coil in the Red Top missiles. The bottles are installed in an insulated duct. Air from the 15th stage compressor mixed with cold air from the CAU is fed into the chamber, formed between the duct and the bottles, to heat the bottles and so maintain pressure when the ambient temperature is low.
(b) The endurance of the pure air system is sufficient for 16 missile armings plus 243 missile minutes (continuous running after 96 missile minutes). This endurance is related to a bottle charge pressure of 4,500 psi at a temperature of +20°C. The state of bottle pressure is indicated by the AIR indicator lamp on the Red Top ready indicator S on panel AU as follows: —

• Light out—pressure above 3,000 psi (supply satisfactory for arming and running).
• Light on steady — pressure between 3,000 psi and 1850 psi. Supply satisfactory for one arming and running only. Arming should be carried out as soon as possible after the light comes on.
• Light on flashing — pressure below 1850 psi. Supply unsatisfactory. If arming has previously been carried out it must be cancelled.

An additional pressure indicator in the observer’s compartment, on panel N, shows the combined bottle pressure.

 

[yahya]

Thank you very much indeed for the reply. The Sea Vixen pilot's notes are actually very difficult to get and I have not seen them, hence the avionics setup is still a mystery.

By the way, could you please advice if the Sea Vixen had an onboard RHWR?

 

[zen]

S-Band and X-band homing if memory serves. Much like the Buccaneer.

 

[yahya]

Would such features be manned by the radar operator?

 

[overscan (PaulMM)]

https://www.secretprojects.co.uk/De%20Havilland%20Sea%20Vixen%20Tactical%20Manual_sm.pdf

Original Source: https://www.seavixen.org/seavixen-technical-documents/sea-vixen-tactical-manual

 

[yahya]

Thank you very much indeed.

By the way, does anyone have the complete FAW1 or FAW2 pilot's notes with cockpit photos and description? At https://www.seavixen.org/seavixen-technical-documents/faw-mk2-pilot-notes, the cockpit photos are incomplete, alas.