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A pair of Airfix Hawks in 1/72. Finished.


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Radar Altimeter I 'spects

Intuitive posting ;)

Correct - as opposed to BARALT; Barometric Altimeter, the thing driven through the static ports on your pitot tube, which has varying degrees of lag. Descending at night to low level over the sea on BARALT only can be decidedly scary. RADALTs are lovely.

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RADALTs are lovely.

And an important part of the weapons delivery system on a Jag.

Need to accurately know (basic) stuff such as height speed and flightpath (plus other more subtle stuff which we don't need to trouble ourselves about here ) to accurately predict where a dumb weapon will hit the ground.

The kit used the Radalt to accurately measure the height above the ground to feed into the calculation of where a given bomb would impact.

Here's still from the a HUD wet film recording (hey - that counted as cutting edge tech when the poor old jag was built). It's colour film - as befits the special occasion of being taken at Red Flag.

The Radalt's on and working - cos there's an R in front of the height reading (in feet agl) and the horizontal CCIP line (Continuously Computed Impact Point) on the bomb fall line is the predicted impact point of the bomb(s). Speed is in Knots. Wind and flightpath have been taken into account.

dda697c0-9d0d-481d-b5ec-017971f2ab68_zps

Actually - I may have been misled by the dust/smoke cos it looks like I'm gonna miss just to the left of the tgt (never was any cop at this flying lark).

Note also that I'm being a good boy and making sure I'm not busting the 100' authorised minimum separation distance (filmed target runs were always looked at in the debrief) - that said I am descending so I was probably thinking that 125' was a bit on the high side to retain credibility.

The problem with the Radalt in weaponeering is that it measures distance directly below the aircraft - so the prediction is only accurate if the ground is flat. If the ground is sloping then the predicted impact point will be wrong. And that is why the Jag had a laser in the nose - to accurately measure slant range to a target/impact point........

Ain't gonna have anything interesting (or not) left to say by the time I build a Jag. Have to either fall back on just building a model (heaven help us) or do as I've done so far and just repeat myself........

The Hawk T1/T1A had no radalt or inertial platform and so the (basic) sighting system relied on the pilot flying at a predetermined speed and height above the target - which had to be judged by mark one eyeball. Excellent practice for training studes - not so good if you want to reliably splat a target. In the Hawk we generally did shallow dive attacks (5 or 10 degree - can't remember which) I think because it tended to allow a more accurately reproducible approach and reduced the margin of error.

10degreediveSAP_zpsac1d77d6-1.jpeg

Edited by Fritag
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The RADALT is equally vital in the Sea King as one of the inputs to the (ahem) cutting edge 60s tech "computer" which was the Louis Newmark AFCS (automatic flight control system). The other inputs being the Doppler (to give drift), speed and a gyro-stabilised platform ("stable table") to give attitude. Without the AFCS, dunking at night would be impossible - hovering with no visual references at all is a recipe for crashing within seconds. Once in the hover with the sonar body in the water, sensors in the pit head gear came into play, flying the aircraft to keep the cable vertical. If you look at some walk round shots of a Sea King or Wessex 3, the cable sensors are the big rollers at the top of the shaft. The two types of hover were therefore Doppler hover (genuinely stable in position) and cable hover (cable vertical, so aircraft drifting with the movement of the sea if there was tidal stream or current).

Basically, the pilot flies the aircraft into a "gate" (usually 200', 90kts, wings level, heading into wind) and the non-flying pilot "engages down" (presses a button in the AFCS) and the aircraft does the rest, ending up in a 40' stable hover. There are variations on this theme; for instance the pilot can disengage channels of the AFCS independently, so probably the majority of "jumps" (as they were called) the computer flew the height channel and the pilot flew the heading, to allow tighter turns and avoiding the need to head into wind before descending (i.e. you turned into wind on the way down). The into wind was called a "full" jump, and AFCS flying only height a "modified" jump.

By day you can do this all visually / manually, but it is a complex skill and a perishable one, so to remain current all pilots had to do a set number of FCS transitions in various conditions, day & night. There's a column in my logbook to record them.

To be fair, given its age & complexity, the box worked pretty well. However, it could give you some scary malfunctions - the worst being a Radalt failure during the transition down, which would mean the box didn't feed the power in at the bottom and tried to fly you straight down into the sea. Failure of the stable table could be nasty, too - without warning the aircraft could assume some very peculiar and disorientating attitudes. The night AFCS malfunctions check ride ("night dunking check") on AFT was the hardest sortie of my entire flying training - way worse than night deck landings.

None of this would have been possible without a Radalt.

[Edit: and none of this has anything much to do with Airfix's Hawks. Sorry, Steve!]

Edited by Ex-FAAWAFU
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While we're off topic, what sort of rate does the RADALT sample at and does it aim straight down or slightly ahead? I would imagine that it would be quite confusing if it was darting up and down as you fly over lumps and bumps on the ground but equally if it were averaging everything out, the lump of granite rising ahead could present a (terminal) problem. This is just a curiosity thing; leisurely VFR flying with an ageing pressure altimeter suits my ability and speed of reaction just fine.

Kirk

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We had a RADALT in Albert. In fact some Alberts (mainly the SF 'frames) had two RADALTS, one for each pilot! :o:
However, in the Dom we had a Mk19F Baro Alt plus the good old Mk 1 eyeball.

Low level on 'Functional' sorties (ie Nav trg ones) was (at least in the pre DAU days) 500ft on 8 standard routes. The reason being that the studes used 'radar prediction' photographs to show what the ground would look like via the Ecko 190 radar. Later on with the better radar in the post DAU aircraft, low level was 250 ft and std routes were a thing of the past. All of this judged by 'setting the picture' by eye.

All well and good, but if you got off track, off heading, or off height, then the radar predictions would look nothing like what the stude saw in the scope.

So there we are bimbling along somewhere north and east of Spadeadam; it's a phase 5 summer's day with clear blue skies and visibility to the natural horizon.

Now, bear in mind that the studes were encouraged to make the pilot aware of the proximity of high ground ahead - even though we could invariably see it, we often pretended the weather was 'skoshy' and not the 5.5Km vis, 1500m horizontally and 1000ft vertically clear of cloud that we were required to operate in (we were pretending to be an all weather Tornado remember?). Actually we often operated to what was termed 'RAFG Brit VFR' (those used to low level in Germany will know what I mean), but I digress.

Those who know the area I was operating in will know that it is punctuated by some (quite large) rolling hills - hills that the Dominie will not out climb if you get too close to them. I'm expecting the following calls fom the Nav:

"CUT OFF, 5 miles, best escape is xx degrees turn R/L, hdg xxx."

To which I would reply that I was either visual with the high ground, or that it was NOT SEEN. If I called NOT SEEN then the calls would continue thus:

"CUT OFF, 4 miles, best escape is xx degreees turn R/L, hdg xxx."

To which I would reply that I was either visual with the high ground, or that it was NOT SEEN.

"CUT OFF, 3 miles, CLIMB!".

The low level emergency abort in the Dom was sporty to say the least: Full power, wings level, pitch the aircraft until the horizon bar on the artificial horizon sat on the 60 degree AoB markers, and hold that attitude until you'd climbed through Safety Altitude. Good fun VMC, pretty bloody hairy IMC!

I'm flying over a large forest on high ground with big hills on the nose. What I actually heard was:

"No radar picture."

(Hmm. Bloody Nav's with bloody finger trouble.)

"No radar picture."

(C'mon Nav get it sorted out.)

"No radar picture,"

(Hmm, that's a tad odd. Have you recycled the kit, Nav?)

"Radar re-booted, no radar picture."

At which point our intrepid Dominie Captain is heard to utter the immortal words:

"Holy, f***ing, doo-doo!", and pitched the aircraft aggressively skywards.

Yes I'd fallen into that well known visual illusion trap. What I thought was a forrest of mature conifers was, in fact, a plantation of baby trees and we were well below 500 ft. I don't (to this day) know how low we'd got but I'm guessing (by the fact we had no radar returns) well under 100 ft, possibly less than 50 ft. :yikes:

As they used to say....I learnt about flying from that.

I submitted a CONDOR (CONfidential Direct Occurence Report) but that (I assume) got lost in the bowels of the Inspectorate of Flight Safety. Nothing was ever done and the Dom (shamefully) was never fitted with a RADALT.

[Edit: and none of this dit has anything at all to do with Airfix Hawks. Mea Culpa, Steve!]

Edited by Ascoteer
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Thing is, RADALT's may be lovely, but is it also a piece of kit that you can put too much trust in - as suggested in the recently released interim report of the tragic Lynx crash in Afghan last year...?

Anyway as we're all apologising for posting off topic stuff in this 'Two Hawks' thread, get us back on track with some more nice modelling Mr. F...!!

K

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We had a RADALT in Albert. In fact some Alberts (mainly the SF 'frames) had two RADALTS, one for each pilot! :o:

I have recently obtained (after months of looking) a copy of Tony Buttler's superb book about the Sea Vixen. Unmissable if you are interested in the aircraft, but quite hard to find.

The Vixen had two independent BARALTs, the pilot's fed from the port pitot system and the Looker's from the starboard. The DH110 / early FAW1s had a RADALT as well, but they had some snags with it.... so the thing was disconnected, the gauge remaining in all Vixens for their entire career, but never functional. For an aircraft that routinely flew at high speed at very low level over the sea at night, this seems to me a completely bizarre decision - and the various aircrew quoted by Tony Buttler seem to agree with me.

Anyway, the two BARALTs. The Observer could see both gauges from his seat - his own in front of him, obviously, and the Pilot's at an angle through the gap in the cockpit. On a night approach to a deck the pilot would be "eyes out" on the meatball, and (in the Mk2) using an audio warner connected to an early angle of attack device and an auto-throttle system - i.e. flying everything using attitude / alpha (Steve, you were quite right in our discussion of this on my FAW1 thread).

The FAW1 didn't have this set-up, though, so the workload for the pilot in some conditions must have been very high indeed (which no doubt contributed to the high accident rate in the aircraft's early career). The Looker spent much of the time monitoring the two BARALTs, and in many cabs there was a significant difference between them - 50' or more, which is a hell of a lot when you are on finals to a deck (especially bearing mind that deck lighting only came in during the Vixen's career; initially they'd have very little visual deck reference info at all until the very last minute). When you factor in the fact that all BARALTs have an element of lag....

Balls of steel, those boys!

Debs - like all of us, my Beefers told me all about the pine tree optical illusion when low flying, and I suspect I thought] it was exaggeration... until I had a similar adrenaline exploration of the flight envelope to yours. I couldn't even blame it on a student Nav; it was pilot VFR low level NAVEX, clock-to-map-to-ground stuff. Not even sure we had a Looker on board.

Keefr22, you can put too much trust in ANY instrument. But flying over the sea at night, no question I felt better with one than without.

P.S. Did you RAF Johnnies use QFF? For non-Service aviators, the Q code was an old fashioned code for all sorts of aeronautical malarkey from the era when morse code was your only friend. QNH (sea level barometric pressure) & QFE (the setting to give an accurate BARALT reading at a specific place - usually an airfield) were & probably still are in very widespread use. At sea we often used QFF; for instance, if Sea Kings were operating a passive ASW barrier 50-100 miles away from Mum in mid-ocean, the cab coming off-task would give QFF to the cab coming on: set the BARALT to match the RADALT in level flight (i.e. with the lag element taken out), to give a pressure setting for your particular piece of miles-from-anywhere-Oggin. In some circumstances it would differ markedly from the setting given by the Metmen on board, and it could be a life-saver if your RADALT packed up.

Edited by Ex-FAAWAFU
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Q codes are brilliant. Lot's of people try to tell you that they are acronyms (Field Elevation, Nautical Height etc) but that's b******s as I think is explained in the wiki article.

The QDM routine is quite fun iirc; you have to keep talking so that the operator can get a decent bearing on your signal. Can't recall if it's the same for QTE but both come up in the PPL Nav exam so you need to know them for at least a 24hour period!

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We used to use QDM, too. Some of them sound rather plaintive; QAK & QAU, for instance... I'd have thought the last thing you need in those circumstances is to decode a response!

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While we're off topic, what sort of rate does the RADALT sample at and does it aim straight down or slightly ahead? I would imagine that it would be quite confusing if it was darting up and down as you fly over lumps and bumps on the ground but equally if it were averaging everything out, the lump of granite rising ahead could present a (terminal) problem. This is just a curiosity thing; leisurely VFR flying with an ageing pressure altimeter suits my ability and speed of reaction just fine.

Kirk

Hmm - Good question. And I'm not going to allow the mere fact that I don't know the answer stop me from answering :)

The Radalt wasn't there principally to assist with terrain avoidance - so your probably thinking about it from a slightly false perspective.

Terrain avoidance and judging the flight path to keep as low as practicable whilst not busting your minimum separation distance - whether 500', 250' or 100' - was down to the mark one eyeball. The Radalt told accurately from movement to moment what your actual height above the ground was and so was very useful feedback - but at 450kts (230 meters per second) you determine your flight path looking well ahead.

There are exceptions of course. The more predictably flat and featureless the terrain then the more the Radalt becomes an important - to the point of being vital - aid to judgment of height. Over the sea is the prime example (as per Crisp and his clearly suicidal night/poor viz scary-daft low level level antics) but also say the Desert.

It was also a life saver because it gave as a low height audible and visual warning if you went below a manually pre-set height - It probably would have saved Debs from her visual illusion trap with the baby trees. It saved my life and it certainly saved plenty of others too. But I bet for some unlucky s*ds all it did was alert them to their impending doom - if the ground was rising too steeply in front of say - then the warning may well come too late. Having a radalt does not confer any additional safety to flying low level over undulating terrain in poor viz.

So back to the question:

(1) I don't know the rate at which it sampled - but it may even have been a constant wave radar and so sampling continuously - (2) I think it will have been a cone shaped beam aimed vertically downwards - and I say that because (i) the information wanted was the height above the ground movement by moment and (ii) seeing as the waves travel at the speed of light I don't suppose it needed to be angled forward (but I could be wrong).....(3) The reading on the HUD was digital and read to the nearest 5'. I don't know the refresh rate but it will have been designed not to be so fast as to render it unreadable - but from the subjective point of view it did indeed change rapidly when flying over jagged terrain - otherwise of course it was kept rock steady by the truly unfathomable skill of the pilot in accurately terrain following. Part of the above answer may be false......I'll leave you to work out which bit :)

you can put too much trust in ANY instrument. But flying over the sea at night, no question I felt better with one than without.

P.S. Did you RAF Johnnies use QFF?

I can believe it.

No never used QFF. Only QFE, QNH and the standard pressure setting of 1013.

Anyway as we're all apologising for posting off topic stuff in this 'Two Hawks' thread, get us back on track with some more nice modelling Mr. F...!!

Well a wee bit more modelling perhaps - dunno about the 'nice'.

So having exhausted the the Ram Air Exhausts - it's on to the Ram Air Intakes :)

Airfix forgot that intakes have to have - well an intake!:

9A3BE0F1-85CC-4E7A-8D38-0A717C5D1AB8_zps

I could have tried drilling em out - or crash moulding em as I've done before - but I thought I'd give the Quick Boost resin jobs a go:

image_zps0pmf08lf.jpg

So. Carve the Airfix efforts off, followed by some smoothing and careful measuring and marking:

image_zpsfd9zqdkz.jpg

More care needed to separate the tiny intakes:

image_zps6a3js18y.jpg

Practice go just using Krystal Klear as a temporary fix:

image_zpsgx0jksd5.jpg

Bite the bullet and go for it with some thick cyano (to give a few moments fiddle time) followed up with some thin cyano and capillary action followed by some Mr Surfacer 1000:

image_zpsz5m290i8.jpg

And at the same time filling the fictional Airfix trenches :)

Waiting now for the Mr S to dry so they can be smoothed down.

There Keef. Not much of an update - but summat....

Edited by Fritag
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...otherwise of course it was kept rock steady by the truly unfathomable skill of the pilot in accurately terrain following. Part of the above answer may be false......I'll leave you to work out which bit :)

Ho ho ho. :D

(Loving the Hawk btw :popcorn: Do you have a plan for the dome headed rivets aft of frame 20(?)? They're taller than the panel lines are deep, so check if Airfix have supplied a bag of ball bearings for you to stick on. More seriously, one of the amazingly good 1:32 builds on BM used Archer self-adhesive jobbies but I wouldn't imagine that they do anything small enough for 1:72)

Edited by Kirk
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Nice inlets Steve, good stuff that yaller primer innit...

I will enjoy seeing you seeing off the big rivet mystery :)

And fer pity's sake you lot, DO not I say Do Not stop with the thread drifts

They make all of these threads into truly memorable stories, they are fabbullus

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P.S. Did you RAF Johnnies use QFF? For non-Service aviators, the Q code was an old fashioned code for all sorts of aeronautical malarkey from the era when morse code was your only friend. QNH (sea level barometric pressure) & QFE (the setting to give an accurate BARALT reading at a specific place - usually an airfield) were & probably still are in very widespread use. At sea we often used QFF; for instance, if Sea Kings were operating a passive ASW barrier 50-100 miles away from Mum in mid-ocean, the cab coming off-task would give QFF to the cab coming on: set the BARALT to match the RADALT in level flight (i.e. with the lag element taken out), to give a pressure setting for your particular piece of miles-from-anywhere-Oggin. In some circumstances it would differ markedly from the setting given by the Metmen on board, and it could be a life-saver if your RADALT packed up.

That's exactly what was done on the Nimrod and also what we did 'Dahn Sarf' on 1312 Flt when we were doing MRR (Maritime Radar Reconnaisance) with Albert.

I didn't know it was called QFF though. Cool! Every day's a schoolday - we A2s are never too proud to learn something new. :)

I can only echo Crisp's comments about RADALTs and the oggsplash. IMHO they are essential when flying low level over the sea, especially in 'goldfish bowl' weather. Considering I helped develop the new Gp2 Nav course to be effectively a Nimrod lead-in course, the fact that they never fitted the Dom with such an instrument was downright bloody criminal. I had one or two squeaky bum moments that still make me shiver.

Edited by Ascoteer
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Those Quickboost parts do make quite a difference.

I think you're right - and they were only £2.50.

Rubbed down the Mister S and given the Ram Air Intake/Exhaust decking a squirt of Tamiya Primer as a check. The primer will need micromeshing in due time.

Here's an Airfix original to compare with the scratchbuilt exhaust/Qickboost intake version:

64694941-2610-40D3-AAF6-36646212578F_zps

40C86374-699C-4D97-B8B3-CCF4AED0274F_zps

Perhaps not much to show for a few sessions work - but it looks more refined and with finer and more defined detail - which is what I was after.

Ok. now what? - I need to move the nose wheel U/C bay back about 1mm - and box in the U/C bay. Might start that.......or I might do something else.

Edited by Fritag
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Nice work - small details, but they make a big difference.

By the way, I have been meaning to ask - what's the orange-y filler you are using? It looks very fine grained, but I don't recognise it.

Never even thought of the Nimbats, Debs - of course they used QFF as well.

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