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SAR S-92 Missing Ireland

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SAR S-92 Missing Ireland

Old 18th Apr 2017, 02:31
  #1161 (permalink)  
 
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Originally Posted by jimf671 View Post
That works out Pruneface. Double-checked the AAIU report and the Irish SAR Framework and put the numbers in Google Earth and it works out about 11nm into the UK SRR.
Thanks for your confirmation. I thought I was losing it for a while there.

So, if the FV was actually in the UK SAR area of responsibility at the time of the call, why was the UK SAR not the prime mover, using if necessary and by dint of International Agreement, the Sligo SAR resource (on a call for assistance) but not obviously requiring the Dublin based R116 to get involved. In addition, considerable mention has been made in respect of the 'out-of-hours unavailability' of the Irish Aer Corps CASA resource(s) and indeed, the IAC has on occasion been denigrated for this since the crash.

Perhaps I'm over egging the importance of this in my own mind, and perhaps a very fluid 'boundary' exists worldwide between SAR areas of responsibility and all this is irrelevant, but I'm just getting a very bad feeling about this tasking and each of the individual missions that flowed from it, some of which in themselves create questions that have not been satisfactorily answered, not including the specific questions surrounding the crash itself that the IIAU is dealing with.
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Old 18th Apr 2017, 07:29
  #1162 (permalink)  
 
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Originally Posted by AAKEE View Post
For the comments on the 10nm scale, I dont se a big problem using 10mile scale.
This scale still shows everyrhing, scaled down though.

For a let down to hover( transition down) we use a fixed scale, more zoomed in than 10 nm. But then you do this close to something, and need to see this more in detail. I think there also a good thing to use a standard setting making you refer to the picture at a 'known' scale.

For a descent to below clouds and the plan to continue flying I think the idea to see radar returns that give you SA in the radar picture, for example the shore line or islands is good, that may be the reason for that selection. Too zoomed in and you loose the SA and the easy relation to a map/moving map and so on.
(I would have worked with radar settings, and scale to make sure but thats not the point here).
Sorry AAKEE, but I disagree... If you are cruising at 200 ft RHT and NAV/LNAV coupled you are heading (or actually tracking) towards an obstacle which is 300 ft AGL high... and you don't have a visual contact with the target at distances 1,3 nm or 0,6 nm (ALTITUDE WARNING)... I think that the 10 nm scale was not the best option in order to avoid the collision... Then if the crew was not aware of the high obstacle ahead, it will be a SA issue and a different story...

Btw. I highly respect "Irish Aviation Community" and I know that the crew members were true professionals! RIP.

Last edited by Search&Rescue; 18th Apr 2017 at 20:10.
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Old 18th Apr 2017, 07:36
  #1163 (permalink)  
 
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Originally Posted by SASless View Post
What was the CHC In-Service training routine for ICG Pilots and Crew?

Many years ago as UK SAR was being shifted to the Civvie side from the Military....Crab and others raised concerns that then existing Training Hours and array of Training Tasks might decline.

Anyone able to share their knowledge about ICG training?
Hi SAS, I'm waiting for a reply to this one too!
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Old 18th Apr 2017, 08:02
  #1164 (permalink)  
 
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player104

A useful video that shows some of the pitfalls when interpreting the radar display. However note the range settings on the display and target return distances of between 20 and 40 miles. At close range settings the display can be much harder to interpret although all the points mentioned still apply.
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Old 18th Apr 2017, 08:25
  #1165 (permalink)  
 
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Pruneface - the whole point of SAR is giving the quickest response, regardless of international boundaries - how long do you think it would take to task a UK-based aircraft (probably from Caernafon) to fly across Ireland, refuel and then go to the FV compared to tasking the Sligo aircraft to something that might technically be outside their area?

The vessel may also have been steaming towards the mainland (this is normal to reduce the range) and could well have been estimated to be inside the Irish area by the time the rendevous happened.

That aside, the Irish area really should be expanded now they have better aircraft - they would never go more than 160 nm out with the S-61 but the S92 has a far better RoA.

Gouli - are you sure about your radar theory? The minimum distance for the radar on the Sea King was 75m which is why it was so good at coastal and vessel letdowns.
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Old 18th Apr 2017, 09:01
  #1166 (permalink)  
 
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Crab.
You got it spot on. IRCG would have been tasked by HMCG as being closest useable asset.
As for expanding the Irish SAR Region . . . thats mired in ancient politics best left out of this forum
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Old 18th Apr 2017, 09:28
  #1167 (permalink)  
 
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Originally Posted by [email protected] View Post
Gouli - are you sure about your radar theory? The minimum distance for the radar on the Sea King was 75m which is why it was so good at coastal and vessel letdowns.
The min range is about 0.1Nm (from my memory) in SEA mode. In ground mapping, ehhh, I'd say around 0.15. It is a bigger value in WX mode, that'll be aound the numbers given by Gouli.
Gouli, its a 10kW radar, with 8kW as nominal power.

For others, about the radar painted picture: the screen will only show where the radar pulse hit somethig. From low level towards a very steep high hill higer then your height the closest part painted on screen will be the first hit close to sea, and the furtest will be the upper part of lobe hitting higher on the slope further away.( a vertical steep will only paint a thin line).
From wikipedia pictures, they flew towards this small island short side, that is quite steep. Wiki say Blackrock measures 400m length and 200m width, thats 0.1nm wide. So the radar picture will show a very small width( seen in track perspective). The length it will paint is the steep's horizontal difference + the "beach". From pictures that looks like a maximum of half length, ie also about 200m or 0.1nm.
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Old 18th Apr 2017, 10:05
  #1168 (permalink)  
 
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Originally Posted by dClbydalpha View Post
Can any S92 operators tell me the size/colour of FMS WP symbols? Are they overlayed on top of the radar video?
That is a very valid question.

With the radar set to 10 NM range on the PM's (copilot) NAV screen in this case, the waypoint symbol for "BLKMO" would hide the radar return from Blackrock. If using 5 NM, or even better 2.5 NM range, the return from Blackrock would be relatively larger than the waypoint symbol, and hence get your attention.

I tried this a couple of days ago (in the S92 with the Primus 701A radar) using an oil rig as "Blackrock". With 10 NM range, GMAP2, optimal gain and tilt, and at a distance of 1-2 NM from the oil rig it was very difficult to actually spot the return because of the waypoint symbol. Blackrock might have given a slightly larger return than an oil rig though.
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Old 18th Apr 2017, 10:16
  #1169 (permalink)  
 
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I'm staggered at the number of posts about radar operation and differing views and understanding about it - it is obviously very complex. It therefore seems all the more extraordinary that a crew select an approach type (long transit at 200ft) that relies for safety on radar, which clearly has a lot of risks associated with its use (that they probably didn't fully realise), to rely on for obstacle avoidance. The route guidance the crew followed has been criticised heavily by some - but the chart itself did not include any vertical profile so was surely obviously not an IMC let down procedure. I guess the associated notes might include minimum heights, but it seems highly unlikely. So why did the crew choose to carry out the whole route at 200ft? Was it too much automatic default to the over sea APP1 coupled approach mode, without enough thinking?

Clearly this procedure has important uses for SAR, but by using it here the crew put themselves in a position of having to rely on a complex system - radar - with considerable risks to be safe.

Safety of course is all about risk minimisation and the risks of using a simple IMC let down, minimising distance at low height, relying on GPS waypoints, seem to be far less to me. Blacksod really doesn't look a tight, tricky location to get into. With the two GPS systems accuracy would be pretty much guaranteed, and it would have been easy to verify position using other tools such as RadAlt anyway. And all the benefits of radar and FLIR could also still used, but with far less risk of hitting anything if - as seems here - radar use is flawed.

Furthermore such an approach would take far less flight crew attention - frankly it could have been flown single pilot without problem.

So why did the crew apparently choose to blend the APP1 approach mode with this VFR inter lighthouse route guidance? Or maybe they didn't choose it - could it have been specified by the operator to do this? And they didn't question it?
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Old 18th Apr 2017, 11:00
  #1170 (permalink)  
 
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Theory and practise

Originally Posted by [email protected] View Post
Pruneface - the whole point of SAR is giving the quickest response, regardless of international boundaries - how long do you think it would take to task a UK-based aircraft (probably from Caernafon) to fly across Ireland, refuel and then go to the FV compared to tasking the Sligo aircraft to something that might technically be outside their area?

The vessel may also have been steaming towards the mainland (this is normal to reduce the range) and could well have been estimated to be inside the Irish area by the time the rendevous happened.

That aside, the Irish area really should be expanded now they have better aircraft - they would never go more than 160 nm out with the S-61 but the S92 has a far better RoA.

Gouli - are you sure about your radar theory? The minimum distance for the radar on the Sea King was 75m which is why it was so good at coastal and vessel letdowns.
I think what the officer means is "theoretical minimum range".
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Old 18th Apr 2017, 12:18
  #1171 (permalink)  
 
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Ai-Bert,

I raised this before in the thread well back in the many posts and repeated it again for reasons you understand.

The standards, method, curriculum, and time devoted to Initial and Currency Training is a very important issue that bears close study by the Investigators.

I was hoping those with first hand experience would offer some insight into the CHC/Irish Coast Guard. operation training program.

Crab and other SAR folks have expressed concerns back during the U.K. Transition to the current system..
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Old 18th Apr 2017, 12:38
  #1172 (permalink)  
 
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Gouli:
The radar transmitter is pumping out pulses of energy of up to 1,000 watts. The receiver is designed to respond to returning echo signals measured in micro watts, a millionth of a watt. Even if the transmit/receive protection circuits work in around a microsecond, you will see nothing within a 300 metre range. If they take three microseconds to switch over, you are blind to everything within a kilometre. We are talking millionths of a second here to switch from 1000 watts out to a few millionths of a watt coming back! The technology is well proven, but transmit/receive delays increase as equipment ages, so close in blind spots get bigger. A crew may actually perceive the radar equipment as working better as it ages because of an apparent reduction in close in sea clutter.
As an ex-SAR radar operator I've tried to stay out of this debate - I used to operate a search radar, not a weather radar, but the statement above was a step too far. Minimum Range (Rmin) is a function of pulse width, or pulse duration (interchangeable terms), caused by a pulse requiring time to be transmitted, hit something and return. For example, with a radar with a pulse duration of 1 microsecond the pulse leading edge can travel out for 0.5 microsecond (at the speed of light, and when the receiver is effectively 'blind'), hit something, and travel back to the radar in the following 0.5 microsecond. Using the equation, Rmin = C x PD/2, if C = 300,000,000 m/s (approx) then Rmin in this case is 150 m. As Crab says, the Sea King radar had an Rmin of 75m due to its PD of 0.5 microseconds.

There usually aren't any complex "transmit/receive protection circuits" in the manner suggested as they are usually simple isolators (with no moving parts) that allow microwave energy to pass in one direction but not the other. You are mixing up circuits within the receiver which are designed to prevent very large targets swamping smaller ones by raising the receiver Automatic Gain Control too high.


"Transmit/receive delays increase as equipment ages?" That's just wrong.


Finally, I never perceived the apparent lack of information on my radar screen as an indication it was "working better."


Last edited by sargs; 18th Apr 2017 at 13:21. Reason: Mixing my MURs with my MINs...
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Old 18th Apr 2017, 12:43
  #1173 (permalink)  
 
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crab

Radar operates at the speed of light, 300,000 kilometres per second, or 300 metres every millionth of a second. Modern electronic components have reduced the size and increased the power of radar systems, but there is a physical limit to how much functionality can be built into a single system. Low power motion detector systems can operate at ranges of a few feet, but a system capable of picking up targets at a range of 40 miles will have its' performance compromised at very close ranges due to the laws of physics. In order to obtain unhindered close range performance, the use of two identical physically coupled but electrically isolated scanning dishes would be required. The sheer size of such an antenna system would preclude fitting in most aircraft.

I am as certain as I can be that the crew did not see Black Rock on the radar display and that Black Rock was certainly not presented on the display or recognised as presenting imminent danger. I am also sure that such an experienced crew were lulled into a false sense of security by perhaps not appreciating the ultimate physical limits of the radar system due to weather and possibly a latent deterioration in system performance due to the ageing of components.

A flawed approach pattern, lack of detailed mapping information, radar returns that were "unreliable" at close range and a loss of situational awareness in dodgy weather all combined to create the circumstances for this tragedy to happen. The classic holes in the swiss cheese lining up analogy of many aviation accidents.

sargs

Yes, 75 metres is a theoretical minimum range with a half microsecond transmit/receive switchover. You are quite correct that quarter wave stubs of waveguide are used to provide almost perfect isolation between the transmit and receive sections and that no electronic components are necessary to provide this isolation, just careful design and adherence to mechanical tolerances. But radar waveguide alters in size due to temperature changes and/or mechanical damage when knocked so some part of the transmitter energy can end up being fed towards the receiver circuits as the transmit pulse is fired off. To cater for this, there is a very high speed schottky diode mounted across the waveguide of the receiver section designed to short out if receive signals exceed a small fraction of a volt. It is this component that ages and needs to be replaced at regular intervals. When I worked for Marconi, every radar engineer carried half a dozen replacements in their tool kit. It was standard practice to replace them on every visit for servicing or fault finding.

Last edited by G0ULI; 18th Apr 2017 at 16:35. Reason: Corrected 300,000,000 to 300,000!
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Old 18th Apr 2017, 12:55
  #1174 (permalink)  
 
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Gouli - I refer you to the post above yours by sargs regarding radar theory

If modern weather/search radars in helicopters are so difficult to setup and use accurately, why on earth is there not a dedicated and properly trained radar operator doing it in a modern SAR helicopter rather than a co-pilot (often the least experienced member of the crew) being given the task on top of all his other duties?

leopold - yes quite right as always
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Old 18th Apr 2017, 13:02
  #1175 (permalink)  
 
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crab

Modern radar systems are brilliant. Operation has been simplified with automatic optimisation to present the clearest possible display, but they are not infallible.
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Old 18th Apr 2017, 13:21
  #1176 (permalink)  
 
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Originally Posted by Pltnorway View Post
That is a very valid question.

With the radar set to 10 NM range on the PM's (copilot) NAV screen in this case, the waypoint symbol for "BLKMO" would hide the radar return from Blackrock. If using 5 NM, or even better 2.5 NM range, the return from Blackrock would be relatively larger than the waypoint symbol, and hence get your attention.

I tried this a couple of days ago (in the S92 with the Primus 701A radar) using an oil rig as "Blackrock". With 10 NM range, GMAP2, optimal gain and tilt, and at a distance of 1-2 NM from the oil rig it was very difficult to actually spot the return because of the waypoint symbol. Blackrock might have given a slightly larger return than an oil rig though.
To add another relevant part to the question - both the waypoint symbol and the strongest GMAP returns are magenta. It may well be that a particular range set up will result in the Blackrock return being somewhat masked by the waypoint symbol and labelling, and I'm sure the AAIU will replicate the conditions. More so, if the illumination levels are dimmed down to enhance night vision.

On that point, I feel that Al-berts' rather pejorative remarks about "children of the magenta line" are misplaced in this context. The expression usually refers to young pilots that have never known anything other than glass cockpits and automation - in this case both pilots had spent 20 odd years each flying S61s. Relative newcomers to the magenta line perhaps.....
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Old 18th Apr 2017, 13:34
  #1177 (permalink)  
 
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Gouli

When I worked for Marconi
That'll be the radar company that ceased operations 30 years ago?
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Old 18th Apr 2017, 13:38
  #1178 (permalink)  
 
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The Primus 701 is nearly 30 years old
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Old 18th Apr 2017, 13:42
  #1179 (permalink)  
 
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Proven technology?

Anything better on the market that could be installed in place of the current fit?
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Old 18th Apr 2017, 14:10
  #1180 (permalink)  
 
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Relative newcomers to the magenta line perhaps.....
I think that might be a very valid point in that after a couple of years of 'magenta' all those hard-won lessons on old technology get forgotten and reliance on the new and shiny kit becomes absolute.
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