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.

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.

Hi SAS, I'm waiting for a reply to this one too! :hmm:

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.

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.

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

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.

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.

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?

Theory and practise
 

I think what the officer means is "theoretical minimum range".

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..

Gouli:
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."

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.

Gouli - I refer you to the post above yours by sargs regarding radar theory:ok:

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:)

crab

Modern radar systems are brilliant. Operation has been simplified with automatic optimisation to present the clearest possible display, but they are not infallible.

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.....

Gouli

That'll be the radar company that ceased operations 30 years ago? :hmm:

The Primus 701 is nearly 30 years old

Proven technology?

Anything better on the market that could be installed in place of the current fit?

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.

G0ULI - you are polluting this thread with misinformation and utterly erroneous conjecture based on experience that has got absolutely nothing to do with the subject in hand.

:ugh:

Which is why you need to switch off all the fancy stuff, once in a while and do it old style. Not a popular view in H&S dominated industries like aviation, but it helps to appreciate what the fancy bits can and cannot do for you. Ue it when you must, but when you train it has got to come off every now and again.

With regard to using the radar for ground mapping: I never trust the thing to show me what I need to see, so I constantly select short to medium ranges, adjust gain, tilt and mode just to make sure I don't miss anything that might harm us. Low level below MSA, especially at night/in poor visibility is a dangerous place to be. Changing scales and modes also helps in showing something hidden under a waypoint marker. Never take anything for granted ..

The Dublin helicopter was 140 nm from the refuelling site at Blacksod. Caernarfon was 70 nm further away. So the answer to your question is that the extra travel time involved would have been approx 30 minutes.

My point is not about taking Sligo out of the picture. I can see why Sligo would have been tasked, even if HMCG was the principal mover.

Having flown pre, post, and during the magenta revolution and experienced the full spectrum of technology across approx four decades worth of aircraft innovation I believe it is overly-simplistic just to blame the technology (and over-reliance on it). Crews have been routinely flying serviceable aircraft into the ground since aviation began.

The reasons vary and causes range from straightforward to vastly complex. Wherever there is human decision-making involved in a system (of any kind) there will be accidents. James Reason's 'Swiss-cheese' model is an eye-catching representation of the way that a combination of errors conspire to cause tragedy. Even this though is a simplistic view; the investigators on this one will have a hell of a job exposing all the relevant factors, and their complicated relationships, that caused this tragedy.

Those that shout "more training" and "less automation" may feel better but the picture is vastly more complicated than that. Learning from accidents like this will no doubt help safety culture to evolve but, in my opinion, the human element combined with the limits of current technology will continue to conspire and result in accidents.

I admired Bristow's optimism with their recent 'Target Zero' safety program and statement that they genuinely believe that accident rates can be reduced to zero. I'm not so sure.

Thanks, my beer mat calculations had Blackrock as sub tending 900m at a couple of miles (including antenna beamwidth). At 10 nm display across, then each pixel would be about 50m and so 18 pixels. Symbols are often between 16 and 32 pixels. My concern was that if a symbol was coincident with the return then it might not have been as compelling an indication as it should. Particularly if not being looked for. All built on assumptions of what display ranges were selected so just wild conjecture. Thanks for the answer.

For those calculating radar MDR remember it is not just PW but also the Receiver Recovery Time that has to be used in the calculation.

FC80

The aircraft flew into a rock that clearly was not visible or obvious to the crew on the radar display. I (and others) have proposed several reasons how and why this could happen.

It is indeed a long time since I was a hands on radar engineer but the physics hasn't changed since then, only the equipment has got smaller and lighter.

How do you know the island was not visible on radar? Much more likely that they could see it. Perhaps thought the route they were flying was some sort of safe low level route.

Transcript from the CVR suggests that they were not aware of their position in relation to Black Rock. If it had been clearly visible on the radar, someone would have commented on it. It was the FLIR operator that alerted the pilot to the presence of something ahead.

This crew were betrayed by a combination of factors with inadequate navigational data and a failure of the radar to highlight the presence of Black Rock immediately ahead for some reason being primary factors.

They inputted BLKMO into the FMS. BLKMO is Black Rock.

I dunno, ...
 

All the years I did this (70's and 80's) we would NEVER overfly a target at 200' IMC. Think of a rig with a couple of workboats steaming around or a group of ships moving in different directions. If you were cheating a bit (not that I ever did) when you got inside 1/2 mile you offset the target 10 degrees so that if you didn't get visual at least you wouldn't hit the darn thing.

Tezzer. They loaded the APBSS approach (well, flight plan really) which included BLKMO as it's first waypoint. They clearly did not know that BLKMO was Blackrock and that Blackrock was a 300ft tall lump of rock. Part of that was their fault for not reading the notes to the plate and the captions on the plate, but a large share of the issue rests with the operator for not making clear what this chart and approach was designed for, and more importantly what it was not designed for.

O'leary. What's becoming clear is that BLKMO didn't appear as a target (which they would have avoided), it most likely appeared as a caption for BLKMO (which they were aiming for) which happened to be obscuring the target.

Gouli,

"One point three err miles to run to eh blackmo…
and after that its bravo kilo sierra delta alpha..."

Would indicate that the PM knew where they were - what they clearly were not aware of was the vertical extent of the island or they would not have been at 200 ft asl.

I'm guessing there have been numerous 92 SAR crews around the bazaars (UK, Eire, Canada, US, Australia and Brunei) using their training sorties to fly towards small islands and trying to replicate situations where they can't see them on radar! If not, might be an idea!

I suppose, but ...
 

I considered that possibility. The radar we used was primitive and had a simple black/orange display but even with sea or ice clutter we could still clearly define shoreline and islands. The only thing I can think is that somehow they had their MFDs set up incorrectly - but how would that be possible given the experience level of the crew?

Assumptions? Didn't the preliminary report state that the PF requested the PM to select 10 NM range?

Yes, it is, as it turns out. That does not mean the crew were aware that it was a waypoint that was located with a rock sticking 300 feet out of the ocean. They very clearly were not.

In answer to a question posed by Rotorspeed about why they would select an APP1 mode for descent, and whether that was imposed by the operator, it would be helpful to have 5 more minutes of the CVR before what is in the report.

I think the report makes it clear that the APBSS diagram was being used. It is not clear if the waypoints in that diagram are structured into a selectable approach in the FMS. If they are, then that supports a view that this is "imposed by the operator". The next question is if the operator imposes it as an IFR approach. If that is so, it is clearly inadequate, lacking vertical guidance.

There are a couple of features of this diagram that have the potential for the crew being led into the danger of presuming it is an IFR procedure for IMC conditions. The first is the lighter blue shading on either side of the leg lines. That shading only appears over water, except at BLCKMO. It does not appear over any terrain, or so it appears. I expect most would think it indicates an obstacle free safe space. Which it does. Even at 200 feet. Except for Blackrock, or over land around Blacksod.

The second feature is that it cannot be flown visually, although it obviously can be flown VFR. However to go from waypoint to waypoint, the flight must utilize instrumentation in the cockpit. Other than the helipads/lights, the other waypoints cannot be identified visually.

So the waypoints must be in the nav databases of helicopters which use this route. That would have to include the helicopters which use it for its primary purpose, transiting between Blacksod and Blackrock. Those aren't S-92s. But they are helicopters. We know an Air Corps machine was used to place the investigators there. So some other operator has a version of that diagram, and somehow CHC has it in its route guide. Legacy procedure seems reasonable.

It seems this crew has little to no local knowledge. That fact alone, and the availability of APBSS in the aircraft, underly this accident to a considerable degree.

Great discussion on radar. One thing from the CVR that stands out is that the crew operated on an assumption about the environment they were in. They were wrong to believe 200 feet was a safe altitude. When Capt. Duffy says something large to the right, it is obvious that assumption is challenged and that 200 feet, where they are and at 75 knots, may be/was a dangerous place to be and that a climb to MSA was a priority, followed by a different lookdown with the radar. Radar guys, they will see the picture then, or no? SAR pilots, yes or no on the immediate climb?

I would be interested on hearing how synthetic vision gear may have avoided this. Is it true that like EGPWS, if Blackrock isn't in the database, same problem?

If the purpose of the preliminary report is to immediately advise other operators and aircrew of issues, I think another five minutes of immediately preceeding CVR would be very enlightening for that purpose.

Exactly Llamaman - the 'kit' has become vastly more complex yet training hours are reduced and, the task remains the same. Has there ever been a job that this new kit has made possible compared to what we had before - I doubt it somehow!

Simple fix for the future?

Lose leg 1 from the diagram. Make BKSDA the IAF. Procedure turn right at MSA and descending after IAF to 2000. Balance unchanged other than putting in crossing altitudes for the next waypoints, MDA in the last leg, and a missed procedure. Draft a proper chart.

Don't make all the crossing altitudes after BKSDA at 200 feet. Same question arises, why spend more time down that low than necessary.

On APBSS, what are those red circles with numbers in them?

Amen to that ! Let's hope they setup a waypoint on top of the island and post something on here so we can see the challenges faced by this crew.

cnpc. The assumption is that they refer to notes in the supporting pages. And I don't think the operator should be in the market for simple fixes. They should either publish approaches that are fit for purpose or not publish approaches at all and rely on the SAR training and alleviations to allow crews to find the safest approach.