AS332L2 Ditching off Shetland: 23rd August 2013
P2k4 - I am quite happy to be considered patronising, and lets face it, when you have a brain the size of a planet its hard not to be. But I really don't care what you think of me, my aim is to get a message across by whatever means. By the way, if you've read much of this thread you would realise that whilst the EC225 is all singing and dancing, the L2 is not. And this accident was ....... Oh yes, an L2. So patronise that!
But on a briefly more serious note, your point has been covered before in this thread. Of course manual flying skill retention can be an issue, but in this case, unless you consider skills were degraded to the point they had forgotten what the collective did, its not the issue. Mixing automation with manual flying possibly is.
But on a briefly more serious note, your point has been covered before in this thread. Of course manual flying skill retention can be an issue, but in this case, unless you consider skills were degraded to the point they had forgotten what the collective did, its not the issue. Mixing automation with manual flying possibly is.
HC
You have confused me now - surely an instrument approach is at low - medium speed yet it seems that the way pilots fly the approach is as if it were high speed.
Being a product of the RAF system I, like Crab was taught that cyclic controlled speed and that power via the collective controlled height. The scenario you put forward of cruising at max power didn't occur in most RAF operations as the helicopter was usually been aggresively flown at low level - 50ft in German Ex areas and 100ft elsewhere
HF
You have confused me now - surely an instrument approach is at low - medium speed yet it seems that the way pilots fly the approach is as if it were high speed.
Being a product of the RAF system I, like Crab was taught that cyclic controlled speed and that power via the collective controlled height. The scenario you put forward of cruising at max power didn't occur in most RAF operations as the helicopter was usually been aggresively flown at low level - 50ft in German Ex areas and 100ft elsewhere
HF
Low, medium and high are relative terms. In my context I was using them to mean pretty much hovering, around Vy, and significantly above Vy. We don't know what the nominated approach speed was but lets say 110kts, I would say that was "high speed" in this context, although I will give you that its only just so, or even in the grey zone in between.
Power determines both height and speed as there are any number of combinations one can get for a particular power setting.
Examples....Full RPM....flat Pitch...minimum power...Zero airspeed....either sat on the helipad or in autorotation with Vne on the clock.
MCP....Max attainable height....low speed.....50 feet AGL...high speed.
MCP...2000 feet.....some speed....to go faster....nose down....but lower altitude for the new speed.....slow down to original speed (nose up) more height.
So I say all you CFS guys are wrong.....it is Power that matters and what you do with it.
Cyclic controls the pitch and roll attitude of the aircraft, Collective controls Power.
In Hover....Collective controls Power which determines Height.
In Forward flight....Collective controls power which provides Speed/Height.
Examples....Full RPM....flat Pitch...minimum power...Zero airspeed....either sat on the helipad or in autorotation with Vne on the clock.
MCP....Max attainable height....low speed.....50 feet AGL...high speed.
MCP...2000 feet.....some speed....to go faster....nose down....but lower altitude for the new speed.....slow down to original speed (nose up) more height.
So I say all you CFS guys are wrong.....it is Power that matters and what you do with it.
Cyclic controls the pitch and roll attitude of the aircraft, Collective controls Power.
In Hover....Collective controls Power which determines Height.
In Forward flight....Collective controls power which provides Speed/Height.
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Surely all the extensive discussion on autopilot type and modes selected is secondary here?
This sort of approach is presumably fairly routine in the NS and shouldn't have caused any problems. Autopilot coupled on LOC and VS, pilot sets collective to achieve target AS, adjusts if necessary. Both pilots focused on critical part of flight, standard scan focuses on airspeed, altitude and radalt, as MDH is approached monitoring reaches max, a go around ready to be implemented if necessary. Not complicated, surely? Workload is reduced with the LOC and VS coupling.
Events going wrong didn't happen quickly here either - the airspeed was gradually decaying over 60 seconds or so - plenty of time to see things going awry with decaying AS and heights too low. And it wasn't as if they hit high terrain from loss of situational awareness (eg Mull of Kintyre). The crew knew it was flat sea between them and the airfield and that their critical input was to monitor height and go around if required.
When more information is revealed it will also be interesting to see what happened in the final 200ft or so, when presumably the crew became visual. Did they pull max Tq and try to recover? Or was local vis too bad to properly get visual before hitting the sea was unavoidable. The crew will certainly know.
And yet despite not just one but two experienced crew, this basic monitoring appears not to have happened. Again it is hard to think they simply were not paying attention for such a long time. Could they have been incapacitated somehow? Unlikely, especially both, again. Did each pilot wrongly assume the other knew what he was doing?
And why did the airspeed drop off so much in the first place? Could that have been from something as simple as collective friction not having been set at the top of the descent and it edged down un-noticed? (Never flown SP so no idea if relevant) Of course monitoring and reacting is still the critical bit.
Was there a major distraction? Warning lights? Fire? Passenger interference?
Quite a conundrum.
This sort of approach is presumably fairly routine in the NS and shouldn't have caused any problems. Autopilot coupled on LOC and VS, pilot sets collective to achieve target AS, adjusts if necessary. Both pilots focused on critical part of flight, standard scan focuses on airspeed, altitude and radalt, as MDH is approached monitoring reaches max, a go around ready to be implemented if necessary. Not complicated, surely? Workload is reduced with the LOC and VS coupling.
Events going wrong didn't happen quickly here either - the airspeed was gradually decaying over 60 seconds or so - plenty of time to see things going awry with decaying AS and heights too low. And it wasn't as if they hit high terrain from loss of situational awareness (eg Mull of Kintyre). The crew knew it was flat sea between them and the airfield and that their critical input was to monitor height and go around if required.
When more information is revealed it will also be interesting to see what happened in the final 200ft or so, when presumably the crew became visual. Did they pull max Tq and try to recover? Or was local vis too bad to properly get visual before hitting the sea was unavoidable. The crew will certainly know.
And yet despite not just one but two experienced crew, this basic monitoring appears not to have happened. Again it is hard to think they simply were not paying attention for such a long time. Could they have been incapacitated somehow? Unlikely, especially both, again. Did each pilot wrongly assume the other knew what he was doing?
And why did the airspeed drop off so much in the first place? Could that have been from something as simple as collective friction not having been set at the top of the descent and it edged down un-noticed? (Never flown SP so no idea if relevant) Of course monitoring and reacting is still the critical bit.
Was there a major distraction? Warning lights? Fire? Passenger interference?
Quite a conundrum.
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HC, if you were flying that approach completely manually, at 110kts, which control would you use to adjust/maintain IAS, and which control would you use to adjust/maintain your "glidepath"?
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A number of posters are clearly confused when they hear that, in the L2, cyclic controls altitude or vertical speed.
In most helicopters, collective controls those two parameters, and cyclic controls speed and direction. However, in the 50s and 60s, the French broke away from this tradition. In their helicopters, they decided it would be better to fly at a fixed collective pitch, and fly the ac like a fixed wing. (And, at the same time, they decided to make their rotors go around in the opposite direction to everyone else!)
So their AFCS systems are optimised with different rules to 'most' helicopters, with the vertical channel being controlled by cyclic.
It's not wrong, it's just different. Pilots become used to it very quickly, and think it normal. But it can confuse those not au fait with ze French way.
In most helicopters, collective controls those two parameters, and cyclic controls speed and direction. However, in the 50s and 60s, the French broke away from this tradition. In their helicopters, they decided it would be better to fly at a fixed collective pitch, and fly the ac like a fixed wing. (And, at the same time, they decided to make their rotors go around in the opposite direction to everyone else!)
So their AFCS systems are optimised with different rules to 'most' helicopters, with the vertical channel being controlled by cyclic.
It's not wrong, it's just different. Pilots become used to it very quickly, and think it normal. But it can confuse those not au fait with ze French way.
OF many moons ago I used to fly the 332L - manually -EEEK! Nominated approach speed for an ILS was 110kts normally. At that speed, presuming the collective was set to the correct ballpark figure, it was by far the easiest to fly the glide slope on the cyclic. Minor adjustments to attitude would of course give slight speed variations, but within limits. If there was severe up or down drafts then some collective action might be required to contain the speed.
When I became an instructor, I found guys fresh out of flight school really struggled with ILSs because they were trying to control glideslope with collective and speed with cyclic. On many helicopters, and especially the 332L, you get a lot of interaction in pitch and roll when the collective is moved, and this was destabilising their flying. Once I had beaten the duff gen they had been given at flight school out of their heads, and got them to fly glideslope mostly on the cyclic, they suddenly found it easy.
However, as SAS correctly pointed out a moment ago, in reality a combination of cyclic and collective is required to control both glideslope and speed in these sorts of speed ranges. Its a sliding scale from (eg height) all collective at zero speed, to no collective at Vh, and vice versa for cyclic. And the same but in reverse for speed. I just wish ab initio flight schools explained this properly.
When I became an instructor, I found guys fresh out of flight school really struggled with ILSs because they were trying to control glideslope with collective and speed with cyclic. On many helicopters, and especially the 332L, you get a lot of interaction in pitch and roll when the collective is moved, and this was destabilising their flying. Once I had beaten the duff gen they had been given at flight school out of their heads, and got them to fly glideslope mostly on the cyclic, they suddenly found it easy.
However, as SAS correctly pointed out a moment ago, in reality a combination of cyclic and collective is required to control both glideslope and speed in these sorts of speed ranges. Its a sliding scale from (eg height) all collective at zero speed, to no collective at Vh, and vice versa for cyclic. And the same but in reverse for speed. I just wish ab initio flight schools explained this properly.
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Exactly KG86, at speed the L2 behaves like a fixed-wing, and should be flown like that. If you want to make a small altitude correction in cruise, you do not need to touch the collective at all.
You can even keep your feet on the floor and make perfectly coordinated turns without any upper modes engaged.
Great machine, and I hear the 225 is even better.
You can even keep your feet on the floor and make perfectly coordinated turns without any upper modes engaged.
Great machine, and I hear the 225 is even better.
Last edited by Jimmy 16; 6th Sep 2013 at 13:41.
I find it interesting that it is considered "just an NPA". In the fixed wing world, almost all CFITs occur on NPAs, with something like 70-80% with the Captain as PF. There are a few very thought provoking diagrams of CFIT type accidents here:
NPAs without any form of vertical guidance are a bigger danger than an ILS and many companies require extra briefings and precautions for them. The large number of beautifully stable approaches on centreline smacking in short of the runway keeps my eyes firmly open.
Do you get any aural EGPWS type warnings when approaching minima for instrument approaches in the L2?
NPAs without any form of vertical guidance are a bigger danger than an ILS and many companies require extra briefings and precautions for them. The large number of beautifully stable approaches on centreline smacking in short of the runway keeps my eyes firmly open.
Do you get any aural EGPWS type warnings when approaching minima for instrument approaches in the L2?
jwscud, interesting statistics. I suppose its because we consider offshore airborne radar approaches and night offshore landing so much more difficult, that we consider NPAs to be "safe". The L2 doesn't have EGPWS but it does have an aural warning of "check height" when you go below the height bugged on the radalt, and also "100 feet" when you go below 100' radalt. I'm not familiar with CHC policy on setting the bugs, but in Bristow we set the bugs 100' below MDH. We don't really want a "check height" interrupting at the critical moment when crews are calling "decide", "I have control", "go-around" etc.
In this case, that would give a warning at 200' and at 100'. The former is suspendable, but Bristow SOP is to only do that when the necessary visual references have been acquired. The latter is not suspendable, although its inhibited for RoD >5000'/min.
However, taking into account reaction time and the high rates of descent at low airspeeds we suspect, there might be insufficient time to recover, certainly from 100' and possibly from 200'
In this case, that would give a warning at 200' and at 100'. The former is suspendable, but Bristow SOP is to only do that when the necessary visual references have been acquired. The latter is not suspendable, although its inhibited for RoD >5000'/min.
However, taking into account reaction time and the high rates of descent at low airspeeds we suspect, there might be insufficient time to recover, certainly from 100' and possibly from 200'
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Do you get any aural EGPWS type warnings when approaching minima for
instrument approaches in the L2?
instrument approaches in the L2?
- CHECK HEIGHT
The message is transmitted twice, with a four-second interval, when the aircraft reaches the DH/A or MDA displayed on the NMD or PFD. An AVAD push-button on the cyclic stick can be pressed to cancel the message for three minutes.
- ONE HUNDRED FEET
The message is transmitted once as soon as the aircraft passes into the altitude zone 100 feet Rad alt.
Last edited by Jimmy 16; 6th Sep 2013 at 14:14.
The "AVAD 100 Feet Warning" is not suspendable, although its inhibited for RoD >5000'/min.
EGPWS gives you a different way of doing it - it will automatically call something like PLUS HUNDRED and then MINIMUMS (depending on customer option) based on the Baro DA set by the crew. You then call Land/Go Around in response to the EGPWS call.
Not I agree entirely relevant to the scenario we're discussing - I'm just interested in how you guys operate.
Do you have clearly defined SOPs for calling deviations? The following examples for final approach come straight from my FCOM:
Flightpath deviations:
• “___ DOTS(S) FLY LEFT / RIGHT”
• “___ DOT(S) FLY UP / DOWN”
• “SPEED” (Whenever IAS is less than Vref or greater than Vapp + 10 kt or
when the speed trend shows a significant tendency to exceed either of
these parameters and thrust lever position is inappropriate for the phase of
flight.)
• “VERTICAL SPEED” (Less than 300 fpm or greater than 1000 fpm in the
last 1000 feet AGL).
The "speed" call gives you 15 knots range of speed (Vref is the minimum, Vapp normally Vref+5) before it is called to your attention.
Not I agree entirely relevant to the scenario we're discussing - I'm just interested in how you guys operate.
Do you have clearly defined SOPs for calling deviations? The following examples for final approach come straight from my FCOM:
Flightpath deviations:
• “___ DOTS(S) FLY LEFT / RIGHT”
• “___ DOT(S) FLY UP / DOWN”
• “SPEED” (Whenever IAS is less than Vref or greater than Vapp + 10 kt or
when the speed trend shows a significant tendency to exceed either of
these parameters and thrust lever position is inappropriate for the phase of
flight.)
• “VERTICAL SPEED” (Less than 300 fpm or greater than 1000 fpm in the
last 1000 feet AGL).
The "speed" call gives you 15 knots range of speed (Vref is the minimum, Vapp normally Vref+5) before it is called to your attention.
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@SAS:
Yes, the French have a policy of not distracting pilots with things they do not need to know about......
Yes, the French have a policy of not distracting pilots with things they do not need to know about......
Last edited by Jimmy 16; 6th Sep 2013 at 14:17.
HC
RAF basic training is done on a fixed wing, this gives you a base line of experience and airmanship. You also fly the a/c to the limits of its envelope so you develop a healthy respect for limits.
My "basic" helicopter flying was done on the Whirlwind 10 a single turbine which was very basic, and it didn't have an autopilot. On this a/c you certainly learnt about limited power!
The basic model of power/collective controls height always works until a power limit is reached - then cyclic can be used to zoom climb or increase airspeed to descend. Every RAF pilot knows this and while flying nap of the earth a mixture of height control was used depending on power settings.
To get back to the accident. The weather at Sumburgh was right on limits.
METAR COR EGPB 231750Z 14019KT 2800 BR SCT002 BKN003 15/14
Q1013 NOSIG=
METAR COR EGPB 231720Z 14017KT 2800 BR SCT002 BKN003 15/14
Q1013 BECMG 4000 BR BKN006=
The MDH for the LOC/DME approach is 300ft QNH so the crew would be very aware that they had to fly an accurate approach. In this case I would aim to arrive at the MDH just short of the MAP so I could level, stabilise and hopefully see the lights/ runway as I approached the coast.
HF
Mmmh, so your basic training was limited to expected future roles and types. Not very basic then!
My "basic" helicopter flying was done on the Whirlwind 10 a single turbine which was very basic, and it didn't have an autopilot. On this a/c you certainly learnt about limited power!
The basic model of power/collective controls height always works until a power limit is reached - then cyclic can be used to zoom climb or increase airspeed to descend. Every RAF pilot knows this and while flying nap of the earth a mixture of height control was used depending on power settings.
To get back to the accident. The weather at Sumburgh was right on limits.
METAR COR EGPB 231750Z 14019KT 2800 BR SCT002 BKN003 15/14
Q1013 NOSIG=
METAR COR EGPB 231720Z 14017KT 2800 BR SCT002 BKN003 15/14
Q1013 BECMG 4000 BR BKN006=
The MDH for the LOC/DME approach is 300ft QNH so the crew would be very aware that they had to fly an accurate approach. In this case I would aim to arrive at the MDH just short of the MAP so I could level, stabilise and hopefully see the lights/ runway as I approached the coast.
HF
No point, too late by then. Anyway, in case you didn't know, the >5000'/min inhibit is to try to stop the "100'" sounding every time you cross the deck edge landing offshore. It works most of the time.
the >5000'/min inhibit is to try to stop the "100'" sounding every time you cross the deck edge landing offshore. It works most of the time.
Last edited by SASless; 6th Sep 2013 at 15:56.
In most helicopters, collective controls those two parameters, and cyclic controls speed and direction. However, in the 50s and 60s, the French broke away from this tradition. In their helicopters, they decided it would be better to fly at a fixed collective pitch, and fly the ac like a fixed wing. (And, at the same time, they decided to make their rotors go around in the opposite direction to everyone else!)
So their AFCS systems are optimised with different rules to 'most' helicopters, with the vertical channel being controlled by cyclic.
So their AFCS systems are optimised with different rules to 'most' helicopters, with the vertical channel being controlled by cyclic.
All helicopters, regardless of origin, with 3-axis autopilots fly using cyclic to control the vertical mode when it's engaged (and IAS when it's engaged). How else could they, with no collective coupling? That's why you can't have both IAS and a vertical mode engaged simultaneously on 3-axis machines.
Last edited by 212man; 6th Sep 2013 at 16:54.
Therein lies my point 212man - the autopilot modes were designed around what was possible at the time (clearly collective coupling wasn't) but most pilots are taught to fly on a non-autopilot machines.
Is it not therefore surprising that, under pressure, one reverts to what one was first taught (and had beaten into you - attitude= speed and lever = height) not what one has subsequently learned?
Is it not therefore surprising that, under pressure, one reverts to what one was first taught (and had beaten into you - attitude= speed and lever = height) not what one has subsequently learned?