Helijet S-76C Loss of Control November 2015

[zalt]

BC operator Helijet had a nasty incident last November with one of their four HEMS S-76C.

Shortly after uncoupling the AP at 600ft on night-time finals the crew got into a high rate of decent (between 1100fpm and 2500fpm, depending on who you believe) and allegedly lost so much NR that the generators went off-line. They did however manage to recover but the casualty they were flying to pick up had to wait for a fixed wing transfer the next day.

More details here. (http://aerossurance.com/helicopters/hems-s76-night-approach-loci/)

The paramedics union are fairly grumpy about it.

[Sevarg]

The generators (DC) are driven by the engines not the rotor, the AC genny is driven from the MGB but there is only one of them, so I take it they mean the AC generator. Old age has taken away the memory of the Nr that it it drops off line at, sorry.

[eivissa]

The AC Generator drops out if the NR falls below 93%.

[zalt]

Thanks. Sorry for being imprecise. Its been a few years since I had anything to do with an S-76!

[Nigel Osborn]

When the AC drops off, doesn't the invertor take over?

[zalt]

Forgive me but the generator status is surely the least interesting matter.

A RoD of between 1100fpm and 2500fpm when uncoupling the AP at 600ft and over torqueing the drive train in the process seem more significant to me.

[Random Old Guy]

I doubt the 2 paramedics on board cared much whether it when out at 92% or 93%
They where to upset to continue even doing there job. The patient sure did not care. They had to stay alive until a fixed wing with more paramedics could come to get them.
The issue is how could this happen, then on a go around, happen again.
Then two days later, when everyone has settled down and the aircraft is "fixed" it starts off on another medivac and returns before take of because of a bad vibration, which ultimately saw the transmission and gear box changed.
The company said the fire the 2 pilots.

[squib66]

Of course it wasn't "fixed" first time. Wonder why.

[gulliBell]

A single operative inverter can power all the AC buses, except for the monitor bus. Only the AC generator can power the monitor bus. The AC generator will only power the AC buses if both inverters are off-line. The AC generator automatically drops off-line when the engine-out logic is tripped, as determined by N1 and ECL position. NR is not used in the logic to determine engine-out status. In an emergency if you droop NR below 92% with both engines operative the AC generator should still drop off line.

[RyRy]

Sounds like they got into VRS... at night and on final to what was essentially a black hole with a ring of flares.

Can't imagine a more terrifying situation. Glad no one was hurt.

[Outwest]

at night and on final to what was essentially a black hole with a ring of flares.

The report says they were on final to the Tofino airport (runway), is that not true?

[RyRy]

Yeah, but to my knowledge it's unlit and the staff set out a flare ring. I could be wrong.

[CG4A]

Correct. RNAV 29 in Tofino, completely unlit. O Dark 30 medevac, very high ground to the east, black hole approach. Sounds like a lot of no fun.

[gulliBell]

My thinking with these approaches: there is no need to decouple the AP at DH/MDA once visual, even if you have to subsequently manoeuvre for a circling approach to land. With a stable approach established on the final segment the AP will keep you stable and going down to the runway, just maintain IAS minimum for coupling (what is it, 50 knots?). When pilots decouple too early from a stable approach and then move the controls is when things are at risk of getting unstable.

At 600' the search light provides adequate illumination to see the ground ahead of you. Passing 50' decouple, trim 10 degrees nose up, the airspeed and sink rate will reduce, run it on at 20 knots using a touch of collective at the bottom to cushion it on. There is no need to move the controls at all, just trim! With 5000' of runway ahead of you there is no need to slow down too early and risk getting yourself in a sticky situation. Anyway, this is the technique I teach, maybe there are other safe ways to do it. But the important thing is to use the resources available, maintain safe airspeed to be assured of reaching the runway, and monitor the sink rate. You will not get into settling with power if you keep 30+ knots airspeed, however be mindful that you can quickly slow below 30 knots and get into strife close to the ground if somebody is not closely watching the parameters.

These are my thoughts, for what they're worth.

[Turkeyslapper]

Are nvg used in this part of the world? Great sa tool off the bottom of an approach and in this case may have been a huge help?

[RyRy]

NVGs are an option.... should the government decide to pay for them, as its a provincial contract.

[Perro Rojo]

Gullible, It appears that 29 was unlit so that means no landings on the runway. Have to land at the "flare ring" laid out for them.

Does anyone know where the flare ring was laid out? Was it on the runway or was it on the ramp?

[malabo]

I question the decision (pilot or operator or CAA) to do a black hole approach to a blacked out airport when according to my dog-eared VFR Flight Supplement the hospital has a perfectly good helipad with good approaches, floodlit ambiance, lead-in lights, pad perimeter lights, lit windsock, and the ambient cultural lighting of the entire town surrounding it.

I've seen that stupidity in Africa where you would ignore the huge floodlit ramp area by the hangars to go land 1/2 mile away on a pitch black runway lit with some feeble dying pot lights, thought Canada was smarter.

[RyRy]

I believe the Tofino Hostpial pad is day VFR only nowadays.

[Rotorhead77]

Tofino pad is closed permanently! Airport is the only option.

[Turkeyslapper]

"NVGs are an option.... should the government decide to pay for them, as its a provincial contract"


No NVGs but under the provincial contract approaches to flame rings at blacked out airports are ok??? I must be missing something but that sounds ludicrous??

[gulliBell]

If ground support was in attendance why can't they just do a runway inspection, lay the flares down the edge of the runway, and use the aircraft controllable search light to supplement the ground illumination? Much safer than getting succoured into a black hole approach. Unless the local operating rules dictate otherwise?

The power train replacement must have cost at least $1 million USD. Much cheaper me thinks just to lay the flares down the edge of the runway and execute a normal runway landing. To me it's just crazy landing into a flare circle when you have a 5000' runway that might otherwise be available.

[Hot and Hi]

Here is the full investigation report Aviation Investigation Report A15P0217 - Transportation Safety Board of Canada (http://www.bst-tsb.gc.ca/eng/rapports-reports/aviation/2015/a15p0217/a15p0217.asp)

The first 40 pages is good reading, then it becomes a bit repetitive: Unfortunately, the final analysis chapter is a mere repetition of the facts established upfront. No real judgement passed.

How could the incident happen? Two ATP's, two engines, autopilot, IFR ratings, thousands of hours each. The biggest single problem the report highlights is the low crew gradient: Professional curtesy prevents scrutiny. Or rather, each pilot may have thought the other pilot should well be able to do the job on his own. Right they were. What one would expect a PPL holder to get right: speed, sink rate, attitude.

But if it can happen do the best, if might happen to any of us. As such it serves as a good learning.

[gulliBell]

...How could the incident happen? Two ATP's, two engines, autopilot, IFR ratings, thousands of hours each..

Don't be surprised, I've seen it happen many many times in the simulator. One pilot sits on his hands and says nothing as the other pilot flies both of them into the ground. ATP, CPL, high experience, low experience, makes no difference, the behavior and outcome is the same.

I'm a bit rusty on S76C+ as I haven't flown one in about 20 years, but some of my reading of the report thus far doesn't gel with my vague memory...about blowaway power (para 1.6.3.1)...I thought the most the DECU would give you under blowaway logic is 115% TQ...the report says if NR drops below 90% the DECU will give you 140% TQ, really?? And (para 1.6.4.1) "..The system is designed to limit fuel flow when either the all-engines-operating torque limit or the temperature limit is reached..." Doesn't the DECU only look at T5 for engine starting?...the DECU limits fuel flow to maintain T5 limit during blowaway logic event, really? Maybe I'm setting myself up to look stupid here, and I don't have any manuals at hand to look up the answers for myself, so if any S76 gurus out there could enlighten me on these aspects, thanks.

[gulliBell]

Decu does not control engine starts ..actually I know of no helicopter that does that.

Of course the DECU controls engine starts...it is the box that sends the control signals to the stepper motor that is attached to the AFCU that regulates engine fuel flow during start, operation, and shutdown.

[Flapwing]

the full 72 page report

[albatross]

Sorry about my post..my error...I was refering to still monitoring to ensure no overtemp..just very badly worded...I will go stand in the corner with my dunce cap firmly in place.
I think I was having a 76A, A+ or ++ moment.

[casper64]

NVGs are an option.... should the government decide to pay for them, as its a provincial contract.

Sad that it's just an "option"... should be mandatory if you ask me.... It would have prevented everything!

[gulliBell]

Some might say, monitoring the sink rate and other performance parameters with the Mk1 eye ball and call any deviations during the approach would also have prevented everything. For sure NVG would have given them better visual clues that they were flying backwards/sideways at the bottom of the approach.

[Longdog]

Helijet & B.C. Ambulance Service to install Night Vison Imaging Technology on Air Ambulance Aelicopters - Helijet.com (http://helijet.com/helijet-b-c-ambulance-service-install-night-vison-imaging-technology-air-ambulance-aelicopters/)
It took a while, and almost the loss of life, but the government has seen the light.

[the coyote]

If you fly a black hole approach without absolute attention to the numbers then you are simply asking for trouble. In my view it is 10% eyeball and 90% instrument. Plot a distance to run/altitude scale and set up a constant GS/ROD to match and it should fall into place with minor corrections. Those that fly it all eyeball will get disorientated.

[Sir Korsky]

the Universal FMS has the VNAV function. You can't couple, but you set the ROD and you'll get SA guidance to any fix your choice. We'd use it a lot going into black holes.

[gulliBell]

Don't they have a nightsun to light up the landing area like a Christmas tree? If not, the pilot controllable searchlight on a S76 provides reasonable ground illumination below about 300'. Certainly enough light to provide visual reference at the bottom of an approach. When you are close to the ground the pilot has to be looking outside...

[Longdog]

Helijet receives heaviest aviation fines from Transport Canada in B.C. | Vancouver Sun (http://vancouversun.com/news/local-news/helijet-receives-heaviest-aviation-fines-from-transport-canada-in-b-c)
Just published.