The big picture
A good friend of mine once asked me how I manage flying in ice and if we had an out if anything went wrong. He’s a highly experienced instrument flight rules (IFR) captain flying EMS in the US, and although he doesn’t know it, he’s already answered his own question.
We all know that successful IFR requires significantly more knowledge, planning and risk management than flying visual flight rules (VFR) does. At some point, we’ve all lost our alternate while en route when the weather went below forecast. We know what to do and we know how to manage those risks in real time. If you’re an experienced IFR pilot, you probably would have thought about that before you even left the ground.
The stakes are raised slightly when managing the risks of icing in instrument meteorological conditions (IMC) and all the aspects of those risks can get very complex. When you fly IFR in helicopters, you’re typically under significant performance constraints from your customer or clients so you’d better have a strong understanding of what tools you need to get from point A to B (and back again) safely and effectively. When your helicopter is certified for flight in known icing conditions, you can bet your life that your customer has even higher expectations of getting the mission completed.
Performance and limitations
Before we can begin to discuss things like route and weather planning, we need to understand how the aircraft protects itself from ice accumulation and consider the limitations of those systems as well as the performance penalties paid while using them.
My current steed is the S-92 and Sikorsky calls their system RIPS (Rotor Icing Protection System). It provides protection against ice build-up through a combination of anti-ice and de-ice systems by electric heating elements for the main rotor, tail rotor, rotor head, engine inlets, windshield, etc. Some systems provide heat continuously while others, like the main rotor blades, are heated with timed (on/off) cycles depending on how much ice is being measured at the ice rate probes. The engine compressor vanes are heated by bleed air.
Like all Transport Category-certified aircraft, these systems all have redundancy and isolation, but they are not without limitation. These limitations can change when you have a failure of a critical component such as the loss of an AC generator or its associated GCU. In addition, emergencies like one engine inoperative (OEI) events further limit rotor ice protection system (RIPS) capabilities and therefore overall aircraft performance when flying in icing conditions. It’s this understanding of system knowledge that needs to be raised to the highest level possible so that you can foresee conclusions based on the failure of a RIPS component at the worst possible time, especially when your operations require some level of CAT A performance.
For example, failure of the No 1 engine concludes with a completely different set of RIPS system limitations than that of a failure of the No 2 engine. This could have significant impact on completing a mission offshore, depending on which pilot (left seat or right) is expected to execute the landing.
Even when everything is going right, using any one of these systems comes with a performance penalty. Each anti-ice/de-ice system consumes heavy electrical loads and thus translates to greater fuel burn. We plan for 1,375lb/hr fuel burn as a baseline in the S-92 but we have fuel contingencies when it comes to flight planning when icing is either forecast or reported. Sikorsky iFly is a fantastic performance app that allows us to preview our take-off performance in icing conditions both all engine operating (AEO) and OEI to ensure we meet CAT A climb performance both on the runway and at the offshore installations. In a worst-case scenario, if we had severe icing in cloud at 500ft AGL on departure (with no tops in sight) and we had an engine failure after takeoff decision point (TDP), we need to know well ahead of time if we have the required climb performance with the RIPS system engaged. If we don’t have that performance, then all bets are off and we can push our pilot decision making straight up the food chain.
Once we completely understand our RIPS system limitations and factor in our performance penalties, we can now look at weather and flight planning.
In Canada, we have some pretty good IFR flight planning products: the Graphic Area Forecast (GFA) charts show clouds and weather, and icing and turbulence. Together, these two graphical area forecasts give us the ‘big picture’ with future cloud cover, tops, ceilings, frontal activity, precipitation, freezing level, amount of icing and turbulence as well as a host of other good stuff. With prevailing westerlies off the coast of Newfoundland, we often see stronger winds above 3,000ft so a typical flight 200nm offshore would likely send us outbound at 5,000ft or 7,000ft and inbound at 2,000ft. Based on that knowledge, we can look at the GFA and see where the ceilings and tops are forecast for the duration of our flight. When it comes to flight planning, it’s time to find the most appropriate cruise altitudes that maximize groundspeed (both directions) while minimizing the time spent in actual icing conditions.
There will be times, however, when the weather gods truly hate you. I’ve flown more than my fair share of offshore flights where we took off in IMC, flew enroute entirely in IMC, shot the offshore approach twice (and missed twice), and flew back to base in IMC that required a precision approach to land. Had we been in moderate or heavy icing the entire time, we would have had to consider not going in the first place.
Again, all fine and dandy when everything is going well. What if you’ve planned your flight ad nauseum and halfway to your destination you get a master caution for a TR DEICE FAIL?
Like we practice in the SIM time and again, systems knowledge along with actioning the specific emergency in the emergency check list (ECL) should lead to a positive outcome. Like weather planning, we have pilot planning: it’s called sim training. Long before we venture off in actual icing conditions, we get to run the drills in the simulator. RIPS component or even full system failures are part of the standard barrage of initial and recurrent training scenarios. Decision making skills are also developed along with confidence building exercises to help you manage and mitigate risks associated with flying in icing, whether it be simulated or real.
The bottom line
To answer my friend’s question, yes, we always have an out. If that means using the RIPS to keep ice off the aircraft, then so be it. The tools are there for us to use. If something goes wrong, we already have a plan to deal with a system failure or we can climb or descend as required to exit icing conditions if we’re dealing with worse than forecast weather. Our final out is the same one we all have – our choice to say no and wait it out for another day.