As the days become cooler and shorter, every PA-46 pilot must begin to mentally prepare for the inevitable icing potential. The most prolific icing question I receive during training events about icing is. “When would you turn it on?” The answer is…it depends on the airframe, engine type, and which icing switch begin discussed. So, I’ll break down each of the PA-46 models and discuss the “why” behind the use of the switch.
A quick caveat that should preclude any discussion of icing…I never plan to fly “in” any icing, I only plan to fly “through” icing. All serious airline/corporate/military pilots respect icing and try to avoid it regardless of the capabilities of their airplane. Climb through any icing to get to the clear weather on top, always divert around “painted weather” (not just convection) that will have moisture conducive to icing, and never accept an ATC clearance that will place you in any prolonged icing. Even though the PA-46 is a wonderful icing platform, icing is weather that no serious pilot “hangs out” in.
Pitot Heat (all PA-46 models): For every PA-46 airframe, this should be “ON’ for every flight regardless of the weather. It is the cheapest insurance policy that exists for the PA-46 pilot. Pilots crash airplanes every year with the only reason being spatial disorientation that occurs after the pitot tube clogs with ice. Just turn it on…there really is no excuse.
Stall warning heat (all PA-46 models): I really don’t care much about Stall Warning Heat. Why? If you’ve got ice on the wing, the wing is going to stall at a different AOA (a lower AOA) than is going to be indicated by the Stall Warning. Stall Warning Heat is probably the most useless switch in the cockpit. If there’s ice on the airplane, you need to fly with additional airspeed and ensure the AOA is lower than usual…the airplane will probably stop creating lift long before the stall warning gives you any indication.
Prop Ice (all PA-46 models): I turn on Prop Ice any time I see ice on the airplane, or prior to entering icing (if I see it coming). There’s no down side to turning it ON beside the additional draw of energy from the electrical system. And, the electrical system will have no problems powering the Prop Ice.
Windshield Heat (all PA-46 models): Windshield Heat is really misnamed. It should be called “Landing Heat” since you will only need it during the landing sequence. If you’ve got ice on your windshield, you are only concerned about it during the landing sequence. Up at altitude, I rarely care. In fact, I like to leave windshield heat OFF in cruise flight and use the windshield as a good “Ice-rate meter” on the PA-46 since it is right in front of me. Some airframes (MU2, some jets, etc) recommend the windshield anti-ice be ON during all operations because it makes the windshield more pliable and safer at altitude in case of a bird strike. I don’t know of any such need in the PA-46. In fact, I think I’ve only used windshield heat twice in 12 years flying the PA-46. But, it is good to have it for those times when you need it. I’ve got a Malibu that I fly regularly that has the “Hot Plate” windshield, and I had the Hot Plate removed for better visibility. Since I live in the southern US, the need for windshield heat is virtually non-existent.
Blowing the boots (all PA-46 models): The myth of “Ice Bridging” has been debunked. I’ve never seen Ice Bridging, and I’ve seen LOTS of icing in my career. So, blow the boots whenever you think they need it. They do seem to work better when more (thicker) ice is present, but that does not mean you cannot blow the boots with only a light film. I blow the boots sometimes in flight just to see if there is ice or not. Sometimes thin films of clear ice can fool you. When in doubt, blow the boots. If I ever do blow the boots in flight, I always touch the prop deice, and pitot heat to make sure they are ON too.
Intake Ice Door (Malibu/Mirage/Matrix only): The ice door rotates the ice box on the pitch axis so as to force air to “make a turn” before going into the turbochargers. It works wonderfully, does not sap engine power, and should be turned to “ALTERNATE” when moisture is present and the OAT is 10C or below. The fins on the front of the intake and the air filter just behind them are some of the first parts to ice up. I move the ice door to ALTERNATE prior to entering icing conditions. Here’s the catch…make sure you don’t move the ice door back to PRIMARY until you are on the ground or until you are absolutely assured that no icing is present in any form on the airplane. If any icing exists in the filter, that ice will be sucked straight into the turbochargers which may be turning in excess of 100,000 RPM. This will effectively “ice-blast” the turbochargers and you’ll get to spend about $5k+ buying new ones.
Ice Deflector (Jetprop only): The Ice Deflector deflects air downward and out of two ports on the belly of the airplane. This creates the advantage of diverting ice, FOD, and anything else from the engine compressor. But, it also reduces the smooth flow of air to the engine, reducing power and effectively making the engine less fuel efficient. With this knowledge, here’s the flow that I use in various phases of flight to control the ice deflector:
- Start-up: Be sure the Ice Deflector is OFF prior to engine start so the ITT stays as low as possible. A hot-start is the enemy of a PT-6 and you want all of the smooth flow of air as possible during engine start.
- Taxi: Turn the Ice deflector ON for taxi as this provides FOD protection while on the ground.
- Takeoff: Leave the Ice Deflector ON for takeoff, and turn it OFF when the greatest threat of FOD diminishes (usually above 2000 AGL).
- Cruise: Leave it OFF for normal operations, and turn it ON if the OAT is below 10C and visible moisture is present.
- Descent: Since the Jetprop cruises so close to Vne, a reduced power setting is always used in any descent. So, I always turn ON the Ice Deflector at the beginning of the descent. Then, I leave it on for the rest of the flight since there is no detriment to fuel burn and reduced power will be used for the rest of the flight.
- Landing and Taxi: You should have the Ice Deflector ON since it was turned on at the beginning of the descent, and I leave it ON for the landing portion so FOD prevention is provided on the ground.
- Shutdown: As one of the last things I do before turning off the battery master switch, I turn the Ice Deflector back to the OFF position so it will be in the proper position for the next engine start.
Too Much Juice?: The potential does exist in the Jetprop to overload the electrical system with Icing equipment. One time, a good customer of mine and I were flying into Colorado and light icing was occurring. We turned all the icing equipment on, to include the windshield, pitot heat, stall heat, and prop heat (all electrical). As we came in for landing, when we put the gear down whole parts of the electrical system simply went blank. It took us quite a while (certainly longer than it should have!) for us to find that the main bus circuit breaker had popped. With all the icing equipment on, the landing gear motor amp flow exceeded the limits of the circuit breaker. The easy fix was to turn off the windshield heat temporarily, lower the gear, and then turn the windshield heat back on.
One thing is for sure…if you fly a PA-46, you need to have a complete understanding of the icing systems. If in doubt, turn it on. But, it’s always better to remove the doubt by having a solid understanding of the PA-46 systems. I hope this discussion helps your understanding of the icing capabilities of the PA-46.