Wx Watch: On Deck--New Icing Rules

In last month's Wx Watch (" News from the Icing Front," February Pilot), we talked about the FAA's In-flight Aircraft Icing Plan and touched on some of the recent advances in the icing forecast community. Improving the timeliness, accuracy, and volume of icing forecasts is one of the big objectives of the Icing Plan. It appears that the plan is well on the way to meeting those objectives.

Another main objective of the Icing Plan is to urge the FAA to require that "certain" aircraft exit icing conditions when "specific visual cues" are observed. By "certain," the plan refers to virtually all aircraft having pneumatic deice boots and unpowered ailerons — not just the turboprop commuter airplanes whose accidents sparked the plan. That includes FAR Part 23 turboprop and piston-powered singles and twins, plus a few business jets — the early Cessna Citations and the Rockwell Sabreliners — that used pneumatic boots to deice their leading edges. In other words, the kinds of airplanes that many of us fly, or hope to fly.

By "specific visual cues" the FAA means the signature types of ice formations that accrete on airplanes flying in conditions conducive to large-droplet icing.

In September 1997 the FAA issued notices of proposed rulemaking (NPRMs) for the affected airplanes. The proposed rules would require additions to the "Limitations and Normal Procedures" sections of the airplane flight manuals (AFMs) for those airplanes. That means they'd carry plenty of regulatory punch — enough to satisfy the intent of the Icing Plan.

What are the specific visual cues? What are the additions to the AFMs?

The visual cues are those that accompany the very dangerous large-droplet icing conditions that felled an ATR-72 commuter over Roselawn, Indiana, back in October 1994. (It was that accident that kicked off the Icing Plan in the first place). Quoting from the NPRM, "Severe icing conditions that exceed those for which the airplane is certificated shall be determined by the following visual cues. If one or more of these visual cues exists, immediately request priority handling from air traffic control to facilitate a route or an altitude change to exit the icing conditions." These cues are:

• Unusually extensive ice accumulations on the airframe and windshield in areas normally not observed to collect ice
• Accumulation of ice on the upper surface of the wing, aft of the protected area
• Accumulation of ice on the engine nacelles and propeller spinners farther aft than normally observed

Those cues, and the requirement to request priority handling, are proposed to be published in the "Limitations" section of the affected AFMs, along with a preface warning that "Flight in freezing rain, freezing drizzle, or mixed icing conditions may result in ice buildup on protected surfaces exceeding the capability of the ice protection system, or may result in ice forming aft of the protected surfaces. This ice may not be shed using the ice protection systems, and may seriously degrade the performance and controllability of the airplane."

Nothing new here, you say. We all know that known-icing certification doesn't guarantee safe passage in the worst ice. That warning has been in a lot of magazine articles and textbooks. In addition, any pilot with the smallest particle of common sense would immediately try to exit icing conditions of any kind — no matter what kind of airplane he/she is flying, and regardless of whether it's known-ice certificated.

No, the big news here is that this may be the first time this kind of guidance becomes codified in AFMs. Common sense becomes law.

As for the "Normal Procedures" sections of the manuals for the affected airplanes, the following procedures are proposed for inclusion. Here's the complete passage:

The following weather conditions may be conducive to severe in-flight icing:

• Visible rain at temperatures below zero degrees Celsius ambient air temperature.
• Droplets that splash or splatter on impact at temperatures below zero degrees ambient air temperature.

Procedures for exiting the severe icing environment:

These procedures are applicable to all flight phases from takeoff to landing. Monitor the ambient air temperature. While severe icing may form at temperatures as cold as minus 18 degrees Celsius, increased vigilance is warranted at temperatures around freezing with visible moisture present. If the visual cues specified in the [proposed] "Limitations Section" of the AFM for identifying severe icing conditions are observed, accomplish the following:

• Immediately request priority handling from ATC to facilitate a route or an altitude change to exit the severe icing conditions in order to avoid extended exposure to flight conditions more severe than those for which the airplane has been certificated.
• Avoid abrupt and excessive maneuvering that may exacerbate control difficulties.
• Do not engage the autopilot.
• If the autopilot is engaged, hold the control wheel firmly and disengage the autopilot.
• If an unusual roll response or uncommanded roll control movement is observed, reduce the angle of attack.
• Do not extend flaps when holding in icing conditions. Operation with flaps extended can result in a reduced wing angle of attack, with the possibility of ice's forming on the upper surface farther aft on the wing than normal, possibly aft of the protected area.
• If the flaps are extended, do not retract them until the airframe is clear of ice.
• Report these conditions to air traffic control.

The intent of the NPRM is to avoid any more ice-induced roll upsets of the kind that happened at Roselawn. And while the proposals are aimed at airplanes with boots, there's information here that pilots of non-ice-protected airplanes can use as well.

The NPRM doesn't explicitly say so, but some language implies that it's directed at airplanes certified for flight in known icing. But a strict interpretation — the repetitive references to airplanes with boots and unpowered ailerons, with no mention of known-icing certification — paves the way for these rules to find their way into the AFMs of airplanes with STC'd boot installations. STC'd installations often do not bestow known-icing certification. Rather, they are installed on a no-hazard certification basis. This means that while the boots may work and won't harm the flight characteristics of the airplane, they haven't been thoroughly tested in icing conditions and therefore may not provide the level of protection that a certified installation does. Either way — STC or certified — it probably won't make much difference in large-droplet icing.

The final rules were to be published in late January. By the time you read this, you may have already received or seen the new AFM entries.

E-mail the author at [email protected].

Airplanes affected by the new icing NPRMs include:

• Aerospace Technologies of Australia, models N22B and N24A
• Aerostar Aircraft Corp. PA-60-600, -601, -601P, -602P, -700P
• Cessna models 500, 501, 550, 551, and 560 series
• Cessna P210N, T210N, P210R, and 337 series
• Cessna models T303, 310R, T310R, 335, 340A, 402B, 402C, 404, F406, 414, 414A, 421B, 421C, 425, and 441
• Fairchild models F27 and FH227 series
• Frakes Aviation model G-73 (Mallard) and G-73T series
• Gulfstream G-159 series
• Harbin Aircraft model Y12 IV
• McDonnell Douglas DC-3 and DC-4 series
• Mitsubishi Heavy Industries Model YS-11 and YS-11A series
• New Piper models PA-23, -23-160, -23-235, -23-250; PA-E23-250, PA-30, PA-39, PA-40, PA-31, PA-31-300, PA-31-325, PA-31-350, PA-34-200, PA-34-200T, PA-34-220T, PA-42, PA-42-720, PA-42-1000
• New Piper PA-46-310P and PA-46-350P
• Partenavia P68, AP68TP 300, AP68TP 600
• Piaggio P-180
• Pilatus Britten-Norman BN-2A, -2B, and -2T
• Raytheon Aircraft Company models B55, B55A, 58, 58A, 58P, 58PA, 58TC, 58TCA, 60 series, 65-B80 series, 90 series, F90 series, 100 series, 300 series, B300 series, and Model 2000
• Sabreliner models 40, 60, 70, and 80 series
• SIAI-Marchetti models SF600 and SF600A
• Socata TBM-700
• Twin Commander models 500, 500-A, 500-B, 500-S, 500-U, 520, 560, 560-A, 560-E, 560-F, 680, 680-E, 680FL(P), 680T, 680V, 680W, 681, 685, 690, 690A, 690B, 690C, 690D, 695, 695A, 695B, 720

Links to the full text of icing NPRMs affecting these aircraft can be found on AOPA Online ( www.aopa.org/pilot/links.shtml).