Appendix 1
c. Approximately 5 minutes before the accident, the ASOS at RWL reported the weather as few clouds at 500 feet above ground level (AGL), scattered clouds at 900 feet AGL, overcast ceiling at 1,500 feet AGL, visibility 2 miles with light snow and mist, temperature 32°F, dew point 32°F, winds 250 degrees at 3 knots, and altimeter 29.35 inches of mercury (Hg).
Before departing SBS, the pilot received a weather briefing from Denver Flight Service. The briefer told the pilot that there was a band of light to moderate snow shower activity half way between Rock Springs and Rawlins, spreading to the northeast. The briefer told the pilot there were adverse conditions and flight precautions along his route for occasional mountain or terrain obscurations. The pilot responded that he planned to fly instrument flight rules for the entire flight.
d. The Surface Analysis showed a north-south stationary front positioned along the front range of the Rocky Mountains beginning at the Wyoming/Montana border and extending south into north-central Colorado. Station plots indicated patchy snow over western Colorado and Wyoming. The most recent AIRMET reported, “Occasional moderate rime, or mixed icing in clouds and precipitation between the freezing level and flight level 220.” The freezing level for the area encompassing the route of flight began at the surface. Witnesses in the vicinity of RWL reported surface weather conditions varying from freezing rain to heavy snow. The Current Icing Product (CIP) showed no potential for SLD, yet an examination of the airplane showed clear ice up to 1½ inches thick adhering to the vertical stabilizer, the left and right wings, the right main landing gear tire, and the right propeller.
e. The airplane’s aerodynamic performance was degraded due to the ice contamination, leading to a stall. An examination of the airplane’s systems revealed no anomalies. FAA Advisory Circular (AC) 135-15, Emergency Medical Services/Airplane (EMS/A), addresses several subject areas that were not practiced by the operator, including the recommendation of avoiding flight in icing weather whenever possible.
f. The National Transportation Safety Board determined that the probable cause of this accident was the pilot’s inadvertent flight into adverse weather (severe icing) conditions, resulting in an aerodynamic stall and impact with rising, mountainous terrain during approach. A factor contributing to the accident was the pilot’s inadequate planning for the forecasted icing conditions.
8. Cirrus SR-22 (Childersburg, Alabama).
a. This accident shows the importance of obtaining an up-to-date weather briefing that includes icing forecasts and freezing levels. It also highlights the performance degradation that can occur when an airplane not certificated for flight in icing exceeds its limits.
b. On January 13, 2006, a Cirrus SR-22 was en route from Birmingham, AL to Orlando, FL, when it encountered icing conditions and entered an inadvertent stall and spin. The pilot deployed the ballistic recovery system parachute, and the aircraft descended into the trees leaving the three occupants of the aircraft uninjured.
c. The night before the accident, the pilot obtained a full Direct User Access Terminal (DUATS) briefing, though the briefing was not valid for the time of the accident. The National Page 6
Appendix 1 Weather Service (NWS) issued an AIRMET Zulu update 3 for icing and freezing level data valid from 1445 CST until 2100 CST. The advisory warned of occasional moderate to mixed icing-in-clouds and in precipitation between 3,000 to 8,000 feet. Within the boundaries of the advisory were the departure airport and the accident site. The pilot requested an abbreviated DUATS weather briefing at 1244 EST for his route of flight. The in-flight advisories were to expire at 1500 CST. The briefing provided several adverse weather phenomena impacting the route of flight from icing, turbulence, and thunderstorms. The pilot stated he was not aware of AIRMET ZULU UPT 3 that was issued by the NWS before he departed Birmingham, though the airplane was equipped with an XM Satellite radio and the AIRMET was transmitted by the NWS over the XM radio installed in the airplane. This was significant, considering the airplane is not certificated for flight into icing conditions.
d. The pilot stated the flight departed from runway 24 and he contacted the air traffic controller on the radio. ATC radar identified the aircraft and the pilot was instructed to climb to 7,000 feet and proceed direct to HANDE intersection. With the autopilot engaged, the airplane entered the clouds at 5,000 feet, climbing at 120 knots. Upon reaching 7,000 feet, the airplane encountered icing conditions. The pilot informed the controller that he would like to climb to 9,000 feet and that was approved.
e. As the airplane reached the cloud tops in visual flight conditions at 8,000 feet, the airplane began to buffet. The pilot looked at his airspeed indicator and it indicated 80 knots. A stall ensued, followed by a spin that descended the airplane back into instrument flight conditions. The pilot deployed the ballistic parachute system and informed the air traffic controller of his actions. The airplane descended under the parachute canopy into the trees.
f. The NTSB determined the probable cause(s) of this accident as follows:
(1) The pilot’s inadequate preflight planning, failure to obtain a current weather briefing, and his decision to operate the airplane into a known area of icing outside the airplanes certification standards.
(2) This resulted in the aircraft accumulating ice, a loss of airspeed, an inadvertent stall/spin, and subsequent collision with trees.
Appendix 2 APPENDIX 2. REGULATORY ISSUES RELATED TO ICING Title 14 CFR parts 91, 121, 125, and 135 specify the responsibilities of flightcrews concerning flight in icing conditions. Pilots are advised to check the current regulations for revisions. They are noted here for reference only and to illustrate the degree of similarity between parts 91, 121, 125, and 135 with respect to regulation of flight into icing conditions. An important distinction in each of these regulations is the restriction on flight into “known or forecast” conditions. Because of the limitations of icing forecasts, it is admittedly difficult for pilots to be certain whether the conditions in which they are flying actually will result in an icing encounter, and it is even more difficult to determine the severity of the possible encounter. Pilots can be caught inadvertently in icing conditions that exceed these legal limits.
General operating and flight rules for GA aircraft are found in part 91, but not all rules within part 91 are applicable to all GA aircraft. Section 91.501 states that the rules in subpart F apply only to large and turbojet-powered multiengine airplanes that are not covered by parts 121, 125, 129, 135, and 137. Section 91.527, Operating in icing conditions, falls within subpart F and thus is not applicable to all GA aircraft.
1. Part 91 Icing Regulations.
a. IFR. No pilot may fly an airplane under IFR into known or forecast moderate icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet the requirements in 14 CFR part 135, appendix A, paragraph 34 of Special Federal Aviation Regulation (SFAR) No. 23.
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
b. VFR. No pilot may fly an airplane under VFR into known light or moderate icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet the requirements in SFAR 23 paragraph 34 (same as part 135, appendix A, paragraph 34, and § 23.1419 at Amendment 23-14).
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface vertical tail, control surface flap, aileron, elevator, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
Appendix 2
c. Severe Icing. No pilot may fly an airplane into known or forecast severe icing conditions unless:
(1) The airplane has ice protection provisions that meet the requirements in SFAR 23 paragraph 34, or;
(2) The airplane has ice protection provisions that meet the requirements for transport category airplane type certification.
NOTE: Even airplanes approved for flight into known icing conditions should not fly into severe icing. Many Airplane Flight Manual Limitations Sections require an immediate exit when these types of conditions are encountered.
NOTE: Airplane certification for flight into known icing conditions does not include freezing drizzle and freezing rain. In fact, some airplanes are prohibited from flying into freezing drizzle or freezing rain, regardless of its intensity. These conditions are very dangerous and can cause ice to form behind the protected areas. (See § 91.527, Operating in icing conditions, for the exact language of the above regulations.)
d. Aircraft Not Certificated for Flight in Icing Conditions.
(1) Aircraft certificated since the mid-1970s that are not certificated for flight in icing conditions will have a limitation in the AFM or POH and possibly a placard on the aircraft stating that flight into “known icing conditions” is prohibited. “Known icing conditions,” as defined in the AIM, are conditions in which ice is observed or detected in flight, by your aircraft or another aircraft, or an airport. Such limitations are binding under § 91.9, Civil aircraft flight manual, marking, and placard requirements, and this regulation takes precedence over §§ 91.527 and 135.227. However, if a pilot of such an airplane were to takeoff and fly in area in which icing is forecast (e.g., AIRMET Zulu), it is expected the pilot will through preflight planning and in-flight execution:
(a) First attempt to avoid areas of “potential icing conditions”, which are areas of visible moisture such as clouds at temperatures below freezing;
(b) If that is not practical, attempt to avoid areas of forecast icing by all tools available (e.g., AIRMETs, SIGMETs, CIP and FIP); and
(c) If icing is encountered, declare an emergency and exit the conditions immediately.
NOTE: Failure to follow the section above may result in enforcement action under § 91.103, Preflight action, or § 91.13, Careless or reckless operation, depending on the circumstances and the actions a reasonable pilot will take.
Pilot should remember, these airplanes were not tested for inadvertent encounters and since most icing conditions consist of small drops and low Page 2
Appendix 2 LWC, should not assume their airplane can tolerate all icing conditions after one successful encounter.
(2) Aircraft certificated prior to the mid-1970s that are not certificated for flight in icing conditions may not have any prohibitions stated in the AFM or POH. If not, they are not covered by either § 91.527 or § 91.9. However, given that information on the dangers of aircraft icing has been widely disseminated for many years, certain actions, such as taking off with wings coated with ice, could be interpreted as prohibited under § 91.13.
2. Part 121 Icing Regulations (see § 121.341, Equipment for Operations in Icing Conditions).
a. Icing Conditions. No person may fly an airplane in icing conditions unless one or more of the following apply:
(1) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
(2) The aircraft is type certificated under the transport category airworthiness requirements relating to ice protection.
(3) The aircraft is a non-transport category airplane type certificated after December 31, 1964, which meets the provisions detailed below.
b. Non-Transport Category Airplanes Type Certificated After December 31, 1964.
(1) IFR. No pilot may fly a non-transport category airplane under IFR type cerftificated after December 31, 1964, into known or forecast light or moderate icing conditions unless one or more of the following apply:
(a) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.
(b) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(c) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
(2) VFR. No pilot may fly a non-transport category airplane under VFR type certificated after December 31, 1964, into known light or moderate icing conditions unless one or more of the following apply:
(a) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.
Appendix 2
(b) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(c) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
(3) Severe Icing. No pilot may fly a non-transport category airplane type certificated after December 31, 1964, into known or forecast severe icing conditions unless one or more of the following apply:
(a) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.
(b) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
NOTE: Even airplanes approved for flight into known icing conditions should not fly into severe icing. Many Airplane Flight Manual Limitations Sections require an immediate exit when these types of conditions are encountered.
NOTE: Airplane certification for flight into known icing conditions does not include freezing drizzle and freezing rain. In fact, some airplanes are prohibited from flying into freezing drizzle or freezing rain, regardless of its intensity. These conditions are very dangerous and can cause ice to form behind the protected areas.
(4) Nighttime Icing Conditions. No person may operate an airplane in icing conditions at night unless:
(a) Means are provided for illuminating or otherwise determining the formation of ice on safety-critical parts of the wings.
(b) Any illumination used is of a type that will not cause glare or reflection that would handicap crewmembers in the performance of their duties.
3. Part 125 Icing Regulations (see § 125.221, Icing Conditions: Operating Limitations).
a. Frost, Ice, and Snow Accumulation. No pilot may take off an airplane that has frost, ice, or snow adhering to any propeller, windshield, wing, stabilizing surface, control surface, powerplant installation, airspeed instrument, altimeter, rate of climb instrument, or flight attitude instrument system unless:
(1) Frost adhering to the wings, stabilizing surfaces, or control surfaces has been polished to make it smooth.
Appendix 2
(2) The Administrator has authorized takeoffs with frost under the wing in the area of the fuel tanks.
b. Anticipated Frost, Ice, or Snow Accumulation. When conditions are such that frost, ice, or snow may reasonably be expected to adhere to the airplane, no certificate holder may authorize an airplane to take off, nor may any pilot take off, unless the pilot has completed the testing required under § 125.287(a)(9) and one or more of the following apply:
(1) A pretakeoff contamination check established by the certificate holder and approved by the Administrator for the specific airplane type has been completed within five minutes prior to beginning takeoff. A pretakeoff contamination check is a check to make sure the wings and control surfaces are free of frost, ice, or snow.
(2) The certificate holder has an approved alternative procedure under which the airplane is determined to be free of frost, ice, or snow.
(3) The takeoff complies with the certificate holder’s approved deicing/anti-icing program (which must comply with § 121.629(c)).
c. IFR. No pilot may fly an airplane under IFR into known or forecast light or moderate icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet part 125, appendix C.
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane.
(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
d. VFR. No pilot may fly an airplane under VFR into known light or moderate icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet part 125, appendix C.
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
e. Severe Icing. No pilot may operate into known or forecast severe icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet part 125, appendix C.
Appendix 2
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
4. Part 135 Icing Regulations (see § 135.227, Icing Conditions: Operating Limitations.)
a. IFR. No pilot may fly an airplane under IFR into known or forecast light or moderate icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
b. VFR. No pilot may fly under VFR into known light or moderate icing conditions unless one or more of the
(1) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.
c. Severe Icing. No pilot may operate into known or forecast severe icing conditions unless one or more of the following apply:
(1) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.
(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.
NOTE: Even airplanes approved for flight into known icing conditions should not fly into severe icing. Many Airplane Flight Manual Limitations Sections require an immediate exit when these types of conditions are encountered. Airplane certification for flight into known icing conditions does not include freezing drizzle and freezing rain. In fact, some airplanes are prohibited from flying into freezing drizzle or freezing rain, regardless of its intensity. These conditions are very dangerous and can cause ice to form behind the protected areas.
Appendix 3 APPENDIX 3. ICING CHECKLISTS The following checklists contain icing-specific items that should be considered before operating in possible icing conditions. The checklists are intended to supplement pilot information. These checklists should not replace or supersede AFM or POH.
1. Aircraft Not Certificated or Equipped for Flight in Icing Conditions.
a. Preflight.
(1) Always obtain a thorough preflight weather briefing. Evaluate cloud types, bases, and tops; types of precipitation; freezing levels; and pilot reports. Check for AIRMET Zulus and convective SIGMETS. Supplement your weather briefing by reviewing graphical data at:
http://adds.aviationweather.gov.
(2) Pack additional items in your flight bag such as a large flashlight, spare fresh batteries, and transceiver.
(3) During preflight planning, identify alternate airports along the route of flight to be used if unscheduled weather is encountered. If possible, choose airports with long runways.
(4) Always know how to escape icing conditions (i.e., either climb or descend into warmer areas, make a 180-degree turn, etc.)
(5) During the preflight inspection, clean all ice, frost, and snow off the aircraft.
(6) Check that pitot heat is operable.
(7) Check pitot/static openings, fuel drains, and stall warning sensors to ensure they are not clogged with ice.
(8) Clear any accumulated ice or snow from brakes and wheel fairings.
(9) Check controls externally for ice/snow binding.
b. Taxi/Takeoff/In-Flight.
(1) Use brakes carefully during taxi to prevent skidding.
(2) Ensure that carburetor heat or alternate air is working.
(3) Check controls for full range of motion.
(4) Aircraft with turbine engines: Perform regular turbine engine power run-ups while taxiing to shed ice, per the AFM procedures.
(5) After takeoff, if recommended by the manufacturer, cycle landing gear to clear snow or slush from wheel wells.
Appendix 3
(6) During flight, monitor engine RPM. A drop in RPM or manifold pressure may indicate induction icing. Apply carburetor heat or alternate air if required.
(7) If ice is encountered in-flight, exit the conditions immediately.
(8) Use visual cues to identify ice formation. If ice forms on the wing, there is a possibility the tail may be accumulating ice as well.
(9) Stay alert for any performance or handling degradation that may be an indicator of ice accumulation.
(10) Remember that recovery procedures from an ice-induced tailplane stall are opposite from those for an ice-induced wing stall.
(11) If using an autopilot, when workload permits, periodically disengage and manually fly the aircraft to identify possible handling changes or control jamming caused by ice.
c. Approach and Landing.
(1) Be prepared for unexpected attitude changes when changing the airplane’s configuration. If the aircraft’s performance characteristics change suddenly, return to the previous configuration.
(2) If landing with an accumulation of ice on the tailplane, perform a no-flap landing at a higher approach speed. Use a longer runway if available.
(3) After touchdown, use brakes sparingly to prevent skidding.
2. Piston Aircraft Certificated or Equipped for Flight in Icing Conditions.
a. Preflight.
(1) Always obtain a thorough preflight weather briefing. Evaluate cloud types, bases, and tops; types of precipitation; freezing levels; and pilot reports.
(2) Pack additional items in your flight bag such as a large flashlight, spare fresh batteries, and transceiver.
(3) During preflight planning, identify alternate airports along the route of flight to be used if unscheduled weather is encountered. Choose airports with longer runways.
(4) Always know how to escape icing conditions (either climb or descend to warmer areas, make a 180 degree turn, etc.).
(5) During the preflight inspection, clean all ice, frost, and snow off the aircraft.
(6) Check that pitot heat and static heat are operable.
Appendix 3
(7) Check pitot/static openings, fuel drains, and stall warning sensors to ensure they are not clogged with ice.
(8) Cycle deicing and anti-icing systems to check for proper operation.
(9) Clear any accumulated ice or snow from brakes and wheel fairings.
(10) Check controls externally for ice/snow binding.
b. Taxi/Takeoff/In-Flight.
(1) Use brakes carefully during taxi to prevent skidding.
(2) Ensure that carburetor heat or alternate air is working.
(3) Check controls for full range of motion.
(4) After takeoff, if recommended by the manufacturer, cycle landing gear to clear snow or slush from wheel wells.
(5) During flight, monitor engine RPM. A drop in RPM or manifold pressure may indicate induction ice. Apply carburetor heat or alternate air if required.
(6) Refer to the AFM or POH for proper operation of anti-icing and deicing systems.
A rule of thumb is that anti-ice systems should be activated at the first sign of visible moisture with air temperatures some margin above freezing. Deicing systems should be activated at the first sign of ice accretion.
(7) Use visual cues to identify ice formation and regularly check for ice accumulation behind protected areas on the aircraft. If ice forms on the wing, there is a possibility that the tail may be accumulating ice as well.
(8) Stay alert for any performance or handling degradation that may be an indicator of ice accumulation.
(9) Remember that recovery procedures from an ice-induced tailplane stall are opposite from those for an ice-induced wing stall.
(10) If using an autopilot, if workload permits, periodically disengage and manually fly the aircraft to identify handling changes caused by airframe icing.
c. Approach and Landing.
(1) Be prepared for unexpected attitude changes when changing the airplane’s configuration. If the aircraft begins to roll or pitch unexpectedly, return to the previous configuration.
(2) If landing with an accumulation of ice, use a higher approach speed. Use a longer runway if available.
Appendix 3
(3) After touchdown, use brakes sparingly to prevent skidding.
3. Turbo-Propeller Aircraft.
a. Preflight.
NOTE: Professional flightcrews flying complex, high performance aircraft should always refer to the AFM or POH and company guidance materials as the authority for procedures for flight into icing conditions.
(1) For ground deicing operations, refer to company manuals, AC 120-58, and AC 135-17 for guidance.
(2) Always obtain a thorough preflight weather briefing. Look for cloud types, bases, and tops; types of precipitation; freezing levels; and pilot reports.
(3) Preflight icing inspections of the aircraft in ground icing conditions are essential.
Tactile inspections are mandatory for some aircraft and are very valuable for detecting clear ice.
By physically touching the surface, any fine contaminants not easily visible can be detected.
Refer to AFM or POH to determine if a tactile inspection is mandatory for your aircraft.
(4) Clean all ice, frost, and snow off of the aircraft
(5) Check that pitot heat and static heat are operable.
(6) Check pitot/static openings, fuel drains, and stall warning sensors to ensure they are not clogged with ice.
(7) Cycle anti-icing and deicing systems to check for proper operation.
(8) Clear any accumulated ice or snow from brakes and wheel fairings.
(9) Inspect the engine inlets of turbine engines and remove any accumulated ice from the nacelle inlet as well as around the nacelle drain hole and around the fan blades.
b. Taxi/Takeoff/In-Flight.
(1) Use brakes carefully during taxi to prevent skidding.
(2) Check controls for full range of motion.
(3) After takeoff, if recommended by the manufacturer, cycle landing gear to clear snow or slush from wheel wells.
(4) Refer to the AFM or POH for proper operation of anti-icing and deicing systems.
A rule of thumb is that anti-ice systems should be activated at the first sign of visible moisture with air temperatures some margin above freezing. Deicing systems should be activated at the first sign of ice accretion.