|Issuing Office:||Standards Branch|
|Document No. :||CASA 2010-02|
|File Classification No. :||Z 5000-35|
|Issue No. :||02|
|RDIMS No. :||10731567|
The purpose of this Civil Aviation Safety Alert (CASA) is to alert operators and pilots to the possible need for higher elevator control forces that may be required for proper rotation to the takeoff attitude on aircraft with unpowered elevator control surfaces (i.e. flight controls without hydraulic assistance) when treated with Type II, III or IV anti-icing fluids. Inadequate training on these added forces or missed identification of this potential scenario could lead a pilot to reject a takeoff from speeds above V1 and exceed the available runway length during the rejected takeoff.
The reason for the re-issue of this CASA is to further substantiate the Background and Recommended Action sections as a result of recent incidents and more recent operational research carried out to investigate this issue.
Over the past years, Transport Canada (TC), the European Aviation Safety Agency (EASA) and the Federal Aviation Administration (FAA) have received numerous reports of flight crews that have conducted rejected takeoffs after their airplanes were treated with thickened anti-icing fluids. Some of the aircraft types which appear to be affected are also operated by Canadian operators. TC initially reproduced and distributed FAA safety information (Safety Alert for Operators SAFO 10001)Footnote1 and is now updating this CASA to be more reflective of its current understanding of the issue.
Flight crews have reported that some aircraft did not respond to normal, or even slightly above normal, control column back pressure inputs for rotation to the takeoff attitude. The flight crews assessed the need for unusually high back pressure forces to be a flight control failure and elected to reject the takeoff at speeds in excess of V1. Fortunately, these rejected takeoffs did not occur during takeoffs that were runway length limited.
Moreover, an investigation carried out by the Swedish Accident Investigation Authority (Statens haverikommission - SHK) on a January 11th, 2010 incident in Helsinki, FinlandFootnote2 involving an aircraft with unpowered flight controls (elevators) concluded that, for unknown reasons, the elevator restriction during rotation was due to the use of thickened anti-icing fluids on an individual aircraft where the horizontal stabilizer and elevator are too close together.
In late 2014, EASA carried out research to experimentally reproduce this phenomenon as reported by pilots via wind tunnel testing of a horizontal stabilizer model. The results confirmed the potential hazard of increased stick forces during rotation at take-off when thickened deicing/anti-icing fluids were appliedFootnote3. EASA is continuing its assessment and will be aiming to coordinate any potential future actions, including those related to continued airworthiness and type certification with TC and the FAA.
The common factors in all the reported incidents and those reproduced experimentally is that the rotation speeds were below, at, or only slightly above the recommended 100 knot minimum rotation speed for the use of thickened (i.e. Type II, III or IV) anti-icing fluids. In addition, the airplanes involved were all equipped with unpowered elevator flight controls. In all of the reported cases, the use of thickened anti-icing fluids was approved for the airplane, and the flight crews reported following the airplane manufacturer’s procedures for takeoff after being treated with thickened anti-icing fluids.
In many of these reported cases, the rejected takeoffs occurred during the flight crew’s first takeoff or their first takeoff for that winter season, after the airplane was treated with thickened anti-icing fluids. The flight crew must be aware of and trained on the airplane manufacturer’s procedures for operations after the application of de/anti-icing fluids, including any added control column forces that may be necessary to achieve the appropriate takeoff pitch attitude.
There are several theories to the cause of this above normal control elevator force requirement including the possibility that the thickened anti-icing fluid is being applied too heavily, above the thickness recommended by the fluid manufacturer and the SAE standard, to the horizontal tail surfaces.
Only the de/anti-icing fluid Types (I, II, III, IV) approved by the airplane manufacturer should be applied to the airplane. The airplane must be operated in accordance with the airplane manufacturer’s procedures specified for operations after being treated with de/anti-icing fluids.
Directors of safety, directors of operations, chief pilots, check pilots, pilot instructors, training providers and pilots of aircraft with unpowered elevator controls and rotation speed below, at, or only marginally above 100 knots should be trained on the control column forces that may be necessary to rotate the aircraft to the takeoff attitude when the airplane is treated with thickened anti-icing fluids. The operator should include in the flight crew operating procedures the airplane manufacturer’s procedures for operation of the airplane after being treated with de/anti-icing fluids.
As part of the pre-takeoff crew briefing or takeoff procedures review (single pilot operations), pilots should include the airplane manufacturer’s procedures and the possible need for added control column back pressure if the aircraft is treated with thickened anti-icing fluids. The flight crew should adhere to the manufacturer’s procedures for the aircraft when treated with de/anti-icing fluids.
Additionally, operators should ensure that all de/anti-icing service providers are aware of the potential impact of applying anti-icing fluids on the horizontal tail surfaces in excess of that needed to provide adequate ice protection.
Operators should ensure that de/anti-icing service providers have processes and procedures in place within their ground icing programs to prevent excessive anti-icing fluid applications to the horizontal surface areas that is recommended by the fluid manufacturer and the appropriate SAE standard(s) to provide the necessary ice protection.
For more information concerning this issue, contact Mr. Roman Marushko, Program Manager, Flight Technical and Operator Certification, Commercial Flight Standards, in Ottawa, by telephone at 613 9934692, or by e-mail at firstname.lastname@example.org.
ORIGINAL SIGNED BY
The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.
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