A93Q0245-Collision with Terrain - Umiujaq, Quebec - 01 December 1993

Safety Action Required 
(as presented in the TSB Report)

Obstacle Clearance Altitudes

During this investigation, it became evident that Article 553 of the Air Regulations was being interpreted in a way such that its application with respect to operations in uncontrolled airspace was questionable. The regulation, when used as a reference for the flight conditions required for the transition from IFR flight to VFR flight in uncontrolled airspace, appears to have been ambiguous to such an extent that the Transport Canada (TC) Quebec regional office had an interpretation substantially different from that of TC's head office in Ottawa.

The flight procedure that brings into question the intent of the regulation is an en route IFR descent in instrument meteorological conditions (IMC) to conduct a VFR landing. Air Regulation 553 requires that aircraft in IFR flight be flown at an altitude 1,000 feet above the highest obstacle within 5 miles of the estimated position of the aircraft, except when taking off or landing (3). The descent procedure used by the aircrew in this occurrence, and interpreted by the TC regional office as being acceptable, could eliminate this safety margin. Using a line of thinking consistent with this interpretation, a crew could descend an aircraft in IMC, without being on an approved instrument approach, to an altitude where visual meteorological conditions (VMC) were anticipated, as long as the descent was considered to be for the purpose of landing. The Board and TC's head office both believe that this was not the intent of the regulation.

The new Canadian Aviation Regulations (CARs)(recently announced in the Canada Gazette) contain a detailed section on minimum altitudes to ensure obstacle clearance in IFR flight; however, the CARs are no clearer than the Air Regulations as to what differentiates the en route and/or approach phase of a flight from the landing phase. Nevertheless, until the CARs are in effect, aircrew are still required to fly in accordance with the existing Article 553; therefore, some aircrew may still believe that a descent is permissible to any altitude while attempting to transition to a VFR landing. Moreover, given the increasingly widespread use of GPS for navigating in remote areas and considering GPS' reputation for accuracy, aircrew may be more likely than ever to question the need for the 1,000-foot safety buffer.

The Board is concerned that regulatory officials and the operator of a fleet of state aircraft apparently did not question the appropriateness of a procedure that put aircraft, crew, and passengers at an increased level of risk. Therefore, the Board recommends that:

The Department of Transport advise the aviation community, including Transport Canada regional staff, of the correct interpretation of Air Regulation Article 553;(A96-01)


The Department of Transport clarify the wording of the CARs with respect to descents for landing in uncontrolled airspace to ensure that the intended level of safety is not jeopardized through misinterpretation. (A96-02)

Transport Canada's Response:

Transport Canada agrees that, in general, further efforts are required to eliminate confusion that may exist related to IFR flight in uncontrolled airspace. However, further clarification of Air Regulation (AR) 553 (which requires that aircraft maintain certain altitudes and distances from obstacles while operating under IFR) is unwarranted if related regulations and guidance material are considered.

Regulations cannot be considered in isolation of other relevant regulations or guidance material; to do so may lead to misinterpretation. When other regulations and guidance material are considered, the intent of AR 553 becomes clear. For instance, paragraph 548(1) (c) is relevant in this case, and applies to the pilot-in-command of an aircraft that is in IFR flight of IFR weather conditions-..."where the aircraft makes an approach to an airdrome or a runway, ensure that the approach is made in accordance with the instrument approach procedure, unless otherwise authorized by the appropriate air traffic control unit." At the time of the accident there was no published instrument approach procedure for Umiujaq, Quebec.

Guidance material is contained in AIP Canada in Section 9.0 - Instrument Flight Rules - Arrival Procedures, paragraph 9.7.1 "In accordance with Air Reg. s.553, the aircraft shall be flown at an altitude of at least 1,000 feet above the highest obstacle located within a horizontal radius of 5 miles from the estimated position of the aircraft in flight until the required visual reference is acquired in order to conduct a normal landing. Pilots are cautioned that conducting a contact approach in minimum visibility conditions introduces hazards to flight not experienced when flying IFR procedures." When considered together, the relevant regulations and guidance material provide clear intent.

Notwithstanding the above, confusion may exist as to the application of IFR in uncontrolled airspace. The department has taken steps to eliminate this possibility in the following ways:

  1. Different interpretations have existed regarding the application of the Instrument Flight Rules. Some were of the opinion that IFR did not apply in uncontrolled airspace, while others were of the opinion that IFR did not apply unless the aircraft was being operated in accordance with an IFR air traffic control clearance. In order to minimize the possible misinterpretation of application, CARs Part VI, Division VII - Instrument Flight Rules, section 602.121, General Requirements, has been drafted in such a way as to eliminate any question regarding the application of the division.
  2. The CARs Training Course that was delivered at least three times in every region over the winter contained, in its course material, information on the new construction of the division pertaining to instrument flight rules. The training was given not only to familiarize Transport Canada staff and the aviation community with the new regulations, but also to begin to establish uniform interpretation of the content and application of the regulations.

It is believed that these actions will meet the intent of recommendations A96-01 and A96-02; namely, to eliminate any confusion regarding the application of regulations in uncontrolled airspace. The Department will monitor compliance with the CARs, paying particular attention to possible misinterpretation of intent on the part of both departmental staff and the aviation community.


(3) The Air Regulations define "landing" as the act of coming into contact with a supporting surface; this includes the immediately preceding and following acts.

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