Relevant Regulations / Policy / Background

A320 Special Conditions for Certification

Since the A320 presented a considerable number of new and novel technologies when it was first introduced, some of these technologies were not addressed within existing regulations. A number of Special Conditions were therefore applied where current regulations did not contain adequate or appropriate safety standards due to novel or unusual design features. The Airworthiness Authorities of Germany, England, and the Netherlands participated with France in a joint certification of the A320 in February 1988. U.S. type certification of the A320 came later in December 1988.

For the A320, Special Conditions were identified for Electronic (Fly-By-Wire) Flight Controls, Active Controls (for Load Alleviation), Engine Controls and Monitoring (for Full Authority Digital Engine Control (FADEC) and for non-moving thrust levers), Protection from Lightning and Unwanted Effects of Radio Frequency (RF) Energy, and for Flight Characteristics, Flight Envelope Protection, Side Stick Controllers, and Flight Data Recorder. As an example, the FAA Special Condition relevant to the Indian Airlines Flight 605 A320 accident was with regards to the non-movable throttle levers in the Engine Controls and Monitoring Special Condition.

Decisions made by the FAA in validation of the A320 type design were similar or identical to the earlier certifying authorities. During the development of this special condition, the subject of non-moving throttles was addressed, and commented on by the public. Similar comments were made by the Indian Court of Inquiry during the flight 605 accident investigation.

  • "One commenter recommends that the thrust levers should move corresponding to autothrust commands ....." (to) "provide adequate cues for the flightcrew to monitor thrust changes during normal operation * * * ". ....... "The FAA does, not agree, however, that the thrust levers would necessarily have to move during autothrust operation, provided the same (or greater) degree of information feedback regarding thrust commands is being provided to the crew. It is the intent of this special condition to require a satisfactory degree of monitoring capability to be incorporated in the design in order to compensate for the lack of thrust lever motion during autothrust operation."
  • "One (commenter) recommends that the ATS (Autothrust System) system should provide thrust lever motion at flight phases below 1500 feet above ground level (AGL) because this is where current autothrottle systems are most effective and important in providing tac" feedback to the pilot through movement of the thrust levers. The FAA agrees that takeoff, approach, and landing are especially important flight phases to be considered in assessing the effectiveness of the ATS command cues, as well as the ease and effectiveness of the disconnect. The FAA does not agree, however, that this may only be accomplished by means of physically moving the thrust levers. The special condition has been reworded to make it more clear as to the objectives of monitoring and override capability, and a new paragraph (5) has been added to address takeoff, approach, and landing.

The final wording for the Non-Movable Throttle Lever section of the Engine Controls and Monitoring Special Condition is as follows;
“(b) Engine Thrust Levers During Autothrust System Operation. In lieu of compliance with § 25.1143(c) of the FAR, it must be established by analysis and test that the A320 automatic thrust system:

  1. Provides adequate cues for the flightcrew to monitor thrust changes without the need for exceptional diligence during normal operation and provides capability for the flightcrew to recognize a malfunction or inappropriate mode of operation and take corrective action without the need for exceptional skills.
  2. Provides a means for the flightcrew to disengage or otherwise override the automatic thrust system and regain manual control of engine thrust through normal motion of the thrust levers as defined in § 25.779(b) of the FAR.
  3. Provides visual cues for any disengagements, and provides visual and aural alerts during uncommanded disengagements.
  4. Functions reliably and does not allow the exceedance of any approved engine operating limit during normal system operation.
  5. Compliance with paragraphs 1 through 3 above shall include consideration of faults within the automatic thrust system which could affect any or all engines during critical flight operations, such as takeoff, approach and landing.”

The entire text of the FAA Special Condition is available at the following link:

(A320 Special Condition

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