Remarks: Where applicable, the requirements of this AD must be integrated into the Aircraft's Logbook(s). Address inquiries concerning this AD to: Civil Aviation Authority, Airworthiness Division, Airport Ruzyne, 160 08 Prague 6, Czech Republic, tel.: 420 2 33320922, fax: 420 2 20562270.

DGAC AD ref.: 1999-166-041(B) R1
ATR 72 Airplane
Severe icing conditions- Implement aircraft design enhancements (ATA 30)

1. APPLICABILITY:
Airplane ATR 72, model -101, -102, -201, -202, -211, -212, -212A.

Accumulated experience on the worldwide fleet of commuter aircraft, and a recently reported in-flight incident, lead to recall that a prolonged exposure to severe icing conditions, outside the certification envelope, can lead to performance degradation and to stall.

The reason for prolonged exposures to such severe icing conditions are late detection of these conditions and/or non or late application of the AFM, which require the immediate exiting of the severe icing conditions as soon as detected.

Compliance with the previously mandated procedures is therefore essential for the safety of flight.

However, it is recognized that, even if the exit maneuver is initiated rapidly after detection, it may take a few minutes before the airplane is out of the severe icing conditions.

Consequently, DGAC acting as the primary authority for the ATR program, has mandated a first measure which has been to increase by l0kt the minimum maneuver/operating icing speeds when severe icing is detected. This was mandated by AD No.1999-O15-040(B).

Furthermore, it has been recorded that, in several occurrences, crews have failed to activate the deicing boots, despite the fact that ice accretion had been detected by the Anti-icing Advisory System.

This has led ATR to develop an enhancement of the alerting capability of the AAS system. The modification implementing this enhancement is mandated by this AD.

As part of its continual efforts to enhance safety, ATR has designed extended median boots which further enhance the aircraft's performance in case of prolonged severe icing encounters. In addition, since it is DGAC policy to avoid relying only on procedures to address safety issues, the modification implementing this design change is mandated by the present AD.

Revision 1 of this AD is issued in order to take into account revisions of references Service Bulletins without modifying the technical content of this AD.

3.1. Reinforce crew awareness and vigilance by embodying AEROSPATIALE modification No. 5008 "modification of the ICING light flashing logic" in accordance with Service Bulletin ATR 72-30-l034.

3.2. For airplanes on which AEROSPATIALE modifications No. 4994 and 4997 have not been accomplished : replace the median wing boots by extended boots and install boots on the metallic leading edge by embodying AEROSPATIALE modification No. 8210 and No. 8212 or No. 8241 in accordance with Service Bulletin ATR72-30-1032 revision 1 and ATR72-30-7033 revision 1 or ATR72-30-1037.

Note : the requirements of paragraphs 3.1 and 3.2 can be accomplished separately.

The requirements of paragraphs 3.1 and 3.2 must be accomplished at the first opportunity and no later than September 30th, 200l.

Remark Inquiries regarding the technical content of this Airworthiness Directive should be made to DGAC/SFACT/N-AT, tel. : 33.1.41.09.48.79, fax : 33.1.41.09.43.19.

REF.: Service Bulletin ATR72-30-l034
Service Bulletin ATR72-30-1032R1
Service Bulletin ATR72-30-1033R1
Service Bulletin ATR72-30-l037

Any further revision of these Service Bulletins is acceptable.

This revision 1 replaces AD 1999-166-041(B) issued on April 21, 1999.

EFFECTIVE DATES:
Original AD: MAY lst l999
Revision 1: JULY 22, 2000