**Exemption No. 4385A**

**UNITED STATES OF AMERICA**

**DEPARTMENT OF TRANSPORTATION**

**FEDERAL AVIATION ADMINISTRATION**

**SEATTLE, WASHINGTON 98168**

**In the matter of the petition of**

**AEROSPATIALE Regulatory Docket No. 006NM**

**for an exemption from § 25.571(e)(2)**

**of the Federal Aviation Regulations**

**GRANT OF EXEMPTION**

**By letter dated May 31, 1989, Mr. D. Berger, ATR Chief Engineer,
Societe Nationale Industrielle Aerospatiale, 316, Route de Bayonne,
31060 Toulouse Cedex 03, France, petitioned for an amendment to
Exemption 4385 to permit type certification of the Model ATR 72 without
showing that the airplane is capable of successfully completing a flight
during which likely structural damage occurs as a result of propeller
blade impact. Exemption 4385 was granted on April 19, 1984, to permit
such type certification of the earlier Model ATR 42. (The exemption was
originally identified as Exemption NM-104; however, it was subsequently
reidentified as Exemption 4385 for administrative convenience.)**

**The Model ATR 72, which is being developed jointly with Aeritalia of
Italy, is a derivative of the earlier Model ATR 42. Like its forebear,
it is a pressurized, high-wing transport powered by two turbopropeller
engines. Although the fuselage is seven feet greater in length to
accommodate as many as 74 passengers, it too is of metal construction
and utilizes construction methods that are similar to those of the Model
ATR 42. Like those of the Model ATR 42, the propeller blades of the
Model ATR 72 incorporate metal spars with composite outer shell
construction.**

**Aerospatiale has applied for type certification of the Model ATR 72 by
the airworthiness authorities of France under the provisions of Joint
Airworthiness Requirements - 25 (JAR-25)1 and by the Federal Aviation**

**\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_**

**1JAR-25 is a document developed jointly and accepted by the
airworthiness authorities of various European countries, including
France, for the type certification of large airplanes. JAR-25 is based
on Part 25 of the FAR; however there are certain specified differences
in the requirements of the two documents.**

**ANM-89-016-E**

**Administration (FAA) under the provisions of § 21.29 of the Federal
Aviation Regulations (FAR) and an existing bilateral agreement with the
government of France. Like that of the Model ATR 42, the U.S. type
certification basis for the Model ATR 72 consists of Part 25 of the FAR,
with Amendments 25-1 through 25-54 thereto; Part 36 of the FAR, with
Amendments 36-1 through 36-12 thereto; Special Federal Aviation
Regulation No. 27; and any necessary special conditions.**

**Section of the FAR affected:**

**Section 25.571(e)(2), which was introduced by Amendment 25-45,
effective December 1, 1978, specifies that the airplane must be capable
of successfully completing a flight during which likely structural
damage occurs as a result of propeller blade impact (or as a result of
uncontained fan blade impact for a turbofan powered airplane). The
requirements of § 25.571(e)(2) are based on the assumption that a
propeller blade will fail and therefore allow no relief based on
improbability of blade failure. Similarly, the requirements of**

**§ 25.571(e)(2) allow no relief based on the possibility that the blade
will not impact the structure. The wording of § 25.571(e)(2), together
with the preamble to Amendment 25-45, clearly indicates that the rule is
concerned only with structural damage due to impact of the failed
propeller blade. By omission, other hazards, such as damage to vital
systems or structural damage due to severe powerplant imbalance, are not
addressed by § 25.571(e)(2).**

**Compliance with § 25.571(e)(2) has not been required for any
turbopropeller airplane to date. Saab-Scania AB, Empresa Brasileira de
Aeronautica (Embraer), de Havilland of Canada, Construcciones
Aeronauticas SA (CASA), and British Aerospace have been granted
Exemptions 3469, 3722, NM-102, NM-103, and 4812, respectively; and, as
noted above, Aerospatiale has been granted Exemption 4385 for their
Model ATR 42. As in the case of the Model ATR 42, Aerospatiale has
proposed to show compliance of the Model ATR 72 with the following in
lieu of § 25.571(e)(2):**

**All practical precautions must be taken to minimize the hazards to the
airplane in the event of propeller debris release.**

**Although differing somewhat in wording, this proposal is identical in
substance to that of each of the other five petitioners.**

**The petitioner\'s supportive information in regard to the Model ATR 72
is as follows:**

**In support of the request, the petitioner states that the supportive
information submitted by their letter of February 29, 1984, for
Exemption 4385 remains valid and applicable to the Model ATR 72.**

**This information, which is presented in detail in Exemption 4385,
presents reasons why, in the petitioner\'s opinion, safety of the Model
ATR 42 would not be compromised by granting the requested exemption and
doing so would be in the U.S. public interest.**

**Summaries of the Saab-Scania, Embraer, and de Havilland of Canada
petitions for similar exemptions were published in the *Federal
Register*, affording interested persons the opportunity to participate
in the rulemaking process by providing comments on each petition. No
comments were received concerning either of the last two of those
petitions. Because the reasons presented for the CASA petition were
identical in substance to those presented for each of the three earlier
petitions for which the public was afforded full opportunity to comment
and because granting that petition would not set a precedent, the FAA
determined that publication and comment procedures were unnecessary for
the CASA petition and the subsequent Aerospatiale and British Aerospace
petitions for similar relief. The FAA has determined that publication
and comment procedures for this petition are unnecessary for the same
reasons.**

**The FAA analysis/summary is as follows:**

**For reasons discussed in detail in Exemption 4385 for the earlier
Model ATR 42, the FAA determined that it would be virtually impossible
to assure literal compliance with § 25.571(e)(2) with any economically
viable, propeller-driven airplane and that literal compliance with that
section would impose an extreme burden without providing a commensurate
improvement in safety. On the other hand, compliance with the proposed
alternative would, in some respects, result in a higher level of safety.
For reasons also discussed in detail in Exemption 4385, the FAA
determined that the granting of that exemption would be in the U.S.
public interest. The conclusions reached in regard to the Model ATR 42
are all equally applicable to the new Model ATR 72.**

**In consideration of the foregoing, I find that amending Exemption 4385
to include the Model ATR 72, as well as the Model ATR 42, would not
adversely affect safety and is in the public interest. Therefore,
pursuant to the authority contained in Sections 313(a) and 601(c) of the
Federal Aviation Act of 1958, as amended, delegated to me by the
Administrator, Aerospatiale is hereby granted an amended exemption from
§ 25.571(e)(2) of the Federal Aviation Regulations to the extent
required to permit type certification of the Models ATR 42 and ATR 72
without showing that the airplanes are capable of successfully
completing flight during which likely structural damage occurs as a
result of propeller blade impact, provided the petitioner shows
compliance with the following in lieu thereof:**

**All practicable precautions must be taken to minimize the hazards to
the airplane in the event of propeller debris release.**

**Issued in Seattle, Washington, on**

**F:\\HOME\\PLS\\RULES\\ATR-EXM**

**Typed:glk:10/30/89**

**Editorial Revisions:pls:10/31/89**