U.S. Department of Transportation

**Federal Aviation Administration**

+------+------------------------------------------+------+-----------+
| Subj | ACTION: Engine Inoperative Ten Minute    | D    | August    |
| ect: | Takeoff Thrust/Power Rating (Revision to | ate: | 19, 1994  |
|      | 6/28/94 Memorandum)                      |      |           |
+------+------------------------------------------+------+-----------+
| F    | Manager Transport Airplane Directorate,  | R    |           |
| rom: | ANM-100                                  | eply |           |
|      |                                          | to   |           |
|      | Manager Engine and Propeller             |      |           |
|      | Directorate, ANE-100                     | A    |           |
|      |                                          | ttn. |           |
|      |                                          | of:  |           |
+------+------------------------------------------+------+-----------+
| To:  | Manager, Small Airplane Directorate,     |      |           |
|      | ACE-100                                  |      |           |
|      |                                          |      |           |
|      | Manager, Aircraft Engineering Division,  |      |           |
|      | AIR-100                                  |      |           |
|      |                                          |      |           |
|      | Manager, Rotorcraft Directorate, ASW-100 |      |           |
|      |                                          |      |           |
|      | All Managers, Aircraft Certification     |      |           |
|      | Offices                                  |      |           |
+------+------------------------------------------+------+-----------+

***The original version of this memorandum was issued June 28, 1994, and
addressed only turbojet engines. The memorandum is now revised to
include turbopropeller engine installations.***

The Joint Aviation Requirements (JAR) allow the use of takeoff
thrust/power for up to ten minutes after the shutdown or failure of one
or more engines. However, Part 1 of the Federal Aviation Regulations
(FAR) defines rated takeoff thrust/power as limited to five minutes of
operation. At some airports (mostly foreign) the maximum allowable
airplane takeoff weight is limited by the climb gradient capability (at
maximum continuous thrust/power) needed to clear distant obstacles after
takeoff. The availability of takeoff thrust/power for use up to ten
minutes enables some foreign operators to dispatch at an increased gross
weight relative to U.S. operators under these conditions. U.S. operators
have expressed a desire to be treated equally in similar circumstances
in order to be competitive.

The Transport Standards Staff has reviewed Part 25 and determined that
no revisions are needed to provide the flexibility for an engine
inoperative \"10-minute\" takeoff thrust/power rating. The limiting
phrase is found in Part 1 in the definition of rated takeoff
thrust/power. The Engine and Propeller Standards Staff is proposing a
regulatory change to Part 1 to harmonize the FAR with the JAR. The
proposed wording would extend the current definition of rated takeoff
thrust/power for turbine engines in Part 1 as follows:

*\". . . and limited in use to periods of not over 5 minutes for takeoff
operation, and, for turbojet (including turbofan) and turbopropeller
engines, when specifically requested by the engine type certificate
holder, to periods of not over 10 minutes for engine inoperative takeoff
operations.\"*

The Engine and Propeller Directorate has verified that the engine
inoperative \"10-minute\" rating is well within the boundaries of the
engine certification standards of Part 33 for turbine engines.

Since the Part 1 definition is not limiting with respect to ratings
selected by the engine manufacturer for abnormal operations, we have
adopted the following procedure to allow the FAA approved transport
category Airplane Flight Manual (AFM) to be revised to incorporate
instructions regarding the engine inoperative \"10-minute\" takeoff
thrust/power rating for airplanes with turbine engine installations.
Upon receipt of a written request from an applicant seeking an engine
inoperative \"10-minute\" takeoff thrust/power rating the following
items will be addressed:

a\. The engine type certificate holder shall request in writing to the
cognizant aircraft or engine certification office for approval of an
engine inoperative \"10-minute\" takeoff thrust/power rating for the
relevant turbine engine models.

b\. The aircraft or engine certification office shall ensure that the
relevant engine type certification data sheet is revised to note the
extended turbine engine rating.

c\. The transport category airplane type certificate holder shall
request in writing to the cognizant Aircraft Certification Office (ACO)
the desire to establish the engine inoperative \"10-minute\" takeoff
thrust/power rating for the relevant airplane/engine model(s). The
request should include the engine type certificate holder\'s
\"endorsement\" of the extended turbine engine rating.

d\. The transport category airplane type certificate holder shall
present the appropriate AFM revisions concerning the engine inoperative
\"10-minute\" takeoff thrust/power operation to the ACO for

review and approval.

e\. The ACO shall ensure that the relevant airplane type certification
data sheet is revised to note the extended turbine engine rating.

The engine inoperative \"10-minute\" rating operation should be
processed as an engineering approval unless there are actual hardware
changes. The AFM revision should specify that using takeoff thrust/power
for more than five minutes (not to exceed ten minutes) is approved for
use only in the event of an inoperative engine(s) due to shutdown or
failure. The AFM obstacle clearance charts (see §§121.189(d) and
135.379(d)) should be revised to reflect the increased climb capability.

This interim procedure, which is available upon request, may be used to
provide the additional obstacle clearance capability for U.S. operators
. When the Part 1 amendment is effective the normal certification
procedures will apply.

  ----------------------------------- ----- ------------------------------
  s/ RTW                                    s/ JJP

  Ron T. Wojnar                             Jay J. Pardee
  ----------------------------------- ----- ------------------------------

Distribution:

Manager, Aircraft Certification Service, AIR-100

Manager, Engine and Propeller Directorate, ANE-100

Manager, Engine Certification Office, ANE-140

Manager, Boston Aircraft Certification Office, ANE-150

Manager, New York Aircraft Certification Office, ANE-170

Manager, Rotorcraft Directorate, ASW-100

Manager, Airplane Certification Office, ASW-150

Manager, Rotorcraft Certification Office, ASW-170

Manager, Special Certification Office, ASW-190

Manager, Atlanta Aircraft Certification Office, ACE-115A

Manager, Small Airplane Directorate, ACE-100

Manager, Wichita Aircraft Certification Office, ACE-115W

Manager, Chicago Aircraft Certification Office, ACE-115C

Manager, Seattle Aircraft Certification Office, ANM-100S

Manager, Los Angeles Aircraft Certification Office, ANM-100L

Manager, Brussels Aircraft Certification Staff, AEU-100