Tue, Sep 06, 2011
Revised AD, Effective September 5th, Is Considered To Be An
Interim Measure
EASA has modified an emergency AD that had grounded most
Dassault Falcon 7X airplanes. The revision outlines the steps
required to restore the full original certified flight envelope of
the airplane.
In May 2011, a Dassault Aviation Falcon 7X airplane experienced
an uncontrolled pitch trim runaway during descent. The crew
succeeded in recovering a stable situation and performed an
uneventful landing. The results of the investigations showed that
there was a production defect in the Horizontal Stabilizer
Electronic Control Unit (HSECU) which could have contributed to the
cause of the event. EASA issued the emergency AD because the
condition, if not corrected, could lead to a loss of control of the
airplane.
To address this unsafe condition, EASA issued emergency AD
2011-0102-E which prohibited further flights. Following further
technical investigations accomplished by Dassault Aviation, EASA
issued AD 2011-0114, currently at revision 2, which superseded EASA
AD 2011-0102-E. Following accomplishment of all the actions as
required by EASA AD 2011-0114R2, all airplanes could resume flying
with operational limitations.
Since EASA AD 2011-0114R2 was issued, Dassault Aviation
developed a modification (M1245 to be embodied through
accomplishment of Dassault Aviation Service Bulletin F7X-214) of
the Fly-By-Wire (FBW) current standard which improves the
monitoring and reversion logic of the Horizontal Stabilizer Trim
System (HSTS). This modification results in earlier failure
detection and quicker reversion.
Dassault Aviation also issued Revision 13 of the Aircraft Flight
Manual (AFM) which incorporates the changes introduced in EASA AD
2011-0114R2 (CP55 and 56) as well as the new changes resulting from
Dassault Aviation M1245 (CP58). Dassault Aviation introduced as
well operational tests of the HSTS electric motors reversion relays
and of the HSTS trim emergency command into the Chapter 5.40 of F7X
Aircraft Maintenance Manual (CP010).
For the reasons described above, this AD requires:
- Accomplishing Dassault Aviation modification (M1245).
- Amending the AFM.
- Implementing the operational tests of the HSTS electric motors
reversion relays and of the HSTS trim emergency command.
According to EASA, accomplishment of all the above actions
restores the full original certified flight envelope of the
airplane. However, this AD revision is still considered to be
an interim measure. EASA says that, pending results of the ongoing
analysis, further AD action may follow to restore the full original
certified MEL for airplanes fitted with FBW standard 2.1.7.3.
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