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technical investigations accomplished by Dassault Aviation, EASA issued AD 2011-0114, currently at revision 2, which superseded EASA AD 2011-0102-E. Following accomplishment of all the actions as required by EASA AD 2011-0114R2, all airplanes could resume flying with operational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.

FMI: www.easa.europa.eu