B747 captain experiences pneumatic leading edge flap-drive failure on approach. Secondary (electric ...

Narrative:

[We had a] pneumatic leading edge flap-drive failure. On approach; during flap extension; received flaps primary and le single drive EICAS messages. Slight yaw and bank experienced; followed by EICAS display. Captain was able to visually confirm left outboard leading edge devices (leds) had not extended. Secondary (electric motor) mode successfully extended leds; followed by normal EICAS display; and slight yaw which had been induced was removed. Trailing edge flap operation was normal. Once secondary mode had extended leds; remainder of approach was uneventful with normal configuration. After landing; all flaps appeared to retract normally. [We] debriefed with mechanic on arrival. The irregular procedure action items deal with trailing edge flap (tef) operation in secondary mode. Time for flap operation was not applicable to our situation. Suggest splitting action items into two parts; trailing edge with the present applicable time delays; and leading edge with time required for led extension (unless accompanied by tef in secondary mode; once the leds are extended the remainder of flap operation will be normal). I do not believe the 160 KT speed restriction is applicable with only a leading edge drive in secondary control mode.

Original NASA ASRS Text

Title: B747 Captain experiences pneumatic leading edge flap-drive failure on approach. Secondary (electric motor) mode successfully extended LED's; followed by a normal landing.

Narrative: [We had a] pneumatic leading edge flap-drive failure. On approach; during flap extension; received FLAPS PRIMARY and LE SINGLE DRIVE EICAS messages. Slight yaw and bank experienced; followed by EICAS display. Captain was able to visually confirm left outboard Leading Edge Devices (LEDs) had not extended. Secondary (electric motor) mode successfully extended LEDs; followed by normal EICAS display; and slight yaw which had been induced was removed. Trailing edge flap operation was normal. Once secondary mode had extended LEDs; remainder of approach was uneventful with normal configuration. After landing; all flaps appeared to retract normally. [We] debriefed with mechanic on arrival. The Irregular Procedure Action items deal with Trailing Edge Flap (TEF) operation in secondary mode. Time for flap operation was not applicable to our situation. Suggest splitting action items into two parts; trailing edge with the present applicable time delays; and leading edge with time required for LED extension (unless accompanied by TEF in secondary mode; once the LEDs are extended the remainder of flap operation will be normal). I do not believe the 160 KT speed restriction is applicable with only a leading edge drive in secondary control mode.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	991095
Time
Date	201201
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.TRACON
State Reference	US
Aircraft 1
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Component
Aircraft Component	Leading Edge Flap
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 104 Flight Crew Total 17640 Flight Crew Type 4400
Events
Anomaly	Aircraft Equipment Problem Less Severe

B747 captain experiences pneumatic leading edge flap-drive failure on approach. Secondary (electric motor) mode successfully extended led's; followed by a normal landing.