Federal Aviation
Administration

MMEL Policy Letter (PL) 72, Revision 4 GC

Date:

March 12, 2012

To:

All Region Flight Standards Division Managers
All Aircraft Evaluation Group Managers

From:

Manager, Air Transportation Division, AFS-200

Reply to Attn of:

Manager, Technical Programs Branch, AFS-260

 

MMEL GLOBAL CHANGE (GC)

This is an approved addendum to all existing MMEL documents.  The operator may seek use of the specific relief contained in the PL by revising the Minimum Equipment List (MEL).  In doing so, the applicable sample proviso stating the relief in this PL must be copied verbatim in the operator’s MEL.  Approval of the MEL is gained utilizing established procedures, through the assigned Principal Operations Inspector (POI).  This GC expires 3/12/2016.

SUBJECT:

Wing Icing Detection Lights

MMEL CODE:

33 (LIGHTS)

REFERENCE:

PL-72, Revision 3, dated March 24, 2008

PL 72, Revision 2, dated August 15, 1997

PL 72, Revision 1, dated July 31, 1995.

PURPOSE:

To provide standardized Master Minimum Equipment List (MMEL) requirements for Wing Icing Detection Lights.

DISCUSSION:

Revision 4 clarifies relief available for wing icing detection lights within the regulatory guidelines of 14 CFR.  This revision designated a GC.

Revision 3 deletes the Global Change designation of GC-54 from this Policy Letter and revises FOEB Chairman guidance statement.

Revision 2 cancels and replaces the following Policy Letters:

Master Minimum Equipment List, Policy Letter 37, dated September 15, 1993, Subject: Relief for Wing/Illumination Ice Lights.

Master Minimum Equipment List, original Policy Letter 72, dated December 16, 1993, Subject: Cargo Aircraft Ice Lights Relief.

1.  Wing icing detection lights are used for visual ice detection on critical wing surfaces by flightcrews.  Adequate external lighting for visual detection of ice at night is a requirement for part 23 certificated aircraft.  Part 25 aircraft must have wing icing detection lights or some other means to detect icing conditions on critical wing surfaces.

2.  Many of today’s modern aircraft, both part 23 and part 25, contain wing icing detection lights, advisory and primary ice detection systems, and ice protection systems (IPS); all used for the detection of, and protection from, the accumulation of ice on the aircraft.  Advisory ice detection systems advise the flightcrew of the presence of ice accumulation.  Advisory systems normally require manual IPS activation.  Primary ice detection systems determine when the ice protection system must be activated and may be manual or automatic in activating the IPS.  Because advisory systems are less reliable than primary systems, advisory systems must be used in conjunction with visual observation by flightcrews.

3.  Flightcrews visually monitor ice accretion from the flight deck, however, on some aircraft, crews cannot view the wing from the flight deck due to the wing’s sweep angle.

4.  Although some aircraft are equipped with other ice detection systems that meet the regulatory requirements, some ground de-icing procedures may require the use of the wing icing detection lights during ground de-icing operations.

 

POLICY:

Wing icing detection lights provide illumination for viewing critical wing surfaces which should be monitored under certain conditions. These lights should be operative for night operations on those aircraft where the wing surface can be effectively viewed from the flight deck.  For those configured aircraft which preclude a view of critical wing surfaces from the flight deck, and/or those aircraft that incorporate primary ice detection systems, the wing icing detection lights may be inoperative provided ground deicing procedures do not require their use.

The following MMEL provisos and repair categories are adopted for items entitled “Wing Icing Detection Lights”, or equivalent, on passenger and cargo aircraft.

Note:  In some MMELs, wing icing detection lights are also referred to as wing illumination lights, wing inspection lights, or wing ice lights.

 

AIRPLANES WITH WING CRITICAL SURFACES NOT VISIBLE FROM FLIGHT DECK

33  (LIGHTS)

Repair Interval

Number Installed

Number Required for Dispatch

Remarks or Exceptions

33-X

Wing Icing Detection Lights

C

2

0

May be inoperative provided ground deicing procedures do not require their use.

AIRPLANES WITH WING CRITICAL SURFACES VISIBLE FROM FLIGHT DECK

(EQUIPPED WITH PRIMARY ICE DETECTION SYSTEM)

 

33-X

Wing Icing Detection Lights

   C

   2

0

May be inoperative provided:

a)        Primary Ice Detection system is operative, and

b)        Ground deicing procedures do not require their use.

 

 

 

 

 

 

 

AIRPLANES WITH WING CRITICAL SURFACES VISIBLE FROM FLIGHT DECK

(NOT EQUIPPED WITH PRIMARY ICE DETECTION SYSTEM)

 

33  (LIGHTS)

 

Repair Interval

Number Installed

Number Required for Dispatch

Remarks or Exceptions

 

33-X

Wing Icing Detection Lights

         C     

2

0

May be inoperative provided:

a)    Aircraft is not operated in known or forecast icing conditions at night, and

b)    Ground deicing procedures do not require their use.

 

 

C

2

1

One may be inoperative provided:

a)  The left light is operative for single pilot operations, and

b)  Ground deicing procedures do not require their use.

 

Each Flight Operations Evaluation Board (FOEB) Chairman should apply this Policy to affected MMELs through the normal FOEB process.

 

 

 

 

 

        /s/ Greg Kirkland for

John S. Duncan

Manager, Air Transportation Division