Federal Aviation

MMEL Policy Letter 90, Revision 1


Sept 20,2001


All Region Flight Standards Division Managers
All Aircraft Evaluation Group Managers


Manager, Air Transportation Division, AFS-200

Reply to Attn of:

Manager, Technical Programs Branch, AFS-260


Pitot Heat Indicating System




PL-90, Original, dated Aug 15, 1998

PL-8 (Item 3), FOEB Minutes, dated Jul 12, 1982


The following policy provides standardized Master Minimum Equipment List (MMEL) relief for the Pitot Heat Indicating System.




Revision 1 clarifies the policy letter intent by specifically addressing non-transport category airplanes used in operations other than Title 14, Code of Federal Regulations (14 CFR) part 121.  This policy letter also restates an earlier MMEL policy that was previously contained in PL-8 (item 3) dated July 12, 1982, which covered multiple issues.


14 CFR section 25.1326 requires a Pitot Heat Indicating System for all transport category airplanes that have a flight instrument pitot heating system installed. 14 CFR sections 121.342, 125.206, and 135.158 repeat that requirement for transport category airplanes.  Additionally, 14 CFR section 121.342 was revised in 1996 to require non-transport aircraft operated under 14 CFR part 121 to also have a Pitot Heat Indicating System. This has created situations where some non-transport airplanes have been equipped with Pitot Heat Indicating Systems for the purpose of operating under 14 CFR part 121 but their operators desire the flexibility of operating those airplanes under 14 CFR part 135 (i.e. all cargo operations and/or non-scheduled passenger carrying) which do not require that a Pitot Heat Indicating System be installed.


The Flight Operations Evaluation Board (FOEB) should adopt the following policy for the MMEL item concerned with 14 CFR sections 121.342, 125.206, and 135.158. The FOEB chairmen should review the following for extended range approved operations for two-engine airplanes and modify as appropriate for compliance with PL-40.


When the certification or operating rules require a Pitot Heat Indicating System, the repair interval shall be a category B with none required provided all other elements of the pitot heat system operate normally and the airplane is not operated in known or forecast icing conditions. When a Pitot Heat Indicating System is

not required by the certification or operating rules, the repair interval will be category C.

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


Louis C. Cusimano, Manager,

Air Transportation Division, AFS-200



PL-90, R 1 reformatted 01/20/2010 with no change in content.