Windshield cracking and electrical arcing due to loose windshield heater electrical terminal - Civil Aviation Safety Alerts (CASA) No. 2012-01

Owners, operators and maintainers of aircraft with electrically heated windshields

Issuing Office: National Aircraft Certification Branch
Document No. : CASA -2012-01
File Classification No. : Z 5000-35
Issue No. : 01
RDIMS No. : 5317873
Effective Date: 2012-06-07


To inform Owners and Maintainers of safety concerns regarding the loss of, or improper torque values of heated windshield electrical terminal connections and to advise of incidents in which the windshield heater connectors overheated, causing smoke in the cockpit.


The Service Difficulty Report ( SDR ) database as well as daily incident reporting programs, indicate that the issue of windshield failure due to overheated windshield heater terminals is not uncommon. Transport Canada Civil Aviation ( TCCA ) believes many of these overheat conditions may be, in part, due to inadequate or a loss of torque on the windshield heat terminal hardware. Many existing maintenance programs require the inspection of these connectors as part of a zonal inspection, albeit carried out at fairly lengthy intervals. Many of these failures resulted in smoke, sparks or flame in the cockpit and unscheduled landings.

Recommended action:

TCCA recommends that owners and maintainers inspect the windshield heater terminal block connections for security, overheating and wire routing by performing a Detailed Inspection of the terminals and ground studs to ensure that the parts are not loose and that there are no visible signs of overheating or discoloration. It is also recommended that the attaching hardware at the terminals be re-torqued to the value specified by the airframe manufacturer.

Many aircraft maintenance programs currently use MSG-3 defined tasks. Under such programs, a Detailed Inspection would include a tactile check of the wiring connector attachment to the windshield terminal for looseness. For those aircraft without such guidance material, standard practices are to be followed.

Operators may use findings as a result of this inspection to revise their inspection program requirements to preclude such failures.

Defects, malfunctions and failures occurring on aeronautical products are to be reported to Transport Canada, Continuing Airworthiness in accordance with CAR 521 mandatory Service Difficulty Reporting requirements.

Contact office:

For more information contact a Transport Canada Centre; or Paul Jones, Continuing Airworthiness, Ottawa, at 613-952-4357, facsimile 613-996-9178, or e-mail

For the electronic version of this document, please consult the following Web address

For the Director, National Aircraft Certification


Derek Ferguson
Chief, Continuing Airworthiness

The Transport Canada Civil Aviation Safety Alert ( CASA ) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.