As temperatures drop and winter weather systems move in, the first snow is always a good reminder for aircraft owners who haven’t already done so to give some thought to winter aircraft maintenance. And today's topic: windshield heat system check. Ensuring your windshield heating system is in good working order to provide the heat needed to keep your windshield clear is an imperative for cold weather flying.
This is true for any aircraft you intend to fly for your cold weather missions, but every system is a bit different so it’s important to work with your aircraft maintenance team to understand your particular system and ensure it is in good working order.
In this article we’ll focus on some tips from Ed Novak, our vice president of maintenance and a Piper aircraft expert, that you can use to check your (post-1988) PA46 M-Class aircraft for signs of wear to help you determine if and when maintenance may be required.
Unlike your aircraft propeller deice system, which has a current monitor that will illuminate an annunciator on the instrument panel to indicate heat failure if the system fails to draw sufficient current, the windshield heat system has no such device. The windshield heat system does include an ‘overheat’ annunciator, but this is rarely activated as the typical failure mode of the windshield heat system is a lack of heat rather than too much.
Surprisingly, even the pneumatic deice system for your Piper’s deicer boots has a monitoring system that will indicate whether or not the system is working properly. But at the present time, the only way for you to know if the windshield heat system is working properly is to know what the windshield heat current draw should be and then periodically check these numbers to see if they are correct for your system.
A properly functioning windshield heat system will generally draw about 18-19 amps on the “Defog” setting (over and above the draw for other equipment in use) and 24-25 amps on the “Anti-ice” setting (over and above the draw for other equipment in use). Anything less than these values typically indicates inoperative heating elements within the windshield.
The photograph to the right shows a window that draws 15 amps on the “Defog” setting, rather than 19 amps. The same window also draws only 19 amps on the “Anti-Ice” setting, rather than 24 amps. Indeed, the inoperative heating elements are plainly visible in this case.
Although the window in this example may keep clear for the time being, these issues are an indication that close monitoring of the current draw is needed to ensure the problem does not progress to a stage when there are no longer enough functioning heating elements to sufficiently clear the windshield in icing conditions.
That’s the wrong time to discover your windshield heat is not working!
Ed Novak has been the Director of Maintenace at Shoreline Aviation since 1987. He has over thirty years of technical experience on a wide range of turbojet, turboprop and piston models, including Cessna Citation jets, Diamond Aircraft and many others. Shoreline Aviation has been an authorized Piper Service Center since 1995 and Ed and his team of technicians are experts on all Piper models.
Have a maintenance question for Ed? Contact him at (781) 834-4928 or email email@example.com