SL 1204 and the PA46 Windshield

You know the old joke…”What’s the landing light used for in a single-engine airplane with an engine failure at night?”  Answer: “You turn it on when you near the ground…if you don’t like what you see, turn it off!”  A weird parallel can be made with the windshield heat and the PA46.

Suffice it to say, the Windshield Heat situation on the PA46 has evolved into a real mess.  Without a doubt, the operation of the windshield heat has been the “elephant in the room” on just about every purchase/sale of every PA46 for as long as I can remember, but now Piper recently released Service Letter 1204 which was supposed to clear up the muddy water.  Well, it arguably cleared up the water for there’s now little doubt about the condition of a windshield.  But where we can now clearly see, few are liking what they see.  And, we cannot “turn off” SL 1204.  We are going to have to live with SL 1204 and it’s going to cost money.  Let’s go back into history and discuss the windshield heat from day-one…

Nearly every PA46 in the fleet is FIKI (Flight Into Known Icing) equipped.  There are a few early Malibu’s and a few recent Matrix versions which did not come from the Piper factory with all of the icing systems (most non-FIKI PA46’s have no wing boots), but the VAST majority of PA46’s are FIKI-equipped.  In order to be FIKI-equipped, a PA46 must have (among other requirements) windshield heat.

The early Continental Malibu’s came from the factory with a Hot Plate.  I personally dislike the Hot Plate as it destroys the forward visibility of the pilot.  There are still plenty of 1984-1988 Malibu’s with the Hot Plate, and some of them still work, but many don’t.  Today, there’s no replacement or repair for the early Hot Plate, so if it fails the owner is left with the option of removing it from the airplane (and placarding the airplane with “Flight Into Known Icing Prohibited”) or upgrading to a Glass Windshield.

In 1989 Piper came out with the Mirage installed with a “Plexiglass Windshield”.  This windshield had lots of failures and became known as the windshield that “either worked really well” (and still works), or that would frequently experience “infant mortality”.  There are still some Plexiglass Windshields in the fleet, but there are fewer and fewer every year.

In 1995 Piper began installing the (currently used) “Glass Heated Windshield”. made by PPG.  This windshield is found on all PA46’s that come from the Piper Factory (Meridian, Mirage, Matrix) after 1995 and is the only windshield that can be purchased today.  So, if your Hot Plate windshield or your Plexiglass Windshield were to fail (and you want to be FIKI equipped), you will have to buy the Glass Windshield.

Before Service Letter 1204, to check the operation of the heated windshield (glass or Plexi), the POH for the PA46’s mandated that the amp draw be checked.  Basically, you’d make sure only one electrical source (one alternator or generator) is running and note the amp reading before and after turning on the windshield heat.  A new windshield should draw 19 amps on LOW and 24 amps on HIGH, but Supplement 2 of the POH advises a “preflight check” of the windshield be accomplished with the pilot seeking an amp draw above 13 greater in LOW and 23 in HIGH (See Section 9, Supplement 2 of the Mirage POH).  If it is less than 13, then it’d be in the “gray area” where lots of interpretation was required.  The windshield has lots of very small wires that act as heating elements embedded in the windshield.  When these wires get broken (for now unknown reasons), the electrons don’t flow across that portion of the windshield and the amp draw goes down.

To help clear up the confusion, Malibu Aerospace (led by Chad Menne) creatively began using infrared images to determine the operation of the windshield, and other maintenance shops and instructors (including me) followed their lead.  With an infrared camera it is VERY easy to see exactly where the windshield is heating and where it’s not heating.  I think the Infrared Camera is the BEST way to test the operation of a heated windshield. Although VERY subjective, if the amp draw was lower than 13, the pilot/owner/mechanic could use the Infrared Image decide if the windshield heated up enough area for the pilot to see in a icing event, or if the windshield required replacement.

The catch is that the windshield replacement is VERY expensive.  As of this writing, a new windshield costs $21k to purchase and the installation is laborious, often pushing total replacement cost up to $30k.  And…to add insult to injury, if the airplane is older, it is often prudent to replace the copilot windshield as well.  The CP windshield adds just a little more labor to replace both and if there are scratches on the co-pilot side, then the cost for an entire replacement can top $35k.  If you own an early “Hot Plate” Malibu and require replacement, then there’s more bad news…the wiring and windshield controller is different, there’s new switches to install, and new cockpit indications are required.  A Windshield replacement in an early Malibu can push $40k very quickly.  Bottom line…a windshield is expensive!

We’ve trudged on for years in the gray area with nearly all of the “quality” PA46 shops signing off annuals with “less-than-optimal” windshields because the Maintenance Manual does not offer any criteria for checking the Windshield Heat…it merely says to check to see that there was an amp draw…any amp draw.  Maintainers follow the guidance of the Maintenance Manual, not the POH when performing maintenance.  Most owners that live in the southern USA would ride along for years with windshields that would draw FAR fewer amps that was mentioned in the POH.  Most northern-based pilots that often flew IFR in the cold clouds would opt to have it replaced, as icing would be a frequent visitor in flight.

At sale, the wise buyer of any PA46 would include “Airworthiness Items” as a “seller-paid-item” in the Purchase Agreement.  If the amp draw was discovered to be less than 13 amps in the prebuy, the Buyer would press the Seller to buy a new windshield (this is the gray area).  That $30k “elephant in the room” would often result in hurt feelings, empty pocketbooks, and sometimes it would stop the sale entirely because that windshield was “in the gray area”.

In the Fall of 2016, Piper issued Service Letter 1204 to help “clarify” the Windshield Heat issue.  Basically, the resistance of the windshield is now tested with an ohm meter. Note, this is not a home-toolbox ohm meter found at your local Auto Zone…it’s a 4-terminal ohm meter that is highly accurate, required because of the low resistances being measured. And…make no mistake…the operation of the ohm meter should not be left to rookies.  There’s simply too many variables when testing such low resistances.  I suspect there will be LOTS of windshields replaced because dealing with such low resistances is tricky business…a corroded connector can move the needle over the line, for example.

But…assuming a mechanic knows what he’s doing, and reads with the right equipment…if the reading is within limits specified in the SL, then everything is OK.  If not, then the SL declares that the windshield “Must” be replaced.  Not “suggested”, not “should”…it says “Must”.  And, it advises that the POH and Maintenance Manual are to be revised to eliminate the discussion of the amp draw (but that has not happened as-of yet).

Here’s the kicker…SL’s are NOT mandatory.  Even though the SL uses the word “Must”, no owner/pilot MUST do anything that a SL illustrates.  If the FAA wants to mandate an action, they will issue an Airworthiness Directive (AD).  No AD has been issued on the PA46 windshield.  So, the SL is currently the best written guidance for a maintenance shop to use, but a responsible owner must carefully consider prudence when deciding to write that $30k-$40k check, and right now replacement is NOT mandatory if the windshield fails SL 1204.

My big issue with the new SL is that the allowable resistance range for what is an “acceptable windshield” is representative for a NEW windshield.  I’ve seen LOTS of windshields that had a slightly low (but decent) amp draws and looked just fine through an infrared camera, but would fail the resistance check.  If I owned a PA46 and planned to keep the airplane for a while, I’d view the windshield issue with a different lens…I’d consider the amp draw, check out infrared images, look at the resistance, and also consider where I lived and how often I anticipated needing the windshield.  In Texas, we need the windshield heat rarely…I can count the number of times I’ve turned on the Windshield Heat in the last decade on one hand.  But, anyone that operates anywhere defined as “northerly” probably uses the windshield heat frequently.  Again, prudence must be considered.

At sale though…there’s no holds barred.  If the Seller has been nursing a weak windshield for a few years, you can rest assured they do NOT want to pay $30k at sale.  And, consequently, the Buyer will be VERY interested in making sure the windshield works IAW Service Letter 1204.  Who will win?  Answer: whoever has the most knowledge and whoever CAREFULLY considers the verbiage of the legally-binding Purchase Agreement.

If an airplane is about to go on the market, I recommend a Seller consider the condition of the Windshield Heat closely and be prepared to discuss it PRIOR to signing the Purchase Agreement (PA).  If I were the Buyer, I’d want to know the condition of the windshield and also know the language of the PA.  If the windshield doesn’t work, then the Seller should disclose this early so that discussion can ensue.  If it absolutely does work, then this is a good selling point.  If the windshield is going to be in a “gray area”, then I suggest the Buyer and Seller work out a “win/win” scenario.  Usually the purchase price is lowered to a fair value, and then the windshield heat is eliminated from consideration as an “airworthiness item” on the prebuy.

If a Buyer or Seller walks into a transaction without knowledge of the windshield heat, the chances are VERY high that person is going to be be VERY disappointed at sale.

One thing is for sure…PPG (manufacturer of the heated windshield) is smiling widely.  There’s going to be LOTS of windshields replaced in the near-term as maintenance facilities will undoubtedly find LOTS of windshields that will have resistance measurements outside the parameters illustrated in Service Letter 1204.  My hope is that PPG will spend some serious energy determining why the PA46 Glass Windshields have such a poor record of performance and produce a windshield that doesn’t fail so frequently.  I fly LOTS of other pressurized, turbo-charged, high-altitude airplanes and those rarely have the repetitive problems that are found on the PA46 heated windshield.

For the time being, knowledge is key…as in any transaction, “he with the most knowledge usually wins”.  It’s a $30k question…be sure to position yourself well in the marketplace.  There’s going to be a LOT of $30k checks written by PA46 owners in the near future…be sure you’re not one of them.

About Joe Casey

ATP, CFI, CFII, MEI, CFI-G Commercial Pilot - SE, ME, Rotorcraft, Glider US Army AH-64 Pilot and UH-60 Instructor Pilot and Instrument Flight Examiner
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