56 Windows

TTP	B1-L3	ATA 56
Beech 90 Series	B2-L1	Windows

The King Air forward windshields are formed from two-ply glass in an integral aluminum frame. The two glass plies are bonded together with a center polyvinyl sheet that contains the fine wire heating grids. The windshields are electrostatically  coated and current-production windshields are surface sealed. All the side windows are constructed from acrylic plastic.

WINDSHIELDS

 

The electrically heated laminated glass windshield is subject to the gradual process of delamination due to the effect of chemical action and differentials of temperature and pressure incurred during pressurized flights at varying altitudes and under varying weather conditions. This delamination is not detrimental to the structural integrity of the windshield, but it may significantly decrease visibility or the deicing capability of the windshield. The following guidelines can determine when a windshield should be replaced:

 

1. Visibility Impairment—Replace the wind- shield when areas of delamination are enlarged to the point of impairing vision, whether or not these areas extend to the edge of the glass. Small delaminations appearing as bubbles are no cause for concern. The rate of growth of delamination  areas should be used as a criterion for scheduling replacement of the windshield.

 

2. Heating Impairment Limits—Replace the windshield when the lost heating area exceeds

1/4 to 1/3 of the total heated area.

 

The windshields should be routinely inspected for outboard moisture seal erosion or seal debonding. Erosion can be apparent with a visual inspection. The hump seals should be inspected to determine if they are well-bonded to the glass and aluminum retainer surfaces. If the seals can be lifted with finger pressure, they should be removed and replaced. If the seals are not well bonded between the outboard glass and metal retainer, moisture can enter the glass-to-inter- layer bond line and cause premature delamination of the windshield, which could significantly reduce its normal service life.

Cracked or Shattered Windshield

 

The following limitations apply when continued flight is required with a cracked outer or inner ply of the windshield:

 

•  Continued flight with a cracked windshield is limited to 25 flight hours.

 

•  Windshields  with  a  shattered  inner  ply have numerous cracks which obstruct forward vision. Small particles or flakes of glass can break free of the windshield and interfere with the crews vision. These windshields must be replaced prior to the next flight unless a special flight permit is obtained from the local FAA Flight Standards District Office.

•  Crack(s) must not impair visibility.

 

•  Crack(s) must not interfere with the use of windshield wipers for flights requiring the use of the wipers.

 

•  Windshield  anti-ice  must  be  operational for flights in icing conditions.

 

•  The following placard must be installed in plain view of the pilot:

 

MAXIMUM AIRCRAFT ALTITUDE IS LIMITED TO 25,000 FEET. CABIN DIFFERENTIAL PRESSURE MUST BE  MAINTAINED  BETWEEN  2.0 AND 4.6 PSI DURING FLIGHT.

 

Windshields with cracks in both the inner and outer plies must be replaced prior to the next flight unless a special flight permit is obtained from the local FAA Flight Standards District Office.

The outer glass surface is coated with a stannous oxide, nonelectrostatic application (NESA) designed  to  dissipate  static  electrical  buildup. The coating is grounded to the airframe structure and is checked periodically for continuity. Care should be taken to prevent damaging this outer coating and the windshield should be cleaned only with water, soap and water, a 50% isopropyl and water solution, or other approved cleaning agents. Never use any abrasive materials or strong acids to clean the glass. Do not apply wax. It is essential  windshield wipers be kept clean. Grit trapped by the wipers is a common source of scratches in the glass. Do not attempt to polish such nicks and scratches out of the glass surface

COCKPIT/CABIN WINDOWS

 

On current production aircraft, the side windows, including the storm window and the D window are formed from multiple-layered stretched  acrylic;  the  cabin  windows and the baggage compartment, or teardrop window, are formed from single-ply stretched acrylic. The plastic windows should be kept clean and waxed at all times. Only approved plexiglass cleaners  such as Mirror Glaze,  Permatex Plastic Cleaner or Parko Antistatic Plastic Polish should be utilized.

 

After gently washing and cleaning the windows, they should be waxed with a good grade of commercial wax. The wax fills in minor scratches and helps prevent additional scratches. Apply a thin, even coat of wax and bring it to a high polish by rubbing lightly with a clean, dry, soft flannel cloth. Never use a power buffer. The heat generated by the buffing pad may soften the plastic.

Acrylic windows are extremely susceptible to damage during painting, stripping and fuselage cleaning operations. Improper protection of the acrylic windows can cause severe chemical dam- age resulting in reduced service life and structural failure of the acrylic. Functional fluids such as deicing, hydraulic, etc., are also detrimental to the acrylic windows. Depending on the type of chemical involved, the damage caused to the window may not be evident for months; therefore, it must be stressed that all recommended cleaning procedures be followed and only the approved window cleaning products be utilized.

 

Two dust panes are inboard of the cabin window; each composed of a polarized film. The inboard pane may be rotated to permit light regulation. When the aircraft is parked in areas exposed to intensive sunlight, the polarized windows should be rotated to the clear position to prevent deterioration of the polarized material. Sufficient ultraviolet protection is provided to prevent fading of the upholstery.

Paint, paint strippers, degreasing compounds and most solvents can seriously damage acrylic win- dows. If any of these functions are performed in the vicinity of the windows, the windows must be completely sealed against the chemical compounds and fumes. Pressure-sensitive polyester film (mylar) and pressure-sensitive painting/ stripping masks of polyester, aluminum and other composite materials are commercially available for this purpose. When installed, the mask must extend beyond the window cutouts in the skin. This prevents the chemical compounds from attacking the window edge.

 

 Crack in Any Side Window (Cockpit or Cabin)

 

The following limitations apply when continued flight is required with a crack in any side window. These limitations do not apply to minor compression-type chips (Clamshell) which may occur on the milled edge of cockpit side windows. Refer to the AMM for the disposition of such chips.

 

•  Continued  flight  is  limited  to  24  flight hours.

 

•  Flights must be conducted with the cabin depressurized. The following placard must be installed in clear view of the pilot:

 

PRESSURIZED FLIGHT IS PRO- HIBITED DUE TO A CRACKED SIDE WINDOW. CONDUCT FLIGHT WITH THE CABIN PRESSURE SWITCH IN THE DUMP POSITION

PTP  Beech 90 Series	B1	LOC					TS
	B2