AD 81-25-03

81-25-03 McDONNELL DOUGLAS: Amendment 39-4271. Applies to McDonnell Douglas Model DC-9-10, -20, -30, -40, -50, and -80 series airplanes, including C-9A, C-9B, and VC-9C airplanes, certificated in all categories. Compliance required within six months from the effective date of this AD, unless already accomplished. To assure that proper windshield heat generation is available for bird impact protection and anti-ice functions on aircraft fuselage numbers 894 through 1021 and on aircraft that have had left, center, or right windshield panels replaced since November 1, 1978, accomplish the following:

A. Inspect windshield panels to determine manufacturer and year of manufacture. Windshield panels may be identified by the manufacturer's logo "PPG" or "LOF" in large capital letters with part number, specification, and serial number adjacent to logo. These are located at the top of the panel on the left and right-hand windshield panels, and at the bottom or top of the center windshield panel.

1. Panels manufactured by Libbey Owens Ford (LOF), no further action is required.

2. Panels manufactured by PPG Industries:

a. Determine the year of manufacture, which is contained in the serial number. Serial number samples are shown below:

8-H-10-20-220-315 (first digit indicates year of manufacture, 1978; third digit indicates month, October)

9-H-5-21-315-373 (first digit indicates year of manufacture, 1979; third digit indicates month, May)

0-H-4-6-219-215 (first digit indicates year of manufacture, 1980; third digit indicates month, April)

1-H-3-6-317-212 (first digit indicates year of manufacture, 1981; third digit indicates month, March)

b. Windshield panels with an October 1978 or prior manufacturing date coded, or January 1981 or subsequent manufacturing date coded, no further action is required.

c. Aircraft with less than 200 flight hours since new or on aircraft with less than 200 flight hours onreplacement panel(s), accomplish the following heating element resistance check on PPG November 1, 1978, through December 31, 1980, date coded windshield panels:

(1) Open anti-ice circuit breaker on lower electrical panel center for windshield to be checked.

(2) Disconnect electrical connector from windshield panel to be checked.

(3) Using an ohmmeter, check resistance between Pins L and P at receptacle on left (right) windshield panel. Resistance reading should measure 61.2-82.8 ohms.

(4) Using an ohmmeter, check resistance between Pins E and G at receptacle on center windshield panel. Resistance should measure 67.5-92.5 ohms.

(5) If windshield resistance is:

(a) Within tolerance on all three panels, aircraft may be continued in service, and panels must be repetitively inspected at 50-hour intervals until the accumulation of 200 flight hours.

(b) Within tolerance after the accumulation of 200 flight hours, no further actionis required.

(6) If resistance is out of tolerance on one or more of the three windshield panels:

(a) Center panel out of tolerance, install the following placard in full view of the pilot: "Do Not Exceed 260 kts IAS Below 10,000 Feet Altitude."

(b) Only side panel(s) out of tolerance, install the following placard in full view of the pilot: "Do Not Exceed 285 kts IAS Below 10,000 Feet Altitude."

(c) If windshield resistance of any panel, left, right, or center is greater than 130 ohms, install the following placard in full view of the pilot: "Flight into known icing conditions is prohibited." If left (right) windshield panel(s) resistance is 82.9 to 130 ohms, and/or center windshield panel resistance is 92.6 to 130 ohms, the panel(s) must be repetitively inspected at 50-hour intervals until the accumulation of 200 flight hours to ascertain that resistance remains at or below 130 ohms. After the accumulation of 200 flight hours, the repetitive inspection interval can be extended to 1,500 flight hours.

(d) The above restrictions can be removed when the out-of-tolerance panel(s) is/are replaced with panel(s) manufactured by LOF or any PPG manufactured panel(s) with a date code other than November 1, 1978, through December 31, 1980.

(7) Reconnect electrical connector to windshield panel and close circuit breakers.

d. For November 1, 1978, through December 31, 1980, date coded windshield panels which have over 200 flight hours, accomplish the following:

(1) Perform heating element resistance check, as outlined in paragraphs c(1) through c(4). If windshield resistance is within tolerance on panel(s), reconnect electrical connector to panel(s). No further action is required.

(2) If resistance is out of tolerance on any of the three panels, accomplish the instructions as outlined under paragraph c(6).

B. Alternate inspections, repairs, or other action to be accomplished on or after the effective date of this AD, which provide an equivalent level of safety, may be used when approved by the Chief, Los Angeles Area Aircraft Certification Office, FAA Northwest Mountain Region.

Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by this AD.

This amendment becomes effective January 4, 1982.