69-23-03 PIPER: Amendment 39-871. Applies to Piper PA-18-150 type airplanes, S/N 18-8809 through 18-8851, except S/N 18-8844 and 18-8849, certificated in all categories.
To determine if the lower longerons are made from 1025 steel or the approved 4130 steel, accomplish before further flight the following inspection:
(a) Remove the rear seat, look downward through the no sag springs and locate the lower fuselage longerons on the left and right sides of the aircraft.
(b) From a point adjacent to the aileron cable pulley measure aft 10 inches on the top of the longeron and perform the following:
(1) Using longitudinal strokes sand the top surface of the right and left lower longerons with No. 80 emery cloth, for an area approximately 3 inches in length and 1/2 inch wide. NOTE: No chemical reaction will occur unless this area is thoroughly cleaned down to the bare metal. Use only longitudinal strokes to remove the paint, primer, metalizing or corrosion from this area.
(2) Wipe specified area with a clean cloth.
(3) Apply one drop of concentrated nitric acid on the sanded area.
(4) If the longeron is 1025 steel, the acid drop will boil and turn a yellowish orange or brown.
(5) Wipe off the acid spot and neutralize the area with baking soda paste.
(6) Wipe surface and wash with water.
(7) Prime and paint the test area.
(8) If the test indicates (as described above) the longeron is 1025 steel, the aircraft is considered unairworthy and must be grounded until the aircraft is altered in accordance with an alteration approved by the Chief, Engineering and Manufacturing Branch, Eastern Region.
(9) The aircraft is considered airworthy, relative to the longeron being 4130 if there is no reaction to the aforementioned acid test, and can be returned to service.
Piper Service Bulletin No. 302, dated October 23, 1969 covers this subject.
This amendment is effective November 15, 1969 and was effective upon receipt for all recipients of the telegram dated October 24, 1969 which contained this amendment.