69-13-03: Heater Exhaust Tube

69-13-03 PIPER: Amdt. 39-785 as amended by Amendment 39-1749. Applies to Piper PA-23, PA-23-160, PA-23-235, PA-23-250, PA-E23-250 and PA-30 airplanes equipped with Stewart-Warner "Southwind" model 940 series heater. To prevent carbon monoxide from entering the airplane cabin, accomplish the following: (a) Within 25 hours' time-in-service after the effective date of this airworthiness directive, unless already accomplished, remove the heater exhaust tube shroud and by means of a magnet determine if Stewart-Warner P/N 486238 exhaust extension (Piper P/N 754-708) is mild steel (magnetic) or stainless steel (non-magnetic). Mild steel extensions, regardless of condition, must be replaced with stainless steel extensions, when available. (b) If stainless steel extensions are not available, a mild steel extension may continue to be used but must be visually inspected for deterioration at intervals not to exceed 25 hours time-in-service. If inspection reveals deteriorationin the form of cracks, corrosion, rust or flaking, the exhaust tube must be replaced and if with a new or non-deteriorated mild steel P/N 486238 tube, it must continue to be inspected in accordance with this paragraph. (c) (1) For heaters having 900 or more hours' time in service, unless already accomplished within the last 400 hours' time in service after the effective date of this airworthiness directive, overhaul the heater assembly within the next 100 hours' time in service and every 500 hours thereafter in accordance with Stewart-Warner Service Manual PM-10035 dated July, 1966 or an equivalent procedure approved by the Chief, Engineering & Manufacturing Branch, FAA Eastern Region. An overhaul consists of a complete disassembly, cleaning, repair, reassembly and test as described in the above service manual. (2) Heaters having less than 900 hours' time in service on the effective date of this AD shall be overhauled in accordance with paragraph (1) prior to the accumulation of 1000 hours' time in service and every 500 hours thereafter. (3) In complying with (1) and (2) above, if the owner or operator cannot document heater operating time, aircraft time should be used. (d) If the overhaul described in paragraphs (c)(1) and (c)(2) above includes replacement of heat exchanger P/N G488636 with a new unit, the time to next overhaul may be extended to 1000 hours in lieu of 500 hours provided a new nameplate Stewart-Warner P/N 704897 or an equivalent approved by the Chief, Engineering & Manufacturing Branch, FAA, Eastern Region, is attached to the heater adjacent to the existing nameplate, and inscribed with unit Model No., Serial No., Aircraft Registration No. and hours of service time at installation. (Stewart-Warner Corp. South Wind Division Service Bulletin No. 73-2 covers this subject.) Amendment 39-785 was effective July 2, 1969. This amendment 39-1749 is effective December 14, 1973.