AD 99-04-15
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Porsche K.-G., Dr. Ing.h.c.F. | PFM3200N01 | Airworthiness Directives; Dr.Ing.h.c.F. Porsche Aktiengesellschaft (Porsche) 3200N01, N02, and N03 Reciprocating Engines |
| engine | Porsche K.-G., Dr. Ing.h.c.F. | PFM3200N02 | Airworthiness Directives; Dr.Ing.h.c.F. Porsche Aktiengesellschaft (Porsche) 3200N01, N02, and N03 Reciprocating Engines |
| engine | Porsche K.-G., Dr. Ing.h.c.F. | PFM3200N03 | Airworthiness Directives; Dr.Ing.h.c.F. Porsche Aktiengesellschaft (Porsche) 3200N01, N02, and N03 Reciprocating Engines |
Unsafe Condition
Fatigue cracking of valve springs due to relative motion between valve spring and valve spring retainer, leading to eventual spring failure and potential in-flight engine shutdown.
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Required Actions
Replace all valve springs in each engine cylinder head prior to further flight for engines with 500 or more hours time-in-service (TIS) since new or last overhaul. For engines with less than 500 hours TIS, replace valve springs prior to accumulating 500 hours TIS. Subsequent replacements must occur at intervals not exceeding 500 hours TIS, following Porsche SB No. N/105-036.
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Compliance Time
Prior to further flight for engines with 500 or more hours TIS since new or last overhaul as of the effective date. For engines with less than 500 hours TIS, prior to accumulating 500 hours TIS. Subsequent replacements must be done within 500 hours TIS.
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Affected Aircraft
Porsche PFM3200N01, N02, and N03 reciprocating engines installed on but not limited to Mooney M20L series airplanes.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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