AD 99-19-20
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Short Brothers PLC | SD3-30 | Airworthiness Directives; Short Brothers SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes |
| aircraft | Short Brothers PLC | SD3-60 | Airworthiness Directives; Short Brothers SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes |
| aircraft | Short Brothers PLC | SD3-60 SHERPA | Airworthiness Directives; Short Brothers SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes |
| aircraft | Short Brothers PLC | SD3-SHERPA | Airworthiness Directives; Short Brothers SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes |
Unsafe Condition
Failure to activate the airframe pneumatic deicing boots at the first signs of ice accumulation in icing conditions can lead to reduced controllability due to adverse aerodynamic effects of ice adhering to the airplane prior to the first deicing cycle.
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Required Actions
Revise the Airplane Flight Manual (AFM) Limitations Section to include requirements for activating the wing and tail pneumatic deicing boots at the first sign of ice formation or ice detector annunciation, and specify continued automatic or manual cycling until icing conditions are exited and a full deicing cycle is completed.
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Compliance Time
Within 10 days after the effective date of this AD (December 27, 1999)
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Affected Aircraft
Short Brothers PLC SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA series airplanes equipped with pneumatic deicing boots, certificated in any category.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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