AD 99-16-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Learjet Inc. | 23 | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24 | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24A | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24B | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24B-A | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24C | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24D | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24D-A | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24E | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
| aircraft | Learjet Inc. | 24F | Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes |
Unsafe Condition
Malfunction of the horizontal stabilizer anti-ice system due to undetected accretion of ice on the leading edge of the horizontal stabilizer, which could result in loss of pitch control and reduced controllability.
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Required Actions
Perform a one-time detailed visual inspection of the electrical wire leads of the horizontal stabilizer anti-ice system to verify wire lead numbers match connected airframe wiring. Install wire ID straps on left- and right-hand sides of each terminal block and install warning placards. If discrepancies are found, repair them per Learjet's procedures before further flight.
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Compliance Time
Within 100 flight hours after the effective date (September 7, 1999).
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Affected Aircraft
Learjet Models 23, 24, 25, 28, 29, 31, 55, and 60 series airplanes as listed in specific service bulletins dated October 27, 1998.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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