AD 50-48-02
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Collins Radio | Receivers | Airworthiness Directives; COLLINS RADIO: Applies to All Model 51R-1 and 51R-2 Receivers Incorporating Allite or Thordarson 90/150 Cycle Filters in Their Tone Localizer Indicator Circuits and to All Model 51R-1 Receivers Which Have Not Been Modified in Accordance With Collins 51R-1 Service Bulletin Number 7a |
Unsafe Condition
Failure of the 90/150 cycle tone localizer system due to in-service failure of Allite or Thordarson filters, and loss of automatic gain control action leading to course reversal.
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Required Actions
Replace Allite and Thordarson 90- and 150-cycle filters with Collins Radio Co. approved filters per specified part numbers. Modify Model 51R-1 receivers per Service Bulletin No. 7a.
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Compliance Time
July 1, 1951
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Affected Aircraft
Collins Radio Model 51R-1 and 51R-2 receivers with Allite or Thordarson 90/150 cycle filters in tone localizer circuits, and Model 51R-1 receivers not modified per Service Bulletin 7a, installed in air carrier aircraft.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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