A simulated instrument failure is an exercise that represents unavailable or unreliable instrument information. Used in training and practical tests, it helps learners recognize failures and maintain control using the remaining equipment.
The applicable test standards establish the skills the learner needs to demonstrate. Instructors should set clear lesson objectives, then select failures and simulation methods that develop those skills.
Skill Progression: Training should begin with maintaining control and transitioning to reliable indications, then progress to instrument approaches and missed approaches.
A useful exercise begins with a specific training objective, such as recognizing unreliable attitude information. The selected failure should simulate a problem that can realistically occur in the installed equipment.
Display Failure: One screen becomes unavailable, but its sensors may still work. A backup display or reversionary mode may restore access to the information.
Sensor Failure: A failed sensor may affect several displays and related functions. The exercise should reflect those effects; a second screen is not necessarily an independent backup.
Navigation Failure: Loss of a navigator can affect course guidance and connected equipment. Covering its screen does not remove those outputs or simulate every GPS failure.
The method should realistically simulate the selected instrument or display failure while remaining within equipment limitations.
Instrument Covers: Removable covers can obscure individual indications or an entire display while leaving unrelated information available.
Reversionary Mode: Where supported, a covered or dimmed display can be combined with manual selection of reversionary mode. The learner practices obtaining essential flight and engine information on the remaining visible display.
Declared Failures: The instructor identifies information as unavailable, and the learner avoids displaying or using it. For example, selecting another page can simulate loss of a moving-map presentation while leaving navigation guidance available.
Simulators and Training Devices: Suitable devices can reproduce misleading indications, failure warnings, and related system effects. Covering or dimming hides information but does not reproduce those effects or necessarily trigger automatic reversion.
Circuit Breakers: Breakers should not serve as routine training switches. Repeated operation can weaken them, and one breaker may supply several systems. Power interruption is appropriate only when aircraft-specific guidance and operator policy support it.
Example from Garmin's Retrofit Avionics Training Guide:
Do NOT attempt power loss simulations in IMC.
Power Cycling: Turning equipment off and back on may be prohibited inflight. Restoring power does not guarantee immediate recovery.
Example from an Aspen EFD1000 Flight Manual Supplement (IFR Operations):
Do not power-cycle the EFD1000 PFD in flight.
During a practical test, simulated instrument failures assess how the applicant maintains control and navigates using the remaining equipment. The failure must realistically represent the installed equipment without jeopardizing safety. If an action would jeopardize safety, the evaluator has the applicant simulate it.
The following summarizes expectations for partial-panel approaches during a full practical test. Additional-rating and reinstatement tests may have different task selections.
| Practical Test | Approach Expectations |
|---|---|
| Instrument Rating | A nonprecision approach following loss of primary flight instrument indications is required, using appropriate backup or partial-panel information. |
| Flight Instructor Instrument | A nonprecision approach using backup or partial-panel information is required. The applicant demonstrates and explains the approach and analyzes and corrects common errors. |
| Practical Test | Approach Expectations |
|---|---|
| Airline Transport Pilot | A nonprecision approach using backup or partial-panel information is required. A precision approach with a realistic instrument failure is recommended but does not replace it. |
Hand Flying: Each full practical test listed includes at least two different nonprecision approaches. At least one must be flown from an initial approach fix without autopilot or radar vectors. The evaluator may combine this with the partial-panel exercise or satisfy those requirements on different approaches.
Separate Exercises: When the requirements are met on different approaches, the evaluator may allow autopilot use, radar vectors, or both during the partial-panel exercise.
Flight Director and Yaw Damper: Both may be used on the hand-flown nonprecision approach when consistent with the simulated failure and equipment limitations.
Approach Completion: The evaluator may require a landing or a missed approach.