Threat and Error Management (TEM)

Origin

TEM was developed in the late 1990s by the University of Texas Human Factors Research Project (Helmreich, Klinect, Wilhelm) as part of the FAA's Line Operations Safety Audit (LOSA) and adopted by ICAO in 2002 as the common framework for CRM/HPL training (ICAO Doc 9803 Line Operations Safety Audit (LOSA), ICAO Doc 9683 Human Factors Training Manual).

Three building blocks

1. Threats

Events or conditions outside the crew's control that increase operational complexity.

GA examples:

Environment: turbulence, icing, thunderstorms, crosswind > demonstrated
Traffic: dense training operations, unwanted approaching traffic
Platform: unfamiliar aircraft, unusual avionics layout
ATC: language change, high frequency saturation
Personal: fatigue, pressure (see [[stress]])

2. Errors

Errors originate from within the crew: wrong input, forgotten step, misinterpretation.

Error types (Reason 1990):

Slips (execution errors with correct intent — wrong button)
Lapses (forgetting)
Mistakes (rule-based or knowledge-based — wrong decision)

3. Undesired Aircraft States (UAS)

Unwanted aircraft states arising from unmanaged errors: unintended altitude/heading/speed deviation, lateral or vertical path deviation, wrong configuration, lateral deviation on ground.

Mistake-mitigation strategy: Reduction / Detection / Recovery

The three-stage mitigation strategy for errors is central to TEM:

Stage	English	Action	Where it acts
1. Reduction	Reduction	Recognise threats pre-flight, avoid, or prepare	Before errors
2. Detection	Detection	Catch errors before they become UAS — cross-check, standard callouts, read-back	Between errors and UAS
3. Recovery	Recovery	Recognise UAS and return to safe state	After UAS

code

Threats ──► (1. Reduction) ──► no error
   │                              │
   ▼                              ▼
Errors ────► (2. Detection) ────► no UAS
   │                              │
   ▼                              ▼
UAS    ────► (3. Recovery) ─────► safe state

Practical examples:

Reduction: weather briefing shows crosswind 18 kt → decide pre-flight to use alternative airfield.
Detection: pilot forgets flap setting (slip) → co-pilot notes via configuration check and calls it → corrected before UAS.
Recovery: aircraft already in > 45° bank in cloud (UAS) → recovery via immediate wings-level on instruments → safe state restored.

"Point out errors of other pilots"

Important principle in crew environments and also in PPL training context:

When you recognise that another pilot (even a more experienced one) has made a mistake, you should immediately point it out — politely but directly.

Reasoning:

Authority gradient is a known accident factor: young co-pilots hesitate to correct experienced captains — sometimes fatally (e.g. Air France 447, Asiana 214).
TEM works only with active mutual monitoring (cross-check).
Experience does not protect from errors — even experienced pilots benefit from a heads-up.

How to point it out? Fact-based, not judgemental:

✓ "Hey, I think we're 200 ft below MEA — can we check that?"
✗ "You're flying too low!" (judgmental, escalates stress)

In a training setting (PPL): instructor pilot AND student pilot may point out errors to each other — important learning culture.

Application in PPL

Pre-flight: threat list in briefing (weather, aircraft, pilot, route).
In-flight: explicitly "Threat: crosswind 18 kt — plan: long final approach, go-around if crab > 15°".
After flight: debrief — what errors were there, how were they caught? (Learning).
Multiple people in cockpit: actively use cross-check — regardless of hierarchy.

[[shell-modell-icao]] structures where threats and errors arise.
Reason's Swiss Cheese explains chaining of multiple threats/errors into accident.
ICAO Doc 9859 SMM anchors TEM in organisational safety management.