Adiru Vs Adc

Let’s clearly explain the difference and relationship between the ADC and ADIRU, step by step 👇

🧭 1️⃣ The Simple Summary

✅ In short:

An ADIRU = ADC + IRS (Inertial Reference System) combined into one unit.

⚙️ 2️⃣ What Each One Measures

🧮 3️⃣ What Each One Outputs

✈️ 4️⃣ The Key Relationship

The ADIRU includes an air data function similar to an ADC — but it also adds an inertial reference (gyros + accelerometers) that lets it:

• Know aircraft attitude (pitch, roll, yaw)
• Track movement through space (position, velocity, acceleration)
• Provide data even if pitot/static systems fail

So in modern aircraft (like Airbus A320, A350, Boeing 777, 787):

The ADC function is built into the ADIRU — you don’t have separate ADC boxes anymore.

In older aircraft (B737 Classic, early A300s):

You had separate ADC units and IRUs (Inertial Reference Units).

🧩 5️⃣ Typical Modern Setup (Airbus-style)

           PITOT / STATIC / TEMP / AoA
                   │
        ┌──────────┴──────────┐
        │     ADIRU 1        │
        │     ADIRU 2        │
        │     ADIRU 3        │
        └──────────┬──────────┘
                   │
   FMS • PFD/ND • Autopilot • Stall Warning

Each ADIRU has two logical parts:

• ADR (Air Data Reference) → airspeed, altitude, Mach
• IR (Inertial Reference) → attitude, heading, position

Hence the name: AD + IR = ADIRU

🧠 6️⃣ Think of It Like This:

✅ 7️⃣ Quick Summary

🧭 Air Data Computer (ADC) — Simple Explanation

The Air Data Computer (ADC) is like the “brain” that collects and processes all the air pressure and temperature data from the aircraft’s sensors.

It takes information from:

• Pitot tubes → total (dynamic) pressure
• Static ports → static air pressure
• Temperature probe → outside air temperature
• Angle of Attack (AoA) sensor → airflow angle over the wing

The ADC then calculates important air data values such as:

• Airspeed (IAS, CAS, TAS, Mach)
• Altitude (pressure altitude)
• Vertical speed
• Static air temperature (SAT)

These results are sent digitally to:

• Flight instruments (PFD, ND)
• Flight Management System (FMS)
• Autopilot and autothrust systems
• Inertial systems (INS/IRS)

This digital information allows all other systems to “speak the same language.”

⚙️ ADIRU — Combined Modern Version

In modern airliners, the ADC and the Inertial Reference Unit (IRU) are combined into one unit called an:

🧩 ADIRU — Air Data Inertial Reference Unit

This box provides both:

• Air data (speed, altitude, Mach, etc.)
• Inertial data (attitude, heading, acceleration, position)

Because the two data types work closely together — airspeed and acceleration, for example — it’s more efficient and accurate to have them in the same computer.

✈️ ADIRS — The Complete System

Airliners don’t rely on just one ADIRU. They usually have two or three ADIRUs for redundancy and safety, and together they form the:

ADIRS — Air Data Inertial Reference System

This ensures:

• Backup if one unit fails
• Cross-checking for accuracy
• Continuous air and inertial data available to all flight systems

🧠 In Simple Terms

The ADC calculates air data (how fast, how high). The IRU measures movement and attitude (which way and how you’re moving). Modern aircraft combine both into an ADIRU, and several ADIRUs together form the ADIRS — a smart, reliable system that keeps the aircraft accurately aware of its speed, altitude, attitude, and position.

✅ In short:

ADC = Air Data only IRU = Inertial data only ADIRU = Both combined ADIRS = The complete network of ADIRUs for redundancy