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Airbus H145 (BK117 D-2) · Components

Components by ATA chapter

Every ATA chapter has its own components page. Pick a chapter, then a part: what it is made of, how it works, what it connects to, the numbers that matter, how it fails and how mechanics inspect it.

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ATA 21 · Air Conditioning & Heating

Every part in this chapter is described below.

All parts in ATA 21

1.Bleed air valve

Taps regulated bleed air from each engine for the heating mix manifold.

A pneumatic valve on each Arriel 2E that taps regulated compressor bleed air for the H145's heating/demist mix manifold. One valve per engine, mounted on the engine casing near the compressor bleed port.

How it works

FADEC-scheduled or thermostatically modulated bleed flow is routed through stainless steel lines to a mixer valve; the valve throttles flow as a function of selected cabin temperature and bleed pressure available from the engine, closing automatically at low NG to protect engine performance during critical phases.

Bleed pressure	approx. 3-5 bar at cruise NG
Bleed temperature	approx. 150-200 C
Valve type	electro-pneumatic, spring-loaded closed

Failures

Valve sticks open: Cabin overheat, possible engine performance loss, crew selects heat OFF
Valve fails closed: No cabin heat available, demist function lost

Inspection

Inspect for bleed air leaks/soot staining at fittings
Functional check of valve response during ground run
Check wiring/connector condition if electrically actuated

2.Mixer/distribution valve

Blends hot bleed air with fresh air to the selected temperature.

A single mixing valve downstream of the two engine bleed taps that blends hot bleed air with ambient fresh air before it enters the cockpit/cabin duct network of the H145.

How it works

A rotary or butterfly element proportions hot and cold air streams based on the temperature selector position; a temperature sensor in the mix duct feeds back to the control logic (manual or automatic) to hold the selected outlet temperature, with crew able to override to full cold or full hot.

Mix outlet temp range	approx. ambient to 60-70 C
Control	manual rheostat or automatic thermostat

Failures

Valve jams mid-position: Uneven or uncontrollable cabin temperature
Sensor failure: Mix defaults to a fail-safe position, usually full cold

Inspection

Verify full range of travel on ground test
Check linkage/cable rigging for binding
Inspect sensor wiring continuity

3.Cockpit and cabin ducts

Flexible ducting to floor and console outlets and windshield demist nozzles.

Flexible, lightweight ducting that carries conditioned air from the mixer valve to floor-level and console outlets and to windshield demist nozzles throughout the H145 cockpit and cabin.

How it works

Low-pressure air flows by a combination of engine bleed differential pressure and the electric blower, through corrugated hose runs clipped along the airframe structure to individual outlet fittings; duct routing avoids chafing against wiring and flight control runs per design.

Duct material	silicone/fiberglass flexible hose
Operating pressure	near-ambient, low differential

Failures

Duct chafe/leak: Reduced flow to downstream outlets, localized hot spot
Duct detachment: Loss of demist or cabin heat at affected outlet

Inspection

Inspect duct clamps and routing for chafe against structure/wiring
Check for crushed or kinked sections on removal of panels
Verify outlet airflow during ground test

4.Eyeball fresh-air vents

Adjustable outlets for crew and passengers/patients.

Individually adjustable swivel outlets at each crew and passenger/patient position in the H145 cabin, allowing local control of fresh air direction and flow.

How it works

Each vent is a ball-and-socket diffuser fed from the main distribution duct; a rotating collar or lever opens/closes an internal shutter to vary flow independent of the central temperature selection, giving occupants individual comfort control.

Flow control	manual rotary shutter, 0-100%
Supply source	blower-boosted fresh air duct

Failures

Vent shutter seized: Fixed airflow, cannot be closed or opened by occupant
Vent detached from mount: Air loss to intended duct run, draft elsewhere

Inspection

Check for free rotation and shutter operation
Inspect mounting ring for cracking
Confirm airflow present at each vent during system test

5.Electric blower fan

Circulates cabin air on the ground or at low rotor downwash.

A DC electric fan unit in the H145 air distribution system that boosts cabin airflow on the ground or when rotor downwash and ram air are insufficient, such as during hover or ground idle.

How it works

Powered from the DC bus, the fan draws fresh air through an inlet scoop/filter and pushes it into the mix/distribution ducting; it runs continuously at low power settings or is thermostatically/manually switched, independent of engine bleed air operation.

Supply voltage	28V DC
Typical current draw	a few amps

Failures

Fan motor failure: Reduced airflow especially on ground/hover, crew relies on ram air in flight
Bearing wear/noise: Audible vibration, eventual seizure

Inspection

Listen for abnormal bearing noise during ops check
Inspect inlet screen for debris/blockage
Check circuit breaker and wiring for condition

6.Cabin heater (combustion type, optional)

Independent fuel-burning heater for HEMS cabins, with overheat protection.

An independent, fuel-burning combustion heater fitted to HEMS-configured H145s to provide cabin heat without relying on engine bleed air, typically mounted in a baggage/equipment bay.

How it works

The unit draws fuel from the aircraft fuel system, burns it in a sealed combustion chamber with its own air supply and exhaust, and transfers heat to cabin air via a heat exchanger; overheat and flame-out sensors shut the unit down automatically, with a cockpit switch for crew control and a smoke/fire warning tie-in.

Fuel source	aircraft Jet A/Jet A-1 supply
Overheat protection	automatic shutdown thermostat/sensor

Failures

Overheat trip: Heater shuts down, cabin heat lost, possible smoke/fire caution
Ignition failure: No heat output, fault light/CAS message

Inspection

Inspect combustion chamber and exhaust for soot/cracking
Test overheat sensor function per maintenance schedule
Check fuel line fittings for leaks

7.Air conditioning unit (optional)

Electrically powered vapour-cycle cooling for cabin/patient comfort on VIP/HEMS kits.

An electrically powered vapour-cycle cooling system fitted to VIP and HEMS H145 cabins for patient/passenger thermal comfort, with the compressor and condenser typically mounted externally or in a dedicated bay.

How it works

An electric compressor circulates refrigerant through condenser and evaporator coils in a standard vapour-cycle loop; cabin air is blown across the evaporator coil and ducted to cabin outlets, with the compressor cycling on thermostat demand and drawing significant DC or inverter-supplied AC power.

Power source	28V DC or inverter-derived AC
Refrigerant	HFC-type, e.g. R134a

Failures

Compressor failure: Loss of cooling, CAS caution, heater/vent fallback
Refrigerant leak: Reduced cooling capacity, low-pressure switch may inhibit compressor

Inspection

Check refrigerant charge/pressure per schedule
Inspect condenser coil for debris obstruction
Verify compressor clutch/cycling operation on ground test

EDUCATIONAL USE ONLY. Content is summarised from manufacturer documentation for learning. It is not approved flight or maintenance data. Always use the current, aircraft-specific POH/AFM, FCOM, QRH, AMM and operator procedures.