عاكس الدفع (Thrust Reverser)

ما هو a Thrust Reverser?

A thrust reverser is a system integrated into an aircraft engine that redirects the engine's exhaust stream forward rather than rearward, creating a braking force to decelerate the aircraft after landing. While not the primary braking mechanism — wheel brakes and spoilers contribute more — thrust reversers are essential for safe landings on wet, icy, or short runways, and they significantly reduce brake and tire wear.

كيف يعمل

There are three main types of thrust reverser systems:

• Cascade (cold stream) reversers: Most common on high-bypass turbofans. Blocker doors divert bypass airflow through cascade vanes that redirect it forward and outward. Used on Boeing 737, 787, Airbus A320, A350 families.
• Pivot-door (clam-shell) reversers: Two semicircular doors close over the exhaust nozzle and redirect the hot core exhaust forward. Used on older aircraft and some business jets.
• Bucket-type reversers: Two "bucket" targets swing into the hot exhaust stream. Common on older turbojets and some regional jets (e.g., Embraer ERJ family).

Thrust reversers are only deployed on the ground with weight-on-wheels signals confirmed, preventing accidental in-flight deployment. They are powered by the engine's own bleed air or hydraulic systems and can be activated within 1–2 seconds of touchdown.

مواصفات الأداء

• Braking contribution: 20–40% of total deceleration on dry runways; up to 50% on contaminated runways
• Typical deployment speed range: From touchdown (~140–150 knots) to around 60–70 knots, then stowed to prevent re-ingestion of debris
• Maximum reverse thrust: Usually 40–50% of takeoff thrust in reverse direction
• Deployment time: Fully open within 1.5–3 seconds after crew selection
• Runway length savings: Can reduce landing roll by 15–30% on contaminated surfaces

أمثلة الطائرات

• Boeing 737 MAX: Cascade-type reversers on CFM LEAP-1B engines, standard equipment
• Airbus A320neo: Cascade reversers — many airlines use idle reverse only on dry runways to save engine life
• Boeing 777: Large cascade reversers on GE90 engines — particularly critical for heavy MTOW landings
• Airbus A380: Reversers on 2 inner engines only (engines 2 and 3); outer engines (1 and 4) have deactivated reversers
• Bombardier CRJ series: Bucket-type reversers on General Electric CF34 engines

Thrust reversers work in conjunction with the Thrust output from engines. On shorter runways, maximizing reverse thrust alongside autobrake settings is critical for safe stopping distance.