Details

Introduction
High-Energy Net-Based Emergency Runway Arresting System for Fighter Aircraft On a modern fighter base, everything is designed around speed: high approach velocities, short decision windows, heavy weapon loads, and tight sortie cycles. The same parameters that make a fighter effective in combat also make it unforgiving during an abnormal landing or aborted take-off.

Now picture a real failure case:
• A fighter touches down long and fast on a wet runway.
• Anti-skid and brakes are working, but there simply isn’t enough friction or distance left.
• The end-of-runway lights are coming up fast; beyond that there is soft ground, perimeter fencing, roads, maybe even populated areas.
At that point, the base either has a dedicated, engineered emergency arresting system—or it is gambling a multi-million-dollar aircraft, a pilot’s life, and runway availability on luck.

The Aircraft Arresting Gear (AAG) System is that engineered safeguard. Installed at each end of the runway, it uses a high-strength Nylon-66 net, textile purchase tapes, and a dual 20T + 40T water-twister energy absorber to safely stop aircraft in the 6–40 tonne class within a controlled run-out up to ~270 m, holding peak deceleration to around 3 g so the aircraft and pilot can walk away from an otherwise catastrophic overrun.

It is not a comfort feature. It is designed for the worst single day in the life of the runway—the moment when brakes, runway length, weather, and pilot margins have all been exhausted.

1. Mission, Envelope & Typical Use Scenarios
The AAG is fitted as a permanent, always-ready safety barrier aligned with the runway over-run on both ends. It turns an uncontrolled overshoot into a predictable engineering event.

Operating envelope
• Aircraft mass range: ~6,000 kg to ~40,000 kg
• Maximum arresting run-out: up to 270 m (depending on entry speed and mass)
• Maximum deceleration: approx. 3 g, tuned via dual-stage absorber
• Net deployment time: about 3 seconds from stowed to fully raised
• System reset / retrieval: typically 10–15 minutes after an arrest

Real-world scenarios where the AAG is decisive:
• Rejected take-off at high gross weight with limited runway remaining
• Landing overruns on wet/contaminated or low-μ runway surfaces
• Brake, anti-skid or partial hydraulic failure on landing
• Crosswind or tailwind landings where touchdown point shifts unfavourably
• High-elevation or hot-day operations where stopping distances increase
• Short over-run length with obstacles, roads or public areas beyond the fence
In all of these, the AAG provides a repeatable, measurable, engineered stop, rather than a random excursion into whatever lies beyond the runway end.

2. High-Level Technical Specification (For Datasheets / Marketing)

  

    

      
Category
      
Parameter
      
Specification
    
  
  

    

      
Performance
      
Aircraft mass range
      
~6,000 kg to ~40,000 kg
    
    

      
Performance
      
Max aircraft deceleration
      
≈ 3 g (controlled, non-shock arrest)
    
    

      
Performance
      
Max arresting run-out
      
Up to 270 m
    
    

      
Performance
      
Arresting principle
      
Net capture + textile purchase tape + dual water-twister energy absorber
    

    

      
Net System (MENA)
      
Net width
      
≈ 58 m span
    
    

      
Net System (MENA)
      
Net height
      
≈ 4.7–4.9 m deployed
    
    

      
Net System (MENA)
      
Vertical elements
      
40 high-tenacity Nylon-66 elements
    
    

      
Net System (MENA)
      
Element strengths
      
Vertical > 3,400 kgf; Horizontal > 2,300 kgf
    

    

      
Stanchion System (STS)
      
Qty per runway end
      
2 (left & right)
    
    

      
Stanchion System (STS)
      
Mast height
      
≈ 7.5 m steel lattice frame
    
    

      
Stanchion System (STS)
      
Net raise time
      
≈ 3 s
    
    

      
Stanchion System (STS)
      
Drive
      
3-phase squirrel-cage geared motor (~19 HP) with brake
    

    

      
Energy Absorber (EAA)
      
Type
      
Dual stacked water-twister (20T + 40T)
    

    

      
Working fluid
      

      
Water + ethylene glycol (anti-freeze, viscosity control)
    
    

      
Stage switching
      

      
Linear actuator, slider fork, < 5 s response
    

    

      
Purchase Tape & TRS
      
Energy link
      
High-strength textile purchase tape
    
    

      
Purchase Tape & TRS
      
Tape retrieval
      
10–15 min full reset time
    

    

      
Control & Power
      
ECS
      
Electrical Control System with full interlocks & alarms
    
    

      
Control & Power
      
Control Hut
      
≈ 12 m × 8 m × 3.5 m (L × W × H)
    
    

      
Control & Power
      
Aux power
      
≈ 6 kW rooftop solar + DG provision
    

    

      
Civil
      
Foundations
      
Dedicated RCC foundations for each subsystem, designed for dynamic arrest loads
    
  


This is the layer you show on a website, in a brochure or at the front of a technical offer; the following sections unpack what actually sits behind these numbers.

3. Arresting Concept – From Overshoot to Controlled Stop
At its core, the AAG converts 1⁄2·m·v2 of kinetic energy into heat in a water-glycol absorber, using the net and purchase tapes as the mechanical link.

Concept in one narrative 
In an emergency, command is given and the two stanchion towers at the runway edges rapidly raise a wide textile net across the over-run. The aircraft enters and is enveloped by this net, which breaks calibrated shear pins and releases from its ground anchors. The net is connected to high-strength purchase tapes that run through sheaves and fairlead tubes to a dual water-twister energy absorber buried at the side of the runway. As the aircraft pulls the net and tapes forward, the absorber spins in a controlled water-glycol bath, converting kinetic energy into heat with a smoothly increasing torque. The aircraft is brought to a controlled stop within the design run-out, after which the tapes are rewound, the net is re-rigged, and the system goes back to standby.

Step-by-step sequence (operational view)
• Standby mode
  ▹ Net (MENA) is lowered, attached to net anchors.
  ▹ Purchase tapes are fully wound on the absorber drum.
  ▹ ECS monitoring all subsystem health (motors, sensors, positions).

• Emergency / deploy command
  ▹ Controller triggers deployment from the control hut.
  ▹ Stanchion Systems (left & right) raise the net to full arresting height in ≈3 s.

• Engagement
  ▹ Aircraft enters and wraps the net.
  ▹ Load in the net bottom rises until ESS shear pins (≈2,500 kgf) fail; bottom of the net releases from the anchors.
  ▹ Net now travels with the aircraft, load routed into purchase tapes through Tape Connectors.

• Energy transfer & absorption
  ▹ Purchase tapes pay out through Sheave Assemblies and fairleads, driving the drum on the dual 20T+40T water-twister absorber.
  ▹ ECS selects 20T, 40T, or combined mode via a linear actuator moving a slider fork (switching <5 s).
  ▹ Fluid shear in the water-glycol mix produces braking torque, keeping deceleration near the 3 g target.

• Stop and reset
  ▹ Aircraft stops within the design run-out and is recovered.
  ▹ Tape Retrieval System rewinds the tapes; the net is lowered, inspected, and re-secured to the anchors.
  ▹ Total turnaround for the AAG is typically 10–15 minutes, so the runway is quickly back in service.

4. System Architecture & Subsystems (Detailed)
Each runway end has a defined set of mechanical, electrical and civil subsystems that together deliver the arresting function.

4.1 Multi-Element Net Assembly (MENA) – The Arresting Interface
The MENA is the physical barrier the aircraft sees. It must be strong, compliant, and aerodynamically stable.

• Material & structure
  ▹ High-tenacity Nylon-66 webbing, chosen for high tensile capacity, controlled elongation and environmental resilience.
  ▹ Approx. 58 m wide and 4.7–4.9 m high in deployed state.
  ▹ Built from 40 vertical elements, interconnected by horizontal straps forming a mesh.

• Mechanical performance
  ▹ Vertical elements: breaking strength > 3,400 kgf.
  ▹ Horizontal elements: breaking strength > 2,300 kgf.
  ▹ Geometry allows the net to “wrap” around nose, forward fuselage and wing root, spreading load across multiple contact zones.

• Operational behaviour
  ▹ In standby, the net is folded down along the edges.
  ▹ On deployment, it rises to form a vertical curtain in the aircraft path.
  ▹ On engagement, the net travels forward with the aircraft, feeding load into the tapes.

4.2 Net Anchors (NA) & Engagement Support System (ESS) – Controlled Release Layer
These subsystems control how and when the net detaches from ground restraint and starts travelling with the aircraft.

Net Anchors (NA)
• Installed at 17 locations across the width of the arresting lane.
• Each anchor is a hollow steel tube with welded fins and a nut, set in the pavement.
• A D-ring connects these anchors to the net’s bottom horizontal straps.
• Function: hold the net down in wind and jet blast; release once shear pins in ESS fail.

Engagement Support System (ESS)
• Shear-off coupling & pin
  ▹ Round alloy-steel coupling with a 2,500 kgf shear pin.
  ▹ Defines the consistent load point at which the net bottom is released.

• Suspension & restraining cables
  ▹ 11 mm diameter suspension rope supports net height.
  ▹ 8 mm restraining ropes hold the net in defined lateral and longitudinal positions.

• Force monitoring & actuation
  ▹ A 44 kN stainless load cell measures net tension for diagnostics and performance validation.
  ▹ A 3-phase, 5.5 HP brake motor is used to adjust and position the net during maintenance and set-up.

Together, NA + ESS ensure that engagement and net release are repeatable and predictable, not random.

4.3 Stanchion Systems (STS) – Fast Deployment Towers
The stanchions are the tall steel towers that raise and support the net.
• Mechanical design
  ▹ Height approx. 7.5 m, hinged at the base.
  ▹ Fabricated from IS 2062 E250 structural steel with cross-bracing.
  ▹ Verified for dynamic loads and fatigue; main frame stresses around 32.5 MPa under design conditions.

• Drive & cables
  ▹ Squirrel-cage induction motor (~19 HP) with gearbox and electromagnetic brake.
  ▹ Winch and tension cables are 14 mm steel wire ropes (~0.82 kg/m), routed through pulleys and sheaves.

• Energy absorption & protection
  ▹ Telescopic hydro-pneumatic shock absorbers handle sudden loads on the mast.
  ▹ Cantilever leaf spring sets (7 leaves per set) and elastomer pads manage end-of-travel and impact scenarios.

These systems allow very rapid net deployment without overstressing the structure, even when subjected to violent dynamic loads.

4.4 Tape Connector (TC) & Purchase Tape (PT) – Load Transfer Bridge
The interface between flexible net and high-inertia absorber must be both strong and instrumented.
• Tape Connector (TC)
  ▹ “C”-shaped alloy-steel weldment with sleeve & spacer tube, designed for high tensile loads.
  ▹ Incorporates a balanced strain-gauge load cell and DAQ, enabling precise capture of tape loads during arrest.

• Purchase Tape (PT)
  ▹ High-strength textile tape with controlled elongation, abrasion resistance and fatigue life.
  ▹ Serves as the main energy transmission link from MENA to EAA; its behaviour directly shapes the deceleration curve.

This combination ensures smooth load transfer and full traceability of arresting forces.

4.5 Energy Absorber Assembly (EAA) – Dual Water-Twister Core
This is the energy-conversion heart of the AAG.
• Configuration
  ▹ Two water-twister units rated 20 T and 40 T torque, stacked vertically.
  ▹ Both are mounted on a common structural frame (≈6,000 kg).
  ▹ A shared vertical rotor shaft and tape drum connects to the purchase tape.

• Internal materials & hardware
  ▹ Rotors and stators: EN24T alloy steel, precision machined and heat-treated.
  ▹ Shafts & couplings: 17-4 PH stainless steel.
  ▹ Drum hardware: SS304 hub with Al6063-T6 flanges.
  ▹ Bearings: SKF spherical roller bearings; seals designed for high-speed, pressurised operation.

• Working fluid & control
  ▹ Fluid: water + ethylene glycol for stable viscosity and freeze protection.
  ▹ Stage selection: linear actuator moving a slider fork, providing <5 s switching between 20T and 40T stages, or a combined effective curve.

As the tape pays out and the drum spins, the rotor shears the fluid through the stator vanes, generating a predictable torque vs. speed characteristic. This is tuned so that the deceleration profile is smooth and shock-free, avoiding abrupt g-spikes.

4.6 Tape Retrieval System (TRS), Pressure Roller Assembly (PRA) & Sheave Assemblies (SA)
These subsystems ensure that the purchase tape is handled cleanly and the system can be restored quickly.

Tape Retrieval System (TRS)
• Horizontally mounted 3-phase induction motor, connected via flexible coupling to a worm-gearbox (ratio ~50:1).
• Power transmitted via a leather flat belt to the tape drum pulley (260 mm hub / 320mm flange).
• An arm-and-roller guide traverses along the drum face, ensuring even tape lay.
• Typical tape rewind and reset: 10–15 minutes.

Pressure Roller Assembly (PRA)
• 100×100×6 mm SHS steel arm with an aluminium pressure roller on deep-groove ball bearings.
• Pre-loaded using a 25 mm bungee system to keep constant tape pressure.
• Designed to meet MIL-B-83183B purchase-tape handling criteria.

Sheave Assemblies (SA)
• Convex-profile steel sheaves on 100 mm alloy-steel shafts with cylindrical roller bearings.
• Structural-steel housings with wear plates, gaskets and O-rings per IS 9975-1981.
• Provisions for proximity sensors to monitor sheave rpm (and hence tape speed) during engagement.

Together, these make sure the tape is never mis-handled, preventing knots, overlaps or edge damage that could compromise the next arrest.

4.7 Electrical Control System (ECS), Control Hut & Civil Foundations
The mechanical system is integrated into the base’s infrastructure via a dedicated control & civil layer.
• ECS functions
  ▹ Net deployment command & feedback
  ▹ EAA stage selection & status
  ▹ TRS actuation
  ▹ Health monitoring, alarms, and safety interlocks
  ▹ Event logging via load cells and sheave-rpm sensors

• Control Hut
  ▹ Approx. 12 m × 8 m × 3.5 m building near the AAG installation.
  ▹ Houses ECS, UPS, communications and optional DG set.
  ▹ Fitted with ~6 kW rooftop solar and associated power electronics for resilience.

• Civil works & foundations
  ▹ Individual RCC foundations for stanchions, absorbers, ESS, TRS, sheaves, net anchors and fairlead ducts.
  ▹ Designed for worst-case dynamic arrest loads, verified against overturning, sliding, uplift and fatigue.
  ▹ Trenches / ducts for fairlead tubes and routed cables ensure clean, protected layout.

5. Safety, Maintainability & Operational Advantages
Beyond the hardware, what matters is how the system behaves across years of operations.

Safety & performance advantages
• High-consequence risk mitigation
  ▹ Provides a dedicated, engineered stop for the worst failure cases, not just incremental improvement in normal operations.

• Predictable, traceable arrests
  ▹ Load cells in TC/ESS and rpm sensors on sheaves give quantifiable data for every arrest event.
  ▹ Allows validation of energy absorption and continuous improvement of procedures.

• Fast turnaround and high availability
  ▹ 10–15 minute reset time keeps the runway and squadron sortie rate intact after an arrest.

• Environmental robustness
  ▹ Materials, seals, coatings and civil design are suited for temperature extremes, humidity, dust, heavy rain and salt-fog conditions common to
airbases.

Maintainability
• Subsystems are modular (stanchions, absorbers, TRS, ESS, SA, PRA), enabling targeted maintenance without full system downtime.
• Use of standard industrial components (standardised bearings, gearboxes, motors) simplifies spares management.
• Scheduled inspections focus on:
  ▹ Net and purchase-tape condition (textile inspection and replacement cycles).
  ▹ Wire ropes, sheaves, bearings and seals.
  ▹ EAA fluid health (water-glycol condition) and leak-tightness.
  ▹ Civil foundations and anchor points.

6. Conclusion
The Aircraft Arresting Gear (AAG) System is not a generic GSE add-on—it is a mission-critical safety asset that stands between a high-speed overrun and a catastrophic loss of aircraft, runway, and life. By combining a high-strength textile net, intelligently controlled purchase tape handling, a dual-stage water-twister energy absorber, and a robust control and foundation architecture, the system converts an uncontrolled emergency into a managed, instrumented, repeatable engineering event. 

For the operator, the value is brutally simple:
• When everything goes right, the AAG is invisible.
• When everything goes wrong, the AAG is the only thing that still has to work—first time, every time. This system is engineered precisely for that moment.