Introduction
On 24 March 2025, an Alliance Air Avions de Transport Régional ATR-42-600, registration VT-UDB, operating domestic flight 9I-821 from Indira Gandhi International Airport (Delhi/VIDP) to Shimla Airport (VISM), encountered a brake system malfunction while on approach to Shimla. Despite the anomaly, the flight crew conducted a safe landing on runway 32, and the aircraft taxied under its own power to the apron without further incident. No injuries or operational disruptions were reported.
As of 25 March 2025, the aircraft remains grounded in Shimla for maintenance inspection and corrective action, approximately 17 hours post-landing.
Flight & Aircraft Information
• Operator: Alliance Air (A subsidiary of Air India)
• Aircraft Type: Avions de Transport Régional ATR-42-600
• Registration: VT-UDB
• Engines: 2 × Pratt & Whitney Canada PW127M
• Flight Number: 9I-821
• Callsign: ALLIED 821
• Route: Delhi (VIDP) → Shimla (VISM)
• Date: 24 March 2025
• Occupants: 44 (Passengers and Crew Combined)
• Weather: VMC reported at destination
• Landing Runway: RWY 32
• Time on Ground Post-Landing: >17 hours
Sequence of Events
1. Departure and Enroute Phase
• The ATR-42-600 departed Delhi on schedule and proceeded towards Shimla under normal flight conditions.
• The enroute phase was uneventful, and the aircraft remained under positive radar control throughout the flight.
2. Approach to Shimla
• During the approach into Shimla Airport, which is known for its elevated terrain and short runway profile, the flight crew reported a technical issue with the braking system.
• The specific nature of the issue—whether it was hydraulic, anti-skid related, or mechanical—was not disclosed at the time of reporting.
3. Landing and Taxi
• Despite the braking concerns, the crew opted to continue the approach to RWY 32 and executed a safe landing.
• The aircraft maintained directional control during rollout and was able to vacate the runway and taxi to the apron under its own power.
• No emergency response was triggered upon landing, indicating confidence in system redundancy and crew control.
Technical Analysis: Brake Systems in the ATR-42-600
The ATR-42-600 is equipped with a dual-redundant hydraulic brake system, supported by:
• Hydraulic pumps powered by both engines
• Brake accumulator pressure reservoir for redundancy
• Anti-skid units and brake control valves
• Manual brake system backup
Potential causes of a brake-related issue include:
• Hydraulic fluid leaks
• Brake wear or failure of brake pads
• Anti-skid system sensor fault
• Brake temperature overheat condition
• Malfunctioning brake control valves
Any fault in these areas may trigger ECAM warnings or cockpit advisories, prompting a brake failure checklist and modified landing procedures, especially at high-elevation, short-runway airports like Shimla.
Operational Considerations at Shimla Airport
Shimla is a category-C airfield with the following challenges:
• Short runway (1,230 metres / ~4,035 ft)
• Runway slope gradient
• Surrounding mountainous terrain
• Limited overrun area
Landing with degraded braking capability in such conditions is inherently riskier, requiring:
• Adjusted approach speeds
• Early touchdown aiming points
• Reinforced coordination with ATC and ground services
Aftermath and Maintenance Actions
• The aircraft was safely parked and secured on the apron at Shimla.
• A maintenance team was dispatched to conduct a technical inspection and assess the reported brake problem.
• No passengers or crew were injured, and no runway excursion or overrun occurred.
• As of the latest report, VT-UDB remains grounded for further evaluation and potential rectification.
Conclusion
Alliance Air flight 9I-821, operating an ATR-42-600, reported a brake system problem during final approach into Shimla on 24 March 2025. The crew successfully executed a precautionary landing on runway 32 without incident. The aircraft was taxied to the stand, and a technical investigation is underway.
The professionalism of the crew, combined with appropriate system redundancies, ensured a safe outcome, even at an airport with challenging topography and limited runway length. The aircraft remains out of service pending further maintenance action.
Disclaimer
This report is based on publicly available information as of 25 March 2025. While every effort has been made to ensure accuracy, the findings may be subject to revision as investigations progress. If you are the rightful owner of any referenced materials and wish them removed, please contact takedown@cockpitking.com.
