PEGASUS AIRLINES

AIRCRAFT MAINTENANCE & PAINT HANGARS

Process-Based Airflow Engineering for Aircraft Painting

A Gerhman × Lindab Engineering Solution

The Pegasus Airlines Aircraft Maintenance Center at İstanbul Sabiha Gökçen International Airport includes new Line Maintenance and Aircraft Paint Hangars developed to expand the airline’s in-house aircraft maintenance capabilities.

The facility provides simultaneous maintenance capacity for four narrow-body aircraft, while the dedicated paint hangar accommodates one narrow-body aircraft for surface preparation and complete painting operations.

Aircraft paint hangars require a ventilation approach significantly different from conventional comfort HVAC systems. The air distribution system must maintain the required air velocity and environmental conditions around a large and aerodynamically complex aircraft while supporting the controlled transport of paint overspray, solvent vapours and volatile organic compounds (VOCs) toward the extraction system.

For this reason, ventilation is considered an integral part of the aircraft painting process rather than simply a building HVAC function.

Gerhman, in cooperation with its strategic partner Lindab and in coordination with mechanical subcontractor Birleşim Mühendislik, developed the air distribution solution from the engineering design stage through product selection, system calculations, CFD analysis, airflow optimization and commissioning.

The air distribution system was implemented using Lindab RCW low-turbulence displacement diffusers, selected and configured according to the specific aerodynamic and operational requirements of the aircraft paint hangar.

Engineering Challenge

Aircraft refinishing consists of several different processes:

Paint Stripping → Cleaning → Surface Preparation → Priming → Final Painting

These operations do not necessarily require identical ventilation conditions. Required surface velocities, contaminant loads and active working zones vary throughout the painting process.

Aircraft geometry creates an additional engineering challenge. The fuselage, wings, engines, horizontal stabilizers and vertical tail act as large aerodynamic obstructions within the hangar.

Their interaction with the supply airflow can create:

Low-velocity regions · Aerodynamic shadow zones · Local recirculation · Non-uniform surface velocities

Simply increasing the total ventilation rate does not necessarily eliminate these conditions.

The engineering objective was therefore to establish the required airflow velocity and direction around the active aircraft surfaces, while minimizing unnecessary airflow to areas where no active process was taking place.

Engineering Design & Product Selection

Gerhman developed the system using its engineering calculation and product-selection software.

The design process evaluated the main aerodynamic and thermal parameters affecting air distribution:

Airflow Rate · Surface Air Velocity · Discharge Velocity · Pressure Drop · Throw Distance · Jet Penetration Depth · Discharge Direction · Supply-Air Temperature · Operating Zone

Different operating scenarios were evaluated according to the individual stages of the aircraft painting process.

This approach allowed the air distribution system to be designed according to the actual process requirements rather than sizing the complete hangar around a single maximum operating condition.

CFD-Based Airflow Analysis

Following the preliminary engineering calculations, Computational Fluid Dynamics (CFD) analysis was used to evaluate and optimize the proposed airflow concept before implementation.

The CFD studies analysed the interaction between:

Supply Airflow + Lindab RCW Diffusers + Aircraft Geometry + Process Zones + Extraction System

The simulations were used to evaluate:

air velocity distribution around the aircraft,
surface airflow uniformity,
airflow direction and jet penetration,
potential low-velocity and recirculation zones,
airflow behaviour around the fuselage, wings and tail,
interaction between supply and extraction,
alternative zonal operating scenarios.

CFD therefore served as an engineering design and verification tool, allowing alternative configurations to be analysed before the final system was implemented.

This was particularly important because conventional air-change calculations and catalogue-based diffuser selections alone cannot fully represent the complex three-dimensional airflow patterns created around an aircraft.

Air Distribution Product: Lindab RCW

The final air distribution solution was implemented using Lindab RCW low-turbulence displacement diffusers.

The RCW units were selected for their ability to provide the aerodynamic characteristics required by the aircraft painting process:

Low-Turbulence Displacement Airflow
Adjustable Air Discharge Direction
Electrically Controlled Jet Penetration Depth
Low Pressure Drop
Stable Operation Under Heating and Cooling Conditions

These characteristics allowed the air distribution pattern to be adapted according to the aircraft geometry, active process zone and required surface air velocity.

Low-Turbulence Air Distribution

Excessive turbulent mixing is undesirable in aircraft painting applications because it can redistribute overspray and airborne contaminants and generate local recirculation around aircraft surfaces.

Lindab RCW units introduce conditioned air using a low-turbulence displacement principle, creating a controlled airflow field through the active working zone.

The design supports a defined airflow path from the supply side, across the working area and toward the extraction system.

The engineering objective is therefore not only to provide the required total airflow, but also to establish the correct velocity distribution and airflow direction at the aircraft surface.

This supports the controlled transport of overspray, solvent vapours and VOCs toward the extraction system while limiting unnecessary dispersion within the hangar.

Adjustable Air Direction & Jet Penetration

Different parts of an aircraft require different airflow trajectories and penetration distances.

The airflow requirement around the fuselage, for example, is different from that around the wings, tail section or lower aircraft surfaces.

Lindab RCW units incorporate an electric actuator for adjustment of the discharge characteristics and jet penetration depth.

This allows the airflow pattern to be adapted according to the active working zone.

Where greater penetration is required, the discharge characteristics can be adjusted accordingly. Where the active process is closer to the supply zone, unnecessary penetration can be reduced.

This capability was an important element in developing the process-based zonal ventilation strategy.

Process-Based Zonal Control

The main system optimization was achieved by replacing the initial full-volume ventilation concept with process-based zoning.

Instead of treating the entire hangar as a single ventilation zone operating continuously at peak conditions, the aircraft and surrounding working areas were divided into functional process zones.

The system could therefore provide the required:

Airflow Rate + Surface Velocity + Airflow Direction + Jet Penetration

according to the active aircraft zone and painting process.

Conditioned air was directed to where it was actually required rather than maintaining the complete hangar continuously under the maximum design condition.

This engineering approach resulted in an approximately:

64% REDUCTION

IN REQUIRED AIRFLOW CAPACITY

compared with the initial full-volume ventilation concept.

The reduction was achieved through better utilization and distribution of conditioned air, rather than by compromising the required process ventilation conditions.

Contribution to Energy Efficiency

The 64% figure represents a reduction in required design airflow capacity, not a 64% reduction in total energy consumption.

However, reducing the required airflow capacity has a significant impact on the energy demand of the complete ventilation system.

Aircraft paint-hangar process air typically passes through several energy-intensive stages:

Filtration → Fan Transport → Heating / Cooling → Humidity Control → Supply → Extraction

Reducing unnecessary airflow therefore contributes to lower:

Fan Energy Demand
Heating Load
Cooling Load
Humidification and Dehumidification Demand
Overall Air-Handling Requirement

The low pressure drop of the Lindab RCW diffusers provides an additional contribution by minimizing terminal pressure losses within the supply-air system.

The optimized design therefore reduces the quantity of air that must be continuously transported and conditioned, making a substantial contribution to the overall energy efficiency and lifecycle operating cost of the facility.

Temperature & Humidity Conditions

Temperature and relative humidity are important process parameters in aircraft painting because they influence paint application, solvent evaporation, coating behaviour, curing and final surface quality.

Lindab RCW is designed to maintain its intended air distribution characteristics with supply-to-return temperature differences of up to:

Cooling: ΔT = –5 K
Heating: ΔT = +8 K
Heating-Up Operation: ΔT = +10 K

Temperature and humidity are controlled by the associated air-handling system, while the RCW units distribute the conditioned air according to the required aerodynamic conditions within the process zone.

Supply & Extraction Integration

The performance of an aircraft paint-hangar ventilation system cannot be evaluated from the supply-air terminals independently.

The final airflow field is determined by the interaction between:

Supply System + RCW Diffusers + Aircraft Geometry + Extraction System + Control Strategy

For this reason, the supply and extraction systems were considered as part of the same airflow concept.

The objective was to maintain the intended airflow path through the working zone and toward the extraction points while minimizing low-velocity and recirculation regions around the aircraft.

This system-level approach was incorporated into both the CFD analysis and the final airflow optimization.

From Engineering Design to Commissioning

Gerhman remained involved throughout the development and implementation of the air distribution system.

The engineering workflow followed a continuous design and verification process:

Process Requirements
→ Engineering Calculations & Selection
→ Lindab RCW Configuration
→ CFD Analysis
→ Zonal Airflow Optimization
→ System Implementation
→ Testing & Commissioning

This methodology was important because the actual performance of an aircraft paint hangar cannot be determined from individual diffuser catalogue data alone.

The complete system must be evaluated considering the interaction between the air distribution system, aircraft geometry, extraction arrangement and operating conditions.

Engineering Outcome

Through the Gerhman–Lindab cooperation, the initial full-volume ventilation concept was redesigned around the actual aerodynamic and process requirements of aircraft painting.

Gerhman’s engineering calculations and product-selection tools, combined with CFD analysis and Lindab RCW low-turbulence displacement diffusers, enabled conditioned air to be directed to the required aircraft zones with controlled velocity, direction and penetration.

The resulting design achieved an approximately:

64% Reduction in Required Airflow Capacity

while maintaining the required process-based airflow strategy.

The reduction in conditioned-air demand also makes a significant contribution to lower fan, heating, cooling and humidity-control energy requirements.

The project demonstrates an important principle of process ventilation engineering:

System efficiency depends not only on the quantity of air supplied, but on how effectively that air is distributed within the required process zone.

Project Highlights

Project: Pegasus Airlines – Aircraft Maintenance & Paint Hangars
Location: İstanbul Sabiha Gökçen International Airport, Türkiye
Client: Pegasus Airlines
Mechanical Subcontractor: Birleşim Mühendislik
Application: Aircraft Maintenance / Aircraft Painting / MRO
Maintenance Capacity: 4 Narrow-Body Aircraft
Paint Hangar Capacity: 1 Narrow-Body Aircraft
Engineering Cooperation: Gerhman × Lindab
Product Used: Lindab RCW – Low-Turbulence Displacement Diffuser
Design Methodology: Engineering Calculations · Product Selection Software · CFD Analysis · Process-Based Zoning
Airflow Strategy: Low-Turbulence Displacement Flow · Adjustable Air Direction · Variable Jet Penetration · Zonal Control
Key Engineering Result: 64% Reduction in Required Airflow Capacity
Energy Impact: Reduced conditioned-air demand with lower fan, heating, cooling and humidity-control requirements
Gerhman Scope: Engineering Design · Product Selection · CFD Analysis · Airflow Optimization · System Integration · Testing & Commissioning