A cowling is the removable covering of an aeroplane's engine; it is an engine covering and may also extend over part of the nacelles, the fuselage, or the cockpit. Located at the front - and sometimes the rear - of the fuselage, the cowl gives form to that section and channels air around and into the powerplant. Integral cowl flaps, small doors in the lower cowling, open during take-off and climb to admit extra cooling air.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is cowling in aviation?
Cowling is a removable metal covering that houses the engine, and it may be used for engine cooling by directing airflow. In aviation, a cowling is a removable cover that encloses an engine. It is a streamlined metal housing designed as a symmetric circular airfoil. The cowling surrounds engines mounted outside the fuselage, yet it remains an engine covering even if that motor is not inside a nacelle.
An example is the NACA cowling, a metal shroud designed for radial air-cooled engines. This streamlined shroud, developed by NACA, won the 1929 Collier Trophy and the National Aeronautic Association's award for the year's greatest achievement in American aviation. Its design uses slots and baffles to direct air over the crankcase; air enters the front, collects the heat produced in the combustion process, and exits through openings on the underside, greatly reducing both drag and cooling problems that a bare engine suffers.
What is the purpose of cowling of aircraft?
The purpose of cowlings is to protect the engine from physical damage and shield it from environmental elements. They form a protective shell around the powerplant, refining aerodynamics by reducing drag while also providing cooling. On airplanes, cowlings are used to cool the engine and streamline airflow outside the fuselage. A well-designed cowl channels air around and into the engine, acting as a ducted radiator to lower operating temperatures. Cowl flaps increase the flow of cooling air, collecting heat from combustion. They must be closed during descent to avoid added drag. The NACA cowling, a streamlined shroud, reduced drag, allowed airplanes to fly faster, and increased lift coefficient of the wing. Modern fighter jets' cowlings are engineered for stealth capabilities, minimizing radar signatures while maximizing performance under extreme conditions. Special composite materials refine strength and reduce vibration of the engine cowling. Cowlings allow easier access during maintenance.
Where is the cowling located on a plane?
On a single-engine airplane the cowling wraps around the entire engine that is mounted in the nose, giving form to the front of the fuselage and separating the passenger compartment from the powerplant. On multi-engine aircraft each nacelle carries its own engine and therefore its own cowling; the cowling here covers the whole covering of an engine that is outside the plane, typically on the wing, and extends over part of the fuselage, the nacelles, the engine mount and part of the cockpit.
Within every engine cowling, whether nose-mounted or nacelle-mounted, the movable engine-cooling components are found at the bottom: cowl flaps are small doors located at the bottom of the engine cowling and are movable extensions of the lower engine cowling, are typically mounted on the lower section of the nacelle. On multi-engine aircraft each nacelle carries its own set of cowl flaps positioned along the lower cowling. The pilot manages these cowl flaps from the cockpit through controls located on the pilot's left lower side panel, while the related cowl-flap circuit breakers are on the co-pilot's right upper side panel in the bottom two rows labeled Engine & Fuel Systems.
