Townend ring
A Townend ring is a narrow-chord cowling ring fitted around the cylinders of an aircraft radial engine to reduce drag and improve cooling.It caused a reduction in the drag of radial engines and was widely used in high-speed designs of 1930–1935, before the long-chord NACA cowling came into general use.Despite suggestions of it exploiting the Meredith effect, low airspeeds, low temperature differences and small mass flows make that unlikely,[4] particularly when combined with the lack of flow control as the air exits the cowling.[5] Although superior to earlier cowlings, and uncowled engines in terms of drag and cooling, above 217 kn (402 km/h; 250 mph) the NACA cowling was more efficient and soon replaced it in general use.[6][failed verification] Examples of aircraft with Townend rings include the Boeing P-26 Peashooter, the Vickers Wellesley, the Fokker D.XVI and the central engine on the Junkers Ju 52/3m.
PZL Ł.2radial engineBritishNational Physical LaboratoryBoulton & Paul LtdNACA cowlingMeredith effectLuftwaffeNACA cowlingsBoeing P-26 PeashooterVickers WellesleyFokker D.XVIJunkers Ju 52AircraftsystemsAirframeAft pressure bulkheadCabane strutCanopyCrack arrestorCruciform tailEmpennageFabric coveringFairingFlying wiresFormerFuselageHardpointInterplane strutJury strutLeading edgeLift strutLongeronNacelleStabilizerStressed skinT-tailTailplaneTrailing edgeTwin tailV-tailVertical stabilizerWing rootWing tipWingboxFlight controlsAileronAirbrakeAutopilotCanardCentre stickDeceleronDive brakeDual controlElectro-hydraulic actuatorElevatorElevonFlaperonFlight control modesFly-by-wireGust lockRudder pedalsServo tabSide-stickSpoilerSpoileronStabilatorStick pusherStick shakerTrim tabWing warpingYaw damperAerodynamichigh-liftActive Aeroelastic WingAdaptive compliant wingAnti-shock bodyBlown flapChannel wingDrag-reducing aerospikeGouge flapGurney flapKrueger flapLeading-edge cuffLeading-edge droop flapStall stripsStrakeVariable-sweep wingVortex generatorVortilonWing fenceWingletAvionicflightinstrumentAir data boomAir data computerAircraft periscopeAirspeed indicatorAltimeterAnnunciator panelAstrodomeAttitude indicatorCompassCourse deviation indicatorFlight management systemGlass cockpitHead-up displayHeading indicatorHorizontal situation indicatorMulti-function displayPitot–static systemRadar altimeterTransponderTurn and slip indicatorVariometerYaw stringPropulsionfuel systemsAutothrottleDrop tankGascolatorInlet coneIntake rampNACA ductSelf-sealing fuel tankSplitter plate