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The Hurricane I with De-Havilland 5-20 Propellor is an early model with a two pitch propellor with only two settings, either fully fine or fully coarse.
Merlin II inline liquid cooled engine with Single Stage Supercharger, Full Throttle Height of 15,500 ft at +6.25 boost (unrammed horsepower figure)
Pilots should note this is an earlier generation Merlin engine, and is slightly less reliable than the later generation Merlin III type. Care should be exercised in the use and careful attention to rpms and temperatures.
Aircraft has a De-Havilland Two Speed Propellor, maximum rpms are not restricted by the propellor governor. Pilots will need to watch their engine rpms, especially in Fine pitch, (100% setting) to avoid over-revving their engine or damaging the Propellor governor. Pilots should use their throttle to keep rpms to a maximum of 3000 rpm. A “Do not Exceed” limit of 3600 rpm is in effect for dives. Exceeding this engine speed will very likely result in the destruction of the engine.
The two propellor settings available are either 'Fine Pitch', 100% in the game, or 'Coarse Pitch', which is 0% in the game.
Pilots will notice that in both Coarse and Fine Pitch rpms rise as altitude is gained, this is a natural result of how these aircraft's propeller settings were tuned. Maximum rpms in Coarse Pitch were designed to arrive at approximately Full Throttle Height, (+6.25 boost at 15,500 ft) to allow maximum speeds at those altitudes to be attained. For this reason, rpms and performance at lower levels are less than desirable. This is one of the compromises of a simple two pitch propeller system.
Fine pitch is only intended for use in takeoff and landing, and below 2,000ft, and only in climbs and slow speed maneuver at or below that altitude. Any attempt to use Fine Pitch at higher altitudes or in dives or in higher speed situations will result in excessive engine and governor rpms and the destruction of the engine.
Coarse pitch is intended to be used for most situations, including Climb, Dive, Level Flight and Combat Maneuver. Pilots will still need to watch their rpms, although the potential for over-revving the engine or prop governor is not as high as the rpms are more controllable.
Pilots may use this slower pitch change mechanism in the same way as the real RAF pilots did, as a means to mimic a variable pitch system and gain a bit of acceleration when Coarse Pitch rpms are very low. When the prop is in Coarse Pitch and the rpms are low, the pilot can engage the lever to change to Fine Pitch. The rpms will then rise as the blade angles change giving more bite to the prop and a brief burst of acceleration. Before the rpms reach 3000 and the engine over-revs, the Pilot should change the lever position back to Coarse Pitch, so that the Prop pitch reverses, and the engine goes back to lower RPM's. This technique is only recommended for use between 0- 10,000ft, or when at altitudes over 20,000ft. Extreme caution should be used to avoid over-revving the engine.
The aircraft has a liquid cooled, (All Glycol) engine. Shutters can be opened and closed by the pilot to regulate the Radiator coolant temperature. In addition the aircraft has an automatic Oil Cooler, which is not controlled by the pilot. Gauges for both Radiator and Oil Cooler temperatures are displayed on the right side of cockpit dashboard.
Note: Engine damage due to coolant or oil overheat CAN occur at lower than MAX temperatures. BEWARE of going close to those limits. Pay especial care when using +12 boost in low speed/high angle of attack manoeuvring.
Do not advance the throttle past 10% initially. Engine must be warmed prior to takeoff. Leave Radiator closed till following:
The Aircraft's radiator should be opened full before taxiing. The Hurricane is taxied using a combination of low engine power with applications of rudder and brakes providing the steering input. Pilots need to be very careful when applying brakes, as the aircraft can tip onto its nose easily. Pilots should use a 'fishtail' pattern during taxiing so they can see any obstacles in front of them.
The aircraft will accelerate slower than one with a Constant Speed Propellor and a long runway is required. No attempt to lift the aircraft off early should be made, it should fly off the ground naturally. Flaps may be deployed if pilots wish to shorten their takeoff distance, however they should beware the nose down attitude which will result after tail comes up, this must be controlled or the aircraft's propeller blades will contact the ground.
After takeoff, aircraft should be levelled out, undercarriage and flaps raised before any turns attempted.
The aircraft has trim for elevator and rudder. Pilots use the Sideslip Indicator on the right side of the cockpit dashboard to trim their rudder accurately. Needle should be centered. Pilots may also use the rudder to center the sideslip needle during combat for accurate shooting.
Max. Speed at Sea Level: 255 mph
Aircraft has a single stage supercharger, with the rammed Full Throttle Height, (FTH) being approx. 16250 ft at +6.25 boost. Performance falls off rapidly above this height.
The Hurricane I DH5-20 is a stable and manoeuvrable gun platform at low and medium altitudes although it is slower than the Bf-109 and Bf-110 at all altitudes. It will outturn 109's and 110's at low and medium altitudes. It loses performance at higher altitudes, especially over 25,000ft.
The engine is equipped with a carburetor which allows the pilot to select either 'Rich' (0%) or 'Lean' (100%) mixtures. 'Rich' mixture is used in all normal situations, takeoff, landing, climb, combat. 'Lean' mixture is only used to conserve fuel in level flight Cruise settings, and only when boost is set to '+1' or lower, and rpms to 2600 or lower. Use of 'Lean' mixture setting at higher rpms or boost will result in the destruction of the engine.
Pilots should exercise caution when pulling out of a high speed dive They should be cautious about using full elevator, especially with nose up elevator trim, and should be especially cautious when they have taken damage to their wings.