The Sea Hurricane 1B
Resting silently on a flying day, waiting for her chance to perform, the Collection’s beautifully restored Sea Hurricane is an aviation enthusiast’s dream. This surely is what Old Warden is all about. But if you listen carefully to those who have flown her, you may hear rumours that all is not so rosy. Here is a pilot’s view.
The Shuttleworth Collection’s Sea Hurricane 1b, Z7015, was originally built in Canada as a Hurricane Mk1 by the Canadian Car and Foundry Company at Kingston, Ontario in 1940. She was then shipped to the UK and converted to a Sea Hurricane 1B. Z7015 was initially issued to No 880 Squadron; the first Fleet Air Arm Squadron to be equipped with Hurricanes and later she served with No 759 Squadron. At the end of 1943, she was delivered to Loughborough College and served as a ground instructional airframe for the next 18 years. Z7015 was used as a taxiing aircraft in the film The Battle of Britain and was eventually fully restored to flying condition jointly by SVAS volunteers and the Imperial War Museum. In fact, Loughborough College was persuaded to swap both the Sea Hurricane and our Spitfire AR501 for a prototype Jet Provost and a Flying Bomb. Not a bad deal if you ask me! Z7015 flew again for the first time in 1995. She is a unique aircraft, the airframe and its Merlin III engine being the earliest airworthy examples in the world. From a handling point of view, she is one of the Collection’s most interesting types.
The Sea Hurricane is a solid, workmanlike aircraft. It is physically larger than its Battle of Britain brother, the Spitfire, and harks back to an older generation of aircraft. Whilst the Spitfire was designed around an all metal stressed skin monocoque fuselage with a thin wing for aerodynamic efficiency, the Hurricane has a more traditional Hawker style tubular steel framed fuselage seen on types such as the Hart, Hind and Fury, the rear portion of which is fabric covered. The Hurricane wing is extremely thick and the aircraft exudes an impression that it is built to take a few knocks. In many ways, the Hurricane is at the end of the design process that gave us the great biplane fighters whilst the Spitfire was a much more revolutionary design for it’s time. Hence the scope for the latter to be developed extensively during the Second World War, only being eclipsed when the advanced Griffon engine that powered the later versions was superseded by the jet engine. Of course, much has been written about the history of Hurricane, but what is the Shuttleworth example like to fly today?
It’s a long way up on to the wing of the Hurricane, and there is a pull down step to the rear of the trailing edge to help the pilot. The step retracts when a cover over the fuselage handhold is returned to the flush position, a feature that will be familiar to anyone who has flown the current RAF Hawk trainer. Unlike the Spitfire, the cockpit has no hinged side panel and it is entered by climbing on to a second step below the coaming. The cockpit entry is fairly tight but once inside, the lower cockpit is seen to widen out to give a roomy working environment. Seat and rudder pedals are easily adjusted and it is immediately apparent that the view over the nose is far better than in the Spitfire. I normally lock the sliding canopy open at this stage and take care to tuck the loose ends of the harness straps under the shoulder straps. If this is not done, they will flap around wildly during the take off roll with the canopy open. Like most aircraft of this era, the cockpit is arranged rather haphazardly and anything accidentally dropped will be lost in the bowels of the aircraft.
I scan the cockpit from left to right, although in practise the checks are fairly simple. Having checked the flying controls, pneumatics, trim, undercarriage lever, throttle, mixture, RPM lever, fuel cock/contents, radiator flap, ignition, instruments and radio it is time to connect external power and pre oil the engine. The latter involves activating a small electrically powered oil pump to get oil up to the camshafts before the engine is started. The pump is a later modification and is required as at Old Warden the engine may stand for a couple of weeks or more between outings. Operationally, such breaks were rare, and if necessary, the pre oiling would be conducted by the mechanics removing rocker box covers etc. Obviously an impractical way to operate the aircraft nowadays when flown at widely spaced intervals. The engine is fuel primed manually by the pilot using a Ki-Gass pump; about 4 shots are usually sufficient for a cold engine. With the throttle set to ½” open, magnetos (including starting magneto) on and fuel selected to reserve tank, the booster coil and starter button are pressed and after a few blades and clouds of exhaust the Merlin crackles into life. Oil pressure should rise immediately, perhaps as high as 110 psi if the engine is cold, and having checked this I normally set about 1000 RPM to warm the engine after waving away the external power. The growl of the Merlin is a wonderful sound and at this stage the excitement of the flight always starts to mount. I normally check the fuel flow on main tanks briefly although I reselect reserve tank for takeoff as this will give a greater head of fuel pressure. The starting magneto is now turned off and the Ki-Gass pump screwed firmly shut. The pneumatic brakes are pressurised by the engine and they are rechecked at this stage. The pneumatics were also used operationally for the eight Browning .303 machine guns (later Sea Hurricanes being armed with 20mm canon). The aircraft has a simple hydraulic system that operates the flaps and undercarriage (unlike the Spitfire, where the flaps are pneumatically operated). The lever that controls these services is on the right side of the cockpit and looks a bit like an H shift gear stick. The left side of the H controls the undercarriage and the right the flaps. With the lever in the centre, the hydraulic pump is idling and pressure is low. To select a service up or down, the lever is moved to the corresponding side of the gate and then forward or backward as required. However, once the gear or flaps have reached their desired position, the lever must be moved back to the neutral position to return the pump to idle and prevent possible hydraulic failure due to over pressurisation. There are obviously several traps with this design, the main one being that a hasty pilot could move the undercarriage instead of the flap. Also, once the flap or undercarriage has travelled, the position of the lever does not indicate flap or undercarriage position. Hence it is with great care that I check the flaps, first moving the lever outboard, down, watching the flaps move on a strip gauge behind the flap/gear selector and then moving the lever back to idle when the flaps reach the desired position. Having checked the flaps, they are then retracted by reversing the process. Engine run-ups are commenced when the radiator temperature has reached 60 deg C and comprise the standard checks of mag drop, RPM control and idle. Unlike the Spitfire MkV, the Hurricane has its radiator fully in the propwash and is not prone to overheating on the ground. Hence there is not such a sense of urgency to taxy out and get airborne.
The Hurricane is easy to taxy, with a good view ahead for this class of aircraft. The brakes are reasonably effective and the aircraft is not as tail light as the Spitfire, where care has to be taken to avoid harsh use of power or brakes when taxiing. Apart from the standard pre takeoff checks, there is a small rotating gate on the undercarriage selector that I rotate out of the way. This is designed to prevent inadvertent undercarriage retraction on the ground and is moved out of position just before take off. The Merlin III in the Sea hurricane develops only about 850hp at sea level (compared to the Spitfire V’s 1585hp) and hence full power is required to drag the aircraft into the air. As the throttle is opened the engine note rises to a crescendo. The stick is held forward to bring the tail up as soon as possible and there is only a small swing to the left which is easily controlled. This compares favourably with the Spitfire, which needs relatively coarse rudder inputs to keep straight, especially if power is advanced too quickly or the tail raised too rapidly, the latter causing a swing due to gyroscopic precession. However, it is at this stage that the Hurricane pilot needs to concentrate. Although the aircraft is easy to keep straight, she is unstable in pitch, especially at low speed, and care is required to hold a precise take off attitude without over controlling, a characteristic that is not helped by any bumps in the runway. The saving grace here is that the smaller propeller gives better ground clearance than in the Spitfire and hence a small error in raising the tail too high will not have the disastrous consequences of a prop strike.
I scan the engine instruments, which are all grouped conveniently together on the right side of the cockpit, checking mainly boost (+6.25 psi) and RPM (2850 rpm), whilst concentrating on holding the correct attitude as the aircraft flies off at about 80kts. Being a naval aircraft, the ASI is calibrated in knots rather than the Spitfire’s mph. Once airborne, the pitch instability is particularly noticeable and great care is required to keep the aircraft’s nose at the correct climbout attitude as gear is selected up. As the aircraft is allowed to accelerate to about 100kts, I check that the throttle friction is extremely tight, change hands on the stick and raise the undercarriage. In addition to careful operation of the hydraulics, as previously described, it is important to confirm the correct undercarriage indications, as they are somewhat different to those of a modern aircraft. Modern day pilots are used to seeing green lights for gear down, orange in transit and no lights when the gear is up. However, for the Hurricane (and, incidentally, the Spitfire) whilst green still indicates down, orange now means locked up and no lights would indicate a partially retracted, possibly failed undercarriage. Hence it is extremely important to check these indications carefully. With the aircraft safely cleaned up and accelerating to the climb speed of 150kts, it is merely necessary to reduce boost to about +4 psi and RPM to 2600 and transfer to main fuel tanks whilst quickly scanning temperatures and pressures to confirm that all is still well. Unlike the Spitfire, intermediate flap settings are available for takeoff although my preference at Old Warden is to take off flapless. The advantages of some flap down for takeoff are a slightly shorter ground roll and more pitch stability as the tail is raised.
So we are safely airborne, but what is she like to fly up and away? Well, classic aircraft that she is, I find that the handling is dominated by the pitch instability to a detrimental effect. Let me explain. All aircraft have varying degrees of pitch stability. If an aircraft is trimmed for a particular speed, and then accelerates, the pilot (if he does not retrim) will have to apply forward pressure to the control column to maintain a level flight path as speed increases. This means that he can feel what the aircraft is doing, and if the nose should drop in flight, the resulting speed increase will then work through the natural stability of the aircraft to bring the pitch attitude back to where it was. Of course, a fighter aircraft should not have too much stability, as control forces become excessive during manoeuvres that produce large speed changes and the pilot must trim rapidly during accelerations to keep such forces manageable. However, an aircraft that is slightly longitudinally unstable, although clearly flyable, requires constant attention from the pilot to keep it pointing where he wants it to go. This is most apparent in the Hurricane during a display when a tight turn is flown and the pilot finds the aircraft tightening into the turn. Here, since the turn is flown at constant power (to conserve engine life), the increased drag causes the speed to drop. Normally, the pilot would expect to have to pull back more on the stick in this case to maintain the turn and to recover from the turn by relaxing the back pressure. However, the Hurricane tightens up and requires a push force to relax the turn.
None of this is a major problem but it feels unusual to pilots who only fly the aircraft occasionally. I’m sure that in the 1940s a current wartime Hurricane pilot would get so used to these characteristics that he would quickly learn to compensate and in many ways these handling qualities would have allowed him to manoeuvre more aggressively during combat. However, any pilot trained on modern aircraft would certainly be surprised at first by the pitch characteristics of Z7015. In all other respects, the Hurricane generally handles nicely with well-harmonised controls and a good roll rate. The stall is benign both clean and with flap down and the aircraft will only drop a wing at the stall if encouraged by ignoring the many standard stall-warning symptoms. Like many aircraft of this era, sideslip causes a marked nose down pitching moment due to blanking of the tailplane by the fuselage although in practice the relatively short nose and highly effective flaps make deliberate sideslip on the approach generally unnecessary. The engine handling characteristics are good although being any early mark of Merlin, she will not tolerate much negative g without coughing in protest. Unfortunately, our Hurricane is not cleared for aerobatics although I would imagine that with a little practise on the part of the pilot she could perform a lively aerobatic display.
Before landing, Reserve tank is reselected, the RPM increased to maximum and the brake pressure and radiator temperature carefully checked. The undercarriage is lowered at about 95kts (the limiting speed for gear and flaps is fairly low at 104kts) and a curving approach flown at about 85kts from a down wind height of 800ft. The approach is not so critical as in the Spitfire, where the final turn should not be started beyond a point abeam the threshold. This is because a straight final approach in the Spitfire severely degrades the view of the threshold and can lead to overheating as the undercarriage and flap disrupts the cooling airflow into the radiator. Neither of these problems manifests itself in the Hurricane. I normally lower the flap about one third of the way around the finals turn. This produces a strong nose down trim change which is easily corrected. The view ahead on landing is reasonably good and as the threshold is crossed at 75kts the aircraft is eased into the three-point attitude. The elevator is powerful and it is possible to land tail first, although this is not dangerous. It is also important to make sure that the mixture is fully rich or the throttle can snag on the mixture control preventing the pilot from fully selecting idle. This caught me out the first time I flew the aircraft and will increase the landing roll. Once on the ground, it is merely a matter of keeping straight with rudder and brake whilst holding the stick hard back to get weight on the tailwheel. The aircraft is reasonably tolerant of crosswind although the brakes are prone to fading and are not good in the wet.
After landing, I take great care to check that I have correctly identified the flap side of the flap/undercarriage gate before moving the lever to retract the flaps. The radiator is usually comfortably cool enough to allow an unhurried taxy back during which the fortunate pilot is able to reflect on what it may have been like to fly such a famous and historic aircraft in the desperate days of the Battle of Britain.
So how can I summarise the Sea Hurricane, and in particular her much discussed (amongst collection pilots) handling characteristics? For an airshow pilot flying the aircraft occasionally, the poor longitudinal stability demands a cautious approach when manoeuvring hard close to the ground. However, I would imagine that a fully current Hurricane pilot with a few recent hours on type would soon have been able to turn such characteristics to his advantage in the aggressive combat encounters of the Battle of Britain. As for myself, I can only consider myself fortunate enough to learn this at first hand.