Pelican's Perch #73:
Hurricane (Part 1)
It still gets less press than its more-famous compatriot, the Spitfire, but the Hawker Hurricane was the mainstay of the British fighter squadrons in the European theater of World War II. AVweb's John Deakin considers it one of his favorites, and his two-part pilot report begins this month.
No, not the windstorm after which it is named, but the Hawker Hurricane, the airplane credited with winning the Battle of Britain (although the Spitfire got more publicity). Most reports show the Hurricane with more kills than all other aircraft combined.
As one British friend mournfully told me, "John, old boy, if you're going to fly it, you really ought to pronounce it properly, it's "HURR-ic'n," not "Hurri-CANE." Point taken. I call it "The Hurry," and he gets a pained look at that, too.
As I wrote in July (Pelican's Perch #71), the Southern California Wing of the Commemorative Air Force now has 13 aircraft, including three priceless WWII aircraft on lease from the owner, the Museum of Flying at Santa Monica: the Mitsubishi A6M3 "Zero," the Supermarine Mark XIV "Spitfire," and the subject of this column, the Hawker Mark XII "Hurricane."
(All is not peaches and roses, however; all three are "down" at this writing: the Zero with fried wires in the electrical control panel, the Hurricane with a phantom oil loss, and the Spitfire with a blown coolant line. Not to worry, we'll have them going again soon!)
I always have a soft spot in my heart for funky airplanes, or those that are difficult to fly, or that have "endearing quirks." The Hurricane may become my favorite, after the C-46. It has the usual dreadful British cockpit layout, with "stuff" scattered all over the place, oddball ways of doing things (at least by American standards), and the appearance of a boiler factory from the nineteenth century. As usual with the old aircraft, I find it truly remarkable that young men actually went into combat in these aircraft.
Like many WWII aircraft, the production history is very complicated. Hawker, Gloster and the Austin Motor Company made Hurricanes in several different factories in England, and the Canadian Car & Foundry Company made them in Montreal and Ontario, in Canada. There was a bewildering variety of modifications and model numbers. There is a Web site devoted to Hurricanes, and a Google search will show a lot more.
According to information on that site, the airplane was manufactured as part of a batch of 1,700 by Gloster Aircraft Co. between July 1940 and August 1941, as a Mark IIB aircraft, with a Rolls-Royce Merlin (III or XX) engine, driving either a Rotol or deHavilland prop.
However, the Museum of Flying in Santa Monica shows a very different history for this aircraft, stating that it was made by the "Canadian Car and Foundry Company," in Montreal.
In September and October of 1991, two RAF test pilots conducted about 10 test flights on this aircraft, then registered in England as G-ORGI, and owned by "Charles Church Displays, Inc." It appears this might have been the point at which the airplane became a civilian.
The introduction to their report states:
"The aircraft was in excellent condition, having just been extensively rebuilt. It has been fitted with an injected Rolls Royce 500-224 Merlin engine, and a four bladed Rotol R5/4F5-4 propeller (from a Spitfire Mk IX.) Both internally and externally, the aircraft was very clean, with no oil, fuel or coolant leaks. The external finish was primer and silver dope."
There was some confusion here, because there is probably no such thing as a "500-224" -- those are two different engines. It was probably a 500, as it is now.
|Propeller Blade Markings|
Assuming those two pilots could both count to four and agree, then somewhere along the line that four-bladed prop has been replaced with a very lightweight three-bladed wooden prop, marked "Dowty-Rotol." The prop is "interesting" because it has so little rotating mass compared to the metal props on most big engines, which act as flywheels. It is very noticeable when trying to start the engine. The prop "jerks" through each compression stroke, and if the start is botched, the prop stops almost instantly, rather than coasting to a stop, as do the heavier metal props. With the metal props, that "coasting" will often provide an opportunity for the engine to "catch," and start. On this one, the engine not only needs to "catch," but continue running smoothly. Prop rotation stops almost instantly on shutdown, for the same reason. It's also scary in flight and on the landing roll, because the RPM drops very sharply during any low-power, low-speed operation, and the prop looks for all the world as if it's just about to stop. The prop turns at 47.7% of the engine speed, so at an idle RPM of 600, the prop is only turning about 290 RPM. It seems like you can almost count the blades as they go by. I haven't yet had the courage to do a power-off stall for that reason.
The FAA is confused, too. The current paperwork shows it as a "Hawker-Siddelley Mk XII Hurricane." That's a little like saying "Boeing DC-3," which I will never accept. Of course, I'm still fighting the change from "P-51" to "F-51."
Too Many Engine Possibilities
If the history of the airplane is confused, the histories of the engines are even worse! Whole books have been written about them, and even Rolls Royce got some details wrong, in a 1953 report they published.
So, just what engine do we have in this airplane? All I can tell you for certain is that it's a big, red, nice-looking V-12 that fills the engine compartment to the last inch, and it runs beautifully, sounds great, and produces a highly satisfying feeling when you shove the throttle up on takeoff.
The current engine data plate shows:
|TYPE MERLIN 500 / 45 306773
RIGHT HAND TRACTOR
|Engine data plate
(click photos for larger versions)
The bold print is molded into the data plate, very faded and worn, while the "45 306773" is stamped, cut right into it. That's probably the way it came from the factory, but who knows what kind of heads it has -- and what innards have been changed -- without an extensive search of the records. Even that might not clarify things. The story is that it has about 200 more HP than the original, but horsepower is confusing, too.
In addition to a bewildering number of aircraft models built in different factories, a large number of different engines were installed by each factory; and in later years, engines were swapped for later models, too. It is not likely that any Hurricane came from the factory with a 500-series engine, but modern operators are faced with massive problems trying for "authenticity."
For more on this subject, Graham White, a world-renowned aircraft engine historian, runs a wonderful Web site. See the sidebar for comments from him.
Construction and Preflight
The Hurricane fuselage is of steel-tube construction for the frame, with metal skin forward of the cockpit. The skin aft of the cockpit is fabric, with a series of very light wood and fabric panels. About five minutes with a screwdriver will lay the important innards of the airplane bare for inspection and maintenance -- a very nice feature. Some of the early models had fabric-covered wings, but the wings on this one are all metal.
I start my external preflight at the left-wing root, trailing edge. The boarding step is spring loaded to the retract position, but a gentle pull will extend it for use, where it remains. Pulling it down also automatically opens the little flap covering the handhold about three feet above the step. Closing that flap (gently, please) releases the step so that it retracts again. Very clever. It's also a fairly fragile mechanism, so we're very alert for those who start to mess with it.
|Water Tank and Pump|
The large inspection panel just above the step must be opened to allow inspection and refilling of the water tank, which is not original equipment. This water is used for a "spray bar," which floods the coolant radiator, providing much-needed additional cooling of both coolant (glycol) and oil.
The water tank holds about 17 gallons, and just plain clean water from a hose will do nicely. Note this is not "water injection," or "Anti-Detonation Injection" (ADI). The spray bar is used during long ground holds, and at high power settings in flight. Many "hot water twelves" develop very high coolant temperatures, and I can't help but wonder how they managed in wartime, without the spraybars. I'd guess they didn't suffer the long ground holds we do today with ATC, and in fact, most of the time they were probably in something of a hurry to take off, so high coolant temps on the ground were probably not an issue. I don't know if they just accepted the high temps in flight, or if perhaps the radiator on this particular airplane might not be working quite as well as the originals. It is common during radiator overhauls to plug any passages that leak, and it doesn't take much of that to reduce efficiency. In any event, the spray of water makes a big difference, and allows control of the temperatures very well, although it does take some attention. I don't have a handle on how long the water will last, so it's been "one fill, one flight," so far. That does seem to use most of the water. We'll nail that down soon. There is no question when the water is running: The cockpit humidity jumps instantly, and there is that familiar smell of water being sprayed on hot metal with traces of oil and coolant mixed in. Ahhh, a lovely smell.
Which leads to an interesting thought. If I can so quickly smell the spray bars working, where would the flames from a fire go? Maybe we ought not to think about that, scratch the thought. There is always the parachute, of course, but the standard remark in warbird circles is, "You bail out of one of these priceless antiques, you'd better keep on running, because if we catch you, we'll kill you!"
|Landing Light Detail|
Walking clockwise around the aircraft, there is nothing remarkable about preflight of the wing, until arriving at the landing light. The first time I saw it, I thought the mounting was broken, but upon closer inspection, I realized it moves! Some designer went to a lot of trouble with this item. In the original airplane, the landing lights were used one at a time, controlled by a three-position switch. A "dipping lever" adjusted the aim, and a knurled knob locked the lever in place. Loosening the knob would allow the spring-loaded lever to move to the up position.
Note the odd bulb mount, too. The mirror is an unbroken concave shape, with the bulb socket out in front. Looks like it would be a bear to change that bulb -- you'd need to disassemble the wing first!
Inboard of the left landing light and main gear at the leading edge wing root, we find the engine oil reservoir. It seems a little odd to find the oil tank there, but at least it's easy to inspect and service. The oil cap is identical to all three fuel caps, and a large red tool (inset) is carried in the storage compartment behind the pilot's head.
|Left Side Engine & Cockpit Panel Off|
The two (aluminum) panels on the left side of the engine are not normally removed for preflight, but they have been removed here to chase down an elusive oil leak. The "Batwings" are shields to prevent the exhaust flames from blinding the pilot at night (exhaust flames from a big engine at night are spectacular!) The "reserve" fuel tank holds 28 gallons, and is located right over the pilot's feet. This is not one of my favorite locations for fuel, as I prefer not to share the cockpit with fuel in any kind of accident. Somewhere in the back of my mind, firmly repressed, is a niggling little thought that they might have done better to put the fuel in the wings, and the oil where the fuel tank is, but I don't think about that much. I'm sure they must have had their reasons. I'll probably fill that tank for cross-countries, but not for local flights or air shows.
|Air Scoop (rear view)|
Here's a really critical part of any airplane with a liquid-cooled engine. The large radiator is for the coolant, and the small circular one is for the oil. There is a large, manual exit door at the rear of the scoop, but for most flights, the door is left fully open at all times. Oil temperature doesn't seem to be a problem, but the coolant temperature seems to run very high. I'm wondering if playing with the exit door position might produce a more favorable air flow and better cooling, but I haven't flown it enough to experiment, yet.
|Air Filler Valve|
Wheel wells are often very interesting places on airplanes, and this one is no exception, with several points of interest. The brakes (and the inoperative gun-firing mechanism) on this airplane are pneumatic, and while the very small engine-driven air pump will produce enough air to recharge the system, it's a slow process at taxi RPM. It is very important to turn the air on during preflight and check the pressure gauge during taxi -- often. If it's below about 180 PSI, this is the place to fill it.
("Air" is something of a misnomer around airplanes: Nitrogen is the preferred substance. It is inert, dry, and doesn't contain oxygen. The only place real air is suitable is in tires, and the airlines generally use nitrogen there too, most likely because nitrogen at high pressure is readily available, and air generally isn't.)
|Wheel Well Forward & Air Tank|
In the front of the wheel well the rather small, main-system air tank can be seen. This is where air under pressure is stored for the brakes. The British were very fond of air brakes for some reason, while we generally favored the use of hydraulics, with master and slave cylinders -- a much simpler system. The fuel sump is barely visible just below the left landing gear actuator.
While at the right wing root, leading edge, it is best to stand on the right main tire and reach back to check the fuel in the right wing tank. There is no wingwalk, and no handles or footsteps to climb up on the right wing from the trailing edge. The only other way to reach the right wing gas cap is to board on the left, climb through the cockpit and out onto the right wing, stepping very carefully to avoid the soft spots.
|Wood and Fabric Panel|
Walking around the right wing shows little of interest until we come to the trailing edge wing root. Here there are two wood and fabric panels, and at least the rear one must be removed for a proper preflight inspection.
|Battery and Hobbs Meter|
Looking past the battery at the inside of the left fuselage skin, the wood and fabric construction can be seen clearly, as well as the basic tubular steel frame.
The battery is vented through a small glass jar half-full of baking soda, which reduces the acid in that airstream. The little circles at the bottom of the panel are where the "Panel Buttons" fasten the panel to the airplane.
With a flashlight, and only a small contortion, the emergency air-tank pressure gauge can be checked through this panel, so it's not really necessary to remove the next panel forward. However, for this column, the next photo shows what it looks like:
|Emergency Air Bottle|
This is the backup for the pneumatic brakes. Better than nothing, but it scares me, a little. Picture this: You're taxiing along, and suddenly realize you're not getting normal braking. You reach down and pull the emergency air handle, and suddenly you have brakes again, with a vengeance. The tail is VERY light on this airplane, and you'll almost certainly put the airplane on its nose, destroying that very expensive, hand-made prop. Keep checkin' that main system air pressure, and don't get in any position where you'll need brakes in a hurry!
|Right Main Gear|
Nothing unusual here at the main gear, except that a peek for leaking hydraulic fluid won't accomplish much (pneumatic brakes, remember?). Tire -- er, "tyre" -- condition, strut extension, general condition, as with any airplane.
After we reinstall the right side panels, we continue back towards the tail. Nothing remarkable, although I suspect that there were some flutter problems on the rudder trim tab, necessitating the counterbalance devices you see here.
|Tail Tied Down|
The tailwheel does not retract on this airplane. The lifting point is a tube that runs all the way through the airplane, and is welded firmly to the frame. This can be used to lift the tail when hoisting the airplane by passing a steel bar through, and securing each end. It's also used for high-power runups, as shown here. The steel bar is simply chained or strapped to a good solid anchor point in the concrete. The brakes are sufficient to hold the airplane for slightly more than the 1700 RPM for the normal prop and mag check, but if much more power is applied, either the tail will rise, or the brakes will slip, unless tied down.
The next part of the preflight is to climb up on the left wing, check the fuel in the left wing and center fuselage tanks, and then climb through the cockpit to the right wing, because I usually forget to check that fuel from the leading edge when I passed by.
No, the control stick isn't broken -- it's British. Big circular grip, and hinged very high on the stick. You'd think it would feel funny in flight, but it's quite natural and transparent to the new pilot. It does seem like a complicated way to accomplish the purpose. The picture shows full left-wing-down aileron.
|Brake Air Pressure Gauge|
This picture shows the front of the circular grip on the control stick, with a brake handle that looks like it came from a bicycle. When holding the grip with the right hand, the brake handle falls nicely under two or three fingers, and is very easy to actuate and regulate. What is a bit strange is that differential braking is accomplished by moving the rudder pedals, along with squeezing the brake handle. This is very disconcerting at first, but becomes quite natural with time -- say, 10,000 hours. No, just joking, it's not bad, it just takes a bit more attention. There is an air-pressure gauge on the floor (lower picture), with one large, white, fixed needle showing max. system pressure, another large needle showing actual system pressure, and two smaller needles, each showing the actual pressure being applied to the respective brake. When holding the brake handle fully on for runup, moving the rudder will change the individual air pressures, and full rudder will reduce the opposite brake to zero. It is important to hold the rudder pedals centered when doing a runup!
The parking brake consists of a tiny lever that engages a small pin (barely visible) on the brake lever, holding it "squeezed." It seems to work well enough, but I prefer to hold the brake on while doing the runup. I'll trust the big, hydraulic "power brakes" on larger aircraft, but not those on non-power systems. I did (once) set the parking brake for shutdown, then turned off the master air valve. After fueling, we started to push it into the hangar (no towbar, yet), and with about ten guys pushing, it was really hard to move (some air had probably bled off). It is a rather heavy airplane, and everyone thought everyone else was slacking off. Someone yelled, "Feels like the parking brake is on!" Oh, did I hear about that, as I sheepishly clambered up and released it! There is no mercy on our ramp. Every time we've moved it since then, some smartass will yell, "Hey, see if Deakin left the parking brake on, again!"
|Cooler Door Handle|
This view is straight down, on the left side of the seat, and shows the large handle for moving the big air exit door at the back of the scoop.
|Cockpit Left Sidewall|
|Throttle, Prop, and Mixture Controls|
The electrical instruments and switches are reasonably located at the pilot's left elbow, and move toward the pilot for "On."
The throttle is aggressively spring-loaded to the closed position, so it takes a hard twist on the friction knob to keep it in place at high power settings. The radio PTT ("Push to Talk") button is on the end of the throttle, under the thumb.
The mixture control is odd. It doesn't seem to move very far, and has only two positions, "Idle Cutoff," and "Run." Mixture control is automatic. There is a yellow safety latch (barely visible in the close-up) that prevents inadvertently pulling the mixture all the way back, which would kill the engine. But if the start is missed, that latch is a real annoyance, because the mixture must be immediately returned to the off position to keep from flooding the engine. Nothing two more hands wouldn't cure.
The fuel valve has the usual "Left," "Right," and "Fuselage" positions, with a safety tab to prevent "Inadvertent Off."
The air valve is the master air shutoff, trapping the air (nitrogen) in the main tank while the aircraft is parked. If this airplane is parked for more than a couple weeks, that main air reservoir will need pumping up from the filler in the wheel well.
The "PreOil" switch is a "modern" add-on device. This is turned on for several minutes before starting a cold engine. It runs a small electric motor that drives an oil pump to circulate engine oil under pressure throughout the engine, but especially on the "fingers" (rocker arms) that ride directly on the cams and rod ends. These are critical parts in the big Merlins, and getting some oil on them before turning the engine saves a lot of wear and tear. Allisons have "roller rockers," and are far less troublesome.
The mags are simple toggle switches, one for the left, one for the right. To the left of those are two push-buttons, one for the starter, one for the ignition booster coil, which gives a hotter spark for the start. Both must be pushed together, both are pretty stiff, and they are located where it's difficult to get the fingers on them with enough force to do the job. Oh, the hardship of flying these old airplanes!
All the way down on the floorboards is a yellow and black striped handle, and this is the emergency gear (uplock) release. It is intended to be operated by moving it with the left foot, as it is basically unreachable by even an Orangutan.
Manifold pressure is automatically limited to 12 lbs. sq. in. in this engine, but for emergency use, that feature can be cut out with the "Automatic Boost Cutout." Yes, I said "pounds per square inch," and not "inches of mercury" so common in the USA. The manifold pressure gauge is marked so that "0" is ambient pressure. At less than ambient pressure, "Boost" is negative (about -6 at idle), and at higher power settings, "Boost" is positive. There are 2.036 inches of mercury to each 1 pound per square inch, so a takeoff "Boost" of 12.0 is equivalent to 54.35 inches of manifold pressure at sea level (12 x 2.036 + 29.92). All this is of little consequence, because we just use the appropriate "Boost" numbers.
The "Supercharger Control" for the two-speed, gear-driven supercharger is simply a push-pull knob, in for low gear (low altitude), out for high (high altitude).
Moving to the right instrument panel, we see the tachometer, also a bit strange, because the big hand indicates hundreds of RPM, and the little hand thousands. For takeoff RPM (3,000), the big hand is on the "0", and the little hand on the "3". This instrument is also well up under the glareshield, and a bit difficult for the pilot to see.
|Primer & Fuel Pressure Gauge|
These very small gauges (and oil pressure, not shown) are probably the most important instruments in the cockpit, for they directly reflect the happiness of a monster engine. They must be constantly checked in flight, and controlled by airflow and power. In 1960, a main oil line blew out right under the cockpit of an A-36 Mustang (N4607V) I was flying, and I literally saw the pressure fall just before the cockpit filled with hot oil and smoke. I shut the engine down instantly and toggled the Curtis Electric prop back to minimum RPM, but by the time I was able to dead-stick the airplane from 11,000 feet, the engine was locked up tight in less than two minutes, from lack of lubrication.
|Cockpit Front Right|
The seat-adjust lever is a real bear-trap, guaranteed to literally mangle your fingers if carelessly used. The trick is to grab it tight, hold on, lift it a bit to take the load off, depress the push-button on the end, and lower it slowly to lower the whole seat. As the lever gets down alongside the seat, move your fingers to keep them out of harm's way of the various components down there.
|Gear and Flap Handles|
Way back in the late 30s, someone at Hawker said, "Hey, let's make a single handle for both gear and flaps!" And they did. It moves within an "H" shaped cutout, and works well enough. There is a red safety latch that prevents motion into the "Gear Up" position, and this is turned 90 degrees clockwise just before takeoff. When the handle is pulled left, and then up, it flips the safety to the safe position and retracts the gear (before reaching 103 knots, please). After the gear is up, the handle is placed back in neutral. Doing that pushes past the safety, but doesn't turn it enough to re-arm the thing. It is also necessary to move the lever safety anytime the handle is used for either flaps or gear. The handle is pictured in the "Flaps Up" position.
The switch and green light to the right of the gear/flaps lever is for the "Aux Cooling" system -- the spray bars -- and is not original equipment, of course.
|Cockpit Right Rear and Seat|
Not much to see on right sidewall, except for the jettison handle that pops out the panel by the pilot's left side. This, together with the canopy jettison, gives the pilot a better chance of getting out in a crisis.
We'll get into the flying part next month!
Be careful up there ...