Spitfire Flight Test

In a recent re-issue of a special magazine by Key Publishing featuring military aircraft flight tests, Dave Unwin takes aloft the legendary Spitfire

As the Spitfire sliced skyward with the roar of the mighty Merlin thundering in my ears I couldn’t help sneaking a glance at the evocative elliptical wing.  I’m back in the cockpit of a Spitfire – but this time I’m sitting in the front!  Can it get any better?  I’ve waited two years for this moment, but as I merely think about turning and the Spitfire responds to my every whim, I know it’s been worth the wait!

Before going anywhere near the Spitfire, Aircraft Restoration Company Chief John Romain sat me down for a briefing.  John is one of those great instructors that has the rare gift of being able to impart a phenomenal amount of information clearly and succinctly – he promptly reminded me of the salient points.  (As I’d spent most of the previous week reading my copy of the ‘Pilot’s Notes’ for the Spitfire Mk IX from cover to cover this didn’t take long!)

While I waited for John to finish the other 101 tasks he was attending to that morning (he must be the busiest bloke I know), I decided to walk around the Spitfire and examine it as if I were preparing to write a full flight test of a new type.

As I strode out to the Spitfire waiting patiently on the grass at Duxford I suddenly realized just how long it had been since I last flew it.  It had even changed colour!  My first flight in G-CCCA was way back in 2005, when it wore a scheme to represent its time flying with the Irish Air Corps as ‘IAC161’.  However, it was now painted to represent a Dutch aircraft, ‘H98’, and certainly looked a lot more ‘warlike’ in its camouflage.

I revelled in the Spitfire’s grace, elegance and power.
I revelled in the Spitfire’s grace, elegance and power. (Ben Ullings)

As usual, I studied the aircraft from a distance and immediately noted how narrow the undercarriage track looked, and also how little prop clearance there was. Even if I hadn’t already flown this aircraft, I could clearly see that great care would need to be taken any time it was moving on the ground!

Moving in close for the pre-flight I studied the huge prop and elegant spinner.  The propeller is a four-blade Rotol constant speed unit, and is turned by what is undoubtedly one of the greatest aero-engines of all time, the immortal Rolls-Royce Merlin.  This liquid-cooled supercharged V-12 has a swept volume of 27 litres, and the version fitted to this particular aircraft (a -66) produces up to 1,650 of the finest British horses at 3,000rpm and +18psi of boost.  Two fuselage tanks with a combined total of 386 litres feed the engine’s voracious thirst, and there are also two 114 litre auxiliary tanks, one in each wing.  These are located where the 20mm cannons used to be, although as the aircraft was flown for gunnery training while operated by the IAC it retained one .303 machine-gun in each outer wing bay. 

That much engine requires a lot of cooling, and while studying the radiators under the wings I could clearly see that both the undercarriage and flaps must reduce the flow of air through the radiators when down.  The undercarriage legs are immediately in front of the radiators, and the flaps directly behind.  The flaps are of the split type and cover about 40% of the trailing edge.  However, they are quite narrow chord and didn’t look as if they’d be particularly effective.  They only have two positions –up or down (90°).  They are pneumatically actuated, as are the radiator doors, brakes, supercharger ram and (when fitted) the guns.  The undercarriage (which retracts outwards into the wings) is hydraulic. 

(Key-Steve Flectcher)

The famous elliptical wing is particularly noteworthy, as – for its time – it was extremely thin, with a thickness/chord ratio of only 13% at the root, reducing to 6% at the tip.  This is considerably thinner than its contemporary, the Hawker Hurricane.

Interestingly, the Spitfire is probably the most developed fighter ever made.  The Mk.I, which entered service in 1938, had a 990hp engine and a MAUW of 2,595kg.  Ten years later, the Mk.24 had 2,035hp, and weighed up to 5,511kg!  It was also the only fighter that was in production before the Second World War started, that remained in production after that conflict had ended.  It was almost certainly the very thin wing that kept it in production for so long, as the Spit’s critical mach number is – for a piston-powered aircraft – incredibly high.

Moving towards the tail I noted that although most of the Spitfire is metal, the rudder and elevators are fabric covered.  There is a trim tab in the rudder and both elevators, while the tailwheel is fully castoring and non-retractable.  Access to the cockpit is quite good – the canopy slides back a fair way, there is a small door on the left side and the non-slip wingroot walkway is sensibly sized.

I rolled in some nose down trim and pulled the power back to +2 and 2,000rpm.
I rolled in some nose down trim and pulled the power back to +2 and 2,000rpm. (Ben Ullings)

Having slid the canopy back and slipped into the cockpit I made myself comfortable.  An unusual facet of the Spitfire’s cockpit (and I suspect many other RAF fighters of the 1940s) is that there is no floor.  Consequently, it is very important not to drop anything.  The seat and rudder pedals adjust over a good range, so once I was satisfied that I could reach everything and that the view over the nose was as good as it was going to get, I began to study the cockpit more closely.  As I remembered, it is typically British – ie a mixed-up medley of mostly black-faced dials in a black-painted panel, along with some guarded buttons and a few warning lights seemingly scattered at random.  Indeed, there are some aspects (such as having the undercarriage selector on the right, or installing the rudder trim wheel in the vertical plane) that, if this were a prototype, I would deem distinctly unsatisfactory! 

The engine is a Rolls-Royce Merlin 66, which produces up to 1,650hp at 3,000rpm and +18psi of boost.
The engine is a Rolls-Royce Merlin 66, which produces up to 1,650hp at 3,000rpm and +18psi of boost. (Key-Steve Fletcher)

In fairness, upon examining the panel more closely it became apparent that the basic ‘six pack’ follows the traditional RAF arrangement and is located directly in front of the pilot.  The engine instruments are also logically laid out and reasonably well sited in a sub panel to the right of the flight instruments.  Engine power is shown by a colour-coded boost gauge and one of those terrible two-pointer tachometers.  Below the boost gauge are the yellow painted oil temperature and pressure instruments, and the coolant temperature and fuel gauges.  To the left of the flight instruments are the oxygen system controls and quantity gauge, the undercarriage position lights and a modern transponder.  Below this is the master switch, elevator trim indicator and brake triple pressure gauge.  This has three pointers, one for the two storage cylinders and one for each wheel brake. 

The throttle quadrant is mounted quite high on the left cockpit sidewall and consists of a large throttle handle, small prop lever and friction control.  The flap lever is slightly further aft, while the large hand wheel for the elevator trimmer is located immediately below the throttle quadrant.  It works logically, and has a co-located position indicator.  Behind it and slightly lower is a smaller hand wheel for the rudder trimmer.  It works illogically, as it is mounted vertically (most rudder trims are mounted horizontally), and does not have a position indicator.  On the opposite side of the cockpit are the undercarriage control lever and the main fuel cock.

The tall control column features the classic British spade grip, which incorporates a single lever for the wheel brakes and a large button for the cannons and machine-guns.  Two particularly peculiar aspects of the primary controls are that the control column articulates just below the spade grip and that the rudder pedals slide fore-and-aft.  They can be adjusted via the star wheels built into the tubes that the pedals are mounted on.

The engine is a Rolls-Royce Merlin 66, which produces up to 1,650hp at 3,000rpm and +18psi of boost.
The engine is a Rolls-Royce Merlin 66, which produces up to 1,650hp at 3,000rpm and +18psi of boost. (Key-Steve Fletcher)

I was now joined by Dave ‘Rats’ Ratcliffe, who proceeded to brief me on the cockpit layout in detail.  ‘Rats’ explained that starting the Spitfire was akin to being a ‘one-armed paper-hanger’ as quite a few controls had to be operated more-or-less simultaneously.  He then did something that really got my attention.  Moving the throttle slightly he said, “OK Dave, you move the throttle to here, you’ve got about a hundred horses.  Now,” he continued, as he moved the throttle about a centimetre, “you’ve got two hundred, and here,” he moved it another centimetre “three hundred.  Any questions?”  I shook my head – he’d certainly made his point!  ‘Rats’ patiently continued the briefing by explaining why the door catch has two positions (the door forms part of the canopy rail, so the ‘half-catch’ position prevents the canopy sliding forward and jamming should you force-land).

Note the narrow track undercarriage, and also how little prop clearance there is.
Note the narrow track undercarriage, and also how little prop clearance there is. (Key-Steve Flectcher)

John arrived, and climbed quickly into the rear cockpit.  I’m in the very privileged position of being paid to fly lots of different aircraft, but I don’t mind admitting I was pretty excited (later that evening, photographer Fletch remarked that he’d never seen me looking so ‘keyed up’ – and we’ve done a lot of exciting flying together!) 

As I’d learnt from my previous Spitfire lesson, the coolant heats up very quickly, so checks like the ‘full and free’ for the controls and setting the trims are done long before starting the engine.  Elevator trim was set just slightly forward of neutral, while the rudder trim was left neutral.  Although the original Pilot’s Notes recommend using right rudder trim, John doesn’t.  He explained that as soon as you’re airborne you have to retrim almost immediately, and furthermore the pedal loads are not excessive anyway.  The next items on the pre-start checklist were to set the parking brake, check that the undercarriage lever was ‘down’ then turn on the master switch and ensure the green ‘down’ lamp was lit.  Then I pre-oiled the engine for three minutes with the electric pump. 

(Key-Steve Flectcher)

Once all these tasks were done I set the throttle lever so that I could just see the micro-switch for the undercarriage warning horn and turned the main fuel cock ‘on’, then pulled and held the idle/cut-off ring and turned on the main tank booster pump for 30 seconds.  Finally I shut down the pump, released the ring and unscrewed the Ki-Gas primer.  I used this to give the engine five shots and left the primer pulled out, as John recommended that another shot as the engine started was always a good idea.  

At last, I pulled the stick all the way back and over to the right with my left hand, then pressed the guarded starter and booster coil buttons.  After four blades had swung past I flicked up the left mag switch and the big Merlin fired up instantly.  Right mag on, I eased the throttle back, pushed the primer in and carefully screwed it down.  After a quick check of the oil and pneumatic pressures, I was ready to roll. 

The Spitfire was practically shaking with suppressed energy, and it almost felt as if I was riding an impossibly powerful horse.  As we set off on the long taxi to runway 06 I noticed an old man standing at the fence and staring with rapt interest at the Spitfire.  What was he looking at, I wondered.  A piece of history – or a piece of his story?  I continued along the taxiway in a series of sinuous S-turns, while carefully monitoring the coolant temperature and brake triple pressure gauges. 

Access to the cockpit is quite good – the canopy slides back a fair way, there is a small door on the left side and the non-slip wingroot walkway is sensibly sized.
Access to the cockpit is quite good – the canopy slides back a fair way, there is a small door on the left side and the non-slip wingroot walkway is sensibly sized. (Key-Steve Flectcher)

Taxiing a Spitfire is not easy.  The big nose blocks out a considerable amount of whatever’s immediately in front, and this – combined with a castoring tailwheel and hand-operated pneumatic brakes – make it quite a challenging exercise.  Obviously, for a number of reasons you can’t go too fast, but at the same time you can’t go too slow, because the coolant temperature is constantly rising.  Luckily for me it was a cool day.  It must be a nightmare when it’s hot, particularly if you’ve got a long taxi.

At the run-up point I swung the aircraft into wind, centred the rudder pedals and squeezed the brake lever.  During the briefing John had emphasised that you never set the parking brake for the run-up, as should the tail start to lift (and it will at the slightest opportunity) you must allow the aircraft to roll forward.  As the oil temperature was already over 40°C I ensured the stick was fully back and slowly opened the throttle to 1,850rpm in order to check the mags and exercise the prop, then slowly pulled the throttle right back to idle and noted the rpm.  This is very important.  The Spitfire is not over-endowed in the flap department, and if the tick-over is too high it will float a considerable distance. 

John then showed me a very useful trick.  He directed me to roll slowly forwards about half the aircraft’s length, then turn 45°.  By looking back over my shoulder I could see if any oil or coolant had leaked onto the ground during the run-up. 

The flight instruments are located directly in front of the pilot, with the engine instruments in a sub panel to the right.  To the left of the flight instruments are the oxygen system controls and quantity gauge, the undercarriage position lights and a modern transponder.  Below this is the master switch, elevator trim indicator and brake triple pressure gauge.  Note that G-CCA has a GPS instead of a gunsight.
The flight instruments are located directly in front of the pilot, with the engine instruments in a sub panel to the right. To the left of the flight instruments are the oxygen system controls and quantity gauge, the undercarriage position lights and a modern transponder. Below this is the master switch, elevator trim indicator and brake triple pressure gauge. Note that G-CCA has a GPS instead of a gunsight. (Key-Steve Flectcher)
Above and below: The throttle quadrant is mounted quite high on the left cockpit sidewall.  The flap lever is slightly further aft, while the large hand wheel for the elevator trimmer is located immediately below the throttle quadrant. The undercarriage control lever and main fuel cock are on the right side of the cockpit.
Above and below: The throttle quadrant is mounted quite high on the left cockpit sidewall. The flap lever is slightly further aft, while the large hand wheel for the elevator trimmer is located immediately below the throttle quadrant. The undercarriage control lever and main fuel cock are on the right side of the cockpit. (Key-Steve Flectcher)
(Key-Steve Flectcher)

All checks complete, I trundled out onto the grass runway, lined up and took a deep breath.  I’d already noted that the wind was from the left, which would tend to exacerbate the Spitfire’s propensity to swing.  Brakes off, I slowly opened the throttle while feeding in right rudder.  I’m so paranoid about not letting the Spitfire swing that I focussed all my attention outside.  Consequently, I used more power than I meant to (+12lb/sq in boost, instead of only +7) and we were off the ground very quickly. 

I felt the throttle move back under my hand as John accurately set the power while commenting dryly “plus seven is plenty Dave!”  I’m annoyed I’ve used too much power, but pleased that I haven’t swung.  As the last of the runway disappeared from view I squeezed the brakes, put my left hand on the stick and my right on the undercarriage lever.  There’s a slight wobble as I changed hands, but it’s not too bad.  I pressed down on the lever for four seconds (to pressurise the hydraulic system), moved it inwards (out of its gate) and forwards in one movement, then held it in place while waiting for the red ‘wheels up’ light. 

It is imperative that the undercarriage retracts completely, as the legs are immediately in front of the radiators.  Without an adequate flow of air through the radiators and oil cooler the engine will rapidly overheat.  I could actually feel the wheels thump home in the wells through my seat, and this was confirmed by the red light.  Changing hands again, I rolled in some nose down trim and pulled the power back to +2 and 2,000rpm.  Phew!  So far – so good! 

I then eased the prop back to 1,850rpm, left the boost at +2 and took a couple of moments to savour where I was sitting – the front seat of a Spitfire!  I gazed out over the impossibly long nose and then looked sideways at the iconic elliptical wing.  Just for a couple of minutes, I completely forgot about John sitting just behind me and revelled in the Spitfire’s grace, elegance and power.  Then, it was time to get back to work. 

G-CCCA is currently painted to represent a Dutch aircraft, ‘H98’, and certainly looked very ‘warlike’ in its camouflage.
G-CCCA is currently painted to represent a Dutch aircraft, ‘H98’, and certainly looked very ‘warlike’ in its camouflage. (Pete West)

After a couple of graceful, sweeping turns I tried to work out where we were.  However, it was a rather grey, claggy day – and at 190kts we’d already gone a long way.  Consequently, I was ‘temporarily unsure of our position’.  John helpfully gave me a heading to steer, and told me to slow down prior to extending the undercarriage and flaps. 

Despite pulling the power back to -2 the Spitfire was reluctant to decelerate, so I initiated a gentle climb to shed some speed.  I’ve memorised the limiting speeds, and as the needle of the ASI dipped below 140kts I changed hands, pressed the undercarriage lever forwards (to get the legs off the uplocks) and pulled it all the way back in one movement.  As the legs locked down I rolled in some nose-up trim, waited for the speed to reduce below105kts, then lowered the flaps.  I felt the deceleration as they extended into the airstream, and the nose also pitched down, requiring more ‘up’ trim. 

At 95kts I eased the Spit into a smooth right turn to remind myself how it would feel on the approach.  It felt like the lateral control was beginning to degrade slightly as the speed reduced, although there was still lots of lift in those beautiful wings.  However, the elevator remained very effective.  Satisfied that I’d got the feel of it, John directed me to increase rpm to 2,000 and the boost to +2, retract the flaps and undercarriage, and return to Duxford. 

(Ben Ullings)

I entered the circuit at Duxford via a ‘run and break’.  However, this wasn’t for show.  As I’d already learnt, because the aircraft is a relatively ‘clean’ design it takes time to slow it down.  The best way to bleed energy is to pull up and round, putting on some ‘g’ in the process. 

I was careful to avoid Duxford village via a small dogleg as I turned downwind, then moved quickly into position so that I was at 800ft agl with the wingtip just level with the runway.  I made a quick check of the speed midfield, then lowered the undercarriage, retrimmed and opened the oil cooler and radiator doors.  After another speed check, it was time for ‘flaps down’, more nose-up trim and then bank back towards the runway.  The flaps are pneumatic, as are the brakes, so I glanced at the brake triple pressure gauge and checked we had adequate pressure.

As I came round the corner I thought “I’m a bit low” and asked if I should add power.  “No, it’s OK – keep it coming,” John replied.  I pushed the prop up and slowly started rolling the wings level on very short final.  “Nice,” said John, “OK, power off!” 

I slowly closed the throttle and ever so gently eased the stick back.  The nose reared up, blocking my view forwards.  Using my peripheral vision, I tried to hold the attitude I’d burned into my memory – I didn’t want to touch down tail first.  For long seconds the Spitfire floated tantalisingly close to the ground, and then settled gently onto the grass.  We were down and rolling out nice and straight.  I could feel that the elevator was still very effective, and slowly eased it back as the speed dropped.  On many taildraggers, you want to get the stick right back straightaway, but the Spit has big wings and a powerful elevator.  I could sense that it still wanted to fly.

I revelled in the Spitfire’s grace, elegance and power.
I revelled in the Spitfire’s grace, elegance and power. (Ben Ullings)

As briefed, I ignored the brakes and just used small jabs of rudder to keep us straight.  The grass would slow us down.  As the speed dropped away I tried a couple of very tentative squeezes of brake, and we slowed to a stop.  I suddenly remembered to start breathing again, and raised the flaps.  It was a good landing, and I know it! 

Above and below: Many of the systems are pneumatically actuated, including the flaps, radiator doors and brakes. An engine-driven compressor fills the two air storage cylinders.
Above and below: Many of the systems are pneumatically actuated, including the flaps, radiator doors and brakes. An engine-driven compressor fills the two air storage cylinders. (Key-Steve Flectcher)
(Key-Steve Flectcher)

A fair chunk of tailwheel time, some excellent coaching and a bit of luck had produced a smooth three-pointer!  “Very nice,” said John.  I was well chuffed.  As I taxied carefully back on the grass he added, “this time, I want to see the power come in smoothly.  Let’s see a nice steady 1, 2, 3, 4, 5, 6, 7 on the boost gauge – not a jerky 1…3…5…8…12!”

We both laughed, but I resolved to ‘do it right’ next time– and I did.  The take-off was much better this time.  The power was applied smoothly to +7lbs sq in boost, and I barely wobbled when I changed hands to raise the undercarriage.  Speeds, heights and power settings were all good as I turned back downwind.  I really felt as if I was ‘in the groove’, and John was saying nothing. 

Moving towards the tail I noted that although most of the Spitfire is metal, the rudder and elevators are fabric covered.  There is a trim tab in the rudder and both elevators.
Moving towards the tail I noted that although most of the Spitfire is metal, the rudder and elevators are fabric covered. There is a trim tab in the rudder and both elevators. (Key-Steve Flectcher)

“Here we go,” I thought to myself.  “This looks perfect!  OK – gear down, open the oil cooler and radiator doors, trim.  Flaps down, more trim – check the air pressure, round we go.  I’m just ever so slightly slow,” I thought, “so just a tad more power…there.   The angle looks good, the speed is dropping back towards 90mph, start rolling the wings level and push the…”  “Prop please Dave,” says John.  Bugger!  He beat me to it.  If only I’d been talking out loud!  I slowly drew off the power and felt the throttle move ever so slightly under my hand as John ensured that it was on the stop.  Even a small amount of residual thrust would greatly prolong the float.  I was holding off and trying to keep it airborne – then the wheels touched, but we still had flying speed.  We then hit a bump which skipped us back into air, and suddenly we were flying again. 

(Key-Steve Fletcher)

During the briefing John had said that this was a distinct possibility, and that under no circumstances should I try and ‘chase’ the attitude, as a PIO is almost inevitable due to the sensitive elevator.  Instead, I held the stick still, kept straight with rudder and waited.  Two more small skips and we were down and rolling out.  I’d done it!

Back at the hangar I pulled out the idle/cut-off ring and the great propeller swiftly slowed to a stop.  Even before I’d got the switches off John has unstrapped and was climbing out, but I was in no rush.  Instead, I sat in the cockpit and tried to remember everything.  The feel of the spade grip in my hand, the awesome cowling stretching out in front of me and the heady aroma of oil, Avgas and a hot V-12.  Reluctantly I undid my harness and took one last look around the cockpit.  What an incredible experience!  I felt elated, but almost sad as well. How am I ever going to top this?

 

SUPERMARINE SPITFIRE Tr.9

DIMENSIONS

LENGTH                                  9.55m                    31ft 4in

HEIGHT                                   3.86m                    12ft 8in

WING SPAN                         11.22m                  36ft 10in

WING AREA                         22.47m2                 242 sq ft

 

WEIGHTS AND LOADINGS

EMPTY WEIGHT                   2,631kg                 5,800lb

MAX AUW                             3,401kg                 7,489lb

USEFUL LOAD                       770kg                     1,689lb

WING LOADING                  151.3kg/m2           30.9lb/sq ft

POWER LOADING               2.76kg/kW            4.53lb/hp

FUEL CAPACITY                   614lit                      135 Imp gal

 

PERFORMANCE

VNE                                         385kts                    713km/h

CRUISE                                   205kts                    380km/h

STALL                                      65kts                      120km/h

CLIMB RATE                          4,540ft/min          23m/sec

SERVICE CEILING                40,600ft                12,383m

 

ENGINE

Rolls-Royce Merlin 66 liquid-cooled supercharged V-12, producing 1,650hp (1,230kW) at 3,000rpm.

 

PROPELLER

Rotol four-blade constant speed.

 

MANUFACTURER

Vickers Supermarine.

 

OPERATOR

The Aircraft Restoration Company,

Duxford Airfield, Cambs.

Tel: 01223 835313  

Fax: 01223 837290

Email: info@arc-duxford.co.uk  

Web: www.arc-duxford.co.uk

If you liked this article, the full magazine is available from Key Publishing Shop

 

 

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