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Flight Test: World War I Bristol F2b Fighter

PUBLISHED: 16:48 14 December 2016 | UPDATED: 16:48 14 December 2016

Bristol F2b Fighter

Bristol F2b Fighter

Archant

At the controls of the type that in WWI rewrote the rules — the original multi-role combat aircraft

Delightfully evocative of a different eraDelightfully evocative of a different era

Words: Andy Sephton; Photos: Steven Jefferson and Peter R March

I first learned of the World War I Bristol F2b when a colleague in my local Air Training Corps’ aeromodelling group brought his model to one of our meetings. I was so taken by the design that I immediately sent off for a set of plans and built one of my own. Little did I know that some thirty years later, I’d be flying the full-size machine.

Even now, she still looks right as a flying machine. The long nose, tail and wings all balance and complement each other. The tailplane is well proportioned and the fin/rudder, albeit a little small, look right at the back end.

The F2b is a pleasant enough aircraft to fly and she has few vices but, like all aircraft of the period, she has her own characteristics, which make her what she is.

At the (rather blunt) ‘sharp end’ is a Rolls-Royce Falcon III 275hp V-12 liquid cooled engine, driving a fixed pitch two-bladed wooden propeller. A radiator, with pilot-controlled shutter, is fitted in front of the engine to facilitate cooling.

The F2b in its previous inter-war colour scheme (grey and silver), carrying a ‘gunner’ as was then allowedThe F2b in its previous inter-war colour scheme (grey and silver), carrying a ‘gunner’ as was then allowed

Moving clockwise around the aircraft, there’s a Rotherham mechanical air pump on the starboard wheel strut, to pressurise the air system when in the air or with the engine running on the ground. The lower wing is fitted slightly below the fuselage so, with the standard biplane gap, the upper wing is set closer to the fuselage than it would normally be. This puts the average pilot’s eyes in line with the upper wing, which allows minimum impact of the wing in the field of view from the cockpit.

Around the wing and you see it’s a long-span four-bay biplane. The damping from the large area is high, but it’s balanced partially by its rather large ailerons. However, when noting aileron movement − which is more down than up − it becomes clear there will be significant adverse yaw. This means the aircraft will yaw in the opposite direction to any roll applied with the ailerons.

Passing down the unremarkable right side of the fuselage, we reach the tailplane and a jack fitted at the trailing edge to give the pilot the facility for in-flight pitch trimming. Effectively, we have an all-moving tailplane with elevators fitted at the rear. The tailskid is well sprung and well supported – looking closely, you can see it can castor through small angles. If we try to lift the tail, we find it is heavy.

In pitch, the aircraft is light and sensitive; in roll she is sluggishIn pitch, the aircraft is light and sensitive; in roll she is sluggish

These two facts, together with a narrow track undercarriage located well forward on the fuselage, means we have a groundlooper, for sure. This is confirmed by the hoops fitted under the wings to protect the wing tips and aileron horns when the aircraft does just this. There are no brakes, and the rudder is relatively small, therefore it’s best not to try any wheeler landings (the precessional swing caused by the rotating propeller as the tail is lowered will initiate a groundloop), and always to land into wind.

In fact, these two suggestions are two of the basic ‘rules’ for flying this aeroplane. Those who ignore them do so at their cost!

Rolls-Royce Falcon III V12 engine puts out a respectable 275hpRolls-Royce Falcon III V12 engine puts out a respectable 275hp

Along the port fuselage, we pass the observer’s position and note that ballast must be carried in lieu if there is no observer present. There are adequate footholds leading up to the pilot’s cockpit, but an unwritten warning not to use the long exhaust pipe as a step must be heeded.

Note the two main ignition switches, set in the off position, on the outside of the cockpit, in view of the ground crew and well within reach of the pilot. The port wings are similar to the starboard, but as we reach the engine again, we see various drain pipes under the nose of the aircraft, some leaking fluids and some not. As long as the leaks are not excessive, the aircraft is acceptable for flight.

The Shuttleworth Collection’s Bristol Type 14 F2b Fighter D8096 was built by the Bristol Aeroplane Company at Brislington, Bristol in 1918. The ‘Brisfit’ is believed to have served with No 208 Squadron in Turkey in 1923 but was back in Britain for conversion to dual control Mk II by October 1925. It was sold to Christopher Penrose Bartholomew Ogilvie who registered it as G-AEPH on 13 November 1936, and went unconverted until 1949. It was restored by the Bristol Aeroplane Company at Filton as a Mk II and flown by Bill Pegg for the first time on 14 February 1951. A year later, it was with the Shuttleworth Collection at Old Warden and CAA records show that it officially transferred to the Shuttleworth Collection Trustees on 29 October 1981. It remains active 35 years later.

For the Rolls-Royce Falcon III V12 engineFor the Rolls-Royce Falcon III V12 engine

Time to climb in − with the cockpit behind the wing, there’s little to impede progress. As well as avoiding standing on the exhaust pipe, it’s prudent to avoid the myriad flying control wires situated along the side of the fuselage. The first action, before strapping in, is to stand on the pilot’s seat facing backwards to take a good look into the observer’s cockpit, to ensure the ballast weights are present and correct, there are no loose articles and the observer’s straps are secure.

Turning around, we’re faced with the wing centre-section with the flight compass located in the middle. The remaining cockpit instruments are located on a pretty standard WWI-pattern instrument panel lower down in the cockpit. The throttle and mixture control are on the left side, with an advance and retard lever using the same quadrant but mounted below. To the right are a trim lever to adjust the all-moving tailplane and a radiator shutter lever to control the coolant temperature.

Odd looking gap between the lower wing and fuselage is a consequence of the decision to mount the upper wing low down, in a position where it impedes the pilot’s vision to the minimum degreeOdd looking gap between the lower wing and fuselage is a consequence of the decision to mount the upper wing low down, in a position where it impedes the pilot’s vision to the minimum degree

Dominating the instrument panel is the Air Pressure Exchange, a manifold with a number of pipes entering and leaving, each with its own on/off tap. It’s worth explaining the workings of the manifold and its associated fuel and air systems as it forms a fundamental part of how to operate this aircraft.

Fuel is contained in two tanks – the rear tank is under the pilot’s seat and the front tank immediately behind the engine. The front tank could provide some gravity flow to the carburettor, but it’s not guaranteed. The rear tank cannot. The tanks are switched by a mechanical tap located low and left of the instrument panel with positions marked front, rear and off. The full name of this device is the ‘Dewrance 3-Way Cock’. Air pressure is used to force the fuel into the carburettor.

The system runs at 2.5psi and is limited by a pressure relief valve. Air pressure is generated by either a cockpit mounted pilot-operated pump, an engine driven pump and/or a Rotherham propeller pump. All three air sources are routed into the Air Pressure Exchange manifold. The other three manifold pipes lead to the pressure relief valve and the two tanks. For normal operations, all of the valves are set open, allowing air pressure to be generated by all three sources and fed to both tanks continuously.

The twin Lewis guns — a powerful sting in the tail by WWI standardsThe twin Lewis guns — a powerful sting in the tail by WWI standards

In the event of air pressure failure, the pilot should be able to isolate the fault by selective switching of the various air sources and/or outlets. It’s a relatively straightforward process, but it does require a good knowledge of the system as a wrong selection at a critical time could lead to engine failure.

Getting back to the cockpit, in addition to the standard flight instruments of the day, there’s a starter magneto and associated switch to the low right of the instrument panel and a priming fuel cock to the upper right. Starting the engine requires at least three ground crew members to assist, two to pull the propeller over compression and one to hold the tail down. The engine is primed by the ground crew and the propeller pulled through several revolutions to distribute the mixture.

F2b Fighter formates with an earlier Bristol design, the single-seat Scout (in this case, the Bremner/Wilford replica)F2b Fighter formates with an earlier Bristol design, the single-seat Scout (in this case, the Bremner/Wilford replica)

The ground crew call “Ready” when their pre-start ritual is complete. The pilot sets the throttle about half an inch open, the mixture rich, the timing fully retarded, the radiator shutters closed (assuming a cold engine), checks the fuel is set to the front tank, that air pressure is available, the trims are fully back, holds the control column fully back, sets the main magnetos on and sets the starter magneto on.

One of the ground crew takes hold of the propeller, while the second takes hold of the first ground crew’s other hand and the pair align themselves forward of the propeller arc but in line with the propeller rotation. They pilot calls out “Three, two, one, go!” at which point the ground crew pull the propeller over compression. After the propeller starts to move − and certainly not before − the pilot vigorously turns the starter magneto handle, sending a shower of sparks to the cylinders.

The engine fires and bursts into life… we hope! If not, the switches are set to off and the starting process is repeated.

With all its woodwork and Edwardian fittings — including a brass light switch — this is a pilot’s ‘office’ that merits the nameWith all its woodwork and Edwardian fittings — including a brass light switch — this is a pilot’s ‘office’ that merits the name

Once the engine is running, the pilot immediately checks the oil pressure is rising to a minimum of 20psi within thirty seconds, then sets the throttle for about 1,000rpm for warm up. The priming cock must be turned off to prevent rough running and the radiator temperature monitored to prevent a temperature runaway.

There’s a lot of lag (hysteresis) in the radiator temperature/radiator shutter position relationship, so anticipation is the order of the day. A coolant temperature of more than 60°C is required for engine run-up, but the coolant must be kept below ninety. An ideal would be around eighty degrees. The advance and retard is also set for smooth running − about one third to a half forward from fully retarded would be about right at this stage − and the starter magneto is set to off.

As soon as the engine oil and coolant have warmed, an engine run-up is made on the chocks (there are no brakes, remember). The advance and retard is set between two-thirds and fully forward, and engine power assessed. The magnetos are checked at 1,450rpm and idle speed at about 500-600rpm. Taxying can be carried out without wing walkers but, given the vagaries of steering with a castoring tailskid, it’s prudent to seek their aid for the trip between dispersal and the runway holding point. The rear tank can be checked on taxi, but it’s sensible to use the front tank for takeoff, display and any other form of low flying.

Pre-takeoff checks are quickly carried out: trim is set to neutral; throttle friction set; mixture fully rich; radiators open; timing fully advanced; fuel on − front tank; air pressure satisfactory; temperatures and pressures in the normal range; harness secure and controls full, free and correct movement. When lined up, the wing walkers can be waved off with a ‘thank you’ thumbs up, then it’s just a case of waiting for a green light from the Aldis lamp in the Tower.

The engine is opened up slowly and the aircraft rumbles forward. A slight swing to the left can be easily corrected with rudder as there is adequate slipstream from the large propeller. Acceleration is smooth, progressive and quite powerful for such a large aircraft. In a very short time, the controls come alive and we’re airborne.

Details include a modern stand-by compass (set in grey panel) supplementing the original mounted in the top wing, inclinometerDetails include a modern stand-by compass (set in grey panel) supplementing the original mounted in the top wing, inclinometer

In pitch the aircraft is light and sensitive, in roll she is sluggish but the aileron force is light. The adverse yaw postulated during the walk round is certainly there. She wanders in yaw as well, but the rudder is effective and light. Although large, the airframe bounces in the light summer air. There’s a lot of lift from the large wings, but there’s also a lot of drag and a lot of inertia.

Notwithstanding, the aircraft is pleasant to fly and delightfully responsive in pitch. There’s power to spare, which may come in useful if we’re ever in a tight spot. Climbing at 60mph, I reduce power slightly to maintain a maximum continuous rpm of 2,000. In the cruise, we can maintain about 85mph at 1,950rpm, with the aircraft nicely trimmed in pitch.

The complicated manifold and tap array required to distribute air pressure to the two-tank fuel system from no fewer than three alternative sourcesThe complicated manifold and tap array required to distribute air pressure to the two-tank fuel system from no fewer than three alternative sources

The radiator shutters can now be closed slightly to maintain around eighty degrees Celsius on the gauge. The advance and retard can be tried, but smooth running normally equates to fully advanced. It’s rare to get more than about ten minutes’ flying time in any particular type on a flying day, and as that’s during a display, there is little time spare just to enjoy the aircraft.

So transit flights are one of the most sought after flying tasks for the Collection pilots. There’s time to look around and take in the aircraft − noise, smell and feel. I always felt I formed a stronger bond with whatever I was flying when detailed for such a trip. I’ve had a number of memorable flights in the F2b, but one of the most enjoyable was a transit flight between Old Warden and Duxford for a display.

The Collection’s Gladiator was detailed for the same display. The Gladiator pilot, the then Aviation Trustee, arrived in the Engineer’s Office sometime after me, so I was well ahead of him in timing and watched from above as he started his engine while I was setting heading for Duxford. We hadn’t pre-briefed anything, but as he was an ex-RAF fighter pilot, it was pretty obvious what was going to happen sometime during the transit. His aircraft could maintain 100mph more than mine in the cruise.

To run her up safely, you need at least one ground crew member leaning on the tailTo run her up safely, you need at least one ground crew member leaning on the tail

So, as I settled in the cruise to Duxford, monitoring the coolant temperature and making appropriate adjustments to the radiator position, monitoring the engine gauges and air pressure, and generally enjoying myself, I kept a wary eye open for a Gladiator somewhere in my six o’clock. Sure enough, as I was passing Bassingbourn, I saw the Gladiator low down in my deep 6.30 (behind and slightly to the left) about two miles away. I waited and watched.

It stalked me from below, slowly gaining on me, gradually getting bigger, until at about 300 metres range, I heaved the F2b over to the left and pulled. It didn’t need much G as I was lightly loaded and slow flying. Within one 360 degree turn, I was on the Gladiator’s tail, and the tables had been turned! He opened up and sped away − it was the only thing he could do. Honours were even in the end, neither of us got into a position to shoot the other one down.

A two-man starting team is essential — three bods just makes it a bit less of a strain!A two-man starting team is essential — three bods just makes it a bit less of a strain!

On another occasion, I was tasked to carry out a centre of gravity (C of G) expansion programme on the aircraft. For some reason, the C of G limits on the aircraft’s Permit to Fly were very tight and didn’t give us the flexibility required to operate the aircraft with all of our pilots or with the occasional engineer in the rear cockpit. New limits were decided empirically and tested over three flights.

Essentially, as the C of G is moved aft, an aircraft gets more sensitive in pitch to the point where it may be unstable. As the C of G is moved forward, there might not be enough up elevator to enable a round-out for landing or, at the limit, there may not even be enough to take off. The test programme looked at longitudinal stability, stalling and landing handling in the three different configurations tested.

In the event, there was little difference noted on all three flights, so the new limits were accepted and added to the Permit. The stall on the aircraft was always benign with little to no wing drop. There was adequate warning, albeit with nose high rather than buffet indications, and little to no nose drop. The minimum speed noted during most stalls was around 45mph.

Like all aircraft of the period, she has her own characteristics, which make her what she isLike all aircraft of the period, she has her own characteristics, which make her what she is

For landing, the radiator shutters are set closed on the approach to maintain temperature, and the aircraft speed is controlled at 60mph. The field of view forward is good, which makes positioning for a landing a doddle. Final checks include checking pilot’s harness secure, fuel on the front tank, timing fully advanced and radiator shutter closed. Trim should also be set fully aft to enable full up control should it be needed.

The aircraft sits down rather nicely in the three-point attitude, the ease of a good landing nicely lulling the unsuspecting pilot into a false sense of security. Shortly after touchdown, the aircraft heads off in one direction or the other.

Two of the supreme British warplanes of WWI, the multi-role F2b and the SE5a scout (fighter, in modern parlance)Two of the supreme British warplanes of WWI, the multi-role F2b and the SE5a scout (fighter, in modern parlance)

The pilot has to be quick on the rudder in both directions and, if necessary, quick on the power too. If the landing was made out of wind, then the aircraft will certainly swing in that direction. If a wheeler was attempted, then a groundloop to the right will nearly always result due to the precessional swing caused by the propeller as the tail is lowered.

All that notwithstanding, the aircraft quickly comes to rest, wing walkers arrive to help steer it back on to the chocks and the pilot can think about relaxing. The radiator shutters are opened after landing to prevent overheating and it’s also worth retarding the timing to reduce the rpm to give the wing walkers a chance.

Far too many pilots run their helpers off their feet by taxying too fast… and then they wonder why they can’t get any wing walkers when they really need them. Such is life!

As with most Shuttleworth aircraft, the engine is run for three to four minutes on the chocks to temperature stabilise it before shutdown. It’s then just a case of depleting the fuel tank air pressure, checking the fuel is selected to off and making sure all the switches are off, including the starting magneto. The silence after the engine has stopped is captivating. I love the gentle ticking that comes from the engine as it cools down, it’s delightfully evocative of a different era. Now, where did I put those model aircraft plans?

______________________

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