The most-produced fighter ever, and the yardstick every Allied fighter was measured against.
1940·Bf 109 E-4·~560 km/h at 4,500 m·33,984·DB 601Aa inverted V-12, 1,175 PS·660 km on 400 L·~10,500 m
1· THE STORY
The fighter everything was measured against
The Bf 109 was the smallest airframe that could be wrapped around the biggest engine available, and Germany built some 34,000 of them, more than any other fighter in history. Over England in 1940 it was at least the equal of the Spitfire: it climbed better, dived better, and its engine kept running when the Spitfire’s cut out. What it did not have was fuel. Flying from France, a 109 had perhaps ten minutes of combat over London before it had to turn for home. That short endurance was one of its biggest handicaps in a battle that radar, the control rooms, tactics, production and losses also decided.
~560 km/h at 4,500 mTop speed (E-4)33,984Built (all versions)
2· WHY IT MATTERED
Injection beat the carburettor
Push the nose down hard and the fuel in a float carburettor floats to the top of its chamber: the engine starves, then floods. Merlin-engined Spitfires and Hurricanes lost power for a second or two whenever a 109 bunted into a dive, because the DB 601 had direct fuel injection, a pump metering fuel into each cylinder, and did not care which way was up. The RAF’s first fix, in 1941, was a brass restrictor designed by Beatrice Shilling at Farnborough; the real cure, a pressure carburettor, took until 1943.
From the F model a cannon fired through the hollow propeller shaft — the Motorkanone — so its shells came out exactly along the line the pilot was looking, with no need to set the wing guns to converge at some chosen range. Later versions added a 30 mm cannon there that could bring down a bomber with a few hits.
4· WHY IT MATTERED
Range, the handicap
Four hundred litres of fuel gave the 109 E about 660 km of range and a combat radius of roughly 300 km. From the Pas-de-Calais that meant minutes over the target and a Channel to recross with the fuel light on; escorting bombers at their speed made it worse. The 300-litre drop tank arrived with the E-7 from August 1940, too late and on too few aircraft to change the summer. Performance was never the 109’s problem. Fuel was.
5· THE ENGINE
Daimler-Benz: the injected inverted V-12
The DB 601 hung its cylinders upside down like the Jumo, and injected fuel directly at 1940 pressures that were state of the art. Its supercharger was driven through a hydraulic clutch that a barometer adjusted continuously with altitude, so instead of the step of a two-speed gearbox the blower sped up smoothly as the air thinned. The DB 605 of the G series, from 1942, grew to 35.7 litres and 1,475 PS, and from 1944 many G models could spray water and methanol into the intake to run 1,800 PS for a few minutes: the water cooled the charge and held off knocking, so the engine could take boost that would otherwise have wrecked it.
Bf 109 E-4 (1940): DB 601Aa · inverted V-12 · 33.9 L · Bosch direct injection · clutch-driven supercharger · 1,175 PS · Bf 109 G-6 (1943): DB 605A, 35.7 L, 1,475 PS; with MW 50 (1944) 1,800 PS
Two machine guns and two cannon; later, a cannon in the nose
The 1940 Emil fired two rifle-calibre machine guns over the engine and two 20 mm cannon in the wings: about 2.1 kg of metal a second, but the cannon drums held only sixty rounds — seven seconds of firing — after which it was back to the machine guns. The 1943 Gustav moved the heavy guns to the nose: two 13 mm machine guns and one 20 mm cannon through the spinner, the same weight of fire with far more rounds behind it. Gondola cannon under the wings doubled it again for bomber hunting, at a cost in handling that fighter pilots hated.
7· TRY IT
Minutes over London: what 400 litres buys
Four hundred litres inside, a climb, the Channel crossing each way and a reserve you choose: what is left is minutes at combat power over London, the number that shaped the Battle of Britain more than any performance figure. Add the 300-litre drop tank the Emil did not have that summer and watch it change. A planning sum, not a sortie.
Readout
Minutes over London6 min
Fuel on board288 kg
Radius with that fight161 km
The planning arithmetic, in round numbers: rich mixture for the climb and the fight, the E-4’s 1,175 PS and cruise consumption, L/D 12.5, still air. Real sorties varied with routing, the bombers’ speed and the weather; the answer is the order of magnitude, and it is small.
8· THE LAB
Power, guns and range: the same three models for all ten
Power against altitude from the type of supercharger, weight of fire against the other nine, and Breguet range with the armour and drop-tank trades. Simplified models, each scaled to this aircraft’s published figures, so the shapes are honest and the third decimal is not.
At 4,500 m: 1,108 hp in total, true airspeed 560 km/h.
Readout
Power1,108 hp
Per engine1,108 hp
True airspeed560 km/h
Service ceiling10,500 m
A simplified model calibrated to the published rating and top speed — the shape of the curve is the point, not the third decimal.
Messerschmitt Bf 109, 2 of 10
Deep dive · Injection against the carburettor· opened from Messerschmitt Bf 109
Push the nose down and a float carburettor starves — the 109 did not care which way was up.
direct injection, 1937·SU float carburettor·March 1941·1943
01The idea
A float chamber under negative g: the fuel floats, the jet runs dry, the engine coughs
A carburettor mixes fuel and air by letting the air rush past a jet and suck fuel out of a small chamber kept topped up by a float valve, like a cistern. Turn the whole thing upside down, or push the nose over hard enough that everything inside goes momentarily weightless, and the fuel floats away from the jet: the engine leans out and cuts. A moment later the float valve, now the wrong way up, lets fuel flood in. The Merlin of 1940 had exactly this carburettor. The DB 601 pumped fuel straight into its cylinders and never noticed.
02Why it matters
Why a bunt beat a Spitfire
A 109 pilot with a Spitfire on his tail could push the stick forward and dive. The Spitfire pilot following him lost his engine for a second or two, fell behind, and often lost the fight. Spitfire pilots learned to half-roll and pull into the dive instead, which kept the g positive but cost time.
03Why it matters
Miss Shilling’s orifice
In March 1941 Beatrice Shilling, an engineer at the Royal Aircraft Establishment, fitted a small brass restrictor in the fuel line that limited the flow to the engine’s maximum-power rate. It stopped the flooding, though not the initial lean cut, and pilots gave it a name that has stuck. The real cure was the Bendix-Stromberg pressure carburettor in 1943, which injected fuel into the supercharger under pressure and had no float at all.
04Why it matters
Why the Merlin kept its carburettor
A carburettor cools the intake charge as the fuel evaporates in it, which was worth some power in a supercharged engine, and Rolls-Royce judged that worth more than the negative-g cut. The Germans judged the other way. Both engines won battles.
05Try it
Float chamber under g
A float chamber with the g slider: watch the fuel level against the jet as the aircraft bunts.
Readout
Fuel in the chamberon the floor
Jetfed
Engineruns
Where the fuel sits, not the mixture: the real cut came in two stages — first a rich cut as the float dropped, then starvation. The RAF’s stop-gap was a washer in the fuel line; the DB 601 never had the problem.