Dissecting a Heinkel

When the British brought down a Heinkel He-111 bomber practically as good as new in Scotland last year, they started right in to dissect it. Some of the results are beginning to come to light now, and while the details of its bullet-proof gas tanks have got most of the publicity, the dope on the direct fuel injection system used on its Junkers Jumo 211A engines was probably the most important.

These engines, rated at 1,050 hp at 2,300 crankshaft rpm at 14,000 feet, are liquid cooled inverted V-twelves equipped with two speed superchargers. The centrifugal supercharger is mounted to one side at the rear end with its axis at right angles to the crankshaft, and is driven at either 7.853 or 11.375 times crankshaft speed by two sets of gear trains. For high speed the pilot engages a disc clutch on the high ratio drive gear, while the low ratio drive gear, which is connected to the drive shaft through an overrunning clutch, free wheels.

The throttle is located in the air intake pipe just after the supercharger, and has an automatic control operated by the boost pressure in the intake to keep it from being opened too far by the pilot's throttle control, doing away with the possibility of some ambitious boy's burning up the engine by opening it out at too high manifold pressures. The air enters the cylinder through two intake valves in the head, between which the fuel injector is placed in the side of the head. The two spark plugs are also in the side of the head, one at about 45° and the other at about 135° from the injector. The single exhaust valve is in the head on the side opposite the injector.

The chief point of interest is the fuel injection pump, and particularly the complicated automatic mixture control that proportions the amount of fuel injected to the weight of air taken in. All the pilot worries about is his throttle and blower ratio control; the automatic control on the fuel pump does all the rest. The injection pump is a twelve-cylinder plunger pump with two opposed banks of six cylinders. The whole works is mounted in the V of the engine, the plungers being worked one direction by a camshaft running half crankshaft speed and being returned by springs. The fuel is injected into the cylinders in a fan shaped spray on the suction stroke, always starting at the same point in the stroke but being cut off according to the amount of fuel being injected.

Each pump plunger has a spiral groove along the side at its head end working across a bypass port in the pump cylinder. With a constant stroke the plunger will deliver a variable volume of fuel into the injection line through check valves according to how it is turned in its cylinder. The rest of the fuel displaced by the plunger goes down through the groove, out the bypass port, and back to the suction side of the pump. The six plungers on each side of the pump are rotated together by a rack across them.

Preparing for the Junkers Ju88

Now that the British are pretty well used to being visited by assorted Heinkels and Dorniers, the Junkers Ju88 is being mightily talked up as something to get ready for. This is being done both by those in the government who don't want the public to get the idea that they are too safe, and by those in the trade who would like to see their own country turning out more bombers like it and plenty of fighters capable of catching it without trouble. So far it hasn't put in an appearance anywhere, but from the records it set last summer it must be quite an airplane. Just how the record ship compared with production models is a deep German secret, but at any rate it turned in a speed with 4,400 lbs load of 321 mph over 625 miles, and 311 mph over 1,250 miles.

It looks nice too; it's a low wing all metal job of fairly conventional appearance except for the trick tail, which has a big fin and rudder in the middle and two smaller fins at the ends of the stabilizer. Another novelty is the type of radiator and cowling for the engines. It has two Jumo 211 engines, and these are provided with a doughnut-shaped radiator with the engine in the hole in the middle, the whole works being covered by a round nacelle and ring cowling like that used with a radial engine.

The gross weight of this ship is supposed to run around 17,000 lbs, which would put its wing loading at around 33 lbs. Like other recent German bombers, the crew of three are carried well forward, all together, instead of being strung out along the fuselage, and not much armament is provided. There's a gun above and one below to the rear, both in the small transparent bullseye type of mounts that the Germans are going in for instead of turrets.

Those Messerschmitt Destroyers

Another German ship that's come in for plenty of publicity on both sides lately is the Messerschmitt Me-110. Just what to call it is a problem; the Germans have given this class the name of "destroyer". Essentially it's a high performance, heavily armed multipurpose type. In Poland it was used on attack missions, is being brought out now and again in the West as a defensive fighter against British bombers, and it could probably be used as an escort fighter over medium ranges in a pinch.

It's a fair-sized airplane, and going by the dimensions its gross weight has been estimated at around 15,000 lbs, which would figure a wing loading in the neighborhood of 36 lbs. Most of the Me-110s are supposed to have DB601 motors, which are rated at 1150 hp at 16,000 feet and have such features as direct injection and hydraulically driven, automatically controlled superchargers. Others may be coming out with Junkers Jumo 211 engines. In either case, two of them put out plenty of horses for a ship of this size, and the top speed is up in the 370 mph range.

It is a nice clean-looking, low-wing ship; the Germans don't seem to have taken as much to the midwing arrangement as other countries have. The general effect is somewhat spoiled because the Germans have evidently not made any effort to retract or fair in the tail wheel, which hangs out in an aerodynamically shameful fashion. It's all metal, of course, and has the usual Messerschmitt single-spar wing. To help the boys get it down, automatic slots and slotted flaps have been provided. The tail has twin fins and rudders.

Gas capacity is around 400 gallons, which with all that power doesn't give it any super range. It could make a round trip bombing escort flight to Britain by easing back the throttles, but it wouldn't be able to spare gas for very much fighting along the way. These ships seem to be coming out with a variety of armament, but outside of a movable machine gun or two to the rear on top, the main punch is fixed and fires forward.

KLM and the War

What the war did to KLM's traffic figures is shown by a report comparing the prewar eight months of 1939 with the last four wartime ones. In the first eight months about 88,000 passengers were carried, but the number dropped off to around 10,000 for the last four. On the East Indies route the Dutch were patting themselves on the back about their traffic increase to 5,000 passengers up to Sept 1 compared with 3,500 for the same period in 1938, but from then on to the end of the year only 1,200 more were hauled. There's talk that the fare on the East Indies route, which was boosted considerably at the beginning of the war to help cover the big jump in operating costs, may be cut to get traffic figures up again.

In Europe KLM has sent a survey ship through from Amsterdam to Portugal via Britain and Spain. On its schedule are flights to the Cape Verde islands, the next stop on the trans-Atlantic route to Paramaribo, and also to Naples, still the western terminal for the East Indies line. The Dutch aren't saying whether they're working toward Netherland-Britain-Portugal service, but this would permit tying up both their trans-Atlantic and East Indies lines to Amsterdam by air instead of having them end off short. The chances are that the British would allow the line — subject to several carloads of restrictions — as they could use a service down that way. At present they themselves are pretty well held back from starting the route, what with having their hands full elsewhere and not being on too good terms with Mr Franco.

This column was originally published in the March, 1940, issue of Aviation magazine, vol 39, no 3, pp 84, 86.
The original column includes 3 photos.
One photo credited to British Press Combine; 2 photos not credited.

Photos: