The clearance needed between two props next to each other leads to the engines being placed far apart. The further a mass is from the centre of gravity, the more rotational kinetic energy is needed to change the objects state of motion (for example, accelerating a mass). So the further apart the engines are on a two engined plane, the more time it takes to INITIATE a roll. Once you are rolling at a decent speed, the rotational momentum will give you a fast roll rate, but on the other hand you also take longer to stop rolling.
Jets do not have the prop clearance issue so apart from a strip of armour and heat absorbent material they can be placed closely next to each other resulting in a most of the aircrafts's mass being more closely grouped in the centre. So less kinetic energy is needed to initiate a roll.
In combat you usually only roll in one direction for a relatively short time before stopping the roll, levelling or changing the direction of roll, so having the mass concentrated near the centre of the plane is preferable for rolling.
The P38 needed power boosted airelons to improve its roll rate.
On the other hand the P38 seemed a good turner = more lift from the prop thrust going over the wings?
The two engine configuration was chosen after the war, mainly because jets were being built after the war, and as the thrust/weight ratio wasnt big enough, they used to engines for safety/speed/effeciency. The earliest jets just werent good enough, and with the dual jet configuration, one could flame out or get shot out and you'd still have the power of one jet to work with.
Having one engine is always bad news for reliability. The Fighting Falcon has suffered alot of crashes because it depends on one engine, and also depends on its flight control computer, which can suffer glitches like any computer
But it is more maneuvrable than the twin engine Eagle as more of its mass is concentrated in the centre of the aircraft.
P-51 needed to be a lot faster and higher to fight against a P-38, as at least one P-51 driver told his Nephew.
Acording to many pilots that flew both they prefered the P-38 dogfighting and Stienhoff cited the "Clear superority of the Lightning in speed and maneuverability" for the loss of air superority over Sardinia.
Art Heiden prefers the P-38L with comments like - theres nothing the doomed German pilot can do to get away from the P-38L or "The Mustang was a delight to fly, easier to maintain, chealer to build and train pilots for and had long legs. In those respects you could say it was better, but it could not do anything better than a P-38J-25 or L".
A twin has some advantages and depending of design intent/efficency disadvantages. The point made above about propellar clearance is true and it could have disastours cosequenses on the handling of a twin engined fighter.
Advantages (counter rotating props/jet engines)
2. Load capacity for fuel and ordanence
3. Stability for aiming and flying
4. Great stall characteristics in all regimes
5. Engine/prop tourque Help during maneuvering
6. Tricycle gear are easier to mount (Reciprocating engines normaly mounted in front)
b. Maintenance (though in the case of the P-38 engines overhaul rates on both Allisons were only about 25% greater than one Merlin and 30% greater than one 2800.
2. Fuel consumption (though the P-38 used 1,030gal for 2,600mi to a P-47Ns 1,165gal for 2,300mi)
3. Size (again the P-38 is only larger than a P-51/P47 from above)
I mention the P-38 for two reasons first I'm more familiar with it and second I think I paved the way and convinced those concerned that a twin engined fighter was not only viable but could be very competitive ans versatile.
It isn´t clear that in post wartimes twin engined were generally preferred over single engined ones:
He-178: single engined
EF28/39: single engined
He-280: twin engined
Me-262: twin engined
He-162: single engined
P-80: single engined
Meteor: twin engined
Vampire: single engined
MIG-9: twin engined (because of the low thrust output of BMW-003)
MIG-9TR: single engnined improvement of the original Mig-9 (TR-1)
F-84: single engined
Saab-9: single engined
Mig-15: single engined
F-86: single engined
Mig-17: single engined
As we see, the twin engined fighter doesn´t dominate the single engined ones.
No, there is and will be a place for both esp when they compliment each other as in the F-16 and the F-15.
The P-38 had a lot of trouble being accepted as a first class fighter esp in England where a lot of former P-40 pilots were, and couldn't accept the reality that the P-38 (or any twin) was viable as a fighter, 20th FG as an example, and were never happy until the P-51 came along. By the wars end the P-38 and yes, the Hornet, showed that a high performance twin was capable of not only taking on a single engine fighter but a lot more.
Today there many, maybe more twin engine fighters as single engine fighters, Im not sure that would be true without planes like the P-38 and the Hornet.
F-16 vs F/A-18 is a fairer comparison of a big single engine versus two smaller ones, the F-15 has the same F101 engine type as the F-16 but its a bigger heavier aircraft which will always be a difficult burden to overcome in close combat as their thrust to weight ratio is similar.
Something like a P-47 with a huge single engine vs a P-38 with two smaller ones is probably the most fair example from WW2, ironically you have the P-38 twin engined aircraft turning better than the P-47 which is more of a boom and zoom type. The P-38 was an exceptional aircraft though, pretty much every other twin (piston) engined attempt at a fighter in WW2 was hopeless in air to air combat with the bf110 being the prime example.
This seems to be a very knowledgeable group. I'm new here, but old, 74.
I've flown aircraft with 1, 2, 3, and 4 engines, jet and prop. I like two engines as close to the centerline as possible. My favorite was/is the
F2H-3 BANSHEE. I flew it in 1955-56 in VF-152, and deployed to WESTPAC aboard the USS WASP CVA 18.
The new Boeings with 2 engines, ie the B-767 is a good performer, but a handful on one engine. Lot's of yaw problems.
The L-1011 had some yaw problems too, but not as severe, and was easier to handle. I retired with this one in 1987. The very best autopilot in the world as far as I'm concerened. Autoland was flawless.
BTW, I flew for 34 years and accumulated about 20,000 hours, and NEVER lost an engine. All my experience with engine out were in the TWA simulator, thank God.