Maximum Speeds Of WW2 Aircraft

[Sid327]

This is a question, not a statement.

Why is maximum speed considered important. Particularly when this is usually restricted to a time limit of not much more than five minutes in a lot of cases.

Doesn't cruise speed @ maximum continuous power (along with altitude) tell a better story and give a more telling idea?

 

[BiffF15]

This is a question, not a statement.

Why is maximum speed considered important. Particularly when this is usually restricted to a time limit of not much more than five minutes in a lot of cases.

Doesn't cruise speed @ maximum continuous power (along with altitude) tell a better story and give a more telling idea?

Sid327,

Max or top speed for the most part tells of power available. The Do-335 had a tremendous top speed (piston fighter) but not what you would want to be flying in a slow speed fight with a smaller single engine fighter. However, a small single engine fighter with a 30+ MPH advantage over other small single engine fighters has much more power reserve available in a slow speed fight, as well as the ability to exit that might not or doesn't exist for his lower power adversaries. Top speed is a tool, and can be an indicator of other tools / advantages.

Cheers,
Biff

 

[tomo pauk]

This is a question, not a statement.

Why is maximum speed considered important. Particularly when this is usually restricted to a time limit of not much more than five minutes in a lot of cases.

Maximum speed advantage can enable you to catch an opponent - we can recall that one of main job of fighters was to catch & destroy enemy bombers, not just fighters. Faster fighter can disengage far easier than slower fighters. Five minutes at 600 km/h = 50 km, so a fighter that is going reasonably fast can cover a lot of space in those 5 minutes.

Doesn't cruise speed @ maximum continuous power (along with altitude) tell a better story and give a more telling idea?

Aircraft rarely cruised on max continuous power, usualy lower power settings were used. Of course, usually the plane A that can cruise @ 500 km/h is money better spent than a plane B that will cruise @ 450 km/h on same power setting, problem being often that plane B is earlier available for squadron use.

 

[Shortround6]

to add to Biff's statement for much of WW II if you knew the top speed of an airplane you could calculate or estimate it's cruising speed as many engines had a max continuous power rating that was a percentage of the full power (like 90% or 80%), this did change a bit from engine to engine and there were a couple of odd balls where there was a wide variation but there was a general rule of thumb.

WEP could change that but WEP usually only worked at altitudes below where the max speed was achieved anyway since WEP usually worked at lower altitudes where there was more drag due to the thicker air.

 

[GregP]

The WWII pilots I have spoken with weren't very concerned with maximum speed. They were much more concerned with armament, combat speed, combat acceleration, turning, and rolling.

Normally, when they saw the enemy, they had maybe 15 - 25 seconds or less before closure, maximum ... usually less. That assumes an enemy fighter coming toward you, not a tail chase. Combat speed is the speed you'd be at if you started accelerating at max power upon sighting the enemy. It was usually around 300 - 350 mph, no more. Of course, Biff15 is right ... if you have a plane capable of 450 mph at your altitude, you probably have better combat speed and acceleration than one capable of 410 mph at that altitude.

If your aircraft was a good turner, you'd use turn rate to get on someone's tail. If your aircraft was a good roller, you'd use rolling maneuvers to avoid letting someone get on YOUR tail. Turning was more important for offense, roll was more important for defense. Speed was relatively unimportant as long as you had enough to close and fight or get away from a fight, whichever was appropriate for you at the time. WWII was not a conflict where vertical maneuvering was all that important because WWII fighters aren't all that good at vertical climbs. They aren't much use for more than 3,000 - 4,000 feet going vertical, and that's if they had a good turn of speed to start with.

The vertical is a lot more important for jets, especially once jets approach or have 1 : 1 or better thrust to weight ratios. If your thrust to weight is 0.5 or less, you're in a turning fight, more than likely. If it is 0.7 and up, you're likely in a vertical fight ... assuming fuel doesn't cause you to break off and run for home or a tanker. Somewhere in the middle of that is a scissors fight that can go upward or downward, depending on thrust. Whoever runs out of energy first is in trouble. The last place you want to be "out of airspeed, altitude, and ideas," which means you are in the gunsight reticle of the opponent.

I'd bet that Biff15, being an F-15 pilot, was likely very seldom, if ever, out of altitude, airspeed, and ideas, all at the same time! If it has nothing else, the F-15 isn't usually out of power unless maybe if you are flying on one engine.

 

[BiffF15]

The WWII pilots I have spoken with weren't very concerned with maximum speed. They were much more concerned with armament, combat speed, combat acceleration, turning, and rolling.

Normally, when they saw the enemy, they had maybe 15 - 25 seconds or less before closure, maximum ... usually less. That assumes an enemy fighter coming toward you, not a tail chase. Combat speed is the speed you'd be at if you started accelerating at max power upon sighting the enemy. It was usually around 300 - 350 mph, no more. Of course, Biff15 is right ... if you have a plane capable of 450 mph at your altitude, you probably have better combat speed and acceleration than one capable of 410 mph at that altitude.

If your aircraft was a good turner, you'd use turn rate to get on someone's tail. If your aircraft was a good roller, you'd use rolling maneuvers to avoid letting someone get on YOUR tail. Turning was more important for offense, roll was more important for defense. Speed was relatively unimportant as long as you had enough to close and fight or get away from a fight, whichever was appropriate for you at the time. WWII was not a conflict where vertical maneuvering was all that important because WWII fighters aren't all that good at vertical climbs. They aren't much use for more than 3,000 - 4,000 feet going vertical, and that's if they had a good turn of speed to start with.

The vertical is a lot more important for jets, especially once jets approach or have 1 : 1 or better thrust to weight ratios. If your thrust to weight is 0.5 or less, you're in a turning fight, more than likely. If it is 0.7 and up, you're likely in a vertical fight ... assuming fuel doesn't cause you to break off and run for home or a tanker. Somewhere in the middle of that is a scissors fight that can go upward or downward, depending on thrust. Whoever runs out of energy first is in trouble. The last place you want to be "out of airspeed, altitude, and ideas," which means you are in the gunsight reticle of the opponent.

I'd bet that Biff15, being an F-15 pilot, was likely very seldom, if ever, out of altitude, airspeed, and ideas, all at the same time! If it has nothing else, the F-15 isn't usually out of power unless maybe if you are flying on one engine.

Greg,

Excellent post! Except for that part where I never ran out of ideas, airspeed, or altitude. I did. When you fight an identical plane, or one with better performance, you can fly yourself into a square corner, out of airspeed, and altitude all at the same time. Did it!

I fought a clean (no tanks, not combat realistic) F-16C block 30 big mouth (30 means mongo large GE motor, and big mouth means the intake was enlarged to feed said mongo motor). Serious thrust to weight advantage / turn advantage. I start offensive, fly a very aggressive wire (tight fight with more closure but more chance of an error causing big set backs). I did great until we get to the floor (5k) and I flush outside his turn circle just a little. He was slow, probably under 200kts, and as soon as i let up pressure he rolled wings level and did a loop. I was awestruck. Asked him on the radio how fast he was going (we never do that), and complimented him when he told me. He then finished his loop and gunned the crap out of me!

On the WW2 front vertical maneuvering can also be in the down direction as gravity can help, along with denser air for more power and G. When you fight a similar plane today, it seems to end up going downhill no matter what.

Cheers,
Biff

 

[GregP]

Better maneuverability combined with better power to weight is an advantage HARD to beat, assuming everything else is nominal.

You know, Biff, I'm SURE you know they offered a stealthier F-15 with better avionics to the Military, but the DOD (or whoever made the decisions) was mesmerized by the F-22, which was selected after changing the test specs that the YF-23 passed and the F-22 didn't pass so the F-22 could compete. I was never sure why Northrop didn't take them to court on that one. If the F-22 could only pass lowered specs, then Northrop should have been awarded money to develop a follow-on to the YF-23 that could just barely pass the NEW specs.

Old argument, I know. Not to say anything is wrong with the F-22, but the YF-23 passed the ORIGINAL specs and SHOULD have been a shoo-in winner. I never DID like the fact that the YF-23 always seemed to pull a contrail from the wingtip whenever it turned with any G-load, but it met the specs as originally issued.

 

[Reluctant Poster]

Fighters came into existence because reconnaissance aircraft and bombers had to be stopped. Interception was still one of the main tasks for fighters in WWII. High speed and high rate of climb were extremely important in that role, much more than maneuverability.

 

[pinsog]

Greg,

Excellent post! Except for that part where I never ran out of ideas, airspeed, or altitude. I did. When you fight an identical plane, or one with better performance, you can fly yourself into a square corner, out of airspeed, and altitude all at the same time. Did it!

I fought a clean (no tanks, not combat realistic) F-16C block 30 big mouth (30 means mongo large GE motor, and big mouth means the intake was enlarged to feed said mongo motor). Serious thrust to weight advantage / turn advantage. I start offensive, fly a very aggressive wire (tight fight with more closure but more chance of an error causing big set backs). I did great until we get to the floor (5k) and I flush outside his turn circle just a little. He was slow, probably under 200kts, and as soon as i let up pressure he rolled wings level and did a loop. I was awestruck. Asked him on the radio how fast he was going (we never do that), and complimented him when he told me. He then finished his loop and gunned the crap out of me!

On the WW2 front vertical maneuvering can also be in the down direction as gravity can help, along with denser air for more power and G. When you fight a similar plane today, it seems to end up going downhill no matter what.

Cheers,
Biff

Biff15's story sounds like a Wildcat/Zero story from 1942. Biff is in the Wildcat and the F16 was the Zero

 

[Sid327]

tomo pauk (thank you)

Posted a report in this thread: Bf-109E vs Hawker Hurricane Mk I

Which was quite interesting, as it gives an example of two aircraft with disimilar maximum speeds.

 

[K5083]

History usually (but not always) shows the faster fighter in the ww2 context to be the more successful one. Now, it is true that fighters did not fly around at level top speed. But say a P-51 faces a 109G. Top speeds are 440 mph vs 400 (ish) . At 400, where the 109 can only go level or dive without losing speed, the 51 has excess power at around 30% of the total. That's some 500hp to use for climb without losing speed, or turning or whatever maneuver. That translates to (very roughly) 1500 ft.min climb rate. So what you get with a higher top speed, without ever using it to fly level, is a lot of freedom. Second, if they keep the speed up, new guys will survive the first few missions. Thirdly, the speed advantage will help in closing with the enemy or in getting away. That 109 has a climb rate advantage in the books, but if the 51 keeps up his speed he will be flying rings round the 109 even though it has that best climb and (maybe) a better turn rate too. In the books.

A word about diving. In the dive from cruise, the aircraft with the best power/weight will accelerate faster at first. Then there will be a stage where the best top speed wins and later when the best weight over drag, or ballistic coefficient. takes over.

Anyhow, all things being equal faster is always better. The exceptions being when training, armament, tactics or just plain dogginess tips the balance.

 

[Sid327]

Thank you for a lot of good posts,

I agree it's confidence boosting and telling in most cases to have the speed advantage.
Though the abilty to manouevre sufficiently well at combat speeds is helpful too. Some of the faster planes may not have been able to do this.
Power to weight ratio is all important also and this may not always translate to a better max speed.
If the more agile plane has a better endurance this could also tip the balance.

 

[K5083]

Hence the superiority of the Gloster Gladiator, CR42 and Ki-97 over all the monoplane retractable-gear fighters...oh.

I think the crux here is that the faster aircraft's pilot has options that the slower guy does not have.

 

[Sid327]

Hence the superiority of the Gloster Gladiator, CR42 and Ki-97 over all the monoplane retractable-gear fighters...oh.
I think the crux here is that the faster aircraft's pilot has options that the slower guy does not have.

Yes, you are probably right.
Though there was a speed difference between the Spitfire IX and the P-51 which one was the better dogfighter assuming equal ability? ....just one example. I'm sure there are many others, so all I'm saying is it's not a clear cut black and white statement.

 

[Greyman]

Another force acting on fighter development/speed is the fact that the same trends can and do apply to bombers. If fighters don't follow suit and take advantage of every speed increase the bomber does -- they're quickly rendered pointless ... dogfight ability be damned.

 

[pinsog]

Better maneuverability combined with better power to weight is an advantage HARD to beat, assuming everything else is nominal.
.

This comment also sounds like a 1942 Wildcat vs a Zero thread

 

[K5083]

It's not so much power to weight as excess power to weight. The power you use just to fly at a given speed is already used up, if you want to do something else on top, like turn or climb, it is the excess power that enables it. Now excess power over weight just happens to be specific excess power, which is what the Boyd energy maneuverability theory is all about. It is expressed as a rate of change of altitude, positive or negative. Anyhow, the faster fighter will always have a flight regime where he has a positive SEP and the other guy does not. Where he effectively has better power to weight even though on paper it is worse.