Documents I have on the Spit I show the following (below FTH its fairly linear):
Increasing climb speed from 160 mph EAS to 175 mph EAS costs about 28 ft/min in climb rate. Increasing climb speed from 160 mph EAS to 200 mph EAS costs about 315 ft/min in climb rate. This would suggest that increasing the climb speed on a Spit IX from 170 IAS to 182 mph IAS would have a negligible effect on climb rate.
Thanks. That sounds much more like what I was expecting, with little change at the start, a more rapid drop off as speed increases towards maximum
What I think Crump is arguing is that while the Spit can climb faster than the Fw190 at 182mph it needs a steeper angle to do so and because of that cannot simply follow the Fw190's exact path.
There is a lot of confusion between angle of climb and angle of attack on this thread.
Angle of attack means a plane is travelling in a different direction to the one it's facing, although only very slightly. In level flight, the angle of attack of the wings has to be slightly positive to provide lift. The slower you are going, the higher the angle of attack.
The same is true in climbs. The nose will not follow the angle of climb exactly.
That's true in all attitudes of flight.
It's like saying a Spit cannot get a guns solution on a Fw 190 in level flight because the Spit needs a positive angle off attack, and if he depresses his nose to bring the 190 under his sights, he won't have enough lift, and will start to descend, or if he pulls the nose up he will have too much lift and will start to climb.
It's true, but it's only a minor difference, and of course affects every aircraft. Using an AoA comparison, no plane can follow another in a climb.
He isn't arguing about climb rates. He is talking about climb rates at a given AoA. Using made up numbers, it would look something like this:
Spitfire LF.IX at a 18.5 degree AOA and 170mph climbs at 4,700fpm
Angle of attack is relative to the direction of travel.
So if your flight path is angled up 15 degrees, and your angle of attack was 18.5 degrees, your plane would appear to an outside observer to be pointing up at 33.5 degrees.
Here's a good explanation of the difference:
http://142.26.194.131/aerodynamics1/Performance/climb.htmlTherefore at 182mph the Spitfire has the choice of either matching/exceeding the Fw190's climb, or matching the Fw190's AoA. It can do one or the other, but not both.
This is true in level flight, and for all aircraft that require different angles of attack.
If a Spit and a 190 are side by side in level flight at the same speed, they will have slightly different angles of attack.
If the Spit tries to match the 190s angle of attack at that speed, he will start to climb, but very slowly.
If the 190 tries to match the Spit's angle of attack, he will start to dive, very slowly.
These are minor differences every aircraft has trying to follow another plane, in climb, dive or level flight.
Sin(climb angle) = Climbrate/Speed
IF you climb at 182mph and an angle of 14.5º, you MUST be doing 4000fpm.
Exactly. The climb angle and speed determine rate of climb.
The AoA is seperate, and is just the ammount you need to angle the wings of the plane relative to climb angle to maintain lift.
I don't think so. Different wing designs generate differing ammounts of lift.
Angle of attack is small, though, whereas the angle of climb is much greater.
As an example, at 200 IAS, the Spit VIII at 7500 lbs required an angle of attack of 1 degree.
That means to maintain level flight, the wings had to be 1 degree above horizontal.
To maintain climb, the wings have to be 1 degree above climb angle.
If you assume the 190 needed 2 degrees angle of attack at the same speed, if both were climbing at 18 degrees, then the Spits wings would be 19 degrees above horizontral, the 190s 20 degrees.
But they would both be following the same path.
If they both kept the same speed, they would both be exactly the same distance apart when they reached the top of the climb.
The Spit might need to make adjustments in it's climb angle to bring the 190 under it's sights, but they are simply adjustments, just as you make adjustments in level flight to bring guns to bear.
