Thread by @BaA43A3aHY

McDonnell F-4 Phantom II - The Flying Brick 🧵

When trying to read about the F-4 Phantom II, I come across the expressions like "the triumph of thrust over aerodynamics" or "even a brick can fly if you stick a big enough engine on it".

Even the president of the McDonnell Douglas aircraft company, George S. Graff mentions this at the minute mark 21:48!

So I started to wonder if the F-4 Phantom has mediocre aerodynamic properties? I decided to first search for its minimum CD₀ (zero lift drag coefficient). The first source that I checked was "Quest for Performance: the Evolution of Modern Aircraft" by L. K. Loftin Jr. (1985).

The data in his book does indeed indicate that the F-4E has a pretty high minimum CD₀ = 0.0224, compared to other fighters in the list.

Side note: I have a whole new love for the F-106A & B-58A. Convair Power!💪

But I'm not sure that set of values is wind tunnel or flight tests data. If they are flight test data, and maybe that's the slatted F-4E, then what about a non-slatted? In NASA CR-2144 we have some other values:

F-4C CD₀ ≈ 0.0183 (with 4 AIM-7?)
F-104A CD₀ ≈ 0.015 (clean?)

A bit better. What about Soviet aircraft for comparison?
According to the manual, the MiG-21UM with two R-3S mounted, has a CD₀ ≈ 0.0168. R-3S with launcher & pylon CD₀ = 0.002.

The MiG-21F-13 seems to be even better.

The MiG-23ML on the other hand is worse than the F-4 in the subsonic domain. But with the wings swept back it's really low drag rise at supersonic. Witnesses the benefits of a swing-wing design!

What about maximum lift-to-drag ratio. Well according to all of my F-4 Phantom II flight manuals, with windmilling engines, the glide ratio is 7.29. The highest L/D that I could find for the Phantom is listed here, 8.58:

Ok, so the CD₀ & L/D aren't great, but not terrible either. But that weird tail surely must be an aerodynamic catastrophe, right? Well no, the 23° anhedral on the horizontal tail solved the problem of pitch-up, that McDonnell encountered on the F-101.

The 12° dihedral helped too, according to Loftin's book.

And the tail-boom configuration helped shorten the inlet ducts, reducing pressure loses due to boundary layer effects. At first it looks like a big source of base-drag, but according to SAE paper "Optimizing Exhaust. Nozzle/Airframe Thrust Minus Drag - 680294 - 1968-04-29":

EBR = equivalent body of revolution, simulates the area distribution of the real aircraft by replacing it with one which has circular cross sections.

So according to this wind tunnel test, the aft fuselage of the F-4 is better at high Mach numbers than an A-5 Vigilante one.

And finally, the lift curve. Judge for yourself. It's on par with many aircraft of its generation and before it. Here are some for comparison:
F-8, max CL = 1.0
F-8 cruise droops, max CL = 1.05
F-100D no slats, max CL = 0.94
F-100D slats, max CL = 1.07

Here's the MiG-23ML's lift curve

OK Phantom fans, after reading all of this, what's your opinion on this?

Spey💪

Sparrow lunch.

Sageburner, misinterpreted edition.

Brick and mortar