F-104 Starfighter Corner Speed

[hawker111 1]

Does anyone know what the corner speed should be for the F-104?

 

Thanks,

 

Hawker111

[Fubar512 1,350]

It's quite high, in excess of 450 KIAS according to published charts.

[+streakeagle 871]

This graph for the F-104A should give you an idea of F-104 corner speed (Vc):

Edited January 29, 2015 by streakeagle

[+streakeagle 871]

Be wary of the limits of the above graph: clean with flaps and gear up... and less than 1,000 lbs of fuel.

If you take the total weight with 1,000 lbs of fuel, you can estimate performance with higher fuel loadings by using the weight ratio to reduce the load factor scale on the left.

i.e. if the weight is increased by 25% (5/4), then the load factor g's should be 80% (4/5) lower.

Note: this load factor reduction also applies to the 7.33g structural limit. In this example, it would now be 0.8 x 7.33g => 5.864g

Flaps down should improve the lift curves a bit up to their rated speed, but at the cost of greatly increased drag.

Keep in mind, this is not a sustained turn graph, this is the maximum load that can be pulled while the wing is at the max controllable angle of attack, which can be less than the theoretical Clmax angle since the F-104 had control issues at high AoA.

The stick pusher system that tries to prevent unstable AoA is the source of the flat spots in the curves.

Also keep in mind, the speed is IAS => indicated airspeed, not CAS/TAS, which is useful while flying but harder to read for performance evaluation/comparison.

At sea level, IAS is theoretically equal to TAS, so that is a great altitude to derive Clmax information as a function of speed.

 

According to this graph, at sea level, Vc is very close to 500 kts!

This is the price of using thin stubby wings to maximize top speed.

Edited January 29, 2015 by streakeagle

[+streakeagle 871]

For perspective, consider a clean F-4B at 50% fuel. Since the altitude is at sea level, TAS = CAS = IAS is fairly true, so it is directly comparable to the sea level data above:

[+streakeagle 871]

The unslatted F-4B can pull more g at a lower speed, which means its instantaneous performance is considerably better than the F-104A/C depicted above.

At the same 7.33g load, the F-4 only needs to fly at 420 kts, about compared to the F-104G's 490+ kts. This results in 490/420 = 16% better turn rate.

At corner speed, around 445 kts, the F-4 can pull about 8.5g, leading to 8.5/7.33*490/445 = 27% better turn rate.

I don't know how accurate the information is, but this graph is way cool. Keep in mind that the slatted F-4E generally turns better than the F-4B by a good margin given how much better the F-4B turns compared to the F-104:

[+streakeagle 871]

An interesting point is at Mach 0.8. At 10,000 ft that is about 500 kts, a typical starting point for air-to-air combat, which is commonly evaluated at Mach 0.9.

Around that point, the F-14A performs nearly identical to the F-4E in both sustained and instantaneous.

Down to Mach 0.5, just over 300 kts, the F-14A's sustained performance is about 20% better than the F-4E, while its instantaneous is about 72% better.

The power-to-weight advantage of the F-15C over the F-14A is very apparent from this graph.

So only knowing the v-n diagram which establishes instantaneous performance limits doesn't quite tell the whole story.

The weight/payload greatly affect performance: the F-16C does not sustain 9gs when the wings are cluttered with missiles and pylons -- too much weight, drag and lost lift.

It is a shame the F-14D isn't shown, as it would reflect how simply changing the available thrust greatly affects the same airframe.

[+streakeagle 871]

Back to the F-104, based on the v-n diagram, 200 kts IAS is the 1g speed for both sea level and 20,000 ft, so the curves for the F-104 would start at about Mach 0.36 on the color graph.

The instantaneous rate would peak at about the same spot as the F-4E.

[Caesar 305]

Streak,

 

The F-14B/D has the roughly same sustained turn rate as either the F-15C (-220) or F-16 at 10,000 feet, but it achieves that turn at only ~.63M, thus with a better radius (given 4x AIM-7 and 4x AIM-9, and about 60% fuel remaining) but based on TACTS data, the "max lift" line is a little too low if landing flaps are considered.