marsavian wrote:I noticed the turn chart for the air to air mode for the F-15SA has a quite sharp drop after corner velocity compared to clean. Is that due to the weight of the CFT and extra fuel or its drag and how was it computed ?

I'm looking at the turn chart now.

The "Air" configuration does not show a sharp drop after corner velocity (0.9M in this figure) in the ITS or STR curves. After corner velocity ITR for Air is the same as Clean. After corner velocity STR for air is gradually decreasing. There IS a marked reduction in ITR before corner velocity for Air when compared to Clean due to the drastic increase in weight. Please clarify what you are asking about so I can help.

marsavian wrote:With the computed thrust/weight ratios at 36kft are these with afterburner i.e. is the thrust of the -229 at that altitude only around 10 klbf with afterburner, just over a third of sea level rating ?

Yes they are in afterburner. If you re-read section 1.3.2 on Thrust to Weight I explain all the factors that go to reduce engine thrust below rated levels.

In this case, at 36,000ft the air density is 29.8% that of sea level. There is also a gearbox loss that is fixed at 15% of rated military thrust, or 2,670 per engine. I also assume an airflow loss at lea level of 1,869lb for friction on the inlet. I double the airflow loss for afterburner due to the increased speed. The airflow loss does get reduced proportionally to air density.

So if we take the rated engine thrust of 29,500lb and move it to 36,000ft at zero airspeed we apply the air density factor.

Now we are at 8,791lb. Take out the gearbox loss next, as the systems being powered by the engine don't care about what altitude the plane is at, they need power. Now we are down to 6,121lb. Afterburner airflow losses is nominally 3,738 but is reduced to 1,114lb due to reduced air density. Now we are down to 5,007lb of installed static afterburning thrust.

But thrust goes up with speed, especially at altitude. My model has a 70% increase in engine thrust for this speed and altitude. That gets applied to the air density corrected rated thrust after airflow reduction (7,677lb) to raise it to 13,051lb. The gearbox, like the taxman, always gets its due, lowering the thrust to 10,381lb.