Originally posted by streakeagle
The quote about being safe with the 7 degree line probably includes the range bonus that comes from having a speed significantly higher than 210 knots optimum glide range speed during flameout (probably 400 to 500 knots). Per the procedure, this speed will be traded for additional altitude which will permit recovery at the optimal 10 degree angle.
I disagree, if they meant that you could only make it if your airspeed was high enough to begin with, I assume they would have said so. If there was a speed below which you couldn't make it, I'm sure they would have qualified it. The fact that they say you know you can get there, regardless of other factors, providing you have a 7º glide slope, implies that the 7º already includes a safety margin and it also implies that you could make it regardless of the airspeed you had at the time. Particularly since flameout due to compressor stagnation stalls, for example, are more likely to occur at high angles of attack and low speeds, and are also covered by that statement.
If the information from Zigrat's F-16 drag polar is correct (Isn't the genuine F-16 drag polar classified?) then a L/D of 10 gives a glide slope of only 5.7º. Now I know that L/D is not constant, and may be slightly lower at the speeds and altitudes we are considering, but this could be the source of the safety margin for the 7º glide slope, a margin of 1.3º equivalent to the difference between the 8:1 and 10:1 glide slope.
The F-16 Documents suggest that 7º is possible, while Zigrat's F-16 drag polar suggests that something in the order of 5.7º may even be possible, but in practice it seems pilots count on much less. I'm sure the reason would be that they need to maintain a considerable margin in order to execute maneuvers in the landing pattern and so on. I found this interesting account, that suggests that in practice F-16 pilots expect far less. Notice the rule of thumb:
"Tigre 83 was on what would normally be considered a low threat cross-country sortie; if there is such a thing in a single-engine fighter! Twenty-five nautical miles west of El Paso International, the tone of the sortie took on a drastic change when his aircraft suffered catastrophic engine failure and flamed out. This all occurred at 18,000 feet above ground level and 550 knots true airspeed. Every F-16 pilot knows that the rule of thumb for simulated flameout (SFO) landings is to be at an altitude (thousands) equal to your distance from the intended landing. If you do the math in this problem, it is obvious that any delays in turning back would have resulted in a completely different outcome. Even with Maj Overturf's immediate execution of the critical action procedures, this SFO would require all of his piloting skills to safely recover his crippled F-16 to a heavily populated area. In fact, had this occurred a mere 30 seconds later, the Air Force inventory would be short one F-16C. It's situations like this that help reinforce the single-engine mentality of always being aware of the closest piece of concrete."
After all that, what surprises me the most about this is that most WWII aircraft, actually look less aerodynamically efficient than the F-16, but they all appear to have a far better L/D ratio and can glide much farther. Amazing.
Badboy
