Hi HoHun,
That diagram is only intended to illustrate the principles involved, I left the numbers off deliberately so that discussions about any particularly values wouldn’t cloud the principles involved. Having said that, even though I haven’t indicated any particular speed, I agree that taken in proportion with the rest of the diagram it does appear a tad too fast, so I have edited the diagram.
Originally posted by HoHun
Hi Badboy,
My disagreement with that diagram is only the position of the dotted line on which the B-C segment runs. This is the speed of best climb, and for WW2 propeller fighters, it's usually farther to the left. If it would run through point A, then the diagram would look good to me :-)
However, I also think that point A would be below the correct speed for most WWII fighters. If we put some numbers to it, (which I hope won’t lead to any hair splitting) just for the purpose of discussion, we can assume that the speed axis of the diagram has major tick marks at 100mph intervals, and that the altitude axis has major tick marks at 10,000ft intervals. If that is the case, we can see the diagram represents a fighter with a top speed at sea level of 350mph, and a top speed of 450mph at its critical altitude of about 24,000ft.
Now, if that is the case, then the scenario we are looking at here is this… Imagine our pilot has just been in a hard turning engagement, he has been riding the edge of the envelope and the enemy aircraft tries to pull his nose high, he pulls up to follow him gets enough lead for a shot and hanging on the prop gets the kill. The bandit explodes, showering his canopy with hair teeth and eyeballs! He then becomes aware of another threat. At that point our pilot is at point A, 20k and 150mph, and then dives to the speed for best energy transfer, at around 190mph and 18k. He then climbs, increasing his speed to about 230mph at point C at just over 30k, and then dives back to a speed of 320mph at a slightly lower altitude, which places him close to his corner velocity at that altitude, and ready to maneuver.
Of course, if he was already cruising at a speed of say 250mph at point A, he would need to zoom climb, and if he was already close to the 190mph speed for best energy transfer, he could simply execute his climb without either the diving or zooming part.
Originally posted by HoHun
The reason this makes a difference is that the lines of equal energy have less curvature there so that relatively little altitude can be converted into the speed needed to reach the dotted line.
The type of dive involved here isn’t just any old dive, in order to dive and gain speed most quickly with the least cost in energy it should be a zero g dive that minimises the induced drag. Following an Es curve down, should always get you the best speed gain for the least loss in altitude, regardless of where it is on the diagram.
Originally posted by HoHun
Accelerating from 100 mph to 160 mph IAS by putting the nose down a little while going at full throttle probably wouldn't be perceived as a dive because it's over rather quickly :-)
I agree, but those speeds are below the sort of speeds I had in mind, and I think that 160mph is too low for the best energy transfer speed, particularly for the heavier late war fighters, which is why I have been trying to stick to general principles and avoid discussing numbers. I think there have been a lot of threads on that topic already, and being specific will always cloud the issues because it doesn’t matter what numbers are used, there are always exceptions.
Originally posted by HoHun
But anyway, the important point that remains is - how do you determine the optimum point D? :-)
Interestingly enough, the practical execution of the technique has a lot in common with the methods used to calculate it, because those methods are numeric and iterative. Carrying out those calculations for educational purposes is instructive, but unfortunately carrying out the calculations for specific cases in combat is only of any real value if you have the advantage of modern GCI or AWACS that can stream the data to onboard computers, where you can apply it in real time… Otherwise a certain amount of judgement is required, which is how fighter pilots have been applying the technique since Korea. In terms of a more practical approach, the speeds for best energy transfer are given in the dash one of most third generation fighters and used to determine the climb schedules. When notified by ground controlled intercept of an approaching enemy, a modern fighter pilot, if below the best energy transfer speed, would unload to zero g until they reach that speed, then climb to an altitude above the enemy if possible. I’ve already described an optimal approach for an imminent engagement, but if the bandit tried to run away, the pilot would continue to climb to 36k for the chase, and in a prop fighter you might go to the critical altitude for the chase for maximum speed. There is an article on SimHQ where I describe the Co-E chase. Everything else remains as described, but one last point, how do you do it in Aces High?
Well, these technique can also be used in that way to good advantage in AH. In order to explain what I mean in terms of the practical application, let’s consider how you would apply these principles in the duelling arena with both pilots starting on the runway. Firstly, both pilots might take off on auto climb, but climbing right off the runway is the wrong thing to do, because it takes too long for the aircraft to accelerate to the best climb speed while climbing. Ideally, you would like to unload and get to that speed as soon as possible, just as I’ve shown in the diagram, but because you are already on the deck you just lift off and accelerate in level flight until you reach a speed just above the best climb speed, then you begin to climb.
Now, you climb as rapidly as possible as your radar dots approach each other. At some point you know you need to convert some of your altitude back to airspeed for the impending merge, and you have asked what is the point D in terms of airspeed and altitude, but more importantly, the way I apply it, is how do you determine point C, the point when you commit to the push over. Once you begin the push over at point C, point D will be determined by your initial timing and experience. Begin the push over too late, and you may not have enough speed at the merge, begin it very late, and you may lose sight of the bandit. Begin the merge too early, and you will gain too much speed, and lose energy and maneuverability. Also, when you time your push over will depend on the type of engagement you intend to fly, if you intend to follow the merge with a zoom climb for an energy fight, or whether you intend to pitch back vertically, or slice it, for an angles fight. And there are a lot of variations. In a duel, guys even try to disguise their energy by diving steeply and throttling back during their descent. However, the real secret is being very familiar with your aircraft handling qualities, so that your timing and judgement are correct, or at least close enough. That’s why some guys spend many hours practicing these techniques in duels until they have honed their skills and can judge the correct timing against any type of enemy aircraft and engagement style. If you don’t think this works, take any experienced AH pilot to the duelling arena, and see what they do, if they are good, the only thing that will change, will be how well they do it
Hope that helps…
Badboy
