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Howto:Aerial refueling: Difference between revisions
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== In the Air == | == In the Air == | ||
=== General procedure === | |||
Turn to an appropriate heading, guided by the TACAN bearing (you should try a "leading" approach to close in on the tanker) and look for the tanker on the radar or nav. screen. Around 5nm away, you should reduce your speed to around 20kts faster than the tanker (these fly at 280 kts TAS) - a "slow overtake". The KC135 will be visible from about 10nm, the KA6-D, being smaller, just over 1 nm. You should use airbrakes as necessary to keep control of your speed should you find yourself overshooting. | Turn to an appropriate heading, guided by the TACAN bearing (you should try a "leading" approach to close in on the tanker) and look for the tanker on the radar or nav. screen. Around 5nm away, you should reduce your speed to around 20kts faster than the tanker (these fly at 280 kts TAS) - a "slow overtake". The KC135 will be visible from about 10nm, the KA6-D, being smaller, just over 1 nm. You should use airbrakes as necessary to keep control of your speed should you find yourself overshooting. | ||
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Once your tanks are full, or you have taken as much fuel as you wish, close the throttle a little, back away from the tanker and continue your intended flight. | Once your tanks are full, or you have taken as much fuel as you wish, close the throttle a little, back away from the tanker and continue your intended flight. | ||
=== Troubleshooting the approach === | |||
If you had problems approaching the tanker, then it's useful to understand just what the cause of the difficulty is, so that you know what to practice. In a nutshell, what you have to do is to fly to the right spot behind the tanker, <i>in such a way that the relative velocity with the tanker is zero</i>. The first part, flying to the correct position, is easy - just keep the tanker centered in your visual field and fly till you are there. All the trouble is in matching the velocity. Successful Air-Air Refueling thus requires precision control of your airspeed. | |||
This, again, would be no problem if the throttle would directly control your airspeed - then you could just set the throttle to the airspeed you need as soon as you reach the right spot. However, the throttle controls thrust, and airspeed results from an equilibrium between thrust and drag which takes some time to reach. Let's assume you have reached the right spot behind the tanker with the correct airspeed, but with insufficient thrust, and see what happens: Since the drag force is now larger than the thrust, the plane starts to settle into a new equilibrium and the airspeed will slowly drop. A few seconds pass before the airspeed gauge reflects this, as gauges usually do not work instantaneously. Thus, but the time you notice the chance in airspeed from the gauge, the plane is already slower than the gauge indicates. Assume you try to correct you increasing thrust a bit. It takes a few moments before the turbine spins up to the new RPM setting (like gauges, they don't react instantaneously), then more thrust is generated. From that moment on, it takes a few seconds for the plane to settle into a new equilibrium airspeed corresponding to that thrust level. By the time that is reached, some 20 seconds may have passed - and you may find yourself already far behind the tanker! | |||
That time-lag between recognizing airspeed changes and reaction of the plane to thrust is the prime reason why Air-Air Refueling is so difficult. A second reason is that planes usually do not just get slower when you reduce thrust or apply airbrakes - the nose of the aircraft tends to drop as well and you have to compensate. The solution to all problems is that you need to anticipate the reaction of the aircraft to what you're doing and that you need to act quickly and decisively. For this, you have to know the aircraft you're flying well. | |||
First, <i>never</i> fly by the airspeed gauge in close proximity to the tanker, always react to <i>what you see</i> - if you see the tanker fly away, you are too slow no matter what the airspeed gauge says! If you react to what you see, you gain precious seconds (and that takes care of the wind effects, i.e. the fact that the tanker flys TAS whereas you IAS as well). Second, change thrust before you see the effect. Assume in the above example, you'd give a short burst of thrust, then put the thrust lever back to a slightly higher setting than it was before. If done just right, the airspeed drop gets compensated almost immediately and the new equilibrium is reached quickly without falling far behind the tanker. Finally, use altitude to your advantage instead of fighting it. If you pull the nose up, you'll lose just a bit of airspeed, so if you approach a bit below the tanker being a bit faster than the tanker, you can pull up as soon as you reach the spot, and you will stop just fine in the correct spot. | |||
=== Simulation vs. reality === | |||
[[Image:f16-air-air-refuel.jpg|thumb|270px|Approaching the tanker with an F-16 - and receiving fuel already (v.1.9.1)!]] | |||
There are a few things which are (presumably) easier in the simulation as compared with the real world, but there are also some that are harder. First, the envelope for refueling is actually quite generous - you start getting fuel in a position where in the real world this could not possibly work (see picture). The real refueling position of the F-16 feels a lot less comfortable! It is also mercifully short - usually holding the plane in the correct spot for about 30 seconds is all you need. There is also no turbulence or other change in the airstream induced by the tanker modelled. | |||
What is on the other hand probably easier in real life is flying by eye - in reality, we usually don't have any problems accurately gauging relative motions of a few feet per second. On the screen, with finite resolution and not-exactly-real textures and shadows, a lot of visual cues are missing and gauging a small relative motion becomes difficult. Also, in real life both the tanker and the refueling plane fly in the same airstream and wind effects not being felt by the tanker AI model are not an issue. | |||
== More advanced topics == | == More advanced topics == | ||