An interesting photo from Iran. An American Lockheed Martin KC-130 Hercules tanker and Sikorsky HH-60 Pave Hawk helicopters connected to it. If you think about it, it’s incredibly complex. Look, the plane has to fly at a super low speed for it – close to the stalling speed – while the helicopters, in contrast, must push to their limits to keep up. To avoid entering into a spin, the plane is forced to rapidly lose altitude, consequently, the helicopters must also purposely drop altitude. The helicopters are positioned lower than the plane, so if the pilot slows down even more (though how much more can he slow down?), and the helicopters don’t slow down, the hose could hit the rotor blades and that’s it. The helicopters also gain several tons during refueling, which adds to the complexity. Why refuel two at once? It’s more complicated. Actually, it’s both more complicated and simpler, because the load on the wings is distributed symmetrically, making it easier for the plane to maintain a stable course. It’s also interesting how the issue of static electricity is handled in the dry air.
A good addition from the comments (Sergey Snegirev):
1. It is noted that the Hercules stalls at 100-110 knots (depending on the air temperature and altitude, which is important in Iran), and the photo shows the flaps deployed, allowing it to stay up to even 90 knots. Meanwhile, the Pave Hawk can accelerate up to 190 knots (but obviously, nobody performs AAR at max speed), with a cruising speed of 150 knots, so there’s quite a sizable overlap. It’s assumed that AAR takes place around 120 knots on the video.
3. It is noted that AAR happens at exactly the same altitude, so there’s no need to lose altitude
4. It is noted that the tanker – like any other aircraft – can dissipate static electricity using an electrostatic discharger. The refueling hose has a contact that equalizes the potentials of the two aircraft before fuel delivery.
5. It is noted that the fuel used to refuel external aircraft is stored in tanks in the aircraft’s cargo section, separate from the tanker’s own fuel system. Even if the pumping were from the tanker’s own fuel tanks, it would come from the central tank, which is set up to transfer fuel from the side tanks.
It is noted that on the underside of the plane’s wings, several metal “antennas” are installed on the flaperons to discharge static electricity into the air. It is noted that when the hose is connected, a wire passes through and the potentials on the bodies are equalized.
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