Global Hawk Aerial Refueling - Which Way?


Senior Member
Oct 5, 2009
Global Hawk Aerial Refueling - Which Way?

There is a wrinkle to Northrop Grumman's plans to demonstrate the autonomous aerial refuelling of one Global Hawk by another at high altitude - the tanker will fly behind the receiver.

Concept: Northrop Grumman

The tanker will be equipped with a refuelling probe and the receiver with a hose-drum unit - the opposite of the normal probe-and-drogue arrangement - and it is the tanker that will rendezvous with the receiver, maneuver into contact with the basket and "push" fuel forward to the receiver.

Northrop says this "reverse" refueling arrangement reduces the cost of equipping a Global Hawk fleet for aerial refueling because fewer aircraft need permanent modifications. Only tankers would need probes and relative-navigation systems; receivers could be fitted with underfuselage hose-drum units as required.

Equipping the Global Hawk for autonomous aerial refueling is expected to extend its endurance to 120-125h from 30-35h unrefueled. This could also save money, Northrop says, as fewer aircraft would have to be equipped with expensive payloads to maintain continuous coverage. Examples include staring sensors for missile defense, or unique payloads for NASA science missions.

NASA's two Global Hawks will be used for the DARPA-funded KQ-X demonstration in 2012. AV-1 will be equipped as the tanker and AV-6 as the receiver. Flight tests are to begin in mid-2011. Northrop says the contract includes the option to conduct a one-week flight.

Probe-and-drogue refueling has been around since the 1940s. but no-one has attempted it with unmanned aircraft at high altitude (up to 60,000ft) and low speed (160ft), where deploying and stabilizing the drogue will be a challenge because of the low air density and dynamic pressure.

KQ-X is a follow-on to DARPA's autonomous aerial refuelling demonstration in 2006 where a NASA F/A-18 refueled "hands off" from an Omega 707 tanker (video below). Northrop will use the same Sierra Nevada relative-navigation system, with differential GPS for rendezvous and an optical tracker to guide the probe into the drogue.

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