Skyraider refuelling a Scimitar in the 1960s
Norman Sinsel,  President of Saber Tanker Aerial Group (STAG) wrote and told us about their work on innovative low speed air to air refuelling. Other members of the group are Sherpa Aircraft, IsoLair Helicopter Systems, and  Ryno Motors. Interesting stuff, we look forward to seeing actual UAS flight trials.
STAG is developing a technology demonstrator for USAR using the Sherpa.  The last time fixed-wing in-flight refueling (IFR) was conducted was before the start of WWII.  In fact the last time the US military performed IFR below 120 knots using fixed-wing assets—–1929.  For the last eight years I have been conducting flight test flights and research ( I’m a pilot ) in the USAR field since no one is alive today who conducted such flights or recent research in the subject.
Alan, Glen, and Michael next to Sherpa

The last decade has seen an evolution in the application of unmanned flying machines for use over the battlespace in ever growing numbers and hours flown by unmanned aircraft.  The unprecedented use of unmanned flying machines over conflicted regions have forever change how hard force is applied by nations to met the ever growing volatility the planet now sustains.  But the unmanned aerial vehicle or system has hit a wall in the technology’s ability to maintain the now vital around the clock presence required by the users of unmanned flying assets.  A crisis has developed in the last several years in the ability of the UAV to stay over the battlespace as long as possible without the need to return to the airbase to be refueled.

The UAV has become the go to aviation asset to supply persistent low cost real time video intelligence, surveillance, and reconnaissance (ISR) of the battlespace.  But the level of persistent aerial coverage of the battlespace depends on the ability of the UAV platform to not just carry its sensors and ordnance payloads but a sufficient fuel load that allows for several hours of flight before having to return to base to be refueled on the ground.  Today this inability to maintain persistent flight without in-flight refueling (IFR) capability is no longer acceptable and is now the reason the Pentagon has developed the needed technologies which will allow class V unmanned combat aerial system (UCAS) like the X-47B to perform IFR in the not to distant future.  But if a class V UCAS will be able to perform IFR then why not class IV systems or even smaller class III unmanned aviation assets, are they not any more wanting for what the military calls “force multiplier” of air-to-air refueling?

The greater majority of UAVs operated today lack an air-to-air refueling platform is due to their smaller physical size and slower airspeeds flown by class III and IV unmanned aviation assets.  Not since before the start of World War II have there been aerial refueling platforms which operate at airspeeds flown by today’s smaller slower operating UAVs.  Air-to-air refueling today is in need of a major rethink how to deliver not only fuel at ultra slow airspeeds but to deliver the new fuels now being contemplated for use for long duration flight by unmanned aviation platforms like hydrogen.  Even electrical powered flight platforms could use the resource of being recharged in mid-air if only a platform could access the needed airspeeds such unmanned aerial assets operate at.  One such technology that I designed is now being developed here in the Pacific Northwest just a few miles north of Portland Oregon.

Ultra slow flight is problematic for the air-to-air refueling process.  Fixed-wing aircraft when operating at minimum controllable airspeeds require the wing to operate at very high angles of attack to maintain fixed altitude flight.  This places the fixed-wing platform nose high above the horizon and very close to stall airspeed a position not advantageous for a refueling tanker let alone for the receiving aircraft asset operating behind such a tanker.  Toss in turbulence during the refueling process you then have a situation that is very dangerous to the aerial refueling process.  What was needed to be solved first was to allow for greatly reduced angle-of-attack while still being able to operate at minimum controllable airspeeds by the IFR tanker.  I solved it.

Maintaining level flight pitch attitude at very slow airspeeds where accomplished through the use of several decades old flight proven, off-the-shelf devices and methods which are now combined in a proprietary business method for the use of IFR and electrical aerial recharging at airspeeds between 50 and 150 knots.  The devices and methods used for USAR will allow even small Cessna’s too perform aerial refueling or electrical aerial recharging.  The key is not only having stable level flight at ultra slow airspeeds but the refueling/recharging booming technology itself to allow for IFR to small UAVs.

Small airframes like class III and IV UAVs are very susceptible to atmospheric or wake turbulence from an IFR aircraft itself.   I have been a small aircraft pilot since the early-seventies. Currently I have over 3200 hours of flight time, having flown in turbulence that has placed my aircraft briefly into uncontrolled flight I was very conscious in developing a refueling boom that would place the receiving aircraft out of any wing/fuselage induced or prop wash turbulence during the refueling or recharging process.  Luckily what I needed had been already flight test flown and proven to allow for the receiving aircraft to maintain flight in clean undisturbed air during aerial refueling.  I made several modifications to the system that will allow for the aerial refueling/recharging of UAVs, fixed or “rotor-wing” at ultra slow airspeeds where the original system had no allowances for such multiple operational parameters.  My booming technology places the hose and drogue a dozen feet below the tail and two dozen or more feet behind the tanker.  This position allows the UAV ether fixed or rotor-wing to be refueled or recharged in clean undisturbed air at ultra slow airspeeds.

Having flown as a tow plane pilot pulling sail planes back in the early 80s I had a pretty good idea what it would be like refueling small aircraft using a small tanker aircraft.  And having pulled sail planes in turbulent flight conditions I knew what was needed to be solved to perform USAR using light utility general aviation aircraft.

Today’s military thinkers have no idea what is involved in ultra slow flight using small aircraft platforms as tankers for UAVs.  The skills I developed over years as a bush/tow plane pilot and general aviation pilot are skills not taught in the military except for very few Special Forces pilots mostly flying rotor-wing assets.  The militaries institutional memory of small plane fixed-wing tactical flying let alone air-to-air refueling below 120 knots is ether lost or all but forgotten by today’s military pilots.  Such low, slow tactical flying was an everyday occurrence during the Vietnam War and later saw limited usage during the First Gulf War using the OV-10D Bronco.  Those Vietnam military pilots are long gone from the military or very few still in uniform from the first Gulf War.  As stated earlier what is now needed is a total rethink, a game changing rethink in aerial refueling if the unmanned aerial system is ever to evolve into a truly 24/7/365 real time aviation technology.  Such a new type of IFR tanker called the Tactical Refueling Aerial Tanker or TRAT for short will allow the UAV to truly game change the battlespace as an ISR hunter/killer platform.  I saw this crisis coming back in early 2003 after the CIA turn one of its Predators into a Hell Fire missile carrying weapons platform to turn bad guys into smoking holes.

Pandora’s Box has been opened, there is no going back and I knew those little unmanned flying machines would need to be refueled in mid-air if they are going to truly become the aviation technology of the future for hard and soft power applications.

The new 21st century refueling tanker needs to be far less costly, smaller and be able to be forward based from smaller less costly unimproved airstrips or landing areas.  Such landing areas also known as “lily pads” will allow TRATs to stay closer to the combat air patrols (CAP) of the UAVs.  TRAT lily pads would be temporary, being used for a few hours to less than a week.  TRATs would allow for new increased operational missions over longer periods of time and greater ranges by U.S. and Multi-National Coalition Forces in Southwest Asia or anywhere else in the world.  The trend is for increased levels of conflict on the global scale from failing to failed nations, multi-national criminal activity, and climate refugees seeking new lands to survive on.  The UAV will be the aviation tool to meet the growing need for 24/7/365 real time video of conflict, of the human conduction by civilian and military leaders around the world.  Low cost ISR is more than ever now required to understand what is happening to ones nation to survive the ever growing vectors which place populations and resources in jeopardy.  The UAV itself now more than ever requires the capability to be refueled/recharged in mid-air at costs which are sustainable by even the smallest of nations and budgets.

Saber Tanker Aerial Groups mission is to provide to the civilian and military aviation world a low cost aerial refueling tanker platform, one costing tens millions dollars less than today’s air-to-air refueling assets.  Today the cost of just one HC-130J is well over eighty million dollars and yet not able to perform USAR.  Today’s legacy aerial refueling tankers reflect old school unimaginative gray hair narrow minded thinking of the aerial refueling asset and is why such thinking places in jeopardy the unmanned aviation industry to grow beyond the bounds now limited to internal fuel capacity of these aircraft.  If this new world of unmanned aviation is ever to evolve too the next level of operational usefulness for the citizens of the world then the aviation world will need to be able to be refueled/recharged in mid-air at airspeeds not seen since the 1930s.  My technology is not just for unmanned aircraft but will be able to be used by manned civilian aircraft fixed or rotor-wing assets.  Just imagine EMS helicopters able to fly further offshore to boats or ships in harms way without having to worry about having enough fuel to fly back to shore or having limited time over ships with passengers in distress.  No sir the time to have a small scale slow flying low cost aerial refueling/recharging general aviation tanker asset is now here.  We as an aviation society now must now move to the next level of operational capability to maintain flight without the need too return to the ground for refueling or recharging, how old school thinking is that.

STAG is a combination of independent American businessmen who are combining their eighty plus years of aviation knowledge to create an aircraft that will allow the unmanned aviation industry to access airspeeds for IFR not seen in over seventy-five years.

By Gary Mortimer

Founder and Editor of sUAS News | Gary Mortimer has been a commercial balloon pilot for 25 years and also flies full-size helicopters. Prior to that, he made tea and coffee in air traffic control towers across the UK as a member of the Royal Air Force.

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