Aerial refueling improvement ideas and resources

Air-to-Air Refueling seen from an F-16 cockpit.

These are some aerial refueling improvement ideas as well as links to various related resources. Currently (December 2014) FlightGear both have several aircraft that can be refueled and several tankers. However there is room for improvement.

Current situation

(June 2015)

• The MRTT has been "de-hotted" by Johan G, so you can crash into it and not crash!

(Below is as of December 2014)

Boom refueling

• None of the tankers have lights indicating the aircraft position in the boom envelope or refueling status.
• Few, if any of the tankers have a moving boom.

Drogue and probe refueling

• None of the tankers have lights indicating the aircraft position or refueling status.
• The hose is fixed length and rigid.

Ideas on improvements

• Adding refueling status lights to all tankers (red, amber and green)

Drogue and probe refueling

• Borrowing code etc. used for towing gliders
  • Visualize the hose using parts or the entire towing code
  • Have the hose attached to the nacelle and the probe (with a small braking force, 320 pounds (MA-2) or 550 pounds (MA-3 and MA-4))
  • Visualize the drogue at the end of the hose

Common meanings of the signal lights

These are the most common meanings of the signal lights. There are some variations to these, but there is nearly no exception to steady amber meaning the tanker is ready and steady green meaning the fuel is flowing. The lights can also have a different arrangement, but usually there are two bulbs of each color either in the lamp or as two separate lamps.

Phase	Lights			Meaning
	Red	Amber	Green
Before contact	Steady	-	-	Do not make contact (tanker not ready or having problems)
	-	Steady	-	Tanker ready for contact, connect
In contact	-	-	Steady	Connected and fuel flowing
	-	-	-	Offload complete, disconnect / no fuel flow / soft contact or dry contact
	-	Flashing	-	Hose pushed in nearly too far (Moving more forward than 25 ft of hose trail will cut the fuel flow)
	-	Steady	-	Hose to far aft (Moving more aft than 5 ft from full hose trail will cut the fuel flow. Moving more aft than full trail will disconnect receiver.)
Any time	Flashing	-	-	Break away! (tanker problems)

According to MIL-A-19736A, section 3.7.5.1 the signal lights should be automatic for these circumstances:

Yellow light

Turned on only when the hose is within 5 feet of the trailed position and the tanker is ready for engagement.

Red light

Turned on when the hydraulic pressure at the hose reel is too low for proper response action.

Green light

Turned on when the fuel is being transferred to the receiver. The light shall be controlled by a primary element which senses actual fuel flow.

The lights can be dimmed and the yellow and red lights function for both dry and wet engagements.

Common terminology

Terms commonly used in relevant marketing material and technical references.

Aerial refueling itself

• Air-to-air refueling (AAR) (Standard NATO term and abbreviation)
• In flight refueling (IFR)
• (fr) Ravitaillement en vol

Technical terms

Boom drogue adapter (BDA)

A short hose with a drogue that can be fitted to a boom.

Boom envelope

The space the boom nozzle can move around in limited by the boom extension and the boom traverse.

Coupling

The part that is attached to the hose and to which the drogue is attached and the probe connects to

Common types are the MA-2 (unregulated flow), MA-2 (regulated flow) and MA-4 (dual redundantly regulated flow). MA probably stands for Marshall Aerospace.

Dry connect

A connect without fuel flowing. Typically the case when practicing and for qualification (in essence the fuel pumps are not used), but otherwise an anomaly.

Nozzle

(1) The nozzle at the end of the boom.

(2) Confusingly also the tip of the probe mast.

Receiver

The receiving aircraft.

Soft contact

As the drogue couplings latching mechanism requires a force up to 155 pounds to engage, approaching the coupling to slowly might not engage it, resulting in a soft contact (sometimes called a soft prodding).

If the latch is not properly engaged the nozzle and coupling may not seal and the nozzle and coupling fuel valves may not open.

Compatibility between western and other aircraft

Russian aircraft

Smaller receiver aircraft

In among others the MiG-9E, MiG-29MST, MiG-29K/KUB, Su-24, Su-30 MKI and Su-35 uses NPP Zvezda ATG-2E series nozzles that are compliant to both Russian, US and NATO standards for probe and drogue refueling (in essence the MA-2 nozzle and MA-2, MA-3 and MA-4 couplings).[1]

Larger receiver aircraft

The larger Russian aircraft like Tu-95MSb Tu-142, Tu-160, A-50 and IL-86SH uses NPP Zvezda ATG-2MS series nozzles that may be compatible with the western probe and drogue refueling systems.[2][3]

Tanker aircraft

The Russian tankers all use refueling pods. The pods are the NPP Zvezda UAPZ in variants for buddy refueling, and refueling lighter and heavier aircraft from tankers.

Chinese aircraft

Chinese tankers and receivers seem to use a mix of equipment originating from Russia and Britain.

Other

There is also some equipment from South African and Israeli companies that seems to be compatible to western systems.

Related content

FlightGear wiki

Articles

• Howto:Aerial refueling
• Howto:Implement aerial refueling capability
• Howto:Setup winch and aerotowing for JSBSim-aircraft
• Scripted AI Objects

Categories

• Category:Air refueling ready
• Category:Military tanker aircraft

Forum topics

• Making drogue slave to probe after contact in AAR (First post in 24 May 2013)
• 707-xx pics (First post in 24 Oct 2013) (Also contains links to technical documentation.)
• Realistic Hose-Drogue Based Aerial Refueling (First post in 21 Nov 2013)
• More tanker problems (First post in 22 Aug 2014)
• Aerial refueling, tanker offsets and contact radius(First post in 23 Aug 2014)

Developer mailing list threads

• Air-to-air refuelling enhancement (First post in 24 February 2013)
• Air-air refueling (First post in 13 May 2013)
• Air to air refueling probe/receiver positions (First post in 29 January 2014)

Source code

• fgdata/Nasal/tanker.nas
• fgdata/Aircraft/Generic/aar.nas
• fgdata/Nasal/towing/hitch.nas

External links

NATO handbook

The national annexes contain detailed information of tankers, fuel flows, signal light differences, boom envelopes, hose lengths and markings, drogue dimensions, tanker–reciver clearance matrices etc.

• Air-to-Air Refuelling. Published by NATO Joint Air Power Competence Centre. Retrieved 21 November 2020. - Host of all related documents, including national annexes etc.
• Air-to-Air Refueling Clearance and Compatibility Database (AAR Matrix). Published by NATO Joint Air Power Competence Centre. Retrieved 21 November 2020.
• NATO Standard ATP-3.3.4.2 Air-to-Air Refueling, Edition D, Version 1 (pdf). Published by NATO Standarization Office (NSO). Retrieved 21 November 2020.

NATO Standards

Contains both performance specifications and dimensional drawings.

• NATO Standard ATP-3.3.4.6 Air-to-Air (Aerial) Refueling Equipment: Probe–Drogue Interface Characteristics, Edition A Version 1 (PDF). Published by NATO Standardization Office (NSO). Retrieved 1 July 2020.
• NATO Standard ATP-3.3.4.7 Air-to-Air Refuelling Signal Lights in Hose and Drogue Systems Edition A Version 1 (PDF). Published by NATO Standardization Office. Retrieved 1 July 2020.
• NATO Standard ATP-3.3.4.5 Air-to-Air (Aerial) Refuelling Equipment: Boom-Receptacle System and Interface Requirements Edition A Version 1 (PDF). Published by NATO Standardization Office. Retrieved 1 July 2020.

US military standards

• MIL-R-27521A, Military Specification: Receptacle, Flying Boom, Aerial Befueling, General Specification for (24-JUN-1971) (dpf). Published by EverySpec.com. Retrieved 3 February 2015. – Requirements for refueling flying boom receptacles.
• MIL-A-19736A, Military Specification: Air Refueling Systems, General Specification for (dpf). Published by EverySpec.com. Retrieved 31 December 2014. – Relates to drogue and probe refueling only.
• MIL-PRF-81975C, Performance Specification: Couplings, Regulated, Aerial Pressure Refueling Type MA-2, Type MA-3 and Type MA-4 (dpf). Published by EverySpec.com. Retrieved 22 December 2014. – Contains the drawing of the externally equal MA-3 and MA-4 coupling on page 28.
• MIL-N-25161C, Military Specification: Nozzle, Aerial Pressure Refueling, TYPE MA-2 (pdf). Published by EverySpec.com. Retrieved 22 December 2014. – Probably not that useful, but I include it anyway.

Drawings

• MS27604A, Military Standard: Nozzle - Universal Aerial Refueling Tanker Boom (pdf). Published by EverySpec.com. Retrieved 22 December 2014.
• MS24355B, Military Standard: Coupling, Reception - Type MA-2, Flight-pressure-refueling, Assembly of (ASG) (dpf). Published by EverySpec.com. Retrieved 22 December 2014.
• MS24356D, Military Standard: Nozzle - Type MA-2, Flight Pressure Refueling (ASG) (dpf). Published by EverySpec.com. Retrieved 22 December 2014.

Manufacturers of refueling equipment

• Cobham Mission Systems
• NPP Zvezda, Russia (Through Google translate)

Research papers

• Jennifer L. Hansen, James E. Murray and Norma V. Campos. The NASA Dryden AAR Project: A Flight Test Approach to an Aerial Refueling System (pdf). Published by American Institute of Aeronautics and Astronautics. Retrieved 3 February 2015. – Contains diagrams of free stream drogue position vs. tanker airspeed, AoA and altitude.
• Michael Jacob Vachon, Ronald J. Ray and Carl Calianno (February 2004). Calculated Drag of an Aerial Refueling Assembly Through Airplane Performance Analysis (pdf). Published by NASA Dryden Flight Research Center. Retrieved 3 February 2015. – Contains diagrams of hose and drogue assembly drag vs. tanker airspeed, AoA and altitude.
• Ujjar Bhandari, Peter R. Thomasy, Steve Bullockz and Thomas S. Richardsonx (2013). Bow Wave Effect in Probe and Drogue Aerial Refuelling (pdf). Published by American Institute of Aeronautics and Astronautics. Retrieved 3 February 2015.
• Andrey V. Styuart, Hisako Yamashiro, Robert Stirling and Marat Mor (2011). Numerical Simulation of Hose Whip Phenomenon in Aerial Refueling (pdf). Published by American Institute of Aeronautics and Astronautics. Retrieved 3 February 2015. – Contains examples and explanation of the hose whip phenomenon.

YouTube videos

• F18 Pilot Refueling Mid-Air (8:34 min) – Cockpit view of boom-drouge adapter (BDA) refueling.
• Italian Air Force Aerial Refueling Exercise Accident (1:10 min) – Illustrating the hose whip phenomenon and the effects it can have.
• Дозаправка МиГ-31 и Су-24 в воздухе (10:00 min) – Illustrating the bow wave phenomenon.

Other

• Mike Gaines; Sergei Skrynnikov (photographer) (19 - 25 February 1992). Buddy-buddy Fencer (pdf). Published by Flight International. Retrieved 22 December 2014. – Russian Su-24 Fencer air to air buddy refueling and Il-78 Midas refueling and techniques.
• Dr Carlo Kopp (27 Jan 2014). The PLA-AF's Aerial Refuelling Programs. Retrieved 22 December 2014. – Note the signal light colors on the NPP Zvezda UPAZ pods.
• Photo of the F-35 being boom refueled – Illustrating the director lights under the forward tanker fuselage indicating to the receiver where he is in the boom envelope.