Aerial refueling improvement ideas and resources

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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 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.
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.
(1) The nozzle at the end of the boom.
(2) Confusingly also the tip of the probe mast.
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.


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

Related content

FlightGear wiki



Forum topics

Developer mailing list threads

Source code

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.

NATO Standards

Contains both performance specifications and dimensional drawings.

US military standards


Manufacturers of refueling equipment

Research papers

YouTube videos


  • 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 refueledIllustrating the director lights under the forward tanker fuselage indicating to the receiver where he is in the boom envelope.