View source for Aerial refueling improvement ideas and resources

[[File:F16-air-air-refuel.jpg|250px|thumb|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.

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== 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.

{| class="wikitable"
! rowspan="2" | Phase
! colspan="3" | Lights
! rowspan="2" | Meaning
|-
! {{no|Red}}
! {{partial|Amber}}
! {{yes|Green}}
|-
| rowspan="2" | Before contact
| {{no|Steady}} || {{n/a|-}} || {{n/a|-}}
| Do not make contact (tanker not ready or having problems)
|-
| {{n/a|-}} || {{partial|Steady}} || {{n/a|-}}
| Tanker ready for contact, connect
|-
| rowspan="4" | In contact
| {{n/a|-}} || {{n/a|-}} || {{yes|Steady}}
| Connected and fuel flowing
|-
| {{n/a|-}} || {{n/a|-}} || {{n/a|-}}
| Offload complete, disconnect / no fuel flow / soft contact or dry contact
|-
| {{n/a|-}} || {{partial|Flashing}} || {{n/a|-}}
| Hose pushed in nearly too far (Moving more forward than 25 ft of hose trail will cut the fuel flow)
|-
| {{n/a|-}} || {{partial|Steady}} || {{n/a|-}}
| 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
| {{no|Flashing}} || {{n/a|-}} || {{n/a|-}}
| 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).[https://translate.googleusercontent.com/translate_c?act=url&depth=1&hl=sv&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ru&tl=en&u=http://www.zvezda-npp.ru/ru/node/532&usg=ALkJrhj5ieceo6Gwfda0t2dlwWJi7yj-wg]

==== 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.[https://translate.googleusercontent.com/translate_c?act=url&depth=1&hl=sv&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ru&tl=en&u=http://www.zvezda-npp.ru/ru/node/532&usg=ALkJrhj5ieceo6Gwfda0t2dlwWJi7yj-wg][https://translate.googleusercontent.com/translate_c?act=url&depth=1&hl=sv&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ru&tl=en&u=http://www.zvezda-npp.ru/ru/node/531&usg=ALkJrhjyVr1ODz8kRHI1vIwGkMTMJwSK-w]

==== 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 ===
* [http://forum.flightgear.org/viewtopic.php?f=30&t=20028 Making drogue slave to probe after contact in AAR] (First post in 24 May 2013)
* [http://forum.flightgear.org/viewtopic.php?f=19&t=21158 707-xx pics] (First post in 24 Oct 2013) (Also contains links to technical documentation.)
* [http://forum.flightgear.org/viewtopic.php?f=6&t=21359 Realistic Hose-Drogue Based Aerial Refueling] (First post in 21 Nov 2013)
* [http://forum.flightgear.org/viewtopic.php?f=25&t=23888& More tanker problems] (First post in 22 Aug 2014)
* [http://forum.flightgear.org/viewtopic.php?f=66&t=23893 Aerial refueling, tanker offsets and contact radius](First post in 23 Aug 2014)

=== Developer mailing list threads ===
* [http://sourceforge.net/p/flightgear/mailman/message/30526429/ Air-to-air refuelling enhancement] (First post in 24 February 2013)
* [http://sourceforge.net/p/flightgear/mailman/message/30825774/ Air-air refueling] (First post in 13 May 2013)
* [http://sourceforge.net/p/flightgear/mailman/message/31902325/ Air to air refueling probe/receiver positions] (First post in 29 January 2014)

=== Source code ===
* {{fgdata file|Nasal/tanker.nas}}
* {{fgdata file|Aircraft/Generic/aar.nas}}
* {{fgdata file|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.

* {{cite web
 | url = https://www.japcc.org/aar/
 | title = Air-to-Air Refuelling
 | publisher = NATO Joint Air Power Competence Centre
 | accessdate = 21 November 2020
 }} - Host of all related documents, including national supplements etc.
* {{cite web
 | url = https://www.japcc.org/aar/matrix/
 | title = Air-to-Air Refueling Clearance and Compatibility Database (AAR Matrix)
 | publisher = NATO Joint Air Power Competence Centre
 | accessdate = 21 November 2020
 }}
* {{cite web
 | url = https://www.japcc.org/?file=7645
 | title = NATO Standard ATP-3.3.4.2 Air-to-Air Refueling, Edition D, Version 1
 | date = April 2019
 | publisher = NATO Standarization Office (NSO)
 | format = pdf
 | accessdate = 21 November 2020
 }}

=== NATO Standards ===
Contains both performance specifications and dimensional drawings.

* {{cite web
 | url             = https://nso.nato.int/nso/zPublic/ap/ATP-3.3.4.6%20ED%20A%20V1%20E.pdf
 | title           = NATO Standard ATP-3.3.4.6 Air-to-Air (Aerial) Refueling Equipment: Probe–Drogue Interface Characteristics, Edition A Version 1
 | date            = June 2016
 | publisher       = NATO Standardization Office (NSO)
 | format          = PDF
 | accessdate      = 1 July 2020
 }}
* {{cite web
 | url             = https://nso.nato.int/nso/zPublic/ap/atp-3.3.4.7%20eda%20v1%20e.pdf
 | title           = NATO Standard ATP-3.3.4.7 Air-to-Air Refuelling Signal Lights in Hose and Drogue Systems Edition A Version 1
 | date            = March 2013
 | publisher       = NATO Standardization Office
 | format          = PDF
 | accessdate      = 1 July 2020
 }}
* {{cite web
 | url             = https://nso.nato.int/nso/zPublic/ap/ATP-3.3.4.5%20EDA%20V1%20E.pdf
 | title           = NATO Standard ATP-3.3.4.5 Air-to-Air (Aerial) Refuelling Equipment: Boom-Receptacle System and Interface Requirements Edition A Version 1
 | date            = June 2013
 | publisher       = NATO Standardization Office
 | format          = PDF
 | accessdate      = 1 July 2020
 }}

=== US military standards ===
* {{cite web
 | url = http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-R/MIL-R-27521A_41232/
 | title = MIL-R-27521A, Military Specification: Receptacle, Flying Boom, Aerial Befueling, General Specification for (24-JUN-1971)
 | date = 24 June 1971
 | publisher = EverySpec.com
 | format = dpf
 | accessdate = 3 February 2015
 }} – ''Requirements for refueling flying boom receptacles.''
* {{cite web
 | url = http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-A/MIL-A-19736A_17611/
 | title = MIL-A-19736A, Military Specification: Air Refueling Systems, General Specification for
 | date = 5 August 1960
 | publisher = EverySpec.com
 | format = dpf
 | accessdate = 31 December 2014
 }} – ''Relates to drogue and probe refueling only.''
* {{cite web
 | url = http://www.everyspec.com/MIL-PRF/MIL-PRF-080000-99999/MIL-PRF-81975C_42388/
 | title = MIL-PRF-81975C, Performance Specification: Couplings, Regulated, Aerial Pressure Refueling Type MA-2, Type MA-3 and Type MA-4
 | date = 22 January 2008
 | publisher = EverySpec.com
 | format = dpf
 | accessdate = 22 December 2014
 }} – ''Contains the drawing of the externally equal MA-3 and MA-4 coupling on page 28.''
* {{cite web
 | url = http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-N/MIL-N-25161C_22246/
 | title = MIL-N-25161C, Military Specification: Nozzle, Aerial Pressure Refueling, TYPE MA-2
 | date = 10 July 1969
 | publisher = EverySpec.com
 | format = pdf
 | accessdate = 22 December 2014
 }} – ''Probably not that useful, but I include it anyway.''

==== Drawings ====
* {{cite web
 | url = http://www.everyspec.com/MS-Specs/MS2/MS27000-MS27999/MS27604A_41012/
 | title = MS27604A, Military Standard: Nozzle - Universal Aerial Refueling Tanker Boom
 | date = 27 August 1971
 | publisher = EverySpec.com
 | format = pdf
 | accessdate = 22 December 2014
 }}
* {{cite web
 | url = http://www.everyspec.com/MS-Specs/MS2/MS24000-MS24999/MS24355B_39046/
 | title = MS24355B, Military Standard: Coupling, Reception - Type MA-2, Flight-pressure-refueling, Assembly of (ASG)
 | date = 12 February 1963
 | publisher = EverySpec.com
 | format = dpf
 | accessdate = 22 December 2014
 }}
* {{cite web
 | url = http://www.everyspec.com/MS-Specs/MS2/MS24000-MS24999/MS24356D_39049/
 | title = MS24356D, Military Standard: Nozzle - Type MA-2, Flight Pressure Refueling (ASG)
 | date = 12 February 1963
 | publisher = EverySpec.com
 | format = dpf
 | accessdate = 22 December 2014
 }}

=== Manufacturers of refueling equipment  ===
* [https://www.cobham.com/about-cobham/mission-systems/air-to-air-refuelling.aspx Cobham Mission Systems]
* [https://translate.google.com/translate?sl=ru&tl=en&js=y&prev=_t&hl=sv&ie=UTF-8&u=http%3A%2F%2Fwww.zvezda-npp.ru%2Fru%2Ftaxonomy%2Fterm%2F18&edit-text=&act=url NPP Zvezda, Russia] (Through Google translate)

=== Research papers ===
* {{cite web
 | url = http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040085352.pdf
 | title = The NASA Dryden AAR Project: A Flight Test Approach to an Aerial Refueling System
 | author = Jennifer L. Hansen, James E. Murray and Norma V. Campos
 | publisher = American Institute of Aeronautics and Astronautics
 | format = pdf
 | accessdate = 3 February 2015
 }} – ''Contains diagrams of free stream drogue position vs. tanker airspeed, AoA and altitude.''
* {{cite web
 | url = https://www.nasa.gov/centers/dryden/pdf/88778main_H-2551.pdf
 | title = Calculated Drag of an Aerial Refueling Assembly Through Airplane Performance Analysis
 | author = Michael Jacob Vachon, Ronald J. Ray and Carl Calianno
 | month = February
 | year = 2004
 | publisher = NASA Dryden Flight Research Center
 | format = pdf
 | id = NASA/TM-2004-212043
 | accessdate = 3 February 2015
 }} – ''Contains diagrams of hose and drogue assembly drag vs. tanker airspeed, AoA and altitude.''
* {{cite web
 | url = http://people.bath.ac.uk/jldb20/pubs/Bhandari.etal2013BowWaveEffect.pdf
 | title = Bow Wave Effect in Probe and Drogue Aerial Refuelling
 | author = Ujjar Bhandari, Peter R. Thomasy, Steve Bullockz and Thomas S. Richardsonx
 | year = 2013
 | publisher = American Institute of Aeronautics and Astronautics
 | format = pdf
 | id = AIAA 2013-4695
 | accessdate = 3 February 2015
 }}
* {{cite web
 | url = http://enu.kz/repository/2011/AIAA-2011-6211.pdf
 | title = Numerical Simulation of Hose Whip Phenomenon in Aerial Refueling
 | author = Andrey V. Styuart, Hisako Yamashiro, Robert Stirling and Marat Mor
 | year = 2011
 | publisher = American Institute of Aeronautics and Astronautics
 | format = pdf
 | id = AIAA 2011-6211
 | accessdate = 3 February 2015
 }} – ''Contains examples and explanation of the hose whip phenomenon.''

=== YouTube videos ===
* [https://www.youtube.com/watch?v=1vhHs7k1zwg F18 Pilot Refueling Mid-Air] (8:34 min) – ''Cockpit view of boom-drouge adapter (BDA) refueling.''
* [https://www.youtube.com/watch?v=eMNitOL0XcA Italian Air Force Aerial Refueling Exercise Accident] (1:10 min) – ''Illustrating the hose whip phenomenon and the effects it can have.''
* [https://www.youtube.com/watch?v=AD_8PVtY624 Дозаправка МиГ-31 и Су-24 в воздухе] (10:00 min) – ''Illustrating the bow wave phenomenon.''

=== Other ===
* {{cite web
 | url = http://www.flightglobal.com/pdfarchive/view/1992/1992%20-%200425.html
 | title = Buddy-buddy Fencer
 | author = Mike Gaines
 | coauthors = Sergei Skrynnikov (photographer)
 | date = 19 - 25 February 1992
 | publisher = Flight International
 | format = pdf
 | accessdate = 22 December 2014
 }} – ''Russian Su-24 Fencer air to air buddy refueling and Il-78 Midas refueling and techniques.''
* {{cite web
 | url = http://www.ausairpower.net/APA-PLA-Tanker-Programs.html
 | title = The PLA-AF's Aerial Refuelling Programs
 | author = Dr Carlo Kopp
 | date = 27 Jan 2014
 | accessdate = 22 December 2014
 }} – ''Note the signal light colors on the NPP Zvezda UPAZ pods.''
* [http://www.f-16.net/g3/f-35-photos/album551/album560/AF-04_002_001 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.''

{{air-to-air refueling}}

[[Category:Aerial refueling]]