FLUG REVUE Aircraft Gallery: EADS/Boeing X-31

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EADS/Boeing X-31A

Type (Muster)
Experimental aircraft for high angle of attack research (Versuchsflugzeug zur Erforschung von Flügen mit hohen Anstellwinkeln)

Country (Land)
Germany/USA (Deutschland/USA)

Manufacturer (Hersteller)
EADS Militärflugzeuge
81663 Munich
Germany
Phone: 0049-89/607-27081
Fax: 0033-89/607-24096

Boeing (previously Rockwell International) is a partner in the programme

General (Allgemeine Angaben)
Crew (Besatzung): 1

Power plant (Antrieb): 1 x General Electric F404-GE-400 turbofan
Thrust (Schub): 1 x 71,17 kN (16000 lbs) with reheat (mit Nachbrenner)

Dimensions (Abmessungen)
Length (Länge): 14,85 m with nose probe, 12,39 m fuselage only
Heigth (Höhe): 4,44 m
Span (Spannweite): 7,26 m
Wing area (Flügelfläche): 21 sq m (226,3 sq ft)

Weights (Massen)
Empty weight (Leermasse): 5175 kg
Fuel (Kraftstoff): 1876 kg
Normal take-off weight (normale Startmasse): 6620 kg
Max. take-off weight (max. Startmasse): 7230 kg

Performance (Flugleistungen)
Max. speed (max. Fluggeschwindigkeit): about Mach 1.3
Max. climb rate (Max. Steigrate): 218 m/s at sea level
Operational ceiling (Dienstgipfelhöhe): 12200 m (43000 ft)
Take-off run (Startrollstrecke): 460 m
Take-off distance to 15 m (Starstrecke über 15-m-Hindernis): 823 m
Landing distance over 15 m (Landestrecke über 15-m-Hindernis): 1130 m
Landing run (Landerollstrecke): 825 m
g-limit (g-Limit): +9/-4 g

Customers (Kunden)
Two X-31 (BuAer. No. 164584 und 164585) were built under contract of the US Naval Air Systems Command.

Costs (Kosten)
Programme costs were about 400 million DM, with the German share being in the region of 100 million DM.
In the new Vector test programme starting in 2000, the 53 million US-Dollars are shared roughly equally between the US and Germany.

Remarks (Bemerkungen)
The X-31 is the first US X-plane developed in co-operation with another country, and also the X-plane with the most flights to date (580 in the original programme, more now at Patuxent River).
It is based on conceptual work by MBB (later Dasa and now EADS Military Aircraft) to investigate extreme manoeuvrability far beyond the stall, helped by thrust vectoring. Angles of attack of 70 degrees were achieved, as well as entirely new manoeuvres such as 360 deg rolls at this AoA and 180 degree heading reversals "on he spot".
The German share of the X-31 included development and manufacture of the wings and the thrust-deflecting paddles – both of carbonfirbre composite material. The German team was also given responsibility for the software of the digital flight-contol system, and a special display symbology for easing post-stall flight manoeuvres.
On the equipment side, the X-31 employed numerous components and subsystems from existing aircraft.
For the revival of the X-31 in connection with the Vector programme to test extremely short landing capability at high angles of attack right down to the runway, new systems were incrementally fitted:
* upgraded Flight Control Software
* a high precisision, GPS-based landing system. IBLS (Integritiy Beacon Landing System) to achieve an accuracy measured in centimetres by differential carrier wave GPS data with inertial data. This allows automaitic landings at angles of attack of 12 degrees and speeds down to 100 kts.
* FADS (Flush Air Data System), developed by EADS and Nord-Micro, allows measuring angle of attack, angle of sideslip, Mach number and altitude form redundant pressure measurements at the tip of the radome.

History (Geschichte)
MBB started work on thrust vectoring and high-alpha manoeuvrability in the mid-70s. While in Europe no partners coult be found, Rockwell International declared its interest and joined in 1983. Feasibility studies ensued from late 1984. A US-German MoU was achieved in May 1986 for further preliminary design work.
In August 1988, the construction of two prototypes was funded, with final assembly being made at Palmdale (California). Rollout was in March 1990, and the first aircraft made its maiden flight on 11 October 1990, with the second following on 19 January 1991.
The vectoring paddles were added later, being flown for the first time on 14. February 1991. Post-stall testing commenced in the autumn of 1991, with 52 degrees AoA being reached by the end of the year. In 1992, testing moved to NASAs Dryden facilites at Edwards AFB. The envelope was extended to 70 degrees AoA, with rolls and other manoeuvres being performed in this flight regime.
In 1993, a series of tactical trials was conducted, with dissimilar combat against F-14s and F/A-18s. The X-31 performed very well in these tests.
Main point of the investigations in 1994 was lateral/directional stability and control by thrust vectoring, with funding provided by the JAST programme (now JSF). On 19 January 1995, one prototype crashed after control was lost. The investigation found that the pitot was iced, giving false air data readings to the computers. The pilot ejected safely.
In May 1995, the remaining X-31 was airlifted to Dasa in Manching and then flown to Le Bourget for demonstrations during the Paris Air Show.
After several years in storage, Dasa (now EADS Military Aircraft) and Boeing (which has bought Rockwell) secured the so-called Vector programme to reactivate the X-31. A US-German Memorandum of agreement was signed in April 1999, in the hope that Sweden would follow during the summer. This did not happen, and so a two-nation go-ahead was decided at the end of 1999. Boeing got its contract in December 1999, with Dasa following in April 2000. At that time, a programme running to February 2002 was envisaged.
Vector (Vectoring Extremely Short Take Off and Landing Control Tailless Operational Research) is valued at about 53 million US-Dollars. Its main objectives are:

·Landings with alphas of up to 40 degrees, to reduce approach speeds from 160 to slightly around 90 - 100 KIAS. Approach angles of atack up to 70 degrees witl be investigated using simulation.
·Calibration and validation of a new miniaturized flush air data system (AADS) that is radar compatible (i.e., can be installed in the nose tip) and able to provide accurate information throughout the AoA range. This part is designed and built by EADS. Two different versions will be tested
·Studies concerning reduced tail/tailless configurations. No money is available for flight tests here, so just wind tunnel work and concept exploration of the flight control laws will be done.

The X-31 was ferried aboard a C-5 Galaxy from Palmdale in California to Naval Air Station Patuxent River in Maryland in mid-April 2000. It was then prepared for checkout flights, which were targeted to start in August.
In the end, the second "first flight" took place on 26 February 2001, with Commander Vivan "Noodles" Ragusa at the controls. He piloted the aircraft to a height of 10000 ft, with speeds of 400 kts and anlges of attack up to 30 degrees. More functional test and calibration flights followed until April 6, with Ragusa an German test pilot Rüdiger "Rudy" Knöpfel in the cockpit.
The X-31 then went into a layup phase, receiving modifications such as the air data system, new navigation system etc. In parallel, software development for the automatic landing phase was conducted.
A first in-flight test phase of the new Flight Control Software 123A as well as the new GPS based Landing System (IBLS = Integrity Beacon Landing System) and the FADS (Flush Air Data System) began on 17 May 2002 with a functional check flight by Rüdiger Knöpfel. At that time, first ESTOL tests were predicted by the end of the summer. In the end, the preparations lasted until October 2002. Some 24 flights with a total of more than 17 hours were performed by pilots Rüdiger Knöpfel (WTD 61) and Vivan Ragusa (US Navy). Speeds of Mach 0.9 and angles of attack of up to 45 degrees wer successfully achieved.
The first ESTOL landings to a virtual runway 5000 feet up in the air were then performed on 18 November 2002 by US Major Cody Allee. Five more ESTOL approaches were performed the next day. Angle of attack was 12 and 14 degrees at first, with 24 degrees on later flights. The aim is to reach 45 degrees.
The next step (Phase III) will be ESTOL approaches down to the real runway at Patuxent River. These are scheduled for early 2003. Additionally speeds above Mach 1 and angles of attack higher than 70 degrees will be tested until the end of 2003, EADS said in October 2002. This is to test the FADS air data system.
Currently test pilots engaged in the ESTOL programme are Knöpfel, Allee and Lt. J. R. Hansen, who made its first test flight in the X-31 on November 19, 2002.
Long term studies to flight test the thrust vectoring nozzle developed by ITP in Spain for the EJ200 engine powering the Eurofighter were conducted some time ago but are far from certain.

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Last updated 28 December 2002

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