Lockheed U-2S

Not to be confused with Lockheed U-2.

Tip  The version described in this article is not the one from the official download page / FGAddon repository. The version described here can be obtained from my GitHub repository: https://github.com/rebootl/U-2S-git/releases

Lockheed U-2S

Type	Ultra-high altitude aircraft, Reconnaissance aircraft
Configuration	Bicycle landing gear aircraft
Propulsion	Jet aircraft, Single-engine aircraft
Manufacturer	Lockheed
Author(s)	Cem Aydin
FDM	JSBSim
--aircraft=	U-2S
Status	Alpha
FDM
Systems
Cockpit
Model
Download

The famous U-2 spyplane, for FlightGear.

The FlightGear aircraft described here features the latest, modern variant of the U-2, the U-2S.

Currently (2015-10-17) it must still be considered unfinished.

The aim of this project is to create a detailed, realistic, but also fun simulation.

Therefore things like e.g. the FDM are developped with great care. The downside to this is that progress is slow.

Aircraft help

U-2S, exterior view w/ Rembrandt lights.

The simulation starts with the engine off, the aircraft is fueled to about 2/3 capacity. The APU can be thought as connected and the electrics powered on. Currently there is no custom electrical system. External lights are on.

Engine start

A simplified startup sequence is provided.

• Press and hold "s". This is thought to simulate the APU powering on.
• After about 5 seconds, when 5% of n1 are reached, put the throttle to idle. By pressing } or middle mouse click on the throttle.
• The engine will increase to 60% of n2 and then start. Release "s".

The engine can be started by windmilling, when there is enough altitude to bring the engine to the needed n values. Use above procedure but without pressing "s". This is not (yet) a customized system but the default JSBSim behaviour.

Takeoff

• Close the canopy (Shift-c) and release the parking brake.
• Throttle to full.
• After a short time the pogos will fall off, keep the wings level.
• At about 80 kt the tail will start to rise. Try to keep the two point position.

Climb

• Try to keep 160 kt up to 50,000 ft by adjusting pitch.
• Between 50,000 and 70,000 ft decrease the speed gradually to 105 kt.

Descent

• Throttle to idle.
• Extend the speedbrake (Ctrl-b) and lower the gear.
• Descent with speeds from 105 to 160 kt.
• Below 50,000 ft speed may be increased up to 220 kt.

Landing

• Full flaps.
• Throttle as needed.
• Threshold should be passed 10 ft above ground.
• Touchdown should be made on main and tail gear together. To do this the aircraft is stalled at 1 ft above ground. At this point the main and tail gear should be aligned to the flight direction.
• Try to keep the wings level as long as possible.
• At 60 kt brakes can be applied gently and at 30 kt fully. (Currently the braking force is reduced in the FDM to provide a better handling with a button controller.)
• You can restore the pogos by pressing Shift-r (appropriately when the aircraft has stopped completely).

Have fun!

Development status

Resources

Due to the lack of available data I'm using the flight manual of the original U-2. (See external links below.) I'm aware that this is somewhat a different aircraft but I believe it's still a valuable resource. Below I will use "FM" referring to it. Further I'm using images, drawings and flight reports.

JSBSim FDM

Based on a model created using aeromatic:

General

• adapted metrics, gears and structural positions, tanks, payload (stub) and gear control
• added custom throttle and fuel system

Open:

• cleanup is really needed, though currently I'm leaving things in as hints for further development

Aerodynamics

• polars generated for the main wing (and the hstab) using XFOIL and extended it by Javafoil and commonsense

Open:

• the DATCOM stuff needs to be redone w/ the information gained (from XFOIL and in general)
• further tuning of flight characteristics acc. to FM

Currently I'm using a "special" configuration that includes the horizontal tail for the pitching moment. Though I'm not convinced that this is best, so it might be subject to change.

Fuel system

A JSBSim fuel system is modelled. Only missing is the tank pressurization.

The fuel cross-transfer and dump system is fully functional but since the cockpit isn't finished there are no controls yet.

The respective properties are under /controls/fuel.

(For detailed information see Systems/fuel.xml.)

Estimations were made for the tank capacities.

Engine (GE-F118-101)

• changed tsfc
• manually extended the tables to higher altitudes
• bypassratio 2.0
• corrected milthrust to 17,000.0 lb

(See Engine/GE-F118-101.xml.)

Model

Exterior

• complete model w/ animated control surfaces, gear and textures
• added lights (supporting Rembrandt, evtl. some finetuning needed)

Open:

• correct the tail gear steering animation
• the texturing and UV-mapping should be reworked (to simplify livery generation)
• add more details (to the gears, inside of the gear-/speedbrake box)
• evtl. correct some positions (e.g. speedbrake)
• evtl. create a normal map
• evtl. add selectable configurations (nose, senior span/spear)
• livery support, add more liveries (e.g. NASA ER-2)

Cockpit

U-2S cockpit, current development state.

Currently I'm working on this. (See the image on the right.)

• reworked the interior w/o instruments
• added throttle and gearbox

Open:

• add instruments/controls (evtl. using the canvas system)
• texturing/UV-mapping
• add more details to the interior

Sound

The sound is taken from FG base package for now.

(Reworked 2013-12-17, see Sounds/U-2S-sounds.xml.)

Issues

• Currently there seems to be a bug in the ejection seat that prevents the pilot loading.

External links

• Lockheed U-2 English wikipedia article.
• https://www.cia.gov/library/center-for-the-study-of-intelligence/utility-flight-hb-1-Mar-1959.pdf The Flight Manual of the original U-2.
• http://www.clubhyper.com/reference/u2sdwa_1.htm Excellent closeup photo reference, intended for aircraft modellers.
• http://www.barryschiff.com/high_flight.htm A flight report.
• http://www.youtube.com/watch?v=1PmYItnlY5M James May in a U-2...