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851938

Aircraft Landing Dynamics Facility, A Unique Facility with New Capabilities

Pamela A. Davis, Sandy M. Stubbs,

and John A. Tanner NASA Langley Research Center

Aerospace Technology Conference & Exposition

Long Beach, California October 14-17, 1985

This paper i~ subject to revision. Statements and opinions ad­vanced in p"apers or discussion are the author's and are his responsibility , not SAE's ; however, the paper has been edited by SAL for uniform styling and format. Discussion will be printed with the paper if it is published in SAE Transactions. For permission to publish this paper in full or in part , contact the SAE Publica tions Division.

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ISSN0148-7191 COpyright © 1985 Society of Automotive Engineers,lnc.

This paper is subject to revision . Statements and opinions ad· vanced in papers or discussion are the author's and arc his responsibilit y, not SAL's ; however. the paper has been edited by SAL for unifo rm styling and format . Discussion will be printed with the paper if it is published in SAL Transaction s. lor permission to publish this paper in full or in part, contact the SAl:: Publications Division.

Persons wishing to submit papers to be considered for pre­sentation or publication through SAl:: should send the manu­script or a 300 word abstract of a proposed manuscript to : Secretary , Engineering Activity Board , SAL

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851938

Aircraft Landing Dynamics Facility, A Unique Facility with New Capabilities

ABSTRACT

The Aircraft Landing Dynamics Facility (ALDF), formerly called the Landing Loads Track, is described. The paper gives a historical overview of the original NASA Langley Research Center Landing Loads Track and discusses the unique features of this national test facility. Comparisions are made between the original track characteristics and the new capabilities of the Aircraft Landing Dynamics Facility following the recently completed facility update. Details of the new propulsion and arresting gear systems are presented along with the novel features of the new high-speed carriage. The data acquisi­tion system is described and the paper concludes with a review of future test programs.

THE LANGLEY RESEARCH CENTER Aircraft Landing Dynamics Facility , formerly known as the Landing Loads Track, is the only facility in the world capable of testing full size aircraft landing gear systems under closely controlled conditions on actual runway surfaces to simulate landing and take off operations of various aircraft. Testing at this facility is advantageous over flight testing for several reasons including safety, economy, parameter control, and versatility. Essentially any landing gear can be accommodated in the test carriage including those exhibiting new concepts and any runway surface and weather condition can be duplicated on the track. Research on slush drag, hydroplaning, tire braking, steering performance and runway grooving was accomplished at this facility. This paper presents a description of the Aircraft Landing Dynamics Facility and indicates how this facility has been upgraded to a higher speed capability. The main features of the facility update-the high pressure propulsion system, the arresting gear system, the high speed carriage and the track extension are described. The upgraded facility is scheduled to become operational during the summer of 1985.

Pamela A. Davis, Sandy M. Stubbs,

and John A. Tanner NASA Langley Research Center

DESCRIPTION OF OLD FACILITY, 1956-1982

A photograph of the old Landing Loads Track facility taken from the propulsion end looking towards the arresting gear is shown in figure 1. The compressor building houses a control room, a high pressure water pump, and an air compressor used to pressurize the three large air storage tanks to a pressure of approximately 21.7 MFa (3150 psi). The air flows from the three storage tanks, through a manifold, and a large goose neck shaped pipe up to the top of the "L" shaped vessel. The "L" vessel is filled with water using the high pressure water pump located in the compressor building.

Figure 1 - Landing Loads Track.

In front of the "L" vessel in figure 1 is the old test carriage. The test carriage is supported by steel rails that are 15.2 cm x 15.2 cm (6 in. x 6 in.) in cross section and extend the full length of the track. The test surface, shown in the center of the track, can be made of

0148 -7191/85/1014-1938$02_50 Copyright 1985 Society of Automotive Engineers, Inc_

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concrete, asphalt or other road bed type materials. Tests can be conducted on dry, damp or flooded runway surfaces, and a small section of runway can be covered with ice or ice slush. At the far end of the track is an arresting gear system that brings th~ carriage to a stop after the run is completed and the carriage building used for set up and calibration of various test articles.

A side view of the old test carriage in front of the old "L" vessel is shown in figure 2. The main features of the test carriage are the turning bucket, the drop carriage and the nose block. The turning bucket is located in the rear of the carriage and accepts the high pressure water jet from the quick opening valve located on the end of the "L" vessel. The.

o turning bucket turns the jet 180 which prdduces the force necessary to accelerate the carriage to the desired speed. The vertical rails lo~ cated in the center of the test carriage are the drop rails on which rides ·the drop carriage. The test article is attached to the drop car­riage to accomplish vertical impact or loading of the test specimen. On the front end of the carriage is a nose block which consists of five grooves to intercept five arresting gear cables which are stretched across the track at the arresting gear end of the track.

Figure 2 - Old test carriage.

The valve on the end of the old "L" vessel is a ten inch plug valve and external to that valve is a 17.8 cm (7 in.) diameter nozzle which directs the water flow into the turning bucket. At the maximum air pressure of 21.7 MPa (3150 psi) the speed of the water jet is 207 m/sec (680 ft/sec). A photograph of a typical catapult is shown in figure 3. The carriage will accelerate to its maximum speed before reaching the raised runway shown in the right foreground of the photograph. The raised runway in this figure is concrete onto which the test

851938

article will be lowered by the drop carriage. A typical test article is shown in the inset of figure 3. The inset shows the test wheel and tire mounted on a dynamometer used to accurately measure the forces exerted un the tire when the tire strikes the runway.

Figure 3 - Typical catapult.

Touchdown speeds for a wide range of com­mercial aircraft as a function of the year those aircraft were introduced into service are shown in figure 4. The Landing Loads Track facility became operational in 1956 and at that time, the track capability of 110 kts (1 knot equals 0.5 m/sec) was adequate to cover the landing speeds of commercial propeller driven aircraft. With the advent of the commercial jet aircraft, however, landing speed climbed to a different plateau. The plateau was even higher for military aircraft, not shown on figure 4. The

TYPICAL TOUCHDOWN

SPEED, KMJTS

250

200

150

100

50

UPGRADED FACILITY UPGRADED SPEED OPERATIONAL \ C APABILlTY ------r- -

o DC-4

o DC-3

OR IGINAL FACILITY OPERATIONAL

SPACE SHUTILE

1

(QJ YC-15 YC-14

o PROP o JET o PROP-JET

OL--~--~~~~~-~~-~~~~ 1930 1940 1950 1960 1970 1980 1990

YEAR I NTRODUCED INTO SERVI CE

Figure 4 - Touchdown speed chronology commercial transports.

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Space Shuttle lands at speeds between 175 and 220 kts. The updated facility is designed to enable testing at landing speeds up to 220 kts. The reason for upgrading the Aircraft Landing Dynamics Facility was to obtain the testing capability at landing speeds covering all cur­rent commercial and future aircraft.

RESEARCH REQUIREMENTS FOR UPDATED FACILITY

There were four basic requirements for the updated facility. The first was to increase the maximum test speed capability from 110 kts to 220 kts. A second requirement was to extend the track 183 m (600 ft) to obtain meaningful test times at these higher speeds. The third re- . quirement was to provide a larger open bay test carriage to be able to accommodate large landing gear test articles for test loads up to 222kN (50,000 lbs). The new carriage was designed to withstand much higher acceleration forces than the old carriage to facilitate the higher speed capabi.lity. The fourth requirement was to design-in the flexibility of utilizing the existing test carriage of the old facility. By meeting these requirements, NASA will have a unique national facility with increased speed capability to study current military and commer­cial aircraft landing problems, and to investigate landing systems of future aircraft including the Space Shuttle Orbiter.

DESCRIPTION OF MAJOR HARDWARE FOR UPDATED FACILITY, 1985 •••

A sketch of the new facility is shown in figure 5. On the left side of the figure is the "L" vessel and air piping system. The three existing air storage bottles were used and a pew 122 cm (48 in.) diameter air pipe was fabricated to carry air from the air bottles to the top of the new "L" vessel. The new "L" vessel -holds 98.4 ki (26,000 gals) of water in contrast to the 37.8 kt (10,000 gals) of the old "L" vessel. A quick opening shutter valve is mounted on the end of the new "L" vessel to control the water jet which catapults the carriage to the desired speed. The new carriage, with the large open bay, is a major addition. Another major addi­tion is the new arresting gear system. It consists of five arresting gear units on each side of the track connected with five arresting gear cables that intercept the nose block of the carriage and bring it to a stop. The carriage building (Building 1261) for experiment prepara­tion and calibration has been relocated at the end of the 183 m (600 ft) track extension shown in cross section. A new transfer system, shown in an auxiliary view, and an addition to the shop area behind Building 1262 has been built to facilitate a two carriage operation.

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TRACK EXTENSION

Figure 5 - Aircraft Landing Dynamics Facility.

PROPULSION SYSTEM - A photograph of the upgraded facility from the propulsion end is shown in figure 6. On the end of the "L" vessel is a fast acting shutter valve which controls the water jet. In front of the shutter valve is a flow straightener that takes the water during initial valve opening that would be deflected downward by the shutter and redirects it into the turning bucket at the rear of the carriage. The foundation for the "L" vessel is a slab of concrete that is 3.7 m (12 ft) thick and weighs approximately 31.7 MN (7 million lbs). A sketch

Figure 6 - Aircraft Landing Dynamics Facility.

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of the high speed shutter valve that i s mounted on the end of the "L" vessel i s shown in figure 7 . A s pherical valve body was chosen t o contain t he high pressure water . A saf ety shutter , i nternal t o the val ve body, is used to obt ain a wat er t i ght s eal be t ween runs. Dur ing a t ypical catapul t operat ion, the safet y shut t er opens t oward the top of the valve body and then the high speed shutter, which is connected by linkages to the hydraulic actuator, is moved in 0.4 seconds to an open position, held open for the dwell time necessary to obtain the desired carriage speed, and then returned to the closed position in 0.3 seconds. The internal nozzie shown in figure 7 provides a smooth contour from the end of the "L" vessel and forms a water Jet 45.S cm (IS in.) in diameter. The nozzle is centrally positioned within th~ 50.S cm (2ti , in.) diameter valve body opening . At a maximum pressure of 21.7 MPa (3150 psi), the 45 .S cm, (lS in.) jet will produce a thrust of approximately S MN (1. S million lbs) on the new carriage . With ' a carriage weight of approximately 4S0 kN (108,000 lbs) this thrust creates a peak ac- . celeration of approximately 17 g's.

Shutter Closed Shutter Open

Figure 7 - Propulsion control valve.

Fi gur e S i s a photograph of the high speed shutter valve during final assembly. Noted in t he fi gure is the high speed s hutter and the linkage mechanism for opening and closing the shutter. The hydraulics and nitrogen supply system controls are shown near the top of the valve. These s ystems control the pressure and f l ow of oil in the actuator which opens and shuts the high speed shutter. These systems also control the flow of oil to the safety shutter and several safety pins around the

851938

' Figur e S - High speed s hut ter valve .

valve. Figure 9 shows the "L" vessel, the goose neck pipe and the new valve sitting beside the "L" vessel before i nstallation. The internal stainless steel nozzle can be seen protruding from the end of the "L" vessel. The valve slips over the nozzle and is bolted to the end of the

Figure 9 - Propulsion system.

"L" vessel. Figure 10 is a photograph of the flow straightener at the end of the high speed shutter valve.

851938

Figure 10 - Flow s~raightener.

CARRIAGE - A photograph of the new carriage is shown in figure 11. The ·carriage is con­structed of tube memebers with a central open bay 12.2 m (40 ft) long and 6.1 m (20 ft) wide to enable mounting a wide variety of test ar­ticle shapes and sizes. The aft end of the carriage contains the large turning bucket which is approximately 3 m (10 ft) high. At the front end of the carriage is the nose block that intercepts the five arresting cables that stretch across the track. In the center of the carriage is the drop carriage to which the test article is attached. The drop carriage rides on four vertical rails and two hydraulic lift cylinders are used to raise and lower the test

Figure 11 - New test carriage.

article and to apply vertical loads to the test article as needed. Also noted in figure 11, on the near side of the carriage, is the hydraulic system for positioning the drop carriage, apply­ing loads, obtaining free fall at speeds up to 6.1 m/sec (20 ft/sec), and applying wing lift to simulate an aircraft touchdown. Data from the test article are r outed through an instrumenta­tion box on the l eft side of the carriage and transmitted to a recording station at the propulsion end of the facility. Also shown in the photograph are outriggers on each corner of the carriage with rollers that run under the hold down rails shown in figure 12. The hold down rollers and rails are designed to hold the carriage on the main rails during the catapult stroke when upward force vectors might cause the carriage to be lifted off the rails.

Figure 12 - Propulsion end of ALDF track.

ARRESTMENT SYSTEM - A sketch of the arrest­ment system is shown in figure 13. A massive concrete foundation is located on either side of the track with five arresting engines mounted on each foundation. A close up view of an arrest-

Figure 13 - Arresting gear system.

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ing gear engine is shown in figure 14. Noted in the figure is a tub which holds a mixture of water and antifreeze. The tubs (5 on each side of the track) have stator vanes inside (not shown) on the bottom and top surfaces. Between the top and bottom stator vanes are rotor vanes attached to the rotating shaft that protrude ' through the top of the tub and to which is attached a spool which contains nylon tape that is approximately 20.3 cm (8 in.) wide and about 1 cm (3/8 in.) thick. The tape is connected to a cable that goes across the track and picks up the nose block of the moving carriage during arrestment . As the nose block pulls the tape from the spool, the rotor vanes churn the water in the tub. This churning action dissipates. the kinetic energy of the carriage. The new arrest­i ng system was designed to stop the carriage in approximately 152 m (500 ft) even if only three of t he five sets of engines are operating.

Figure 14 - Arresting gear engine .

A photograph of the complete arresting gear system is shown in figure 15. The new carriage is shown approximately half way down the track and the propulsion system is shown at the far end of the track. The new 183 m (600 ft) track extension, shown in the foreground, was not completed when this picture was taken.

Figure 15 - Arresting gear end of ALDF track.

Figure 16 is a photograph of a maximum speed shot (220 kts) of the new high speed

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Figure 16 - New carriage during maximum speed catapult, July 3, 1985.

carriage. Figure 17 is a carpet plot of the carriage speed as a function of propulsion valve dwell time, "L" vessel pressure, and water

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CARR IAGE SPEED,

KTS

240 WATER USAGE. kl (gall

0. 4

32. 2 ( 8500)

0. 8

20.7 (3000)

DWELL TIME. SEC

L VESSEL PRE SSURE. MPa (P SI)

10. 3 (15001

J.2

6. 9 (1000) .

3. 4· (5OD)

1. 6

Figure 17 - Carriage speed as a function of dwell time.

usage. Table 1 summarizes the old and updated capabilities of the Aircraft Landing Dynamics Facility.

Max. Test Speed. kes

Length s , m ( ft) Overall Track

Test Dura tion , Sec:

Max. Vertical Loading. kN (lbs )

Catapult Ma x . Accel, g units Ma x. Force, MN (lbs) Stroke, m (ft) Pressure , kPa (PSI) Sozzle Diameter. em (in.) H20 Consumption, k~ (gal)

(Max. Speed Test)

Carriage Ope n Bay S ize. m eft) Vertical Speed. o n Test Article , m/sec (ft/sec) Vertical Load on Test Ar ticle. kN (Ibs)

*With grovth capability of 1,45 ( lOOk)

110

670 (2200) 366 (1 200)

7@IOOkts

222 (SDk)

).)

1 . 6 (3S0k) 122 (loOO) 21 (JOOD) 18 (7.16) 11 (JOOO)

] x 5 (lOxIS) 0-6 (O~20) 0- 200 (O-4 5k)

Upda t ed Capab1l1ty

220

8S] (2800) 549 (1800)

\l@ I OO k es 5@220kts

222 (SDk ) @200 kes >222 (SDk) @ lower V

17- 18 8 ( 1. 8k) 122 (400) 21.7 (3200) 46 (18) 38 (1 0k )

61': 12 (20x4 0) 0- 6 (0- 20) 0 - 222* (o-SOk) *

Table 1 - Aircraft Landing Dynamics Facility Capabilities Comparison

RESEARCH PROGRAMS

The first research programs performed at the updated facility will investigate Shuttle Orbiter main and nose gear tire spin up wear characteristics and cornering force characteris­tics at high speeds. Another test program will collect data on the frictional characteristics of radial and H-type aircraft tires for com­parison with conventional bias ply tires. This radial and H-type tire program will be a joint effort between NASA, the FAA, the Air Force, the Society of Automotive Engineers, and the U.S. tire industry. A third program will be a joint NASA-FAA runway surface traction program study­ing the effects of different runway surface textures and various runway grooving patterns on the stopping and steering characteristics of aircraft tires. A fourth program will support a National Tire Modeling Program, that is a joint effort structured between NASA, and the U.S. tire industry to generate analytical models for the design of new types of tires. Research from the ALDF facility will be used to verify analytical work currently underway.

CONCLUDING REMARKS

A description of the original NASA Langley Research Center Landing Loads Track facility and its upgraded facility referred to as the Aircraft Landing Dynamics Facility (ALDF) is presented. Operational characteristics of the ALDF propulsion system, high speed test car­riage, and arresting gear system are reviewed. The upgraded facility is scheduled to become operational during the summer of 1985.

As a result of the facility upgrade, the maximum speed capability of the Aircraft Landing Dynamics Facility has been doubled. The facility can also handle heavier and more bulky test articles than it could in the past. With this upgraded capability, the Aircraft Landing Dynamics Facility is now equipped to conduct research on present and future landing gear systems under realistic operational conditions.

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