V I. 3, N .4

L NGI UDI AL TABILIT ... PAG 1

~\ Terence B. Donahue, Editor

CONTENTS

January-February 1957 Vol. 3, No.4

COVER PICTURE Luxury andservice, traditional with Trans­portes Aereos Portugueses, willbe provided air travelersbetween Europe, Africa andSouth America by TAP's newlyacquired fleet of 1049G SuperConstellations. Two of theirthree Super Constellations flewin company across the Atlanticin a unique double-deliveryflight to Lisbon. The new,scarlet, silver and white,turbocompound-powered air­liners constitute Portugal's mostsignificant advance in civilaviation.

LONGITUDINAL STABILITY

TRADE TIPS

LUBRICATION OF FUEL TANK ACCESS PANEL SEALS

CALIPER RULE MEASURES TIRE DIAMETER

O-RING PACKING LEAKAGE .

DUAL D-C GROUND POWER SYSTEM

DRAIN HOLES IN AILERON CONTROL ACCESS DOORS

COMMERCIAL SERVICE BULLETINS PENDING

TECHNICAL PUBLICATIONS FOR CONSTELLATION AIRCRAFT

LOCKHEED AIRCRAFT CORPORATION

1

9

9

10

16

19

19

20

The Lockheed Field Service Digest is published bimonthly by Lockheed Aircraft Corporation, CaliforniaDivision, Burbank, California. No material is officially approved by the CAA, CAB, or any of the militaryservices unless specifically noted. Airline and military personnel are advised that direct use of the informa­tion in this publication may be restricted by directives in their organizations. Obtain written permissionfrom Lockheed Aircraft Corporotion before republishing any of the material contained herein. This require­ment is mandatory to ensure thot all material republished will conform to the latest information and changes.The following marks are registered and owned by Lockheed Aircroft Corporation: Lockheed, Constellation,Lodestar, and Speedpak. Address all communications to Lockheed Aircraft Corporation, Burbank, California;Attention, Field Service and Troining Division.

COPYRIGHT 1957 BY LOCKHEED AIRCRAFT CORPORATION, BURBANK, CALIFORNIA

itudinal..&.::B::I::I:.::I:-r~

by F. J. Fitzgerald, Constellation assistant pro;ect engineer

1049 SERIES For some time Lockheed engineershave been investigating ways to improve the longi­tudinal stability in certain aircraft in the Super Con­stellation series. In recent months the results of thisengineering effort have been subjected to stringentlaboratory and flight tests which confirm our beliefthat our objectives have been reached. The newdevelopments now available in elevator control sys­tems will afford the desired longitudinal stabilitycharacteristics under the most exacting service con­ditions.

In this article we will relate the background of aflight stability problem known as pitch oscillation,which has generally occurred during cruise flight onautopilot. We will then describe the improvementsin the elevator booster mechanisms and inspectionprocedures which have evolved from our investiga­tions of the problem, and how they can be applied toin-service aircraft if required.

PITCH OSCILLATIONPitch oscillation may be described as the tendency

of an airplane to fly an undulating flight path, inwhich the airplane's attitude alternates between noseup and nose down over a range of a few degrees. Thisis not characteristic of most Super Constellations, butsome may exhibit mild oscillation when trimmed forlevel flight. The amplitude and frequency of theoscillation may be different in each affected aircraft.Only a few airplanes show pitch oscillation to a

degree which will not meet the flight standards of theoperating airline at all times.CAUSES The direct cause of pitch oscillation is sim­ply rough or excessive movement of the elevators.The indirect or underlying cause may be one unde­sirable condition, or a combination of such conditions,in the automatic pilot system and the elevator boostermechanism. If an airplane contains any undesirableconditions in either of these systems, it may not main­tain its longitudinal stability within acceptable limits.

LONGITUDINAL STABILITY Longitudinal stability isthe ability of an aircraft to maintain a level flightattitude. To do this for great distances and througha variety of weather conditions, the proper function­ing of all elements of the control system is essential.Every part in each cable system, linkage, hydraulicmechanism, and electrical or electronic circuit mustbe properly adjusted and capable of operating as itwas designed to do if the desired end result-straightand level flight-is to be achieved.

The importance of proper component adjustmentis illustrated by the following example. Low tensionin the autopilot elevator servo slave cables contrib­uted to pitch oscillation in some cases when aircraftwere trimmed for automatically controlled levelflight. Several operators reported difficulty in main­taining the prescribed rigging tension of 75 pounds( -+- 10 pounds) in these slave cables, which connectthe autopilot elevator servo unit to the elevator con­trol system. To offset the tendency of these cables to

1

loosen in service, Lockheed recommended that alloperators adopt the following corrective procedure:

"Rig the servo cables to proper tension, thentighten the turnbarrel one additional quarter-turn,safety wire, and back off the turnbarrel within thelimits of the safety wire."

A number of in-service aircraft which had ten­dencies toward pitch oscillation were cured byperiodic maintenance of the servo slave cables inaccordance with this rigging procedure. This informa­tion is now on a placard' LAC PIN 474131, which isinstalled on the aft face of the fuselage bulkhead atstation 1189.17 on production aircraft (see Figure 1) .The placard installation is available for retrofittingon commercial aircraft under Service Bulletin1049/SB-2624, and on U. S. Navy aircraft underR7VjWV Aircraft Service Change 366.

REPORTS FROM OPERATORSOnly a few cases of pitch oscillation were reported

in 1954. At first these were thought to be isolatedcases of differences in flight crew techniques or lackof familiarity with certain maintenance procedures.When the number of reports on this subject increased,we found that we faced a puzzling problem not unlikea ball of string with several loose ends. There wereseveral places where we could start to resolve theproblem, because the reported symptoms of pitchoscillation had a challenging variety. For instance,some of the trouble reports described a repeated pat­tern in the flight characteristics of certain airplanes.These airplanes operated at cruising altitude for pro­longed periods in low ambient air temperatures. Aftertwo or three hours of cruising with good elevator sys­tem control and level flight path, these aircraft wouldstart a series of gradually increasing pitch oscillations.

In other cases, the aircraft would not maintainlevel cruising flight while operating on automaticpilot with the altitude control engaged. Also, therewere aircraft which would oscillate when flown man­ually with the elevator boosters turned on and theautopilot turned off. To compound the difficulty infinding the true sources of trouble, there were a num­ber of cases in which a given aircraft would vary inits oscillating tendencies from flight to flight as aresult of changes in gross loads, operating conditions,and flight crew techniques.

TESTING PROGRAMSFrom the start of the full-scale investigations into

the causes of pitch oscillation, it was apparent thatthere would be no quick and easy fix for the problem.The reports from operators and our observations andflight tests made it clear that no single part or singlesystem was the chronic source of trouble. We foundit necessary to make statistical studies, symmetry and

2

Figure 1 Rigging Instructions Placard

alignment checks on aircraft, and laboratory tests onelevator control systems and components. The com­prehensive effort initiated by our Engineering depart­ment engaged the skills of many of our people formore than two years. Our customers were most help­ful in performing service tests of modified equipmentand in exchanging information on the test results.

The testing program at Lockheed was aimed at twoseparate but complementary goals. We tested theexisting elevator control systems to find any possiblesources of trouble which could contribute to rough orexcessive elevator movement. We also tested newdevelopments which might improve the elevator con­trol systems in our production aircraft, and whichmight be suitable for retrofitting to airplanes pre­viously delivered.

The program was divided into two main categories:autopilot tests and booster system tests.

AUTOPILOT TESTS Since the majority of the earlyreports described pitch oscillation while the affectedaircraft were cruising under autopilot altitude control,the autopilot system was the subject of our first inves­tigations. The most successful development testedwas a resistance-capacitance (R-C) network modi­fication to the autopilot amplifier.

The R-C network consists of a small amplifier anda resistance-capacitance l'ow pass filter combined intoa compact unit. This small unit is connected in theelevator pitch channel of the autopilot amplifier. Asignal derived from the altitude sensor feedbacktransformer in the elevator pitch channel will buildup in the R-C unit and act to oppose steady altitude

sensor signals. .on the other hand, the R-C unit willnot oppose transient attitude-error pitch gyro signals.Therefore, these signals will result in appropriatecorrective action by the elevator servo unit. The timeconstant of the R-C network is adjusted so that theautopilot will damp the objectionable low frequencyaltitude oscillations of the airplane.

The results of our testing to date indicate that theR-C network augments the refined elevator controlprovided by the booster system improvementsdescribed later in the article. For this reason we haveincorporated the R-C network in our commercial pro­duction airplanes starting with Model 1049G LACSerial 4650.

The R-C modification has a disadvantage, how­ever. Because its characteristic is to oppose steadyaltitude sensor signals, added loss of airplane altitudein turns is encountered when the aircraft is beingflown on autopilot with altitude control engaged. Ameans of compensating for this loss of altitude isbeing developed, but it is not yet available for test.Consequently, we do not recommend retrofitting theR-C network until this problem is resolved and muTeoperational service information is available to justifya retrofit program. Operators of Super Constellationsequipped with the Eclipse-Pioneer PB-lO or PB-lOAautopilot will be informed as further autopilot systemimprovements become available.

BOOSTER SYSTEM TESTS During the early tests onautopilot components, we received additional reportsindicating that in some cases the autopilot pitch oscil­lations continued after the autopilot was turned off.Our testing program confirmed these reports andwe found that some of the trouble, especially inModel 1049G aircraft, was traceable to the elevatorpower booster system.

The investigation of the elevator booster systemhas resulted in the design and production of severalimprovements to the booster mechanism which arediscussed in the next section of this article. Followingthat, we will examine a new procedure for checkingclearances and alignment of certain critical points inthe elevator control system. These developments havebeen proved by careful laboratory and service tests.We feel that their adoption will afford much im­provement in elevator control response and cruisingflight characteristics on those Super Constellationswhere longitudinal stability is unsatisfactory.

ELEVATOR BOOSTER SYSTEMIMPROVEMENTS

Our investigations into the causes of pitch oscilla­tion included comprehensive tests of the elevatorbooster cylinder. We wanted to reduce the time

required for the piston to respond when hydraulicpressure was applied. The following modification~ tothe booster cylinder are the result of our testmgprogram.

NEW TEFLON PISTON SEALING RINGS The originaldesign of the booster cylinder employed a fl~at~ng

O-ring seal on the piston to obtain the low fnctloncharacteristics required for rapid response when theelevator cable system initiated elevator movement.Unfortunately, the advantages of low frictioninherent in this design were partially offset by a con­siderable amount of oil leakage across the piston seal.The leakage persisted up to the relatively high pres­sures required for the O-ring to seal. Sluggish controlresponse could result from this condition since con­siderable hydraulic pressure build-up in the cylinderwas necessary before the O-ring sealed and the pistonmoved.

To control internal leakage across the piston seal,we removed the floating O-ring and installed Teflonpiston sealing rings, backed up by a spring as shownin Detail A of Figure 2. The new seals greatly reduceleakage without increasing friction and do not re­quire a hydraulic pressure build-up for sealing. Thisimproves the ability of the cylinder to move the ele­vators in closer compliance with the demands of thepilot or autopilot.

NEW TEFLON BACK-UP RINGS In laboratory teststhe amount of friction drag produced by standardO-ring seals with leather back-up rings was ~ompared

to the drag of O-rings backed up by Teflon rmgs. TheTeflon ring proved superior to leather in resistanceto deformation, did not separate into individual fiberslike leather, and because of the lower coefficient offriction of Teflon, provided a reduction in frictionaldrag. For these reasons, the Teflon back-up ring hasbeen adopted for both the piston rod dynamic sea~s

and the cylinder static seals. Both of these new modI­fications are illustrated in Figure 2.

NEW CYLINDER O-RING BUSHINGS The new bush­ings are installed as a result of the adoption of Teflonback-up rings. The reduced friction of the Teflonback-up rings allows a greater amount of squeeze tobe placed upon the O-ring without danger of crack­ing or nibbling the O-ring when it rolls in the grooveof the bushing. The new bushings provide grooveswhich are smaller in cross section and which applygreater squeeze to the O-rings. This reduces oil leak­age at the piston rod dynamic seals.

NEW PISTON ROD SCRAPER RINGS Teflon scraperrings are now installed in the existing recesses in thecylinder bushings. The low drag of the Teflon ringmakes possible this added protection against contam-

3

ination of the booster system by dust, water, paint,and washing solvents.

The modified elevator booster cylinder bears LACPIN 668258-1. All of the improvements necessary tomodify in-service and spare cylinders to this configu­ration, as well as similar improvements for the rudderbooster cylinder, will be made available for our com­mercial customers in Service Bulletin 1049/SB-2523,s revised December 28, 1956. When this revision to

1049/SB-2523 is accomplished on 1049Basic LACSerial Numbers 4001 through 4024, or on sparebooster cylinders for these aircraft, Service Bulletin1049/SB-2097 must also be accomplished. ServiceBulletin 1049/SB-2097 contains instructions forwidening the a-ring groove of the booster cylinderpiston. The Teflon piston rings are designed to fitthis wider groove. Revised Time Compliance T.O.1C-121-533 or R7V/WV Aircraft Service Change266A will apply to military airplanes.

Commercial 1049 Series aircraft received theseimprovements at the factory beginning with LACModels and Serials: 1049G 4647, 4650 and subse­quent; 1049H 4801 and subsequent. Installation ofthe improvements on military aircraft in productionbegan at LAC Model 1049A 4464 and subsequent.NEW HIGH-GAIN, LINEAR-FLOW CONTROL VALVEA new elevator booster control valve LAC PIN668259-1, has been designed and produced. Wedecided to design a new valve after completing lab-

oratory tests in which the performance of the standardelevator booster control valve was compared to thatof a modified valve having improved flow meteringcharacteristics. Our tests showed considerable im­provement in response rate (the time required foraction) and increment control (the accuracy ofpositioning) in the entire booster mechanism whenthe modified valve was used. Our earlier experiencewith rework programs on similar units convinced usthat attempts to modify existing valves on in-serviceaircraft and spares stock would prove impractical sono valve modification program is planned.

The new valve is externally similar to, and phys­ically interchangeable with, the earlier unit, exceptfor installation and rigging procedures. The newvalve supplies greater oil flow to the elevator boostercylinder at very small displacements of the valvespool from the neutral position. This characteristicis referred to as high gain. The new valve also pro­vides approximately equal increases in oil flow forequal increases in spool displacement. This charac­teristic is referred to as linear flow. These flow char­acteristics are compared to those of the existing valvein Figure 3.

This illustration shows that a spool displacementof .030 in. from neutral in the existing valve resultsin a fluid flow of approximately one gallon per min­ute, which is little more than leakage flow. This is

TEFLON BACK-UP RING(STATIC SEAL)

NEW CYLINDER BUSHING

TEFLON BACK-UP RING(DYNAMIC SEAL)

~Teflon rings in op­posite end of cylin­der are identical tothose identified

EXPANDERSPRING--~

TEFLON SCRAPER RING

Figure 2 Cutaway of Modified Elevator Booster Cylinder

4

Figure 3 Comparison of Flow Rates-Existing Elevator Booster ControlValve Versus New High.Gain Valve

not enough flow to provide the rapid pressure build­up needed to move the piston in immediate responseto autopilot or pilot demands. The low rate of flowis especially noticeable when small amounts of boosterand elevator movement are required.

On the new high-gain valve, a spool displacement .of .030 in. from neutral results in oil flow at the rateof approximately 3.25 gallons per minute, also shownin Figure 3. The increase in volume of fluid whichmay be passed by the new valve at any given spooldisplacement when compared to the existing valve,affords much tighter control of elevator movement.Thus, quicker and smoother corrections to changes inairplane attitude are achieved.

NEW ELEVATOR FEEL BOLT SLEEVES The sensitivityof the new booster control valve makes it possible toreduce the range in which the booster mechanismoperates on low boost ratio. We reduced this range oflow ratio booster action by removing the existing ele­vator feel bolt sleeves LAC PIN 297456, and replac­ing them with new sleeves LAC PIN 726995-1, whichhave a larger outside diameter. Figure 4 shows howthe larger OD of the new sleeves results in reducedclearance between the sleeves and the edge of theslotted hole in the debooster floating (pilot) lever.Closing up these clearances allows earlier applicationof high ratio booster action. This results in more vig­orous elevator movements when required to correctlarge or rapid changes in airplane attitude. LAC Serv­ice Bulletin 10491SB-2525 will provide both therevised feel bolt sleeves and the new high-gain, linear­flow valve for retrofitting to commercial Super Con­stellations in service. These improvements have beeninstalled on aircraft at the factory starting with com­mercial Models 1049G LAC Serial 4647, 4650 andsubsequent; 1049H 4801 and subsequent; and mili­tary 1049A LAC Serial 4464. When 10491SB-2525is retrofitted to in-service commercial aircraft, the ele­vator booster cylinder must be modified concurrentlyin accordance with the December 28, 1956 revision to

1049ISB-2523, unless this has been previously accom­plished. The autopilot amplifiers used in these air­planes must also be modified by installing an altitudesensitivity adjustment potentiometer in the altitudecontrol. Eclipse-Pioneer has issued their Service Bul­letin 300A-25 to accomplish this change on PB-lOautopilot amplifiers. A parallel installatidn forPB-lOA autopilot amplifiers is supplied by Eclipse­Pioneer Service Bulletin 730-3.

ALIGNMENT AND TOLERANCE INSPECTIONOF ELEVATOR BOOSTER MECHANISMThe benefits of the improvements previously pre­

sented may not be realized unless all of the functionaland structural parts in the elevator booster installationare aligned and adjusted to afford proper freedom ofmovement at every operating point, but without exces­sive clearance. We consider it mandatory for eachoperator to conduct a thorough inspection of certaincritical points in the booster mechanism and its attach­ments on those airplanes which exhibit pitch oscilla­tion. Inspection points requiring illustration areshown in Figures 5, 6, and 7.

Commercial operators may obtain parts kits andfull instructions for the accomplishment of thisinspection and any necessary corrective action in LACService Bulletin 1049ISB-2941. This service bulletinapplies to the following LAC Models and Serials:1049C, E, and G 4501 through 4667; 1049D 4163through 4166; and 1049H 4801 through 4804. How­ever, general inspection procedures are presentedhere for the convenience of those operators who havenot yet established their need for these service bulle-

NEW SLEEVErEXISTING CLEARANCE

T

EXISTING SLEEVE VIEW SLOTTED HOLE

Figure 4 Reduced Clearance Provided by New Feel Bolt Sleeves

5

SIDE VIEW OF ELEVATORBOOSTER MECHANISM SHOWINGLOCATIONS OF SECTIONS A-A,B-B, AND C-c.

~All dimensions shownare in inches. Multiplyby 25.40 to obtainmillimeler equivalent.

6 Figure 5 Points to be Checked i

SECTION A-AINSPECTION STEP 2 AND 3

POWER LEVER ARMASSEMBLY (PIN 315863-3L)

FEEL LEVERASSEMBLY (PIN 315803)

~~__- PISTON ROD ASSEMBLY(PIN 322644)

ELEVATOR BOOSTER FRAMEBEAM (PIN 279188)

ISECTION C-C

INSPECTION STEP S

tins. These inspection procedures are given in step­by-step sequence below. This sequence must befollowed for the best results in operation and greatesteconomy in man-hours expended.

1. Check for concentricity of the elevator feel boltsleeves LAC PIN 297456. The feel bolt sleevesshould be removed from the feel bolt and placed ona mandrel or close-tolerance centering pin which willnot allow radial mov~ment. A dial gage should beused to determine that each sleeve is concentric within.002 in. total indicated reading on the larger outsidediameter. The new sleeves provided by 1049/SB-2525will assure concentricity, but can be used only with thenew high-gain booster control valve.

Before reinstalling the sleeves on the feel bolt,check the flat parallel surfaces inside the slotted holesof the debooster floating lever assembly for paintaccumulation or roughness due to wear. These sur­faces must be clean, smooth, and parallel. If any out­of-round condition exists on the sleeves, even thougheach sleeve is within tolet'ance, the high point shouldbe marked. The sleeves should then be installed onthe feel bolt with the high point on each sleeve in thesame respective position. For instance, if one sleeve isinstalled with the high point facing forward then theopposite sleeve should also be installed with the highpoint facing forward. The nut should then be tight­ened to lock the sleeves in this position.

2. Check the slotted holes in the floating leverassembly PIN 290864L and 290864R for location in acommon plane. Section A-A of Figure 5 illustratesthe proper method of checking these holes and theprocedure is as follows:

Move the 290864R floating lever assemblydown until the Rat surface on the upper sideof its slotted hole iust contacts the OD of thefeel bolt sleeve, as illustrated by Point A ofSection A-A in Figure 5. Holding the leverin this position, use a feeler gage to measurethe clearance, if any, as shown at Point S,where the opposite sleeve meets the upperside of its slotted hole. The clearance mustnot exceed .004 in.

3. Check the clearance of the elevator control valvelinkage. Section A-A of Figure 5 shows two points,C and D, at which the clearance should be checkedbetween the flanges of the arm assembly PIN 315863and the two vertical swinging links PIN 290789 andPIN 290790. The clearance at these points must notbe less than .020 in.

4. Check for side load at the elevator boostercylinder rod end. See Figure 5, Section B-B. The rodend of the cylinder piston rod should be disconnectedfrom the feel lever by removing the bolt and anywashers which may be installed. The rod end must befree of any side loading from the feel lever through-

out the entire stroke of the piston rod. The rod enddoes not need to be centered in the slot of the feellever so long as there is no side load. Washers maybe installed on the bolt as required to fill the gap be­tween the rod end and the feel lever. The bolt shouldbe tightened to a torque value of 0 to 10 inch-pounds,and be free to rotate with finger pressure, but withoutend play.

5. Check the lower attachment points of the boostermechanism. The elevator booster frame beamPIN 279188 attaches at its lower end to two bulk­head tees PIN 278444-20 and PIN 278444-21. Across section of this attachment point is shown inFigure 5, Section e-c. The bolts should be removedone at a time from each lower attachment point andthe holes in both tees ~nd beam checked for align­ment by reinstalling the bolts by hand. Each boltmust be passed through the outer and inner holes inthe beam and the hole in the bulkhead tee withoutusing force or without springing the beam to obtainalignment. Each of the six holes must have an insidediameter between .3119 in. and .3134 in.

6. Check for free motion of the elevator boostercontrol valve linkage. Figure 6 shows the propermethod of checking this parallelogram linkage forfree motion at the booster control valve. Remove thebolt which connects the control valve rod to the hori­zontal link, and swing the parallelogram linkage foreand aft so that the forward end of the horizontal linkpasses back and forth through the slot in the upper

BOOSTER CONTROl VAlVE(PIN 667775)

figure 6 Checking for free Motion ofControl VaI'e Linkage (Inspection Step 6)

7

AITACHINGSHAFT

SEalOM A-AUse equally distributed1356-13E shims here toobtoin bearing fit betweenmaximum of .002 in. preloadand maximum .007 in. endplay.

ELEVATOR COUNTERWEIGHTBELLCRANK ASSEM8LY

CONTROL HORN

Use AN960-1016L washers asrequired to allow feltseals to touch control homlightly without binding.

AITACHING SHAFTNUT (AN 310·10)Torque 500-1000inch-pounds both ends.

ELEVATOR COUNTERWEIGHTPUSHROD

ELEVATOR TORQUETUBE

ELEVATOR COUNTERWEIGHTCONTROL HORN

Figure 7 Checking for Proper Bearing Fit at Both Ends of Counterweight Pushrod !Inspection Step 71

end of the valve rod. There must be no binding orinterference at any extension of the valve rod.

7. Check for correct bearing fit at the attachmentshafts which secure the elevator counterweight push­rod. The elevator counterweight pushrod PIN 284123attaches at its forward end to the counterweight bell­crank and at its aft end to the elevator counterweightcontrol horn on the right-hand elevator torque tube.The bearing installations at both of these points mustbe checked for preload or end play and the nuts onthe shafts for proper torque.

Section A-A of Figure 7 illustrates the proper useof shims equally distributed as required to allowtightening the nuts on the counterweight pushrodattaching shaft to a torque of 500 to 1000 inch­pounds. With this torque on the nuts established, thebearing fit should fall within a range of .002 in. max­imum preload to .007 in. maximum end play. Washersshould be used as required to allow the felt seals totouch lightly and without binding on the surface ofthe control horn or bellcrank. The felt seals shouldbe lubricated periodically with general purpose lubri­cating oil Spec MIL-L-7870.

8

SERVICE BULLETIN SUMMARYA high degree of longitudinal stability has been

attained wherever the improvements and inspectionprocedures described above have been adopted onSuper Constellations. Service tests under many dif­ferent flight conditions rlave indicated that thesemodifications reduce operating and maintenanceexpense, and provide greater passenger and crewcomfort.

The improved components developed by the testingprograms and the service bulletins discussed in thisarticle are summarized below.

• Service Bulletin 1049/SB-2523 for commercial air­planes, and R7VjWV Aircraft Service Change266A or Time Compliance T.O. 1C-121-533 formilitary airplanes, concern modifications to therudder and elevator booster cylinders. The partskits for the elevator cylinder will include new cyl­inder bushings and Teflon rings.

• Service Bulletin 1049/SB-2 52 5 for commercialoperators will include the new high-gain boostercontrol valve and new elevator feel bolt sleeves.

• Service Bulletin 1049/SB-2941 contains fullinstructions and parts as required to accomplish theinspection and alignment of the elevator boostermechanism on commercial airplanes.

• The changes described for commercial customersby Service Bulletins 1049/SB-2525 and 1049/SB-

2941 will be proposed to the Air Force and Navyby ECP LH-R7V;WV/C121-5326.

• Service Bulletins 1049/SB-2525, 1049/SB-2941 andthe revision to 1049/SB-2523 will be distributedto all affected commercial operators as soon as theyare available. .. ..

3/16-INCH BOLTSAND NUTS(4 eoch required)

1/2-TO 5/8-INCH THICKUTILITY GRADE PLYWOOD(3 inches wide x 57 inches long)

9

TWA personnel have informed us that they use alarge portable wooden caliper rule to measure thediameter of main gear tires more easily and moreaccurately. The construction features of this caliperrule are illustrated for operators who may be inter­ested in such a device. A ..

To keep seals from sticking and tearing, it isrecommended that the seals in the panels be coatedsparingly with Lubriplate No. 130AA. Use cautionto apply the lubricant only to the seal, as this com­pound will also prevent tank repair sealant fromadhering. However, Lubriplate No. 130AA is easierto see and remove than DC-4, thus minimizing thepossibility of tank repair sealant failing to adhereto the dome nuts or structural joints around theaccess panel area. .. A

aT

_ ___--+10 0 t3.

00

111-0--------------43.00

!~8;~~~e:)RAZIER HEAD RIVETS .050 ALUMINUM GUIDE .050 ALUMINUM PLATE u8.00Rivet to plote on both sides of wood. Form guide oruse spacers to allow sufficient c1earonce for sliding aclion.

.050 ALUMINUM PLATE ~AII di....n.ion••hownMake some dimensions os plote are in inche•• Multiply .1 I.at opposite end of caliper.-----../ by 25.40 to obtoln 1.50, r

SECTION A-A milli....ter equivalent.

-:L~ tJI ?~ 7ad,4eee44 ;:J4Ied Seatt

ALL CONSTELLATIONS Some operators have beenusing a coat of silicone grease, Dow-Corning com­pound DC-4, to lubricate the rubber seals on the fueltank access panels. This lubrication is intended toprevent the seals from sticking to mating surfacesand to eliminate the possibility of the seals tearingwhen the access panels are removed.

Our Materials and Processes group disapprovesthe use of silicone grease such as DC-4 for this pur­pose. DC-4 is a transparent grease which can pene­trate, to some degree, any surface to which it isapplied. Since it is difficult to see, any that is inadver­tently applied to existing tank sealant could not bereadily removed and would form a coating to whichfuture tank repair sealant would not adhere.

In Vol. 2, No.5, of the March-April 1956 Digest(English edition) we presented a TRADE TIP fromTrans World Airlines on "Matching Main Gear TireDiameters." Other operators have shown sufficientinterest in this TRADE TIP to warrant our passingalong some supplementary information which wereceived recently from TWA's Los Angeles base.

ALL CONSTELLATIONS O-rings which provideexternal seals for moving shafts in hydraulic unitsare, by their very nature, almost always subject tovarying degrees of leakage. Years ago, many peoplesaid that hydraulics on aircraft were impracticalbecause no one would ever find a seal that would notleak. Actually, those designs which require absolutefluid-tightness for successful operation have neverbeen completely feasible, and probably never will be.

Years of experience with hundreds of thousandsof hydraulic units have proved that O-rings suit theirpurpose better than any other type of seal knowntoday. O-rings are practical-particularly if leakageis judged from a practical viewpoint.

The main question which we wish to answer hereis, "When is leakage serious enough that a hydraulicunit should be replaced?" We believe that a realisticanswer will result in a substantial reduction in thenumber of unnecessary removals experienced at someactivities.

In order to understand better the important facetsof the problem, we will have to study briefly thedevelopment and nature of the O-ring seal as wellas its characteristics under operating conditions. Thenwe will present some general suggestions for deter­mining the seriousness of O-ring leakage and forrealizing better service from O-ring seals.

10

DEVELOPMENT OF SEALS

RUBBER CUPS In the earlier aircraft hydraulic sys­tems, fluid was retained within working componentsby means of rubber cups somewhat like those usedin automobile hydraulic brake systems. These cups,when carefully made and used with smooth metalsurfaces, produced fluid-tight seals-for a while.However, they had several very undesirable weak­nesses. In order to seal against the metal surface, thelips of the cup could not be stiffened sufficiently toprevent their folding back on themselves or tearing.Also, the proportionately large amount of rubber inthe cup was such that any swelling caused the heelof the cup to expand and contact the sealing surface.This deformed the lips of the cup and they wouldmove away from the sealing surface.

These failings would eventually result in a com­plete loss of fluid from the hydraulic system, sincethe rate of flow past the damaged seal was verygreat.

CHEVRON SEALS In an endeavor to correct some ofthe disadvantages of the rubber cups, the V-shapedpacking ring or chevron seal was adapted for air­craft use from its usage in heavier industrial pack­ing applications. The chevron seals were usuallyinstalled in a stack consisting of two or more sealswith metal adapters at each end of the stack. These

Too large an O-ring leads toinstallation problems, excessivefriction, and deformation of thering in its groove.

>..

Too small an O-ring results inan ineffective seal.

Figure 2 O·ring Squeeze

Since the O-ring is a round section, it must bearagainst the sealing surface with sufficient force todeflect into the minute grooves of the machinedsurface and stop leaks. This makes the degree ofseal achieved sensitive to slight imperfections in thea-ring and the effects of certain types of foreignparticles such as threads, hairs, or fibers lying acrossthe sealing face. These faults can be minimized byselecting and installing the a-ring carefully asdescribed later.

O-RING SQUEEZE With practically all types of seals,the pressure, or squeeze, necessary to produce a goodseal, even at low hydraulic pressures, is produced byhaving an interference fit between the seal and themetal surface. For the a-ring to be effective, thisfit is critical and is established by the diameter ofthe a-ring as shown in Figure 2. Not enough squeezewill of course result in an ineffective seal. However,there is a limit to the amount of squeeze that can beemployed. Too much squeeze means: increased diffi­culty of installation, more friction at low pressure,and increased deformation of the ring in its groove.Also the undesirable tendency of the rubber toadhere or bond to the metal surface increases. Themilitary specification MIL-P-5514A lists the amountsof squeeze which will produce the best results inmost installations.

BACK-UP RINGS

Correct size O-ring provides proper interferencefit between O-ring and metal surface.

~

11

As hydraulic system pressures were stepped upfrom 800 to 1000 psi, to 1500 psi, and then to 3000psi, the load on the O-ring seal increased con­siderably. The tendency for the O-ring to extrudeincreased and became critical. Also, actuator shaftswhich moved in and out many times a minute placeda heavy burden on the O-ring. These circumstancesnecessitated an extra ring in the groove to support,or back-up, the O-ring (see Figure 3).

(Continued on next page)Figure 1 Spiraled O·ring

seals had the advantage of greater operating strengthand, as they were installed in multiples, a flaw inone ring would not necessarily result in a leakygland.

However, chevron seals had a high and variablerate of friction. Also, these seals were bulky anddifficult to adapt to a valve application withoutresulting in a very cumbersome design.

O-RINGS The a-ring was a great improvement overboth the cup and the chevron seal. Because of itssimplicity, it literally revolutionized the design ofhydraulic components. It could be stretched orsqueezed into grooves in ways not possible with anyother seal. This allowed a reduction in size andweight of hydraulic components and permitted thehydraulic system to do a greater variety of jobs.

The a-ring is also a stronger seal. There are nothin lips or protrusions to break off or deform. Agreater amount of seal area contacts the metal sur­face so there is less tendency for the rubber to flow,or extrude, through the crack between seal and seal­ing surface. This strength of the a-ring providesincreased protection from a sudden and completeloss of system fluid.

SOME FAULTS TOO As with most things, there arealso some faults with the a-ring. Being round, thea-ring can roll slightly in operation. If a portion ofthe ring rolls too far in the groove it twists a crosssection of the ring and leads to what is known asspiraling, illustrated in Figure 1. This can perma­nently deform the ring and may result in its crackingor parting completely.

(I

Teflon, a synthetic plastic material, has recently beenfound to be a more satisfactory back-up ring materialthan leather. It has low friction, is somewhat pliableand is chemically inert. One disadvantage with thismaterial is that it is not flexible enough to bestretched or deformed into place in a groove and soit must be split for most installations as shown inFigure 5. The split, or scarfed, ends can sometimescut the a-ring.

This difficulty, however, is gradually being resolvedby continued research. One recent example of betterapplication of the Teflon back-up ring is in the mainlanding gear shock struts. Owing to the configurationof the gland in the shock strut it is possible to use anendless Teflon back-up ring, which is rectangular incross section, below the a-ring. A spiral Teflon ringis used above the a-ring (see Figure 6). These ringshave been service tested by a large airline and foundto be satisfactory.

While some leather back-up rings may be in use incertain components of the Constellation, our designtrend is toward Teflon as the better back-up ringmaterial.

• 1000 PSI PRESSURE •

~• 3000 PSI PRESSURE •

Figure 3 O-ring Under Pressure

• 800 PSI PRESSURE •

..:• 1500 PSI PRESSURE •

Figure 4 Failed leather Back-up Ring. Note that the ring has assumedthe contour of the O-ring, resulting in sharp edges which

can cut and nibble the O-ring.

Leather was the first material used for back-up rings_It was stiff enough to resist extrusion but pliableenough to flow into place and help the seal. How­ever, leather is sometimes too hard, sometimes toosoft. It absorbs moisture and contains acid and salt,all of which corrode metal. It often shreds and thefibers can get into the system and under a-rings.Figure 4 shows an unserviceable leather back-up ringwhich has become hard and deformed.

Figure 5 Teflon Back-up Rings. Split, V-shaped ring is shown above;split, rectangular ring is shown below.

12

Figure 6 New Configurations of Teflon Back·up Rings Used in Mainlanding·Gear Shock Struts

EVALUATING LEAKS AROUND a-RINGS

It can be seen from the foregoing discussions thatleaks, large and small, and caused by a variety ofthings, can accompany any seal. The successful andpractical approach to the problem is this: Beforedeciding to remove and replace a hydraulic com­ponent, evaluate the effect of a leak in any unitand in any system to determine what amount ofleakage can be tolerated and what amount mightbe a hazard to the safe and effective operation ofthe aircraft.

TYPES OF O-RING LEAKAGE In the first place, weshould differentiate between failures that allow acomplete loss of fluid and faults that usually resultonly in slow leaks from a unit.

Except for failures of the spiraling variety andcases where static rings blowout or pieces of movingseals are actually torn out due to excessive clearance,O-rings normally do not fail so as to cause completesystem failure.

However, as previously stated, O-rings may beexpected to have leaks of the seep or drip variety

and there are several reasons for this. As the pres­sure builds up or decreases in a unit, the O-ringmoves in its groove (see Figure 7). As it moves, italso rolls somewhat because of its shape. This createsa pumping action that permits a small quantity offluid to get by on each cycle of pressure change. Thisalso happens when a shaft or piston is moved in abore. Pumping even occurs to some degree with astatic seal. Static seals are so called because the partspresumably do not move. But there is always somedeflection or slight motion in the seal parts.

Ambient air temperatures affect the sealing qualityof the O-ring. In cold weather the seal contracts andprovides less absolute sealing in the static condition.In the same manner temperature cycling can alsoinduce a higher leak rate. This is usually the casewhen an aircraft is moved to and from a heatedhangar during cold weather.

Since the O-ring requires a relatively greater bear­ing pressure to create a seal than do the cup orchevron types, the O-ring is sensitive to slight imper­fections in its own surface or in the metal surfacesas previously mentioned. A rough bore, rod, orO-ring groove will, of course, be more apt to causeleakage than a smooth one. However, the apparentsmoothness of a surface can be deceptive, especiallyafter continued wear has created wear marks at rightangles to the original finish marks. It is not wiseto assume arbitrarily that the surface finish is toorough from appearance alone. A profilometer read­ing, or at least a comparison with a finish sample ofknown roughness is the only sure method.

O-ring manufacturers have made great progressin improving the smoothness and accuracy of their

Figure 7 O·ring Pumping Action. Rolling action of O·ring squeezes or pumps out minute quantity of fluid at each cycle of pressure change.

13

rings, but it is inherently impossible to producerings having absolutely no imperfections. It remainsthen, a matter of judgment as to when a defect ina newly manufactured O-ring is cause for rejectionand when it can be accepted. Work is now beingdone on a photographic method of evaluating O-ringdefects. This will present enlarged views of thevarious types of defects so they can be classified asto acceptability.

It should be kept in mind that the characteristicsjust discussed generally produce the seep or driptype of leak. Progressive or erosive wear of theO-ring should not be assumed as the cause of leak­age unless a careful check as described later in thearticle proves such to be the case.

INTERPRETING THE SPECIFICATIONS The net resultof the various shortcomings we have described is thatvery often we find a seal leaking slightly or passingfluid owing to its pumping action. Internal seals dothis also but because they are hidden it is not obviousand no one ever detects it unless it impairs the unit'sfunction. The difficulty lies with the external sealswhich functional test specifications usually say, "shallhave no external leakage." Various attempts havebeen made over the years to improve the wording ofthe specifications to express the intent that a slightamount of fluid escaping past a seal normally has noreal significance. The latest wording that is beingincorporated in the military hydraulic systems specifi­cation says, "There shall be no measurable externalleakage." This is intended to mean that a light stainor wetting which does not actually form a measur­able drop is acceptable.

When it comes to moving shafts which work inand out of a stuffing box, or gland seal, as it issometimes called, the acceptable-leakage problem iseven more acute. MIL-C-5503, the military specifica­tion for actuating cylinders, has always recognizedthis by specifying an allowable leakage rate past amoving seal of one drop per 25 cycles of operation.Unfortunately, this arbitrary limitation does not takeinto account such variables as shaft diameter, stroke,or rate of cycling. These all have an effect on therate of leakage. Also, the size of a drop varies withthe temperature and the shape of the part on whichthe drop forms. A drop of MIL-O-5606 fluid isnormally considered to be 1/20 of a cubic centimeter.Since there are 16.39 cubic centimeters per cubicinch, this means 326 drops per cubic inch, or approxi­mately 75,000 drops per gallon. Obviously, it wouldtake a tremendous number of leaks of the dropvariety to have any appreciable effect on the fluidlevel in the reservoir of the average system.

14

The specification also fails to take into account thevariations in the mode of operation, particularly theoperation of power control or boost actuators. Inthese units the piston rod may move in and outthrough the gland several times per second. If weassume an average rate of movement of one cycleper second, this is 36,000 cycles per hour. At therate of one drop per 25 cycles, this amounts to 144drops per hour, or approximately 7.2 cubic centi­meters per hour. This would collect a large pool offluid in each flight but would be within the allowableleakage rate specified by MIL-C-5503. It is obviousthat such an amount is more than the average actua­tor actually leaks, but it emphasizes the necessity forgreatly revising our thinking as to allowable leakage.Otherwise we must abandon the use of the O-ringand go to other, more cumbersome types of seals.

EVALUATING LEAKAGE Here is a practical approachto deciding whether a hydraulic unit should bereplaced and some suggestions for realizing betterservice life from O-rings.

Units such as landing gear, flap drive, etc., thatoperate only a few times during flight should beconsidered satisfactory if, upon inspection afterflight, only a few drops of fluid have collected. Anylarge increase in the leakage rate from one flight tothe next should be viewed with suspicion, however.

The above units should be allowed some leakagewhile the airplane is parked, say a few drops over­night. Here again a large increase in leakage over aperiod of time would be the signal to remove theunit and check the seals.

POWER CONTROL ACTUATORS For power controlactuators, the present specification is not actually agood criterion for allowable leakage. In our ownlaboratory work at Lockheed we have revised theprocedure of measuring drops per cycle and aremeasuring drops per minute, since operation is moreor less continuous. Our present testing procedure isto continue the tests until leakage reaches five dropsper minute from a rod seal. At this rate, the amountof fluid that would collect in an eight-hour flightwould be approximately 120 cubic centimeters.While this quantity could result in a considerablewetting of surfaces exposed to the leakage, it is notparticularly detrimental to the operation of thehydraulic system or the airplane. It should be bornein mind, however, that excessive fluid collecting inan area where ignition could occur is a hazard whichmust be avoided. If such a hazard does not exist, itis certainly preferable to wipe up the excess fluidand to check the reservoir level occasionally than toremove and replace power control actuators.

Incidentally, the above leakage rate turns out tobe roughly equivalent to the military specificationallowance of 25 cycles per drop, based on two cyclesof control surface movement per second. This isadmittedly on the high side for an airplane like theConstellation, yet a permissible leakage rate of about50 cubic centimeters per eight-hour flight would beentirely reasonable. Here again the important crite­rion should be the sudden appearance of a largeincrease in leakage rate.

MAINTENANCE

Our Field Service Representatives haveasked us to emphasize that preventive main­tenance pays big dividends where the a-ringseal is concerned.

LUBRICATION Every effort should be made to cleanand lubricate piston rods and moisten the felt wipersperiodically with MIL-L-7870 general purpose lowtemperature lubricating oil as called out in the main­tenance manuals. The intervals between lubricationshould be shortened in severe operating conditions.This procedure will undoubtedly aid in cutting downleakage and will reduce the number of seal failures.

INSTALLATION Proper installation of replacementseals is vital. Volumes could be written on this phaseof D-ring seals, but if the following main points areobserved the D-ring will do its job.

1. Be sure that O-ring seals are not replaced whilethe hydraulic unit remains installed on the airplane.These units should be removed and sent to shops ordepots for rework where the proper protection, tools,and test eq~ipment are available.

2. Double check the O-ring to be installed forproper identification and condition-is it the correctsize and type? Refer to the applicable instructionsmanual or technical order for full particulars on theindividual installation being considered. Is the O-ringfree of unacceptable defects and irregularities?Examine the O-ring carefully for any cracks orroughness which would allow leakage. Check thedate on the D-ring box. If it is more than two yearsold the D-ring should not be placed in service.

3. Prior to installing the O-ring, make certain thatit and the component are clean and free of anyforeign particles. Immerse the O-ring in the typefluid in which it is to be used and apply the samefluid to the groove.

4. Be very careful not to twist or scratch theO-ring when fitting it in the groove.

In summation, we should always remember thathydraulic seals were never intended to be absoluteseals, and we will have greatly reduced maintenancecosts and achieved more satisfactory utilization andservice if we recognize and accept the inherent char­acteristics of the O-ring when evaluating leakage atexternal seals. A A

15

w. Fred Tenge, Lockheed electrical design engineer, describes the new . ..

. . . for military radar airplanes

MODEL 1049A There is an ever increasing need foradditional electrical power to make ground check­outs of electronic equipment on military AEW SuperConstellations. This increased power overloads thesingle AN-2552 ground power receptacle and Hart­man A702AA ground power reverse current relay tosuch an extent that ground test procedures have to berestricted to a maximum continuous load of 475 ampsde.

The doc power requirements for complete check-outof electronic equipment, plus normal electrical loadsfor lights, cooling, and ventilation, are presentlyabout 850 amps de. Future airplanes with automaticnavigating devices and improved electronic equip­ment will require about 1200 amps de for a completecheck-out.

NEW SYSTEM DEVELOPED To provide for the futurerequirement of 1200 amps de and to allow for fur­ther growth, a 1500 amp doc ground power systemwas developed. Because no electrical components areavailable to handle these high electrical loads, thetotal load was divided between two busses-an elec­trical main power bus and an electronic bus. Two750 amp external power receptacles (one for eachbus) determined the name, "Dual D-C Ground PowerSystem."

Figure 1 Location of Components

16

LOCATION OF COMPONENTS See Figure 1. The tworeceptacles are installed in a pressure box forward ofthe radome between fuselage stations F 36.8 (stressstation 564.4) and F 55.2 (stress station 582.8). Theyare accessible through an external door, locatedslightly to the right of center on the lower surface ofthe fuselage. The white "power on" lights, one foreach receptacle, are in the receptacle box.

It was necessary to place the receptacles in thisposition, rather than in the former ground powerreceptacle location, to avoid a severe weight penalty.This present location is close to the inboard propel­lers, which necessitates revising the sequence ofengine starting in the interests of ground personnelsafety. The revised engine starting procedure will begiven later in this article.

An interphone junction box is installed adjacent tothe two receptacles and is accessible through a sep­arate door in the skin.

The relays for the system are installed in a fiberglass box on the right side of the forward baggagecompartment, between fuselage stations 73.6 and 92.0.

The external power switch and the "EXTERNALPOWER ON" green lights are in the same location asbefore on the main junction box (M]B) No.1 panel.

NEW SYSTEM OPERATION

USING THE RECEPTACLES To supply doc groundpower for checking out the electrical system only:Connect doc power source capable of continuouslysupplying 600 amps into the electrical power recep­acle.

To supply doc ground power for checking out boththe electrical system and the electronics system or

ELECTRONIC BUSEXT POWER ON IT

2 1

MAINPOWERBUS

P145B18-4---o--(lSHIP'SBATTERY

~SWITCH J

- P144A18N---~

IMJ B NEGATIVE M J B NO, 1 PANEL

BUS

r----P566C20-+--.[IGlI~

~g~RE~Al P144C18N

SWITCH ~

P144B18N

MAINXP312A1/0-ELECTRONIC

INVERTER

SPAREXP313A1/0-ELECTRONIC

INVERTER

P551A1/0-~~~:TORS PANEL

H738A8-- ~~~~::~OWER

H739A6--~1ARBLOWER50A

P560A 110--i-----e"'

P560C1 10--+----.....

25fl37W P568A18N

P572A14

P555B20

Q-+!--P560B1 10--+----.....,

DC-EXTERNAL POWER CONTROl BOX

MAIN BUS EXTERNAL POWERREVERSE CURRENT RELAY

_

_ F===t~~~~~~SP~55~5~B~2~0~~~~:::l-r~~~~~~]=;~MJB NO, 3

P552A20 25fl37W FLIGHT ENGRSELECTRONIC BUS WARNING LIGHT

ELECTRONICS BUS CIRCUIT BKRPOWER ON IT

+

+

+

+

P5~20

P573A20N

.2.GND"="STUD

1----~5':"A'tR....E-lA-Y-...."B-'-'H--I+-+P564A18-1--------'

EXT PWR CONTACTOR CKT BKRS

FORWARD CARGO COMPARTMENTCIRCUIT BREAKER PANEL

DC-EXTERNAL POWERRECEPTACLE BOX

SP

2

r

p561A181

I IP57;:1:~:t__l_8-+-=-.",.-l..:"

~P569B20 1

W S P MAIN BUS L--+'P=-=5"':'6"'6'B 18P574~20Nl POWER ON IT - - --P569A20 ~'_ ,J

L tIro--' GND STUD ~A18

I~ X,-~I + EXTERNAL POWER5A - ISOLATION

RELAY "Au CONTACTORCONTROL RELAY

P550A 1ION-oJ••P550B 1 I0N-1ol'.P550CI 10~11P553A1/0---+----;---,.,.P553Bl/0----t----+--:::±7l:l

P553Cl10-===tC:~~=~~~~~~~~~~~::;:;;~~~dU+ P554A14-----+':.--d"::'~

ELECTRONIC EXTERNAL POWER

IRECEPTACLE

ELECTRICAL EX~ERNAl POWERRECEPTACLE

+ P557A14----l--~5=-A~,........J

E!.ECTRICAl -----'EXT PWR C ONTRELAY CKT BKRS

Figure 2 Electrical Schematic Diagram of New Ground Power System

17

for checking out the electronics system only: Connectboth the electrical receptacle and the electronicsreceptacle to a power source capable of supplying atleast 1200 amps continuously, or connect each recep­tacle to separate power sources capable of supplyingat least 600 amps each.

NOTE

The two new d-c ground power receptaclesLAC PIN 619176-1 are a different configura­tion than the former receptacle. In order toproperly match the new receptacles,plugs on the d-c ground power cart shouldbe Burton Electric Engineering Co. PIN 217.These plugs are available from Burton Elec­tric Engineering Co., III Maryland Ave.,EI Segundo, California.

System operation when external power is connectedto the electrical receptacle: Refer to Figure 2. Withthe external power switch on MJB No. 1 panel in"OFF" position, the "ELECTRICAL BUS EXTER­NAL POWER ON" green light will indicate thatexternal power is available to the main power bus..When the external power switch is placed in the"ON" position the external power isolation contactorcontrol relay becomes energized. This relay then dis­connects the two electronics bus external power isola­tion contactors "A" and "B", dividing the d-c systeminto two busses-an electrical bus and an electronicsbus. At the same time the relay completes the circuitsfrom the short pins of the external power receptaclesto the "SW" terminals on the electrical main busexternal power reverse current relay and the elec­tronics bus external power reverse current relay. Thismakes possible the energizing of the electronics busif power is later supplied to the electronics receptacle.Therefore, the electronics bus can be energized onlywhen the electrical main bus is energized.

The electrical external power receptacle will nowenergize the electrical main bus only, provided theexternal power is of the right polarity and potential.The white light in the receptacle box will indicatethat the connection from the electrical external powersource is completed.

System operation when external power is addedthrough the electronics receptacle: Refer to Figure 2.The electronics bus external power reverse currentrelay will connect the electronics receptacle to theelectronics bus as soon as the small pin becomes ener­gized, provided the external power is of the rightpolarity and potential. The "EXTERNAL POWERON ELECTRONIC BUS" green light on the MJBNo. 1 panel will indicate this condition, while a sec­ond white light in the receptacle box will indicatethat the connection to the electronics bus is completed.

18

NEW ENGINE STARTING PROCEDURE Since the newlocation of the dual d-c ground power receptacles isclose to the inboard propellers, the engine startingsequence has been changed. Also, the d-c groundpower cart must be placed in a different position thanbefore when starting the engines.

At the LAC production flight line the d-c groundpower cart is placed about 5 feet aft of the wingbehind nacelle No.3. This location requires powerleads about 30 feet long. Locating the power uniteither forward of the receptacles or aft of the landinggear is not recommended. The location forward ofthe receptacles would result in ground personnel hav­ing to walk through the propeller plane, and thelocation aft of the gear would place the unit underfuel tank vents, which would create a potential firehazard.

The following is an extract from the latest revisionto the Flight Handbook describing the new enginestarting procedure for aircraft with the new dual d-cground power system.

The new engine starting sequence is 4-1-3-2. EngineNo. 4 is started first to provide secondary hydraulicpressure. Outboard engines are started first to allowground personnel to remove the ground power leadsand cart before inboard engines are started.

All radar equipment, recirculation fans and unneces­sary radio and electrical equipment must be turned offbefore starting of inboard engines to reduce the load onthe ship's batteries and outboard engine generators.

Check secondary hydraulic system for pressure andcheck operation of Bight controls after engine No.4 hasbeen started. This check must be made to ensure that thecrossover valve is functioning. The hydraulic systemcrossover switch (if installed) should be positioned to"EMERGENCY" and then returned to "NORMAL" forthis check. The right cabin air mixing valve should bepositioned to cut off right wing refrigeration so thathydraulic pressure will be available.

After starting engines No. 4 and No. 1 (outboardengines) the starting procedure for the inboard enginesis as follows:

a. Run outboard engines at 1200 rpm.

b. Switch ship's batteries and outboard engine gen­erators "ON."

c. Switch external power "OFF."

d. Have ground power supply removed.

e. Start engines No.3 and No.2.

SERIALIZATION The first aircraft to have this newd-c ground power system installed in production is AFSerial 55-131 (LAC Serial 4404) and BuAer Serial141306 (LAC Serial 4430). A retrofit program for

the Air Force is authorized under T.O. lC-12l (R)­548 and covers all Model RC-l2lC and RC-l2lDaircraft manufactured prior to the production change

point. A retrofit program for the Navy is authorizedunder R7V;WV Aircraft Service Change (ASC) 309and covers all Model WV-2 and WV-3 airplanes

delivered without this change incorporated. ModelR7V-l and R7V-2 aircraft are affected by ASC 309but only in regard to replacing the A702AA relaywith an A79lBB relay. The new relay will have acontinuous duty rating of 600 amps as opposed to acontinuous duty rating of 450 amps for the existing~~ ~~

Drain Holes In AileronControlAccess Doors

MODELS 1049A THROUGH H To reduce the possi­bility of water collecting and freezing in the area ofthe aileron control access door, it is recommendedthat three holes be drilled in each access door asshown in the illustration. This will allow the waterto drain as rapidly as possible and prevent the doorfrom being torn loose or otherwise damaged by anaccumulation of ice. ~ ~

SERVICEBULLETINS

PENDING

SUPER CONSTELLATION SERIES1049

SBNo.

2889

2894

2928

2934

ApproxRelease

Feb1957

Jan1957

April1957

Jan1957

Subject

Replacement of HydraulicPump Pressure Line inNo.3 Nacelle

Modification of ForwardToilet Drain Access Door

Replacement of HydraulicPump Pressure Lines inNos. 1, 2, and 4 Nacelles

Revision to HRD FireExtinguisher ControlPanel

Description of Change

Provides information for replacing the pressure linerigid tubing with a flexible hose assembly for in­creased service life.

Modifies door by installing improved fasteners topreclude failure in flight.

Similar to 1049/SB-2889 except is applicable only toNos. 1,2, and 4 Nacelles.

Relocates heater fire warning lights and selectorswitches on panel for more positive identification.

~~

19

-- -

~0

• . • • • • • • . ••'.- ':"r'

~.(~.'" ~.>

CAA APPROVED AIRPLANE FLIGHT MANUALS

LACIEPOIT APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX SUPPLEMENT SUPPLEMENT SUPPLEMENT SUPPLEMENTMODIL NUMaUANDImSIONDATE I II III IV V VI A B C D

LI5I17049 and IA9 IS Dec 1955 23 Mar 1951 (Deloted) 1 Dec 19A7 22 Dec lfA7 10 "Mar 1953 IA Sopt 1955 - - -60'9 and 7A9 LI6028 2 Juno 1955 18 Apr 1955 2 Juno 1955 (Delotedl 2 Juno 1955 - - - - -

IS Dec 1955 (Supplomont A2 Juno 1955)

1049 LI77872 Sept 1955 25 Mar 1955 - - - - - - - - -

l0A9C and I with Curtiss Ilec LI9153 ~ (l049D only)Props (lelssued 1 Nov 1953) 10 May 1956 10 May 1956 31 Mar 1955 - - - 31 Mar 1955 15 Dec 1955 10 May 1956 31 Jan 1956l0A9C and I with HOMlltonStandard Props (Ioillued LI91SA15 Oct 19531 30 Mar 1956 30 Apr 1956 25 May 1955 - - - - 30 Mar 1956 - - -10490 with Curtlll Ilec Props Lll0051 Revision dote applies to all .ections of thl, manualO..uad 20 Juno 19551 10 $opt 1956l0A9O with HaMilton Slondard Lll0052 Revision dat. applies to all ,ectlons of this manualProps I"suad 5 July 1955) 19 Oct 19561049 0/01 104'" Llll020

1 Oct 1956 - - - - - - - - - -

\ COMMERCIAL PUBLICAnONSMODEL

PUBLICATION TInE 049 149 60'9 7A9 l0A9 l0A9C 10490 l0A9E 1049G -104'"

La 7788 and50/2680 .. La 5795 .. LR 7963 LR 8681

Molnton_ Instructions 15 $opt 19... 15 Juno 1953 1 Feb 1953 I Oct 1956 -Ll5116 La 7789 La 8882

Structural 1_lr 15 Dec 19SA 15 Sopt 1956 15 July 1956Molntenonco Ports Cololog Feb 1952 .. Dec 1952 Oct 1956 Dec 1956

LI6027 .. LI7786 La 8758 LI9814 .. LI 10050 LI11360Crow Oporatlng Monuol - - 1 Juno 1955 15 May 1955 1 June 1956 1 Apr 1956 15 Juno 1956 15 Oct 1956Intogrol Fuo' and 011 Tonk L15909~allng 1 Juno 1955

LI 10038Powerplant Buildup Inltructlons - - - - 15 Oct 195A - -

\ MILITARY PUBLICATIONSMODEL

l7V-l C-121 A C-121C IC-121C IC-121 0 WV-2 WY-3 YC-12l1 VC-12l1 YC-121FPUBLICATION TITLE AN 01-75CMA· T.0.1C-121A- T.0.1C-121C- T.0.1C-121 '11C- T.0.1C-12111ID- AN 01-75CKC- AN 01-75CKC- AN 01-75CMA· INCLUDED WITH T.O. 1C-121 'II C-

(SUPPLEMENTSI 1C-121 A- ISUPPLEMENTSI

Flight Handbook 1-11 1 Sept 1950 1 Jan 1956 1 Aug 1956 15 Apr 1956 1 Sept 1956 15 Mar 1956 T.O. lC·121 (YlF·lMalntenonce Instructions (-21 15 Feb 1956 I Sopt 1956 15 Aug 1956 15 Nay 1956 1 Sept 1956 15 May 1956 .. I Jon 1955 1 Dec 1956

AN Ol-75CM·3 .. AN 01·75CM·3Structutol I_It (·31 1 Aug 1956 1 Juno 1956 1 Aug 1956 15 Aug 1956 15 Sept 1956 15 Oct 1956 I July 195A - 15 Sept 1955lIIultra.-cl Port. Brookdown (... '1 Feb 1956 1 Mar 1956 I Nov 1956 1 July 1956 15 Nay 1956 1 Dec 1956 ... 1 Jan 1955 1 Mar 1956 15 Fob 1956

AN 01·75CM·6loillued .. lol..ued AN 01·75CM·6

Inspectlon loqulrDlllonll (.61 1 Jon 1953 20 Fob 1956 15 Apr 1956 I Dec 1956 15 Dec 1953 I Aug 1955 1 July 195A - 15 Sopt 1955CorgO Loading Inltructlon. (-91 IS Apr 1955 1 Aug 1955 - - - -Powor Pocko,o BuildupInltructlonl (.11) - - 15 July 1956 - - - - -

0 v 0b '. -

The Lockheed Parts and Service OrganizationWalter C. Smith, Director

FIELD SERVICE AND TRAINING DIVISION

field Service Operations Dept.

field Service Planning Dept.

field Service Training Dept.

·N. M. Harrison, Manager

·LE. Mason

•R. G. Richards

.1. l.larson

SPARE PARTS DIVISIONCommercial Spares Dept.Military Spares Dept.Spares Stores Dept.. .Spares Technical Dept..Maintenance Equipment Group.

· D. S. Stevenson, Manager• R. A. Barnard· W. A. Marco• W. M.lowe• E. Scott· C. R. Young

CONSTELLATION FIELD SERVICE REPRESENTATIVES

Kansa,.City, Kansas

Ent AFB, Colorado

Stewart AFB, New York

Wabash 2-1511Ext. 3-123

Wabash 2-1511Ext. 3-123

Newburgh 4900Ext. 746 or 8128

NEwton 4-3571Ext. 560

Olympia 6-5314or 6-5315

Olympia 6-5314or 6-5315.

DRexel 1-5680Ext. 50

MU 042, Ext. 211Mascot N.S.W.

TELEPHONE

25-2165Rio de Janeiro

GoBelins 45-85Ext. 51-64 Paris

Volunteer 3-3111Ext. 645 or 251

Volunteer 3-3111Ext. 645 or 251

Evergreen 9-7711Ext. 8217 or 8284

4-05", Ext. 42214Hickam AFB

60076, Ext. 278Bombay

62411, Ext. 556

Charleston 4-4211Ext. 3469

Cataumet 700Ext. 2536

liberty 5-6700Ext. 71920

Melrose 2-5511Ext. 2754 & 2033

San Bemardino9-4411, Ext. 5131or 6216

P.O. Box 218, Naval Air Test CenterPatuxent River, Maryland

P.O. Box 218, Naval Air Test CenterPatuxent River, Maryland

P.O. Box 1766Yukon, Florida

AIRTRANSRON 8 lVR-81, Navy #128 FPOc/o Postmaster, San francisco, Callfomla

P.O. Box 1010, McClellan AFBMcClellan, Callfomla

P.O. Box 1010, McClellan AFBMcClellan, Califomia

Directorate of AircraftDeputy for Materiel EADFStewart AFB, Newburgh, New Yode

lockheed BoxCharleston Air Force BaseCharleston, South Carolina

P.O. Box 336Pocasset, Massachuse"s

111 So. Kensington St.Arlington, Virginia

2312 No. Wood AvenueColorado Springs, Colorado

c/o Dlredorate of Flight Safety Research, Ftr. Br.Norton AFB, San Bemardlna, CallfomlaA": LocIcheed Service Representative

c/o Eastem Air lines, P.O. Box 787Int'l Airport Branch, Miami 48, Fla.

Room 2-E-14Hangar No.2, N.Y. Int'l Airport, Jamaica 30, N.Y.

Room 2-E-14Hangar No.2, N.Y. Int'l Airport, Jamaica 30, N.Y.

TWA Overhaul Base, Room 102Fairfax Airport, Kansas City, Kansas

c/o QANTAS Empire AirwaysHangar 58, Kingsford-Smith AirportMascot, N.S.W., Australia

MAILING ADDRESS

{

c/o Air India IntemationalSanta Cruz Airport, Bombay 29, Indiac/o Pakistan Intemational AirlinesKarachi Airport, Karachi, Pakistan

c/o John I. Wagner, Av. Franklin Roosevelt 3914 Andar, Sala 1411, Rio de Janeiro, Brazil

lockheed Aircraft Hangar No.9PTT Schiphol AirportAmsterdam, Netherlands

6 Route de VersaillesPetit Champlan longlumeauSeine et Oise, France

V. H. FreitagRegional Service Representative

F. W. Gates, Jr.Regional Service Representative

C. W. PriceResident Service Representative

R. T. SlusserRegional Service Representative

E. l. DuclosRegional Service Representative

J. R. GipsonResident Service Representative

R. P. McintyreResident Service Representative

H. D. SaleResident Service Representative

D. J.SchmittnerResident Service Representative

D. C. SwallaResident Service Representative

D. E. MarkleyResident Service Representative

B. J. BrunoResident Service Representative

NAME

S. E. lucasRegional Service Representative

G. H. SmithRegional Service Representative

C. R. Pi"manRegional Service Representative

D. H. HoradamResident Service Representative

C. R. KelleyResident Service Representative

C. F. WemleResident Service Representative

F. R. SwansonRegional Service Representative

R. E. RipleyResident Service Representative

E. C. JoslenRegional Service Representative

}Amsterdam, Holland

NAVY

Sydney, Australia

Paris, France

Rio de Janeiro, Brazil

Patuxent River NAS, Maryland

Patuxent River NAS, Maryland

New York City, New York

Jacksonville NAS, Florida

LOCATION

COMMERCIALMiami, Florida

AIR FORCE

McClellan AFB, Callfomia

New York City, New York

Charleston AFB, South Carolina

Karachi, Pakistan

Bombay, India

Otis AFB, Massachuse"s

Washington, D.C.

McClellan AFB, Califomia

Norton AFB, Callfomia