Army Aviation Digest - Aug 1967

8/12/2019 Army Aviation Digest - Aug 1967

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UNITE ST TES RMY AUGUST 967VI TION GEST


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UNITED

DIRECTOR OF ARMY AVIATION, ACSFORDEPARTMENT OF THE ARMY

MG Robert R. Williams

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COMMANDANT, U. S. ARMY AVIA nON SCHOOLMG Delk M. Oden

ASST COMDT U. S. ARMY AVIATION SCHOOLCOL M. H. Parson

DIGEST EDITORIAL STAFFMAJ L J. Herman Jr., Editor-In-ChiefRichard K. Tierney, EditorWilliam H. SmithDiana G. WilliamsJohn P. Jones

GRAPHIC ART SUPPORTHarold G. linnHarry A. PickelDorothy l. CrowleyAngela A. Akin

DIRECTOR U. S. ARMY BOARD FOR AVIATIONACCIDENT RESEARCH

COL Warren R. WilliamsUSABAAR EDUCATION AND LITERATURE DIV

Pierce l. WigginWilliam E. Car te rTed Kon tosCharles Mabius

AH IG

RMY VI TION

1GESJAUGUST 1967 VOLUME 13 NUMBER 8LettersFind the Enemy Airmobile Style,LTC Kenneth D MertelA Simple Protective Revetment, MAJ Vincent R RittsPaSSing the Weather Buck, CPT Robert D Kelley andMr. Cletus N. YoumansHere Comes the CH-47BThe Human Factor in Army Aviation,Dr. Wallace W ProphetDitching TechniquesAVLABS, COL Harry L BushAir Mission Commander, MAJ Gordon T. CareyFor Aviators On the Way UpWarrant Officer Training Fort Rucker PhaseCPT E R Downing, Jr. , a.nd CPT C R LedfordCrash Sense

Emergency Landing Techniques in HelicoptersGerard M. BrugginkAircraft Maintenance Is Everyone s Job , Ted KontosNATOPS = Naval Air Training and ProceduresStandardization, MAJ Kydean WhitlockFlight Safety Opinion SurveyPearl s

Keep Posted on AR 95 63, CW2 Harry O. Pierce

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81012141724283132

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T he m iss io n of th e U. S. ARMY AVIATION DIGEST is to pr ovi d e in fo rm a ti on of an op era t io nafun cti onal na tu r e co nce rnin g sa fe ty a nd ai rc ra ft acc ide nt preve nti on trainin g, ma in te nanc e , ope ra t iresea rch and de ve lop ment , av ia ti on medi c in e , and o th e r re la ted da ta.Th e DIGE ST is an official Depa rt me n t o f the Arm y pe riodica l p ub l ished monthl y und er th e sup e rvio f th e Co mman da n t , U . S. Army Aviatio n Schoo. Vi ews expresse d he rein ar e not nec e ssari ly th osDep a rtm ent of th e Arm y or th e U. S . Ar m y Avia ti on S cho oL Phot os ar e U. S. Ar m y un less o th erspec i fied . Ii at e ri al may be rep rint ed pr ovi de d cr edit is g iv en t o th e DIGEST an d to th e auth or, uno th e rwise indica t ed .Artic les p hotos and item s o f in te res t on Army Av ia ti on ar e in vi ted . Dir ec t communica tion i.s autized to: Ed itor.inChief U .S . Army A via tion Diges t Fort Ru ck er A laba ma.Use of fund s fo r p rin tin g t his p ubli ca ti on has b ee n app roved b y H eadqua rt e rs, Department o fArm y, 29 Decembe r 1964.

A t ive Arm y unit s rece iv e di str ibutio n un de r the p inpoint di s tr ibuti on sy stem as out l in ed in AR 3120 l\Ia rch 62 an d DA Ci rc ul ar 3105 7, 14 Ma rch 63. Co mp let e DA Form 12 .4 a nd se nd di rec tl y toAG Publications Cente r 2800 East e rn Bo u leva r d Baltimore , ;o.1d . 21220. F o r an y chang e in distriburequire ments mere ly ini ti at e a r evised DA Form 124 .Na ti onal Guard a nd Ar m y Rese rve uni t s s ubmit req ui rements th ro ugh th e ir sta te adjuta nts general

U. S. Army Co rps co mm a nd e rs respec t ive ly .Fo r th ose not e li g ibl e for official d is tr ibutio n or wh o desi re pe rsona l co p ies of th e DIGEST , paidsc ri p ti ons 84 .50 d omes ti c and $5 .50 ove rseas a re ava ilab le from the Superint end ent of Do c um ents UGovernmen t Printing Ofhce Washington , O. C., 20402.


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Sir:In regards to the article "Wa Hoppen" in the January issue of the Aviation Digest. . . .1. While inspecting an 0-470 engine,that TM 1-2R-0470-508 (Modification ofoil filler cap) had been complied with,the following discrepancies were noted:a. The bracket that the safety pingoes through was not welded to the oilfiller neck lAW TM 1-2R-0470-508, butwas riveted and the rivet had workedloose.b . The bracket tang with the holein it was not Y2-inch long lAW TM1-2R-0470-50S.2. These two discrepancies would allow the pin to be installed through theoil filler cap and pass on the outside ofthe bracket tang, allowing the oil fillercap to tum, even though i t appearedthat the safety pin was installed properly.This facility has submitted an urgen-tEJR on this problem area in keepingwith the high standards of safety inArmy aviation.CW3 WILLIAM E. LEWIS(CONNAR NG)162d Trans Bn TARSGroton, Conn. 06341 The following comments were received from A VCOM:1. The OSSibility of an oil filler capcoming 0 after the cap has been secured into place and safetied is an extremely remote possibility rather thana probability.2. If the oil filler cap came off, engine oil loss out through the oil fillertube would create an oil film over theouter surface of the aircraft fuselage including the windshield. This would betrue even if a small quantity of oil werelost rather than the total engine supply . Thus the pilot would notice theproblem.3. The oil filler cap in proper working order secured to an oil filler neckin good condition will not come off inflight even if the safety pin is not installed.4. The safety pin serves as an assurance that the oil filler cap is in the secure position by visual inspection. talso impedes the cap twisting to the insecure position.5. No matter how simple and foolproof a servicing device may be designed, it will not eliminate the requirement for good maintenance and responsible servicing.AUGUST 1967

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6. The 0-1 aircraft has been in thesystem almost 20 years and many commercial aircraft use a similar enginewith a similar oil filler system. In fact,new Continental engines utilize a similar oil filler cap without the safety pinso does Lycoming).Sir:In reference to the April 1967 issueof Aviation Digest article "Debut ofSuper Lou," page 17, we wish to callyour attention to the statement ". . .with a shot of 7S0S hydraulic fluid andMil 5606 oil.Reference: TB A VN 2, dtd 27 Oct1967, Sec III, oils, para 9 - Turbine Engines, subpara a, defines Mil-L-7S0S aslubricating oil.Reference: TM 55-1520-210-20, C 6Chapter I, Section III, Table 1-1, definesMil 5606 as a hydraulic fluid.Since your magazine is so widely readby our troops worldwide, and a greatamount of information is gained throughthe articles, we felt that we had to callyour attention to this, before someoneinadvertently used the wrong items.Please retain the excellent quality ofyour magazine and we look forward tofuture issues.

Sir:

SP 6 STANLEY C. CLARKUSAAVNS MuseumFt Rucker, Ala. 36360I think your Digest is the greatestthing goingl I very much en oyed yourApril issue, especially your story on the"Debut of Super Lou. But I spotted agoof on page 17, second para Whereasyour Huey was fed a breakfast, by thecrewchief, of Mil-780S hydraulic fluidand 1il-5606 oil. Your crewchief got hismenu a little fouled up. t should ofbeen Mil-780B oil and Mil-5606 hydraulic fluid f we fed our choppers hismenu, we all would be in a worldof hurt. Outside of that, please keep upthe good work. Thank you.PFC WILLIAM E. BURTS1st Aviation DetachmentAPO New York 09128

Thanks to SP 6 Clark and PFC Burtsfor spotting an error that several editorsand reviewers overlooked. The EditorsSir:Each class of warrant officer candidates attends a seminar before theirgraduation. A panel composed of three

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warrant officers and a moderator who isalso a warrant officer conduct this twohour period.A most difficult question was presented to me at a recent seminar. Sir,we have read a letter in the 'ArmyTimes' from an instructor, referring tothe lower quality of students beinggraduated from the Aviation School,and we are aware that the matter isdiscussed. What are your thoughts onthis subject?That question generated thesethoughts: I graduated from the Avi

ation School ten years ago with a classof 25 who had started training with 65candidates . We were one of the largestclasses to graduate at that time. I remember hearing the comment, "F lightschool just ain't what it used to be; youjust can't wash out anymore." f I hadjust been two classes earlier I could havegraduated with eight . . . but then Iprobably wouldn't have made it.At that time the rotary wing coursewas relatively new, and instructor experience ranged from a turn-around student to perhaps three years. At theschool now are also instructors whograduated little more than a year ago

but that year was spent in Vietnam inthe accumu lation of nearly 1,000 hoursand an equivalent of experierice thatwould be impossible to measure.

Rotary wing instrument flying wasstill experimental and of course not included in our instruction. There are afew of our group who are not aroundtoday because we were incapable of executing a IS0 turn without ground reference.The newly assigned aviator will re

quire and always has required unittraining before becoming a fully operational aviator. I have found this toply to both recently graduated aviatorsand to those with years of experience. Ibelieve that the time requir,ed to ac-complish this is less fDr today's graduatethan for any before him.

There is no substitute for experienceand I think that today's graduates arebetter prepared to face the real aviationschool than any of us were-the onethat begins when the wings are pinnedon and never ends.

CW3 ROBERT G. FRANKDept of Rotary Wing TrainingFt Rucker, Ala. 36360


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inelth n myAirmobile Style

In an airmobile infantry unit in Vietnam today in-telligence and reconnaissance always a difficultproblem in the past have been improved to apoint where the enemy s located more rapidlythan before in a counterinsurgency environment

ISUALIZE yourself the commander of a North Vietna

me se Army NVA) battalion.Your unit has been on the trailfor the past 60 days. It has beena long hike; your troops are heavily laden with weapons and ammunition. Those 81 mm mortarshells and the 120s get awfullyheavy. Movement has been relatively easy however. You havebeen in a neutral country andhave been well cared for at theperiodic rest stops. This is yourlast night in friendly territory. Tomorrow you cross the border intoSouth Vietnam and have to beespecially alert, for the rumorshave been heavy concerning enemy activity in the area you areabout to enter.

Reports from stragglers andcasualties from other units thathave preceded you speak of theambushes, the devastating firepower, malaria, and the wellarmed enemy soldier everywhere.Your thoughts flash back to thedetailed briefings and the carefulplanning that you went throughbefore leaving North Vietnam.2

Lieutenant Colonel Kenneth D. MertelYou know your rou tes across theborder are secure, carefully hidden from the enemy, from hissearching aerial eyes. The waystations are carefully placed andprestocked with food, medicineand ammunition, and are nearwater and shelter. The excellentsystem of native guides will takeyou over the carefully selectedroutes. Better get some sleep, fortomorrow will be a busy day.How busy you little know as youdrift off for a few hours of peaceful rest, the last that you will everknow.

Across the border the nextmorning into the heavy jungle.The trails are good-you canmove rapidly, two abreast un derthe thick canopy, and it is easygoing for the bicycles and cartsthat are moving some of yourheavy equipment. By mid-morning, in spite of your rapid movement you realize something hasbeen bothering you an awareness that you are being watchedby unseen eyes-the faint noise ofaircraft or truck engines fromafar-the occasional sight of an

enemy helicopter through thebreaks in the heavy jungle canopy.

With darkness approaching,your lead reconnaissance elementssend back word that the first waystation has been reached. N othing remains but burned out ricestorage huts; the tobacco is destroyed, the ammunition gone.Evidence of recent enemy troops,empty food containers, as well asother indications that Americansoldiers ha ve been there. ManyGI boot marks in the soft soil.

This report is very disturbingbu t no great problem, for yourmen are carrying adequate foodand you can replenish your supply tomorrow night. You spend asleepless and nervous night as anoccasional round of artillery ormortar fire explodes in the darkness-not far away, just enoughnoise to keep you partially awake.Airplanes overhead and bombsOL Mertel s with the Direct-orate of Individual TngJ Office ofthe Deputy Chief of Staff for Per-sonnelJ Dept of the ArmYJ Wash-ingtonJ D C.

U. S ARMY AVIATION IGEST


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narmed Huey seeks out the enemy in Vietnamfalling in the distance-hard torealize that the enemy is so near.

Next morning, moving a littlemore cautiously-still good concealment. A few minutes later asone of your elements cross a relatively open area it is brought under fire by two helicopters firingmachineguns and rockets. Yourmen take cover but not beforeseveral have been killed orwounded. Where did the helicopters come from? How did theyspot you? Approaching a secondway station, back comes a reportno food nothing but debris and

GI boot tracks. Another sleeplessnight, harassing artillery fire fallsclose at hand; two men arewounded.

Moving the next day slowereven more carefully-you are beginning to see helicopters everywhere. One of your lead patrolsencounters a small enemy forcewhich melts away before yourmen can open fire. Several timesyou have had to take cover fromlow -fiying helicopters little onesdarting in and out of the treesright in the treetops. They shootat anything that moves or looksAUGUST 1967

suspicious. Later on in the day asyou cross a stream, part of yourunit is bombed and strafed byfast flying aircraft. More casualties?

Another way station that nightwith little food remaining. Nowyour troops are nervous hungry morale is getting low. More harassing artillery and mortar fireduring the night. Seems to be getting more accurate. The next dayyour lead company is ambushed.They walked right into a carefully laid trap just like a groupof recruits. Before you can assistthem with the remainder of thebattalion, you are under attackby an air strike-bombs, napalm,rockets and machineguns searching out your troops. The sky isfull of helicopters. The enemyseems to be landing everywhere;they are all around you. The firepower is unbelievable, they seemto know exactly where you areeach one of your elements is pinpointed. Every time you movethey counter with a helicopterborne troop force much quickerthan you can react and you arecaught once more.

There is not much time leftthere is Ii ttle left of your battalion. You cannot comprehend,but you have encountered U. SArmy airmobility. This is a highly successful concept proved inVietnam, with troops moved almost anywhere, rapidly with littleconcern for terrain or weather;tremendous firepower instantlyavailable; outstanding communica tions command and control;excellent logistics and superb intelligence and reconnaissance.

Let s now go back and analyzehow the airmobile forces wereable to locate you so easily andbring their vast combat power tobear so rapidly and effectively.

In an airmobile infantry unitin Vietnam today in elligenceand reconnaissance always a difficult problem in the past havebeen improved to the point wherethe enemy is located more rapidlythan ever before in a counterinsurgency environment. This factis evidenced by the increasingnumbers of Viet Cong (Ve) andNVA troops killed wounded, captured or defecting.


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pany commanders after the battalion order is issued is extremelyvaluable if time permits. Part ofyour reconnaissance if any air as-sault will be conducted must jnclude the aviation company orbattalion commander who willsupport you. Ris recommendations on landing zones, routes,etc., a re essential.

An operation may begin withan air cavalry troop operationalcontrol under your brigade. f so,this unit is the best overt meansof locating the enemy within thedivision. The White Team twoOR-13 helicopters, is most effective. This scout team works inthe treetops, flitting about searching out the trails, way stations,bunkers and caves by means ofvisual observation and reconnaissance by fire, using both 7.62 mmmachineguns and 2.75 rocketsmounted on the helicopter. Theycover each other as they work.

f something suspicious is developed beyond their capability,they call for the helicopter gunships in the Red Team. TheseUR-1B helicopters, armed withrockets and machineguns, are excellent for developing a vagueenemy situation. f troops areneeded on the ground the BlueTeam an infantry rifle platoonmounted on its own UR-lD transports, can land and physicallysearch out the terrain. Many ofthe successful battles of the warhave been developed in this manner.

White Red and Blue Teams ofthe air cavalry troop, backed upby an infantry battalion-yourbattalion. Enemy discovered, inyou go, with whatever forces arerequired to relieve the air cavalryand destroy the enemy.Prisoners of war (PW) or VietCong captives (VCC) are a fruitful source of information and intelligence. Once an NVA or VCsoldier is captured or surrenders,he feels that he is out of the warAUGUST 1967

and will spill his guts . A carefully conducted psychological warfare program using leaflets andloudspeakers will help provideprisoners. Many units offer a caseof beer or an R&R for a prisoner.This will give good results in theearly phase of an operation whenthe capture of prisoners is mostcritical.

Interrogation of VCC in theearly phase of the 1st Air CavDiv's Pleiku Campaign Oct-Nov1965, supplied detailed order ofbattle information to completethe picture of a newly infiltratedNVA regiment. A VCC capturedon 4 Nov 65 in an ambush provided the first indication of thepresence of another NVA regiment which was subsequently located and soundly defeated on14 17 Nov at Chu Pong. As theoperation progressed, order ofbattle developed additional forces.By 24 Nov it was determinedthat an enemy division had beenengaged by the Sky Troopers ofthe 1st Air Cavalry.Most NVA captives answerquestions willingly, indicatingthat they have had little or notraining in a code of conduct.They are also unaware of the usefulness of information given. Forexample, several told of theircompany locations. An air strike

Prisoners above) can be an importantsource of information. Below a VietCong prisoner eats lunch after receivingirst aid treatment from a medical aidman

on 100 NVA in one of these locations resulted in 80 KIA. Eightother captives revealed the location of resupply points whichwere struck by air and artillery.Secondary explosions occurredfive times out of eight air strikes.In operation White Wing conducted in Jan-Mar 1966 in BongSong, documents and prisonersconfirmed the presence of anNVA division in the province.Rapid exploitation of information given by a captured battalion

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Find th Enemy Airmobile Style

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Troops may be inserted by helicopter above) to establish companysize bases from which observers can obtain inform tion on enemymovements and positionscommander assisted in raising theenemy death count. Live broad-casts by a captive lieutenant re-sulted in at least one defection.In Operation Lincoln MosbyMar-Apr 1966 conducted in theII ARNV Corps Tactical Zone17 VCC identified 15 separateunits as being in the area. Out ofthese three new infiltrationgroups two newly infiltratedNVA regiments and one engineercompany were confirmed. Againprisoners and captured documentswere invaluable in the discoveryof lines of communications andstorage depots and further indi-cations were evident of majorroutes of infiltration.Documents are a valuable source

of information and intelligence.The VC and NVA are great plan-ners everything worked out to thelast detail in advance. Careful re-hearsals are staged for almost ev-ery operation. Thus most of theirplanning is reduced to writing onpaper. Maps and sketches areplentiful. All enemy bodies mustbe carefully searched for usefuldocuments as well as searchingfor bivouac sites caves etc. Allpaper found must be turned insince in the absence of linguiststhe average U. S. soldier will notbe aware of the value of the docu-ment. The abundance of helicop-ters in the area makes it easy toget documents for evaluation backto the rear to the S 2 types rapidly


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before the enemy knows that apending operation has been comprised. The finding of a sketchmap early in the Pleiku Campaign of the 1st Air Cav Div, OctNov 1965, provided the enemyroutes of movement and locationsof supply points and aid stations.

During Operation White Wingin Feb 66, the 1/ 9 Air CavalrySquadron found a map on anNVA body. Four circles weredrawn around locations in whatis called the Crow's Foot. A callto division revealed that thesenumbers corresponded to unitsof an NVA regimen . A search ofone of these areas resulted in 63NVA killed in a brief battle andthe capture of a battalion commander. The battalion commander's interrogation led to the location of his regimental headquarters and the capture of many morevaluable documents.

In Operation Crazy Horse, MayJun 1966, in Binh Dinh Province,over 75 linear inches of documents were captured, giving theintelligence community an invaluable insight into the VC infrastructure in that area. Rapid interchange of information betweenmultinational Free Wor ld Forcesproduced intelligence that resuIted in locating and destroyingenemy elements.You may employ long range patrols, landed by helicopter or byparachute, to search a specificarea, several days in advance ofan assault. Every infantry battalion should have this capabilitywell developed within the battalion reconnaissance platoon andwithin each rifle company. Someunits give their long range patrolsfancy names and scrounge speciallightweight equipment that willpermit them to operate off theland for several days without resupply.

Excellent communications areessential to receive reports and toretrieve the patrol in the event ofAUGUST 1967

emergency. The CH-47 Chinookhelicopter is excellent for recovering patrols, day or night, usingthe ladder techniques. f you areoperating in an area and expectto come back, it is a good idea toestablish caches of food and ammunition, carefully hidden, butsecretly marked so that they canbe located, for the use of longrange patrols at a later date.

Once the air assault is over andyou are in the area, the use of patrols becomes the best method ofobtaining information and intelligence-to locate the enemy. Thismay be accomplished by sendingout rifle companies to establish abase, then dispatch small patrolson coordinated routes from thatbase. The patrols can be insertedby helicopter and retrieved laterat a predetermined location andtime. Many units have devisedtypes of patrol techniques thatthey have given special names to,such as checker board, scatter, and saturation ; however,they are really the same old triedand true methods that have beentaught and practiced in two previous wars.

Most important, any time a patrol is out, either reconnaissance,stay behind or combat, carefulplans must be prepared to provide fire support and reinforcements or retrieva l. Small unit operations from squad to platoon,off by themselves, must be a verycarefully planned operation for,generally speaking, no unit lessthan a company size combat teamcan really take care of itself in asustained combat action againstthe enemy. Company and battalion commanders must know wheretheir patrols are located at alltimes and be prepared to helpthem should the need arise.

When a company or battalionis moving overland, patrols mustbe used in advance, rear and onthe flanks, even in the jungle.Otherwise, if you lack proper se

curity, you will be surprised andambushed. Liberal use of the helicopter scouts from the air cavalrysquadron or your own brigadeaviation section can provide agreat amount of warning and protection. The enemy invariablyreveals his location by shooting atthe choppers.Most divisions operate a Combat Intelligence CoordinationCenter (CICC), not unlike theFire Support Coordination Center (FSCC). All information,documents and PW reports funnel into the CICC from all units.Here the information is easilytranslated into intelligence by theexperts and then is made available to the combat units to helpthem in their mission to destroythe enemy. The vast amounts ')finformation obtained through themany sources can be sifted andevaluated quickly to provide resuIts of value to the combat units.f the division has not established

such a system, the brigade mayoperate a CICC equally as well.

Good intelligence and reconnaissance is the difference betweensuccess and failure in Vietnamtoday. It is the primary factor inobtaining a favorable friendlyversus-enemy kill ratio. When onehears of a U. S. unit being ambushed or surprised at any location where they are based or se-cured for the night, there is littledoubt that their intelligence andreconnaissance were faulty in spiteof the many means and facilitiesavailable to them. Surprise orambush gained by the enemymeans that the enemy had goodintelligence and knew exactlywhat the U. S. unit was doing.Our Army today has excellentmethods and facilities for gathering information and producingintelligence. Use them for greatersuccess in battle and improvedperformance of the Infantry mission to close with and destroy theenemy.


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simplE protE ctivE rE VE tmE ntfor parkE d army aircraft

I NFORMATION from Vietnam indicates that increasingemphasis is being placed on construction of a protective revetment for parked Army aircraft.And why not? For a few dollarsthe Viet Cong can fabricate abomb that can inflict heavy damage on an unprotected aircraft tothe tune of thousands of dollars.The economics of this is quitesimple, and balances heavily infavor of the VC. We may be arich nation, but sooner or later,with continued damage of parked

PLAN VIEW

Figure 1

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ajor Vincent R Ritts

aircraft we ll begin to feel thepinch in our pocketbook. Worseyet, vitally needed aircraft willnot be available when needed.

I f a relatively simple protectiverevetment is constructed so parkedaircraft can receive some protection from enemy attack, this unnecessary damage can be avoided,or at least lessened. The questionis, How to build it? What s it madeof? How much is needed? Whocan build it? Obviously there arelrmumerable types of protectionthat can be built. TB 5-330-1 is a

REVETMENT

ST NDOFF

r 1/. lJ J m }}} }}J j

SECTION A A

relatively comprehensive bulletinon the subject, and with somestudying of it a type fortificationfor a specific need can be calculated.

First thing to decide is whattype ammumtIOn to protectagainst: ball, recoilless rifle and/or mortar, and what size. Afterdetermining that, find out whattype construction material is available (soil, sand, clay, concrete,timber, etc.). Then decide whether or not a standoff should beused. A standoff is a steel or timber wall erected about 6 feet infront of the protective structureto detonate shells to reduce thepenetrating effect. Standoffs aredesirable because they greatly reduce the required thickness of theprotective structure, thus economizing on time and materials.Once all the above is investigatedand considered, the best materialwith which to construct the fortification and the thickness of thestructure should be determined.

Now it s time to decide on whatM J Ritts s Deputy Branch

h i e f ~ Fixed Wing Branch, Em-ployment Division, Dept of Tac-tics, Ft Rucker Ala.

U. S ARMY AVIATION DIGEST


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type of protective revetment tobuild: sandbag revetment withstandoff, free standing wall, etc.The materials available and especially the labor force and technical ability will govern this. Without going any further, and intotoo much detail, since specificsituations can be gleaned fromthe TB, this article will presenta type revetment for parked UHIA and B aircraft it) Vietnam.The design is relatively simpleand is constructed with materialsreasonably available in RVN. Itcould be constructed by nonengineer troops; however, technical supervision by engineer technicians is desirable. This designshows a partial protection revetmen . Here, time and economy ofmaterials were weighed againstpossible consequences of an attackwith resulting damage to the aircraft. The design uses sandbagjsoil-cement fill with a Y2 thicktimber sta,ndoff. This will providepartial lateral protection against.50 caliber ball (AP) , 82 mm recoilless rifle, and 120 mm mortarammunition. The use of soil ce-ment in the sandbags reduces thebasic problem of rapid deterioration of sandbags. A soil-cementstructure also eliminates the needfor a retaining wall, thus simplifying the construction. It must bekept in mind, however, that asandbag soil-cement revetmenteliminates the need for a retaining wall through the interlockingarrangement of the sandbags; afact which must be adhered toduring construction.

Figure 1 shows the layout ofthe revetment. This small Ushaped design economizes on materials but requires ground handling of the aircraft into and outof it. Its height also affords littleprotection for the main rotorblades and rotor head. This is acalculated risk that must be taken.A higher revetment could be constructed, but with correspondingAUGUST 1967

FOOTER MAY BE NECESSARYIN LOW BEARING SOILS

A

Figure 2

increase in costs and time required for construction.Figure 2 shows the design of thesoil-cement revetment. I f a greaterheight is desired, the 2-foot minimum thickness must be maintained to afford the same ammuni tion protection. The 1: 10 slopemust be maintained to preventthe wall from collapsing. Be surethe soil can support a higher wall;otherwise, a footer may be required.

Figure 3 shows the timberstandoff design. Quarter-inch steelplate could be substituted for thetimber, but this material probably

Figure 3

1 2--1- - -

SECTION A-A

would be more difficult to obtain.Many other type structurescould be used, such as filled 55

gallon drums, combinations withpierced steel planking, salvagedequipment, etc. TB 5-330-1 contains comprehensive informationfor a do-it-yourself revetment,and should be consulted bdoreattempting to design a specifictype for your needs. For a fewdollars spent, considerable savingscould result in sparing damage toparked aircraft. The old saying

An ounce of prevention is wortha pound of cure applies verywell in this case.CONDITIONm

,,, ' x RL x RWSTRUCT GRADE INTERMEDIATE

~ ~ BRACELU MB ER BRACE AS REQUIRED

/, TIMBER STANDOFF.

NOTES: MAKE EACH SECTIONINDEPENDENT OFADJACENT SECTION .LOG POST(40) ORWIRE ROPE ( '/2 0)MAY BE SUBSTITUTEDFOR 2 x 6 BRACE .

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P SSING THE WE THER BUCKBlaming the weather for the loss of lives and destructionof perfectly good aircraft in thunderstorms s too oftenthe easy way out

Captain Robert D Kelley and Mr Cletus N Youmans

M ANY AVIATORS blamethe weather for the loss oflives and destruction of perfectlygood aircraft in thunderstorms.This is just a way of passing theweather buck. The real culpritis not the weather but the pilotwho tries to fly through it.

Pilots who for some reasonhave flown through a thunder-storm often say they didn't knowthere was a thunderstorm in thearea until they were in it. Whenthis happens they generally blamethe weather service. The fault,though, is probably their own because they failed to check or failedto realize the significance of whatthey heard the weatherman say.

No country in the world doesas much weather-wise for its pilotsas does the United States. Thereis hardly any place in the UnitedStates the aviator can be that hecan't get the weather informationhe needs to make his flight plans.

The government has establishedFlight Service Stations, locatedwi thin 75 to 80 miles of eachother, to give weather informa-tion to v i t o r s ~ There's an impressive amount of informationto be had from them, and it's allfree for the asking. An Army pilotonly has to pIck up a telephoneand call them collect, or if he'sairborne call on his radio.Also, military pilots may contact any military airfield with aweather station to obtain information. f necessary, the pilot canalso contact a nearby radio station, TV station, or newspaper10

and get a nonaviation type, butusable, weather report from thenews teletype lines.There are times, of course, that

the aviator may not be able toget the weather information allthe way. Most Flight Service Stations and other weather sourcescan only give point to point forecasts. IV[any stations don't havethe necessary weather radar andother equipment necessary to getthe information themselves.Sometimes the existence of athunderstorm may not be knownby the station. Thunderstormscan build up quickly and weatherstations can't tell where they willbe until they appear. It oftenhappens that after a pilot hasbeen told there are no thunder-storms in an area, one appears.

f an Army aviator can't getthe en route forecast he wantsand he has reason to suspect thun-derstorms, he must rely on visualmeans of spotting them. Armyaircraft usually don't have weatherradar on board.

From a distance, locating athunderstorm is not easy. Thetall cumulus cloud may be buriedin other clouds or look quite different from far away. A cumuluscloud looks much like a cauliflower with rolled puffy lookingsides. As the storm grows the topwill spread out in the directionthe storm is moving.

In front of the thunderstormcloud and near its base a turbu-ltnt cloud will sometimes appear.It usually extends downward from

the main base. This is known asthe roll or squall cloud. Thiscloud is caused by the agitationbetween a rapidly rising currentin advance of the storm and astrong downdraft coming out ofthe storm. Its appearance indicates very rough weather withinthe storm.

Aircraft, especially light ones,should avoid this roll cloud if atall possible. I t has the power tohurl an aircraft into the thick ofthe storm. Also it's unwise to tryto fly under this cloud. Suddenchanges in wind direction andspeed set off by the roll cloud maychange flying conditions and flightaltitude so rapidly that the aviator may not be able to maintaincontrol.

But suppose the aviator findshimself in a thunderstorm whetherhe wants to or not. What is thetechnique he should use that offers him the best chance of survival?

First thing to remember is thatonce started, continue on. Don'tturn back. To turn around onlymeans that it's necessary to gothrough most of the storm again.

Speed is very important. Goingtoo fast will cause structural damage to the aircraft because of thegust loads that will be encountered. Too slow a speed will cause

CPT Kelley is currently servingin VietnamMr Youmans s an education spe-cialist at Hunter AAF Ga



13/68

the pilot to lose control of theaircraft. The 10 gives the bestspeed for each aircraft. f itdoesn t, figure the best to be about20 percen t less than normal cru s-ing speed.The aircraft should be cleanedup as much as possible to make itrespond quicker when extra spee.dis needed. Retractable landinggear should be retracted. How-ever, the landing gear can belowered to slow the aircraft whenreduced speed is needed. The gearshould be raised again as soon asthe correct speed has been reached.

Wings of the aircraft should bekept as level as possible to aid inmaintaining a heading. Altitudeshould be considered of least importance so as to avoid excessivepitch.

The best altitude for enteringthe storm is about 4,000 to 5,000feet above the terrain. This ishigh enough to take care of thedowndrafts and yet keep the air-AUGUST 1967

craft out of the high speed gustsfound higher.

At 10,000 to 12,000 feet hail andice are usually found, so these altitudes are very dangerous. Therewill be considerable lightningflashes. The ou tlines of the maincells can be seen and it s best toavoid them. The cockpit lightsshould be turned up bright toavoid blinding.

Thunderstorms are one of thegreatest hazards to aviation. Thebest advice that can be given toan aviator is to avoid them. Toavoid a thunderstorm a goodflight plan is needed. It shouldtake into account not only theweather as it is bu t also as itcould develop. Once it becomesnecessary to go through a thun-derstorm, the pilot should pick anarea with the fewest probableweather troubles, take the shortest route through, and hold thecourse until he comes out on theother side. . . . . . .

Weather frequently forms during the dayabove) and erupts violently t night be-low)/ with brilliant flashes such as theserecently seen over an Francisco

11


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The Army s new CH-47B Chinook lifts an M-56 self-propelled Scorpion gun which weighs 14 800 pounds

ere omes the CH 47BT HINK OF Vietnam and youthink of the helicopter. Thinkof the helicopter and among thosethat immediately come to mind isthe CH-47A Chinook.Since its arrival in SoutheastAsia in September 1965, the tandem-rotor aircraft has been one ofthe mainstays of the Army s aerialassault against the enemy. Now ithas passed its 56,000th flight hourin Vietnam.

In accumulating these hours,the Chinook flew over 148,600sorties and was called upon dayafter day to carry out a hugevariety of missions. During thefirst 17 months of operation inVietnam, Chinooks have transported over 1,094,000,000 poundsof cargo and moved 415,000 troopsand civilians. A number of Chi-12

nooks have been deployed to thatwar-wracked country.In the field of aircraft recovery,the big helicopters have retrieved

downed aircraft, both rotary andfixed wing. Replacement costs ofthese aircraft total nearly 300,-000,000.The records show there s no

doubt that the Chinook is good.Now it will be even better. TheCH-47B is in production, the result of the Army's greater requirements. The first production CH-47B was delivered in May ofthis year. This is the first phaseof a planned two-step programthat would provide a significantpayload and speed increase overthe Chinook now in Vietnam.

The current Chinook grossweight was expanded from 33,000

to 38,550 pounds for the CH-47B.Cruise speed of the CH-4 7A is 130knots and was increased to 155knots for the CH-47B. Operatingunder sea-level standard conditions, with a full fuel load, theCH-47B payload capability is14,500 pounds. This represents a42 percent increase over theCH-47A Chinook payload capability. The CH-47B Chinook hasa 60 percent increase in productivity when operating under combat conditions.

Changes in the CH-47B Chinooks will include the incorporation of the T55-L-7C Lycomingengine. This results in an increaseof horsepower available from 2,650to 2,850. In addition to increasedpower capability, the CH-47B incorporates a new rotor system



15/68

that provides rotor blades with awider chord and a cambered airfoil.Popular ly nicknamed the

Droop Snoot, the rotor systemprovides a significant improvement in aerodynamic capability.This, in turn, allows the speedand lift capability increases. Theblade has also gone to a honeycomb core, adding to its strength.

Al though the specification ofCH-47B vibration levels have beenmet, Boeing-Vertol, manufacturerof the Chinooks, and the U. SArmy have conducted additionalflight tests and shake tests to correct pilot complaints of vibrationlevels in the forward cockpit.These complaints were largelycaused by a high-frequency buzzat the pilot heel slides and threeper rev of the instrument panel.

As an aid to cu tting down thisvibration and making the Chinook more stable, four absorberswere tested in a prototype. Twowere placed aft, the others forward. A gO-pound weight, set onsprings, was in each, making themapproximately 120 pounds wheninstalled.

Minor visual changes are alsoincorporated into the CH-47B.Among these are the blunting ofthe aft pylon and the inclusionof aft strakes. In addition, fourspoilers have been added to theforward pylon. These additionsmake the aircraft almost staticallystable in the directional mode.

The CH-47B is a forerunner ofthe CH-47C Chinook configuration now under consideration.The CH-47C would contain additional changes, including installation of new T55-L-Il Lycomingengines wi th a horsepower of3,750 and strengthened transmission components to accommodatethe increased power. It wouldhave a multi-fuel capability, andits gross weight would be 44,000pounds.AUGUST 1967

The CH-47B does riot incorporate many visual changes over the CH-47A. However, anoticeable change was made on the tail, which was blunted. Above, a CH-47B ft pylonforeground) can be compared with the A model beside it. Another change includes theaddition of aft strakes see arrows in photo below)


16/68


17/68

In addition to the three agencies mentioned, a number of otherArmy agencies perform researchrelated to human factors. Forexample, at Fort Rucker the U. SArmy Aeromedical Research Unit(USAARU) and the U. S ArmyBoard for Aviation Accident Research (USABAAR) have programs in the human factors area.The collocation of these agenciesand HumRRO Division No.6 atFort Rucker provides the opportunity for considerable interaction among the various humanfactors efforts. Guidance procedures for the conduct and coordination of the Army human factorsresearch program are set forth inAR 70-8.

The Aviation Division ofHumRRO began as a detachmentof the Trainipg Methods Division of HumRRO at Fort Ruckerin 1956. In 1958 it became a {ullfledged research division ofHumRRO and is presently authorized a strength of 14 researchpersonnel. Collocated with theHumRRO Division is the U. SArmy Aviation Human ResearchUnit (USAAVNHRU), a military unit which is authorizedthree rated officers and ten enlisted personnel.

The aim of the HumRRO aviation research program has beena simple one: to provide information basic to improvements in training and performance in Armyaviation systems. Research ontraining is one of the most important aspects of human factorsresearch, because training is theprocess in which human resourcesand hardware resources arebrought together to produce operational man-machine systems.

One of the first problems facedby training r e s e ~ r c h e r s one thatwas stated by DA as a mustresearch requirement, was that ofdeveloping a more objectivemethod of assessing flight performance. This general area of re-AUGUST 1967

search, performance assessment,has been an important part of theHumRRO aviation research program through the first decade ofits existence. Early experimentalstudies in 1957-58 indicated thatflight grading was so unreliablethat correlations between independently administered measuresof flight performance for the samestudents were little or no betterthan zero. As a result, HumRROdeveloped the Pilot PerformanceDescription Record (PPDR)which provides a more objectivemethod of measuring helicopterflight proficiency. The PPDRsystem has been in operationaluse at the U. S Army PrimaryHelicopter School (USAPHS) forabout seven years now and is usedfor all checkrides there.

The PPDR is not a magic instrument, in spite of its being sodescribed in a recent magazine.It is merely an objective listing ofthe performances the student exhibits while carrying out Hightmaneuvers. Use of the PPDR doesresult in standardizing what isobserved, the sequence of events,and the information collectedall of which tend to increase grading reliability.

This standardized collection ofdetailed objective informationmade possible the development ofa training quality c o n t r ~ l systemin a subsequent phase of the research. This system, which makesheavy use of machine processingof checkride information, hasproved to be a valuable tool forUSAPHS management in terms ofassessing the overall operation ofthe training program and indicating the need for specific changesin instructional or checkride practices.

Another area of continuing research interest has been thatof aerial observation. In 1957HumRRO Division No. 6 embarked on a series of research studies aimed at developing a train-

ing program for aerial observers.Research showed that existingtraining was doing an adequatejob, except in four critical skillareas-visual search, target recognition, geographic orientation,and target location. Experimentaltraining concepts developed forthose four areas during the courseof the research were adopted bythe Army in FM 1-80 in 1962.

Subsequent to development ofthe observer training program described, the Army requested thatresearch be undertaken to developa programed text version of theobserver training program tofacilitate training in field units.The programed texts developedhave just been published by theArmy as TM 1-380- (1-6). Plansare currently being formulatedfor a joint effort by the Department of Tactics, USAAVNS, andHumRRO to integrate some ofthe lessons learned from Vietnam operations into the documentary materials available foruse in observer training.

Training devices have been thefocus for another important areaof research. HumRRO DivisionNo. 6 has participated withUSAAVNS and with the U. SArmy Aviation Test Board intesting a number of Hight training devices during the past eightyears. From the human factorspoint of view, there is one overriding consideration in evaluatinga , Hight training device: does thedevice produce learning of desired skills which can be shownto transfer to the actual Hightsituation? f this requirementcannot be met, all other aspectsof the device-cost, maintenance,etc.-do not matter. The devicemust fulfill its primary function,that of producing useful skillsthat transfer.

The training device researchprogram has been aimed at identifying those aspects or characteristics of devices which are critical

15


18/68

/

officer training, its concern wi thcareer factors introduces a newdimension in the HumRRO aviation research program.

umRRO personnel study the Whirlymite a primary rotary wing trainer

The study of career factorsillustrates the extension of humanfactors research to a broad personnel subsystem context. It alsoillustrates the fact that whilemost HumRRO research is related to training and, hence, toschool and USCONARC interests,the program is Army-wide in itsorientation. Thus the researcheffort is geared to requirements inaddition to those of USAPHS,USAAVNS, and USCONARC.For example, HumRRO DivisionNo.6 provided the human factorsinput for the recent Combat Developments Command (CDC)study of aerial reconnaissance andsurveillance systems for the 1975time frame, TARS-75. Human factors inputs are routinely made tomost CDC Aviation Agency documents and studies.

to the transfer of training. Onlywhen such relationships are understood and the training requirements are carefully analyzed canwe be assured of receivin.g deviceswhich will do their intended jobat the least cost.

Several recent training deviceresearch projects are of currentinterest. In one, a study was conducted using a contact hoveringtrainer, the Whirlymite, for primary rotary wing training. Thisdevice-an actual, flyable, oneman helicopter mounted on aground effects machine platform-produced a substantial reduction in primary flight attrition.VSAPHS is purchasing 15 suchdevices for operational use in theprimary flight program. In a second activity, HumRRO DivisionNo. 6 developed, at the requestof USAAVNS, an SDR (smalldevelopment requirements) for aSynthetic Flight Training System(SFTS). This system of deviceswould be used, both at USAAVNSand in the field, for initial rotarywing instrument training, fortransi tion training, and for maintenance of proficiency. The SFTSwill incorporate such advances insimulation as modular concepts,digital computation automationof many instructor functions,adaptive training, and automation of instruction programs. Thepossibilities of effecting substantial financial savings in connection with flight training and proficiency maintenance programs16

are of considerable importance.The research activities describedthus far have concentrated on observer and pilot training problems. The current year s programhas seen the introduction of research on aviation maintenance

training. Data collected byHumRRO Division No.6 for therecent DA study of the Army logistics system pointed up a comingshortage of experienced mechanics, particularly in MOS 67N20.This shortage is occasioned by therapid buildup in the inventory ofUH-l and OH-6 aircraft duringcoming years coupled with lowreenlistment rates for aviationmechanics. In view of the criticalrole which the aviation mechanicplays in Army aviation, the research is aimed at developingtechniques for maximizing theextent to which training is directly responsive to major fieldrequirements. Without doubt theaviation mechanic is one of themost important links in the chainof human factors which supportsArmy aviation operations, and research on main tenance training isof extreme importance.

The human factors researchprogram does not treat only theproblems related directly to training. A current study, concernedwith the warrant officer aviator,lays heavy stress on the importance of various attitudinal andmotivational factors in careerplanning. While this study alsotreats many aspects of warrant

In the early days of Army aviation it was assumed that the factorwhich makes man unique hisgreat inherent flexibility andadaptibility, would allow him toovercome deficiencies in aviationtraining and systems design. However, as the overall systems andinteractions with other systemshave grown more and more complex, it has become increasinglynecessary to plan for the humanfactor in the system. Otherwise,we will not take maximum advantage of human capabilitiesand will place requirements onthe human component which cannot be met. The human resourcesof Army aviation are its most precious reSOl-lrCeS and the humanfactor must be given preeminentconsideration from the design ofaircraft, through the selection andtraining of personnel, to the operational employment of Armyaviation. These past 25 years haveseen great strides in this regard;the next 25 cannot afford less.

U. S. ARMY AVIATION DIGEST


19/68

DIT HI GE H IQUES

Ditching Should Have s Many Or More Survivors Than Forced landingN 1960 a Bri tish study was published that in-. eluded a summary of all reported free worldhelicopter ditchings up to that time. The studysaid: Helicopters of the United States Army are

rarely flown over water and there have been nocases of ditching by .that service.Since that report was published, we have becomethe world's largest user of helicopters and are nowflying them more and more over large bodies ofwater.We can no longer say we have had no ditchings.Between I January 1960 and 31 January 1966, we

had 4 fixed wing and 5 rotary wing ditchings. Today every Army aviator can expect to be calledupon to fly over large bodies of water and for thisreason must know ditching procedures for hisparticular aircraft.

PREPARING TO DITCHThe time to prepare for the unexpected is notwhen it happens but before the event occurs. Like-wise, the time to prepare to ditch is not in the air

after it becomes necessary but on the ground beforetaking off Most ditchings occur without warning.In these instances there simply is not enough tiineto think about everything that must be done tomake the di tch a success.Everyone on board the aircraft should knowwhat he is to do and how it will be accomplishedif it becomes necessary to ditch. The crew, ofcourse, will have certain duties before and afterthe di tching, bu t passengers can be used as abackup in case one of the crewmembers is injuredat impact. Helicopters are more likely to overturnin the water during the ditching sequence thanfixed wing aircraft, so the occupants must preparefor this.Passengers should be instructed ' in the use of allemergency equipment before the flight gets under-AUGUST 1967

way. This is especially important if the airport be-ing used is like the New Orleans Lakefroni wherethe aircraft takes off and lands over water. This isalso the time to ins truct passengers in the propersitting position during the ditch. The Navy teachesthat placing your back against the bulkhead, facingaway from the direction of flight, is the best posi-tion. The Coast Guard advises that the best posi-tion for an individual obviously is strapped in asecure seat. A person in a forward facing seatequipped with a lap belt but no shoulder harnessshould bend forward and cover his head wi th hisarms. f it is necessary to sit on the deck, paddingbetween the person and bulkhead are recommended.All passengers and crewmembers must be toldthat as soon as ditching becomes imminent theyshould remove from their person ties, eyeglasses,sharp objects, and any other items that might causeinjury during impact. Crewmembers should alsomake sure that all toolboxes, cargo, and loose equip-ment are secured against impact forces encounteredin a forced landing.Before taking off the aviator should review theditching characteristics of the aircraft he is to flyDoes it have good ditching qualities, or is it likelyto nose over upon contact or sink into the brinydeep within seconds? Will adequate emergencyequipment be on board?

What about passengers on board? Will old peo-ple, wounded soldiers, women and children be onboard who may not be capable of surviving in thewater? Are life rafts available?Obviously all of these things can t be consideredin the few seconds you have in an emergency ditch-ing situation. For this reason it's best to take a fewminutes longer in making your preflight plan toreview all these factors before takeoff.Faced with an emergency over water, the hardestdecision to make is whether to ditch or not. Often

17


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itching Techniquesthis decision is made for you by the aircraft enginejust quitting, leaving nowhere to go but into thewater. But at other times you will have to decideif you should carry on and risk the possibility ofditching without power or ditching while you stillhave control of the aircraft. The Coast Guardrecommends that the following general rules beconsidered when ditching: Ditch while power is still available. Ditch in daylight if possible. Ditch beside a vessel i possible. f flying in the vicinity of a coastline or island,and a crash landing is inadvisable, di tch in the leeof land.

At that critical time you are the only person whoknows the variables. About the best advice thatcan be given is that if you know you are going tohave to ditch, you should do so when ditching presents the best chance of survival for you, your crew,and your passengers.In making the decision to ditch or to fly as longas possible in hopes of getting nearer or reachingland, consider the difficulty of rescue. Are shipsnearby that can make a rescue within minutes or isthe ditching site far from help?Then there are the weather conditions. Are thewaves high and bad weather brewing? What is thetemperature of the water and the air?

f land is near what about the terrain? Is it flatand relatively free of obstacles? Or is it mountain-ous or rocky, offering iittle hope of a safe landing?

During preflight planning a good suggestion isto break up the trip into half-hour parts and consider each part as a separate trip. In each part coilsider all the above factors as much as you can inadvance. After deciding what your ditching policywill be in each part, stick to that decision unlesssomething happens to drastically change the situa

~ i o n For instance, the weather might worsen, causIng seas that are harder to survive in, or the aircraftmight ca. tch fire making it necessary to ditch regardless of other decisions.

LIFE JACKETS AND RAFTSBefore starting off on a flight you should decideif it is necessary to carry overwater lifesaving equipment. Like the British report said, we operate in a

land environment. Since we use our aircraft onshort fields, they are comparatively small and havelimited cargo space. We simply don t have room tocarry lifesaving equipment all the time.

One trip report from Vietnam said that thepilot in Vietnam is subject to fly over water whether18

it was planned or not. The same might be truein any situation where the flight route is nearwater and weather is present along the flight route.A good guide in deciding when to put overwaterlifesaving equipment on board can be found inAR 95 1 and in the rules laid down for civilian aircraft. The council of the International Civil Aviation Organization (ICAO), of which the UnitedStates is a member, says that single-engined l a ~ dplans should carry life jackets when flying morethan gliding distance from shore. Dual-engined aircraft should carry life jackets when they are beyond 30 minutes from a suitable airfield that can?e reached with only one engine. f a land planeIS to be flown more than 90 minutes single engined) or 120 minutes (dual engined) from shore,ICAO says that it must be equipped with lifejackets.

The FAA requires that U. S. Civil Air Carriersprovide individual flotation equipment for eachperson on board when operating over virtually anybody of water. This includes takeoffs, landings,holding or en rou te operations. ICAO is formulating a similar rule. The FAA also requires carriersto carry life rafts on any flight beyond 50 milesfrom shore. The Coast Guard reCOnimends thatlife r ~ f t s be carried whenever possible when flyingany dIstance from shore. Numerous ditchings haveoccurred well within the- 50 mile belt and studieshave shown that without life rafts the survival ratedrops off rapidly as distance from shore increases.One study of a 10-year record of ditching incidentsindicates almost a 100 percent survival rate withrafts at a distance of 15 miles offshore, while without life rafts it was only 30 percent.

When an aircraft is ditched and the occupantsdo not have life jackets, their chances of survivalare less than if they have life jackets. Of course, alot depends upon the condition of the water. InFigure 1 Survival n water

W TER TEMPERATURE



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40 F unstable water, a normal man in the primeof life will become rigid in approximately 5 minutesand will probably sink i f he has no life jacket (seefig 1). Under identical conditions, but with a lifejacket, a normal man can expect to live from 30minutes to 2 hours in the water. Men past theirprime and women and children are lucky if theycan stay alive in the water for 30 minutes.Of course there are exceptions to all rules. Onrecord is report of a woman who stayed alive in400 water for 13 hours without a life preserver.

In life rafts survival time may be stretched outinto days. When survivors are provided with liferafts, there is a good chance of their coming throughthe ordeal. Without life rafts, the chance of surviving is much less even though life jackets are used.

SPOTTING OBJECTS IN WATERIt is very hard to spot someone floating in a lifejacket even when the weather is perfect. f it is

anything less than perfect, it may take hours for anaircraft to spot survivors after it has arrived on thescene. Survivors in a life raft are much easier tolocate. Of course survivors in the water or in liferafts have a much better chance of being spottedif they have dye marking kits or other locatingdevices.Weather conditions will, to some extent, deter

mine the time it takes an aircraft to spot survivorsafter it has reached the general area. The type ofaircraft used will also make a difference.Chances of rescue wi thin 20 to 30 miles of landare greater than those farther out in the ocean.But even here are some difficulties-such as muddyestuaries, fog, and poor visibility.

The Coast Guard feels that a radio is the mostimportant single aid to a survivor in the water.This thought is based on the theory often advanced by survival experts that if a survivor isequipped with an operating homing and communicating device, he probably will be rescuedbefore he must rely upon much of his survivalequipment.

There is currently a DA approved small development requirement for an emergency beacon andvoice transceiver. This radio will provide downedArmy aircrew personnel with a means of transmitting homing information to Army aircraft onthe VHF I M frequency band and to Air Force andNavy search and rescue aircraft on the UHF AMband and to Air Force and Navy search and rescueaircraft on the UHF AM band. In addition thisset will provide voice communications channels onboth the VHF I M guard channel (40.5 MHz, MegaHertz) and the UHF AM international distress fre-AUGUST 1967

quency (243.0 MHz) . The transceiver will replacethe present standard AN IURC-IO radio set whichis not compatible with the homing system in Armyaircraft. The dual channel capability VHF I Mand UHF AM) will make the device compatiblewith communication/homing equipment on Armyaircraft as well as that of other services. This equipment will be small and light enough to be carriedcomfortably in standard flight and fatigue uniformsso that when ejection, bailout, or evacuation becomes necessary it will remain with the crewmember. A limited buy has already been made. Itwill be designated the AN lURe 68.

GETIING HELPOne pilot who had to ditch said that he oftenfelt lonesome while fiying over large bodies ofwater, but not as lonesome as he felt when he hadto di tch. And to tell the tru th, he had good reasonfor feeling lonesome. The oceans are mighty big;

there is much more sea area than land area.In spite of the ocean s large size, help may becloser than it would seem. There are many thousands of airplanes flying and thousands and thousands of ships plying the waters. Those capable ofassisting are required to change their course andassist those in trouble.Before any of these can come to your rescue,they must know about your misfortune. f you are

in contact with a ground station, tell them aboutit. f not, use the emergency frequency available inyour particular aircraft. Most Army aircraft haveUHF emergency 243.0 MHz and some have VHFemergency 121.5 MHz and HF emergency 8364 KHz.

At the earliest possible moment the pilot shouldrequest from ATC (or any radio facility) positionsof ships in his area. The Coast Guard maintains asystem (AMVER) for tracking thousands of shipsin the Atlantic and Pacific. Specific information onships in a given area can be provided in a matterof minutes. Merchant vessels can usually be contacted on the voice frequency 2182 KHz. U. S Navalships can be contacted on 243.0 MHz. Transoceanicaircraft should guard 243.0 or 121.5. In many areas-even well at sea-a Mayday issued on one of thesefrequencies will often be received by another unit.f the emergency is near land, the aviator shouldhead that way. f an airfield is close by he shouldhead for it, but he should go to land first and thento the airfield. He should not take a longer routeto land just because it is a route to an airfield. Thisis true even i f the land is rocky and hilly. Ditchingclose to shore is much better than ditching out atsea.

f there is no land within reach and the emer-19


22/68

itching Techniquesgency occurs close to an ocean station vessel (OSV),head toward it. f you can't reach an OSV, attemptto reach any vessel in the area. f there is a choice,make it a naval or larger commercial vessel as theseare better equipped to effect a rescue.

f no ships are in the area, head towards any airplane in the immediate vicinity. Of course, anotherland plane can't set down on the water and rescuesurvivors, but it may be able to drop life rafts andkeep track of survivors until a rescuer shows up.

READING THE SEAWhen flights are to be made over large bodies

of water, part of the preflight should be devoted tosea evaluation, selection of ditching headings, andgeneral ditching procedures. Once over the waterreevaluate the sea and your ditching headings basedon what you are now able to see first hand. Afterthat reevaluate the sea continuously every half-hourleg of the journey as long as there is enough daylight to see.

To select a ditching heading you must be ableto read the sea. Since the wind is largely responsible for waves, whitecaps, and foam, these can beused to determine the speed of the wind.A rule of thumb says that when the sea is calmor with only small waves, the wind is from 0 to 20knots. With many whitecaps the wind is 20 to 30knots. When streaks of foam appear, the wind isfrom 30 to 40 knots. When the wave crests give offspray, the wind is from 40 to 50 knots.

In reading the sea also consider the swells. Swellsare large waves that move steadily without breaking. There are two kinds-major and secondary.In between major swells are troughs or low areas.Secondary swells are found in these troughs. Sinceyou are mostly concerned with the major swells,learn to distinguish them from secondary swells.

Major swells are, of course, larger than secondaryones; you can tell the difference by comparing theirsize. f you have trouble, go up to 2,000 feet ormore and the major swells will be clearly visible.At times, the secondary swells are so small it isnecessary to be at 500 feet to see them at all.

Even when there is no local wind, there may beswells generated by distant storms. Swells are theprincipal danger when ditching. Smaller secondaryswells will usually be found running at angles tothe larger or primary swell systems.

SEA EVALUATION AT NIGHTAs soon as the sun sets and the air begins tocool, a layer of fog may form on the water. In

20

~ S E C 1

-:a.\..

7Figure 2. Circling ea Evaluationaddition, there are no dark and light areas as youhave on land to show up in the little available light.

The best bet is to get the needed informationfrom appropriate rescue units. But if this isn'tpossible, you will have to get the information someother way.You can ask some nearby surface ship for the seacondition, but often no one on board knows how tofigure a ditching heading. But they will know thespeed of the wind and the direction of the swells.The rest you can figure for yourself.Reading the sea by moonlight can be dangerous.The moon plays tricks on your vision while you areflying over water just as it does on land. All aircraftflying over water at night should carry flares whichshould be used even when there is a moon shining.

There are two acceptable ways to use a flare inevaluation of the sea. One method is called theCircling Sea Evaluation (see fig 2). The para

chute flare is set to ignite 300 feet below the airplane and dropped from 2,500 feet. After the dropturn 900 left and hold for 10 seconds. Then turnleft again until the illuminated water is visible.Decrease the rate of turn and circle the flare. Bycircling the flare you keep it in sight until it dropsinto the water or burns out. It gives a long look atthe water but since you are constantly turning, itmakes the evaluation very difficult.

In another method-the Teardrop Sea Evaluation, which is favored by the Coast Guard-thisdifficulty is eliminated but you have only a shorttime to look at the water. Again the flare is set toU. S ARMY AVIATION DIGEST


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ignite 300 feet below the aircraft and dropped from2,000 feet. Continue straight and level for 45 sec-onds and then execute a standard rate tum to theleft until you see the flare about 15 off the noseof the aircraft. You will be able to see it for thelast minute of the turn and for about 40 secondsof the straightaway (see fig. 3) .When the flare first goes off, it will look as if it isburning just aft of the cockpit. Actually it will beseveral hundred yards away. Burning flares alwayslook closer than they are, but play it safe and pass

i t to the side, well away from the aircraft. Don'tlook at the flare, but directly at the water. As soonas you pass the flare shift back to instruments.These methods can be used either in fixed wing

or rotary wing aircraft.FIXED WING DITCHING

The key to successful di tching in a fixed wingaircraft is slow speed, optimum noseup position,and correct heading. I f the airplane hits the waternose down it will tend to dive. In addition, theforce of the water will cause disastrous impact loads.

The proper attitude for ditching varies with thetype of aircraft. The Coast Guard advises thatspeed should be as slow as possible with good control and a low sink rate. The Army's lOs usuallysay moderate nose high or nose high attitude.Some unofficial publications recommend 7 to 12.But the noseup attitude can be overdone. I f theairplane comes in with the nose too high, the taildigs into the water causing the nose to slam downhard.Army airplanes with high wings are easier toland on water than those with low wings like theU-8 Seminole. This is because the wings often interfere with ditching at first contact. As far as thewings are concerned, the U-6 Beaver and U-I Otterare good initial ditchers from the standpoint oftheir slow landing speed but they have fixed landing gear which cause them to nose over.

On the other hand, low winged airplanes likethe Seminole tend to float longer. This is becausethe wings rest on the water, adding buoyancy andhelping to stabilize the aircraft.

It is generally considered that airplanes like theOV-I Mohawk, with wirigs slightly above the bottom of the fuselage are best for ditching. Theirposition is a good compromise between a high wingand low wing aircraft. Ditching capability of theMohawk is so good that its -10 says: The ditchingcapabilities of the aircra ft (Mohawk) are such thatin any emergency condition over water, when airspeed can be maintained, bailout may not beadvantageous.AUGUST 1967

:

40 SEC I l

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Figure 3 Teardrop Sea EvaluationArmy aircraft have an advantage over some ofthose flown by the other military services. For yearswe have purchased airplanes that land at slowerspeeds and have a short runout. Take advantage ofthis factor and ditch as slow as possible while

maintaining adequate control.Wingtip tanks in low wing aircraft can be agreat help in planing during the water runout.They also add buoyancy, allowing greater escapetime. The trouble is they must be empty or nearempty. So bum out the fuel or transfer it to internaltanks if possible. Remember, however, the tip tanksmight get knocked off or even cause the wing toshear if the water is hit hard. I f one should comeoff, the airplane might roll over.

When ditching in the Seminole, Mohawk andother twin-engined airplanes, it is important thatthe thrust and aerodynamic drag be kept symmetrical. I f there is partial power, it should be used tomaneuver the airplane and reduce the rate of descent. I f there is no power, the props should befeathered.Figure 4 Landing on swells

DIRECTION OF SWELL MOVEMENT

lANDING ACROSS SWEllS MOVEMENT

///GOOD

/ ----4;)'

c, -


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itching TechniquesThe first rule in ditch heading selection should

be to land parallel to the primary swell in winds(see fig. 4 less than 25 knots. f there is only oneswell system (rarely the case) this reduces the problem lan.ding in of two di;ections. Generallythe ~ I r e c t l O n offenng a headwInd component, if~ n y S best. Where two swell systems are running,It S often best to land parallel to the primary and

~ o w n the secondary, again disregarding the windIf. less than 25 knots. One low-wing land planeditched parallel to the swell with a 42 knot crosswind and encountered a very smooth deceleration.However, it is generally advisable to land into awind of over 35 knots. In this case it's best to hit

~ h e water on t h ~ back side of the swell. Do not goIn on the face sIde, which would be like trying toland uphill.

Of course, all of this is assuming that you haveenough power to control or enough altitude to

~ l i g n your aircraft into the proper ditching headIng. f you have no control, the above ditchingheadings are what you shoot for but may not reach.NIGHT DITCHING

When ditching in the day or at night with illumi~ a t i o n descent can be broken by flaring with power,If you have it, just before hitting the water. Butwhen it's dark and the water can't be seen, a powerapproach should be used to touch down if poweris available.

Make a normal approach until you are within afew hundred feet of the water. Then establish apower approach with a sink rate of about 200 fpm,a nose-high attitude and with a speed sufficientlyabove stall to establish positive control. Do notdepend upon the altimeter but be ready to makecontact at any time; altimeters may be a few hun-dred feet off in mid-ocean.

Chop power as soon as you make con tact withFigure 5 Self Illumination Pattern

DITCHING HEADING

22

the water. f the airplane bounces, hold the controlin the touchdown posi tion. f it is a very hardbounce, use the elevator to keep the attitude constant.

f you have a flare to illuminate your c;litching,the Tear Drop Self-Illumination Pattern is a goodtechnique to use (see fig. 5 .ROTARY WING DITCHING

In one way the helicopter is an excellent ditch.;ing aircraft. It can enter the water with no forwardspeed at all. On the other hand, some helicopterswin even roll over on their back and most will sinkwithin seconds after touching the water. When theydon't roll over on their backs, di tching in a helicopter can almost be a pleasant affair. One helicopter pilot who had to ditch at night said heentered the water so softly that he didn't know hehad completed his ditching until the helicopter wasalmost completely submerged. I just kept right ontrying to fly the fool thing until I started breathingwater.

When you are ditching under a controlled situation take advantage of one of the helicopter's goodpoints. Just before touching water bring it to ahover. Open hatches and panels needed for escape.Launch the rafts and allow the passengers and crewto board them. Then move the helicopter downwind enough to clear the life rafts and ditch it.The survivors should then move their rafts towhere you are and help you get on board.

The -lOs give the proper pilot techniques for eachtype Army helicopter. Included is the proper sideto roll the helicopter upon water contact i f necessary. Every aviator should study these ditchingtechniques before flying a helicopter over water.

Although each type helicopter reacts differentlywhen being ditched, there are certain general rulesthat can be followed for all of them.All Army helicopters ditch better at zero speed.Also all of them should enter the water in a nosehigh position. The -lOs usually tell how much thisshould be. The best idea is to follow the -10.

There is still some controversy about rolling thehelicopter on its side. One of the reasons this isdone is to stop the rotors and prevent injury tothose persons getting out of the helicopter. MostArmy helicopters do not have rotor brakes andthere is no other way to stop the blades.The old wooden blades sometimes would breakoff or shatter. This helped as it reduced the topheaviness of the helicopter. However, metal bladesseldom break in the water. f the rotors are rotatingvery fast, they might cause the fuselage to roll overwhen the blades dip into the water.



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f ships are present in the ditching area andthere is time, ask for help in making a cast recov-ery. This is a technique developed by the Navyback in the days when ships carried operating sea-planes. It is now considered an obsolete procedurebut can be of some advantage to the Army aviatorin helicopters and small land type airplanes.

When a ship makes a sharp turn in water, thecentrifugal force causes water to surge upward fromunder the ship, which in turn makes a slick formoff the inboard quarters (see fig 6). This slickextends from 100 to 300 yards depending upon thesize and speed of the ship. Army aviators will findan advantage in ditching in this slick area whenthe seas are choppy and when the ship is large andfast enough (in excess of 12 knots) to clear awide area.

Evaluate the sea in the normal manner and se-lect a heading. The turning ship will have little orno effect on the swells, but will smooth the seassuperimposed on them. Consequently, less atten-tion need be given to the chop as the ship largelyfla ttens it.Figure 6 Landing n the slick

SLICK AREABOWW VE

HELICOPTER TOUCHDOWN 0FIXED WING TOUCHDOWN EAPPROACH

AUGUST 1967

hen ditching n aircraftfollow 10 instructions

The approach should be made to touch waterclose aboard the inside quarter of the ship at orjust beyond the wake i f the aircraft is fixed wing.Runout should be completed within the slick areabefore encountering the bow wave. Helicoptersditching with no forward speed should touch downjust behind the bow wave to have the maximumtime for clearing the aircraft before the wakeappears.

Do not touch down on the central area of theturning circle. At this point the ship's bow waveconverges and focuses in an Archimedes' spiraleffect that culminates in an extremely confusedand unpredictable situation which may result inunusually high and steep peaking seas.Single screw ships circle best to the left whiletwin screw ships do equally well to the left or right.

AFTER DITCHINGAfter ditching, all personnel should immediatelyevacuate the aircraft. There have been some cases

when an aircraft remained afloat for awhile butmost sink rapidly. In cases where the aircraft hasremained afloat, it has sunk very rapidly and with-out warning when hit by a large wave or swell.

It is quite normal for a person who cannot swimto want to remain aboard or cling to the aircraftas it's a sort of mother earth to him. This must beprevented at all cost as he will not have time toget out when the aircraft starts to sink.

f life rafts have been placed on board in prep-aration for flying over water, they should belaunched as soon as the aircraft hits and before thepassengers disembark. Do not inflate them in theaircraft. After launching they should be tied to theaircraft so they won't float away before they areloaded. However, use slip knots so that they can bequickly untied when the aircraft starts to sink. fpossible, personnel should move from the aircraftdirectly into the rafts.

CONCLUSIONf you have studied the techniques of ditching

and have provided yourself with the proper equip-ment, you can make a successful ditching. In astudy of ditchings the Civil Aeronautics Board con-cluded that: All factors being equal, premeditatedditching should have an equ l or gre ter numberof survivors than a forced landing on land, i f ade-quate survival and rescue facilities are provided.

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Colonel Harry L. BushCommanding OfficerU S. Army Aviation Materiel LaboratoriesFort Eustis Virginia

HAT WILL Army aircraftlook like in the year 1980?Will it have wings or rotorblades, or neither? Will it have

one engine, six, or more? Whatabout speed? Will its speed be400 knots? 800 knots? Faster? Howmany passengers will i t carry?What kind of armor? Will it usea new type fuel? And will the aircraft itself be manufactured fromnew materials (such as boron,glass, or metal fiber reinforcedresins) stronger, lighter, more dependable than those now used?

These questions are but a fewof the fascinating problems thatchallenge the imagination andskill of a relatively small groupof highly trained engineers andscientists who make up the firstteam of Army aviation research.

This group, with an authorizedstrength of 402, is known as theU. S Army Aviation MaterielLaboratories - or AVLABS forshort. t carries out its work quietly and without fanfare at FortEustis, Va. Also located here is theU. S Army Transportation Center and Fort Eustis USATCFE).AVLABS operates as a tenant classactivity, which means that itsactivities are separate and distinctfrom TCFE.24

A VLABS is the R&D fieldorganization of the U. S ArmyAviation Materiel Command(AVCOM) and reports directlyto the commanding general ofAVCOM in St. Louis, Mo.AVCOM, in turn, is a major subordinate command of the U. SArmy Materiel Command (AMC)in Washington, D. C. AVLABS,the Army's principal aeronauticalresearch activity has been in business since 1942-and was createdat the same time Army aviationcame into being. In former years,when it also supported the Transportation Corps (TC) in allmodes of transportation, it operated under such names asUSATRECOM, TRECOM,TRADCOM, TRADS, TDES andthe TC Board. In April 1964 twas placed under AVCOM. It hasbeen called A VLABS since March1965, and now devotes all its energies to Army aviation research;

But ever since 1942, the goalof this organization has been tofind, develop and help put intooperation new and better equipment to improve Army mobility.

The word research - whichmeans to search again - is thekey word in AVLABS' goals. Toput it in official terms, AVLABS'

mission is to plan, organize, andconduct research, exploratory development, advanced development, and technology support tosystems development in the fieldof subsonic, low-flying Army aircraft used in support of groundforces in combat. And there youhave i t- to increase the airmobilityof the Army.

But what does AVLABS reallydo? What has it accomplished?What is it working on today thatwill increase the airmobility ofground forces in combat?

The first paragraph of thisstory offers a clue, because research in any field takes time. Research into areas well beyond today's capability may not materialize into actual hardware until1980. On the other hand, researchbreakthroughs often occur - sudden new developments are madeand the lead time may be reducedfrom years to months.AVLABS' nine technical divisions are hard at work on dozensof vital projects, but space permits mention of only a few. Someof these top projects include theComposite Aircraft Program

CAP), the regenerative engine,and emulsified fuel (safe fuel).In addi tion there are many small-



27/68

er programs, which are also considered vitally important to meetthe constantly changing Army requirements to meet new conditions.

Major innovations and changesand improvements in any fieldsimply do not just happen. Obviously, the Southeast Asia situation has dictated hundreds of newrequirements, new needs. Thisnew need or request may take theform of a cha:qge or an improvement on existing aircraft. Or, asoften occurs, combat experiencemay see the need for an entirelynew concept of an aircraft. Aftergeneral r e q ~ i r e m e n t s are set forthfrom the appropriate agencies,various ideas and new approachesare d i s u s s e ~ in detail. From thisbeginning, new designs are created; often dozens are analyzedand e v l ~ t e d before the field ofcontestants is reduced to what isconsidered the best and feasibleto develop) from a cost and timeviewpoint.COMPOSITE AIRCRAFTPROGRAM (CAP)

In the case of the CAP, Composite Aircraft Program, a wholenew aircraft design was needed.Purpose: To develop the technology for a vehicle combining theefficient hover characteristics of ahelicopter with the efficient highspeed cruise characteristics of afixed-wing turboprop aircraft.Eight aircraft companies submitted initial designs.

From these eight submittals,three contracts were let for preliminary design studies of themost promising concepts.Bell Helicopter Company wasto study the tilting rotor-propconcept; Hughes Tool Companyto study the jet-powered stoppedrotor-wing concept; and LockheedCalifornia Company to study thestopped/stowed rotor concept.

The ell composite has a highfixed wing with a tilting rotor-AUGUST 1967

prop at each wing tip. Theserotor-props are used as helicppterrotors when pointed upward andas propellers when pointed forward. The engines are moun tedinboard at the wing root. The aircraft has a tricycle gear.

The Hughes composite has aje t-propelled rotor system whichacts as a helicopter rotor for slowspeed. At high speed, the rotor isstopped and acts as a fixed wing.The aircraft then flies as a conventional turbojet-powered airplane.The Lockheed composite has ahigh fixed wing and a rotor whichstops, folds, and stows for highspeed forward flight. I t has a turboprop powerplant mounted onwing pylons for forward propul-sion. The aircraft has a tricyclelanding gear.

The Army has completed evaluation of these conceptual studiesfor a composite aircraft, and hasawarded two contracts of 1,90Q,-000 each to Bell Helicopter Company and Lockheed--CaliforniaCompany to continue the program.

Lockheed-California and Textron Bellhave been awarded contracts under theComposite Aircraft Program. Above: Lockheed's \\retracted rotor design with therotors stowed (center), retracted (above),and in operation. Below: Bell's tilt rotorconcept n helicopter flight mode (above),midway through conversion (center), andafter complete conversion to high speedflight mode

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AVLABS test pilots re participating in CL-84 evaluations

A VLABS PILOTS TEST THECL-84 V/STOL AIRCRAFTA VLABS has its own group ofassigned research test pilots who

are called upon from time to timeto give their evaluation on specific projects. One such project isthe Canadair CL-84, a twinengine, tilt-wing vertical and shorttakeoff and landing (V/STOL)aircraft undergoing a triservice(Army, Navy, and Air Force)evaluation to determine the aircraft flight characteristics, operational capability, and its suitability to perform a military mission.T63 REGENERATIVEENGINE

Aircraft propulsion systems areunder constant research to makethem more powerful, lighter, andto get the maximum performanceou t of the fuel used. It is thislast goal, low fuel consumption,that now has the attention ofAVLABS Propulsion Division engineers. For one of the currentdrawbacks of the small gas turbine engine is its high specificfuel consumption at aircraf t cruisepower settings.Engineers know that lower fuelconsumption results through theuse of high turbine inlet temperatures and / or use of high compressor pressure ratios. But theyalso know that further reductionsin fuel consumption can be ob-

tained through the use of whatthey call the regenerative cycle.The regenerative gas turbine engine uses a heat exchanger (regenerator) in the exhaust gas pathto remove waste heat and returnit to the compressor discharge air;thus less fuel is required to reachthe scheduled turbine inlet temperature.

Regeneration can cut fuel consumption by 10 to 40 percent.The range depends on the level ofheat exchanger (regenerator)effectiveness. Lower fuel consumption can result in these obviousbut extremely important advantages: Reduced aircraft gross andempty weights. Reduced fuel logistical requirements to overseas theaters. Increased aircraft range capability. Increased aircraft payloadcapability.To evaluate the installationproblems and to seek actual aircraft experience, the T63 regenerative engine experimental flighttest effort was started to determine first-hand just what a regenerative engine could do in anaircraft. Since 1960 the Army hasresearched various heat exchangerconcepts, such as liquid metal,plate tubular U tube, miniaturetubular, and the toroidal rotarytypes.In July 1966, the Allison Divi-

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Army Aviation Digest - Aug 1967

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