Land-Based AircraftOptions for Naval Missions

William D. O'NeilDept. of Defense,

Office of the Director of Defense Research and Engrg.

SOCIETY OF AUTOMOTIVE ENGINEERS, INC.400 Commonwealth Drive, Warrendale, Pa. 15096

770965

Land-Based AircraftOptions for Naval Missions

William D. O'NeilDept. of Defense,

Officeof the Director of Defense Research and Engrg.

ALTHOUGH IT IS NOW MORE THAN THIRTY YEARSPAST, World War II remains the basic pointof reference in analysis of naval warfare,for there has never been a major naval cam-paign since. In the naval sphere the lesionsof that conflict were truly revolutionary,so much that they have yet to be fullyassimilated by many.

As Admiral of the Fleet of the SovietUnion Sergei G. Gorshkov has observed (1)*,in World War II, "Experience in combat oper-ations in the sea and oceanic theaters show-ed that submarines and aircraft had becomethe main, more versatile and effective typesof naval forces." The naval air power whichproved so important in that war was, in signif-icant measure, land based. Land based air-craft accounted for about half of all theU-boats destroyed or put permanently out ofaction. Minelaying and strike aircraftoperating from land bases were among the majorkillers of logistic shipping. And land-based aircraft scored notable successesagainst warships.

But land-based aircraft fell far shortof meeting all needs for naval air power in

*Numbers in parentheses designate Referencesat the end of paper.

World War II. The essence of air power isgetting enough aircraft with the propercapabilities over the target, when they areneeded. The principal factor limiting land-based aircraft as instruments of air power,particularly at sea, was lack of range per-formance. To achieve transoceanic ranges inthe face of low propulsion system efficien-cies, low lift/drag ratios, and high emptyweight fractions, designers had to acceptlarge size, poor agility, limited speed,and/or low ratios of payload to gross weight,This meant that long range land-based air-craft were too costly and too limited incapability for many missions, while aircraftwith the needed capabilities and low costscould not reach many vital targets fromavailable land bases.

The geographically-imposed need fornaval operations has not changed since theSecond World War (although the political-military factors which affect base availa-bility have fluctuated). But the rangepotential of aircraft has improved signifi-cantly as aeronautical technology has advanc-ed (2), bringing many more important oceanareas within reach of aircraft flying fromland bases securely in our possession. More-over, the rapid advance in sensor and weapon

ABSTRACT

Advances in aeronautical technology favorincreased application of land-based aircraftto naval missions. A number of aircraft typesnow combine attractive mission capabilities

with good coverage of ocean areas from avail-able bases. Further developments can be ex-pected to improve mission capabilities and/or range. The result is a broader range ofoptions for naval planners.

technologies has made factors such as a i r -c ra f t a g i l i t y and low-al t i tude performanceless important for many missions, and th isoperates in favor of longer-range a i r c r a f t .

To again quote Admiral Gorshkov, "Con-sidering the importance of the missionsbeing accomplished by .a i rc ra f t , and lookingat the possible nature of naval warfare, i tis f u l l y logical to believe that the impor-tance of a i r c r a f t in comparison with thelast war is great ly increasing." (1) Inpar t i cu la r , i t seems l i k e l y that the roleswhich land-based a i r c r a f t can e f f i c i e n t l yand economically play in sea war are expand-ing in scope and importance.

This paper w i l l examine the major navalmission areas and some possible roles forland-based a i r c r a f t in each. No attempt w i l lbe made to define precise mission require-ments or to compare land-based a i r c r a f t withother possible a l te rnat ives.

ANTI-SUBMARINE WARFARE

The greatest single threat to Westernmaritime securi ty at th is time is the sub-marine. I t is worthwhile to note that th isis not a resul t of the strength of the sub-marine as a f igh t ing sh ip- - for i t s size andcost i t is among the weakest and most vu l -nerable of naval vessels. Rather, the sever-i ty of this threat is a direct reflection ofthe d i f f icu l ty of finding submarines in thef i r s t place.

Aircraft were the major ki l lers of sub-marines during World War I I , and there isevery reason to believe that this would con-tinue to be true i f a naval campaign were tobe fought today. To those who are unfamiliarwith modern air ASW (anti-submarine warfare)i t is often surprising to learn that aircraftcan successfully hunt submarines which do notcome to the surface. By dropping sensitiveacoustic sensors, packaged as sonobuoys,into the water the aircraft is able to obtaindetection results which compare quite favor-ably with those for ships and anti-submarinesubmarines.

There are several reasons why aircraftare particularly eff icient and effective sub-marine hunters, including,

1. Speed of Response. Since detectionsof submarines wi l l be infrequent and fleetingthe airplane's abi l i ty to reach the scenequickly is of considerable importance.

2. Lack of Vulnerability. I t is rela-tively d i f f i cu l t for submarines to attackaircraft .

3. Flexibi l i ty . The high mobility ofaircraf t , particularly long-range aircraf t ,permits the ASW commander to concentrate theireffort where and when i t is needed.

4. Low Cost. The unit costs of ASW air-craft, while large by absolute standards, are

Fig . 1 - Photograph of P-3C

small compared to those of submarines, sothat one can afford a large force of them com-pared to the number of targets.

The principal land-based ASW aircraft ofthe U.S. Navy at this time is the LockheedP-3C Orion (Fig. 1). The P-3 series aircraftare derivatives of a commercial transportdesign of the mid-1950s, the Lockheed L-188Electra. Principal data for the P-3C areshown in Table 1.

I t is frequently asserted that an ASWaircraft is only as good as i ts ASW avionics.This is certainly true in the sense that thevast superiority of the P-3C over roughlysimilar ASW aircraft produced in other coun-tries is very largely a matter of the excel-lence of the avionics system developed forthis aircraft through the combined effortsof the U.S. Naval Air Development Center,Lockheed, and a number of avionics equipmentcontractors.

Any implication that the qualities ofthe aircraft i t se l f are unimportant is notcorrect, however. In the f i r s t place, employ-ment of the AN/ASQ-81 MAD (magnetic anomalydetection) equipment, which is used to obtainfinal target verification and localization,requires that the aircraft be flown in a veryt ight and precise pattern quite close to thewater. Thus i t is essential that the air-craft have good maneuverability and handlingqualities during low-speed maneuvering at lowaltitudes and that pi lot workload be kept toa minimum under these conditions.

Beyond the requirements for low-speed,low-altitude maneuvering imposed by currentASW equipment and tactical concepts, andthose for ruggedness, simplicity, and corrosionresistance common to al l naval a i rcraf t , thereis the matter of range, or, more specif ically,

radius of action. (Radius of action is thatdistance from its base to which the aircraftcan fly, perform its designated mission, andreturn with specified reserves.) As will beseen from Table 1, for a mission requiringfour hours patrol time on station the radiusof action of the P-3C is a little more than1400 nautical miles. Actual operationalradii will usually be less than this, due toneeds to operate the aircraft in non-optimalconfigurations, crew-fatigue considerations,or unfavorable disposition of availablealternate bases.

Operating from presently-available U.S.and allied bases the P-3C can give goodcoverage of many important ocean areas, as isshown in Figure 2. (Figure 2 includes somebases from which U.S. Navy P-3s do not regu-larly operate at present but which are suit-able for P-3 operations and which lie in theterritory of allies with whom we have mutualdefense agreements.) There are other impor-tant ocean areas, hovfever, which remain be-yond the P-3's reach. Moreover, certain ofthe bases shown in Figure 2 might not beavailable, in one eventuality or another, forpolitical or military reasons. An aircraftwith greater range would thus be even moreuseful.

One possibility is to stretch the P-3.Lockheed has conducted a feasibility-levelconceptual design study of a P-3 with increas-ed span and fuselage length, greater fuelcapacity, refined enclines, and strengthenedstructure for higher gross weights. Prelim-inary details are given in Table 2 and itwill be seen that the stretched P-3 has sub-

Table 1 - Lockheed P-3C Orion (Update III version)

ConfigurationOverall length 116' 10"Span 99' 8"Wing area 1300 sq.ft.

Weights

Empty 66,795 Ib.Fuel capacity (@6.8 lb./gal.) 62,560Design gross 139,465ASW payload 19,853

Propulsion

4 Detroit Diesel Allison T56-A-14 turboprop enginesRated power, per engine 4,591 SHPEquivalent cruise TSFC (installed) 0.58 lb./lb-h.

Performance (Clean, at design gross weight unless specified)Maximum speed (15,000 ft.) 380 knotsService ceiling 27,000 feetRadius of action*

Zero time on station 2,020 n.m.4 hour time on station** 1,4408 hour time on station** 900

Flight duration*Normal mission 12 hoursMaximum (4 engine loiter) 14.0Maximum (2 engine loiter) 15.6

Average long-range cruise speed (25,000 ft.) 350 knotsFerry range 4,830 n.m.Load factors

142,000 lb. gross weight +2.5, -0 8135,000 lb. gross weight +3.0, -1.0

Mission EquipmentA-NEW digital computerized integrated anti-submarine

and anti-ship combat system. Advanced acoustic signalprocessor, APS-115 surface search radar, FLIR, ALQ-78 ESM.

Stores:Sonobuoy chutes 52Internal weapons bay length 154 inchesExternal stores stations 6 x 2000 lb.

2 x 1000 lb.2 x 500 lb.

Weapons delivery capability includes Mk. 46 torpedo,HARPOON anti-ship missile, and various mines.

*With reserves equal to 10% of initial fuel plus fuel for20 minutes at sea level, 5% increased fuel flow, and four-engineloiter unless specified.

** With two hours of loiter time spent at sea level.

Source: Lockheed

Fig. 2 - P-3C potential coverage from selectedbases (1440 n.m. radius)

stantially greater range than the P-3C. Thisincreased range can be used to extend thearea which may be covered from existing bases,increase times on station in present patrolareas, or cover present areas with fewer orless favorably located bases. Figure 3illustrates the fact that it is possible withthe increased radius of the stretched P-3 tosimultaneously increase coverage and cut backon bases.

Both the time and costs to develop sucha stretch P-3 would be small by comparisonwith those for any entirely new aircraftand the production costs would probably beless than those for a new aircraft of com-parable capabilities, given comparable pro-duction rates.

Some questions remain concerning thestretched P-3. One of these concerns theeffects of sixteen to seventeen hour missionson crew efficiency. It probably will benecessary to increase the normal crew sizefrom the P-3C's 10 to 14 or so to provideon-board reliefs for critical personnel.Special attention will have to be paid tocrew efficiency and comfort in any long-endurance aircraft.

The vast decreases in the weight andcost of electronic systems, per unit ofcapability, over the past twenty years, havemade possible the tremendous improvement inASW effectiveness from the P-3A to the UpdateIII P-3C, with little growth in aircraft orpayload size. In order to substantiallyexpand the area ASW surveillance capabilitiesof aircraft, however, or to add further tothe non ASW capabilities, a larger payload

will be needed. The stretched P-3 couldprobably accept some limited additional pay-load, thanks to the six-foot stretch of thefuselage, but at the sacrifice of some range.(A thousand pounds of payload would cost 20to 50 nautical miles of radius of action.)If very much additional payload is required,or if growth in both payload and range isneeded, then another aircraft entirely willbe necessary.

Fig. 3 - Stretched P-3 potential coverage withreduced basing (2120 n.m. radius)

Table 2 - Stretched P-3

ConfigurationOverall length 123' 2"Span 110'Wing area 1,498 sq.f t .

WeightsEmpty 72,475 l b .Fuel capacity (@6.8 lb . /ga l . ) 80,520Design gross 163,450ASW payload 19,883

Propulsion4 Detroit Diesel Al l ison 501-M69 turboprop enginesRated power per engine 4,678 SHPEquivalent cruise TSFC (instal led) 0.52 l b . / l b - h .

Performance (Clean, at design gross weight unless specified)Maximum speed (15,000 f t . ) ' 370 knotsService cei l ing 27,000 f t .Radius of action*

Zero time on station 2,750 n.m.4 hour time on stat ion** 2,110 n.m.8 hour time on stat ion** 1,430 n.m.

Flight duration*Normal mission 16 hoursMaximum (4 engine lo i te r ) 20Maximum (2 engine lo i te r ) 21

Ferry range 6,500 n.m.Load factors

163,450 lb . gross weight +2.5, -0.8155,500 l b . gross weight +3.0, -1.0

Mission EquipmentIdentical to P-3C (Update I I I ) except that length of weapons

bay is increased to 173 inches.

*With reserves equal to 10% of i n i t i a l fuel plus fuel for20 minutes at sea leve l , 5% increased fuel f low, and four-enginelo i te r unless specif ied.

**With 2 hours of l o i t e r time spent at sea level .

Source: Lockheed feas ib i l i ty - leve l conceptual design study.

4

In the past, many land-based ASW aircrafthave been adaptation:; of then-current bomberor transport types—the Lockheed PV, theConsolidated P4Y, the Short Sunderland, theAvro Shackleton, the Hawker-Siddeley Nimrod,the Canadair Argus, the Ilyushin 11-38, andthe P-3 i t se l f are al l examples. Thus i t isnatural to consider whether i t might beattractive to repeat the t r ick .

Table 3 provide:; data on a selection ofcurrent bomber and transport a i rcraf t , oper-ated on patrol mission profi les. One of these,the B-52, is of questionable sui tabi l i ty forASW missions since i:s 23-foot length ofpressurized fuselage would not accommodatenormal ASW equipment and crew.

I t is l ike ly that any of the remainingaircraft of Table 3 (and others in the sameclass) could be modified to serve as an ASWvehicle with better range-pay!oad performancethan the stretched P-3. This might be neces-sary i f i t were desired to use aircraft tosupplement ASW surveillance, requiring carriageof surveillance equipment and stores on long-term patrol. (The maximum radius for eff ic ientlong-term patrol is about half of the maximumradius for zero time on station; this pointwi l l be discussed at greater length later inthis paper.) These aircraf t could also expandthe area of land-based ASW aircraft coverage,reduce the number of bases required for equiv-alent coverage, and/or permit ASW aircraft tocarry equipment and stores for additional

missions. None of them is so well adapted tolow-altitude maneuvering as is the P-3, butnew systems and tactics may permit ASW aircraftto do most of their work from high alt i tudes,seldom i f ever descending for MAD detections.

The cost and time to develop a modifiedversion of such an a i rc ra f t , outf i t ted forASW, should be roughly comparable to that todevelop the stretched P-3. In terms of emptyweight, however, these aircraf t are 80% to375% larger than the stretched P-3. Aircraftcosts are very heavily influenced by emptyweight and i t is safe to assume that ASWversions of these aircraf t would be sub-stantial ly more expensive than the stretchedP-3. Since, under existing circumstances,the Navy can only spend more on system X i fi t spends less on system Y, the acquisitionof larger, more expensive aircraf t wouldappear to be feasible only i f : (a) their im-proved efficiency permitted enough reductionin numbers bought to outweigh the added unitcost, or (b) they could take over missionswhich would otherwise have to be performed atgreater expense by other forces. I t has notbeen demonstrated, to this time, that any ofthese aircraf t could f u l f i l l these conditions.

The alternative to adaptation of âï)existing type is development of an all-newaircraf t . Figures 4 and 5 present performanceestimates for new-development a i rcraf t derivedfrom a highly-simplified parametric model(discussed in Appendix A). Data are shown

Table 3 - Bomber and Transport A i r c ra f t

ConfigurationOverall lengthSpanWing aree

WeightsOperating Empty*Assumed Mission PayloadAssumed Fuel LoadMaximum dross

Boeing B-52DRe-engined

156' 6"185' 0"4000 s q . f t .

187,500 l b .45,000

217,500450,000

Performance (Clean, Maximum Gross Weight)

Radius oï Act ion**0 T0Î4 hr. TOS8 hr. TOS

Total Mission TimeTypical Cruise Speed

3910 n.m.3100240020.1 hr.390 k t .

Load Factor at Max. Gross Weight 1.8g

Major Changes from Basic A i r c ra f t CF6 or JT9Dor RB 211Engines

Boeing 707-320BModified &Re-engined

148' 0"1421 6"2892 s q . f t .

132,200 l b .30,000

177,800340,000

3140 n.m.2300140015.0 hr .445 k t .2.5g

Minimum equip-ment changes;JT10D or CFM 56Weapon Bays

DouglasDC-10-30

182' 3"165' 4"3647 s q . f t .

236,400 l b .50,000

303,600590,000

3900 n.m.2900190015.5 hr.475 k t .2.5g

Boeing 747-200

225' 2"195' 8"5500 s q . f t .

344,000 l b .70,000

406,000820,000

3700 n.m..2900210019 hr .480 k t .2.5g

Minimum equip- Minimum equipchanges; Body changes; BodyFuel Fuel

*As normally equipped, without naval mission equipment.**With reserves equal to 10% of i n i t i a l fuel plus for 20 minutes at sea level and 5% increased fuel f low.

Source: Estimates based on manufacturer's data.

6-

2 5-

I3' STRETCHED JßP*

0 100 200 300 400 500 600GROSS WEIGHT - THOUSANDS OF POUNDS

Fig. 4 - Radius with zero time on station

5-

t-« 3-

2-

H

0 100 200 300 400 500GROSS WEIGHT - THOUSANDS OF POUNDS

Fig. 5 - Radius with four h time on station

600

for both "moderate-development" and "inten-sive-development" a i rcraf t . A moderate-development a i rcraf t , in this context, isone which stays with technology which isavailable more-or-less "off the shelf" inan effort to minimize development costs. I twould for instance employ engines already

developed for other applications, largelymetal primary structure, relaxed but non-negative static s tab i l i ty margins, fixedplanar array antennas, etc. The designersof an intensive-development a i rc ra f t , bycontrast, would pay the price to reducedevelopmental technology to practice in

order to produce an aircraft with a betterperformance relative to i ts size and, hope-fu l l y , cost. I t might embody improvementssuch as 'composite materials in primarystructure, negative static s tabi l i ty margins,high-Mach-number turboprops, new-developmentengines, conformai-array antennas, etc.

The performance here assumed for theintensive-development aircraft presupposessubstantial development effort on techno-logy and subsystems, which would add to air-craft development cost and delay i ts serviceentry. On the other hand, under presentacquisition policies any new-developmentaircraft wi l l have a lengthy gestation period,regardless of technology level. Given th is ,and the substantial reduction in size for anydesired level of performance, i t seems l ikelythat an intensive-de/elopment aircraft wouldbe the better choice unless the number to beprocured was smal1.

But the costs of developing such an air-craft would be staggering—probably in excessof three b i l l ion dollars! I t would be veryd i f f i cu l t for the U.S. Navy to find such asum for ASW aircraft development and theremust be a strong impetus toward sharing thishuge development cost with some other user.Recalling the historic association betweenair l iners and ASW patrol aircraft one mightsuppose that the development cost could bespread by developing a dual-use a i rcraf t , withcommercial transport and ASW applications.

Unfortunately, :he prospects for develop-ment of new air transport aircraft of anysort appear quite uncertain. Beyond th is , i tseems clear that the needs of the airl inesand of the Navy have been diverging. Inair l ine terms the planes we have been dis-cussing represent th<; ultimate in "long-thin"airplanes—aircraft designed to carry verymodest payloads over very great distances.What the airl ines are? looking for at thistime are high-capacity aircraft for relative-ly short to medium stage lengths (3). Thereis a fundamental confl ict in the designrequirements between these two classes ofaircraft which cannot be resolved in any waywhich wi l l be economically and mi l i ta r i l yacceptable.

Broadly speaking, the needs for ASW air-craft can be divided into two categories,which we shall class as "responsive" or"patrol" . In a responsive mission the air-craft is responding to some alert of a sub-marine's presence - a report of a torpedoingor detection by a surveillance system oranother unit , for instance - and needs to getthere fa i r l y quickly, When i t arrives i t wi l lneed to spend some time trying to redetectand attack the submarine but, generallyspeaking, wi l l either1 achieve a k i l l withinfour to eight hours or have very l i t t l echance of ever making i t . Thus for these

missions speed is no less essential thanendurance.

In a patrol mission, on the other hand,the object is to maintain a continuous search(or perhaps simply a continuous readiness torespond to contacts by nearby units) in acertain geographic area, or around a surfaceforce, over an extended period of time - daysor even weeks. This would normally be accom-plished by having the aircraft f l y in relays,relieving one another on station, but evenso patrol missions put a premium on enduranceand for them i t might perhaps be desirableto develop special types of aircraf t havingespecially great endurance.

There are at least two types of aircraf twhich f i t this description: airships and open-ocean seaplanes. The airship, having noinduced drag when operating at neutral buoy-ancy can lo i ter at low speeds with l i t t l epropulsion power. An open-ocean seaplanecan rest on the surface of the water withl i t t l e or no propulsion power. In eithercase, fuel consumption while on patrol isgreatly reduced.

I t has been nearly half a century sincethe last large naval airship, the U.S.S.Macon (ZRS 5), was bui l t by Goodyear. Therehas been a revival of interest in l ighter-than-air (LTA) aircraft and examination ofthe performance predicted for a modern air-ship of the Macon's size wi l l indicate someof the reasons (see Table 4). Most of the

Table 4

ConfigurationOverall LengthMaximum DiameterNominal Gas Volume

WeightsEmptyFuelBal lastGrossPayload

PropulsionCruise Engines

Type

Power per EngineLoiter Engines

TypePower per Engine

PerformanceMaximum SpeedNormal cruising speedService ce i l i ngMaximum Radius of Act ion**Time on stat ion for radius of

act ion**5000 n.m.3000 n.m.2000 n.m.1000 n.m.

Time on stat ion for radius ofact ion***3000 n.m.2000 n.m.

Crew

- Airships

USS MACONZRS-5(1933)

785 f t .132.9 f t .6,500,000 c u . f t .

242,356 l b .110,00020,000

403,00028,244

8 MaybachVL-II Diesel560 BHP

(Loiter oncruise engines)

75.6 Kt.55 Kt.

2670 n.m.

—- -3.6 days9.1

- -—91

ModernizedMacon-sizeAirship

785 f t .132.9 f t .6,500,000 cu . f t

175,676 l b .192,600

0*416,62545,000

4 Gas Turbine

1060 SHP

2 Diesel250 BHP

80 Kt.65 Kt.5000 f t .5630 n.m.

4.0 days16.522.729.0

2.5 days5.530

*No water ballast at takeoff; water picked up from sea as fuel burnt off.**Cruise out and back at normal cruising speed; loiter at 30 knots; 10%reserves; 100 lb./hr. fuel burnt for auxiliary and service purposes.***As above but cruise at 80 knots and loiter at 50 knots.

Sources:For Macon: Estimates based on data from Richard K. Smith, The

Airships Akron and Macon, Annapolis, U.S. Naval Institute, 1965.For Modernized Airship: Estimates based on Goodyear data.

improvement over the Me.con results from pre-dicted reductions in empty weight throughthe use of modern materials, equipment, anddesign tools. The weight estimates are in-evitably somewhat speculative in the absenceof recent, directly-relevant design experi-ence, but do reflect a well-understood andproven basic structural scheme (wire-bracedbuilt-up ring frames tied together withlongitudinal girders--a structural conceptyery similar to that of the last Zeppelins)and a considerable body of theoretical,model-test, and empirical data on loads.While the history of the large r ig id airshipswas not a happy one, there is l i t t l e in thehistorical record to indicate that such ve-hicles are basically unfeasible (4). Manyoperational questions remain, however.

The virtues of airships are greatest inmissions which do not make high demands forspeed; at speeds much in excess of 100 knotstheir l i f t /d rag ratios start to become un-attractive. (Because of the square-cube lawairship speed capabilities improve with size,however.) For responding to ASW surveillancecontacts, for instance, the limited speed ofthe airship would be a serious handicap, inmost cases. But for missions requiringlengthy patrol at low speeds (below, say 50knots) the efficiency of the airship is im-pressive. I t is interesting to note that insprint-and-drift operations (to deploy low-speed ASW sensors, for instance) the modernairship of Table 4 could escort a 30-knotconvoy for more than 5,000 nautical miles intoa 20-knot headwind, without refueling. (Air-ships have demonstrated the ab i l i ty to refueland replenish from surface ships in the past.)

Hybrid airships, in which a major portionof the l i f t is produced by airflow over aflatened hu l l , have been investigated byseveral organizations, most notably AereonCorp., Boeing-Vertol, and Goodyear. Low-speedefficiency is sacrificed but cruise speedsmove upward—perhaps to 200 knots or so forvehicles in the size range of probable inter-est. The crucial question is structural weight.The most detailed examinations to date, byGoodyear, have tended to make the hybridslook unpromisingly heavy, but others disagree.

The PS-1, designed and bui l t by Shin Meiwaof Japan, appears to be the closest approachto an open-ocean seaplane bui l t to date. Thisai rcraf t , described br ief ly in Table 5, wasactually designed for ASW. The available datado not give a very complete picture of i tsperformance but i t seems; clear that a sub-stantial penalty has been paid for open-oceanlanding capability. I t is claimed that theaircraft can operate in seas up to 14 feet,although one wonders what the ride must bel ike when s i t t ing on the water in such con-ditions. I t is probably unwise to try to

draw any sweeping conclusions about open-oceanseaplanes on the basis of this one example.

A design study for a "sea control amphib-ian" aircraft with the ab i l i t y to land andtake of f in sea state 5 (one-third highestaverage wave heights to 14 feet, with 20 footwaves commonly encountered) has been reported(5). A very large catamaran hull was select-ed to provide adequate s tab i l i ty and sea-keeping during sea s i t t i ng . General data aregiven in Table 6.

Because of the paucity of relevant designdata this design must be regarded as relat ive-ly speculative at this time, with open-sealanding, takeoff, and lo i ter being the pr inci-pal question areas. There are also manymission questions, chief among which is whati t is that such an aircraf t can do that wouldjust i fy the enormous costs which must go withi ts bulk. Nevertheless, i t is an impressiveand thought-provoking concept.

In addition to being able to stay onpatrol station with low fuel consumption,both airships and open-ocean seaplanes offerthe possibi l i ty of deploying anti-submarinesensors into the water and then recoveringthem. There are obvious economic advantagesin not discarding the sensor, as a normalASW airplane must with i ts sonobuoys. Therecoverable sensor could either be tetheredto the seaplane or l e f t f loating freely, forlater pick-up.

But the virtues of recoverable sensorsare not entirely clear-cut. The sensorarray wi l l normally be heavier than i t couldbe i f expendable, and the ai rcraf t must carryheavy and bulky recovery gear. I f the arrayis towed by or tethered to the aircraf t i tcould be a serious embarrassment when a contactwas made or a threat was reported, since re-covery would normally take considerable time.I f the sensor was not tethered to the aircraf ti ts recovery is l ikely to involve some ratherd i f f i cu l t feats of seamanship, particularlyin rough weather. Against the possible rangeadvantages of a recoverable sensor must be setthe conventional a i rcraf t 's ab i l i t y to spreadi ts expendable sensors quickly over a largearea and to monitor them al l by radio fromhigh alt i tude.

A wide variety of potential ASW aircraf thave been discussed here; i t seems l ike lythat we neither need nor can afford a l l ofthem. But which ones should develop andacquire--if any? This question ought to beanswered on the basis of detailed, quantita-tive evaluations of costs, mil i tary worth,and operational su i tab i l i t y . I t i s , of course,impossible to provide such an analysis here,but a highly schematized and simplified com-parison wi l l shed l ight on some importantconsiderations.

For this comparison, the following as-sumptions wi l l be made:

1. The mission is one of continuouspatrol of a fixed area, not one of contactinvestigation or escort;

2. Mission effectiveness is simply pro-portional to the weight of payload carriedaloft on station—more payload is alwaysbetter;

3. Aircraft l i fe-cycle cost is propor-tional to some weighted sum of aircraf t emptyweight (unequipped) and payload weight;

4. Uti l izat ion rate and avai labi l i tyare the same for a l l a i rcraf t , regardless oftype or mission duration.

I t is clear that one wi l l wish to mini-mize, in this case, the cost per unit effec-tiveness and that this ratio may be expressed,under these assumptions, as,

(aWu + bWpNC - 1,/aWu + bWp\Ë - \ FSWp V) (1)

where,

C/E = Cost per unit effectivenessk, a, and b are suitable constantsWu = Unequipped aircraft empty weightWp = Payload weightF = Fraction of its total time which the

aircraft can spend in flightS = Fraction of its flight time the air-

craft is able to spend actually on stationFor the purposes of this example the

following values of tie constants have beenemployed:

k = a = 1b = 5F = 0.3

Figure 6 is a plot of C/E vs. radius for avariety of aircraft. (Recall that it isdesired to minimize C/E.) It will be ob-served that C/E is wery sensitive to theradius, and that an aircraft which is attrac-tive when operations must be conducted farfrom base may be quitiî uneconomical for pa-trolling nearby areas, and vice-versa.

Having presented this seductively-simplecost/effectiveness comparison it is importantto point out some of its more glaring weak-nesses. First, of course, assumption number2 (proportionality of payload and effective-ness) is so artificial that it would be dif-ficult to think of a m'ssion to which itapplied literally. Assumption number 3 isa moderately good first approximation foraircraft procurement cost but it ignores dev-elopment costs, and the dependence of theconstants, a and b, on aircraft type and sizeof buy has been glossesd over. Assumptionnumber 4 seems innocuous enough, superfici-ally, and the value chosen (30% of the air-craft's time spent aloft) is roughly consis-tent with airline experience. But on closerexamination it seems clearly unrealistic tosuppose (as this implies) that an aircraftwhich flies one-hour missions can be turned

around for another mission in two hours andtwenty minutes but that an aircraft of com-parable complexity which flies for a day ata time will need 56 hours for turn-around.In general, the longer the mission duration,the greater the fraction of its time the air-craft will be able to spend in flight. (Thiseffect can be seen in airline operations.)

One feature of this comparison which isquite fundamental and which does not dependupon any of the more dubious aspects of theassumptions is the "knee" which will be foundin all of the curves in Figure 6. For vir-tually any sort of patrol mission costs willrise fairly slowly with radius out to a cer-tain critical point, beyond which costs (re-presenting numbers of aircraft needed to keepone continuously on station) begin to risevery steeply, becoming asymptotic at the air-crafts maximum radius. This critical pointcorresponds closely with the radius at whichthe aircraft is spending half of its flighton station, with the other half devoted totransit to and from station. For convention-

Table 5 - Shin Meiwa

ConfigurationOverall lengthSpanWing area

WeightsOperating emptyNormal fuel capacity (@6.5 1b./gal .)Maximum fuel capacityPayloadNormal grossMaximum gross

Propulsion4 G.E. T64-IHI-10 turboprop enginesRated takeoff power per engine

Boundry Layer Control1 G.E. T58-IHI-1OB BLC turboshaft engineRated power

PerformanceTakeoff run (rough water)Touchdown speedMaximum speed @4900 f t . (1500 m)Normal cruise speed @4900 f t . (1500 m)Range

NormalMaximum

PS-1

109.8102.2

f t .f t .

1462 s q . f t .

51 ,26015,40033,4305,560

71 ,87086,860

190

l b .l b .l b .l b .l b .l b .

f t .

(33.46m)(31 .15m)(135.8 sq.m)

(23,250( 8,971(19,468( 2,530(32,600(39,400

2,970

1 ,250

(5749.2295

kg)i )l )kg)kg)kg)

ESHP

ESHP

m)k t

k t170 kt

11702560

n . m .

n . m .

Source: Kunio Fushimi, "PS-1, I t s Tradit ion and Technology,"Aireview (Japanese), v. 12, n. 325, 1973.

Table 6 - Lockheed Open-Ocean Amphibian

ConfigurationOverall lengthSpanWing area

WeightsOperating, emptyFuelGrossPayload

268.3'317.3'15,000 s q . f t .

528,600 l b .525,000

1 ,250,000140,000

Propulsion4 high bypass-ratio turbofans, each with 83,650 l b . s ta t ic thrust

PerformanceSpeed 29o ktRange 2500 n.m.

Combat Systems2 retractable an t i - a i r c ra f t gun turrets1 105mm gun or equivalent

12 Lance-type missiles6 Long-range an t i - a i r missiles1 U t i l i t y helicopter1 Early warning radar1 Deployable/recoverable acoustic arrayCrew of 30

Source: Reference 5

10

400-

300-

200-

100-

IDAC 150/30

1000 ;:ooo 3oooRADIUS - NAUTICAL MILES

4000 5000

Fig. 6 - Simplified model of cost/effectivenessfor continuous patrol

al aircraft, whose loiter fuel flow is of thesame order of mignitude as their transit fuelflow, this will come at about 50% to 60% ofmaximum radius. For airships, however, (andprobably for seaplanes as well) the criticalradius for patrol efficiency will come rela-tively farther out, perhaps at 70% to 80% ofmaximum radius.

Another general truth expressed in thiscomparison is that advanced-technology air-craft offer real advantages in efficiency,particularly at large radii. Whether theseadvantages are great enough to justify thedevelopment costs is not so clear. Sharingof development costs through common use ofthe same airframe and engines with othermilitary or civil users, or with other mis-sions within the Navy, would probably be aneconomic necessity. And, in any event, wemust bear in mind that, advanced technologyis an option only in aircraft for which wecan wait a considerable period.

ANTI-AIR WARFARE

Next after the submarine on the list ofmaritime threats comes the airplane. Thissurprises many people, despite the fact that

Table 7 -

ConfigurationOverall lengthSpanWing area

HeightsOperating empty (equipped)FuelMaximum gross

PerformanceNominal radius of act ionTine on s tat ionTotal mission timeTypical cruise speedStation a l t i tudeMaximum speed

Takeoff to clear 50 f t .Ferry range

Pa^yload systemsRadar typeSystem MTBFSystem ava i lab i l i t yElectronic warfare equipmentNormal crew

AEW&C Aircraf t

GrummanE-2C*

57'7"80 '7"700 s q . f t .

37,678 1b.

59,880

200 n.m.6.1 hr .9.3 hr .270 k t .20-29,000 f t .322 k t .

3,700 f t .2,440 n.m.

APS-12530 hr .90%Passive5

BoeingE-3A

145'6"145'9"2,892 s q . f t

172,571 l b .148,970325,000

600 n.m.8.5 hr .11.4 hr .430 k t .29,000 f t .473 k t . 923,400 f t .7,670 f t .4,579 n.m.

APY-178 hr.95%None17

*Land based version with fuel in outboard wing panels.

Source: Grumman and Boeing

Soviet official texts on strategy have longpresented the airplane as a close second tothe submarine as an instrument of Soviet seapower (7). With the introduction of the Back-fire into Soviet Naval Aviation (SNA) regi-ments the Russians are bringing almost all ofthe approaches to Europe and Japan within easystriking reach (8).

In order to reach the North Atlantic sealanes without crossing over Europe Backfireswill have to fly down through the GIUK gap--the straits between Greenland, Iceland, andthe United Kingdom. Since it is only about700 nautical miles from northern Scotlandbases to Keflavik, Iceland, and another 700nautical miles on to Sondrestrom, Greenlandit would seem quite possible for fightersbased at these places to intercept the tran-siting Backfires.

First, of course, the Backfires must bedetected. Flying at high altitudes theyshould be visible to radars in Greenland,Iceland, and Faeroe Islands. But flight atmedium altitudes or screening by jamming air-craft might prevent detection by land-basedradars. Even if jamming alerted interceptorsto the presence of enemy aircraft they couldnot expect to accomplish much without accuratevectoring.

One answer of course is an airborneearly warning and control (AEW&C) aircraft.Table 7 provides data on the two AEW&C air-craft in current production, the E-2C andE-3A. There has been sharp debate about thesurvivability and effectiveness of the E-3Aover central Europe, but this is of littleimmediate relevance to the mission involvedhere. No Soviet interceptor has anythinglike enough range to reach GIUK gap, engagein air combat, and return to base.

1 1

The Soviets do possess jamming aircraftwhich could be employed to screen Backfireraids. In order to screen against mobileAEW&C aircraft radars, however, the jammerswould have to accompany the Backfires (assum-ing that the jammers are not powerful enoughto jam the AEW&C radars at long ranges throughtheir side lobes). The AEW&C aircraft shouldbe able to get a f ix on the jammer accurateenough to vector interceptors to i t , and thusto the Backfires which i t is screening.

I t is possible in principle, of course,that the Soviets could out f i t some Backfireswith air intercept radars and a i r - to-a i rmissiles in place of their anti-ship armamentto attack AEW&C aircraf t . I t is l ike ly thatthe AEW&C aircraft could evade the intercep-tor Backfires, which would lack interceptorcontrol f ac i l i t i e s , sut the anti-ship Back-fires might s l ip thrsugh in the process.Thus the AEW&C aircraft may need to havefighters close enougi to chase off the inter-ceptor Backfires.

To effectively safeguard the AEW&C air-craft the defending fighters would need tobe no more than 15 minutes away. Clearly,this wi l l mean airborne combat air patrol(CAP) aircraft in most cases. This has aserious impact on co:;ts since, at a roughestimate, something like six fighters w i l lbe needed to support one aloft on CAP station24 hours per day, while four fighters shouldbe enough to permit keeping three on str ipaler t .

Str ip-alert aircraft may also run intoproblems in reaching the main Backfire raids.The Backfires would normally transit at highsubsonic speeds. (While the Backfires arecapable of supersonic: dash, the high fuel con-sumption involved in even a brief dash would

prevent them from reaching much of the NorthAtlantic.) Unless very long warnings wereavailable, s t r ip-a ler t interceptors wouldhave to f l y out to intercept at supersonicspeeds. 500 nautical miles is about the out-side l imi t for supersonic intercept radius,and 350 n.m. is probably a more real is t icfigure for most f ighters. Thus many inter-cepts in the GIUK gap might occur at extremerad i i , and feints or operational problemsmight easily result in missed intercepts.

I f the situation is marginal in theNorth Atlantic i t is hopeless in the NorthPacific. There is a 3000 n.m. gap betweennorthern Japan and our bases in the Aleutians,through which the Backfires could pour toravage trans-Pacific shipping. With presentland-based fighters one would have to resortnot only to CAP but to air refueling to closethis gap, at enormous cost.

One plausible answer is higher perfor-mance special purpose interceptors, as exem-pl i f ied by the Lockheed YF-12A of the 1960s(Figure 7). With less need for ag i l i t y andlow-level speed i t is possible for such in-terceptors to have relat ively high super-sonic l i f t /d rag ratios and low structuralweight fractions (9, 10, 11), resulting insubstantially increased radius at supersonicspeeds. I t is clear from consideration ofsupersonic transport technology (11) thatsupersonic intercept radii adequate to givegood coverage of ocean areas are technicallyfeasible.

There is another way in which land-basedaircraf t might play a part in combating theBackfire and l ike threats: combine the func-tions of detection and ant i -a i r missile (AAM)launch in a single transport-type offensiveant i -air (TOAA) a i rc ra f t . The concept is

Fig. 7 - Photograph of YF-12A

12

that TOAA aircraft, flying in data-linkedpairs, would patrol in areas such as the GIUKgap and the approaches to Soviet bases on theKamchatka Penisula. Upon detecting a Back-fire raid with their AEW radars they wouldattack with long-range AAMs. By operatingin pairs they would be able to provide mutualtactical support, triangulate on jammers, andsynchronously "blink" their radars to disruptenemy countermeasures without losing informa-tion.

The fundamental principles which under-lie the attractiveness of such a scheme are:(a) if standing airborne patrols must bemaintained then it will be more economical todo so with aircraft optimized for high effi-ciency, and (b) a highly efficient aircraftcan afford to carry heavy and powerful sen-sors and weapons to offset its own deficien-cies in speed and acceleration.

Other uses for TOAA aircraft also suggestthemselves. For one thing they could be sta-tioned as escort or screening forces for con-voys or naval surface forces which lack theirown fighters and AEW&C aircraft. Less ob-viously, they might also perform similarfunctions for carriers. By relieving thecarrier of the need to conduct constant airoperations for its own defense this wouldpermit it to increase its speed of advance(particularly if the wind is blowing in thedirection the carrier needs to go) and wouldreduce its detectability, while enabling itto concentrate far more of its capability instriking power rather than self protection.

In general the aircraft discussed underthe ASW section should all be well suited tothe TOAA role, although TOAA payload weightswould probably run to the higher end of thespectrum in an effort "o gain a substantialdetection and weapon range advantage overinterceptor Backfires and other potentialthreats. While no TOAA aircraft exist todayit would not be difficult to concoct one withmodi fed versions of existing systems. Thefeasibility of such a "quick and dirty" TOAAversions of the stretched P-3 and of the Lock-heed C-130 Hercules transport aircraft havebeen studied, and the results are shown inTable 8 and Figures 8 and 9.

The large rotodomes of radars such asthe APY-1 and APS-125 impose a drag penalty,but this is probably quite avoidable for anybut very near-term TOAA aircraft. Full con-formal radar arrays clearly seem to be theultimate answer. In the shorter term fixedfuselage-mounted fore-and-aft planar arraysshould be acceptable, since TOAA aircraft donot have the same need for full 360° isotrop-ic radar coverage that AEW&C aircraft have.

In principle, airships could also be usedas TOAA aircraft. Their lack of speed, largeradar cross section (at least for rigid types),

Table 8 - Two TOAA A i rc ra f t Concepts

ConfigurationOverall lengthSpanWing area

WeightsOperating, emptyFuelGrossAAW Payload

Propulsion4 Detroi t Diesel A l l ison 501-M69

Performance (missiles retained)-Maximum speedLoiter alt i tudeRadius of action*

Zero time on station4 hr. time on station8 hr. time on station

Combat systemsAEW radarMissile f i re controlMissiles

Crew

Other MODS to Basic A/C

Lockheed StretchedP-3 (AAW)

123'4"110'1 ,450 s q . f t .

84,004 l b .73,578

163,45025,638

turboprop engines

364 kt17,000 f t . (avg)

2,100 n.m.1,5501,000

APS-125AWG-96 fo ld ing - f i nAIM-54 PHOENIX

12

As for stretchedP-3

LockheedC-130 (AAW)

99 '5"132'7"1 ,745 s q . f t .

88,601 l b .73,984

175,05627,248

310 kt20-25,000 f t .

2,200 n.m.1,6901,180

APS-125AWG-910 AIM-54PHOENIX

12

Refaired aftfuselage;extended landinggear fair ings;1000 gal. fuselagefuel

*With reserves equal to 10% of i n i t i a l fuel plusfuel for 20 minutes at sea level , 5% increasedfuel flow, and four-engine lo i te r .

Source: Lockheed feasibi l i ty- level conceptual design studies.

Fig. 8 - TOAA version of stretched P-3(Lockheed)

13

APS-125 ANTENNA

SONOBUOY TUBES 1100 TOTAL)

Fig. 9 - TOAA version of C-130 (Lockheed)

and particularly the'r lack of altitude capa-bility would all be serious handicaps, however.

ANTI-SHIP WARFARE

Official Soviet military thought has longrelegated surface ships to subsidiary and sup-porting roles in major war, and the JointChiefs of Staff assessment is that a combina-tion of geographical factors and allied airpower would greatly restrict employment ofSoviet surface units in a major war in anyevent (12). Nevertheless, the Soviet surfacefleet is too large and well armed for compla-cency; in a surprise onslaught, or near itshomeland, it could do great damage.

Land-based aircraft play a major role inour anti-ship forces today and in the immediatefuture. The P-3, with its APS-115 radar andelectronic intercept equipment, is a mainstayof our surface surveillance capabilities. Manyland-based aircraft are capable of attackingsurface ships.

The advent of sea-based aircraft in theSoviet Navy does change things somewhat, how-ever. While the Yak-36 Forger carried by theKiev is 20 years out of date in terms offighter performance it would still be enoughto endanger surveillance aircraft such as theP-3 and E-2, and could make weapon deliverymore hazardous.

One answer to these problems is simplyto increase the standoff both for surveillanceand weapons release. Radar detection of sur-face ships at 200 nautical miles or more pre-sents no real technical problems and visualidentification could probably be dispensedwith, in most shooting-war situations. Andmissile ranges can certainly be increased to200 n.m., or even more, if there is a need.Other approaches are certainly also possible.

STRIKE

I t may at f i r s t seem that strike againstland targets, even when carried out by Navyaircraft, is not a naval mission in the s t r ic tsense. There may be some justice to this viewin the case of the sort of strike warfare whichour carriers prosecuted in Korea and Vietnambut there are also truly naval objectives onland--ports, dockyards, naval air f ie lds, andthe like—and strikes against these targetsare surely a legitimate naval mission. More-over, bases are vital in naval warfare and wemight need to conduct strikes against non-navalfaci l i t ies on land incident to seizure of abase for naval needs.

The problem with strike warfare has al -ways been that aircraft with good efficiencyfor long-range cruise are too vulnerable andaircraft with good survivability are too short-ranged. The gradual increase in tactical air-craft ranges and the widespread application(at least in the U.S.) of f l ight refuelinghave certainly extended the reach of land-based tactical air strike forces but coverageof many potentially-important naval targetsremains limited. Aircraft such as the B-52offer virtually unrestricted coverage but havelimitations in their abi l i ty to deliver pre-cision attacks against heavily defended tar-gets without fighter support.

Of course long-range missiles can permitstandoff great enough to safeguard even thesoftest of aircraft. I t is s t i l l d i f f i cu l t ,however, to envision a guidance and controlconcept which would permit effective and econ-omical attack against a wide variety of targetswith launch-and-leave missiles.

One interesting and unique possibility isthe use of large, efficient aircraft to carrysmall tactical aircraft to and from the sceneof engagement. Boeing and the Air Force havestudied 747s carrying "micro-fighters" andlarger aircraft are, of course, feasible.Previous experiments have shown that i t ispossible to launch and recover aircraft inf l ight , although many practical questions haveyet to be worked out. Whether and under whatcircumstances this might prove superior tof l ight refueling as a means of bringing tac t i -cal aircraft to distant targets is not entire-ly clear.

14

BASING

Historically, lack of suitable bases hasbeen a major deterrent to wider employment ofland-based aircraft for naval missions. Air-craft ranges have increased greatly but itremains important to have bases within 1000 to1500 nautical miles of important operatingareas, as can be seen from Figure 6. So faras sea-lane protection is concerned our presentbasing situation is reasonably satisfactory,as can be seen from Figures 2 and 3 (except,of course, for the lack of adequate intercep-tor bases in the North Pacific). Since thesebases are, for the most part, either in U.S.territory or in the territory of nations whowould be depending upon us to aid in theirown defense it is reasonable to feel fairlysanguine about the availability of these basesin a major maritime war.

Nevertheless, it is certainly possiblethat there could be circumstances which woulddeprive us of the use of one or another impor-tant base. It is in just such circumstances,of course, that the longer range offered byadvanced aircraft would be of greatest value.Figure 10, taken from reference 13, gives anidea of the coverage which could be providedby aircraft of various radii operating exclu-sively from bases in U.S. territory.

There is still ansther virtue to rangeas it affects basing: with long-range aircraftone needs fewer primary operating bases. Thisis a significant economy, and could help toreduce the need for stationing American squad-rons in allied territory in peacetime.

CONCLUSION

If there were a naval war tomorrow, land-based aircraft would play a major role on bothsides. The technological means exist to in-crease this role, and it may well be militar-ily and economically attractive to do so.

Much can be done */ith adaptations ofexisting types of aircraft, but there may be

good reason to develop advanced aircraft forland-based naval missions. There is consid-erable scope for multi-mission application tospread development costs and increase learn-ing benefits.

Land-based aircraft offer significantpotential advantages of mobility, flexibility,survivability, and economy for many navalmissions. These advantages should be system-atically and thoroughly explored and vigorous-ly exploited.

APPENDIX A

The data plotted in Figures 4 and 5 werederived from a yery simplified parametric air-craft characteristics model, described here.For both the moderate development aircraft(MDAC) and the intensive development aircraft(IDAC) it was assumed that the aircraft flewat a constant speed of 432 knots (equal toMach 0.75 at 36,152 feet) in both cruise andloiter. (In fact, of course, any reasonableaircraft will loiter best at a speed well be-low that for best range cruise, but the con-stant speed assumption does not introducelarge errors in the results of greatest inter-est and is compatible with the model 's crudelevel of detail. )

For the MDAC the use of a current or near-current (e.g., JT10D or CFM56) high-bypassratio turbofan engine is assumed. The IDAC,as indicated in the text, is assumed to useadvanced turboprop engines turning advanced,highly-loaded high-speed props or "prop-fans"(14, 15). Other technological aspects are asdescribed in the text.

Air range has been calculated from one oftwo alternate forms of Brequet's range equa-t ion, depending on propulsion type:

R = LLMÙ In wWe+ mWf

= 3 2 5 ' 9 ( P T F CYkW

(A-l)

(A-2)

Fig. 10 - Coverage versus radius from bases inU.S. territory (Rand)

where,R = Air range (no wind) in nautical milesV = Speed = 432 knotsi? = Prop aircraft propulsive efficiencyTSFC = Thrust specific fuel consumption

for je t aircraftPSFC = Power specific fuel consumption

for prop aircraf tL/D = Lift/drag ratioW = Takeoff gross weightWe = Empty weight, fu l ly equippedWf = Weight of fuel at takeoffm = Fraction of fuel retained as reserve :

0.12

15

Radii are calculated from the following equa-tion:

3001

r(h) = (R - hV)/2where,

(A-3)

r(h) = Radius with h hours spent on stationThe basic weighi: equation employed is,

W = We + Wf (A-4)

= Wu + Wp + Wfwhere,

Wu = Unequipped empty weightWp = Payload wei ght

Here, as throughout the payload is taken asincluding all mission avionics (but not basicflight avionics equivalent to airline standard),armament (but not weepons bay structure), mis-sion stores, crew, ard effects.

Figure A-l presents the weight data used,while Table A-l shows the other input dataassumed.

REFERENCES

1. Admiral S. 6. Gorshkov, "MorskayaMosch1 Gosudarstva." ("The Sea Power of theState"), Moscow, Military Publishing House,1976.

2. K.G. Wilkinson, "The Technology andEconomics of Air Transport in its Next Phase."Aeronautical Journal, March 1976.

3. J.P. Woolsey, "Uncertainties CloudFuture U.S. Airplane Programs." Air TransportWorld, April 1977.

4. M.D. Ardema, "The Feasibility ofModern Airships - Preliminary Assessment."9th AFGL Scientific Balloon Symposium, Ports-mouth, NH, October 1976.

5. R.G. Smethers, "A Modern Technology,Open-Ocean Seaplane Design." S.A.E. Paper760922, Aerospace Engineering and Manufactur-ing Meeting, San Diego, CA, Nov-Dec 1976.

6. Secty. of Defense D. H. Rumsfeld,"Annual Defense Department Report, FY 1978."Washington, DC, Dept. of Defense, 17 January1977.

7. V.D. Sokolovskiy, "Soviet MilitaryStrategy", edited by -J.F. Scott, New York,Crane, Russak & Co., 3rd Edition, 1975.

8. W.D. O'Neil, "Backfire - Long Shadowon the Sea Lanes." U.3. Naval Institute Pro-ceedings, March 1977.

9. C.L. Johnson, "Some DevelopmentAspects on the YF-12A Interceptor Aircraft."Journal of Aircraft, 7. 7 No. 4 (Jul-Aug 1970).

10. B.R. Rich, 'F-12 Series AircraftAerodynamic and Thermodynamic Design in Retro-spect." Journal of Aircraft, V. 11 No. 7(July 1974).

200-

a 100-

Wp = PAYLOAD WEIGHT = 45,0001b

Wf = FUEL WEIGHT =W - Wu - Wp

MODERATE-DEVELOPMENTAIRCRAFT (MDAC)

INTENSIVE-DEVELOPMENTAIRCRAFT (IDAC)

100 200 300 400 500GROSS WEIGHT - THOUSANDS OF POUNDS

Fig. A-l - Weight assumptions

Table A-l - Input Assumptions

60

TSFC

PS FC

1

L/D

Modéra te -Deve lopmen tAircraft (MDAC)

0.667 l b . / l b -h .

-

-

18

Intensive-DevelopmentAircraft (IDAC)

-

0.330 lb./SHP-hr.

0.82

20

11. L.K. L o f t i n , "Toward a Second-Gen-erat ion Supersonic Transport." Journal o f A i r -c r a f t , V. 11 No. 1 (January 1974).

12. Gen. G.C. Brown, "U.S. M i l i t a r yPosture for FY 1977." Washington, DC, Jo in tChiefs o f S ta f f , 20 January 1976.

13. W.T. Mikolowsky and L.W. Noggle,"An Evaluation of \lery Large Airplanes andAl ternat ive Fuels." Santa Monica, CA, RandCorp. Report R-1889-AF, December 1976.

14. A.H. Jackson and B.S. Gatzen, "Mu l t i -Mission Uses for Prop-Fan Propulsion." AGARDConference on Variable Geometry and Mult icycleEngines, Par is, September 1976.

15. B.S. Gatzen and S.M. Hudson, "GeneralCharacterist ics of Fuel Conservative Prop-FanPropulsion System." S.A.E. Paper 751085,National Aerospace and Manufacturing Meeting,Culver C i t y , CA, November 1975.