Aviation Classics 7 Avro Vulcan preview

Avro Vulcan B2 XH558 taxies towards the camera in impressive style with a haze of hot exhaust fumes trailing behind it. Luigino Caliaro

Contents

6 Delta delight!

8 Vulcan – the Roman god of fire and destruction!

10 Delta Design 12 Delta Aerodynamics 20 Virtues of the Avro Vulcan Nos.1 and 2 22 The ‘Baby Vulcans’ 26 The True Delta Ladies 32 Fifty years of ’558 40 Virtues of the Avro Vulcan No.3 42 Vulcan display 49 Virtues of the Avro Vulcan No.4 52 Virtues of the Avro Vulcan No.5 53 Skybolt 54 From wood and fabric to the V-bomber 4 aviationclassics.co.uk

62 Virtues of the Avro Vulcan No.6 64 RAF Scampton – The Vulcan Years 70 Delta over the Ocean 72 Rolling!

74 Inside the Vulcan 78 XM594 delivery diary 86 National Cold War Exhibition 88 Virtues of the Avro Vulcan No.7 90 The Council Skip!

94 Vulcan Furnace 98 Virtues of the Avro Vulcan No.8

Left: Avro Vulcan B2 XH558 caught in some atmospheric lighting.

Cover: XH558 banked to starboard above the clouds. Both John M Dibbs/Plane Picture Company Editor:

Jarrod Cotter editor@aviationclassics.co.uk Dan Savage Gary R Brown, Rick Coney, Luigino Caliaro, Martyn Chorlton, Juanita Franzi, Howard Heeley, Robert Owen, François Prins, JA ‘Robby’ Robinson, Clive Rowley.

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ISBN No 978-1-906167-38-7

110 Virtues of the Avro Vulcan No.9 111 New memorial for the ‘Dam Busters’ 112 Vulcan versus Lightning 116 Waddington’s Warrior

Having trouble finding a copy of this magazine? Why not just ask your local newsagent to reserve you a copy

122 ‘Black Buck’ 129 Virtues of the Avro Vulcan No.10

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Avro Vulcan 5

XH558 overflies RAF Waddington in Lincolnshire on 7 September 1992; later that month it was retired from its status as a military display aircraft. It was at this base that XH558 arrived on 1 July 1960 becoming the first Vulcan B2 delivered to the RAF, took off for the final RAF Vulcan sortie on 23 March 1993, and carried out its first public air show display in civilian ownership on 5 July 2008. Cliff Knox

Delta delight!

W

hen the prototype Vulcan VX770 first appeared at Farnborough in 1952, it rightly stole the show! A four-engined Delta-winged jet bomber, it represented a massive leap in technology over its famous Lancaster predecessor which had been a war-winning aircraft only seven years earlier – the Vulcan could fly more than twice as fast, more than twice as high and more than twice as far.

Considering that it soldiered on in operational service into the 1980s, the fact that it was conceived in 1947 shows how advanced its design was for the time. Specification B35/46 was issued in January of that year, and called for a high-performance, long-range, jetpowered bomber capable of carrying and delivering a nuclear weapon. Roy Chadwick’s early design work was submitted just four months later, though sadly this great British designer never lived to see the Vulcan fly.

Once into RAF service the type certainly made its mark, with, for such a large aircraft, performance and manoeuvrability that can still take your breath away to this day.

Vulcans formed part of the V-Force, standing on constant readiness as a nuclear deterrent during one of the most tense and dangerous 6 aviationclassics.co.uk

periods in world history following the onset of the Cold War. The fact that it succeeded in its role as a major deterrent at the sharp end, and that the Vulcan wasn’t used for offensive operations until 1982, is something we should all be grateful for. Had it been called into action in the 1950s or 1960s for its intended operational capability of that time, the outcome would have been the selfdestruction of much of the human race.

When it was used offensively during the Falklands War of 1982 it was on the verge of being phased out. By then, as it was naturally envisaged the mighty V-bomber would no longer ever be needed for such operations, the bomb hoists for the Vulcan’s payload of 21 1000lb HE bombs had been disposed of – so RAF ground crew were reportedly despatched to scrapyards all over Lincolnshire to recover some! Well into its twilight years, the Vulcan then achieved the longest bombing raid ever undertaken; a round trip totalling 7700 miles.

At that time there was also a requirement for the Vulcan to briefly fulfil a shortfall in the tanker fleet, before XH558 soldiered on with the Vulcan Display Flight until 1992 as the RAF’s last flying example of its type. After being sold into private ownership and carrying out ‘fast taxi’ runs at Bruntingthorpe

for several ensuing years, XH558 made its triumphant return to flight in civilian hands in 2007 – the result of one of the most complex and challenging returns to flight ever undertaken in aviation preservation.

This issue of Aviation Classics looks at many aspects of the Vulcan story, from the roots of Roy Chadwick’s early Avro designs, through the writings of Avro personnel of the early 1950s and the first flight of prototype VX770, on to its military operations including the Falklands, and right up to XH558’s latest financial appeal which went to the wire in October 2010. I hope the selection of articles and photographs we have assembled for this publication prove a fitting tribute to the Vulcan in general, and in particular mark XH558’s 50th anniversary in suitable fashion. How strange things work out sometimes; the first B2 delivered to the RAF became the last to fly in military hands, and now the oldest complete Vulcan in the world is the only example of its breed to remain in airworthy condition. Long may Jarrod Cotter it continue!

Editor

Photo © John Dibbs

A True Story of British Grit and Determination to succeed against all the odds.

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Vulcan

the Roman god of fire and destruction!

The specification for the V-bomber which was issued in 1947 represented more than a 100% increase in speed and altitude capabilities than Avro’s final piston-engined bomber design in service with the RAF, the Lincoln. Time Line Images

Delta Design

Contemporar y background notes on the reasoning behind the design of the Vulcan written by SD Davies of Avro during the type’s development.

M

any people, and not only those connected with the aircraft industry, are speculating on the reason for AV Roe and Co Limited designing and building the 707 series of Delta research aircraft, the first of which appeared at the 1949 SBAC [Society of British Aerospace Companies] show. After all, the name of Avro is closely associated with the very much larger aircraft, such as the Lancaster, Lincoln and Shackleton in the military field and the Tudor in the civil field.

The little 707s seem to be a complete departure from this tradition. The reason is partly explained by the fact that the aircraft are research aeroplanes and are intended to find out more about the flying qualities of this sort of an aeroplane which is known as a Delta, because of the close similarity between the wing plan form and the Greek letter Delta.

We, like other large aircraft concerns, cannot afford to stagnate and merely produce the

Seen at the 1953 SBAC Farnborough Air Show on 3 September are Vulcan prototypes VX770 and VX777, joined by all four surviving Type 707s for a stunning Delta formation.

Time Line Images

10 aviationclassics.co.uk

same basic type with miscellaneous detailed alterations and improvements as the years go by. The advent of the jet engine has raised the performance levels of all military aircraft and also long-range commercial aircraft, and with the radical change in power plant must come equally radical changes in the airframe to match it. Considering that a military bomber or commercial transport is essentially an aircraft designed to carry pay loads for relatively long distances, the basic aerodynamic problems are rather similar and just as from a military point of view the highest possible cruising speed is necessary, so in the case of a transport aircraft, it has been proved that high cruising speed can lead to overall economy and the lowest overall cost per passenger/mile. From an economical point of view there is a limit to the cruising speed which as is well known, is set by the so called ‘barrier’ of the speed of sound. Some aircraft have flown faster than the speed of sound, but it is not yet an economical

proposition to attempt to cruise for long distances at these speeds. However, the nearest one can get to it the better, and it is this consideration which starts the designer thinking on radical lines.

In order to fly economically the aircraft must have the minimum possible drag and in order to keep the drag down at speeds approaching that of the speed of sound it is necessary for technical reasons to sweep the wings back at a very pronounced angle to the fuselage. Also it is necessary to keep the thickness of the wing as low as possible in terms of the chord; that is to say, whatever the wing chord is at any particular point along the span, the thickness should be kept down to a value of 10% of the chord or even less. Furthermore, if you want to fly at a true air speed and go as far as possible with an economical fuel load, it is well known that you must go as high as possible where the air is less dense.

Unfortunately, the speed of sound drops with increasing altitude and, therefore, as you design to fly higher, you must not only take the steps mentioned previously but in addition you must keep the angle between the wing and the flight path (known as the angle of incidence) low or else the drag will rise rapidly. In order to keep the angle of incidence low it is necessary to keep the wing loading low, or in other words, for a given gross weight of aircraft the wing area must be larger than we have become accustomed to in the last 15 years.

Another factor to be borne in mind, is that on a commercial aircraft or long-range bomber, if you want to fly long distances you utilise wings of high aspect ratio; that is the span is largely relative to the chord; the ratio varying from, say, nine up to 14. This is necessary in order to keep down that part of the drag (known as the induced drag) which is the penalty we pay for the wing lift.

TRIANGULAR PLAN FORM

Now you can get a broad picture of what the designer of a large load-carrying, long-range aircraft is faced with, if he wants to fly at speeds comparable with the speed of sound.

He has at one and the same time to sweep the wings back, make them thinner, increase the area and keep up the span. This poses very great structural problems, and in fact to try to keep a really high aspect ratio and do all the other things simultaneously is economically impossible. One solution is to reduce the aspect ratio, in order to keep the structure weight down, and let the induced drag rise with the hope that so much saving can be made on the rest of the drag that the total will still not be too high. If you combine what is structurally desirable with what is necessary aerodynamically you soon arrive at the solution that the best thing to do is to taper the wings very drastically so that in the limit the plan form becomes triangular in shape.

A little thought will show that with such a wing the required sweep back is achieved and a large area can be automatically obtained at the lowest possible structure weight, since the area out at the tip which causes the big bending loads on the wing structure is reduced to a minimum and, therefore, such a wing of large area can be obtained with the minimum possible structural penalty. Furthermore, our aim of keeping the wing at the centre portion nearest the fuselage is quite large in terms of feet and inches.

We now find that as an interesting byproduct of the theme we have got a relatively large usable volume in the wing that can be used for packing away the engines, undercarriage, fuel, etc, so that the excrescences hitherto so evident on the wing of an otherwise clean aeroplane have completely disappeared. Furthermore, the thickness of the wing at the centre is sufficiently large as to absorb the fuselage almost entirely so that it is reduced virtually to a streamlined projection ahead of the apex of the triangle.

Another by-product of this type of wing with its low loading is that no special devices such as slots or flaps are necessary to keep the landing speed down. The wing loading is sufficiently low as to enable quite normal take-off and landings to be done on existing aerodromes. Once we have abolished the need for landing flaps, which produce big changes of trim that have to be balanced out by the tail, the very need for the tail itself becomes questionable. The large wing chord of the Delta type of wing enables us to fit elevators at the trailing edge of the wing and these elevators have sufficient power to enable the aircraft to be flown through all normal manoeuvres.

We thus, by a fairly logical process arrive at an aircraft capable of high cruising speeds for long distances with a respectable pay load and consisting of nothing more than a smooth wing, streamline fuselage nose and vertical fin and rudder to look after directional control. If we have done our calculations properly we have now reduced the drag to the absolute minimum possible, and, therefore, have achieved, whether by military or commercial standard, the highest possible cruising efficiently.

Technically, therefore, the case for the Delta on paper is proved provided that in fact it flies in a respectable manner and does not suffer from hidden vices which have been overlooked in thinking only of the performance. Any aircraft company interested in the large type of aircraft cannot afford to ignore the possibilities of the Delta configuration. It is one thing, however, to prove a theoretical case on paper and it is another to sell it to the customer. What more obvious step, therefore, to take than to build a small one and fly it and this the Avro Company has done.

This, however, is only the beginning of the story; to translate this rather hopeful lesson into a large and intricate piece of hardware such as a bomber or a transport aircraft requires an enormous amount of investigation into the engineering details and

A page from the original manuscript on the background of Delta design

by Avro’s SD Davies.

Below: Having been towed down the A15 from Avro’s facility at Bracebridge Heath, Avro 707C WZ736 is taken onto the airfield at RAF Waddington in February 1953.

Via Rick Coney

it is here where the designer’s art is more important than his science, where time is dictated by the speed with which materials can be obtained, fabricated and assembled equipment provisioned and tested, all of which adds up to a process which can run into many years.

The above is taken by kind permission from an original typed manuscript in the collection of Rick Coney, whose father David Coney worked for Avro during the development of the 707s and the Vulcan.

Delta

Aerodynamics More contemporar y notes from the time of the Vulcan’s development, this time by JR Ewans, Chief Aerodynamist at Avro, Manchester.

Rare early colour photo of Vulcan B1 XH497 as it breaks away from the camera ship.

12 aviationclassics.co.uk

S

o far as can be ascertained, the idea of using a triangular planform for aircraft wings, now known as the Delta wing, was first put forward in 1943 by Professor Lippisch, who will be remembered for his association with the Messerschmitt Company. His studies had led him to think that this planform was most suited for flight at speeds in the region of the speed of sound, where conventional aircraft designs were already known to be in trouble. By the end of the war, he had a number of Delta wing projects in hand, including an unpowered wooden glider which was intended to explore the low-speed properties of the Delta wing.

This was then partly built, and was later completed under United States orders.

The idea of the Delta wing was studied by many other aeronautical experts and a strong recommendation for its use was given, for instance, by Professor Von Karman, of the USA, at the 1947 Anglo-American Aeronautical Conference in London.

At the time of writing, three British Delta aircraft and two American are known to have flown, and it is pretty certain that others are on the way. In the date order of their first flight, these are: Consolidated-Vultee XF–92 AV Roe 707 Boulton Paul P111 Douglas XF-3D Fairey FD-1 With the exception of the last named, which is fitted with a small fixed tailplane for the first flights, all the above aircraft are tail-less.

The following notes are intended to give a logical explanation of why there is this considerable interest in the Delta wing, and just what advantages it promises the aircraft designer. To do this, we must consider the type of aircraft the designer is trying to produce.

THE DESIGNER’S AIM

Right at the beginning, it must be said that the Delta wing is of value only for very highspeed aircraft, and at the present stage of engine development, this implies the use of jet engines. When projecting his high-speed aircraft, the designer will attempt to produce an aircraft carrying the greatest payload for the greatest distance, at the highest speed, and for the least expenditure of power (i.e. using the least amount of fuel). This applies to all types of aircraft, whether bombers in which the payload is bombs, or civil aircraft, in which the payload is passengers or cargo, or fighters, in which the payload is guns and ammunition.

PROBLEMS OF HIGH ALTITUDE AND HIGH-SPEED FLIGHT

The most fundamental factor determining what is achieved is the height at which the aircraft flies. At higher altitudes, the density of the air reduces so that the aircraft drag is less and it is possible to fly at a given speed at say 40,000ft, for an expenditure of only one quarter of the power required at sea level.

Avro Vulcan 13

Superb head-on view of prototype Vulcan VX770, showing the sleek aerodynamic design of the type off to good effect. All Time Line Images unless noted

The advent of the jet engine has enabled the aircraft designer to get his aircraft up to considerable altitudes and takes advantage of the reduced drag; but a new factor is coming in to limit the speed of the aircraft. This is the speed of sound.

It has been shown in theory, and found in practice, that the speed of sound occupies a fundamental position in the speed range of aircraft. The speed of sound is actually 760 miles per hour at sea level, and falls off to a value of 660 miles per hour at heights above 30,000ft. Because the speed of sound is of such importance, aeronautical engineers relate aircraft speeds to the speed of sound, using the term ‘Mach Number’ defined as the ratio of the speed of an aircraft to the speed of sound at the same height. As an aircraft approaches the speed of sound – in fact for conventional aircraft when a speed of about

Topside view of a Vulcan showing the cranked wing design nicely.

70% of the speed of sound (i.e. a Mach Number of 0.7) is reached – the effects of compressibility become important and the characteristics of the airflow round the aircraft change fundamentally. There is a very large increase in the air resistance or drag, and an excessive expenditure of power becomes necessary to increase the speed any further.

For transport and bomber aircraft the speed at which the drag starts to increase (known as the ‘drag rise’ Mach Number) becomes the maximum cruising speed since if the aircraft is flown at higher speeds, the disproportionally higher thrust required from the engine means excessive fuel consumption and loss of range. At a rather higher Mach Number there will be changes in the stability of the aircraft and in its response to the pilot’s

control – leading possibly even to complete loss of control.

In order to progress along the speed range to higher speeds it is therefore necessary to design aircraft so as to postpone and/or overcome these effects.

We have noted that with an ‘old-fashioned’ type of aircraft design, i.e. that of jetpropelled aircraft current in 1945, the limiting speed in steady cruising flight is likely to be a Mach Number of 0.7 (higher speeds have, of course, already been achieved and a number of aircraft have exceeded the speed of sound, but only for short periods, either by diving or by use of rocket power).

From the knowledge available, however, it appears possible by careful aerodynamic design of an aircraft, to postpone the rise in drag until a Mach Number in the region of 0.9 is reached and this figure is likely to be the practical limit of cruising speed for transport aircraft of all types for many years to come. The designer of a civil aircraft, a bomber, or a long-range fighter, will, therefore, bend all his energies to achieving a Mach Number of this order without any drag rise. In addition he must pay attention to the changes of stability or lack of control which might occur in this region, and this will occupy his attention to the same extent as the purely performance aspect of the drag rise.

DESIGN FOR HIGH MACH NUMBER It is quite easy to design a fuselage shape which is relatively immune from Mach Number effects. It is the design of wings which is difficult, particularly since a wing that is suitable for high speed must also give satisfactory flying properties at low speeds, e.g. for take-off and landing.

Original aerodynamic graphs as referred to in the text. Avro via Rick Coney

As the air flows past a wing its speed is increased over the upper surface to a considerable extent and over the lower surface to a lesser extent, so that there is greater suction on the upper surface than on the lower surface. This difference gives rise to the lift which enables the wing to sustain the weight of the aircraft. Thus, whatever speed an aircraft is flying, the speed of the air around the wing will, in fact, be higher. In the case of an aircraft flying at a Mach Number of 0.8 the speed around its upper surface will be equal to, or may easily exceed the speed of sound. At this stage, the airflow pattern around the wing will be constantly changed, and it is, in fact, this change which gives rise to the drag and stability effects mentioned above. It is essential, therefore, to keep the velocity above the wing as little in excess of the speed of the aircraft as possible.

There are four ways of improving the high Mach Number behaviour of the wings. They are different methods, all of which can be applied simultaneously, of keeping down the air velocities round the wing. They are: Sweepback; Thinness; Low wing loading; Low aspect ratio.

We will consider each of these effects in turn.

The first prototype Vulcan VX770 seen from an impressive angle.

SWEEPBACK

The amount of sweepback is measured by the angle by which the tip of the wing lies behind the centre line. The extent of the gains possible from sweepback is very considerable, and sweeping a wing back may easily lead to a postponement of the compressibility effects by a Mach Number of 0.1. This is illustrated in Fig.1 which compares the drag rises of an unswept wing with that of a wing swept back 45ยบ. The drag rise of the former occurs at 0.7 and the latter is 0.83. Fig. 2 shows the way in which the drag rise Mach Number is increased by the sweepback.

A Vulcan B2 fitted with a Blue Steel nuclear stand-off weapon.

Avro Vulcan 15

THINNESS

Keeping a wing thin leads to the reduction in the amount of air that must be pushed out of the way by the wing. This helps the passage of the wing through the air. The thickness of a wing is measured by the thickness/chord ratio, which is the maximum depth of the wing divided by its length in the line of flight.

In the past, the thickness/chord ratios of an aircraft wing have ranged from 21% down to perhaps 12%. Now values of 10% down to 7% are becoming common. An indication of the result gained is given by Fig. 3.

Rear view clearly showing the layout of the four jet exhausts.

LOW WING LOADING

The wing loading is the weight of aircraft carried by a unit area of wing, measured in pounds per square foot. Mach Number effects are postponed by keeping the wing loading as low as possible, i.e. by supporting the weight of the aircraft with a large wing area. This is particularly important for flight at high altitudes where the low air density puts a premium on keeping the wing loading low. In fact, flight at high altitudes becomes virtually impossible unless this is done. Fig. 4 illustrates this.

LOW ASPECT RATIO

The three types which made up the RAF’s V-Force: a Handley Page Victor at top, then an Avro Vulcan, with a Vickers Valiant nearest the camera.

Aspect ratio is the ratio of the span of a wing to the average chord. For moderate speeds, a high aspect ratio, i.e. a large span relative to the chord, gives greater efficiency. At high Mach Numbers this consideration is no longer important, in fact, some alleviation of compressibility effects is given by reducing aspect ratio. This is shown in Fig. 5.

There is another reason for choosing a low aspect ratio. One of the disadvantages of sweeping a wing back is that the flying characteristics at low speed become worse. A typical symptom is that the wing tip of a swept back wing stalls, giving violent behaviour if the speed is allowed to fall too low. Research has, however, shown that this bad characteristic of highly swept back wings may be overcome relatively easily. Fig. 6 is a graph of sweepback versus aspect ratio,

Vulcan B2 XM603 served with 44 and 101 Squadrons and after being struck off charge was purchased from the MoD by BAE Systems and kept at Woodford painted in anti-flash white. Via François Prins 16 aviationclassics.co.uk

EARLY DELTA DEVELOPMENT TIME LINE January 1947 December 1947 January 1948 September 1949 September 1950 June 1951 August 1952 February 1953 July 1953 September 1953

Avro Vulcan B2A XM575 of 44 Squadron. This aircraft is now preserved at the East Midlands Airport Aeropark. Via François Prins compiled from a very large number of tests of wings of various plan forms. Each of these plan forms has been classified as giving good or bad characteristics. It will be noted that although almost any aspect ratio can be accepted with an unswept wing, for wings of 45º sweepback an aspect ratio of little over 3 is the most satisfactory.

There is yet a third reason for choosing a low aspect ratio – the behaviour (as regards stability etc) in the high Mach Number region. For reasons which it is not possible to go into here, compressibility effects are minimised and a transition from speeds below that of sound to the speed of sound and above is much more readily accomplished if the aspect ratio is low, say in the order of 2 to 4.

THE DELTA PLAN FORM

Put the above requirements together and the result is an aircraft with a highly swept back, thin wing, moderately large wing area and a low aspect ratio. A little consideration of geometrical properties and possible plan form of wings leads to the conclusion that the Delta wing is the only form which satisfied these requirements. It possesses high sweepback and low aspect ratio. The wing area will, of necessity, be generous for the size of the aircraft and for reasons which will be detailed later, it is easy to build it with a low thickness/chord ratio.

We must see how the Delta plan form, indicated from considerations of aerodynamic performance, lines up with practical design requirements, and in particular the overriding necessity for keeping weight and drag low in order to obtain a maximum performance. A preliminary question is whether a tailplane is necessary.

TO FIT OR NOT TO FIT A TAILPLANE?

From the earliest days of flying, the question has been raised as to whether aircraft can be flown satisfactorily without a tailplane.

Confining our attention only to the case of high-speed jet aircraft, we will examine each of the functions of a tailplane in turn, in relation to the Delta wing aircraft. A tailplane performs the following functions: a) To trim out changes of centre of gravity position according to the load carried and

b)

c)

d)

e)

the consumption of fuel.

Investigation shows that a control surface at the trailing edge of the wing, provided that the latter has a large root chord (as has the Delta), can cater for all but the extreme cg movements.

To deal with trim changes due to landing flaps etc.

With the low wing loading associated with the Delta wing, take-off and landing speeds are moderate without the use of flaps, and this question does not, therefore, arise.

To provide damping of pitching oscillations.

The reduction of damping of the pitching oscillation has led to difficulty on some tail-less aircraft, but it does not arise on the Delta since the large chord near the root gives adequate damping.

To deal with loss of stability or control power consequent on distortion of the wing structure at high speed (Aerolastic Distortion).

At very high speeds, all aircraft structures distort to a greater or lesser extent under the high loads imposed, and this distortion alters the aerodynamic form. In extreme cases this leads to a loss of stability or control power, making the aircraft dangerous or impossible to fly at high speeds. An aircraft with a high aspect ratio sweptback wing would need a tailplane to deal with this, but the shape of the Delta wing makes it extremely stiff, both in bending and in torsion, and a tailplane does not appear necessary.

To provide for spin recovery.

Although this point has not been proved, it is expected that the controls on a tailless Delta wing would not be powerful enough to ensure recovery from a fully developed spin. A tailplane appears to be the only way of dealing with this. This restriction is of no significance for transport or bomber-type aircraft for which spinning does not arise, but on fighter or trainer aircraft, a tailplane would appear to be a necessity.

It is, therefore, concluded that for a Delta wing aircraft of the transport type, a tailplane is unnecessary. Its deletion leads immediately to a considerable saving of weight and drag, and to a major gain in performance.

Design study began Prototype ordered 707 series proposed Avro 707 first flight Avro 707B first flight Avro 707A first flight Vulcan first flight Second Avro 707A first flight Avro 707C first flight Second Vulcan first flight

REDUCTION OF MECHANICAL COMPLEXITY

Compared with a conventional aircraft, the Delta wing aircraft will therefore be simpler by the omission of the following items: the tailplane, the rear fuselage necessary to carry the tailplane, wing flaps and other high-lift devices such as the drooped wing leading edge. There is a considerable saving of weight, of design and manufacturing effort, and of maintenance when the aircraft is in service.

These economies will have considerable bearing on the initial cost and the manpower necessary to produce and maintain a number of aircraft.

VALUE OF THE LARGE INTERNAL VOLUME

Because of its shape and the large root chord, the Delta wing provides a large internal volume in relation to its surface area, even when using the thin wing sections which, as we have seen above, are essential for high-speed aircraft.

Simple calculations show that for the same wing area, the Delta wing has 33% more internal volume than an untapered wing, while if the inboard half of the wing only is considered, as this represents a more practical case from the point of view of the aircraft designer, the internal volume of the Delta wing, is more than twice that of the corresponding untapered wing.

It is found that without exceeding a wing thickness of as little as 8% to 10% it is possible on a moderate-sized Delta wing aircraft to bury completely the engines, undercarriage and sufficient fuel tanks for a very considerable range. The fuselage also has the tendency to disappear into the wing at the root. The result is the attainment of an aircraft consisting only of a wing, a fin and a rudimentary fuselage, representing a degree of aerodynamic cleanliness which has never before been reached. In fairness, it must be pointed out that this is achieved at the expense of a rather larger area than usual, but investigation shows that the drag of this is considerably less than that due to a conglomeration of items such as engine nacelles, tailplane, etc.

Avro Vulcan 17

THE STRUCTURAL DESIGN OF THE DELTA WING

From the design point of view, the shape of the Delta wing leads to an extremely stiff structure without the use of thick wing skins, and strength becomes the determining feature rather than structural stiffness. This avoids the inefficiency of conventional sweptback wings where the wing has to be made stronger than necessary in order that it shall be stiff enough. It is found that the Delta wing lends itself to conventional design techniques, and to conventional methods of construction.

SUMMARY

Summarising the above, we have seen that in order to meet the requirements of large loads for long range, at high speeds, the high performance transport or military aircraft of the future will cruise at a considerable altitude, at a speed not much below that of sound. The Delta wing provides the only satisfactory solution to these requirements, for the following reasons: 1) It meets the four features necessary for avoiding the drag rise near the speed of sound, i.e. it is highly swept back, it can be made very thin, the wing loading is low, and the aspect ratio is low.

18 aviationclassics.co.uk

2) Extensive wing tunnel and flight tests have shown that the low aspect ratio Delta wing gives minimum change in stability and control characteristics at speeds near the speed of sound.

3) In spite of being thin, the internal volume is large, so that the engines, undercarriage, fuel and all the necessary equipment can be contained within the wing and a rudimentary fuselage.

4) Adequate control can be obtained by control surfaces on the wing, thus eliminating the need for a conventional tailplane. Together with item 3, this leads to considerable reduction in the drag of the aircraft, and, therefore, to high performance.

5) Auxiliary devices such as flaps, nose flaps, slots and the all-moving tailplane are unnecessary, thereby saving weight and design effort, and simplifying manufacture and maintenance.

6) The Delta wing is very stiff and free from distortion troubles.

The above is taken with kind permission from an original typed manuscript in the collection of Rick Coney, whose father David Coney worked for Avro during the development of the 707s and the Vulcan.

Above: Amazing photo of XH558 before retirement from the RAF. François Prins

First page of the original manuscript by Avro’s Chief Aerodynamist JR Ewans.