English Electric Lightning

The English Electric Lightning is credited with a single kill, ironically a British aircraft – a Harrier pilot ejected and the pilot-less aircraft continued to fly.

The order was given to shoot down the aircraft and the Lightning did.

In their final years of UK service all RAF Lightnings were based at RAF Binbrook in Lincolnshire and many were camouflaged to make them less conspicuous when flying at low level.

They tended to defend the Flamborough Head Sector of airspace above the North Sea.

These later aircraft were the single-seater F.3 and F.6 and the twin seat trainer variant T 5, all constructed by British Aircraft Corporation and distinguished from earlier versions by their flat topped fins. In their last year of service their pilots regularly pushed the aircraft to their limits as they used up their remaining fatigue life.

Interception d'un Tu 95

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Many Lightnings are conserved in museum collections where their clean sleek lines are evocative of the high speeds that they once attained.

The Short SB5 and a P 1A are at the RAF Museum, Cosford.

The Civil Aviation Authority refused a licence for the surviving airworthy examples to perform at air shows in the UK but there are three flying in South Africa

Service in the Middle East: Saudi Arabia and Kuwait

In December 1965, due to its involvement in the North Yemen Civil War and resulting conflict with Egypt, Saudi Arabia ordered 35 Lighting F.53s and six T.55s as part of the "Magic Carpet" programme. As an interim measure, five Lightning F.52s (ex-RAF Lightning F.2s) plus two Lightning T.54s (ex-RAF Lightning T.4s) were delivered to Saudi Arabia in July 1966, as well as a pre-production Lightning F.1 for ground instructional use.

From 1967 the Lighting F.53s operated from the Khamis base, served by radars based at Usram.
The last Lightning was delivered in 1972, during Magic Carpet phase IV. Only one plane was lost to enemy fire; it was shot down by ground fire over Yemen on 3 May 1970, just before peace was declared.

Kuwait also ordered 14 Lightnings in December 1966, comprising 12 F.53Ks and two T.55Ks.

The Kuwaitis somewhat overestimated their ability to maintain such a complex aircraft, and the Lightings were phased out of service very quickly; the last ones were replaced by Dassault Mirage F1s in 1977.

Thanks to this mistake, Kuwait is one of the countries richest in Lightnings on static display; according to Intelligence sources, the Al Jaber air base has three Lightings on display.

Performance

Speed

The maximum speed of the Lightning varied with the model.

The early models, the F.1, F.1A, and F.2, had a rated top speed of Mach 1.7 at 36,000 ft in an ICAO standard atmosphere, and 650 KIAS (Knots Indicated Airspeed) at lower altitudes.

The later models, the F.2A, F.3, F.3A, F.6, and F.53, had a rated top speed of Mach 2.0 at 36,000 ft, and speeds up to 700 KIAS for “operational necessity only.”

These were service limits, and were exceeded on occasion, but when the bases for these limits are understood, some of the “Lightning lore” associated with higher speeds can be placed into perspective.

The first basis for these limits was excess thrust. With the Avon 200-series engines, an early model Lightning with a ventral tank and two Firestreak missiles would run out of excess thrust at Mach 1.9 on a Standard Day.

With the Avon 300-series engines, a Lightning with a ventral tank and two Red Top missiles would run out of excess thrust at Mach 2.0 on a Standard Day.

As excess thrust decreases toward zero, acceleration slows, and fuel to achieve the last few tenths of a Mach could be prohibitive.

Another basis was aerodynamic stability. As Mach number increases, directional stability decreases.

This decrease in stability can become critical with asymmetric missile carriage or adverse yaw induced by aileron deflection.

Failure of the vertical fin could occur if yaw is not rapidly corrected with the rudder.[nb 2] Stability degradation led to the imposition of Mach limits on missile launch[nb 3] and to the adoption of a larger vertical fin on later Lightning variants to provide more stability margin at high Mach numbers.

Inlet stability was also an issue as Mach number increased. At supersonic speed, the central shock cone served as a compression surface to divert air into the annular inlet. The cone would generate an oblique shock, and the angle of this shock would increase with Mach number.

As the Lightning accelerated through Mach 1, the oblique shock would be positioned in front of the intake lip.

This is termed a subcritical inlet condition, and although not efficient, it is stable. In a sub-critical inlet, some portion of the compressed air is diverted outside of the inlet lip, causing spillage drag.

When Mach number reached the Design Mach number, the oblique shock would be positioned just in front of the inlet lip. This critical inlet condition is the most efficient, compressing all of the air in front of the inlet with no spillage.

English Electric Lightning at the Ysterplaat Airshow, Cape Town.

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As Mach number increases beyond Design Mach, the oblique shock enters the inlet, a condition termed supercritical. In a super-critical condition, the airflow in the inlet duct becomes supersonic.

The Lightning’s inlet was designed to handle only subsonic air in the duct, and a super-critical condition would reverse the normal pressure distribution, causing an adverse pressure gradient across the engines.

This adverse gradient could lead to engine surge, also called compressor stall, potentially resulting in flameout and/or engine damage. In any case, if the Lightning’s inlet went supercritical, engine thrust would be drastically reduced.

A supercritical condition could be delayed by translating the shock cone forward with increasing Mach, thus holding the oblique shock ahead of the inlet lip.

The goal would be to delay shock ingestion to a Mach number above the speed range of the aircraft.
The Lightning’s nose bullet was fixed, however, so a supercritical condition was inevitable if excess thrust enabled the aircraft speed to exceed the inlet’s Design Mach.

The final bases for the service limits were thermal and structural. When air is compressed by the passage of a high-speed aircraft, that air is heated.

This heating increases considerably when the aircraft is traveling at supersonic speed. The front of the aircraft is exposed to the heated air, and the heat is convectively transferred to the airframe.

The hottest portion of the aircraft is the nose tip, and in the Lightning’s case, this tip, the inlet shock cone, was constructed of fiberglass.

Fiberglass was necessary because the shock cone was also the Lightning’s radome, and a metal shock cone would not pass the AI 23’s radar energy.