The Aviation Historian — January 2018

32 THE AVIATION HISTORIAN Issue No 22

The fuselage consisted of heavy-gauge skins

over closely-spaced frames and stringers, and

the flying surfaces were formed of integrally

machined skins with supporting ribs and light

spars. The wing, made in port and starboard

halves, passed through the fuselage and the

inner part of each wing panel, between the front

and rear spars, formed an integral tank. The

flaps, ailerons and rudder, as well as the trailing

portions of the slab all-moving tailplane, were

made with the skins Hidux-bonded to a light-

alloy honeycomb core, this form of construction

giving a low weight with a very high torsional

stiffness and proving particularly suitable for

trailing-edge controls. The aircraft’s frontal area

was kept to a minimum and the fuselage was

waisted over the wing; airbrakes were positioned

on the corners of the upper rear fuselage. A single

25ft (7·6m)-diameter tail parachute was carried.

The navigation and reconnaissance systems

Included in the January 1958
brochure was this schematic
drawing showing the P.1129’s
antennae installations. The aerials
marked Violet Picture refer to
the homing system fitted to RAF
aircraft to locate aerial tankers,
among other uses. The X-band
sideways-looking aerials forward
of the intakes were housed within
apertures covered with
dielectric material.

The P.1129 was to use conventional light-alloy
construction, as the performance spectrum did
not justify radical changes in either materials
or methods of manufacture. Experience with
the P.1121 had shown that this philosophy was
justified, and that ground-attack duties at speeds
up to 850kt at sea level were compatible with
short-period penetrations to speeds above Mach 2
in the stratosphere, with negligible complication
of design or cost in structure-weight. Although
flight at supersonic speed at sea level was
extremely uneconomical, it was recognised that
use might be made of such a capability under
extreme circumstances.
The low-altitude design limit was therefore
selected as 850kt equivalent air speed (EAS),
corresponding to Mach 1·3 at sea level and Mach
1·4 at 5,000ft (1,500m). At medium altitude a high
value of design EAS was unnecessary and a limit
of Mach 2·3 was selected on the basis of a steady-
state boundary-layer temperature of less than
170°C (338°F). Choosing higher Mach numbers
would have led to higher kinetic temperatures,
and consequent weight penalties in the airframe
and engine owing to the need for a more
widespread substitution of steel and titanium for
light alloy in components. The P.1129’s absolute
ceiling would be at least 60,000ft (18,000m) and
the cockpit pressurisation would give a cockpit
altitude of 21,000ft (6,500m) at that altitude.

TAH ARCHIVE

TAH ARCHIVE

RIGHT The brochure included illustrative figures
for various sorties the successful GOR.339 candidate
would be expected to fulfil, including this one showing
a normal sortie profile with a 600-mile (1,100km)
radius, although this was later increased to a 1,000-
mile (1,800km) radius. The fuel reserve for landing had
to be enough for an 8min loiter at 1,000ft (300m).