FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1964
1964 - 2117.PDF
FUGHT International, 23 July 19(4 Air-to-air photograph of the 221 in company with its Hunter chase aircraft. Manufacturer's flying is in the hands of Divisional chief test pilot Godfrey Auty Three-view drawing of the BAC.22I, with the original canopy fitted; ultimately an improved canopy will be installed, faired into the hydraulic-tank bulge. Span, 25ft; length, 57ft 7.I'm; height, lift 4in; aspect ratio, 1.22; t/c ratio, 4.5%; announced Mach limit, 1.6 (1,060 m.p.h.) BAC.221 . . . P. 1127 type and the No 2 being similar to that fitted to the 188. Typical of the increased complexity of the 221 hydraulics is the fact that the sequencing valves in the nose-droop and nose-under- carriage circuits provide for all eight possible sequences (e.g., nose- gear up and nose up, nose-gear up and nose down, etc); this complication is inherited from the fact that in the original aircraft the nose-gear doors had to be opened before the nose could be lowered, thus interconnecting both sets of sequences. Moreover the added capability in the 221 is accompanied by greater tank back-pressures and increased hydraulic loads. As already noted, all such system development had to be carried out on the aircraft itself. Electrics Although the basic generation remains unchanged, with a single 28V d.c. machine mounted on the powerplant, a pair of 750VA Hawker Siddeley Dynamics static inverters have been added primarily to supply the 115V a.c. loads to the auto- stabilization, heated windscreen and the now-mandatory UHF communications set and stand-by. One of these inverters is in the fuselage and the other in the wings. Their design is identical with the pattern originally specified for the Short Belfast; the latter aircraft now has rotary inverters, but considerations of space and heat-dissipation precluded their use on the 221, in which the solid- state units are working to complete satisfaction. An additional Ekco 150VA inverter serves the instrumentation. Instrumentation The UHF general-communications radio has already been mentioned. It is mounted in the nose, with its stand- by, where the VHF was in the FD.2. A procedure learnt with the Bristol 188 programme is to leave a transmitter channel on through- out each flight so that the pilot's comments may be simultaneously recorded on the ground and heard in the Hunter chase aircraft. Accordingly the 221 has a continuous-voice VHF transmitter for this purpose, together with an ad hoc receiver in the Hunter (which is now a single-seater, see picture). Basic research instrumentation comprises an automatic-observer panel photographed by a 35mm camera, together with eight Hussenot trace recorders. A crash recorder is also carried: a five- channel ADR.412A modified by Penny & Giles recording on wire normal and lateral acceleration, i.a.s., altitude and engine r.p.m. A 16mm camera is carried at the top of the fin to photograph the tufting used to indicate airflow at low speeds. Ultimately the whole aircraft will be painted glossy blue to provide a good background to the tufts; at present only the nose and tail have this finish. Pressure plotting is being accomplished with some 230 holes arranged in spanwise and chordwise rows on the port wing, with a few repeats on the starboard wing. Some of the sensing points near the leading edge also include thermocouples to determine the transition from laminar to turbulent boundary-layer. Signals from all these points are fed into a pneumatic scanning valve and thence through a transducer to one of the trace recorders. Another essential aspect of 221 clearance concerns flutter, which cannot be simulated at supersonic speeds. The 221 has LTU (lateral thrust unit) mountings at the top of the fin and above and below each wing-tip. These devices, colloquially known as "bonkers," are miniature rocket motors with brief burning time. There are numerous flutter transducers, and the output will enable BAC to complete the flutter curves begun with the ground-resonance programme. Provision is made for attaching a drogue at each wing tip and ballast at the wing tips, nose and tail. Strain-gauges are provided to record control-surface hinge moments. Ultimately WG774 will be delivered to the RAE at Bedford, but its flight clearance is being carried out from the manufacturer's airfield at Filton. The flying programme is in the hands of Godfrey Auty, chief test pilot of the BAC Filton Division, with "Willy" Williamson as back-up man and with a pilot from Bedford also participating. Initially the aircraft is being kept subsonic, and the primary purpose of each flight has been to explore handling at low speeds and prove the systems. Following this phase the aircraft has been spending a planned seven/eight weeks on the ground in its resonance programme, which is now complete. Major modifications to improve the canopy and cockpit interior have been postponed until later this year. BAC will complete their contract by extending the 221 flight envelope to its limits. This will take at least 50 flights; flutter clearance is scheduled before the end of the year, and autostabilizer clearance early in 1965. The aircraft will then be delivered to Bedford. The point has already been made that the 221 wing is not that of the Concord; the latter has different twist, camber, droop, a lower t/c ratio and is mounted low on the fuselage. The 221 leading edge is bolted on in four sections on each wing, but the droop of the Concord is required purely for cruise efficiency and is unlikely to be required on the 221. At the same time, the results achieved at high Reynolds number with the 221 should materially assist in establishing correlation between theory and model results, especially in view of the super-accurate model of the 221 shortly to be tunnel- tested at Bedford. In any case, the 221 should prove a valuable research tool in its own right.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
