FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1985
1985 - 0741.PDF
^L:LMl-.^M/-.'M i •.•••• Wim • Optica revisited It was difficult to find the grass runway at Old Sarum. Yellow edge markers had been dusted by blowing snow, to blend with the white carpet of grass bristles. Ridges up to 3in high were spread across by the wind over 10 per cent of the surface. The 6in Parker-Hannafin wheels of Optica's wide-track "roll-proof under carriage took the uneven surface ruggedly on the rubber-under-compression shock absorbers. The nosewheel responded well as soon as the rudder pedals were deflected, in spite of poor surface traction. I made 360° turns in each direction in little more than the declared radius, using only occasional bursts of power to get through the sticky patches. This needed judgement, because the fan blades seemed to bite suddenly in the middle range of r.p.m. and the machine leapt forward along the line I was trying to follow. There is no differential braking, but manoeuvrability under these unfavourable conditions justified the decision to keep this option in the background of design changes. The nose leg, sprung on tensioned rubber, is offset to the left and placed between the two pilots, who sit in the left and centre seats of the triple layout, with the instrument cluster on a stalk between them. Left turns are tighter with this layout. Balance of the set-forward cockpit and baggage compartment is geared to two pilots. Extra passenger weight must be balanced by a 421b/19kg weight housed in the starboard fin (soon to be split and put in both fins); with only one pilot ballast must be carried in the nose. Runway 06 was defined by the tracks of previous flying. I lined up with a path that would minimise ridge crossings, released the handbrake—which springs down as its catch flicks off with up pressure—and started a 10" flap take-off. The five Hydulignum fan blades are fixed, clearing FLIGHT International, 16 March 1985 As Edgley gains UK certification for its ducted fan Optica, Harry Hopkins samples this unique observation aircraft, which has benefited from increased power since our previous test. FLIGHT-TEST Edgley Optica the cowl by l-5mm. Engine control is single-lever and more familiar to those with mainly jet experience. The sound of the six-cylinder injection 260 h.p. Avco Lycoming IO-540-V4A5D engine was more turbine-like than I expected and, of course, there was no propwash to slap the nose. At 30kt the Optica was biting occasional snow ridges each side, giving a moment's hesitation in acceleration but very little swing. Forty knots and it began to bound on the hard earth beneath. At our 55kt VR slight back-pressure on the stick and the meeting of an upslope provided a sort of ski-jump take-off. Following V2 at 60kt, climb-out came at 70kt. With myself at 1801b and an undeniably lighter Chris Chadwick (Edgley test and demonstration pilot), take-off weight was set at around 2,5001b, 2251b below maximum; calculated take-off distance to 50ft was 1,150ft. The crosswind was more than lOkt and gusting, so ground handling was an indi cation of ability to get airborne in the conditions when pipe/powerline inspec tion or road-traffic policing duties might be most needed. We turned south at 600ft to clear Boscombe Down's circuit, then climbed at 70kt IAS to 5,000ft, averaging 900ft/min climb rate and, in the cold conditions, bettering the book figure by more than 150ft/min. The turn made clear what excellent all- round vision the cockpit transparencies offer. Look-out for several low-level radar targets needed little head movement and no manoeuvre. The helicopter-like cockpit bubble provides incredible vision well back overhead and along the near-side boom—even to see traffic at "six o'clock" back through the fan cowl! Angles of 270° in the vertical and 340° in the horizontal plane are claimed, with 60° down over the feet. Night flying has shown the vision to be almost eerie. Little of the frames can be seen; the impression is of being sur rounded by lights. Aerial work at night is intended. A decision will soon be made whether to retain only the nose landing light, or to fit "eyebrows" to the present lights on the main undercarriage legs to avoid direct light into the cockpit. The ICI Perspex is said to be free from significant internal reflections, except at the top edges of the doors. The ailerons produced a moment of adverse yaw as I rolled into a turn. This settled into a steady turn which, unlike that of the typical light single, needed no rudder to speak of. At 30° bank and 70-80kt, spiral divergence was neutral. Clear of the 2,000ft haze layer and surface turbulence, I was able to say that it was rock steady. It was also nice to fly a single where power increase gave no yaw, just a pitch-up. Roll control is moderately spring loaded to centre (to meet certification conditions for side-slip hands-off) and a modified wooded wing tip has been flown. All control runs have been much lightened
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
