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Aviation History
1998
1998 - 0036.PDF
FLIGHT TEST to accelerate/decelerate while in the turn, XV-15 is easy to stabilise in the hover: fuselage attitude can be adjusted'with cyclic androtor-tilt though there was little wind. Helicopter pilots will find these manoeuvres a delight. Fixed-wing meters on top of the instrument panel which We went from the fast to the slow, Ball allow- pilots have to work harder and need a little help, clearly show maximum continuous and maxi- ing me to stall the aircraft clean (ie, with flaps Landings were equally problem-free, espe- mum power. I held maximum continuous and and wheels up). Pure-helicopter pilots will, of daily with the level attitude. This aircraft does we achieved 222kt at 5,000ft. Bell's chief pilot course, need to remember at this point that they not suffer from the handling problems which said later that this was a bit low, but, in fairness, are flying a conventional wing and not a rotor, some helicopters have when hovering with me I did not hold the power on very long and I was and not try to fly too slow and low. Even this wind in certain sectors. The test pilots are not still searching for the perfect level attitude, early experimental aircraft is slick and it took a aware of any settling with power/vortex-ring Helicopter pilots will be impressed, and even while before I could get die speed down from characteristics. They think that a very high rate pilots of fixed-wing aircraft of comparable size more than 200kt to a little over lOOkt. of descent would be needed to achieve the entry and weight may be surprised. After some With lots of aft stick and nose-high attitude, conditions for the vortex ring to establish itself, climbs, descents, turns, some steep, all showing the aircraft eventually vibrated slightlyand con- benign characteristics, I lowered the nose to tinuously and started to sink This occurred as FIRST CONVERSION achieve the never-exceed speed (VNE) of 250kt. we decelerated through 1 lOkt. I watched the Now came the transition into forward flight. As rate-of-descent indicator on my display go the nacelles were tilted to 60°, I felt the thrust VIBRATION LEVELS from zero to ever-increasing numbers. I could through my body and off we went-unlike the Vibration levels remained much the same - feel the sink rate through my body, too. sensation in the V-22 simulator. All of the verti- impressively low. The V-22, the XV-15's big There was no wing drop or other effect, and caltake-offandlandingaircraftlhaveflownsuf- brother, has a higher V^- of340kt.TheXV-15 the recovery was benign and instantaneous. I fer from a loss of lift at this point because they experimental aircraft was not built for speed, but relaxed the large amount of back pressure I was lose the benefits of ground cushion and vertical for overall assessment of all tilt-rotor systems, holding on the stick, raised the power lever to thrust from the rotor/s before picking up the Even so, for a 20-year-old aircraft, I was about 60 % torque, and out she came and went benefits of forward flight such as translational impressed with its docility at this speed. Heli- straight into a climb.The aircraft has not been lift in the case of the pure helicopter (or wing copter pilots can forget about retreating-blade known to spin.The XV-15 is stressed to +3 to - lift, in the case of the tilt-rotor). The XV-15 is stall, reversed airflow and Mach-number drag 0.5G, although aerobatics are not allowed. The no exception, so the pilot has to be ready with on the advancing-blade tips in this aircraft. They V-22 limits are +3/ -2, a much wider range, the power lever to prevent an undignified sink, must remember, however, that, at what is for This caught me out in the simulator for the them a fast speed (120kt), this aircraft will stall. CIRCUIT WORK much larger V-22, where the nose went down The aircraft has a stabilisation system, more We were allowed to do a straight-in approach on rather hard and we lost some height. for research reasons than for handling necessi- our return to the airfield, so Ball gave me the chal- I anticipated nicely with the XV-15, however, ty, so it is extremely stable in all axes. Hands-off lenge of going for a marked spot on the crosswind and we climbed up. Ball brought up the under- flight produced no deviations from die straight taxiway. This is when both fixed- and rotary- carriage and reduced the flaps. I beeped the and level. We did not have time to explore han- wing pilots need to reprogramme their brains rotor rpm down to 86% and soon saw more dlingwith the stabilisation off, but I am told that and use the tilting rotors to maximum effect to than l20ktappearonmydisplay.Theclimbwas there are hardly any differences. control indicated airspeed combined with rate- continued, and the nacelles tilted to 0° and were Visibility throughout the cruise and turn of-descent and rate-of-closure indications. Ball locked. We accelerated rapidly. manoeuvres was above the average, given the dissuaded me from using the stick and got me to This research aircraft has two big torque large overhead windows and side panels. relyontlietiltcapability.Thetechniqueisdiffer- 34 FLIGHT INTERNATIONAL 7 - 13 January 1998
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