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Aviation History
1964
1964 - 1863.PDF
1034 BOEING 727 ... rather too light and powerful, particularly in view of the closely- spaced engines, but the yaw-dampers did their job well in damping out induced Dutch roll in perhaps one-and-a-half cycles. This was the height and speed regime for which they were installed. In the right atmospheric conditions, a shock wave 6ft to 7ft high can apparently be seen standing over the wing. I now spent a while in the rear cabin, while some checks were carried out, and appreciated the typically cheerful Boeing decor. Though everyone at Seattle is enraptured with the low noise level, I felt that it differed little from other rear-engined jets. A ring of perforations just inside the intake lips is intended to reduce intake noise. There was some machinery noise, which one expects in any unusually quiet aircraft. The wing, as seen by the passenger, is exceptionally tidy and remarkably small. The trailing-edge at the tips is, in fact, aft of the engine intakes, so Boeing have been able to install their fuel-jettison pipes there in a safe and convenient position. Back on the flight deck after a few minutes I was given the right- hand seat for some more handling. I was beginning to like the feel of the aircraft very much. The specially smooth ride and complete absence of engine noise are especially pleasant for a hard-working crew. McMurray switched off the yaw-dampers one after the other, and showed that the 727 still damped out Dutch roll rapidly under these conditions. The yaw-dampers have authority over 4° of rudder travel and an out-of-phase or runaway can therefore be adequately countered. Either rudder section is powerful enough to give all directional control needed. Asymmetric-power effects are very small, as I discovered when McMurray checked acceleration of an outer engine with aircraft flying hands-off in a 30°-banked turn. From idling at 55 per cent r.p.m., the middle engine throttle was slammed open and produced three distinct "choo-choo" thuds, but settled down by 65 per cent to accelerate smoothly. We were now still at 31,000ft, but back in the traffic-control jag, flying VOR headings over the fragmented pattern of lakes, sea inlets and islands of the Puget Sound area. Sno;v still lay above 3,000ft amongst the forests. The Sun was shining, and there was very little cloud. McMurray made some checks on the Sperry SP-30 autopilot which is standard 727 equipment. Autopilot- induced rate of roll is limited to 7°/sec when using the turn knob and 4°/sec when using the course selecter on the director compass. Bank angle limit is 32° ±5°. We flew a VOR-coupled leg and noted how the autopilot went into a heading-hold mode as soon as VOR signal strength and rate of course deviation combined to indicate station passage. VOR-hold is re-engaged automatically after a maximum interval of some lOOsec, but on this occasion we were coupled again after some 15sec. A compass problem then became apparent—one of a score of minor defects on this first flight—and we abandoned coupled flying. High Mach and q We now climbed for a series of checks at 39,000ft and accelerated to the MNO of 0.905 at 290kt i.a.s. Pressing on beyond MNO in a gentle dive the first warning "clacker" chattered at Mach 0.91, followed by the second at 0.92. I was given control at around this speed and the airbrakes were pulled to show their smooth decel- erating effect. With 300kt indicated we launched into a descent with the v.s.i. pegged at 6,000ft/min; actual descent rate was far higher. The airbrakes produced a nose-up trim change, but the air- craft remained perfectly light and manageable, with a remarkable absence of buffet, noise or other complications. Letting down to 20,000ft we pushed the speed up to the q limit at 412kt i.a.s. and duly got "clacker" warnings. The ailerons were now if anything lighter than before, but did not produce quite so good a rate of roll. During fairly brisk turns I noticed the yaw- dampers making quite large movements, to cancel adverse yaw. By 12,000ft there was an occasional inclination to begin Dutch rolling, but I was told to damp it by holding the wings level. There is usually no obvious technique for damping this type of oscillation. Instinctive corrective action tends to get out of phase and simply aggravate the situation. The 727 certainly did not stay in Dutch roll, and behaved itself very well. Early 707s would Dutch roll for ages, but the aircraft now in use have efficient yaw-dampers. FLIGHT International. 18 June 1964 McMurray now put me to work seriously. I had got the feel of the aircraft during take-off, climb and at high Mach and high q. He now proceeded to take out the hydraulic systems one after the other in successive axes. We were at 270kt and 21,000ft and the A system departed with only a barely noticeable loss of aileron response—nothing to worry about at all. When the B system was switched off the 727 reverted smoothly into manual with the lower rudder working on the stand-by system without yaw damper and the elevator and inner ailerons fully manual. The spoilers were not working. Control forces were certainly high, with a steep force gradient and apparently diminishing response beyond approxi- mately the half-deflection point on the ailerons. I really had to work hard to get into and out of a turn, but I would judge the con- trol response to be not greatly worse than, say, an early Shackleton at around llOkt. I remember having the same feeling then that, first, I would never get it to roll, and then that I would never stop the inexorable slow roll that finally started. Nevertheless, the 727 is palpably flyable in this condition, though it would have to be carefully managed for an approach, and a landing in gusty cross- winds should be strictly avoided if possible. I heard someone mention manual undercarriage extension, and was just wrenching the 727 into a turn when the nose-gear doors opened with a bang. For a moment I thought I had broken some- thing important. When the doors were opened and the three legs cranked down one after the other, the effect on control was imper- ceptible. At 200kt in manual, control was at its poorest, but very soon afterwards, at around 190kt, the outboard ailerons came into circuit and improved the picture considerably. We did not lower flaps, but there was the electric stand-by for them, and the leading- edges could be lowered with the stand-by system that was operating the lower rudder. At one point, one of our score of "squawks" turned out to be a lagging spoiler and I momentarily needed every bit of aileron to hold the 727 level. When I had been sweating for some time, the Boeing crew re-engaged the A and B systems at 200kt and I was back in civilized business. Runaway Trim I was then instructed to dive to 400kt at 12,000ft, and spent some time pulling airbrakes in and out, using them rather like the brakes on a car. With powerful applications the trim change with airbrake movement became quite strong as the aircraft got away from its original trimmed speed. The 727 should be flown trimmed at all times, and responds firmly to changes in speed. While we were in- volved with trim, Tom Lane in the right-hand seat set his tailplane thumb-switches to full nose-down and the trim wheel began to whirr round. He told me to hold the nose still, which I did as the force built up, and after a few seconds it seemed as if someone had put a walking stick into the trim wheel. It locked solid of its own accord, and I was able with some effort to hold the out-of-trim force, though Tom still had his thumb hard on the switches. He operated the slow-rate trim switch and it too was disabled. The drill then was to operate the trim-motor cut-out switch on the con- sole, extend the handle on the trim wheel and wind it manually back to the trimmed position. It is this automatic cut-out that eliminates the old 707 drill of grabbing the trim wheel to stop it rotating. Manual trimming was easy and the folding handle allowed the wheel to be turned quite rapidly. Aileron and rudder trim wheels, further back on the centre console, operated on the feel system beneath the stick and actually off-set the neutral positions of the controls. They were high-geared and very powerful. I would have liked to try getting near a stall, but in the hurly burly of checking, seat-changing, ATC and so on, I quite forgot to ask and no one suggested it. I do not know whether they woud have offered to demonstrate it. We were now ready to try a landing, and I was directed to let down to 4,000ft and beyond as we flew south down Puget Sound towards Seattle. Using the airbrakes, I let down slowly at moderate speed and levelled off finally at 2,500ft, on a downwind leg for Boeing Field which would turn our base leg directly over Seattle Tacoma ("Seatac") airport. This would turn a British controller's hair white, but we did it twice, with a ground clearance of 1,200ft and several light aircraft and airliners using the field below. At 200kt I began to extend the high-lift devices, and was told that VREF for the approach was 104kt and to fly finals at VREF +5kt. By the time I had 15° of flap I was flying at 160kt with about 70 per Concluded on page 1038
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