The airplane was now so far out of trim that Getachew had to hold his control column halfway back (meaning half up-elevator) to keep the nose from dropping.
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This is another of Boeing's bewildering failures — the implementation of an automated nose-down input meant to make for an authentic control feel but allowed to keep at it again and again while throwing the airplane wildly out of trim.
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The record shows four attempts in rapid succession to engage the autopilot, all of which were refused because autopilots are not recovery devices and will not engage if they sense pressures on the control column — meaning that an airplane is being flown out of trim.
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Crossing over the channel, his port engine went in and out of trim. He struggled to keep the aircraft aloft. Reaching England, he asked if his crew would want to take to the chutes, but they all elected to stay with the aircraft. Pelly did a wheels up landing on a field, and everyone was able to get out alive.
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However, Brown criticised the lack of trim controls. If a member of the ground crew had moved the tab, or it had been adjusted from another source, it could result in an out-of-trim flight performance at high speeds. Brown praised the high rate of roll. Aileron response was excellent from stall up until 400 mph (644 km/h), when they became heavy.
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Axes of a ship and rotations around them There are three special axes in any ship, called longitudinal, transverse and vertical axes. The movements around them are known as roll, pitch, and yaw respectively. ; Pitch: The up/down rotation of a vessel about its transverse/Y (side-to-side or port-starboard) axis. An offset or deviation from normal on this axis is referred to as trim or out of trim.
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Eckener concluded that the puncture hypothesis, due to pilot error, was the most likely explanation for the disaster. He held Captains Pruss and Lehmann, and Charles Rosendahl responsible for what he viewed as a rushed landing procedure with the airship badly out of trim under poor weather conditions. Pruss had made the sharp turn under Lehmann's pressure; while Rosendahl called the airship in for landing, believing the conditions were suitable. Eckener noted that a smaller storm front followed the thunderstorm front, creating conditions suitable for static sparks.
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There had been earlier "out-of-trim incidents" with the Airbus A300-600R. Airbus had the company that made the flight control computer produce a modification to the air flight system that would disengage the autopilot "when certain manual controls input is applied on the control wheel in GO-AROUND mode". This modification was first available in September 1993, and the aircraft that had crashed had been scheduled to receive the upgrade. The aircraft had not received the update at the time of the crash because "China Airlines judged that the modifications were not urgent".
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It was also found that the pumps could not be disconnected and they ran constantly, resulting in great wear on the valve stems. They were also situated in the stern of the ship, rendering them useless when out of trim forward as Xantho was on her final voyage. The boiler relief valve was an outdated gravity variety and not the spring type generally used at sea to avoid problems as the vessel pitched and rolled. There was no condenser for recycling the used steam back into the boiler.
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Soon afterwards, as it approached the ILS glideslope beam, its height and speed were reduced further and the undercarriage was extended. Then the Captain saw a light which he mistook for one at the far end of the runway—it was actually on a hill beyond the airport—and the "stabiliser out of trim" warning light came on. This had been faulty earlier in the flight, and the Captain disengaged the autopilot and the automatic glideslope tracker. At 0133, the flap angle was increased; the aircraft then began to fall below the approach slope and was travelling faster than the crew thought.
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The resolution for this jammed trim issue is not part of Boeing's current 737 manual according to The Air Current. The Seattle Times reports pilots on the 737-200 were trained for this failure, but later models became so reliable that this procedure was no longer necessary. Experts theorize that the difficulty to trim made it necessary for the flight crew to release the cutout, and try to use electronic trim in an effort to correct the out-of-trim configuration. According to Bjorn Fehrm (Leeham News) and Peter Lemme at this time the airplane was flying "at 375kts and MCAS was never designed to trim at these Speed/Altitude combinations".
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The net effect is that one wing is stalled before the other and the aircraft descends rapidly while rotating, and some aircraft cannot recover from this condition without correct pilot control inputs (which must stop yaw) and loading.14 CFR part 23 A new solution to the problem of difficult (or impossible) stall-spin recovery is provided by the ballistic parachute recovery system. The most common stall-spin scenarios occur on takeoff (departure stall) and during landing (base to final turn) because of insufficient airspeed during these maneuvers. Stalls also occur during a go- around manoeuvre if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed.
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At low air speeds, of or less, the increase in lift obtained by the use of planes on an airship would require a disproportionate increase in engine power and fuel consumption compared to increasing the size of the gas bags. Moreover, the attachment of flying surfaces to the airship's envelope would require significant structural strengthening, with attendant weight gain. Conventional airships often make use of aerodynamic lift by using their elevators to set a nose-up attitude so that the main body of the airship provides some lift as it flies along; however, this is typically done to counteract minor out-of-trim conditions, and it is as likely that the nose may need to be pointed down to reduce lift. Some Hybrid designs, such as the Lockheed Martin LMZ1M, use a flattened or multi-lobed hull to increase the aerodynamic lift obtainable.
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Castoldi based the design of the M.67, (a single-seat, low-wing, monoplane, twin-float floatplane), on that of the earlier Macchi M.39, which had competed for Italy in the 1926 and 1927 Schneider Trophy races, following the M.39s layout but strengthened to accommodate the 18-cylinder, , Isotta- Fraschini Asso 1000("Ace") 1000 W-18 engine, a much bigger and more powerful engine than the Fiat AS.2 V12 fitted to the M.39. The M.67 carried fuel in its floats; the powerful engine drove a three-bladed propeller which created a large amount of torque. To provide extra flotation allowing smaller floats, lighter structure and less drag, fuel was carried in integral tanks built into the floats. To counter the high torque from the propeller, more fuel was carried in one float than the other, reducing swing on take-off dramatically due to reduced asymmetric hydro-dynamic drag, but also causing high out of trim forces in roll when airborne.
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