what controls a planes decent on approach to landing
Information technology is still far also early on in the investigation into the blow involving Asiana flight 214 at San Francisco drome to draw any conclusions about the events leading upwards to the blow. However, some may exist wondering to what extent the information released so far by the US investigation agency, the NTSB, corresponds to a "typical" landing.
Descent
A modern airliner such every bit a Boeing 777 volition start descending from its cruising distance (for example, 37,000ft) and slowing from its cruising speed (for example, 470kt true airspeed) when information technology is around 100 miles from the airport.
The goal is to gradually reduce height and speed and then that the shipping arrives at the runway at a safe speed (typically around 135kt) for the landing. Air traffic command directs the shipping towards the airport by issuing a series of instructions to change heading (management of flight), height and speed until the shipping can brainstorm its approach to the runway.
Guided arroyo
The approach method depends on a number of factors including the conditions, the shipping type and the airport equipment available. Most all major airports are equipped with systems that provide pilots with management and descent profile guidance to the runway. These systems tin let the aircraft to land safely and automatically when visibility is poor and the pilots cannot run into the runway, but they are also unremarkably used even when the weather is skillful to provide additional guidance to pilots flying approaches manually.
The arroyo guidance, known as the Instrument Landing Arrangement (ILS, gives both lateral position relative to the track and also indicates whether the aircraft is on, above or below the platonic glide slope - the angle at which the plane descends.
A typical arroyo would follow a three degree glide slope. The approach would and then descend on that glide slope, gradually dissipating speed to arrive at the target approach speed which is based on, amongst other things, the aircraft blazon and configuration.
As the speed decreases, the pilots volition change the aircraft configuration by deploying flaps and slats. These are aerodynamic devices on the front (slats) and the rear (flaps) of the wings that you see extending during landing. They are designed to generate more elevator, which allows the shipping to land at slower and safer speeds.
Visual approach
A visual approach may make use of the Precision Approach Path Indicator (PAPI) lights. These are 4 lights which prove a combination of white and red to indicate whether the aircraft is on, above or below the ideal glide slope.
Normally during a visual approach, ane airplane pilot would exist flying the aircraft while the other monitors the aircraft's speed, top and systems to ensure the aircraft is properly set up for the landing. Visual approaches are flown manually, but information technology's quite usual in modern airliners to go on the autothrust (or autothrottle) system engaged to assist keep the shipping at the correct speed.
The aim of an arroyo is to become stabilised, that is, closely following the ideal glide slope with speed properly controlled and the aircraft correctly configured. If at any point during the approach or landing either airplane pilot considers that it is not safe to continue (such as poor positioning, an occupied rail or unstable approach), they will call for a go-around. The crew will and so employ total power and climb away from the aerodrome on a prescribed path to either set some other approach or divert to another airport.
Landing
With the aircraft stable and correctly positioned, the arroyo phase can transition to the landing. As the aircraft arrives over the track threshold, automatic callouts tell the pilots the top to a higher place the runway. At around 20ft the pilot will close the throttles and commencement to flare (elevator the nose of the aircraft) allowing the main landing gear to bear on downwardly, followed by touching downwards the nose gear.
The shipping should touch down close to the aiming indicate (painted on the rails) with a low rate of descent. They volition then apply brakes (or employ automatic braking), and peradventure opposite thrust, before turning off the runway onto a taxiway and taxiing to the last.
Asiana 214
The Asiana crash is the third hull loss of a Boeing 777 following a footing burn of an EgyptAir shipping in Cairo and the blow to British Airways Flight 38 which crashed short of track 27L at London Heathrow in 2008.
In the instance of the Asiana blow, the NTSB has released a significant amount of initial data very early in the investigation. This is unusual and, while it tin satisfy media interest, "drip-feeding" data this style can lead to facts losing their context and create misperceptions about what actually happened.
The NTSB has reported that at the time of the accident the visibility was very good (>ten miles) with depression wind speeds (around 7kt). According to the US regulator, the FAA, the ILS glide gradient system was unavailable at San Francisco drome between 1 June and 22 Baronial, which would preclude a full instrument approach. This lack of availability was publicised as a Find to Airmen (NOTAM), which is the usual way of notifying crews of this type of data.
The NTSB conference stated that a visual approach clearance was issued for Asiana 214 and the crew were reported to be using the PAPI lights. The briefings suggest that the Asiana pilots disengaged the autopilot at around 1600ft and flew the arroyo manually, but at this stage information technology is non clear whether the autothrottle remained engaged throughout the rest of the approach or whether the pilots were controlling the speed manually.
Using information from the Flight Information Recorder and the Cockpit Voice Recorder the NTSB reported that the ideal approach speed was identified as 137kt and that the lowest speed reach during the approach was 103kt. They take also reported that the low speed was noticed by the pilots seven seconds before impact, that the "stick shaker" (a device giving auditory and tactile feedback) activated iv seconds earlier impact and that a get-around was called a 2nd and a one-half earlier affect.
Understanding what happened in the run-upward to an accident is only the start of the investigation. It'southward more of import to sympathise why it happened and, the ultimate aim of accident investigation, to cease information technology happening again.
Source: https://theconversation.com/explainer-how-to-land-a-plane-16014
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