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Jet Aircraft Handling During Approach & Landing

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Jet Aircraft Handling During Approach & Landing

Old 27th May 2010, 14:36
  #21 (permalink)  
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Join Date: Jun 2005
Location: USA
Posts: 176

Thank you for your feedbacks.

ok, after we all agree that great pilots never fail and the question therefore is obsolete......
The flight Safety Foundation Approache and Landing Accident Reduction (ALAR)Task Force found that unstabilized approaches (i.e., approaches conducted either low/slow or high/fast) were a causal factor in 66% of 76 approach and landing accidents and serious incidents worldwide in 1984 through 1997

The task force said that although some low-energy approaches (i.e., low/slow) resulted in loss of aircraft control, most involved CFIT because of inadequate vertical-position awareness.
The task force said that the high-energy approaches (i.e., high/fast) resulted in loss of aircraft control, runway overruns and runway excursions, and contributed to inadequate situational awareness in some CFIT accidents.
The task force also found that flight-handling difficulties (i.e., the crew’s inability to control the aircraft to the desired flight parameters [e.g., airspeed, altitude, rate of descent]) were a causal factor in 45% of 76 approach and landing accidents and serious incidents.

The Task Force said that flight-handling difficulties occured in situations that includes rushing approaches, attempts to comply with demanding ATC clearance, adverse wind condition and improper use of automation.
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Old 28th May 2010, 00:47
  #22 (permalink)  
Join Date: Dec 2005
Location: Oz
Posts: 52

What I believe other contributors are trying to say is that landing a Jet aircraft is not 'hard' providing you have been trained correctly, are a professional aviator (unlike some on their forum who seem to believe that a G/A should never be necessary) and are prepared and thinking ahead of the aircraft.

In response to your question though, flying a jet aircraft on approach does present a unique set of challenges. The list and intimate detail is far too exhaustive to discuss in full on this forum, however there is some excellent material published on it including 'Handling the big Jets' by J.P Davies. I have outlined a few points below.

Turbine vs Piston engine response: A piston engine aircraft has an almost instantaneous response to throttle adjustments, this is not true in jet powered aircraft. In Jets particularly at lower power settings it can take a significant time to 'spool up' This is why Jet aircraft operators require the aircraft to be under a stabilised thrust setting by a particular stage of the approach. Modern jet engine response time is however much faster than the engines of the past.

Jet Aircraft vs Prop aircraft: To make matters worse, when getting slow in a prop aircraft advancing the throttle immediately provides an increase in thrust and a very beneficial increase in propellor slip stream increasing lift over the wing, this is not true in Jets. Also, at idle throttle in a prop aircraft the prop generates a heap of drag allowing the aircraft to slow down very quickly (this includes turbo-props), in Jets at flight-idle the engines are still producing some residual forward thrust, this can make the aircraft very hard to slow down if the descent is not properly planned or the pilot allows ATC to subvert his/her plan.

Wing design: Modern jet aircraft Laminar flow and supercritical wings have a flatter Drag curve than traditional light aircraft. This has two effects. Firstly, the speed for minimum drag is higher (approx. 1.4 Vs1g according to JP Davies for a typical wing if memory serves me correctly, as opposed to 1.3vs in light aircraft). Going below this speed puts the aircraft on the back of the drag curve or 'speed unstable region'. Secondly, it is possible to miss this speed unstable event on a modern transport category wing, thereby allowing the situation to become worse (whereas in a light aircraft it is VERY noticeable), couple this with slow spool up times and no prop slip stream and it is easy to see why when flying a jet and getting slow it is extremely important to be positive with the thrust levers. Further study on wing design would encounter the subject of supercritical wings and the associated handling pitfalls with a low wing loading.

In summary, whilst not difficult, there are unique challenges to flying a jet transport cat aircraft. If the descent is not appropriately planned and managed or you encounter/allow something grossly outside of the plan (increased t/w, change of rwy, less track miles) it is necessary to immediately adjust the profile (speed control / track miles / speed brakes / config) If the adjustment required is too large and too late a G/A may be the safest/required option (Jet operators have strict stable approach criteria), doesn't happen often but does happen.

Sorry about the rushed reply but hope this answers some of your question. Highly recommend getting your hands on JP Davies book.

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