How to safely accomplish a visual approach in a jet airliner
Join Date: Mar 2009
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Much of which has been written in the earlier posts holds true, the basics of making a visual approach remain the same regardless of the type of aircraft.
However another factor which applies to large jet aircraft and needs to be taken in consideration is the effect of inertia. Without a reference to a glide slope, either ILS or Vasis speed control and sink rate must be carefully monitored to maintain the aircraft on the desired profile to the runway. When things start to go wrong – either decaying airspeed, or increase in sink rate – on a heavy jet inertia ensures that they do so rather quickly, so small changes to thrust and or attitude are required early, rather than large changes late.
Another consideration on large jets is the aircraft landing geometry. With a considerable distance between the pilot and the rear undercarriage bogie - 100 feet on a Boeing 747 – and the pilot’s height of eye over the runway threshold, the touch down aiming point becomes a very important consideration. Being too low over the fence in a large jet can really spoil your day…
It is for these reasons that most airlines require at least one form of glide slope guidance for line operations and purely visual approaches are restricted to the simulator.
As someone who has spent many years training and checking pilots on large jets, I have seen more experienced pilots stuff up a “Simple” visual approach than more demanding exercises, like a multiple engine or control failure.
This is mostly due to a lack of practice, but also coupled with the considerations mentioned above.
However another factor which applies to large jet aircraft and needs to be taken in consideration is the effect of inertia. Without a reference to a glide slope, either ILS or Vasis speed control and sink rate must be carefully monitored to maintain the aircraft on the desired profile to the runway. When things start to go wrong – either decaying airspeed, or increase in sink rate – on a heavy jet inertia ensures that they do so rather quickly, so small changes to thrust and or attitude are required early, rather than large changes late.
Another consideration on large jets is the aircraft landing geometry. With a considerable distance between the pilot and the rear undercarriage bogie - 100 feet on a Boeing 747 – and the pilot’s height of eye over the runway threshold, the touch down aiming point becomes a very important consideration. Being too low over the fence in a large jet can really spoil your day…
It is for these reasons that most airlines require at least one form of glide slope guidance for line operations and purely visual approaches are restricted to the simulator.
As someone who has spent many years training and checking pilots on large jets, I have seen more experienced pilots stuff up a “Simple” visual approach than more demanding exercises, like a multiple engine or control failure.
This is mostly due to a lack of practice, but also coupled with the considerations mentioned above.
Last edited by Exaviator; 14th Sep 2013 at 05:04.
