Landings can be scary, but they’re no roller-coaster ride

Question: I have been on three flights that have made emergency landings that required diversions, assuming the “head down, stay down” position during the landing and having the runways foamed. I still fly out of necessity and manage OK except during the descent, which almost always involves lots of shaking and roller-coaster drops. It’s worse on smaller planes. Can you please tell me exactly what’s going on during the descent, and if it’s as dangerous as it seems?

— Elizabeth Koeninger, Sarasota, Fla.

Answer: It is not dangerous. Flying is the safest form of transportation ever created by mankind.

Unfortunately, your experiences have been a bit traumatic. It is very, very unusual for a passenger to have been in three landings where evacuation preparations were in effect. That is more than I have been involved in, in over 48 years of flying.

I appreciate your apprehension but please be assured that the descent is not a roller-coaster ride. Descending from cruise altitude can take many forms because of the requirements of air-traffic control. In some cases, it is necessary to descend quickly to meet crossing restrictions. Pilots practice this frequently, and airplanes are designed for it.

A smaller airplane may provide more sensation of rapidly descending, but they usually fly nearly the same profiles as larger ones. Q: At what distance from its destination does an airliner begin its descent? — Steve, Ohio

A: Normally an airliner will begin its descent around 100 to 120 miles from the destination (assuming the cruising altitude is above 30,000 feet).

Q: How long does it take from the start of descent to touchdown? And how many feet per second does the airplane descend? — Avi

A: It varies depending on traffic and the needs of air-traffic control. Modern airliners have flight-management computers that will begin a descent from 30,000 feet, approximately 100 miles from the destination planning an idle descent. The computer calculates a vertical path based on the approach and landing information programmed by the pilots.

Idle descent in many jets is around 3,000 feet a minute until reaching 10,000 feet. There is a speed restriction of 250 knots below 10,000 feet, therefore the flight-management computer will slow the aircraft to 250 knots and continue the descent at approximately 1,500 feet a minute.

Approximately 10 to 15 miles from the runway, the airplane is slowed to landing speed. Slats and flaps are extended passing 5 miles, at which point the airplane is at its approach speed on the lateral and vertical path to the runway.

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John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.