Ask Captain Lim

Hi Captain Lim,

Your website provides an awesome load of information. One can even fly a plane from browsing through it! Its a great pleasure to have come across this fantastic website!

I've some questions pertaining to aircraft landing:

What affects the approach during the landing? Why do pilot sometimes steer the aircraft with a very steep turn during the final stage of the landing? Is it due to the weather condition or the nature in which the airport is designed (e.g. Hong Kong Kai Tak International Airport)

How do pilots ensure that they land accurately on the runway in these difficult turns? Is it common for pilot to conduct last minute changes to correct the heading to line up with the runway during that sort of landing?

How would it affect the pilot if he/she commits an error in such landing, resulting in an engine strike?

What is the use of a checkerboard erected near the runway?

Happy Flying!!!

Sammy Peh

Hi Sam,

What makes a pilot's day is a calm and clear day. Things become bad when the weather deteriorates and the crosswind becomes stronger. Yes, many other factors can affect the approach to a safe landing. Amongst others, the nasty crosswind is one of them - that is the day when a pilot encountering one really sweats!

On the Boeing 777, any crosswind above 45 knots is a no no! For take off, the limitation is even less - 40 knots. This reminds me of my previous Shanghai flight when I had to delay my flight for 24 hours due to the approaching typhoon that was causing a gusty 46 knots crosswind. See this posting "Do air crashes come in a row?" under the Air Crash Menu.

When an aircraft has to do a steep turn in the final stage of the landing, it is often not due to cross wind. A crosswind makes the aircraft "crabs' towards the runway. Such steep turns are either caused by some radar controllers bad positioning of the plane during the interception of the ILS (Instrument Landing System) approach; the pilot misjudging his turn due to strong crosswinds or it was a checker-board type approach in the Hong Kong's old Kai Tak airport. In such cases, the pilot makes use of the ILS or look out visually to maneuver the plane to the runway centerline again.

A well-planned turn is normally smooth and gentle so that the pilot need not have to make any last minute corrections of heading to line up with the centerline. Even if corrections are made, the plane must be stabilized by 500 feet above ground level on a clear day. If not, he must make a mandatory go-around or abort the landing.

An error of judgment resulting in a tail or engine strike can lead to disciplinary action against a pilot.

Checkerboard markers are used to indicate obstacles on the final approach to land. Hong Kong*s old Kai Tak airport had one of the most famous checkerboards on one of its runway. Yes, the new Chap Lap Kok Airport has got rid of one of the most challenging runway to land today!