Trivia Teaser: The men from the boys

Special crew qualifications were required to land using a rather infamous approach to the southeast into Hong Kong because of terrain and other problems. Because a straight-in approach towards this particular runway was not possible, an approach was made with which system?

A)            an ILS that is offset
B)            MLS
C)            an IGS
D)            ADF

It’s C. Hong Kong’s old Kai Tak was an airport with terrain problems; a straight-in approach towards the southeast not being possible because of mountains lying to the north. Instead, when landing on runway 13, an approach was made initially on a system similar to an ILS but offset at 47° to the runway, and referred to as an instrument guidance system (IGS). The IGS signals were rejected by the pilots at about 700 feet and the aircraft was flown towards a large red and white checker board before commencing a sharp 40° turn onto the runway at about 500 feet. The IGS had a paired DME with a built-in delay, which gave distance to the landing threshold, and on the ground strobe lights marked out the turn with offset PAPIs indicating glide path. (In Hong Kong, only aviation danger and guidance lights are permitted to flash. All commercial advertising lights must be steady). This approach, as well as the airport itself, were closed in July 1998. The History Channel program Most Extreme Airports ranked Kai Tak as the 6th most dangerous airport in the world. Hong Kong International Airport is now at Chek Lap Kok, replacing Kai Tak.