Ask Captain Lim

Dear Captain Lim,

I was just wondering what would happen if the reverse thrust system malfunctioned in mid air. Is it possible for 1 reverse thrust to come on during landing while the other does not? Would the wing be ripped off by the asymmetrical thrust?

Another question ? What are the procedures involved with taking off from John Wayne Airport in Santa Ana, California? What are the possible risks involved by requiring planes to perform special procedures during the take off?

Thanks and hope to hear from you.

Colin

Hi Colin,

There was indeed such an incident on an Austrian Lauda Air Boeing 767 in 1991. The flight took off from Bangkok International Airport for Vienna with 213 passengers and 10 crews. Whilst in flight, the left thrust reverser deployed and the plane stalled and finally disintegrated at 4000 feet.

All the 223 passengers and crew aboard did not survive the accident. It was the first fatal crash of a Boeing 767 and the only fatal 767 crash not attributed to human error.

A subsequent official investigation pinpointed the cause to a failure of the thrust reverser system. This led Boeing to modify the system to prevent similar occurrences in the future.

It is possible to have asymmetrical reverse thrust on landing due to one not working. It is not critical where directional control is concerned. I have experienced that many times on the Boeing 777 as well as on the Airbus A320. It would not rip off the wings!

The Brazilian Airbus A320 that crashed recently had only a serviceable left reverser as the right one was rendered inoperative before the flight. In that case, it appears that the pilot mishandled the landing technique (must selected both thrust levers to idle even if one is working!)

Noise abatement procedures are imposed on John Wayne Airport as it affects the local community staying directly south of the airport. Hence aircraft taking off towards the south must follow this special procedure or else they would ?ring the bells? of the 10 noise monitoring stations below their take off paths.

What is this special procedure all about? Well, for flights using the runway heading south (19R), pilots are required to take off at or near full power while holding at the runway, then release the brakes when the engines are fully spooled up. A steep climb is required to allow for a power reduction at about 500?700 feet from the ground level for a quieter flight over the city of Newport Beach. In addition, a left turn to 175 degrees allows the flight to satisfy the noise abatement limit.

This extra power during the takeoff enables the plane to climb higher at a faster rate than it normally would and getting farther away from the ground more quickly, thus reducing the noise for those who live near the airport.

This procedure does not involve any risks where flying is concerned - except that it may affect the wear and tear of the engines (reduced life cycle). Such a procedure is quite common in many city airports around the world.