In mid-January, a British Airways 777 landing at London’s Heathrow Airport crash-landed short of the runway.  When the jet was 600 feet above the ground (about 2 miles from the runway) the engines stopped responding – it effectively became a big glider. 

Most jets fly at about 150 mph during the landing phase.  In the scenario I described above, the pilots had less than 30 seconds identify the problem (the engines had stopped responding), have the cabin crew prepare the plane for an emergency and glide it towards the runway.  The plane touched down short of the runway and sustained major damage, but the most important thing is that nobody was seriously injured. The landing had more to it than just luck, and the pilots and the crew did a great job,

Gliding and Training 

Some people seem to think that when the airplane’s engines stop, the plane will drop out of the sky.  It is not well known is that all airplanes are designed to glide.  In fact, big jets are very efficient gliders; with a lot of altitude, a big jet can glide far.  I’ll talk about a few examples later in this article.

Pilots are trained to handle all sorts of emergencies when they first learn how to fly.  In fact, during my own private pilot training, my flight instructors taught me how to handle engine failures.  This was the most nerve-wracking emergency to practice because I had one chance to land safely.

Notable Airliner-Gliders 

In 2001 a Air Transat flight 236 was flying from Toronto, Canada to Lisbon, Portugal.  Somewhere across the Atlantic, the engines failed due to fuel starvation (the pilots did not notice there was a slow fuel leak due to a faulty part).  Starting at about 30,000 feet, the pilots managed to glide the airplane for about 20 minutes to a safe landing in the Azores.  Impressive! 

In 1982, a British Airways 747 flew into volcanic ash and all four engines failed.  The plane was at 37,000 feet and it was able to glide down to about 13,000 feet (about 12 minutes) before the crew restarted 3 of the engines and landed safely.

The Glide Ratio 

All airplanes come with a manual that is full of charts that help pilots predict an airplane’s performance during take-off, cruise, and landing.  There is also a section that indicates the airplane’s glide ratio.  A glide ratio indicates how many miles the airplane will glide over a given altitude loss.  For example, the small plane I fly, a Diamond Star, has glide ratio of 1.4 miles per 1000 feet of altitude lost.

 A 747 has a glide ratio of about 2.8 miles per 1000 feet of altitude lost at its best glide speed.  This means that a 747 cruising at around 35,000 feet can glide almost 100 miles if it loses engine power!

Modern airplanes are very reliable.  Several thousand aircraft are flying everyday without incident, which is a testament to the high standards of pilot training and maintenance.

Keep up the good work!

-Dr. Dave