Expert: Ahmed Salami - 9/26/2004

Question
Hi. I have a math problem I am a little stuck on. Could you possibly help?

"Jack and Jill were flying cross country in their single-engine plane when their engine quit. When the engine died, the altimeter read 800 feet. They had just passed over a radio tower used as a marker on their navigation map. According to the map, 2 miles straight ahead was a small private airport. If the glide ratio of the plane is 18:1, will they be able to land safely at the airport?"

Any help will be highly appreciated. Thank you.

Answer
Hi Olga,
Glide ratio is an aviation term that refers to the distance an aircraft will move forward for any given amount of lost altitude (the cotangent of the downward angle). For instance, if an aircraft will move forward 5 feet for every foot of altitude lost, it has a glide ratio of 5:1.
So, as regards your question, the plane would move 18 feet for every foot of altitude lost. But because its already 800 feet above the ground, it would move a total distance of 18 x 800 feet forward in order to reach the ground(i.e to land) which is 14400 feet.
But 1 mile = 5280 feet
2 miles = 2(5280)= 10560 feet
So, the the aircraft can't land safely at the airport because on getting there, its still on air.
I hope you understand it.
Regards.