Vacuuming the Cockpit

By Leona Cobham, Surrey, UK

How does an airplane find its way? Modern aircraft use satellite navigation but what if the computer goes down? And what happened before satellites were invented?

Radio waves have long been an essential part of navigation. The system relies on ground beacons sending out signals that airplanes receive with an aerial. What if they are over sea and there are no beacons?

The answer: Inertial Navigation System. This on-board navigation device tracks all the movements of the aircraft from the moment it takes off and calculates exactly where the aircraft would be based on where it started. This is a useful back-up even for modern aircraft with satellite navigation.

And before Inertial Navigation was invented? Airplanes navigated using the same technique as ships; namely, observation of the stars. A hole in the cockpit ceiling allowed pilots to insert a sextant  — an instrument which determined the angle between the horizon and a star to determine longitude and latitude.

Sexton and map

Even today, some Boeing 747s still have the remnant port in the cockpit ceiling. One old pilot used to grumble about crumbs left by his First Officer after tea and biscuits had been served.

“Crumbs everywhere!” he bellowed. He suddenly stood up and, to the horror of the First Officer, he yanked the handle on the sextant port. The low pressure from the space outside the airplane sucked the crumbs out of the cockpit. With a woosh they flew into the night sky. He pulled the port closed. The Flight Engineer and First Officer stared at him dumbfounded. The old captain wore a satisfied smile as he looked through his side window at the night sky.

“And that is how you clean crumbs from the cockpit” he said quietly.

Leona Cobham is the author of Flying Circus Takes to the Skies

Visit her website at

Post Comments