747's Electrifying Breakthrough

By Floyd Lukecart

May 2016

Many of the flight instruments such as the airspeed, altimeter and rate-of-climb on the first 747s were basically huff-n-puff type, i.e., they were pitot (pressure) and static (vacuum) instruments connected to the pitot probes mounted outside near the front of the airplane by aluminum tubing.

The Air Data Computer was analog and also connected to the pitot-static tubing. The Air Data Computer supplied analog signals to other systems on the airplane such as the Automatic Pilot and Navigation systems. Eventually the analog Air Data Computer was replaced with a digital Air Data Computer, but it still required a pitot-static connection.

One of the highlights of working as an avionics system engineer and lead engineer for the Air Data System on the 747, 757 and 767 was to develop an electric airspeed indicator for the 747, thus eliminating the pitot tubing normally connected to the two airspeed indicators, consequently reducing weight.

After the airspeed indicator development completion, the next hurdle was to convince the Federal Aviation Administration that the electric airspeed indicators were as safe as, or safer than, the pitot-driven airspeed indicators. After submitting safety data and other papers to the FAA, the airspeed indication system was approved, and until the 747 went with digital all-glass flight instruments, the two airspeed indicators were electric.

Another first on the 747 was to develop glass flight instruments for Air Force One, a 747-200. This was prior to the production 747 development of all-glass flight instruments. As the lead engineer on this project, with three Boeing engineers, two vendor engineers, plus a Boeing staff engineer, the work meant lots of overtime hours were to be spent -- but in the end, the job was accomplished.

This was the project that eliminated my bridge game during the lunch hour.