Panels of the past: after nearly 80 years of keeping the dirty side down using round gauges, the age of attitude-instrument flying may be on its way out.
Before we say goodbye to round instruments forever, how about a little cross-country journey along the last 79 years of instrument flight since Jimmy Doolittle made the first blind flight in 1929?
Life Was Black and White
Elmer Sperry developed gyroscopic instruments. Doolittle put a hood over the cockpit and flew them. Until the advent of EFIS, the fundamentals of gyroscopic instruments and the information they provide to the pilot had changed little.
An early artificial horizon looked just like a modern version, but it was bigger and all black, except for the radium paint that glowed in the dark to illuminate the horizon bar and the bank markings.
The directional gyros of the day worked the same, but the display was different. The heading numbers were painted, again with radium paint, on a barrel that the gyros held stationary. As the airplane turned, it rotated around the barrel. This seemed logical because it looked like the magnetic compass. But it required turning opposite where the new heading appeared on the instrument. It also created a secondary problem during an engine failure in a multi-engine airplane, where the presentation could confuse the pilot as to which engine had failed.
While gyros evolved little, navigation equipment changed dramatically. Dead reckoning meant flying headings for specific times to estimate your position over the earth. That was fine in the clouds over flat-lands, but a poor choice where terrain posed a hazard.
Flying the Beams
The first radio navigation was the four-course range. There are still a few flyers in the cockpit who can remember flying in the clouds listening for the Morse code of "A," dit dah, or "N," dah dit. Flying on the course combined the codes to make a steady tone. There was a "cone of silence" over the transmitter that marked station crossing.
If you ever wondered why many VOR stations are three to five miles from the airport, it's because they replaced a four-course range on the same spot. The range was the final approach fix and one leg of the station pointed to the airport.
The first improvement on the four-course range was a loop antenna. By manually rotating a big loop on the roof of the airplane, pilots could point at the station. Automating this process led to the ADF. Wide spread adoption of ADF receivers, and the development of VHF VOR navigation in the '50s, spelled the welcome end of the A/N aural navigation.
The first GA VOR receivers were nav-coms. They had names like "whistle stop" and "coffee grinder." The same receiver was used for navigation and voice. Transmitting was limited to a few frequencies, depending on how many crystals were installed in the unit. Hearing the Morse code ID of the station was imperative to preclude navigating to the wrong station.
The VOR is still with us today, but one adaptation of the CDI that has been lost was another Sperry device called a Zero-Reader. It was a wonderful replacement for the CDI with two needles instead of one. The big needle hung from the top of the instrument and displayed the course-line, just like a modern CDI. A second, shorter needle came up from the bottom with a bulls-eye on the end of it. This needle showed the trend, whether the airplane was converging on, or diverging from, the course. Turning the airplane toward the course line needle until the bulls-eye centered over the course line needle yielded the appropriate intercept angle and roll-out on to the course. Once established on the course line, any change in heading moved the bulls-eye off center, and an immediate heading correction kept the course line centered easily. It was really a horizontal flight director, and a predecessor to the HSI.
The HSI was the first attempt at what would later become a moving map. It gave us a God's-eye view of our situation with regard to the course on the ground. Simultaneously, the Zero-Reader expanded into the vertical dimension and the cross-hair flight director was born. The flight director provided the same kind of useful information for vertical guidance as well as horizontal guidance needed to fly the new class of high-performance, swept-wing jets.
All this technology was coming to the corporate and airline world in the late '50s and early '60s, but brand-new GA airplanes, including light twins, were still leaving the factory with military surplus gyros from World War II. Instrument flying was still the exception rather than the rule in light aircraft.
In the mid '60s, three-inch gyros were developed and new airplanes started shipping with new gyro instruments, but even then, they were scattered inconsistently across the panel. Transistors were replacing vacuum tubes and the weight and power consumption of radios became more compatible with light airplanes. Narco introduced the Mark 12, a full-blown nav-com with channeled tuning for both the transmitter and receiver for the GA market.
In the early '70s, the six-pack became the standard and pilots could develop an instrument scan that made sense. Organized instruments, coupled with dependable, solid-state radios and an autopilot that worked, started to make instrument flying in GA airplanes more practical and prevalent.
Autopilots were also almost unheard of in little airplanes until the advent of solid-state electronics, due to cost and weight. The Century I, II, and III autopilots were the first practical solutions for the GA market. King developed the KFC series of flight director/autopilots for GA airplanes in the '70s as well, and single-cue flight directors previously reserved for the turbine world became common in GA airplanes.
The Age of RNAV
LORAN had been used for marine navigation, but it took small computers, memory and displays from the space program for LORAN to work for GA. They had crude databases and provided bearing, range, course, track and speed to any point in the database. The FAA promised IFR certification and approach modes, but few installations were ever approved.
GPS appeared in the late '80s and it changed the game. The '90s was the decade of the moving map. The first decade of the 21st century brought us downlink weather and traffic in light airplanes. This decade is also the beginning of synthetic vision as a widespread option for light airplanes. This not only means the end of the steam gauge, but probably also the end of the horizon instrument display that Sperry pioneered almost 80 years ago.
Imagine taking Jimmy Doolittle and Elmer Sperry for a ride in a four-seat, personal GA airplane with synthetic vision, downlink weather, onboard traffic and a three-axis autopilot that will fly the airplane to the fixed-distance markers within 10 feet of the centerline with navigation based on satellites orbiting hundreds of miles overhead.
Then imagine what the panel of our personal airplanes will look like 80 years from now.
Doug Rozendaal flies antiques, the latest jets and a bunch o' stuff in between.
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|Title Annotation:||IFR DIARY|
|Date:||Oct 1, 2008|
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