Mr. Chandler was first approached by the FAA on December 6th 2011, regarding some components for a wake turbulence timer. Numerous discussions followed for building a turnkey system but no deal was ever reached.
   
At the end of September 2013, Mr. Chandler delivered a purpose-built wake turbulence timer printed circuit board developed at his own time and expense. The printed circuit board was sized to fit an existing panel. This demonstrations version featured:
  • A piezo beeper to indicate when the countdown was complete
  • One Timer Channel
  • 2 or 3 minute countdown periods, selected by illuminated switches.
  • The ability to toggle between 2 and 3 minute periods during a countdown in the event that the wrong interval was selected. 
  • Canceling a countdown progress by pressing both buttons simultaneously. 
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The champion of the Wake Turbulence Timer Project, Mr. Clark Eastman (NAVAIDS/Communications - Washington, Technical Operations AJW-W22E)
took note of this demo unit and serious discussions began about the 
development of the wake turbulence timers.

Mr. Eastman proposed a "brain replacement" for the existing (and problematic) dual-timer AWTT3 wake turbulence timer on October 30th 2013, and offered minuscule compensation to build a working prototype, which was delivered three months later. The functionality of this prototype was limited by the desire to use the existing non-illuminated swithces

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Air Traffic Control evaluated the single channel timer version to the "re-brained" AWTT3. The conclusion was they wanted all the features of the single channel version in a two channel version. the upgraded AWWT3 was deemed unacceptable because of limitations imposed by using the existing hardware.

Two new dual timer wake turbulence timers were desired, a horizontal format in a size factor of the AWTT3 and a vertical format of approximately similar size to fit in place of another style of existing timers. 

Prime in Mr. Chandlers' mind were the following factors:
  • The timers had to be extremely reliable with a long service life. 
  • The dual timers needed to be arranged in a way to provide easy differentiation between the sections. The controllers needed to know at a glance which timer section was in use for a particular area. 
  • The timers required field-replaceable switches. Even with an expected service life of 2 million cylces, switches could fail for a number reasons. A failed switch should not place the timer out of service for an extended period of time. 
To differentiate the sections on the horizontal units, a side-by-side design, rather then the top/bottom design of the AWTT3 timer. To further differentiated the timer sections, one of the sections has a red display and buttons, while the the other section has a yellow display and buttons. Red and green color coding was avoided to prevent any association with port and starboard. 



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Reliable operation was ensured in part of avoiding soldered pigtails on the switches. A pigtail takes a long time to assemble properly and is subject to error and failures. Instead, pre-manufactured jumper cables and switch sockets on remote printed circuit boards were used. This also facilitated easy field-replacement of switches without soldering if needed in the future. 

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The original ten units were supplied as assembled and tested printed circuit boards, to be married to panels manufactured by the FAA Staging Area in  Independence, MO. 
    
Hardware for the second group of timers purchased was improved by using a two-board stack, one with the LED displays and drive, the other with the micro-control and switch sockets mounted directly to the circuit board with no jumpers being required. This change resulted in easier assembly, enhanced reliability and easier field repairs. The second group of timers purchased also feature acrylic panels, as having the panels built by the staging area and the final assembly done there proved problematic. 

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In January 2016, after the timers had been in service for approximately a year, operational feedback from the controllers who had used the timers was sought. Slight enhancements to the firmware were made to suit the controllers' operation style. 


Additional information about the development of the Wake Turbulence Timers may be found in the following forum posts and articles:

Forum Posts

TOPIC: A Long-Term Project.... - An overview of the start of  the project and some of the design decisions along the way.


TOPIC: Dyeing Polycarbonate Display Bezel Lenses - The original timers used lens in bezels.  The manufacturer did not offer a yellow lenses as a standard item, but was happy to do so, for an order of 2000 lenses.  An optometrist provided a simple solution, if boiling polycarbonate lenses in dye can be called simple.


TOPIC: How to choose PCBA service? - As the possibility of a large order of timers looms ahead, a Chinese assembly service was tried for a small batch of timer circuit boards.  There were a few bumps along the way, but the results were excellent.


TOPIC: Some Lessons Learned from my FAA Project - Small problems crop up from time to time.



Articles

Laser Cutting and Engraving May Be Closer Than You Think - Aluminum panels supplied by the FAA Staging Area didn't work out; laser-cut acrylic panels were a reliable, low-cost solution in small volumes.  A laser-cutting service may be available just down the street.


Acrylic Materials For Panels - A discussion of various types of acrylic materials for electronics panels.


Piezo Beeper Volume Control - Sometimes Projects Aren't Easy - The smallest parts of a project can sometimes provide the greatest challenges.