Sandel Avionics SN3308 Electronic HSI Supplement:
Gerry Block Talks About Sandel Avionics

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As a supplement to his review of the SN3308, AVweb editor Mike Busch interviews its creator (and the founder of Sandel Avionics) Gerry Block.

ProductsAfter seeing the SN3308, I naturally assumed that its inventor and Sandel founder Gerry Block was a seasoned veteran of the avionics industry. So when I flew down to Sandel Avionics in a northern suburb of San Diego to interview him for this article, I was quite surprised to learn that the SN3308 was Block's very first aviation product. Turns out that Gerry's previous career was as owner of a company that manufactured audio broadcast equipment used in motion picture and television production. Block sold his company in 1995 and soon started thinking about starting a new career that combined his background in electronics with his love of aviation.

Sandel Avionics

Gerry Block
Gerry Block is founder and president of Sandel Avionics, and the inventor of the SN3308 EHSI.

Gerry had been a pilot for many years, and his audio equipment company owned a Cessna 421 with a very sophisticated Collins FD-112 flight control system. For the longest time, Gerry wanted to put an EFIS system in that airplane. But the only thing available that was even remotely practical was the Bendix/King EFIS 40 system. Gerry looked into that possibility quite seriously, but found that he couldn't put an EFIS 40 in the airplane without literally ripping out the entire panel and starting over, at a cost of around $50,000 by the time labor and ancillary equipment were included. That was simply too much.

In early 1996, after his audio equipment company was sold, Gerry started seriously looking into the notion of creating an EFIS of a size and price within the reach of piston aircraft owners. He quickly discovered there were a tremendous number of technical hurdles involved. The most significant of these was that in order to make a three-inch indicator practical, it had to be virtually 100% screen area. Standard CRT or LCD displays wouldn't work: The best they could do in a three-inch opening would be about 21/4 inches square of actual display area, which simply doesn't provide adequate size or resolution for a primary flight instrument.

Grimes (now AlliedSignal) and BFGoodrich had both developed such flat-panel displays for use as backup instruments, and Honeywell makes one they use for TCAS. But all are extremely expensive, and none provide adequate area or resolution for a primary flight instrument. If you tried to use one as an electronic HSI, you'd wind up with a compass rose significantly smaller than the one on a three-inch mechanical HSI, which is already a bit too small for comfort. Another problem was that standard mass-produced LCD displays are typically rectangular rather than square, and having a square one custom-built for a low-volume application like avionics would increase the cost of the instrument to impractical levels.

Gerry then came up with the concept of using a small LCD and rear-projection optics to create a display that could occupy virtually the entire height and width of the instrument. This was a brand-new approach, never used before, and on which Sandel has applied for a patent.

Mike Busch and Gerry Block
Mike Busch examines the innermost workings of the Sandel SN3308 as inventor Gerry Block explains to him how it works.

This idea made the SN3308 feasible, but there were still many technical hurdles to overcome. Product development would require substantial talent in numerous disciplines: software engineering, hardware engineering, graphics, analog interfaces, optics, packaging, and FAA certification. From his previous company, Gerry had lots of experience in both hardware and software engineering of embedded processor products and analog interfaces. But, he did not have the requisite background in graphics, optics, packaging, and especially FAA certification. So, he hired several very smart consulting engineers to work with him. He also worked with some consulting DERs (FAA-Designated Engineering Representatives) to develop the application for certification. But even at its peak, only a half-dozen people were involved in the development and certification effort. Gerry managed the project personally, and wrote all the software for the instrument himself.

It took about a year to develop the first real working prototype of the SN3308, which was shown at both NBAA and AOPA Expo in October 1997. The prototype was "quite crude" according to Gerry, but it generated a lot of interest and useful feedback that contributed to the final design of the product. The first production units were shipped in July 1998.

I asked Gerry what he had to go through to get the SN3308 FAA-certified. He admitted that the certification process took longer than he expected, both because the SN3308 was so novel and because this was Sandel's first certification effort so the FAA really held its feet to the fire. Gerry says the FAA certification folks were both very demanding and very fair. "They didn't make us jump through any hoop that wasn't reasonable," he added. Gerry explained that the FAA certification people provided a great deal of constructive input to the design, and made Sandel redo some things they didn't like in the prototype, but the result was a much-improved instrument. Sandel worked on SN3308 certification primarily with the Los Angeles Aircraft Certification Office (ACO) and Manufacturer Inspection District Office (MIDO). Gerry refers to the FAA folks he worked with as "a great group of guys."

Hearing Gerry talk about the certification of the SN3308 was refreshing. So many aviation entrepreneurs complain endlessly about the time, cost and hassle of FAA certification. But to Gerry Block, certification was just one more challenge, and the man genuinely seems to love challenges.

Editor's Note:

Don't miss Mike Busch's in-depth review of the SN3308!