The glass-cockpit revolution has accelerated with the advent of reliable, long-lasting and high-resolution liquid-crystal displays (LCDs), but that revolution started when mechanical and electromechanical instruments were replaced with an earlier form of glass, the cathode-ray tube (CRT). Perhaps surprisingly, thousands of CRTs are still flying in airliners and business aircraft. However, CRTs aren’t nearly as long-lasting as LCDs, and they suffer from drawbacks that make them not as well suited to modern avionics display tasks. 

For many reasons, however, upgrading to LCDs—despite all the options—isn’t always a straightforward decision. Many older aircraft simply aren’t worth upgrading, yet they still have some value and must have working avionics. And that is where companies such as INAir, Millennium International, Thomas Electronics and Thomas Global Systems come in.

“The biggest part of our revenue is CRT-based display units, particularly the Honeywell systems,” said Roger Messick, president of INAir Legacy Avionics Solutions of Indianapolis, Ind. The display his company overhauls most is the Honeywell DU-870 CRT found in Primus 1000 and 2000 flight decks. “Honeywell is trying to convince operators to replace old DU-870 CRTs [with LCDs],” he said. “We’ve got a long-term commitment to repair that unit.” 

Messick estimates about 5,000 DU-870s are still in the field, with some business jets carrying three to six of the displays; each Embraer ERJ145 has five of the CRTs. “We’re getting a lot of traction in the business jet world and also on ERJ145s,” he said. “We have a pretty good base of business with the regional airlines.”

CRTs tend to last much longer in business jets than in airliners, according to Messick. “The lifetime on a CRT is longer on a business jet than a regional jet because they’re not turned on as frequently.” Many variables affect CRT life, making it hard to predict when they will fail.These factors include heat in the cockpit, brightness levels, how often they are being switched from one screen to the other and so on.

Long-term Supply

Japan’s Toshiba manufactures these CRTs and it still makes all the parts needed for repairs, according to Claude Peoples, vice president of sales and service for Millennium International, based in Lee’s Summit, Mo. “There are thousands of them out there, and there is no lack of parts to repair them,” he said. Millennium has commitments from Toshiba to supply CRT parts through 2025, for screens found in avionics systems by Honeywell, Rockwell Collins and Thales. 

Typical turn-time for a Honeywell DU-870 is one day, he said, and the cost of the repair is about 80 percent less than a new Honeywell LCD DU-875. Millennium CRT overhauls are warranted for two years.

INAir also provides a two-year warranty, and it also sources parts from Toshiba. Messick said that INAir plans to support CRTs through at least 2030, and he is assessing INAir’s needs and buying enough inventory to last that long. “We have a long-term supplier agreement with Toshiba,” he said, “but Toshiba is closing that factory in 2020.”

The overhaul typically requires replacement of the CRT display and the power supply—which is manufactured in the U.S.—and involves a detailed inspection of circuit boards and any necessary repairs. 

“What’s eventually going to happen,” said Messick, “and this will take another 10 to 12 years, is that these aircraft will be too old and cost-prohibitive to support. Our whole business is at the tail end of this market, the aging legacy aircraft. Our slice is the avionics piece. We’re there to service them, to keep them flying as cost-effectively as possible. This business has really improved because of the price of jet fuel. Newer aircraft are more fuel efficient, and when fuel costs too much there is a drive to park old airplanes. But when the cost of fuel comes down, they keep old aircraft longer. There are a lot of market factors that play into this.”