Learjet Fall 2005

• 20/30/50 Strobe Lights
• Learjet 31/35/36 DEEC Upgrade
• Want Graphical Weather?
• High Speed Data Systems

20/30/50 Strobe Lights

— Dave Schiver

Strobe lights seem to be over-analyzed in troubleshooting. The first question should be, is one not working or are all of them not working? If all are not working, then it usually is a problem of aircraft power getting to the power supply base. (There are four pieces that make up a power supply assembly; three power supplies and a timer base). If there is power and ground, the base is bad. It is possible to have three bad power supplies or bulbs, but highly unlikely. A typical squawk is one where the bulb is not firing. I like to swap plugs on the power supply first. For example, if the tail strobe light is inoperable, swap P323 and P320 (30 series plug numbers). If the R/H wing stops working and the tail starts working, it is a power supply. At that point, swap power supplies on the base to verify that it is not a base.

Let’s say that it did not follow the plug swap. Then I ring out the wires to verify that there is continuity, and more importantly, no shorts to ground or each other. This is fairly common from the wire being pinched or bent. If that is OK, then I’ll just replace the bulb.

Now for repairing the twisted shielded pair for the strobe lights. Yes, per chapter 20 you can repair it. I would highly advise against that. There is a lot of noise in those lines and you could induce other problems. I always recommend replacing the wires when possible. There is also a discrepancy in the 31 wiring manual on 33-40-04. The plug numbers for the tail strobe is shown as P383 connecting to J937. It should read J383 on the power supply side and P383 on the bulb side.

If you have additional questions about this topic or any Learjet technical issue, contact me at 800.228.4277 ext. 1680.

Learjet 31/35/36 DEEC Upgrade

— Lanny Renshaw

Re: Honeywell Service Bulletin (SB) 76- 3076R1, rework N1 DEEC to P/N 2119010-3004 or 2119010-4004 addressing lean blowout (LBO).

There have been incidents in which 731-2 engines equipped with ECTM N1 DEEC on Learjet aircraft have experience LBO during descent, when the throttle was rapidly reduced to idle. This SB will enhance the LBO margins, minimizing the potential for LBO. This upgrade also incorporates SB76-3068 that minimizes the possibility of an uncommanded acceleration in “auto mode.” Honeywell recommends that this SB be complied with in 150 engine operating hours or six months, whichever occurs first. Duncan Aviation and other authorized service centers (line maintenance level or greater) are qualified to accomplish this software download.

Want Graphical Weather?

— Joe Spring

If you have a Universal MFD-640, you can now get WSI or XM Graphical Weather. Contact Joe Spring for more information, 800.525.2376.

High Speed Data Systems

— Joe Spring

If you have ever considered a high speed data system for your aircraft, but ruled it out because the price was too high, you may want to reconsider. Prices are coming down while the technology is getting better.

If your business would benefit from having email, web and video conference access while you’re in the air, please contact Dennis DeCook at 800.525.2376, ext. 8418.

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