737 Tools · Annunciator Lights

An annunciator light just came on. The call is yours. 737 Tools is a technical study and reference companion for 737 NG maintenance, built around that moment: understand the system, find the right box, work the fault — in the right order. Data is 737 NG. Many systems, lights and circuit breakers carry over to the 737 Classic and the MAX, so much of it applies there too — always confirm against the approved documentation for your specific aircraft. ANNUNCIATOR LIGHTS Every light by ATA chapter, with the full technical picture: • What triggers it and what clears it • Fault modes — the same light, different causes depending on switch position or configuration, each with its own path • Related circuit breakers, with panel and exact grid position • The LRUs involved • Related MEL items, with a clear NO DISPATCH warning • Your own field notes, saved on the light E/E TOUR — FIND THE COMPUTER Troubleshooting usually ends with a BITE test on a box you first have to find. The E/E Tour is a photographic walkthrough of the electrical/electronic compartment with every LRU marked on real photos of the bays. Tap a marker and you know the shelf and the neighbours before you open the hatch. CB panels are mapped the same way, each breaker pinpointed on the panel image. Pinch to zoom, double-tap to move in, swipe between bays. DAMAGE REPORTS Lightning strike inspections, hail, ground equipment contact — a dozen findings scattered across the airframe and a notebook full of loose photos. Create a report, add each finding with photos, location and measurements, keep them organised as one job, and export it as a PDF or ZIP from the aircraft. Paperwork you close out on the spot. COMMON PN Every line and hangar has its own short list of part numbers. Build your own catalogue: add each PN with photos and notes, organised by zone and category, and export your collection to share it with the team. ON THE RAMP • Fully offline — no signal needed at the stand or in the hangar • One search box across lights, LRUs, circuit breakers and part numbers • No account, no cloud — your notes, reports and PNs stay on your phone • Full backup to a single file, saved wherever you like TRAINING AND REFERENCE ONLY Designed for aircraft systems study and fault simulation. Information may not be current or fleet-specific and does not replace approved AMM, FIM, MEL or any official documentation — always work from the current approved manuals and your operator's procedures. Independent app, not affiliated with, authorised by or endorsed by any aircraft manufacturer.