Q4681 - Lamp Halogen Sealed Beam PAR 46 Light Bulb

Q4681 – Lighting Aircraft Lamp (PAR 46)

Part Number: Q4681

Standard Compliance: ANSI Q4681

Common Synonyms: PAR 46 Landing Light, Quartz-Halogen Taxi Light, 28V 150W Bulb

Overview Section

The Q4681 is a high-intensity Quartz-Halogen sealed beam lamp designed for primary aircraft exterior lighting. Featuring the PAR 46 (5.75-inch diameter) form factor, this lamp is a high-performance solution for heavy-duty aviation applications.1 It is primarily utilized as a Landing Light or Taxi Light on 28V electrical systems common to business jets, turboprops, and military transport aircraft.

Unlike standard incandescent bulbs, the Q4681 utilizes Quartzline® technology—a halogen cycle process that prevents the internal blackening of the glass envelope. This ensures that the lamp maintains nearly 100% of its initial light output (luminous flux) throughout its entire service life, providing pilots with consistent, penetrating visibility during the most critical phases of flight and ground operations.

Enhanced Technical Data

Advanced Engineering & Structural Application

The Q4681 is engineered for Optical Precision and Thermal Stability. In the aviation environment, landing and taxi lights are subject to intense heat during ground holds and rapid cooling (thermal shock) upon takeoff.

Engineering Insight: The Halogen Cycle

The Q4681 utilizes a pressurized halogen gas charge. As the tungsten filament evaporates during operation, the halogen gas chemically bonds with the tungsten atoms and redeposits them back onto the filament rather than allowing them to settle on the glass.2 This "self-cleaning" cycle allows the filament to run at significantly higher temperatures—producing a whiter, brighter light (approx. 3000K) that improves color contrast for the pilot compared to the yellowish tint of standard incandescent lamps.

The PAR 46 Advantage

The "PAR" (Parabolic Aluminized Reflector) design integrates the reflector, light source, and lens into a single, hermetically sealed unit. The PAR 46 size offers a larger reflective surface area than the smaller PAR 36, allowing for a more controlled beam pattern and better heat dissipation, which contributes to its impressive 1,000-hour rated life.

Aircraft Compatibility

The Q4681 is a standard-fit lamp for a wide variety of 28V heavy-duty aircraft systems:

• Beechcraft King Air / 1900: Often used in the main landing gear or nose gear taxi light positions.

• Cessna Citation Series: Utilized in various wing-root or nose-mounted lighting assemblies.

• Lockheed C-130 Hercules: Common in secondary exterior illumination and recognition roles.

• Regional Turboprops: Standard for many ATR and Dash-8 lighting configurations.

The Q4681 is the definitive choice for pilots who demand superior visibility during nighttime operations. By utilizing advanced Quartzline® halogen technology, this PAR 46 lamp delivers a wide, consistent beam that effectively illuminates taxiway markings and runway environments. With a 1,000-hour service life—nearly double that of some standard lamps—the Q4681 reduces maintenance frequency and lowers the total cost of ownership for fleet operators. Ensure your aircraft meets the highest standards of safety and exterior lighting performance with the proven reliability of GE Aviation lighting.

Installation & Maintenance Addendum

1. Terminal Security: When installing the Q4681, ensure the screw terminals are tightened firmly. Use high-temperature ring terminals to prevent wire fatigue and resistance buildup at the connection point.

2. Housing Inspection: Before installing the new lamp, inspect the "light bucket" or housing for moisture or corrosion. A compromised seal can lead to terminal arcing and premature lamp failure.

3. Orientation: Note the "TOP" or "UP" marking on the borosilicate glass lens. The Q4681 provides a horizontal flood pattern; incorrect orientation will result in a vertical beam that may blind oncoming pilots or provide insufficient ground illumination.