Fokker 100 and Fokker 70 improvement of service life of flightdeck annunciators.
Introduction: Typical section of a Fo100 flightdeck overhead panel |
To prevent flight deck annunciator lights to burn at high intensity for long periods during turn around and maintenance, Fokker Services B.V. introduces an automatic dimming system. The system increases the service life of the flight deck annunciator lights by dimming the pushbutton lights on the flight deck automatically after 15 minutes when the aircraft is on the ground and both engines are off. It ensures that the pushbutton lights are not in Bright-mode at the terminal or during maintenance.
Taking into account the dark flight deck philosophy of the Fokker 100 and Fokker 70, it is evident that the service life of the lights is almost entirely dictated by (prolonged) illumination during on-ground service handling and during maintenance checks. During maintenance checks, the lights can be illuminated in the bright mode for several hours (often without any need).
Failure of a light bulb is detected during the Flight Warning System (FWS) lamp test. It is not allowed to dispatch the aircraft with a detected failure of a light. Delays or cancellations may result because of this.
Benefits:
Analysis indicates that the payback period of the modification is less than 2 years assuming that:
- The number of bulbs to be replaced is reduced by 40 per year per aircraft. Average savings in costs of material and labour costs is approx. 700 US$ per year per aircraft. A total of approximately 425 bulbs are installed per flight deck.
Note: 'net' replacement time is around 5 minutes assuming the tooling and maintenance personnel are available. However, in practice at least 15 minutes is required for all related activities.
 Detail of an opened pushbutton with 4 light bulbs (one light removed) |
- At least one significant delay (> 15 minutes) per aircraft per year is attributed to a failure of one or more annunciator lights on the flight deck.
Please note that a failure of a light bulb is detected during the FWS lamp test and a dispatch of the aircraft is prohibited until corrective maintenance is accomplished.
Related modifications
In addition to the automatic dimming system, Fokker Services B.V. also offers the auto-bright inhibit circuit. The auto-bright inhibit circuit prevents the lights in the flight deck overhead panel to turn bright automatically after a power interrupt on ground.
Introduction of both modifications at the same time is possible and advised to ensure the best improvement in service life of the light bulbs.
Installation:
Manpower for introduction of the automatic dimming system is approximately 60 man-hours. Elapsed time will be 21 hours for 3 men.
Availability :
The automatic dimming system is certified and the modification is available for all Fokker 70 and 100 operators per Service Bulletin SBF100-33-019.
Introduction of the auto-bright inhibit circuit is introduced by Fokker Service Bulletin SBF100-33-018.
Please contact your Fokker Services Account Manager for price and lead-time.