ATA 27

Oversized Taper Pins
If during inspection of the elevator torque tube assemblies you find the taper pins flush with the collars or adapters, note that Engineering Order (E.O.) DDWW5533576 allows installation of oversized pins. Don’t just continue to pound the taper pins in trying to tighten them up – DO THE REPAIR!

ATA 55

Banjo Fitting
When accomplishing Service Bulletin 1124-55-148 R1, be very careful when drilling out the fasteners along the Station 521.750 frame, also known as the banjo fitting. We have seen several instances of technicians allowing the drill bit to go in too far, damaging the frame face. Also, when replacing the fasteners, use Hi-Loks instead of MS20470e6 series rivets, which are really hard to buck in such a confined area without damaging surrounding structure with the bucking bar.

ATA 27

Flaps Extended, No Retract
Your aircraft has landed at a facility with no maintenance operations on site. The pilot reports the flaps are full down and the flap unbalance light is illuminated. There is not an apparent physical asymmetry between left and right flap surfaces. The fault unbalance condition is thought to be a result of an electrical fault, not a mechanical failure in the flaps drive system.

Question:

1. What action may be taken to retract the flaps to 0° in order to return the aircraft to home base?
2. Once the flaps are retracted, what must be accomplished to render the flaps system inoperative?
3. When the flap unbalance indication exists in flight, is it safe to cycle the flap unbalance test switch in an attempt to clear the fault?

Answer:

1. A maintenance technician may temporarily disconnect the flap comparator asymmetry box electrical connector. This will allow the flaps to be retracted, since the flap comparator relay will be de-energized and allow flap operation. Extreme care must be taken when operating the flaps in this condition. If a true mechanical asymmetry exists, the condition must be thoroughly investigated and the aircraft should not be ferried.
2. The flap comparator box connector must then be re-connected. This will ensure the flaps will not operate if inadvertently commanded to run.
3. No, the unbalance switch should never be used in flight. If the flaps test switch is reset while a true failure exists in flight, the fault may progress to an actual flap asymmetry with negative aerodynamic effects.