May 1, 2006 | Mark Paradies

Monday Accident & Lessons Learned – Aviation Equipment Failures – Another Example of a Mechanical Failure Starting an Even Larger Failure

Attached (click on the continuation link below) is a report from an aviation failure on a small plane (not a jet).

This is another example of a small mechanical failure (a generator failure) that could have led to a larger failure (loss of the plane and loss of life of the crew and passengers).

What is the lesson I think you should learn?

That equipment reliability is a key part of system performance and SAFETY.

Safety professionals should help maintenance and equipment reliability folks find the root causes of equipment problems by using TapRooT(R). That’s why safety folks (in addition to equipment reliability and maintenance professionals) should attend Equifactor(R) Training.

For general Equifactor(R) information see:

For 3-Day TapRooT(R)/Equifactor Equipment Troubleshooting and Root Cause Failure Analysis Training see:


Incident: Multiple Electrical Systems Failures

1. En-route from — to — (First Officer Flying Pilot) at 9000 ft msl, about 30 Miles north of —. The Left Gen tripped off line, and momentarily came back on. The Volt Ammeter showed the Left Gen accepting a load. Then the process repeated, with the Left coming back on-line. For a third time, the Left Gen tripped and this time did not reset itself, nor would it reset manually.

2. During the next few minutes, the following were noted: a right Gen load of approximately .45, a left Gen load of zero, no ability to reset the left Gen, a red light in the gear handle, failure of the pressurization system, failure of the left fuel gauge, failure of the number one Comm radio, failure of the transponder’s mode C, a red “Computer” flag on the left ADI, failure of the #1 inverter, the inability to lower the flaps, and gear. Failure of the Primary Pitch trim. ATC (APP) was notified of the initial Communications Radio problems, and informed us of the Transponder Mode C failure. No assistance was requested at that time.

3. About 30 miles out of — a call was made to the Company requesting the assistance of Maintenance. Due to the limitations of one Comm radio, numerous changes back and forth were required.

4. The aircraft was slowed to about 130 KIAS in the vicinity of —, and the gear selected down. Nothing happened.

5. The Emergency Gear extension procedure checklist was reviewed. Then followed. During this period approximately sixty strokes of the (emergency) gear handle were applied. Seeing no green gear lights, and realizing that the electrical failure may have affected those lights, they were tested and failed to illuminate. We concluded they would not illuminate. This meant we could not stop pumping at the normal indication (three green) as taught in Ground School.

6. Flaps Approach were selected. The flaps did not move as observed from the cockpit.

7. The gear position was uncertain. Given that, and the multiple systems failures, an Emergency was declared with Tower.

8. A fly by of the tower was conducted. An aircraft at the runway hold line for Rwy 35. A regional airliner at the hold line suggested the gear looked normal. The Tower reported a “bowed appearance”. We proceeded to the East of the Airport and Called Company for about the fourth time.

9. The passengers received a preliminary briefing of the difficulties, and were told we were working closely with maintenance and ATC.

10. The emergency gear handle was pumped about twelve (12) more strokes, and resistance was met. Pumping ceased.

11. Another low pass down the runway was made. Tower reported gear appeared down. Company called again for further consultation with MX Personnel.

12. The passengers were briefed again. Brace positions were reviewed, and coats were passed forward to act as a cushion for passenger seated on the couch adjacent to the bulkhead.

13. An audible signal for assuming the brace position was agreed upon (the tone generated by cycling of the FSB sign).

14. Multiple systems were secured (lights – which had failed anyway, Bleed Air, and the checklist for an aborted landing with inability to stop on the runway was reviewed for action items. The F/O was briefed as to his actions, and as to those the Captain would accomplish.

15. A power on, zero flap landing with a Ref speed of 110 KIAS was made. The gear appeared normal, and the aircraft exited Rwy 35 at Delta Taxiway were it was shut down, and the passengers deplaned to a safe location at the edge of the taxiway.

#1 Generator bearing failure followed by 325 amp current limiter failure.

This would have been a challenging failure: 1) in low IFR, 2) at night, 3) in icing conditions, or 4) at altitude as oxygen masks are not connected when the depressurization starts, and the emergency descent calls for gear down (not possible) creating a longer time lapse in getting down.

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