How Thorough is Your Test Flight Pre-flight?

Maintenance had just completed a check that required a wing removal on the DC-3. As the test-flight crew levelled the aircraft after takeoff, they used aileron trim to correct a left-wing-heavy condition, but trimming only made the problem worse. They immediately reversed the trim selection and turned for home, landing safely.

Post-flight investigation revealed that the trim was operating in reverse — not the first, nor probably the last time for “Murphy” to strike.

Originally Published: 4/1996
Original Article: Just Briefly - How Thorough is Your Test Flight Pre-flight?

Overweight & Rushed

Seneca Loss of Control

Witnesses who saw the fatal takeoff described the takeoff run as long; the aircraft looked slow and mushy; the wings were rocking immediately after lift-off; and it wavered from side to side before banking steeply into the ground.

Would-be rescuers arrived at the scene within seconds but found no survivors among the four on board. The TSB accident report (A95W0153) records the aircraft as being 400 pounds (eight percent) overweight; the landing gear was down at impact; and the nose baggage door was open.

The Seneca III forward baggage door is located on the left side of the nose, is hinged at the top and opens upward. The door is secured in the CLOSED position by rotating the spring-loaded hatch handle 90 degrees clockwise to the horizontal position. This extends two pins into the doorframe. The key lock is then rotated 90 degrees clockwise to the LOCKED position, and the key is removed from the lock. If the key can be removed at other than the fully locked position, lock and key must be replaced.

A one-time Airworthiness Directives and Piper Service Bulletin requiring inspection of the forward baggage door had been complied with seven years earlier. In addition, one month before the accident, the 100-hours inspection of the door hinges, latches and locks had also been signed off as completed. Yet the investigators' examination found the key and lock tumblers were so worn that the key could be removed in any position. The aircraft was not equipped with a "Door Open" warning light.

The pilot/owner had been observed arguing with one of the passengers, a company employee, before departure. His construction project was behind schedule and four other employees had taken the day off. His distressed emotional state likely affected his pre-flight checks and handling of the aircraft. He may have deliberately maintained a low airspeed to keep the airload from ripping the door away from the airframe. With the added drag of the forgotten landing gear and a higher stalling speed because of his overweight condition, the pilot stalled the aircraft at low altitude. Recovery was impossible.

Sudden opening of the door during takeoff would have been unexpected and visually distracting. The noise level, flight control feedback, possible airframe vibration and increased drag further diverted the pilot's attention from his primary job — flying the aircraft.

Originally Published: ASL 1/1997
Original Article: Seneca Loss of Control

The Accident Chain

Sounds Like...? — The Final Step in Forging the Accident Chain

This is the tale of a PA31 gear-up landing. It starts with an open nose baggage door. But let's go back to the beginning to see how this crew came to do a belly flop and a 1000-foot slide with the sparks flying.

Step One — Design

The first Murphy in the aircraft design is the nose baggage door warning system. The door is equipped with a warning light that will also activate the Master Caution. The door light is activated whenever the nose door is unlatched and the Battery Master switch is ON. However, to activate the master caution light, the system must first be armed. To do that, the nose baggage door must first be latched. If it is not latched when the Battery Master is turned ON, the system is not armed.
Neither light activated during the accident sequence. Although post-slide checks showed both to be functioning normally.

Step Two — Design

The aircraft is equipped with both a landing-gear warning horn and a stall warning horn. Here comes design Murphy number two. Both are solid-tone warnings. The gear warning sounds at 510 +/- 25 hertz; the stall warning at 675 +/- 25 herz. The human ear does not easily discriminate between frequencies this close in range, making it difficult to determine quickly which warning is sounding the alarm — stall or gear? Perhaps one should be a steady tone while the other is an undulating one.
To lessen stress on the open door, the captain had flown the approach at a deliberately low airspeed. When the horn sounded during the landing flare, he assumed it to be the stall warning and he continued the landing.

Step Three — Maintenance

The baggage door closes using a key to turn the lock. Routine maintenance check might have detected the wear, leading to timely replacement.

Step Four — Living with It

On the day prior to the accident, the pilot did not have a key. He used his thumbnail to turn the lock. Tight fit?

Step Five — Writing It Up

There was no record in the aircraft logs that the lock had been reported as unserviceable.
Steps Four and Five go together. If you decide to live with it and don't write it up, it's not going to get fixed, and it's going to turn back and bite you.

Step Six — A Sense of Urgency

As the flaps and gear were retracted after takeoff, the captain noticed the nose baggage door ajar. He elected to make a tight teardrop turn back to land on the reciprocal runway (the winds were calm).
Noise from an open door can be distracting, but flying the aircraft and completing the checklist is vital. Over the past ten years, there have been 53 Canadian incidents involving open doors on all types of aircraft. The vast majority have concluded with uneventful landings. Some, when the pilots got distracted by the noise and sense of urgency, have resulted in gear-up landings. A few have had fatal results.

Step Seven — Cockpit Resource Management

The PA 31 captain decided to reduce approach speed by 10 knots to reduce aerodynamic loading on the door. He instructed the co-pilot to complete the landing checklist, but he concentrated on accurately flying the reduced approach speed. Therefore, he did not fully monitor the co-pilot's pre-landing checks. Evidently, the co-pilot was also distracted by the open door. He missed the Gear Down step in the checklist.

Step Eight — Confirming the Warning

Many checklists or Standard Operating Procedures require that the crew's first step in reacting to a warning be "Confirm," i.e. "Master Caution — Engine Oil Pressure." Check the pressure gauge, and then call for the checklist procedure to be completed.

Perhaps the PA31 pilot expected to hear a stall warning because of his low approach speed, but he did not confirm. He assumed and continued to a belly flop slide down the runway.

Originally Published: ASL 1/1997
Original Article: Sounds Like...? - The Final Step in Forging the Accident Chain