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Accident description
Last updated: 11 December 2017
Status:Final
Date:Thursday 15 June 2000
Time:14:00
Type:Silhouette image of generic SW4 model; specific model in this crash may look slightly different
Swearingen SA227-AC Metro III
Operated by:Eagle Airways
On behalf of:Air New Zealand Link
Registration: ZK-RCA
C/n / msn: AC-637
First flight: 1986
Total airframe hrs:24797
Cycles:36925
Engines: 2 Garrett TPE331-11U-611G
Crew:Fatalities: 0 / Occupants: 2
Passengers:Fatalities: 0 / Occupants: 0
Total:Fatalities: 0 / Occupants: 2
Airplane damage: Substantial
Airplane fate: Repaired
Location:Gisborne Airport (GIS) (   New Zealand)
Phase: Landing (LDG)
Nature:Training
Departure airport:Gisborne Airport (GIS/NZGS), New Zealand
Destination airport:Gisborne Airport (GIS/NZGS), New Zealand
Narrative:
A Swearingen SA227-AC Metro III turboprop sustained substantial damage in a landing accident at Gisborne Airport (GIS), New Zealand. Both pilots were not injured.
ZK-RCA took off from Gisborne for a planned one-hour crew-training flight. A check and training captain (the captain) and a pilot undergoing command training, who was the pilot flying, were on board the aircraft.
The flight included emergency procedure exercises with simulated engine failures, circuits and landings using runway 14. The first circuit was normal using both engines. The second circuit was flown with the left engine power lever retarded to simulate a left engine failure shortly after takeoff. On short final approach a single-engine go-around was commenced from the decision height and the aircraft recircuited with the left engine simulated as inoperative.
The third circuit was flown at an altitude lower than normal. A moderate wind from the south-west created a right crosswind for the landing. The pilots said the approach was normal until about a height of 50 feet before landing when the aircraft descent rate increased. They said the landing was somewhat firmer than normal and firmer than they expected. Although the
aircraft landed straight it began to veer to the left and the pilot under training was unable to maintain directional control. The captain ordered a go-around.
the left undercarriage HAD collapsed rearwards to about 40 degrees past its normal down position.
When the aircraft became airborne the crew selected the undercarriage up but the left undercarriage red in-transit indicator light remained on. After the aircraft climbed to 1500 feet above mean sea level the captain reselected the undercarriage down. The nose and right undercarriage position indicator lights displayed normal green (down) indications but the left
undercarriage red in-transit indicator light remained on.
After the aircraft became airborne the aerodrome controller told the crew that the left undercarriage was not down correctly but was hanging at about 45 degrees. The crew, unsure whether the undercarriage was inclined forward or trailing, loaded the aircraft with positive “g” (vertical acceleration) in an attempt to force the undercarriage into the down locked position.
The red indicator light remained on. The pilot under training then flew the aircraft at low level past the control tower and the controller confirmed the undercarriage was trailing at about 45 degrees aft of its normal down position.
The pilot under training flew the aircraft to the east and to a higher altitude where the crew considered their options. The captain spoke to the company’s Gisborne base manager and company personnel at Hamilton, advising them of the situation. The captain elected to fly ZK-RCA to Hamilton Aerodrome where the company’s headquarters and engineering base were located. Hamilton Aerodrome was an international aerodrome with a higher category of emergency services and a longer runway than Gisborne Aerodrome.
The flight to Hamilton was flown with the undercarriage selected up but at a speed below the undercarriage extended speed limitation of 173 knots. The captain spoke with the operator’s engineering personnel and the Metro fleet captain. Following the fleet captain’s advice the crew swapped seats to occupy their more familiar positions, with the captain in the left seat and the pilot under training in the right seat. The captain completed 2 low approaches and overshoots at Hamilton Aerodrome for engineering and flying personnel to view the undercarriage in the down selected and up selected positions. This was carried out to analyse the possible failure and to assist the captain to decide what action he should take.
In the retracted position the left undercarriage wheels protruded below the engine nacelle some 45 degrees below the normal horizontal up position. The captain decided to land the aircraft with the undercarriage selected up, in accordance with the manufacturer’s recommendation. He orbited over the aerodrome burning off fuel to the minimum, leaving about 10 minutes of fuel to complete a landing, or carry out a go-around for a second approach if necessary.
In the meantime the emergency rescue services and the operator put together a plan to attend the aircraft as it landed and to recover it from the runway. The crash fire service sprayed fire retardant foam along the runway to reduce the potential for fire.
The captain flew a stabilised approach to runway 18. On short final some 50 feet before touchdown he directed the second pilot to pull both the red engine stop and feather knobs. This action cut the fuel supply to both engines and feathered the propellers. The second pilot also closed the fuel shut-off valves and hydraulic shut-off valves. The captain selected the batteries off.
ZK-RCA touched down straight and slid some distance before it slewed to the right side of the runway and onto the grass where it turned through about 170 degrees and came to rest. About 1700 m of runway were used during the landing. The pilots evacuated the aircraft immediately through the emergency exit over the right wing, having already informed the emergency
services of their plan.
Once the pilots cleared the aircraft the emergency fire service sprayed fire retardant under the aircraft around likely hot spots. This action had been predetermined and was taken to eliminate the potential for fire to erupt in the event any fuel lines or fuel tanks had ruptured. The fire retardant was biodegradable and non-corrosive. No fire occurred.

Probable Cause:

FINDINGS:
Findings are listed in order of development and not in order of priority.
1 The aircraft had a valid Certificate of Airworthiness and its records indicated that it had been maintained appropriately and was operating within the required maintenance period.
2 A fatigue crack had started and grown to a critical length in the left undercarriage outboard lower drag brace.
3 The fatigue crack had probably been propagating for less than 15 000 landing cycles.
4 On landing the cracked left undercarriage outboard lower drag brace failed and transferred the load to the inboard drag brace, which failed in overload.
5 A firm landing at Gisborne Aerodrome brought the imminent failure of the drag braces forward.
6 The drag braces did not have a limited service life and were not required to be periodically checked for cracking.
7 Because the cracks in the drag braces could not be detected visually during the routine inspections required by the manufacturer, an approved non-destructive test was necessary.
8 The square edge to the machined recess around the grease fitting acted as a significant stress concentrator, which made the drag braces prone to cracking.
9 The cracking of the drag braces resulted from a design deficiency.
10 The drag brace cracking was potentially common to all the same type of aircraft.

Accident investigation:
cover
Investigating agency: TAIC New Zealand
Status: Investigation completed
Duration: 160 days (5 months)
Accident number: 00-006
Download report: Final report

Classification:



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This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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