Airwork Flight 23
Encyclopedia
Airwork
Flight 23 was a New Zealand Post
cargo flight between Auckland International Airport
(AKL/NZAA) and Woodbourne Airport
(BHE/NZWB) that disintegrated on 3 May 2005.
Immediately after take off the autopilot
was engaged and it controlled the aircraft during its climb to flight level 220. The flight was continued at full power instead of cruise setting to make up for lost time for the next fifteen minutes. On powering down to cruise power, the captain noticed imbalance between the fuel tanks and initiated cross flow procedures. Shortly after, at 10:13 P.M. local time, the plane entered a spiral descent and broke up, killing both pilots.
(TAIC). It found that when the captain noted the fuel imbalance, he said, "We'll just open the cross flow again… sit on left ball and trim it accordingly." He repeated the instruction five times in the next 19 seconds, to which the co-pilot replied, "I was being a bit cautious". The captain said, "Don't be cautious mate, it'll do it good".
This resulted in the plane being flown at a large sideslip angle while still under autopilot control, by means of the rudder trim mechanism. Forty-seven seconds after the cross flow was opened, the captain said, "Doesn't like that one mate… you'd better grab it." One second later they received a "bank angle" warning, followed by a warning chime that was presumably a warning they were straying from their correct altitude.
The investigation came to the conclusion that this was due to the autopilot disengaging, probably due to a servo reaching its torque limit. This meant that there was no compensation applied for the rudder trim input, and the plane entered a roll and steep descent, disintegrating around flight level 199. The investigation found poor visibility at night in low cloud was a factor in preventing the pilots realizing sooner.
Airwork
Airwork is an airline based in Auckland, New Zealand. It operates a joint venture airline, Air Post, which is 50% owned by Airwork and New Zealand Post. It also operates freight services in Australia for Toll Priority...
Flight 23 was a New Zealand Post
New Zealand Post
New Zealand Post, commonly referred by its acronym, NZPost is a State owned enterprise responsible for providing postal service in New Zealand.-History:...
cargo flight between Auckland International Airport
Auckland International Airport
Auckland Airport is the largest and busiest airport in New Zealand with over 13 million passengers a year, expected to more than double by 2025...
(AKL/NZAA) and Woodbourne Airport
Woodbourne Airport
Woodbourne Aerodrome is a small, controlled aerodrome located 3NM west of Blenheim in the South Island of New Zealand, on State Highway Six, Middle Renwick Road.-History:Woodbourne was one of the first airports in New Zealand...
(BHE/NZWB) that disintegrated on 3 May 2005.
History of the flight
The aircraft was scheduled for take off at 9:00 P.M. local time, but it was delayed while cargo was being loaded. During the delay the pilots ordered an extra 570 L (about 1,000 pounds) of fuel and told the person refueling to put all the fuel in the left wing fuel tank, instead of splitting the fuel exactly between the two tanks, as was company procedure. The flight eventually took off at 9:36 P.M. local time.Immediately after take off the autopilot
Autopilot
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. An autopilot can refer specifically to aircraft, self-steering gear for boats, or auto guidance of space craft and missiles...
was engaged and it controlled the aircraft during its climb to flight level 220. The flight was continued at full power instead of cruise setting to make up for lost time for the next fifteen minutes. On powering down to cruise power, the captain noticed imbalance between the fuel tanks and initiated cross flow procedures. Shortly after, at 10:13 P.M. local time, the plane entered a spiral descent and broke up, killing both pilots.
Investigation
The accident was investigated by the New Zealand Transport Accident Investigation CommissionTransport Accident Investigation Commission
The Transport Accident Investigation Commission is a transport safety body of New Zealand. It has its headquarters on the 16th floor of the AXA Centre in Wellington.It was established by Act of the Parliament of New Zealand on 1 September 1990...
(TAIC). It found that when the captain noted the fuel imbalance, he said, "We'll just open the cross flow again… sit on left ball and trim it accordingly." He repeated the instruction five times in the next 19 seconds, to which the co-pilot replied, "I was being a bit cautious". The captain said, "Don't be cautious mate, it'll do it good".
This resulted in the plane being flown at a large sideslip angle while still under autopilot control, by means of the rudder trim mechanism. Forty-seven seconds after the cross flow was opened, the captain said, "Doesn't like that one mate… you'd better grab it." One second later they received a "bank angle" warning, followed by a warning chime that was presumably a warning they were straying from their correct altitude.
The investigation came to the conclusion that this was due to the autopilot disengaging, probably due to a servo reaching its torque limit. This meant that there was no compensation applied for the rudder trim input, and the plane entered a roll and steep descent, disintegrating around flight level 199. The investigation found poor visibility at night in low cloud was a factor in preventing the pilots realizing sooner.
Aftermath
The following improvements were implemented as a result:- On 30 May 2005, the operator issued a Notice to Pilots advising that forthwith the SOP was to give the refueled the volume of fuel to be put into each wing tank to achieve a balanced load prior to engine start, in accordance with the Pre-Start checklist, Metro Training Manual and AFM.
- On 30 June 2006 the operator amended the Metro checklist to add to the Line-up and Approach checklists the item "cross flow closed".
- On 4 July 2006 the operator amended the autopilot Standard Operating Procedures section of the company Metro Training Manual to include two cautions on the use of the fuel cross flow switch.
- On 27 February 2006 the TAIC recommended to the Director of Civil Aviation to amend the AFM, in concert with the United StatesUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
Federal Aviation AdministrationFederal Aviation AdministrationThe Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
, to include a limitation and caution that the autopilot and yaw damper must be disconnected while in-flight fuel balancing is done.
External links
- NTSB Report
- "NZ Post plane explodes killing pilots", article on tvnz.co.nz, 4 May 2005
- "Fuel balancing led to crash", article in The New Zealand HeraldThe New Zealand Herald- External links :* * *...
, 10 August 2005