The Passengers Who ‘Caused’ a 737 Tail Strike
…pitched nose-up just after take -off thrust had been selected. The pitch up movement stopped when the aft fuselage and the tailskid assembly contacted the runway. The crew rejected the take -off, after which the aircraft’s nose came down again to the ground. The aircraft sustained damage to the lower fuselage area in front of the tailskid, to the tailskid and to the nose gear. There were no injuries to persons.
So what did the passengers have to do with this? Well, nothing in relation to any action they took but everything to do with it in relation to the body weight of the 113 passengers and where they had been allocated seats! The aircraft was scheduled for flight from Rotterdam, via Maastricht-Aachen to Arrecive, Lanzarote. The DSB found that:
…nearly all passengers at Rotterdam Airport were checked in at the rear of the cabin and seated themselves there. To facilitate boarding at the next airport (Maastricht-Aachen Airport) the ground handling company Aviapartner had assigned these rear seats to the passengers at Rotterdam Airport. After all, this allowed passengers at MaastrichtAachen Airport to seat themselves in front of the cabin. Because of the uneven passenger distribution, the aircraft’s centre of gravity was situated far behind the applicable aft limit. As a result the nose of the aircraft pitched up and its tail touched the ground.
The DSB used Tripod-Beta as an accident analysis tool. Tripod-Beta is derived from classic bow-tie theory.
The DSB identified four main groups of contributing factors:
- The flight crew’s centre of gravity awareness (and so failed to “respond adequately” when the cabin crew reported the uneven passenger distribution)
- The loading procedures (a “process of producing the load and trim sheets is separated in time and place from the process of actual loading”)
- The airline’s supervision of its ground handling company, who had come on contract the previous year, and the airline’s quality system (both inconsistent reporting and “an internal audit, identified several deficiencies…[but] the subsequent corrective actions…were insufficient” say the DSB, and while crew had reported loading problems in the past, various methods had been used, limiting the ability to detect a trend)
- The effectiveness of the ground handling company’s quality system (as the DSB say the company “did not instruct and train its staff sufficiently”)
The DSB also state:
Search in databases of other Safety Boards and international organizations revealed that similar occurrences of uncommanded pitch up movements on the ground had occurred. In three cases the aft limit of the CG for take-off was exceeded. The cause was that the distribution of the passengers in the cabin deviated from the load and trim sheet used by the cockpit crew. In another case a significant error in the CG calculation itself was made.
Consequently recommendations were raised. To the airline:
- Enhance its pilot’s awareness about the effect of passenger distribution on the centre of gravity of Boeing 737-800 aircraft, and
- Evaluate its quality system, in particular regarding the:
- supervision on contracted ground handling companies;
- results of audits, and the effectiveness of associated corrective actions;
- procedures about reporting safety-related occurrences.
To the ground handler:
- Improve its quality system as such that shortcomings regarding the dispatch of passengers become visible.
To Minister of Transport, Public Works and Water Management (the regulator):
- Orchestrate the draft of quality and safety regulations for ground handling companies by the European Aviation Safety Agency (EASA).
We have covered other loading events previously:
- Inadequately Secured Cargo Caused B747F Crash at Bagram, Afghanistan
- Misloading Caused Fatal 2013 DHC-3 Accident
- Culture + Non Compliance + Mechanical Failures = DC3 Accident
- Wait to Weight & Balance – Lessons from a Loss of Control
- UPDATE 20 December 2016: Time Pressures and Take-Off Trim Trouble
A previous US National Transportation Safety Board (NTSB) investigation into the loss of Fine Air Douglas DC-8-61 cargo aircraft N27UA on 7 August 1997 at Miami is also worth examination. Safety issues discussed subsequently by the NTSB include the effects of improper cargo loading on aircraft performance and handling, operator oversight of cargo loading and training of cargo loading personnel, the loss of critical flight data recorder information, and Federal Aviation Administration (FAA) surveillance of cargo carrier operations. UPDATE 18 December 2017: In 2009 Tail-struck A320’s crew originally chose to continue flight
Italian investigation authority ANSV…determined that 77 passengers had disembarked at Verona, after the BH Air jet arrived from Hurghada, but that the remaining 87 passengers flying onwards to Rome were not redistributed. Fifty-eight of these passengers had been in the aft cabin and another 25 in the centre cabin, with just four up front. But although the ramp agent told ANSV that he had submitted a load and trim sheet to the captain, and had told the cabin manager that passengers need to be reseated, this redistribution was not carried out – possibly owing to a language misunderstanding. The captain nevertheless approved and signed the load sheet. As the aircraft reached 60kt it struck its tail on the runway, and further fluctuations, with lower intensity, showed the jet suffered “repeated” strikes, says the inquiry. …a cabin altitude warning, indicating pressurisation problems from the damaged fuselage, sounded as it climbed through 9,750ft. ANSV says that the crew had decided to continue the flight, “contrary” to operating procedures which required an immediate return to the airport in case of tail-strike… The crew opted to return to Verona “only after the activation of [the pressurisation warning]”, the inquiry adds, and did not specify the reason to air traffic control.
G-FDZJ was operating a charter flight from Malta to Manchester on behalf of a cruise ship company. On takeoff the pilot flying found the aircraft required significantly more aft control column movement than normal to rotate. The available evidence indicates that the aircraft was out of trim due to an incorrect MACTOW on the load sheet. This occurred because passenger’s actual seating positions were not passed to the handling agent. When producing the load sheet the handling agent assumed an even distribution of passengers within the cabin, when the actual distribution created a forward bias.
UPDATE 9 February 2018: The Irish AAIU explain how during preparations for departure from Dublin of ATR72-212 EI-FAV on 23 July 2015 the passenger baggage was placed in the aft aircraft baggage hold instead of the forward baggage hold. “The aircraft departed with the Centre of Gravity outside approved loading limits. The aircraft subsequently landed at its destination where the loading error was discovered”.
UPDATE 13 April 2020: Inadequately Secured Pallets Penetrate the Rear Pressure Bulkhead of a Cargo B737
UPDATE 8 October 2020: UK AAIB have reported on a case where a Wizz Air UK Airbus A321 G-WUKG was substituted for an A320 but due to a communication failure no adjustment had been made to the passenger distribution:
The aircraft was departing from Runway 26 at London Luton Airport, but when the PF made a normal aft movement of the side stick control at rotation airspeed, the aircraft did not pitch up. The PF increased the side stick input close to the maximum deflection. When the aircraft still did not pitch up, the PM selected TOGA thrust. The aircraft responded and a climb was commenced with the flight continuing to the planned destination of Prague Airport, Czech Republic.
Following this event, the operator took action to: highlight this event to its staff and improve their understanding of the issues raised; and improve the flow of information between operational departments when there is a change of aircraft type to reduce the risk that a similar event would occur in the future.
UPDATE 12 October 2020: Runaway Dash 8 Q400 at Aberdeen after Miscommunication Over Chocks