A04H0001 - Standard Passenger Weights - Use and Validity of Standard Values
Background
On 17 January 2004 at 1638 eastern standard time, Georgian Express Flight 126 (GGN 126), a Cessna Caravan 208B, C-FAGA, departed Pelee Island, Ontario, en route to Windsor, Ontario. There were nine passengers and one crew member on board. Shortly after take-off, the aircraft struck the ice-covered surface of Lake Erie, fatally injuring all 10 occupants. Although the investigation (A04H0001) is ongoing, there is factual information to suggest that the aircraft's weight was a contributing factor in the accident. The maximum take-off weight in the Cessna aircraft manual is 8750 pounds (cargo pod installed) or 8550 pounds if flying into known icing conditions. The investigation determined that the actual weight of the occurrence aircraft on departure from Pelee Island was approximately 9820 pounds, 1270 pounds over gross weight (see Appendix A).
Regulations prohibit the operation of an aircraft unless its weight and centre of gravity conform to the limitations specified in the aircraft manual (Canadian Aviation Regulations [CARs] 703.37, 704.32 and 705.39). For passenger-carrying operations, the calculation of passenger weight is one of the primary determinants of total aircraft weight. In Canadian aviation, the use of Aeronautical Information Publication (A.I.P. Canada) standard weights is the common means of determining passenger weight. However, recent studies in the United States have shown that the current values for standard passenger weights are no longer representative of the general population.
The standard weights published in A.I.P. Canada incorporate the weight of clothing and carry-on baggage. In the Pelee Island accident, the calculated weight for the persons on board using standard weights was 1833 pounds; the actual weight of the persons on board and their clothing was 2400 pounds. This represents a difference of 567 pounds (see Appendix A). For a small aircraft such as the Cessna Caravan, using average weight instead of actual weight can have serious performance implications.
Validity of Standard Weight Values
On 27 January 2003, the Federal Aviation Administration (FAA) issued Notice N8400.40 in reaction to a recent commuter air crash that had raised concerns related to aircraft loading and the use of average weights in weight and balance control programs. The Notice required operators of aircraft with 10 to 19 seats to conduct a survey to validate average passenger weights. The results of the survey indicated that the current standard weight values contained in FAA Advisory Circular 120-27C (dated 11 July 1995) underestimate the average weight of passengers by 20.63 pounds and underestimate the average weight of carry-on baggage by 5.72 pounds.
In light of the similarity between Canadian and American demographics, it is reasonable to conclude that the average weights published in A.I.P. Canada, which include both the weight of passengers and carry-on baggage, no longer reflect the current realities of Canadian society. It is therefore likely that many flights conducted in Canada are operating at a heavier weight than calculated.
The average weight of the passengers on Georgian Express Flight 126 using standard weights was 183.3 pounds (9 men at 188 pounds, 1 woman at 141 pounds). Using actual weights, the average passenger weight was 240 pounds. This represents an increase of 56.7 pounds per passenger from the published standard weights. This is a biased sample, but nonetheless indicates the increased weight of the Canadian population.
The Canadian Aviation Safety Board (the Transportation Safety Board of Canada's predecessor) issued three safety recommendations during the investigation into the crash of a DC-8 aircraft in Gander, Newfoundland (CASB 86-01, 86-02 and 86-03, dated 13 February 1986). These recommendations to Transport Canada (TC) and the National Transportation Safety Board (NTSB) in the United States were directed towards the adequacy of provisions for the use of actual weights versus standard weights. The responses from TC and the NTSB were fully accepted by the Board.
Use of Standard Weights in Small Aircraft
In any statistical application, the larger the sample size, the more closely the sample mean will match the population mean. For large airliners, deviations between the calculated standard passenger weight and the actual weight are minimized by the larger sample size of passengers. Additionally, some airlines apply a larger ratio of men to women to further minimize any weight discrepancies.
A comparison of various aircraft types indicates that the ratio of passenger weight to overall aircraft weight is inversely proportional to the size of the aircraft. For example, in a Boeing 747, the passenger weight represents approximately 9 per cent of the aircraft's weight (450 passengers at 188 pounds, aircraft of 875 000 pounds) whereas the passenger weight in a Caravan can represent approximately 22 per cent (10 passengers at 188 pounds, aircraft of 8550 pounds). For aircraft under 12 500 pounds, there can be significant deviations from the published standard passenger weights due to the small sample size (nine passengers or fewer). This deviation error is further amplified in small aircraft due to the higher percentage of total aircraft weight that the passengers represent. If a small aircraft is being loaded to maximum gross weight, this discrepancy in passenger weight could result in an overweight condition that adversely affects the safety of flight. For example, stall speeds increase with increased aircraft weight; if the pilot is unaware of this change to aircraft performance, the reference speeds used for critical phases of flight will be incorrect.
The NTSB has published numerous recommendations relating to the calculation of aircraft weight. Several of these recommendations dealt specifically with aircraft under 12 500 pounds and the issue of standard versus actual weight. In response to these recommendations, the FAA released an Advisory Circular (120-27C, dated 11 July 1995) outlining the new policy on aircraft weight and balance control. This document states that actual weights for passengers are to be used for aircraft carrying nine passengers or fewer.
There have been numerous accidents in Canada related to overweight aircraft. At least five of these accidents involved small aircraft where discrepancies between the standard and actual weight of passengers contributed to the overweight condition and the accident. Four of these accidents were fatal, involving 24 fatalities. There are 3564 commercial aircraft in the small aircraft category (less than 12 500 pounds) operating in Canada. These aircraft conduct thousands of flights on a daily basis. Companies will naturally try to maximize the load to optimize the service and remain competitive with other companies. This means that, on any given day, many flights operate at close to maximum gross weight on paper when, in fact, some of these flights are operating above maximum gross weight. The use of standard weights in these aircraft exposes the industry to a high degree of risk.
TC's Generic Company Operations Manual - CAR 704, section 3.9.6, and A.I.P. Canada RAC 3.5 state that actual weight should be used to calculate passenger weight unless that information is unavailable. Air operators have three options to calculate passenger weight: use actual weight, use standard weights as published in A.I.P. Canada RAC 3.5, or use standard weights obtained through an operator survey. The most common practice is to use standard weights, as indicated in the Pelee Island operation where standard weights were used for 155 of the 165 flights.
The defences against the risks associated with using standard weights are not adequate for aircraft carrying nine passengers or fewer. The use of actual passenger weights in small aircraft would provide a greater margin of safety. Additionally, the surveyed passenger weights in the United States and the investigation results indicate that the published standard weights no longer reflect Canadian society. It is therefore likely that many flights conducted in Canada are operating at a heavier weight than calculated.
Therefore, the Board recommends that:
The Department of Transport require that actual passenger weights be used for aircraft involved in commercial or air taxi operations with a capacity of nine passengers or fewer. (A04-01)
Transport Canada's Response:
Current regulations make it clear that air operators are to ensure that their aircraft are flown within the limits of the weight and balance envelope and that the standards provide options that may be used but do not override the regulatory requirement to remain within the weight limits of the aircraft. Transport Canada (TC) continues to review the standards with a view to improving the direction provided. One option that is under consideration is the use of actual weights for all operations conducted under subpart 3 (Air Taxi Operations) of Part VII (Commercial Air Services) in the Canadian Air Regulations (CARs). Once our review, including a risk assessment, is complete, Notice of Proposed Amendments (NPAs), (if required) will be developed and submitted to the Canadian Aviation Regulation Advisory Council (CARAC) for consultation.
The Department of Transport re-evaluate the standard weights for passengers and carry-on baggage and adjust them for all aircraft to reflect the current realities. (A04-02)
Transport Canada's Response:
TC re-evaluated the standard weights for passengers and carry-on baggage and adjusted them for all aircraft to reflect the current realities.
Commercial & Business Aviation Advisory Circular (CBAAC 0235) and Policy Letter were issued in October and the Aeronautical Information Publication (A.I.P.) published weights will be amended January 20, 2005 (see chart below). Operators whose approved weight and balance control program is based on the A.I.P. weights will need to amend their programs to reflect these new weights.
| Summer | Winter | |
| 200 lbs or 90.7 kg | MALES 12yrs up | 206 lbs or 93.4 kg |
| 165 lbs or 74.8 kg | FEMALES 12yrs up | 171 lbs or 77.5 kg |
| 75 lbs or 34 kg | CHILDREN 2-11yrs | 75 lbs or 34kg |
| 30 lbs or 13.6 kg | *INFANTS 0 to less than 2yrs | 30 lbs or 13.6 kg |
*Add where infants exceed 10% of Adults.
Appendix A - TSB Calculated Weights for C-FAGA on Take-off at Pelee Island (CYPT)
| Aircraft basic weight | 4991 lb. |
| Weight of fuel on departure | 1735 lb. |
| Fuel for start/taxi | -35 lb. |
| Weight of cargo | 589 lb. |
| Weight of dogs | 140 lb. |
| Actual passenger weight | 2400 lb. |
| Gross weight on take-off | 9820 lb. |
| Maximum gross weight in icing | 8550 lb. |
| Excess weight | 1270 lb. |
| Aircraft basic weight | 4991 lb. |
| Weight of fuel on departure | 1735 lb. |
| Fuel for start/taxi | -35 lb. |
| Weight of cargo | 589 lb. |
| Weight of dogs | 140 lb. |
| Standard passenger weight | 1833 lb. |
| Gross weight on take-off | 9253 lb. |
| Maximum gross weight in icing | 8550 lb. |
| Excess weight | 703 lb. |
| Actual passenger weight | 2400 lb. |
| Standard passenger weight (9 men at 188 pounds, 1 woman at 141 pounds) |
1833 lb. |
| Underestimation of passenger weight | 567 lb. |
A02P0261 - Engine Power Loss in Flight - Cathay Pacific Airways Airbus A340-300 B-HXN - Timmins, Ontario 40 nm W 20 October 2002
Cathay Pacific Airways
Timmins, Ontario 40 nm W
Synopsis
The Cathay Pacific Airways Airbus A340-300 (CPA829), B-HXN, departed Toronto/Lester B. Pearson International Airport, Ontario, at 2352 eastern standard time on a scheduled flight to Hong Kong, with a planned refuelling stop in Anchorage, Alaska. There were 249 passengers and 13 crew members on board. One hour and nine minutes into the flight, while cruising at flight level 350, the pilots felt an airframe vibration and observed the number 1 engine shut down spontaneously. All cockpit indications leading up to the engine power loss were apparently normal. The pilots secured the number 1 engine in accordance with the quick reference handbook, continued flight on three engines, and diverted to Vancouver International Airport, British Columbia. CPA829 landed at Vancouver at 0105 Pacific standard time without further incident.
Safety Action Taken
CFM International (CFM) issued Service Bulletin (SB) 73-0126 (published as CFM56-5C SB 73-0126, dated 13 November 2003). The SB changes the electronic control unit (ECU) software version from C.3.G to C.3.J and ensures that ECU electrical power successfully reverts to aircraft power in the event of a complete or partial permanent magnet alternator (PMA) failure. While this SB applies only to the Airbus A340 and the CFM56-5C engines, all CFM ECU software for the CFM56-5 series will have the improved logic at the next scheduled version release.
In October 2003, Airbus revised the A340 maintenance manual to include specific checks during the removal of the PMA for evidence of rotor/stator contact and radial play of the PMA drive shaft.
Safety Action Required
Continuing Airworthiness
SB 73-0126 will update the ECU software to ensure that electrical power will successfully revert to aircraft power. This SB applies only to the Airbus A340 aircraft, and, although CFM recommends implementation within six months, the actual timeframe for accomplishing this SB is at the discretion of the operator. Additionally, Airbus advises that it has launched similar initiatives to incorporate software updates on CFM56-5A and -5B engines used on its A319, A320, and A321 family of aircraft. It is anticipated that compliance for these SBs will likewise be at the discretion of the operator. As of November 2004, the total number of aircraft in the Canadian civil aircraft register affected by these SBs approximated 120, most of which are two-engine aircraft.
Given the number of aircraft affected, the known problem with PMA bearing failures, the critical function that the ECU software provides in ensuring engine reliability, and the discretionary nature of the proposed software updates, the Board is concerned that, without regulatory intervention, this known unsafe condition will remain in service well beyond the manufacturer's recommended six-month timeframe for the implementation of SB 73-0126. The Board therefore recommends that:
The Department of Transport ensure the continued airworthiness of Canadian-registered aircraft fitted with the CFM56-5 series engine by developing an appropriate safety assurance strategy to make certain that, in the event of a permanent magnet alternator failure, the electronic control unit will revert to aircraft power. A04-04
Transport Canada's Response:
Through communication with the Canadian aviation industry, Transport Canada has confirmed that all Canadian aircraft presently affected by CFM Service Bulletin 73-0126 will have their ECU software upgraded to version C.3.J by March 2005 therefore; Transport Canada is not planning on taking any further action.
Should you require further information, please contact Aviation Safety Analysis at asi-rsa@tc.gc.ca