Aviation Recommendation rec-A04H0001

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:

As the investigation proceeds, the Board may make further safety recommendations should additional safety deficiencies be identified.

Appendix A -  TSB Calculated Weights for C-FAGA on Take-off at Pelee Island (CYPT)