DAVID LEARMOUNT / LONDON
Safety statistics this year so far show there have been fewer fatal accidents, but controlled flight into terrain remains a scourge
This year to date has confirmed that the scourge of controlled flight into terrain (CFIT) accidents, which blighted the same period in 2002, is far from being conquered. Half of all the fatal accidents from January to June inclusive come under the CFIT heading - the same proportion as last year.
A redeeming factor is that there have been fewer fatal accidents and fatalities this half-year - almost half the numbers in both cases (see charts). On 30 June 2002 the number of fatal accidents was 18 and fatalities totalled 716, but this year the numbers are respectively 12 and 362. The number of fatal accidents is at its lowest for 10 years, but fatalities have often been far fewer - there were only 114 in the first six months of 2001. Nevertheless, fatal accident numbers and fatalities were well below the average for the first six months of each year for a decade through 2003, respectively 19 and 430.
The CFIT accidents have predictable components, including the fact that they all occurred on non-precision approaches. The Flight Safety Foundation (FSF) Approach and Landing Accident Reduction (ALAR) working group has determined that this makes CFIT during approach up to five times as likely as when a precision aid is being used.
Maintenance faults?
Other features that distinguish this year include the large proportion of accidents caused by technical faults. At least one case is maintenance-related and others may be (see accident listings P40).
In at least two of the four cases the crew could not have intervened successfully to save the aircraft or passengers, and the inquiries will reveal what chance they had in the other two.
But there are more features confirming the year as distressingly predictable, in the sense that established weaknesses continue to show themselves. The main factor is that airlines from the poorer or more immature economies continue to record most accidents, suggesting that the quality of safety standards oversight and national aviation safety cultures still needs attention. Four of the fatal accidents either took place in the former Soviet states, or involved aircraft manufactured or registered there, or combined at least two of those factors. Ukrainian airlines that accept charters overseas are not earning themselves a good reputation, with two civil airlines hired to carry military personnel or their families causing the deaths of some or all of those on board.
Meanwhile, African states saw three of the accidents, Turkey two and Indonesia two. The rest were geographically scattered single accidents, including one each for the statistically safer regions of Australasia, Europe and the USA.
The US accident involved an Air Midwest Beech 1900 that the National Transportation Safety Board believes might have had mis-rigged control runs to the elevators. After take-off the aircraft pitched dramatically to 52¡ nose-up and stalled during the climb away from the runway as the 1900 lost speed. Mis-rigging of controls leading to a fatal accident is rare, but if the final report determines that this was the probable cause it will be interesting to see what recommendations can be made about maintenance practices and pre-flight checks that have not already been made many times.
Weight adjustment
But the accident will be remembered for precipitating a regulatory change that many observers have thought for years was overdue: a reassessment upwards of the assumed weight of the average passenger, which the airlines use for their pre-flight weight and balance calculations. The aircraft had a full load of 19 passengers and luggage, and the NTSB observes that although the weight and balance calculations were carried out according to the rules, the aircraft might have been overweight at take-off. This may not have caused the accident but it would certainly have put the aircraft's performance closer to the edges of the flight envelope, making recovery from any upset less likely. The Federal Aviation Administration has carried out an initial study and determined that average passenger weight is now 9kg (20.5lb), or 12%, greater than was assumed by regulations, and average carry-on baggage is 4.5kg heavier. For the time being US airlines are required either to ask passengers their weight and add 4.5kg or to weigh them to determine the actual load. Meanwhile, in the longer term the FAA is carrying out a more detailed study of the weight of passengers and their baggage, relating it to different types of operation, environments, seasons and markets, with a view to issuing new regulations controlling passenger and baggage average weight.
Brest mystery
The crew of the Brit Air Bombardier CRJ100 that crashed on final approach to Brest in France did not face conditions unusual for that airport, the investigators say there is no indication of an aircraft fault, and the pilots were using the instrument landing system as guidance. But the aircraft still crashed 2km (1nm) short of the runway, beyond the range at which the pilots would have been able to see the approach or runway lights in the prevailing visibility.
The captain was the pilot flying, and in the last 25s of flight - for no clear reason - the aircraft began to diverge above and then below the glideslope, veering left of the centreline, according to French air accident investigation agency BEA. According to information released so far, when the aircraft became low the co-pilot called for the pilot to increase power, but the engines did not spool up until after the ground proximity warning system alert began, and it is not yet clear who moved the power levers forward.
After impact with the ground, the aircraft's fuselage appears to have come to a halt intact, but fire quickly took hold and destroyed the aircraft. The captain was the only person on board who did not survive. Although the BEA will not comment on the possibility of the captain's gradual physical incapacitation, the Brest public prosecutor says he considers it likely. If it was the cause, although the incapacity of one of the pilots in a transport aircraft is rare, it is even more rare for an accident to result from it, let alone a serious one. There is no indication that medical mishaps are more likely to occur on the approach than in other phases of flight, so if incapacitation were to be found as the cause of this accident, it was extremely unlucky that it occurred at such a critical time.
Pushing ETOPS limits
One inflight engine shutdown this year (see non-fatal accidents and incidents listing) has tested the extended range twin engine operations (ETOPS) regulations literally to their limits. On 17 March the crew of a United Airlines Boeing 777-200ER saw the oil pressure on the No 2 Pratt & Whitney PW4090 engine dropping fast and shut the engine down. Then they flew for more than the advisory maximum of 3h on the remaining engine and landed safely at Kona in the Hawaiian islands. The United crew report says that "everything went like clockwork", but no-one has remarked on how long it felt to fly for 3h on one engine above the Pacific. The FAA says that this was the longest ETOPS diversion so far.
Source: Flight International
