Publications

Issue 25 - February 2002

Runway Incursions on the Rise

TSB occurrence data show that the five-year average for runway incursions rose slightly from a decade low of 23 in 1995 to 30 in 1999. However, industry information indicates that in 1997-1999 there was a significant rise in operating irregularities that had the potential to increase the risk of a collision to aircraft during take-off and landing.
- Report No. A98H0004

Nav Canada and Transport Canada (TC) have both recently studied the rise in runway incursions. In February 2001, Nav Canada released its Runway Incursion Study at Nav Canada ATS Facilities Final Report and outlined strategies for reducing the number of runway incursions. Several of these strategies have already been implemented. TC established a safety review group to examine the problem and, in September 2000, released its Final Report-Sub-Committee on Runway Incursion (TP13795). The Incursion Prevention Action Team (IPAT) has harmonized the recommendations from both reports. The team comprises representatives from both organizations and meets quarterly to work on implementing the recommendations.

One such runway incursion incident led to the risk of collision between a Nav Canada Canadair Challenger (Navcan 200) and a TC airport maintenance vehicle (Staff 61) at Terrace Airport, British Columbia, on 17 December 1998. The quick reaction of the vehicle operator in moving his vehicle to the edge of the runway in the few seconds available most likely prevented an accident.

The Situation

The Challenger was inbound to Terrace after conducting flight inspection of navaids near the airport. At about 1116 local time, above the airport, the pilot of Navcan 200 advised the Flight Service Station (FSS) specialist on the mandatory frequency (MF) that he was joining the traffic circuit on a left-hand downwind for landing on Runway 33. The specialist responded with a wind advisory (wind calm). About one minute later, the pilot advised turning to final for a full-stop landing on Runway 33, and the specialist repeated the wind advisory.

Meanwhile, Staff 61 had been authorized to inspect previous snow-clearing work. The operator stopped a few times to pick up small pieces of snow that had fallen from a runway sweeper during the previous clean-up. Each time, while out of the vehicle, he left the vehicle door open and switched his radio to the rear exterior speaker.

Just before landing, the pilot requested that the specialist advise the aircraft refuelling company that the aircraft was landing. The specialist spent the next 35 seconds on the telephone with a refuelling company employee. At one point, the specialist commented that he could not see the aircraft after landing because it had disappeared into a layer of fog that partially obscured the northern half of Runway 33. At 1117:57, near the end of the telephone conversation with the refueller, the specialist received a radio call from Staff 61. The specialist did not immediately answer Staff 61 because he was still on the telephone. At 1118:03, the pilot of Navcan 200 reported to the FSS that a vehicle was at the end of the runway. At no time was information regarding the presence of a vehicle on the runway relayed to Navcan 200 by the FSS specialist.

Just before the incident, the driver of Staff 61 was about 10 feet (about 3 m) away from the vehicle when he heard a jet engine to the south. He quickly ran to the vehicle, put it in reverse, and backed over to the edge of the runway. Approximately five seconds had elapsed from the time he heard the jet engines until he saw the aircraft pass by. No communication had occurred between the specialist and Staff 61 for the previous 6 minutes 28 seconds until the call from Staff 61 to the FSS at 1117:57.

Prompted by the radio calls from Staff 61 at 1117:57 and the pilot of Navcan 200 at 1118:03, the specialist immediately instructed Staff 61 to exit the runway (the aircraft had already passed the vehicle) and to report clear. Staff 61 responded that the aircraft was already past his position and that he would follow it to the ramp.

Different Radio Frequencies

The objective of the vehicle control service provided by the FSS is to control the movement of ground traffic on the airport manoeuvring area. Ground traffic does not include aircraft; it includes all other traffic, such as vehicles, pedestrians, and construction equipment. A separate frequency is established for the control of ground traffic entering the manoeuvring surfaces of the airport. At airports where a vehicle control service is provided, vehicles do not normally monitor the MF. As a result, the FSS specialist is the focal point and the exclusive repository for all the available information on air and ground traffic. The FSS has the responsibility to ensure that operators are apprised of essential information as required.

Whenever information is compartmentalized to the extent that a single individual or system is the exclusive conduit for that information, a lapse in memory, a deviation from standard procedures, or a technical failure has the potential to result in an accident. In the absence of a sufficient depth of defence, a single lapse resulted in this occurrence. It did not become an accident only because of an unanticipated and unplanned defence: the operator of Staff 61 received information about a landing aircraft from the sound of the approaching jet engines.

The redundancy that would be achieved by providing more than one person/agency access to the information necessary for safe operation is lost when the information is restricted to only the FSS. The capability of the aircrew or the vehicle operator to listen to the other active frequency would have reduced the likelihood of the occurrence happening.

Terrace Snow-Clearing Procedures

At Terrace Airport, the term "work area 15/33" is reserved exclusively for snow-clearing operations. Snow-clearing vehicles are permitted unrestricted access by the FSS specialist to the entire area. While in the area, vehicles are not required to provide position reports to the FSS. This procedure was instituted because of the excessive amount of snow-removal operations at the Terrace Airport and the number of vehicles normally involved, often up to eight. The reduction in radio transmissions and workload between the FSS and vehicle operators was seen as a significant benefit.

The absence of radio communications to and from Staff 61 may have prevented the specialist from recalling the presence of the vehicle at a critical time. Routine communications requirements, such as position reports in the work areas, could have reminded the specialist that a vehicle was on the runway when Navcan 200 initially reported above the airport.

System Defences

A more positive intervention is required to change a specialist's established routine for gathering information to ensure that the pertinent facts are recalled into working memory at the correct time. For example, Nav Canada has installed a SONALERT system at some of its FSS facilities to actively remind specialists that they have authorized a vehicle to operate on a runway. Terrace FSS and technical staff were also developing another system that would activate as soon as a vehicle strip was placed into the data strip board. However, technological systems alone will not be effective unless the FSS specialist consistently follows a disciplined approach to providing air traffic services, that is, scanning the immediate work area as well as the outside environment to gather all available and required information.

Other Follow-up Action

Through the Canadian Aviation Regulation Advisory Council (CARAC) Part III Technical Committee, Transport Canada was examining the extent to which vehicles should be allowed to use aircraft manoeuvring surfaces when transiting from one aerodrome location to another, with a view to reducing the potential for aircraft/vehicle conflicts. Additionally, the committee will determine whether vehicles at uncontrolled airports should be operating on the same frequency as that used by aircraft.

At Terrace Airport, all vehicles that operate on aircraft movement areas have been equipped with receive-only radios tuned to the MF to increase the situational awareness of vehicle operators.

		1995	1996	1997	1998	1999	2000	2001	Total
Halifax	CYHZ	0	1	0	0	1	0	1	3
Dorval	CYUL	0	1	1	1	2	2	0	7
Toronto	CYYZ	3	3	4	2	4	3	10	29
Ottawa	CYOW	1	1	0	1	1	1	3	8
Winnipeg	CYWG	0	0	1	1	5	0	2	9
Calgary	CYYC	1	1	2	3	6	4	0	17
Edmonton	CYEG	0	1	0	0	0	0	0	1
Vancouver	CYVR	1	2	3	1	2	1	4	14

Jammed Rudder

The student pilot in the Cessna 152 pulled the elevator control fully aft, stepped on the left rudder pedal, and the aircraft entered a left spin. Despite proper recovery actions by the student and the instructor, the aircraft continued downward in a stabilized spin until it struck the surface of a lake. The student pilot escaped the aircraft with serious injuries; the flight instructor was fatally injured in the 18 July 1998 accident at Lake Saint-Franois, Quebec.
- Report No. A98Q0114

When the aircraft was recovered from the water, the rudder was found locked in the full left position. It was observed that the rudder stop plate on the right-hand half of the rudder horn was firmly jammed behind its stop bolt on the fuselage. The rudder was deflected 34 measured perpendicular to the hinge line, whereas the maximum allowable deflection for setting the stops is 23. When the rudder was released from its jam, the deflection was 23.

The day before the accident, an apprentice mechanic from Laurentide Aviation at Montral / Les Cdres Aerodrome, where the aircraft was based, carried out a 50-hour inspection of the aircraft. During the check, the right pedal rudder bar return spring and a spring attachment for this spring, which was welded to the rudder bar assembly, were found to be broken. The return spring supplied a tension force of about 10 pounds per inch of stretch and balanced the force exerted by the matching left rudder bar return spring. The two return springs maintain tension in the rudder cables that connect to the right and left halves of the rudder horn. Without the right pedal return spring, the right rudder cable slackens. The left rudder pedal return spring will then tend to pull the right rudder pedal toward the pilots, facilitating deflection of the rudder to the left.

The Aircraft Was Not Airworthy

The apprentice removed, but did not replace, the broken pieces of the rudder control system. He then requested the opinion of a company aircraft maintenance engineer, who judged that the absence of the spring and the bracket would not affect the flight characteristics of the aircraft and decided to release the aircraft for service until replacement parts could be installed.

Because the spring was missing, the aircraft was not airworthy. Further, the required entries were not made in the snag book-used by instructors and other pilots to record aircraft defects-or the journey logbook, which was not available to students and instructor pilots for viewing or recording times or defects. Transport Canada (TC) did not approve the use of a snag book at Laurentide Aviation, and TC inspectors were not aware of its use.

Had the logbooks reflected the defect and been available to the pilots, the flight instructor likely would have been aware that the rudder bar return spring was missing. The instructor then would have had the option of refusing to operate the aircraft in that condition.

During a TC maintenance audit of another flight school operator at Saint-Hubert Airport, discrepancies were noted that led to the grounding of several aircraft, including five Cessna 152 aircraft with reported rudder overtravelling. The audit revealed that there were scratches or score marks on the five airplanes, indicating that the rudder horns had overtravelled above and beyond the stop bolt at some time.

Further tests led investigators to conclude that the accident aircraft entered a left spin with the rudder locked at a 34 deflection. With the rudder jammed the way it was, no amount of right pedal force would have released the jam, because the direction of cable pull tends to increase the jamming by closing the horn.

Safety Action Taken and Required

On 14 March 2000, Cessna notified the TSB that it had designed a rudder horn stop bolt with a larger head diameter to prevent overtravel of the rudder after a hard rudder input. Cessna notified the Federal Aviation Administration (FAA) Certification Office about this manner and expected to issue a service bulletin offering the new configuration rudder stop bolt for all Cessna 150's and 152's built after 1996. A time frame for these actions was not specified.

On 09 May 2000, TC issued a service difficulty alert discussing the accident circumstances and outlining details regarding the inspection of the rudder control system.

While stated action by Cessna is appropriate, the Board is concerned that since the proposed service bulletin will be voluntary, not all Canadian-registered Cessna 150's and 152's will be modified. Therefore, the Board recommended that:

The Department of Transport issue an Airworthiness Directive to all Canadian owners and operators of Cessna 150 and 152 aircraft addressing a mandatory retrofit design change of the rudder horn stop bolt system to preclude overtravel and jamming of the rudder following a full rudder input.
A00-09

Any mandatory airworthiness actions to retrofit Cessna 150 and 152 aircraft with newly designed rudder horn stop bolt systems will likely take considerable time to complete. In the meantime, these aircraft will be flying with a known safety deficiency. The circumstances of this accident suggest that the implications of the broken or missing rudder cable return spring were not fully understood. Moreover, the possibility of an irreversibly jammed rudder during intentional spin entry by full rudder deflection was not understood until this accident investigation was completed. Therefore, the Board recommended that:

The Department of Transport, in conjunction with the Federal Aviation Administration, take steps to have all operators of Cessna 150 and 152 aircraft notified about the circumstances and findings of this accident investigation and the need to restrict spin operations until airworthiness action is taken to prevent rudder jamming.
A00-10

The required logbook entries regarding the maintenance performed on the rudder system were not made. It was evident that the operator, in general, did not maintain the aircraft journey logbooks in accordance with the Canadian Aviation Regulations. Therefore, the Board recommended that:

The Department of Transport take steps to ensure that operators and maintenance personnel are aware, in the interests of safety, of the importance of proper maintenance of aircraft journey logbooks and aware of their responsibilities in this regard.
A00-11

The FAA, as the regulatory body in the State of design and manufacture, has primary responsibilities for continuing airworthiness of the Cessna 150 and 152 aircraft. Therefore, the Board recommended that:

The National Transportation Safety Board review the circumstances and findings of this investigation and evaluate the need for mandatory airworthiness action by the Federal Aviation Administration.
A00-12

Transport Canada issued an airworthiness directive effective 04 August 2000 prohibiting intentional spins / incipient spins in Cessna 150 and 152 aircraft until a rudder system inspection has been carried out and any problems rectified. The rudder system inspection is to be completed at every 110 hours or 12 months, whichever occurs first. Aircraft not performing intentional spins / incipient spins are to be inspected not later than 110 hours or 12 months, whichever occurs first, from the effective date of the airworthiness directive and thereafter at every 110 hours or 12 months, whichever occurs first.

SR111 Firefighting Recommendations

In its ongoing investigation into the 02 September 1988 crash of Swissair Flight 111 (SR111), the TSB has identified safety deficiencies in several aspects of the current government requirements and industry standards involving in-flight firefighting. Each of these deficiencies has the potential to increase the time for an aircraft crew to gain control of what could be a rapidly deteriorating situation. Time is a prime consideration in the successful identification and control of an in-flight fire.
- Occurrence No. A98H0003

SR111 crashed approximately 20 minutes after the crew detected an unusual odour. About 11 minutes elapsed between the time the crew confirmed the presence of smoke and the time that the fire is known to have begun to adversely affect aircraft systems. The TSB reviewed a number of databases to look for events that had similarities to the scenario of SR111.

Fifteen such events were identified, the earliest of which occurred in 1967. For these events, the time from which fire was first detected until the aircraft crashed ranged from 5 to 35 minutes. Each of these accidents had the same characteristic: the in-flight fire spread rapidly and became uncontrollable.

Integrated Firefighting Measures

During the SR111 investigation, the TSB has necessarily looked beyond the specific circumstances of this single occurrence to examine industry standards in the area of in-flight firefighting. The Board believes that industry efforts have fallen short in this area and that the industry should look at fire prevention, detection, and suppression as being the components of a coordinated and comprehensive approach. More needs to be done to develop an effective firefighting system and to ensure that all elements of such a system are fully integrated, compatible, and supported by all the other elements. The SR111 investigation has revealed that a number of safety deficiencies could reduce the chances of an in-flight fire being detected and extinguished in time, such as the following:

• lack of effective fire detection and suppression systems in vulnerable areas of the aircraft fuselage;
• dependence on human sensory systems for the detection of odours/ smoke; and
• inadequate appreciation for how little time is available to detect, analyze, and suppress an in-flight fire.

Therefore, the Board recommended that:

Appropriate regulatory authorities, in conjunction with the aviation community, review the adequacy of in-flight firefighting as a whole, to ensure that aircraft crews are provided with a system whose elements are complementary and optimized to provide the maximum probability of detecting and suppressing any in-flight fire.
A00-16

Smoke/Fire Detection and Suppression

At present, built-in smoke/fire detection and suppression systems in transport-category aircraft are required only in "designated fire zones," which are areas that are not readily accessible and that contain recognized ignition and fuel sources. These areas include powerplants, auxiliary power units, lavatories, and cargo areas.

The Board believes that there is the potential for a fire to ignite and propagate without detection in areas not designated as fire zones, including, but not limited to, the following:

• electronic equipment bays (typically below the floor beneath the cockpit and forward passenger cabin);
• the areas behind interior wall panels in the cockpit and cabin areas;
• the areas behind circuitbreaker and other electronic panels; and
• the area between the crown of the aircraft and the dropdown ceiling (sometimes referred to as the attic area).

The Board believes that the present detection and suppression capabilities in these nondesignated fire zones of the aircraft fuselage are inadequate. Such smoke/fire detection is primarily dependent on human senses. In most transport category aircraft, the occupied areas are isolated from the inaccessible areas by highly efficient ventilation/filtering systems, which can effectively remove combustion products from small fires and impede the timely detection of smoke by human senses. Therefore, small fires can continue to propagate and remain undetected by cabin occupants. Furthermore, any attempt at smoke/fire suppression in these areas would require direct human intervention using handheld fire extinguishers. As the SR111 accident and other occurrences demonstrate, early detection and suppression are critical in controlling in-flight fire.

Therefore, the Board recommended that:

Appropriate regulatory authorities, together with the aviation community, review the methodology for establishing designated fire zones within the pressurized portion of the aircraft, with a view to providing improved detection and suppression capability.
A00-17

Emergency Landing Preparation

The SR111 accident has raised awareness of the potential consequences of an odour/smoke situation, and the rate for flight diversions has increased as a result. Some airlines have modified their policies, procedures, checklists, and training programs to facilitate timely diversions and rapid preparations to land immediately if smoke from an unknown source appears and cannot be readily eliminated.

Along with other initiatives, Swissair amended its MD-11 checklist for Smoke/Fumes of Unknown Origin to indicate "Land at the nearest emergency aerodrome" as the first action item. While such initiatives reduce the risk of an accident, the Board believes that more needs to be done industry-wide.

Within the aviation industry, there is an experience-based expectation that the source of odours/smoke will be discovered quickly and that troubleshooting procedures will fix the problem. Although in-flight fires like that aboard SR111 are rare, the TSB review shows that when an inflight fire continues to develop, there is a limited amount of time to land the aircraft. When odour/smoke from an unknown source occurs, the decision to initiate a diversion and prepare for a potential emergency landing must be made quickly. Therefore, the Board recommended that:

Appropriate regulatory authorities take action to ensure that industry standards reflect a philosophy that when odour/smoke from an unknown source appears in an aircraft, the most appropriate course of action is to prepare to land the aircraft expeditiously.
A00-18

Troubleshooting Time

In circumstances where the source of odour/smoke is not readily apparent, flight crews are trained to follow troubleshooting procedures, contained in checklists, to eliminate the source of smoke/fumes. An indeterminate amount of time is required to assess the impact of each action. It can take a long time to complete the checklist, including troubleshooting actions. For example, the MD-11 Smoke/Fumes of Unknown Origin checklist can take up to 30 minutes to complete. There is no regulatory direction or industry standard specifying how much time it should take to complete these checklists. Therefore, the Board recommended that:

Appropriate regulatory authorities ensure that emergency checklist procedures for the condition of odour/smoke of unknown origin be designed so as to be completed in a time frame that will minimize the possibility of an in-flight fire being ignited or sustained.
A00-19

Fire Suppression in Pressure Vessel

Current aviation requirements and standards stipulate that aircraft crews must be trained to fight in-flight fires. However, the TSB found that within the industry there is a lack of coordinated cabin and flight crew firefighting training and procedures to enable crews to quickly locate, assess, control, and suppress an in-flight fire within the fuselage of the aircraft. The Board is also concerned that aircraft crews are not trained or equipped to have ready access to spaces within the fuselage where fires have the potential to ignite and spread. The Board believes that the lack of comprehensive in-flight firefighting procedures and coordinated aircraft crew training to use these procedures constitutes a safety deficiency. Therefore, the Board recommended that:

Appropriate regulatory authorities review current in-flight firefighting standards, including procedures, training, equipment, and accessibility to spaces such as attic areas, to ensure that aircraft crews are prepared to respond immediately, effectively and in a coordinated manner to any in-flight fire.
A00-20

Responses

Transport Canada (TC), the US Federal Aviation Administration (FAA), and the UK Civil Aviation Authority (CAA) support these five firefighting recommendations. The agencies have noted that these broad-reaching recommendations will require international coordination and cooperation among regulatory authorities, aircraft manufacturers, and air operators. In October 2001, representatives from TC, the FAA, and the European Joint Aviation Authorities (JAA) met to "discuss the recommendations, to identify existing initiatives and groups that may already address some aspects covered by the recommendations, and to establish a team to develop an appropriate action strategy." The TSB will closely monitor the progress of these joint deliberations. The FAA has added the TSB's recommendations to its Safety Recommendation Program, and the CAA has taken several steps in support of the recommendations.

It is apparent that TC and the FAA agree with the thrust of the deficiencies and are committed, at least in the short term, to examine these issues and map out a course of action. Collectively, their responses are adequate and constitute a logical first step. Until such time as the details of the proposed action plan are known, it will remain unclear the extent to which the identified deficiencies will be reduced or eliminated. Since these declared initiatives will not yield any substantive change, the responses are considered to show satisfactory intent.

Stay Tuned

The TSB has also identified deficiencies and made recommendations concerning aircraft material flammability standards. Details will appear in our next issue.

Aviation Occurrence Statistics

		2001	2000	1999	1996-2000 Average
Canadian-Registered Aircraft Accidents*		295	319	341	349
Aeroplanes Involved**		242	257	287	286
Airliners		5	9	6	8
Commuters		8	4	13	10
Air Taxis / Aerial Work		55	64	89	101
Private/Corporate/State/Other		174	180	171	166
Helicopters Involved		47	53	45	54
Other Aircraft Involved***		9	12	15	13
Hours Flown (thousands)****		3 860	4 260	4 100	3 942
Accident Rate (per 100 000 hours)		7.6	7.5	8.3	9.2
Fatal Accidents		33	38	34	37
Aeroplanes Involved		25	26	28	28
Airliners		0	1	1	1
Commuters		1	1	2	1
Air Taxis / Aerial Work		6	5	6	9
Private/Corporate/State/Other		18	19	19	18
Helicopters Involved		6	11	4	7
Other Aircraft Involved		3	1	4	2
Fatalities		61	65	65	71
Serious Injuries		37	53	42	50
Canadian-Registered Ultralight Aircraft Accidents		35	38	35	39
Fatal Accidents		6	5	12	7
Fatalities		7	9	19	10
Serious Injuries		8	10	7	8
Foreign-Registered Aircraft Accidents in Canada		29	21	24	21
Fatal Accidents		8	8	6	6
Fatalities		10	19	9	58
Serious Injuries		5	3	1	3
All Aircraft: Reportable Incidents		853	730	705	725
Collision / Risk of Collision / Loss of Separation		222	169	176	190
Declared Emergency		254	227	209	212
Engine Failure		176	164	157	163
Smoke/Fire		108	84	86	84
Other		93	86	77	75

• * Ultralight aircraft excluded.
• ** As some accidents may involve multiple aircraft, the number of aircraft involved may not sum to the number of accidents.
• *** Includes gliders, balloons, and gyrocopters.
• **** Source: Transport Canada. (Hours flown are estimated.)

Figures are preliminary as of 08 January 2002. All five-year averages have been rounded.

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