David Learmount/LONDON
The CIRCUMSTANCES of the" British Airtours disaster at Manchester in August 1985 led the UK Civil Aviation Authority to investigate the installation of external aircraft-surveillance video cameras. About a decade later, a review of CAA tests was published, revealing that the authority does not consider cameras a necessary safety tool, and that at present it has no plans to require their installation.
Meanwhile, one of the specialist companies which took part in the tests believes that the future of external video cameras on aircraft lies, not in safety applications, but in the area of in-flight entertainment. This is not what the world had been expecting to hear. In the Manchester accident, although the aircraft never left the ground and did not collide with anything, 55 people died, mostly from asphyxiation from noxious fumes. The fire had started when the Boeing 737-200's number one engine exploded. A combustion chamber had failed, and a piece of shrapnel from the explosion pierced a wing-fuel tank. The crew, unaware of the severity of the fire because they could not see the engine or wing, abandoned take-off but did not halt on the runway and order immediate evacuation. The captain decided to leave the runway before stopping, putting the burning wing upwind of the fuselage. The fire spread fast to the fuselage, and the rest is history.
One of the first questions to emerge from the incident was: if the crew had been able to see easily how severe the fire was, would they have arranged emergency evacuation of the aircraft faster? The answer is almost certainly "yes".
In January 1989, in another UK accident, a fan blade on a 737-400's engine failed. There was a burst of flame from the engine, seen by many of the passengers. The powerplant, however, did not catch fire and, because the crew immediately throttled both engines back to idle to descend quickly to East Midlands Airport, many of the symptoms of the fan-blade failure disappeared. The result was that the crew shut down the undamaged engine, while the damaged one failed on final approach, and the aircraft crashed short of the airport.
If there had been a screen on the flightdeck displaying the view of the aircraft from a "fish-eye" video camera on the tail fin, would the pilots have seen the flame which the passengers saw? If they had, 47 lives might have been saved.
THE TESTS
The CAA installed three external video cameras on a British Airways Boeing 747-100. A camera on the tail fin viewed the starboard wing; one on the port tailplane viewed the port-wing trailing edge; and a camera with a panning capability was mounted on the forward underbelly. This could scan an arc with the inboard engine intakes at either extremity, and it covered all the main landing gear.
The BA test was set up for engineering purposes. There was no display in the flightdeck, but the camera displays could be viewed at a point in the upper cabin, and a video-recording system was installed there.
Even though the Vinten surveillance equipment had not been made with an aviation application in mind, the CAA says: "In general, the cameras operated satisfactorily in all the meteorological and atmospheric conditions experienced." Observers made the following points:
"-the system produced no usable pictures after dusk. Even on a brightly lit apron, it was not possible to discern details of the airframe";
"-no particular benefits of colour pictures over monochrome were discerned, especially at altitude". In fact, monochrome produced better clarity, which outweighed any advantage of a colour picture;
- the underbelly camera was prone to misting, and to the effects of rain and spray;
- the iris control could not cope with the large brightness variations which occur in flight;
- recorded pictures were of inferior quality to real-time ones.
The CAA notes, however, that many problems might be overcome by the use of specifically designed equipment, warning that "-the problems of night viewing are still a major problem to the realisation of a practical system".
The human-factors (HF) side of the external-surveillance test was carried out by the UK Defence Research Agency (DRA) at Farnborough. The DRA's first concern was where to put a display which would be useful to the pilots. There is not much room in flightdecks, it concludes, and the display's tendency to distract as well as to inform has to be taken into account.
The CAA's report summarises the DRA's views: "It is likely that some events which the crew may find useful to view using external cameras may be transitory in nature. It is unlikely, therefore, that the crew will be looking at the appropriate part of the airframe at the exact time at which the event occurs. It would be very useful to have the ability to play back recordings of the views from all cameras at a later time. However, there are difficulties associated with finding the appropriate piece of recording in a useful time-frame using conventional videotape recording techniques.
"Adequate labelling of the view being shown, time of recording and the facility for inserting event-markers would be needed. The use of such a replay system needs to be given an operational status. The search for the relevant incident could become as absorbing as the pictures themselves, to the detriment of the operation." Ultimately, the DRA says, the system needed extensive evaluation in a simulator to assess the many HF pitfalls it could anticipate.
The CAA's safety-benefit study looked at a wide range of fatal accidents, and finally narrowed them down into categories where external viewing might have helped if the equipment could have shown enough detail, at the time it was required, to be of use. These were:
- ground operations;
- ice/snow accretion on aircraft;
- incorrectly configured landing gear or flaps/ slats;
- engine fire/failure;
- during emergency evacuation.
The CAA says that in all the cases where internal fire was the killer, the situation would have been "catastrophic" before any information would have been apparent externally.
The CAA also says that ground-operations ramp accidents were more effectively dealt with by the implementation of stricter ramp-safety procedures, which the airlines are addressing. For the ice/snow situation, it concludes that video cameras are of little help in detecting ice even in good lighting, but might help for snow. In the case of incorrectly configured landing gear or flaps, the CAA judges that all the information which the crew needs is already provided, especially in modern aircraft which also embody configuration-warning systems.
For the engine-fire/failure situation, the CAA has looked at the Manchester case and observes: "To be able to benefit from an external viewing system the crew would have had to:
- assess the nature of the problem;
- decide whether to reject or continue take-off;
- decide where to bring the aircraft to a halt;
- instruct the cabin crew on the appropriate exits for evacuation."
The CAA report continues: "To perform all of these functions, a camera system would have had to be active during the take-off run. This is not favoured by the CAA since it can be a source of distraction at a critical stage of flight. The use of a camera must also be put in the context of a time-frame in which the whole accident occurred and other events which took place in parallel. The benefits are dubious."
About the January 1989 East Midlands (Kegworth) accident, the CAA observes that "-there was adequate information to indicate which engine was malfunctioning. The crew misinterpreted this information. Had they had the benefit of CCTV [closed-circuit television], it is questionable whether they would have changed this view on receipt of contrary information, even from external view, unless there was an element of doubt in their minds. There is no evidence from the accident report that any such doubt existed." The flame which had been emitted from the engine upon shedding a blade-tip was short-lived and was eliminated when the crew put the engines to idle. Visual detection by the pilots would have depended upon whether they were looking at the correct display at the time that the transient event occurred.
The CAA has decided not to make external video-camera surveillance mandatory, but will not prevent airlines from fitting equipment. It has recommended that the European Joint Aviation Authorities take the same line, and they have done so. Any airline which wants to operate a flightdeck display, however, would have to go to the CAA for its certification, and satisfy the authority that the disadvantages are not dominant. The disadvantages described by the CAA are:
- crew distraction during critical flight phases ;
- distraction from laid-down emergency procedures and priorities;
- incorrect diagnoses;
- information overload; and
- incorrect camera identification.
THE AIRLINE USERS
BA, which carried out the 747 CCTV testing for the CAA, says that it has completed the tests and decided not to use the system voluntarily, even though the CAA had wired the aircraft up to allow a flightdeck display to be fitted if the test had, in the CAA's view, been positive. BA also says that it has considered the idea of using an external viewing system as part of the inflight-entertainment system, but has rejected the idea for the time being.
DM Aerospace, however, which manufactures solid-state systems specifically tailored for aircraft use, has installed its Flight Vu system in a private Gulfstream IV, with a camera high on the fin and one on the underbelly. Technical sales manager of DM Aerospace, Mike Horne, explains: "The owner just wanted it."
The views gained are wired into the entertainment video recorders for the passengers to watch. Dubai-based Emirates has an underbelly system which the passengers can choose to view. This however, shows just the taxiway/runway centreline markings or lights passing by at varying rates during ground movement, and the first useful sight is when the aircraft starts to climb and the ground is seen to "fall away".
There are other areas, however, which Horne thinks are the most commercially promising and can offer most benefit to the industry, but they are internal cameras, not external ones. Flightdeck-recorded film of what the pilots actually see on the electronic flight instrument system (EFIS) displays is one. This can enable pilots to explain why they carried out certain actions which were later questioned, because what the aircraft does may be recorded on the flight-data recorder, but what the EFIS shows the pilots is not. This use of flightdeck cameras could also provide fertile HF data, in terms of how pilots react to integrated-display information.
There would be an option to film the whole flightdeck, taking in the crew's actions. The International Federation of Airline Pilots Associations says that it does not want the latter, but would welcome filming of the EFIS.
Horne points out another use for flightdeck cameras which he sees as promising. There has never, he maintains, been an "-economical way of recording what goes on in a general-aviation aeroplane. One thing we're thinking about is a cheap means-of data-feedback to accident investigators". Cheap, Horne says, is $2,000 per aeroplane, but DM hopes to bring that down to $1,000.
Horne does not think that external cameras for safety are the answer, saying: "There's almost always another way of finding out what's wrong." Of the Manchester case he says: "Screaming down the runway with an engine on fire, you're not going to look at a TV screen."
That, however, is not the end of the potential market for external video, Horne believes. Airlines are showing an interest in the idea of downward-looking cameras, perhaps showing the aircraft or a part of it, which can provide pictures of the terrain over which it is flying. The idea is to combine that view with a moving-map display as a part of a passenger-entertainment/ information system.
Meanwhile, Horne says: "The first pitch is to the executive-jet market, because customers there are easier to convince."
Source: Flight International
