50 Years After Munich

The Briefing Room - Learning from Experience 50 YEARS AFTER MUNICH On 6 February 1958, Manchester notice”. Captain Thain was held to be taxiing has commenced, there will be United football team were returning responsible, his airline transport pilot’s difficulty maintaining directional home to England after a European Cup licence was taken away and he was control if the taxiway is contaminated; match against Red Star Belgrade. They dismissed by BEA. It was not until 1968 braking will also be problematic. If were flying in an Airspeed Ambassador that a new British commission cleared snow or slush obscures taxiway aeroplane chartered from British Captain Thain of all blame. markings, the aircraft may take a wrong European Airways (BEA) and captained turning or proceed further than the by Captain James Thain. The aircraft Understanding of the effects of ice, taxi clearance allows. Snow, ice or slush stopped to refuel at Munich, where the slow and slush contamination on run- may be thrown up from the taxiway by runway was covered with slush. ways and taxiways, and also on aircraft the blast from the engines or by the in the air, has increased enormously mere passage of the tyres through the Captain Thain tried to take off twice, over the last 50 years; but we still do contaminant; this may damage aircraft but both attempts were aborted due to not know all the answers. The reality is components or contaminate the air- engine surging. When a third take-off that the presence of ice, snow or slush craft itself. was attempted, the aircraft did not anywhere near an aeroplane must be accelerate sufficiently, and after take- regarded as a serious safety hazard and Take-off from a contaminated runway off it failed to gain adequate height. It treated accordingly. poses additional hazards. The presence crashed into the fence surrounding the of even a very thin film of snow or airport and then into a house. The left There are two main areas of concern: slush on the runway will reduce wing and part of the tail was torn off. acceleration, delaying the time taken to The house caught fire. The left side of Runway and taxiway reach take-off speed. Maintaining the cockpit hit a tree. The right side of contamination; and, directional control using nose-wheel the fuselage hit a wooden hut, inside steering alone may be difficult, which was a truck filled with tyres and Ice on a parked or taxiing aircraft. especially in the presence of a cross- fuel, which exploded. wind. If the take-off has to be RUNWAY AND TAXIWAY abandoned, then the effectiveness of 23 of the 44 passengers and crew on CONTAMINATION the aircraft brakes will be greatly board died, either at the time or shortly The hazards associated with an aircraft reduced. Finally, contamination of the afterwards. These included 8 members parked on an icy stand are fairly underside of the aircraft, especially the of the football team, as well as the co- obvious. Engineers, ground crew and landing gear and wing flaps, by spray pilot, a steward and 8 journalists. Of the flight crew run the risk of falling and thrown up from the runway will be 9 surviving team members, two never injuring themselves. Vehicles unable to hard to avoid. played again. This accident has entered stop may crash into the aircraft. When the folklore of British football as “The engines are started, the aircraft may Once in the air the problems are not Munich Air Disaster” and is an example slide from its parked position even if over. If the aircraft has been of aircraft accident prevention - and the brakes are applied and may push contaminated by spray from the taxi- investigation - of which we cannot be the wheel chocks out of the way. The way or runway then its aerodynamic proud. push-back, too, will be dangerous due properties will have changed, to poor adhesion between the tug’s increasing drag and reducing lift. Snow In his book, The Naked Pilot6, David wheels and the tarmac. or slush thrown up onto the landing Beaty states that the Canadian gear or flaps will not necessarily authorities and KLM were aware of the Taxiway contamination is not prevent retraction, but it will probably problems associated with slush- systematically assessed in the same freeze in flight and may prevent covered runways but “BEA took no way as for runway condition. Once subsequent extension. Recommended 6 The Naked Pilot by David Beaty, first published by Methuen in 1991. HINDSIGHT N°7 Page 39 July 2008 The Briefing Room - Learning from Experience practice these days is to recycle the landing gear several times before final retraction to shed as much contamination as possible. Contamination of sensors, for example, the pitot head or static vents, will result in erroneous information being fed to aircraft instruments and to the different aircraft systems that rely on their output. When it comes to landing, the main problem will be maintaining directional control and stopping before the end is reached. Other than that, similar hazards to those listed above will be present, although there will of course be an opportunity to clean away any contamination once the aircraft has parked. may cause quite rapid changes to run- ICE ON PARKED OR TAXIING way conditions. Braking action on AIRCRAFT If operations are to be maintained snow and slush can be measured fairly Ice or other contamination on parked while snow is falling, frequent checks accurately; at present water aircraft can have two main effects: it must be made of all paved surfaces contamination cannot. may alter the aerodynamic properties and any adjacent areas over which of the aircraft and it may affect aircraft engines may pass. It will usually be Because of the hazards, some operators components. In addition to the aero- necessary to clear any fallen snow or prohibit or severely restrict operation dynamic effects, ice on control surfaces change the taxiing plan so that aircraft from contaminated runways. Where may prevent their free movement, do not have to use contaminated areas. they are permitted, the pilot will need while wet contamination may freeze If drains are not kept clear, then to know the depth and type of after take-off preventing normal oper- pooling water melting from the paved contaminant as well as the braking ation. Landing gear and flap surface may pose as big a problem as action, for use in making performance contamination has already been snow or ice contamination. calculations. It is essential that the mentioned. assessment of runway conditions is At aerodromes where snow is present accurate at the time of operations as Contamination of the pitot-static for a large part of the year, the use of take-off or landing performance may system is a particular problem if covers ice or compacted dry snow (gritted or be marginal. have been left off the sensors for some ungritted) may be authorised, in which time while precipitation is in progress. case special conditions will apply and Pilots must be notified immediately if Moisture may enter vents and freeze, must be rigorously applied. conditions deteriorate, even if infor- causing blockage and erroneous mation provided is provisional while a readings. Runway inspections must be supple- detailed assessment of conditions is mented by frequent checks of braking being conducted. Clearing ice and snow from parked air- action; this is particularly important in craft is a specialist task. First, loose the presence of precipitation, which snow is brushed from the wings and July 2008 Page 40 HINDSIGHT N°7 The Briefing Room - Learning from Experience fuselage, then the aircraft is treated the take-off run, the fluid is shed from CONCLUSION using a spray of de- and anti-icing the wings and other surfaces so that its fluids (sometimes heated). Holdover presence does not affect the aero- Although we have come a long way protection is achieved by a layer of dynamic performance in flight. At since 1958 in our understanding of anti-icing fluid remaining on and some airports, de-icing is carried out at icing problems, the annual toll of protecting aeroplane surfaces for a a remote de-icing stand on the air- accidents resulting from this hazard period of time. With a one-step craft’s route to the take-off point; this demonstrates that the problem is not de-icing/anti-icing procedure, the permits the collection and ecologically yet under control. Only by continued holdover time (HOT) begins at the safe disposal of surplus fluid. application of best practice and commencement of de-icing/anti-icing. constant vigilance by all members of With a two-step procedure, the Some de-icing fluids remain on aircraft the flying team - pilots, air traffic holdover time begins at the after landing and the dried deposits controllers, meteorological forecasters, commencement of the second may collect in aerodynamically quiet engineers and airport staff - can the (anti-icing) step. The holdover protec- areas. These deposits must be washed target of zero icing-related accidents tion runs out: from aircraft with unpowered flying ever be achieved. controls as they may re-hydrate and At the commencement of take-off freeze at a later point in suitable roll (due to aerodynamic shedding environmental conditions, causing of fluid) or jamming of control surfaces. When frozen deposits start to form or accumulate on treated aero- Once taxiing of an uncontaminated air- plane surfaces, thereby indicating craft has commenced, falling snow may the loss of effectiveness of the fluid. build up on the aircraft. This is likely to become dangerous if departure is Strangely enough, there are no inter- delayed for any reason.Therefore, pilots national standards for these fluids, but should be informed immediately if in Europe, an AEA (Association of accretion is observed by controllers on European Airlines) working group taxiing aircraft; in this case, it may be carries out an annual review of necessary for the aircraft to return to available products and publishes a the de-icing bay for re-treatment.

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