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Brake Problems: Guidance for Controllers
From SKYbrary Wiki
There is no set of ready out-of-the-box rules to be followed universally. As with any unusual or emergency situation, controllers should exercise their best judgment and expertise when dealing with the apparent consequences of a brake related problems and the possible outcomes. A generic checklist for handling unusual situations is readily available from EUROCONTROL but it is not intended to be exhaustive and is best used in conjunction with local ATC procedures.
This article provides guidance for tower/approach controllers on what to expect from an aircraft experiencing the effects of a brake problems and some of the considerations which will enable the controller, not only to provide as much support as possible to the aircraft concerned, but also maintain the safety of other aircraft at or in the vicinity of an aerodrome and of the ATC service provision in general.
Useful to Know
Malfunctions or human errors related to application of brakes on landing and during taxi have been the cause of numerous accidents and incidents (See A&SI in Related Articles and Further Reading). Distraction, preoccupation and technical malfunction during the landing sequence play a prominent role in many occurrences which result in overheated brakes and brake failures which subsequently involve increased levels of risk related to deceleration and directional control.
There are various configurations of brake equipped undercarriage or main landing gear. Aircraft brakes are located on the main wheels and are usually selected by either a hand control or by foot pedals. On most modern transport aircraft autobrake and anti-skid systems are provided. (For more information, see the dedicated article on aircraft brakes in SKYbrary.)
Because brake and antiskid failures are often a direct consequence from hydraulics related problems or faults in associated electrical/electronic control units, the flight crew can become aware of the emerging brake malfunction very early into the flight. These systems are normally not needed during the cruise phase and because of that, the problem may remain unpronounced for ATC until the begging of approach.
Listed are some braking and deceleration issues that directly affect the aircraft performance:
- Overheated brakes - The kinetic energy lost by slowing an aircraft down is usually translated into heat by friction and could result in:
- Loss of braking performance
- Tyre deflation / tyre burst
Brake failure and subsequent poor directional control and deceleration in turn could result in:
- Runway excursion
- Uncommanded aircraft ground movements / taxiway excursion
- Collision with objects on the ground/other aircraft
Anticipated Impact on Crew
A wide range of practical problems could arise following brake related problems:
- High level of stress and increased workload - caused by directional control and deceleration problems resulting from brake failure during landing, or during high speed rejected take off (RTO);
- Lack of awareness - Crew might be not aware of fire, tyre burst or deflation that could result from heavy braking upon landing, RTO, or from smoke coming from the undercarriage;
- Request fire and rescue services - hot brake incidents could be considered by the crew a reason to request attendance of fire and rescue;
- Decision for emergency evacuation - the cockpit crew could take the decision for emergency evacuation if fire is detected following a high energy brake application
Suggested Controller’s Actions
What to Expect
As a controller, expect:
- Pilots, if aware prior landing of the brake problem, to request:
- the longest runway available;
- the widest runway available whenever directional control problems on the ground are anticipated;
- to execute holding procedures to burn fuel and minimise weight;
- to divert to alternate aerodrome if conditions such as poor braking action, runway contamination, adverse weather is present at the destination aerodrome or any other conditions that could result in higher ground speed on touchdown or are unfavorable for taxi with effective brake malfunctions;
- to divert to alternate aerodrome depending on availability of maintenance personnel and respective technical facilities should the airplane need repair.
- Aircraft overrunning runway threshold at far end (stop end);
- Aircraft swerving off the runway;
- Tyre burst* and associated damage to the aircraft - inform the aircraft crew and the airport fire rescue services if a burst tyre was observed;
- Blocked runway after landing - plan ahead regarding pending departures and arrivals, possibly sequencing them for other runways if available.
What to Provide
Best practice embedded in the ASSIST principle could be followed (A - Acknowledge; S - Separate, S - Silence; I - Inform, S - Support, T - Time):
- A - acknowledge the emergency, inform if fire/smoke is observed from the undercarriage area;
- S - separate the aircraft and if necessary prioritise it for landing, allow long final if requested, keep the active runway clear of departures, arrivals and vehicles;
- S - silence the non-urgent calls (as required) and use separate frequency where possible;
- I - inform the airport emergency fire rescue services and all concerned parties according to local procedures; as tower controller expect airport authorities to execute their emergency plan; inform the supervisor and other sectors/units concerned;
- S - support the flight by providing any information requested and necessary such as type of approach, runway length and aerodrome details, etc.
- T - provide time for the crew to assess the situation, don’t press with non urgent matters.
When informed about possible/actual brake problems for aircraft inbound to land, be ready to:
- Inform pilot about runway length and condition;
- When aircraft on final do not allow poor positioning for the approach, monitor carefully alignment, height, speed, distance from touchdown;
- Keep safety strip clear;
- Plan ahead the pending traffic, consider assigning priority to the arrivals if necessary due to possibility of blocked runway;
- Make arrangements for towing equipment to be on stand-by as appropriate;
- Request help of technical staff required to inspect and assess the damage to the aircraft as appropriate;
- If pilot reports vibrations during the take-off/landing roll - consider possible tyre burst/debris on the runway and make the necessary arrangements for runway inspection. Inform the pilot if tyre burst has occurred, especially important if it took place after take-off.
Additionally, as a ground controller consider coordinating where to position on the ground an aircraft that requires a prolonged brake cooling period following a hot brake incident to minimise the disruption to other traffic.
- Burst tyre - Even though modern aircraft rely on a number of defences to prevent tyre burst (e.g. nitrogen inflation, anti-overheat thermal fuses), such incidents are not uncommon. The burst tyre incidents are associated with various circumstances, brake related problems are also among them.
The explosive tyre burst could inflict serious structural damage with associated consequences such as fuel leaks (see CONC, vicinity Paris Charles de Gaulle France, 2000 (AW GND FIRE LOC)), even cause explosive engine failure due ingestion of tyre debris.
- Landing Distances,
- Runway End Safety Area,
- Landing on Contaminated Runways,
- EASA Runway Excursion Statistics, August 2008
- Swearingen SA226, FIRE LOC, Montreal Canada, 1998: On 18 June 1998, a Fairchild-Swearingen Metro II, crashed at Montreal Canada following a fire in the wheel well, caused by overheating of the brakes, which developed until the left wing failed rendering the aircraft uncontrollable.
- Guidelines for Controller Training in the Handling of Unusual/Emergency Situations, EUROCONTROL
- Airbus Landing Techniques Briefing Note - Bounce Recovery - Rejected Landing
- Extract from AAIB Bulletin No. 1/2007: incident involving A320 which suffered a hydraulic failure and subsequently collided with an airbridge because the crew did not appreciate the implications of the failure on the braking system.
- Extract from AAIB Bulletin No. 2/2005: incident concerning failure of aircraft braking system on landing.
- Extract from AAIB Bulletin No. 1/2007: brake fire incident involving a Robin R1180T.