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Landing Gear Problems: Guidance for Flight Crews
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Undercarriage Problems – Guidance for Flight Crew
| Article Information | ||
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| Category: | Emergency & Contingency | 
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| Content source: | SKYbrary | 
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| Content control: | EUROCONTROL | 
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Contents |
Description
Flight crews encountering problems with the operation of landing gear must follow the appropriate EICAS or ECAM procedure, Emergency or Abnormal Checklist (EAC)/Quick Reference Handbook (QRH), Operations Manual and Aeroplane Flight Manual (AFM) direction and guidance for the resolution of problems and the safe conduct of the flight.
This article covers some of the airmanship considerations associated with landing gear problems which may need to be considered in the development of company procedures or as guidance to supplement existing procedures.
Problem Identification
- Consider any unusual occurrences prior to manifestation of the problem, for example an unusual noise or slow movement of landing gear on a previous sector. Is there any previous history of gear malfunctions in the aircraft Technical Log? If so, establish whether a rectification or "no fault found" was recorded - the latter may indicate an intermittent fault.
- When surface temperatures are low enough for frozen deposits to be present, consider whether the mechanisms might have become frozen during flight as a result of prior extended taxiing through slush or wet snow? Flight above the freezing level for prolonged periods may result in the landing gear becoming frozen in the retracted position. This is less of a problem on most modern commercial transport aircraft, where the gear bays are largely enclosed by doors unless retraction/extension is in progress, but is a relatively common occurrence on aircraft such as the C130. If it is suspected that taxiing through slush or wet snow may have led to deposits adhering to the landing gear assemblies, then it may be advisable to cycle the gear after initial post take off retraction to try and shed any deposits.
- In an environment characterised by high levels of dust or fine sand, especially if the aircraft is not regularly exposed to it, consider if the landing gear mechanism may be jammed as a result of insufficient lubrication and contamination by sand and dust.
Management of Aircraft Systems
Resolution of landing gear problems can involve the disabling of features that control the configuration of other systems, for example a proximity switch on a landing gear leg that will signal whether a system should be in ground mode or air mode. Such consequential matters need to be understood and properly briefed at appropriate stages of a flight where they are likely to have an effect.
Landing with Gear in an Abnormal Position
Since there are usually three ways to get landing gear down, the normal system., an alternate system and a frefall option, it is essential to try all of these before preparing to land with abnormal gear status i.e. with ione or more legs indicating not locked down.
If the problem is affecting one set of main landing gear only, consider that it may be safer to land with all the other main gear retracted. The appropriate instructions should be in the AFM or Operations Manual.
If the problem relates to the nose landing gear only, consider how the nose might be held off the ground for as long as possible on the landing run. If practicable, shift the centre of gravity aft (within the allowable limits for landing) by repositioning passengers or freight. Do not arm the autobrakes and use wheel brakes in a manner compatible with elevator authority. Lower nose smoothly onto the runway before elevator authority is finally lost.
In all cases when landing with abnormal gear, use reverse thrust only in accordance with the manufacturer’s guidelines. Note that the applicable QRH drill may advise shutdown of some engines prior to landing, or shutdown of all or some of the engines at touchdown or at some point during the landing roll out. Engines should always be shut down before the propeller or the engine pod makes contact with the runway and must be shut down when the aircraft comes to rest prior to ordering an evacuation.
In the past, a low level ‘flypast’ has sometimes been flown to allow persons on the ground to inspect the landing gear. Whilst in certain circumstances, and if the inspection is made by appropriately qualified technical personnel, this can be valuable, it is a pointless exercise if merely seeking to establish whether one or more landing gear legs are ‘down’ since the main issue is not usually whether they are down but whether they are locked down, which cannot be reliably determined by persons on the ground whether qualified or not. The ‘flypast’ option is proscribed or severely qualified in many Operations Manuals because it is not covered in training and would constitute an unmitigated heightened risk in most SMS.
Planned flight with Landing Gear in the Down Position
Such a flight must only be undertaken in accordance with the procedures and limitations in the AFM or Operations Manual. It will usually also require the express approval of the Flight Operations Department of the Aircraft Operator as well as appropriate entries in the Aircraft Technical Log which allow the aircraft to be released to service. Depending upon aircraft type, pre-flight preparation may include maintenance action to remove some gear doors or making specific switch selections in the avionics compartment.
Limitations on speed may affect other airspace users and result in exclusion from certain airspace and higher flight levels. Check with the air navigation service provider (ANSP) and ensure that a new or amended Flight Plan (FPL) is filed which clearly indicates any performance restrictions.
Whether the flight with gear down is planned, or occurs as a result of a decision to continue a flight following a failure to lock landing gear up after take off, the following need to be considered:
Flight Planning Considerations
- Structural Considerations: Flight with the gear down is likely to involve limitations on both indicated airspeed and cruising altitude.
- ATC Issues: ATC will need to be advised of any reduced cruise speed and maximum altitude unless these if these will mean that the figures filed in the FPL are no longer applicable.
- Flight Time: Consider the impact of reduced speed on flight times and expected arrival time at the potentially revised destination and alternates - will they be open? Is new en route wind velocity data needed? Consider whether previous performance calculations are still valid at the reduced cruising speed, for example engine out terrain clearance requirements, or ETOPS.
- Fuel Planning: Increased drag, and flight at lower than normal cruising levels, will result in a significantly higher fuel burn. It may be necessary to make a refuelling stop en-route if it is still intended to continue to the destination. Note that some FMS will not give reliable fuel predictions in such a situation.
- Flight in Icing Conditions. Flight in icing conditions should usually be avoided because any build up of frozen deposits on the extended undercarriage will increase drag and aircraft weight and may also affect the centre of gravity. It should be noted that at a slower speed, ice accretion on the airframe may occur at an increased rate.
Accident and Incident Reports
- A310, Vienna Austria, 2000 (LOC HF AW): On 12 July 2000, an Airbus A310 being operated by Hapag Lloyd on a non scheduled passenger flight from Chania to Hannover declared an emergency due to fuel shortage and, after making an en route diversion to Vienna in day VMC, crash landed short of runway 34.