OT Safety Bulletin

Use of Brakes in Light Aeroplanes

Introduction

This is issued to remind operators and pilots of the importance of using appropriate braking techniques in light aeroplanes.

Applicability

Aircraft Operators are asked to ensure that this information is made available to their ‘in house’ or contracted maintenance organisation, to relevant outside contractors, and to all members of their staff who could have an interest in the information or who need to take appropriate action.

Discussion

Brakes absorb kinetic energy by heating up. As they heat up, they lose effectiveness, so the pilot may then use them more harshly and for longer periods, which in turn increases the heating. Whilst brake pad wear is to be expected in normal use, poor operating techniques may cause increased wear and failure of other brake components. Overheating or component failure could make the brakes totally ineffective when most needed, leading to the risk of an accident.

Problems can result from approaches being flown inaccurately – e.g. at the wrong speeds. The speeds specified in the flight manual (Vref and/or Vat) should allow a pilot to cope with most situations. Approaching too fast increases the landing distance – kinetic energy is proportional to the square of speed. If the speed is reduced by floating, the touchdown point moves further along the runway. If the aircraft is flown onto the runway at the higher speed, the brakes must absorb that energy after landing, and the landing run will be considerably increased.

A late decision to go-around also involves risks, so it is important that operations manuals include appropriate stabilised approach parameters, and these must be emphasised during flight crew training and competency checking.

Be alert for the significance of anything that seems unusual. For example, if extra power seems to be needed during taxiing, consider whether the brakes may be binding. That could result in a lack of acceleration on take-off.

It is also important to know and understand the aircraft systems. For example, in some types there may be a need to check the fluid level in the brake cylinders before flight. In some aircraft a single hydraulic system is used for the brakes and the undercarriage and/or trim systems, so any loss of hydraulic pressure may have braking implications.

Incorrect operating techniques can cause damage in less obvious ways. In one case fatigue damage to the nose gear assembly is believed to have originated from shock loads transmitted by use of a hand operated tug used for routine ground handling. It is important to ensure that the aircraft brakes have been released before any ground movement, because attempting to move a braked aircraft may cause such shock loads.

Some important reminders

• Checklists help to ensure that essential items are not overlooked.
• Make certain that brakes are applied (and lookout) before starting engines.
• Always be ready to close the throttle and/or steer towards the area of minimum danger if the brakes seem ineffective.
• Do not ride the brakes while taxiing.
• Be careful with tight turns and avoid excessive use of power and brakes together.
• Make sure brakes are not inadvertently applied (e.g. heels on the floor) when taking off.
• Pay attention to stabilised approach parameters.
• Aim to touch down at the correct speed in the touchdown area, and let the aircraft roll out and decelerate normally, using brakes as appropriate to the runway remaining and other conditions.
• Make proper allowances for wet and contaminated (or damp) runways and understand the techniques to prevent aquaplaning as appropriate to your aircraft type (see note).
• Use the brakes appropriately, e.g. on long runways use gentle pressure in short bursts.

Note: For example in aircraft without automatic braking systems (ABS) it may help to release the brakes before reapplying them gently, perhaps doing this several times until they grip.

Recommendation

Operators should review the content of their training and competency checking programmes, and ensure that appropriate stabilised approach parameters are included in their operations manuals (see Appendix 1 to OTAR Part 121.1250 / 135.1250 Part B Aircraft Operating Matters, paragraph 2.1).

Queries

Any queries should be sent to: enquiries@airsafety.aero.