Last Line of Defence - Stall Warning Devices

Flight training in order to recognise and avoid a stalls must always be the primary focus in order to maintain safe flying operations, however, as a last line of defence should you consider fitment of a stall warning or angle of attack device within your aircraft?

What is the cost of a life? $500, $2000, $10,000? When it comes to putting a price on survival, it simply cannot be done – However, in an environment where loss of control events continue to be the number 1 cause of fatal accident globally, how is it that many new aircraft are not fitted with a stall warning device?

While training should focus on ensuring pilots are capable of identifying and preventing a stall before it occurs, there are a number of situations where a pilot may end up in a stall due to distraction, or where a turn is initiated without realisation that the aircraft is rapidly approaching the point of stall. So while stall awareness training is key in minimising loss of control events, an aural or visual warning may be the last line of defence in avoiding a loss of control.

Operation type

Whilst fitment of a stall warning device may be suitable for all aircraft operations, with a majority of loss of control events occurring within the circuit, there are higher risk operations which may make fitment of a stall warning system even more critical. Examples of this may include aircraft which are used on a farm for mustering or monitoring cattle, fences or troughs. Aircraft used for low level activities, or aircraft used for flight training.

Stall warning devices

In relation to devices that warn of an approaching stall there are a number of options available. These include stall warning horns, lift detector stall warnings, the ever familiar sound of a reed horn stall warning as seen on many Cessna aircraft, and more recently, a range of angle of attack sensors that provide warning when the aircraft is approaching the critical angle of attack.

Most of these devices require a sensor to be attached to an external surface of the aircraft which is wired to an alarm or control system in the aircraft electrical system. These devices normally require fitment from a qualified engineer to ensure they are installed correctly and safely.

In addition to the above, there are new devices available offering probeless angle of attack readings combined with a suite of additional functions for pilots. One such device is the uAvionix AV-20-S or AV30 multifunction display capable of offering visual and aural angle of attack alerts as well as a range of additional functions.

Stall warning fitment

Before rushing out to purchase and install a new stall warning or angle of attack device, aircraft owners must review the requirements relevant to your aircraft type.

  • If you operate an LSA aircraft on a special certificate of airworthiness, you will require a letter from the manufacturer approving any modification made to the aircraft
  • If you have a type certified aircraft then any modification will require certification 
  • Amateur built aircraft where the owner is not the builder will require an inspection and may require flight testing.

 

RAAus recommends aircraft owners contact their aircraft manufacturer or local representative to discuss the possibility of fitting a stall warning device to your aircraft. While designed as a last line of defence, it may just be the difference between stall identification and realising too late to recover.