Something’s ‘not right’ with one of your instruments or gauges on the panel. Do you immediately make a forced landing, or find the closest safe airfield to land at, or deal with it when you land at your planned destination?
The right answer is – it depends.
The best course of action will be different when your oil pressure drops, to when the alternator light comes on, to when you have altimeter or suction issues. Not understanding what an alert or failure means – and therefore what you really should do – sets you up for stress, leading to poor aeronautical decision-making and potentially a worse situation.
A recent aircraft accident investigation in the United States demonstrates extremely well the risk of poor decision-making after an instrument failure:
In December 2024, after suffering an in-flight electrical failure with subsequent loss of avionics, navigational aids and flap, a Grumman AA-5 attempting to land collided with a Cessna 182 that was exiting the runway. The Grumman pilot had believed he had to ‘get the airplane on the ground as soon as possible – and at all costs.’ The US National Transportation Safety Board concluded ‘the AA-5 pilot’s poor judgment’ contributed to the collision. (NTSB accident number CEN25LA059)
Systems knowledge
Systems knowledge means thoroughly understanding how the aircraft’s systems work and interact. These include electrical, mechanical, fuel, hydraulic, avionics, pitot-static, gyro, and other systems. This knowledge helps keep you ‘in front of the aircraft’ and is key to making calm, rational aeronautical decisions under pressure.
A good start to a thorough systems knowledge is to understand the instrument panel:
- what the indications mean or measure
- how to detect instrument failure
- knowing what happens to performance if an instrument fails
- understanding instrument interaction or interconnection
- understanding which instruments are electrically powered
- which instruments are driven by other means
- which instruments can fail instantly, or fail slowly
- knowing what your immediate aviation action should be in the event of an alert, failure or suspected failure.
Possible vs practicable
In a single-engine piston aircraft, if your engine or propeller fails completely, the key decision has been made for you – land now.
Scenarios:
Land as soon as possible: the airworthiness of the aircraft is at risk, therefore land at the nearest suitable landing site (be that paddock or airfield).
Land as soon as practicable: find the nearest safe airfield to land at, while continuing to monitor for a worsening situation that might mean you need to land as soon as possible instead.
Deciding the appropriate action can be assisted by aeronautical decisionmaking tools, such as DECIDE:
D – detect the threat
E – estimate the threat
C – choose a safe outcome
I – identify options
D – do (execute the plan)
E – evaluate (the execution of the plan)
Every in-flight scenario is unique. Only the pilot in command will know all the factors that may inform the decision.
Chad Summers, who has been flying for more than 18 years, is New England Aviation’s chief flying instructor based in Tamworth, and a licensed aircraft maintenance engineer.
‘The difference between possible and practicable is in the severity or time-sensitivity of the problem,’ Summers says. ‘If the aircraft appears to fly normally with no indication of engine trouble, there may be no need to put it down in a paddock; it’s not necessarily a right-now emergency.
‘However, it may also be a worsening condition. Even if you have already made the decision to divert and land as soon as practicable, you still need to be prepared to make a decision to put it down immediately.
‘With electrical systems, it could be benign, but it also may be a wire shorting that could lead to an electrical fire. Don’t panic but also don’t be complacent with electrical problems.’
Fly the aircraft
Many instrument warnings or failures aren’t as time critical as engine temperature or pressure problems, and many aircraft also have redundancy instruments. Some aircraft, for example, have a secondary static pressure source which can be turned on in case of a primary static failure. Know these before you go and remember to crosscheck them in an instrument alert or failure scenario.
If the engine, flight controls and propeller continue to operate normally, your aircraft is ‘flyable’. Keep the normal in ‘abnormal’, manage your workload and continue to follow checklists and procedures.
‘All pilots should be flying in reference to power + attitude = performance,’ Summers says. ‘As long as you have power (engine) and can control pitch and bank (stick and rudder), your aeroplane should still fly.
And it’s possible to land an aircraft without an airspeed indicator and an airspeed altimeter. As long as you have an idea of your engine performance – RPM, throttle setting, sound – and attitude, you can get it pretty right.
‘This is something you might practise, but only with a check pilot or instructor,’ he says. ‘Hide the airspeed indicator and attitude indicator and try flying and setting up for landing.’
In the accident mentioned earlier, the Grumman AA-5 pilot told the NTSB he allowed the failure of the aircraft’s electrical system to influence his decision to land as soon as possible and ‘at all costs’. Sure, you may want to be on the ground if your in-flight computer goes dark, but the aircraft still had power and attitude control.
Different systems
Consult your pilot operating handbook and discuss with your aircraft’s LAME and your instructor before deciding what your potential actions might be given various different scenarios.
‘Only the pilot in command of an aircraft can know the full extent of an in-flight situation,’ Summers says. ‘And only a pilot with a thorough systems knowledge of that aircraft can make informed decisions’.
‘Always expect that things could definitely get worse, without panicking. That mindset will keep you safe.’
Know your aircraft, know your systems, know your pilot operating handbook and may your Ts and Ps always be green.
