Medical certification – are you fit to fly in Australia?
Over the last few years the approach to assessing whether a pilot is medically fit to fly has changed. It is moving towards trying to quantify the risk of total incapacitation due to some medical emergency.
There have always been legal cases, involving senior professional air transport pilots, who objected to their company policy of retirement at age 60. Their success in the courts has heightened the need to look statistically at medical risk factors for pilots as they get older.
Medical Certification deems the most important area of concern to be the assessment of cardiac or heart disease causing the risk of sudden incapacitation, although similar models have been developed for other conditions, such as epilepsy.
Various risk factors are known to be associated with the development of heart disease. These can be quantified using a major heart disease study which is world famous for it’s detail and reliability as a long term factor program (the Framingham Study).
The chances of developing heart disease in broad terms is associated with a number of known risk factors.
- Family history
- Lack of exercise
- Raised blood pressure
- Abnormal cholesterol
The contribution of each towards an individual’s risk of heart disease can be quantified. More importantly, all but family history, age and sex can be modified by appropriate lifestyle changes.
A risk analysis model now being developed for medical emergencies equates the risk of a total pilot failure to the quality assurance standards expected of the air frame and associated engineering.
The concept involves around assessing the risk for the failure event occurring in any one particular hour.
Engineers design the aircraft, airframes and engineering to to a standard expected to achieve a serious failure (accident assured) in less than one in 109 hours (one is a thousand million hours risk).
Worldwide observed failure rates as follows:
- Multi-crew transport jets 1 in 106 hours
- Military jets 1 in 105 hours
- Charter air services 1 in 105 hours
A way of computing the risk of pilot incapacitation due to any particular medical condition is shown in this table:
Assume average flight is one hour duration.
Initially consider 100% incapacitation for the condition arising some time in a year.
Possibility of event occurring in any one hour:
One event in 24 x 365 = 8760 hours or approx. 1 in 104 (one in 10,000). If pilot flies 600 hours per year, the chance of incapacity being a flying hour is:
600/8760 or approximately one in 10.
Probability of being incapacitated in that single flying hour is:
104 x 10 = approximately one in 105 (one in 100,000) hours.
If the incapacity event is not 100% chance in a year, but only 1%, then hourly probability in a year is:
105 x 102 = 1 x 107 hours.
Similarly, if there is only 0.1% of incapacity, then probability of occurring in one hour of flying in a year is:
107 x 10 = 1 x 108 hours
Medical Certification – Multi-crew Risks
In multi-crew operations with two fully qualified pilots, the risk of both pilots having the same incapacity event at the same time, or the surviving pilot making a very serious error in the circumstances of his co-pilot having total incapacitation, is considered to be 1 in 10 (although in observations taken in simulator training, this is measured at better than 1 in 100).
It takes an average eight seconds for a pilot or co-pilot to realise that his partner in the flight deck has become incapacitated – a long eight seconds during complex operations such as landing or taking off.
Therefore in multi-crew operations the final risk is ultimately one event in 109 hours, or very similar to air worthiness targets.
Private Pilot Risks
For private fliers, the number of hours flown per year is significantly less. It is assumed to be one tenth that of air transport or commercial pilots.
This allows certification of a single pilot operator privately to 1% per year risk of incapacity. If the single private pilot flies with a safety pilot, then the risk can be accepted up to 10% risk of incapacity in any one year period, as a private multi-crew flight.
It is now possible to compute the risk factors for sudden incapacitation due to heart disease. This means that for a professional commercial ATPL pilot, when the various risk factors evaluated at medical examination, he/she may start to exceed acceptable risk levels due to possible cardiac disease processes.
This is particularly if they smoke tobacco or have high cholesterol or do not exercise etc. The combined risk factors may well exceed the acceptable levels well before reaching any technical retiring age for a particular company.
The aviation medical exam now includes routine cholesterol examinations, as well as questions about smoking, family history etc.
The message therefore is very clear for professional pilots in that they should cease smoking now. They should pay attention to lifestyle issues such as dietary control of cholesterol, exercise regularly and make sure their blood pressure is checked regularly and subject to medication if it is raised.
Commercial and ATPL pilots will now have regular cholesterol tests and the requirement to undergo stress test ECGs yearly from the age of 60. These tests will become regular features of their routine medical exams for a Class 1 certificate.
The opinions expressed in this article are those of the author (Dr Andrew Marsden) and do not represent formal CASA policy. They are designed to serve as a guideline for pilots in understanding how the risk assessment process works.