# BVLOS Unmanned Aircraft Operations in Forest Environments
## 5 Taking a Risk-Based Approach to BVLOS Operations in Forest Environments
### Other Considerations
#### 5.3.5 Drugs and Alcohol  
Drugs and alcohol are major concerns within the aviation context, with states often imposing strict regulations to manage associated risks. Alcohol is widely consumed, but it does cause performance detriments, primarily, in relation to cognitive and sensory functions [101]. While regulations vary between countries, they usually consist of a minimum stand-down period following any consumption of alcohol called the \"bottle to throttle\" rule (usually 8 or 12 h), which is the requirement to not pilot an aircraft unless your blood alcohol level is zero and to not pilot an aircraft under the influence of alcohol even if your blood alcohol level is zero [102; 103]. This latter point is important in capturing the ongoing impairment associated with hangovers. These are standards that should also be applied to unmanned aircraft operators to prevent any alcohol-associated impairment. Past research also suggests that pilots with previous convictions for driving while intoxicated are twice as likely to be involved in a pilot-error accident [104], providing a good basis for background checks regarding past compliance with transport regulations.  
Drugs can be divided into two categories of concern for unmanned aircraft pilots: the first are over-the-counter and prescription medicines, and the second are illicit substances. Over-the-counter and prescription medicines are legal substances, but that does not mean that they will be compatible with safe flying. All drugs are taken with the intention of affecting the human body, which means that they may have side-effects that are detrimental to human performance. Antihistamines are an example of a widely taken drug for hay fever that have a sedative effect and may be incompatible with safe flight (depending on the exact medicine and dose) [88]. Unmanned aircraft pilots should always check with their doctor as to whether a particular medicine they are prescribed or intend on taking is compatible with safe flight; in specialised cases, an aviation doctor may also be more appropriate to consult. Illicit drugs, on the other hand, are illegal and, often, consumption of these would result in loss of a pilot's license in manned aviation. Some of these arealso being legalised in some parts of the world, such as marijuana. In this instance, it needs to be viewed in a similar manner to alcohol, whereby its consumption may take place, but this should never affect performance in the workplace. Pilot performance has been shown to be impaired as long as 24 h after a social dose of marijuana, though the subjects are unlikely to be aware of its effects at this time [105]. It has been suggested that, since 1991, when the aforementioned study was conducted, the impact will have likely increased, as the potency of marijuana has begun to increase [106]. The key symptoms are impairments of a cognitive and psychomotor nature [106]. A 2011 research article that compared 10 years of drug testing data for employees in the United States commercial aviation industry found that the prevalence of drug violations (specifically for marijuana, cocaine, amphetamines, opiates, and phencyclidine) were 0.64% in random drug tests compared with 1.82% for post-accident tests, meaning that the odds of being involved in an accident was three times higher for those that tested positive than those who tested negative [107]. While not mandatory for unmanned aircraft operators, random drug and alcohol testing is widely used in the aviation industry to counter the effects of drugs and alcohol upon pilot performance. Unmanned aircraft operators should voluntarily undertake this in line with a clear drugs and alcohol policy to ensure that pilots involved in complex operations, such as BVLOS in forest environments, do not have their performance impaired by drugs or alcohol.