Ounce of Prevention Part 11 of 12

Preflight Yourself, Then Your Airplane

November 1, 2001

Watch out for the invisible dangers

Let's talk about the less overt hazards to your safety. Previously in this series we have talked about handling the more obvious ones such as running out of fuel, poor takeoff technique, poor planning, engine failure, and midair collisions. Now we're going to talk about safety threats that are less obvious and are more often ignored.


You're on a long cross-country flight in your unpressurized single-engine four-seater. The auxiliary tanks are filled and it will be four hours or more before you leave your IFR cruising altitude of 11,000 feet to land. Late in the flight, the controller asks if you would rather accept vectors to avoid traffic or climb to 13,000 feet and remain on course; he doesn't specify how long you'll be at the higher altitude. He hasn't a clue about whether you're wearing an oxygen mask. You readily accept 13,000 feet to avoid a delay, but you recall that regulations prohibit you from remaining above 12,500 feet for more than 30 minutes without supplemental oxygen. Do you have a problem? The regulations and the Aeronautical Information Manual (AIM) offer suggestions.

Federal Aviation Regulation 91.211 clearly states that your proposed plan is legal. The regulation is titled Supplemental Oxygen and states: "No person may operate a civil aircraft of U.S. registry at cabin pressure altitudes above 12,500 feet (msl) up to and including 14,000 feet (msl) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes' duration; at cabin pressure altitudes above 14,000 feet (msl) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and at cabin pressure altitudes above 15,000 feet (msl) unless each occupant of the aircraft is provided with supplemental oxygen."

Safety strategies

  • Perform the "I'm safe" checklist.
  • Be aware of the signs of oxygen deficiency.
  • Read labels to learn the side effects of over-the-counter medications.

Sounds cut and dried — you can pop on up to 13,000 feet for 30 minutes. But the AIM expands on the regulations and offers some advice. As you remember from your training, hypoxia is a state of oxygen deficiency — because of reduced barometric pressure — sufficient to impair the function of the brain and other organs. Deterioration in night vision can occur as low as 5,000 feet, but most pilots suffer no effects of altitude hypoxia below 12,000 feet. However, it may come as a surprise that hypoxic effects can start as low as 12,000 feet — or even much lower with some pilots — and can affect judgment, memory, alertness, coordination, and ability to make calculations. Also possible are headaches, drowsiness, dizziness, and either a sense of well-being or belligerence. The higher you are, the quicker the effects appear. At 15,000 feet, for example, effects are typically noticeable in 15 minutes unless the crew uses supplemental oxygen.

So how should you handle a request to climb to 13,000 feet? Accept the new altitude if you desire, but add a phrase such as, "We're limited to 30 minutes at that altitude," to your response. It alerts the controller as to whether a new plan is needed. And remember that — should effects manifest themselves — you may not have 30 minutes before needing to descend. Better yet, use supplemental oxygen.


Friends don't let friends fly drunk, of course. And most pilots won't let themselves fly drunk. But there could be pressure from nonpilot friends to cheat on the eight-hour rule just a little. Alcohol, unfortunately, has been a big contributor to accidents in the medical factors category over the years. Statistics from the AOPA Air Safety Foundation for the period from 1985 through 1994 prove it. In the early part of that time period there were more than 30 accidents per year in which alcohol was listed as a cause or factor. In 1994, the yearly number dropped into the teens, and hopefully the trend has continued: No data is available after 1994 because of a change in recordkeeping at the National Transportation Safety Board.

The regulation is clear. FAR 91.17 says, "No person may act or attempt to act as a crewmember of a civil aircraft within eight hours after the consumption of any alcoholic beverage; while under the influence of alcohol; while using any drug that affects the person's faculties in any way contrary to safety; or while having 0.04 percent by weight or more alcohol in the blood." If you're still under the influence nine hours after you have a few drinks, then you can't legally fly.

The regs also say that you can't fly someone who is drunk. FAR 91.17 continues with this admonition: "Except in an emergency, no pilot of a civil aircraft may allow a person who appears to be intoxicated or who demonstrates by manner or physical indications that the individual is under the influence of drugs (except a medical patient under proper care) to be carried in that aircraft." Again, that regulation will be difficult to explain to your nonpilot friends, assuming they are inclined to overindulge during that evening meal you flew them to. They want to go home in your airplane, drunk or not. Better find more understanding friends, at least for social activities involving flying.

The AIM offers good advice on the use of alcohol that goes beyond what the regulations require. "As little as one ounce of liquor, one bottle of beer, or four ounces of wine can im-pair flying skills, with the alcohol consumed in these drinks being detectable in the breath and blood for at least three hours," the AIM states. And don't forget the hangover. You may adhere to the time requirements for alcohol consumption but still be impaired by the aftereffects. Even a small amount of alcohol makes :ou more susceptible to disorientation and hypoxia. Yes, the regulations say that you can fly eight hours after drinking, but the AIM suggests you wait 12 or even 24 hours, depending on the amount of alcohol consumed.


Let's skip a preachy warning about hard drugs, since accident reports indicate that most of you have just said "No" to drugs. Drugs can still affect you — even over-the-counter drugs that you had always assumed were safe. For an overview of the problem, a copy of a pamphlet titled Over-the-Counter Medication in the Cockpit is available on AOPA Online ( www.aopa.org/members/files/pilot/1993/otc9305.html). Or you may call the AOPA Pilot Information Center at 800/USA-AOPA (800/872-2672) to order a copy.

Here are a few highlights from that pamphlet:

If you feel bad enough to take medication, you might consider staying in bed. That said, there are many mild symptoms that can be treated safely with over-the-counter remedies prior to flight. However, no two people are &ffected the same way by the same med-ication. Antihistamines often cause drowsiness while decongestants can cause stimulation or nervousness — but you may experience neither effect. Your best strategy is to read and follow the warnings on the label, perhaps waiting longer than the usual period listed.

An obvious idea is to avoid taking a new medication before flight. Better ground-test it first, especially if the flight is expected to be a long one.

Prescription medications often have the potential for more serious side effects. As the AIM notes, tranquilizers, sedatives, and strong pain relievers can impair judgment, memory, alertness, coordination, and vision. Other drugs, such as antihistamines, blood pressure drugs, muscle relaxants, and agents to control diarrhea and motion sickness can also impair the same critical functions. And any medication that depresses the nervous system, such as a sedative, tranquilizer, or anti-histamine, can make a pilot more susceptible to hypoxia.


Feeling lousy? Most of the time common sense will kick in and you'll voluntarily ground yourself. Consider whether your illness is just arriving or just departing. If you have a rising fever with that aching-all-over feeling, as the AOPA pamphlet on over-the-counter drugs notes, it is likely to get worse. Good idea to stay away from the airport.

Often it is the illness itself that is the problem and not the medications that accompany it. Take strep throat as an example. It is usually treated with penicillin and aspirin or Tylenol. Under most circumstances, doctors say, it is safe to fly with those medications. But strep throat often comes with a fever high enough to cause delirium in addition to annoying throat pain. You can fly with the medications but not with the illness itself.


Trips are tiring, and the resulting weariness is a safety factor on the return flight home — usually a manageable one. But how do you know if you are too tired? The answer is obvious if you partied all night long. But most of the time it falls into a gray area.

The AIM divides fatigue into acute fatigue and chronic fatigue. Acute fatigue is considered normal and is the tiredness felt after long periods of physical and mental strain, including strong emotional pressure, monotony, or lack of sleep. It interferes with concentration and alertness but can be fixed with adequate rest and sleep, as well as regular exercise and proper nutrition.

Chronic fatigue occurs when there isn't time to recover between episodes of acute fatigue. Performance and judgment suffer so much that you may unknowingly take unnecessary risks. It's time to call the folks at Carnival Cruise Lines.


"Leave your problems on the ground" sounds like a good idea, but just try it. Difficulties at work or unresolved personal problems are likely to occupy more than their fair share of your daily thoughts. It is called distraction, and it is often the reason behind a pilot's decision to fly into deteriorating weather to keep to a schedule. Add a little stress to the fatigue mentioned above and you have an explosive mixture. The obvious solution is to stay on the ground, yet under such circumstances it is hard to take your own advice, particularly if peer pressure is involved. If you know you are under stress and you intend to fly, be aware of it and resolve to focus all of your attention on flying duties while in the airplane.


Top stress producers listed in the AIM include such emotionally upsetting events as a serious argument, the death of a family member, a separation or divorce, the loss of a job, or a financial catastrophe. "The emotions of anger, depression, and anxiety from such events not only decrease alertness but also may lead to taking risks that border on self-destruction," the AIM warns. You may want to hold off on that next flight until finding a resolution to your emotional state, or fly with a friend and ask him or her to accept pilot-in-command duties.

Are you safe?

You may have heard of the "I'm safe" checklist offered by the FAA. Consider what it means the next time you fly. The letters in "I'm safe" stand for: illness, medication, stress, alcohol, fatigue, and emotion. If you are not suffering unmanageable problems in any of those categories, you're good to go.

E-mail the author at [email protected].

Al Marsh

Alton K. Marsh | AOPA Pilot Senior Editor, AOPA

AOPA Pilot Senior Editor Alton Marsh has been a pilot since 1970 and has an airline transport pilot certificate and instrument and multiengine flight instructor certificates, aerobatic training, and a commercial seaplane certificate.