If this happens to you in-flight, pay attention.

1) Changes In Vibration

There's a variety of reasons an engine might run rough. Damaged components, carburetor ice, and improper mixture management are some of the most common reasons. Start looking for the cause right away, and if you can't solve it, plan to get on the ground before things get worse.

2) Headache, Blurriness, Or Nausea

If you have a cracked muffler and you have your heater on, carbon monoxide can start entering the cabin. And if that happens, your first signs of carbon monoxide poisoning will most likely be these symptoms:

3) Unusual Noises

As pilots, we become intimately familiar with the way our airplanes sound. Any unusual noises, whether it be electrical or mechanical, should be paid close attention to.

4) "Seat Of Your Pants" Feeling: Uncoordinated Flight

Have you ever flown uncoordinated or way out of trim? You might feel yourself "falling" to the side of your seat. This should be an indication to you that you need to re-trim, add rudder pressure, or that the flight controls might be experiencing a problem.

5) Euphoria Or Lightheadedness

Hypoxia occurs when your body is deprived of oxygen. If you start to experience hypoxia, there might be something wrong with your pressurization system or your oxygen system.. There are lots of hypoxia symptoms, and unfortunately, every pilot reacts differently. Here are some of the most common symptoms: Euphoria, Cyanosis, Visual Impairment, Headache, Impaired Judgement, Drowsiness.

6) Strong Smells

Have you ever smelled something in the airplane that wasn't quite right? Maybe it was a strong electrical component smell, gas, or smoke. Pay attention to what your nose is telling you because it might be a great indicator that something is going wrong.

7) Noticeably Different Control Pressures

You probably know the way your airplane "feels" when it flies. If you notice unusually heavy or light control forces, or something "catching" as you pull the yoke, there might be something wrong with the control rigging.

What else? What other physical cues can tell you that something is wrong? Tell us about your experiences in the comments below.

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