Friday, October 16, 2009

Ear Pollution in Flying Planes

Noise Pollution in Flying Airplanes - A Comparison

When we talk about Ear Pollution we must have an understanding of the intensity of common sounds for comparison. The list below gives you an idea where noise behind a Single Engine Small Plane stands with respect to other intensities of sound.

1. Threshold of Hearing........0 Decibels
2. Whisper.....................30 "
3. Quiet Office................40 "
4. Normal Speech...............60 "
5. Busy Street.................73 "
6. Cockpit Noise...............105 "
7. Hard Rock Music.............110 "
8. Threshold of Pain...........140 "

High intensity noise is one of the major causes of permanent hearing loss. It cannot be reversed. Sounds which exceed 85 decibels pose the greatest threat to the hearing mechanism. There are few sounds in nature that surpass this level and the ear is not prepared to cope with more than 85 decibels.

The exposure to high intensity of sound is important. The longer the exposure per week the earlier the hearing loss begins.The ear has three conduits for sound, outer ear (pinna), the middle ear, that houses the three little bones of the ear, that help transmit sound waves to the inner ear. High intensity sound affects the inner ear nerve found in the chochlea. (A sea shell shaped coiled structure) Hearing for high pitched sounds is affected first. With more exposure, more and more of the pitch range is destroyed until your hearing is really handicapped. Again, it is important to repeat that a noise induced hearing loss is permanent and cannot be reversed by medical treatment.

Frequently, hearing aids are not very beneficial since the nerve endings are destroyed. Hearing sensitivity is usually measured by finding the lowest intensity level a person can hear low, medium and high frequency musical tones. We interpret these sounds as different pitches. The impression of these sounds are recorded on an audiogram. If you ever went to an audiologist he or she would explain what the tracings represent.

If you remember your days as an audiophile the whole thing hinged on you receiving sound that was not distorted. If the ear is healthy the listener will have little difficulty in distinguishing between the various speech sounds.On the otherhand, if you have impaired hearing due to exposure to high intensity noise in the cockpit without protection, you may have great difficulty distinguishing such words as he and she, not and got and slow and low.For example, the phrase " You are too slow for a safe landing" and the phrase "You are too low for a safe landing" are similar but different enough to cost you your life.

Several things can be done to cut down on or prevent high intensity sound to protect against permanent hearing loss.Simplest solution is to buy a set of tight fitting earplugs. Sound reducing earmuffs are even better. Revolver and pistol shooting earplugs and muffs are acceptable if they fit. (A wad of cotton is useless!)

Scientists have found that understanding speech in noise is not impaired when wearing ear protection. Anyone who questions this can purchase a headset built into protective muffs. You can purchase these at any pilot supply store. High intensity noise does cause stress related error making decisions and general fatique that I have discussed in earlier articles. One point to remember is that engine noise, even with protectors on, is still loud enough to hear a decrease in RPM or a missing magneto. 

A final note, if you feel that your hearing may be impaired please make an appointment with an audiologist at your earliest convenience. They can assist you in finding the best ear protectors for your needs.

Red Light Blindness

Red Light Blindness

Red light blindness - the visual handicap that develops gradually affects most pilots including many that seem to have "perfect vision" under daylight flying conditions.

A good idea, if you are a pilot over the age of 40 years young, is to try and read fine print by red light before your next night flight.

What is red light blindness? Heres an example: You plan on taking your wife out to dinner at a local "feeding hole" located at a convenient airport about an hours flight away from where you hanger your plane.

You leave just a little after sunset in perfect weather. You need to cross-check your position and make sure the frequency of the next VOR is correct. Its dark in the cockpit so you turn on the red map light and spread a chart on your knees. You can't read it there so you pick it up for a closer look..yikes, it is still blurred. You move the chart right up under the red map light, you sense your eyes are widening and your forehead strains as you try to focus the fuzzy figures of the VOR frequency. Thats red light blindness.

How does red light blur vision?

At the age of forty your eyes ability to focus close up declines due to changes in the ability of your lens to alter its shape to clearly focus an image on the back of your eyeball. (the retina) This condition is called presbyopia.

In good illumination it is hard to read a newspaper held at arms length. I remember going through this and I will bet you have too. Red light has a rather long wave-length. It takes even more effort, on your eyes part, to focus on print in red light than in normal white light illumination. 

The pupil of the eye dilates to its maximum under dim red light, attempting to admit more light to the retina. The net result from the lens thickening and increasing its curvature and the dimness of the red light causes the image to fall slightly behind the retina. 

I will high-light several sources that will include diagrams to ease your understanding of eye physiology which is beyond the scope of a short blog. 

If you have an interest in photography the human eye is similar in operation. If you are near-sighted or far-sighted click on the links in this sentence.

Monday, October 12, 2009

Interrupted Communications - Non-Existent Communications

Interrupted Communications from Equipment Failure

With the incredible increase in miniaturization of avionics an old enemy still rears its head...HEAT. Remember the story about how cool transistors ran and the rage in the aviation community after spending thousands for new avionics only to have them fail. The answer to theses communication failures is simple: Get rid of the heat!

The best way is an air- conditioned hanger. Hangering an airplane goes a long way toward solving heat-induced avionics problem. For many of us, that is far too expensive.

Alternatives are much cheaper but may not be as effective. One of these is borrowed from autos, a cheap reflective foil panel for installation when the plane is parked. That will reduce but not eliminate entirely, the heat build-up problem.

Arrange for proper stack cooling if you have your plane serviced regularly. Vent ports are a good idea. Keep heat producing power devices above sensitive avionics. Same goes for your positioning of your home TV-Audio-Cable stuff...why not do the same in the plane. Unpressurized aircraft are easier to vent. Pressurized are more complex because they can't have any openings to the outside. Fans are okay but be careful of the magnetic fields created by fan motors that could cause problems with sensitive navigational equipment.

A problem with corporations that manufacture avionics is their sales stress reliability. If suddenly they seem to mention cooling that reflects, in an adverse way, on reliability. The majority of manufactures today insist on proper cooling of their avionics installation or the warranty is invalidated. Good enough reason for you to retrofit well preserved antique aircraft that you wish to communicate from consistently.

Scared? Uncertain? Frightened? How to Reduce "The Holloween Syndrome!"

Controlling "uncertainty" in flight....

Night-time flying can lead to a sense of uncertainty, especially if comforting visual clues are not forthcoming. You may unconsciously turn up the volume to the headset or speaker for communications. Fix? Turn the volume down to normal levels.

Finger tapping for no apparent reason. Fix? Stop the tapping.

Increasing the brightness of instrument illumination. Fix? Turn down the illumination.

You feel unusual tension developing in your face and body.

  • Try to relax and practice procedures you know that relax you. One possibility use the ADF radio station that broadcasts 'elevator music' that is relaxing. 
  • Stretching is another. 
  • Shoulder shrugs. 
  • Think good thoughts. 
You feel lost, in the geographical sense.
  • Fix? Use instrumentation to locate your position. 
  • Tune in to a major 50,000 watt radio station. 
Fix? Self-evident.

  • Use a handy checklist to set up a recognizable sequence to follow. That will, in many cases, provide the self help to get out of trouble.
Use the IFR Center in your area. If your plane is transponder equipped and you know your Center frequency, they can find you and they are trained in techniques to calm you down. Once calmed, you will be astonished as to what you now remember to aid yourself. Additional informatiion that tension may be rising is the "familiar becomes unfamiliar" and vice-versa.

In controlled airspace having fear arise, recognized and brought under control is vital. We all have our moments.   Recognize, in a simplified way, those signs of fear and deal with them quickly for your safety.