PRIOR ISSUES

The National Transportation Safety Board (NTSB) found the cause of the accident to be fire in the engine compartment. An exhaust pipe inadequately held in place by an automotive clamp had separated.

Aviation clamps have a pin assembly which add extra support so the clamp resists vibrating loose.

Exhaust systems in aircraft carry away hot gases released during combustion, reserve some heat for carburator and cabin heating, and muffle the sound of those rushing toxic gases. These systems operate red hot at temperatures of 1000 degrees fahrenheit or more.

The two major stresses on an exhaust system are:
1. Vibration fatigue
2. Thermal fatigue.

Wear due to vibrations are the most common cause of system breakdowns. Exhaust system failures generally reach a maximum rate of occurrence at 100 to 200 hours' operating time, and over 50 percent of the failures occur within 400 hours.

There are two main assemblies in an exhaust system. The manifold is made up of a series of pipes that gather the gases from the cylinders and send them to the exhaust pipe. The muffler assembly dampens the sound of the escaping hot gases and diverts hot air for the carburator and cabin heating.

Leaks around the manifold are caused by corrosion and vibration cracking. Areas where there is stress, slip joints that no longer slip and welds and parts are clamped together are prime spots for cracks and breaks. Engine backfiring and the combustion of unb urn ed fuel add corrosion to the system.

Half of all exhaust system failures are traced to cracks or ruptures in the muffler assembly. Breaks in the heat exchanger surfaces used for cabin and carburetor air heat sources are found near welds and stress points. Exhaust gases escape into the cabin heat system delivering carbon monoxide to occupants of the aircraft .

The October 1998 issue of Aviation Maintenance Alerts (AC 43- 16A) has the account of a plane crash with two deaths caused by carbon monoxde poisoning. The aircraft had an annual inspection thirteen hours prior to the flight yet, the extensive corrosion that caused the leak had not been corrected.

Baffles inside a muffler can fail forcing the hot gases back into the engine. This will cause loss of power and cylinder damage. Any engine backfiring should trigger an exhaust system inspection.

When inspecting look for:
Cracks in the exhaust stack
Stains, white to brown, on the cowling
Blistering of the paint on the cowling
Loose fittings.
Shine a flashlight up the exhaust stack to look for loose baffles that may be blocking the exhaust outlet. If the exhaust stack is cool, check for any movement. Check the carbon monoxide detector in the cabin, or bring one in your flight kit to use.

If you own your airplane and experience a power loss, take off the cowling and inspect the system for blistering, corrosion and loose fittings. Thump the muffler with the palm of your hand to be sure the baffles are not loose. If you rent, know the expected performance of the aircraft and if you are not getting that performance, check with the mechanic. Even better, hang around during a hundred hour inspection some time and get a good look at that exhaust system.

You can protect yourself and your passengers in three ways:
Preflight inspection
In-flight awareness
Post flight inspection. These actions are your allies. The three together support a flight safe from fire, loss of engine power and carbon monoxide poisoning.

by Kathleen O'Brien, SPM, LGB FSDO

Why don't you understand me?

My message machine has a stranger's voice on it. It's my voice, but to my ears it sounds different. Is it the same for you?

We probably sound different on our aircraft radios from the way we think we sound.

Researchers tell us that people respond to the tone of the voice five times more powerfully that to the words we use. Try an experiment.

Listen to a call-in radio show some day when you're stuck in traffic. Notice that you will have an idea about what that caller is like in the first few seconds of sound.

Pitch and pace can get you heard or ignored. Pitch is the tone of the voice. High pitched voices sound excited, childish or nervous. Pace is the speed you use from word to word. Pace too quickly and you may be judged impatient or rude.

People tend to reflect the pitch and pace of the speaker. When you use a lower tone and a moderate pace, people will tend to perceive you as knowledgable. A side benefit to lower pitch and moderate pace is that you will mostlikely be understood the first time you transmit.

I have been a flight instructor for many years. One of the things I try to instill in my students is the practice of asking the question, “WHAT IF……?” For example, whenever you’re flying an airplane you should always be asking, “What if my engine dies right now?” To me, this question seems to be especially relevant when flying in the airport pattern. In fact, I believe any good pilot uses that as the criteria for how he flies the pattern.

Over the last couple of years I have seen the normal traffic pattern deteriorate to the point that, in many cases, it has become unsafe to follow aircraft in the pattern. Often times it is difficult to determine whether the plane you are following is even remaining in the pattern. I have seen planes that are an eighth of a mile or more to the left or right of center line. I have seen planes on the upwind leg so far to the left that they are actually flying into the downwind leg. I have also seen planes on the upwind leg of the left runway so far off to the right that they are to the right of the parallel runway. The scary thing about this is there are often instructors on board these planes. Instructors, I know it can get busy in the cockpit but sacrificing the safety of the flight because you’re talking to the student is unacceptable. All of us have a responsibility to be aware of where we are, and as best we can, where the other guy is. When a pilot isn’t flying a normal pattern, determining where the other guy is becomes more difficult.

I hope it is obvious to all of us that drifting into the upwind leg of the parallel runway is dangerous. But what about drifting to the other side? Or, what about extending the upwind leg and crosswind leg? I teach my students to listen to the radio and try to visualize where everyone is in the pattern. Then, when they are scanning they have a better idea where to look for the traffic. If you’re following a plane in the pattern and you’ve just done a touch and go, you’re probably looking for the plane ahead of you to be on the upwind or crosswind leg. If that plane has drifted way to the left you may not see it. Or if the pilot has extended their upwind to a great degree, you may think he must be on the downwind leg already and turn crosswind. You are now ahead of or turning into the path of a plane that is not where you thought it was. We, as pilots, have been given (for all you old Star Trek Fans) “The Prime Directive” of “See And Avoid”, but we make it very difficult for the other guy to do that if we don’t fly a proper pattern.

The main problem I am seeing out there is the distance pilots are extending the downwind leg from the approach end of the runway. When you pass the numbers of the approach end of the runway, on the downwind leg, you should be thinking, ok, if that runway, that is disappearing behind me, is where I want to land, maybe I shouldn’t get too far away from it. Something I always emphasize to my students is to try to stay close enough to the airport, that in the event of your losing your engine, you can still glide back to the airport. (preferably to a runway, but you’ll be a hero even if you can make it to that nice flat airport property!) You see, people who don’t fly, for some strange reason, don’t like airplanes coming down on their streets or worse, into their front yards or houses. For that matter, there may even be some pilots out there who feel the same way. So how can we avoid that? Simple. Fly a tight pattern and turn base leg before you have extended too far downwind. This will help to avoid mid-air conflicts with aircraft in bound to the airport and hopefully enable you to make it back to the airport in an emergency. And another thing, flying three to four hundred feet above the houses and dragging power to make it back to the airport, doesn’t do much for our community relations.

So what is a normal pattern? The AIM has a diagram and some recommended procedures for a safe pattern in section 4-3-4. These are my personal recommendations for flying a safe pattern. Unless there are noise abatement procedures, fly the upwind leg maintaining center line. Commence the crosswind leg within 300 feet of pattern altitude or upon reaching 500 feet above ground level, which ever comes first. While on the crosswind leg and approximately 45 degrees from the departure end of the runway begin the downwind turn and fly parallel to the runway. Maintain pattern altitude until abeam the approach end of the landing runway on downwind leg. When approximately 45 degrees off the departure end, or at most, no further than, in the event of an engine failure, you could glide back to the airport, begin you’re base leg. Finally, start your turn to final approach early enough that you don’t overshoot final. Flying a proper pattern will enable you to do more landings, ensure that you will usually be able to make it back to the airport in an emergency, and help other pilots see and avoid you.

Coming in February…

There are no Wings Seminars this month. We know all you would be thinking about is the shopping you had left to do, so go do it.

 Benjamin Dacayana

Cecile Davidson