Aircraft parked in the ARIZONA DESERT in an aircraft graveyard.

Located just outside the gates of Davis-Monthan Air Force base in Tucson Arizona are a series of Aircraft salvage yards. These salvage yards are here to feed off of the steady flow of demilitarized aircraft auctioned off by the Aerospace Maintenance and Regeneration Center AMARC. AMARC is responsible for the storage and aircraft parting out of excess Department of Defense and Coast Guard aircraft.

Anything the government sells, which could cause potential injuries or be used by a hostile government is “demilled” before it leaves their control. Demilling, which stands for de-militarising, can include chopping wings off, or cutting the fuselage or disarming electronic panels and ejection seats.

Because of this Demilling process, most aircraft are rendered useless for flying and are destined to become exhibition pieces, broken down for aircraft parts salvage or aircraft parting out, or melted down for scrap metal.

Tucson’s dry climate and alkali soil has made it an ideal location for storing aircraft, a role it has held since it was selected after WWII as a storage site for hundreds of decommissioned B-29s and C-47.

Reclaimed aircraft parts

Post Vietnam, this legacy continues today, as the city boasts the most aircraft salvage yards for reclaimed aircraft spares recovery of any city in the world. The surreal photographs are well known worldwide.

It is possible, on a visit to Tucson, to drive round a field of old 707s from the dawn of the age of commercial jet travel, many with the logos of since bankrupt airlines like Pan Am and TWA. They were originally brought to AMARC for their engines which could be removed and used for upgrades.

A fence keeps you from getting close to the C-123 Providers. C-123s were used to drop millions of gallons of Agent Orange during the Vietnam War to defoliate forests to deny cover to the North Vietnamese. You can’t touch them because of OSHA rules (Occupational Safety and Health Administration). So they could still be there in fifty years. Perhaps they could be declared a monument to soldiers and civilians harmed by Agent Orange.

You can drive slowly under a long canopy formed by the tails of Boeing 747s parked in the Sonoran Desert 20 miles west of Tucson. Beyond a vast expanse of desert and cactuses, mountain peaks rim the horizon. It’s warm. More importantly, it’s dry.

In row after row of silent, abandoned airliners, great jets that once soared over the earth, more than 300 are parked here. Some are going to be worked over and eventually resold to airlines around the world. Others are waiting for the banks or domestic airlines to reclaim them. Many are waiting for mechanics to strip away useable parts before wreckers tear apart the fuselages for aluminium.

Aircraft Structures Design

Airframe structures can be made light, yet strong and stiff, and the aircraft skin contributes to the overall strength of the structure.

All airframes, whatever the aircraft, are designed using the same principles. The smooth exterior provides a streamlined shape, with extra supporting structure underneath to provide the strength and stiffness needed to operate effectively. In many modern aircraft, the covering and part of the framework are made from a single piece of material. The outer skin, then, hides a complex piece of structure that must be strong, stiff and reliable.

Struts, ties, beams and webs.

The structure of most airframe components is made up of four main types of structural member. Ties are members subject purely to tension (pulling). Because tension will not cause the tie to buckle, it does not need to be rigid, although it often is. Ties can be made from rigid items, such as tubes, or simply from wire, like the bracing wires on a biplane.

Struts carry compression loads. Because compressive loads can cause the member to buckle, the design of a strut is less simple than a tie. If overloaded, struts will fail in one of two ways: a long, thin strut will buckle; a short, thick strut will collapse by cracking or crushing, as the material from which it is made is overstressed.

A medium strut may do either, or even both, depending on its dimensions and on other factors. Tubes make excellent struts, because the material is evenly loaded, so that the strength-to-weight ratio is high in compression.

Beams carry loads at an angle (often at right angles) to their length, and so are loaded primarily in bending. Many of the major parts of an airframe are beams, such as the main spars. The fuselage and wings themselves are structural members, and are beams, because they support the bending loads imposed by weight, inertia and aerodynamic loads.

Webs are thin sheets carrying shear loads in the plane of the material. Ribs and the skin itself are shear webs. Thin sheets are ideal for carrying shear, especially if they are supported so that they resist buckling.

You may get the impression that each part of an airframe is either a tie or a strut or a beam or a web, but this is not so. Some items, such as wing spars, act almost entirely as one type of member, but others act as different members for different loads.

For instance, the fuselage skin may be subjected to tensile and shear loads simultaneously. Pure bending loads almost never exist alone; they are almost always related to a shear load. So a beam will normally carry both bending and shear loads.

The aim of aircraft structural design

By carefully mixing these members, and making sure that each part of each member is taking its share of the loads, aircraft structural design will achieve the greatest strength with minimum weight, and so get the best operating efficiency and maximum safety.

It is the designer’s aim to ensure that each part of each structure carries a reasonable stress, so that the capability of every part of the structure is used effectively. Only by doing this can the weight of an airframe be made as low as possible, while still providing adequate strength.

There are many uses of struts in an airframe, including the supports for the floor in transport aircraft, undercarriage legs, actuation jacks of all kinds and pushrods for operating flying controls. Struts also frequently act as ties, when the load they take is reversed; again, actuation jacks are typical examples of this.

Little Airplane/Big Sky – Why Aircraft Collide In Flight & How To Prevent It

I was a commercial helicopter pilot for 35 years. In my career, I racked up nearly 1.5 million miles across the ground, carried, as near as I can tell, about 100,000 passengers, and finished up with 12,500 hours of flight time in my logbook. The most important number? I ended up with an equal number of takeoffs and landings.

Kidding aside, considering the public perception of the helicopter business, this may seem like an astonishing outcome. Most people truly believe that helicopters are dangerous contraptions capable of all manner of unpredictable, mostly nasty behaviors. The truth is, as I often told my passengers, the dangerous part of my job was driving in to work.

But there is a real danger involved in the helicopter industry, partly because of the way helicopters are operated, and that’s the ever present peril of midair collisions. Most helicopter operations take place from what the FAA refers to as ‘unimproved areas’, that is, unmonitored heliports, crude landing spots in rural areas, and generally remote places where radio or radar oversight is nonexistent. The general rule calls for pilots to simply see and avoid each other. Seems straightforward enough.

Even so, there are a number of midair collisions and near misses each year. Pilots do, of course, monitor radio frequencies, and ought to be constantly aware of the presence of other air traffic. But in the absence of an outside monitoring facility such as an FAA control tower, or other ATC facility, which situation is standard in the helicopter business, it’s up to the pilot to steer clear of other aircraft.

It goes without saying that a collision between two aircraft almost always results in fatalities. When one of those machines is a helicopter it always does. A fixed wing aircraft has the possibility, albeit remote, of recovering from a midair, and possibly, maybe, perhaps reaching the ground somewhat safely. A helicopter does not. Any time the main rotor system of a helicopter is disrupted the aircraft will crash.

Done. So in many respects it’s incumbent on helicopter pilots to be constantly aware of other aircraft, particularly so when, as was the case in the recent New York midair, the fixed wing was likely operated by a private, possibly lower time pilot.

In addition, though the investigation has just begun in New York, design factors may have played a part. Helicopters typically have much more visibility from the cockpit than a fixed wing machine. Airplane cockpits generally have more limited visual fields, particularly a low-wing plane where the wing itself acts as a blind spot to traffic beneath.

So how to prevent midair collisions? How to keep aircraft separated in flight when there’s little or no outside monitoring, no on-board technical prevention mechanism? Here are a few suggestions for students, or any other pilots with a desire to retire as I did with no such ugly incidents in their record.

I did have a few close calls: one near collision in Vietnam at dusk; another near Dubuque Iowa one cloudless, sun-splashed afternoon in July; and another reasonably close call with an impressively large offshore marine bird that could have taken out my windscreen had I not avoided him.

There are those in the aviation industry, mostly younger or inexperienced pilots, who subscribe to the ‘little airplane big sky theory of midair avoidance. Simply put, those pilots believe that in so vast a region as the sky, and while presenting such a meager target, their opportunities for contact with another aircraft are nearly negligible.

Even though instructors always demand that student (and all other) pilots keep their heads ‘on a swivel’, some pilots keep their focus inside the cockpit for long periods, glancing up only occasionally. So the first rule is to look outside the aircraft once in a while. A good rule of thumb would be, oh, like, every ten seconds–okay five seconds.

Another way to stay free of other traffic is to monitor the radio. Listen to the chatter, pay attention to who’s taking off, or who’s landing, and from where. Called situational awareness, it’s our best friend while flying, or looking for the car in a crowded parking lot.

Know where you are all the time. This may sound simplistic, but if you know where your aircraft is within a quarter mile at all times, and other traffic reports in that same box, you need to be looking. And don’t assume they see you. One of the big killers in aviation is complacency.

It’s killed more pilots than running out of gas. A classic mishap several years ago involved a commercial 727 landing at San Diego which collided with a Cessna 172 in September 1978. The pilots of the big airplane reported that they had the aircraft in sight. But the plane they reported seeing was a third aircraft. They never saw the one they ran into, and 137 people died.

Another phenomenon that can cause midairs is called rate of closure. In free air the perception of speed is difficult to distinguish from a cockpit. Closing on another aircraft, an inexperienced pilot can misjudge the rate at which the two are approaching, and literally fly into the other machine. It happens, especially when a pilot believes he has plenty of time to react, and finds out otherwise.

As for the little sky theory, just as in the San Diego crash described above, the vast majority of midair collisions happen on a clear day within five miles of an airport. In the New York City example, the helicopter had just lifted from the heliport along the Hudson River and was ascending.

It’s speculation at this point, but it appears likely that neither pilot saw the other, so there was no time to evade. This accident may have been prevented by more vigilance from both cockpits, particularly considering the congested corridor along the river.

Aviation accidents are not inevitable. They’re the result of human oversight, complacency, lack of attention, and disregard for limitations. As one of my instructors used to say, “We’re not inventing any new ways to crash”.

Midairs can be prevented, with a healthy regard for just how congested the airspace really is–and getting more so all the time–cultivating a good habit of situational awareness, and using whatever resources are available in the cockpit and outside it, such as radar coverage, position reporting on the radio, and teaching passengers to look outside as well.

When Using A Buffer To Detail An Aircraft There Are A Multitude Of Things To Consider

Aircraft paint is very thin, and really it has to be that way to save the weight. If an aircraft gets too heavy, it takes bigger wings and a larger power plant or motor to fly. Think of the paint weight this way; if you have a five gallon paint pail how much does it weigh?

And how many gallons does it take to paint the aircraft. Well, let’s say it takes 25 gallons to paint the aircraft, that is the same as putting five of those paint pails in the backseat and flying around with them everywhere you go, on every flight for as long as that aircraft shall both live. See that point.

Now then since that paint is really thin, it’s very easy to go through it with a buffer and take it down to bare metal, aluminum that is or fiberglass, titanium, or carbon fiber. Not only will that piss of the owner of the aircraft, but you’ll get a pretty bad reputation around the airport if you are running an aircraft detailing business if you do that.

But, there’s even a bigger problem, once the paint is thin or removed corrosion can start in or taking down the paint on the control surfaces could cause adverse flight effects. Do you doubt what I’m saying?

The FAA issued an airworthiness directive for the Gulfstream line of corporate jets which will become effective on August 1, 2012 and here is the summary of what it is and why they have made the issuance of this AD for the Gulfstream Model G-IV, GIV-X, GV, and GV-SP airplanes;

“This AD requires measuring to determine paint thickness on the flight control surfaces and corrective actions if necessary, and revising the Airplane Flight Manual (AFM). This AD was prompted by reports of failure to inspect or document the paint thickness on flight controls (ailerons, rudder, elevator), potentially having a negative impact on the flutter characteristics of the airplane.

We are issuing this AD to detect and correct paint thickness on flight controls, which could result in loss of control of the airplane due to flutter.”

Are you beginning to see why you need to be an expert with a buffer before you use it on the surface of an aircraft, or why you need to train your crews professionally? And even when you do, might I suggest you stick to an orbital buffer, and not use anything high-speed until you have years of experience? Please consider all this and think on it.

Is An Aircraft An Aeroplane Or The Other Way Round? The Importance Of Proper Terminology

A lot of air traffic management related material passes through our hands, usually to be checked with a view to ensuring quality of content and consistency of the terminology. There is a disturbing trend that is becoming more and more evident with the passage of time. The documents show a deteriorating level of quality in respect of terminology use.

Why is this a problem? Unless they have been sensitized to the issue, the authors of those documents may not feel particularly disturbed by the fact that they use the terms aircraft, aeroplane or airplane interchangeably in their text, they may even feel that the varied use of words reflects better writing style. But in technical documents, the terms used must all have their precise definition and it is not enough to find a given word in a Webster’s Dictionary.

Let’s have a look at these three words, aircraft, aeroplane, and airplane. They are all English words and they all mean something that flies. Very true. But there are many things that “fly”, from hot air balloons to helicopters and, depending on how you define “fly”, even hovercraft. So how do we know which exactly a given text refers to if it is not clear from the context?

If you see a piece of text that says “a flashing white light shall be displayed on all aircraft” and then another one that says “a flashing white light shall be displayed on all aeroplanes” and you own a helicopter, a glider and a hot air balloon, which one would you need to equip based on the first requirement? And the second?

Although I assume you know the answer without the explanation that follows, it is still interesting to look at these terms in more detail.

First and foremost, we have to say good-by to the term “airplane”, at least in the international context. Only aircraft and aeroplane have been defined by the International Civil Aviation Organization (ICAO).

An aircraft is any machine that can derive support in the atmosphere from the reaction of the air other than the reactions of the air against the earth’s surface.

A aeroplane is a power-driven heavier-than-air aircraft, deriving its lift in flight chiefly from aerodynamic reactions on surfaces which remain fixed under given conditions of flight.

So what do these definitions tell us? A hovercraft is not an aircraft (reactions of the air against the earth’s surface) and a glider is not an aeroplane (power driven) but it is an aircraft. A balloon is an aircraft but it is not an aeroplane… and so on.

As you can see, expressing requirements, infrastructure suitability and services desired does need proper terminology use, otherwise things quickly become ambiguous, leading to misunderstanding and endless discussions.

We used the terms aircraft and aeroplane (the subject of the most common errors) as examples but there are scores of other terms which, if used improperly or inconsistently, can lead to serious problems of understanding.

A few simple rules can help

Proper terminology use is not rocket science. It needs good knowledge of the subject and a bit of discipline. Here are a few simple rules that can help.

• If there is an ICAO defined term for something, use it.ICAO has developed definitions for the terms it uses in the provisions aviation the world over follows. Using terms as defined by ICAO provides immediate benefits in terms of consistency with ICAO documents and documents derived from them. Those definitions are also consistent among themselves.

• If there is no ICAO definition but a definition from another big organization, use it. In some cases ICAO may be lagging behind developments and they may not have a definition (yet) for a term or the term is not used in the ICAO provisions. Some other organization may however have developed a definition that is widely accepted or even standardized. In such cases, this recognized definition should be used and the source clearly identified. There may be several definitions from different sources… use the one that appears to be the most appropriate but use it everywhere consistently.

• Create your own definition. In some cases you may find that a term that nobody has yet given a definition needs to be understood in a particular way and only that way. Create your own definition and use it consistently across your documents. It is also a good idea to try and promote your new definition. If you had a need for it, so might do others. The wider it will be used, the better for overall consistency.

• When a term has multiple meanings. A great example of this is air-side and land-side, two terms that divide an airport in two, one you might call the public area and one restricted to passengers and employees only. The trouble is, there are at least two schools of thought on where the dividing line is between the air-side and the land-side. Although the dividing line is always artificial and arbitrary, its actual position does make a difference to the processes that extend across the division. In such cases feel free to adopt whichever dividing line position is best for you, however, always state clearly where the boundary between air-side and land-side is (or any other aspect the given term requires). A clear indication mitigates the negative effects of this kind of multiple usage.

• Be consistent. Perhaps the most important rule is to be consistent. There is only one thing worse than using undefined terms or terms with the wrong definition and that is using terms inconsistently across a document. Inconsistent use of technical terms is the surest way of confusing the reader.

What about abbreviations?

Few disciplines in the world are so prolific with creating abbreviations as aviation. When we speak, the uninitiated may think we are using some kind of secret code language… Worse, we tend to assume that each of us knows all the abbreviations from every part of the business while in fact CUTE (Common User Terminal Equipment) may mean nothing to an air traffic controller while ATIS (Automatic Terminal Information Service) may sound like a four letter word to a check-in agent. To managers higher up, who may have come from the financial world, neither CUTE nor ATIS may say much except if there is a price put against them… So what to do with abbreviations?

Here again the main rules are: use accepted abbreviations whenever possible and be consistent at all times. Include a list of abbreviations in all technical documents and consider writing the words full out (followed by the abbreviation) when first used in the text.

Avoid creating new abbreviations. Of course this is not always possible, if nothing else, there are new working groups, new processes, new equipment and they all crave their own, easy to remember names. So, go ahead and come up with new abbreviations but do try to avoid re-using abbreviations that already have a well established meaning. You may feel that your field is stronger and you will eventually squeeze out the other guy but believe me, not paying attention to this will only confuse everybody.

What if you are writing in your national language?

Whether you are writing in English or your national language, the guidelines are the same. But, they may not be so easily implemented if the terminology has not yet been introduced into your language to the same level of detail as it is in English.

There may be opportunities to be a pioneer in enriching the local language with the required new terms… In some cases trying to force consistency and new terms onto the professional writing scene may not be easy or appreciated by your peers. Use good arguments and examples similar to those above to convince them of the importance of proper terminology use.

The responsibility of SESAR, NextGen and SWIM

Experts in Europe and the United States are busy writing the blue prints for the next generation air traffic management systems SESAR and NextGen respectively. Those systems will introduce new concepts, new technologies and new processes, each bringing with them their specific terms and abbreviations.

System Wide Information Management (SWIM) is something that draws heavily on ideas first put forward in the general information technology field, with SWIM applying those things in an aviation context.

All the above activities will be generating tons of new documents which must be consistent across the board, both in terms of the old definitions and abbreviations and the new ones they will be introducing. Their responsibility is huge if we consider that the SESAR and NextGen documents will determine for decades to come what is called what and what we mean by what.

Get it wrong or inconsistent and future generations will struggle with the inconsistent, diverging terminology for a long time to come.

The new documents we see to-day are cause for concern and show signs of people ignoring the simplest rules of terminology use. They must remember that at the end of the day, we will all need to know beyond a shadow of a doubt whether we need to bolt that flashing white light onto the particular flying machine we own. Only consistent, proper terminology can help in deciding…