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Narcosis and Hypoxia Kill

by Jeremy Cox 1. February 2007 00:00
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Recently many of us were surprised to follow the story of the two crewmembers in a King Air B200 bound for Virginia from Arkansas who experienced what appears to have been a case of Hypoxia and possibly even a mild case of Narcosis as a result of some kind of cabin depressurization, probably due to the failure of the outer pane of the King Air's Windscreen. From what I have learned about this eventful flight, the crew were approaching the Cape Girardeau area of South-eastern Missouri at FL290 when it appears (on radar and flight-tracker) that the aircraft performed a 360 degree turn while varying its speed and altitude, and then it plunged down to somewhere around 7,000 feet where the crew appeared to have recovered the aircraft having lost pitch control of the aircraft (it was later discovered that both elevators had fluttered right off the horizontal stabilizer while both the entire empennage and both wings had deflected so severely that they were creased and bent!) Fortunately with the prodigious use of airspeed and engine power, the crew were able to make a fast, but safe landing into Cape Girardeau. These chaps were lucky, but there have been countless instances where Hypoxia as a direct result of a cabin depressurization event has caused the loss of aircraft and their occupants. A recent and most horrific example is Helios Airways flight 522, a Boeing 737 that eerily cruised over the Mediterranean skies with no response from either the cockpit or any of the almost 120 passengers in the main cabin. The world's television networks watched in horror as the aircraft eventually crashed into a Greek mountainside. The Payne Stewart, Learjet 35A crash is also a carbon-copy of this accident. So how can these types of 'near-accidents' and tragedies happen?, what is Hypoxia? and how can it be prevented?

According to a medical report authored by various aero-medical physicians of the United States Air Force (USAF), people flying in un-pressurised aircraft at high altitude after a rapid decompression can experience Altitude Decompression Sickness (ADCS; a.k.a Nitrogen Narcosis as it is known outside of the USAF) which is the same as the 'Bends' that deep-sea divers suffer from when they ascend to the surface too quickly. ADCS is an phenomenon governed by Henry's Gas Law, whereby when the pressure of a gas over a liquid is decreased, the amount of gas dissolved in that liquid will also decrease; in simple terms open up a can or bottle of carbonated beverage and the hiss and subsequent bubbling is a direct result of Henry's Gas Law. This phenomena applies to we humans, especially to pilots and divers, because we all store nitrogen, an inert gas, all-through-out our bodies as a result of respiration. When we experience a rapid reduction in pressure, either water or air, the nitrogen stored in our tissues starts to bubble and fizz just like a beverage being uncorked and when we have gas bubbling within our bodies we will experience an 'Air Embolisim' which results in paralysis and subsequent death unless it is quickly treated by re-compression. Unfortunately the 'Bends' (pain may be reduced by bending the affected joint like an elbow, shoulder, hip, wrist, knee or ankle to a more comfortable position, therefore the term 'Bends' was applied) can creep up on you and therefore you should always keep an eye on your Cabin Differential Gauge and the Cabin Vertical Speed Indicator, while looking for the tell-tale medical signs that you are: Localized deep pain from mild to excruciating in any of your joints; confusion, memory loss, headache, tunnel vision, double vision, blurry vision, unexplained fatigue, vertigo, nausea; tingling or burning sensations around the lower chest or back, abdominal or chest pain; incontinence, muscle weakness or twitching; shortness of breath, dry constant cough; itchy ears, face, neck, arms and upper torso, mottled or marbled skin around the upper body, and or welling of the skin accompanied by tiny scar-like skin depressions. According to the USAF, 'recompression' is the only effective treatment for severe ADCS, although rest and oxygen (delivered from a tight fitting mask) when applied to milder cases may bring about recovery without damage. For specialist aviators like astronauts, record breaking balloonists and/or parachutists, etc. or high altitude reconnaissance military pilots, the pre-breathing of 100% pure oxygen for 30 minutes before the commencement of their flight, and then the continuation of the breathing of 100% pure oxygen will 'drive-out' the nitrogen that has already formed in their tissues and then it will continue to prevent any new nitrogen entering the body. Having oxygen in your tissue instead of nitrogen does not eliminate ADCS, but it does make the recipient less susceptible to an early onset.

In addition to the massively debilitating effects of ACDS as a result of a rapid decompression, flight at high altitude in a reduced air pressure environment without the availability and use of supplemental breathing oxygen will result in Hypoxia (a.k.a Altitude Sickness), a medical state that can quickly lead to incapacitation and/or death. Hypoxia is basically a shortage of oxygen in the blood. As soon as we start to suffer from a shortage of oxygen at altitude, we will start a very dangerous 'clock' ticking which will determine how long you will remain conscious. This 'clock' can be renamed the Time of Useful Consciousness (TUC.) According to Doctor Paul W. Fisher, Ph.D., '....TUC is the period of time from the interruption of the oxygen supply or exposure to an oxygen poor environment, to the time when useful function is lost. The individual is no longer capable of corrective and protective action. It is not the time to total unconsciousness.'

For an individual of average health sitting at rest in a cockpit or cabin may see their TUC to correspond to the following table:



FL500 and above

<9 seconds


9 to 12 seconds


15 to 20 seconds


0.5 to 1 minute


1 to 2 minutes


2.5 to 3 minutes


3 to 5 minutes


10 minutes


20 to 30 minutes

A rapid decompression can reduce the TUC by up to 50% caused by the forced exhalation of the lungs during decompression and the rapid rate of ascent in cabin altitude. The symptoms of Hypoxia include: a feeling of apprehension, headache, dizziness, fatigue, nausea, hot/cold flashes, blurred vision, tunnel vision, tingling, numbness, an increase in both the depth and rate of your breathing, mental confusion, poor judgement, loss of muscle coordination and unconsciousness. People who are out of condition and people who smoke will be affected by Hypoxia much faster than their healthy, non-smoking colleagues.

So how can you prevent you and your fellow crew members and passenger's injury or demise at the hands of Hypoxia or Narcosis? Well first it is extremely important to make certain that your pressurization system is functioning properly. Follow all of the operating and maintenance procedures specified for your system and in addition to keeping a parameters 'trend' log for the cabin differential, like you do for your engine parameters, which you provide to your maintenance personnel, make sure that your aircraft is periodically 'blown-up' (ground pressurized by a 'Huff' Cart) and physically inspected for leaks using either soap and water, 'owls fluid' or other means. Don't just rely on a ground check using engine bleed air or the engine gearbox driven compressors to verify the integrity of your aircraft's cabin pressure vessel. Additionally have your technical people keep a close eye on the condition of your windows to make sure that they catch a potentially catastrophic delamination or failure before it occurs. Obviously it is also vital that you regularly check your oxygen delivery system as well. Fortunately this is often incorporated into your aircraft's maintenance schedule; however it is believed that a 'turned-off' oxygen bottle main valve was a contributing factor in the Payne Stuart accident. If you can't don (put on) your oxygen mask and start sucking a lungful of O2 in less than 5 seconds, you had either better practice this procedure with a friend who has a stopwatch, or it is time to buy new masks and hoses that allow 'quick donning.' Now that you have done everything in your power to ensure that your aircraft and its equipment are up to the rigours of high altitude flight, you will serve yourself well to arrange a ride in a Hypobaric Chamber (Altitude Chamber) so you can experience first hand, under close professional supervision, the effects of Hypoxia on your own body so that you are better equipped to recognize your own symptoms thus allowing you to possibly react quicker to making the necessary environmental changes necessary to save your life. Your local FSDO or AME can recommend a location where you can experience this.

So keep your cabin altitude below 10,000 feet, keep your wits about you, and most importantly keep the shiny side up!

As this is a very important issue with any stage of piloting skills please share any experiences you may have had with either Narcosis or Hypoxia.  Your learning curve with experience will help all others without.  Please click on the link below which states "Reply to this Article", your thoughts and comments would be very much appreciated.  Until next month dear readers.

Aviation's 709 Ride

by Greg Reigel 1. February 2007 00:00
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Aviations "709 Ride" What happens after the aircraft accident or incident.

© March, 2007 All rights reserved.

What happens if you are involved in an incident in which your aircraft is damaged, but no one is injured, other than perhaps you and your pride? For example, you forgot to put the landing gear down and you landed your aircraft with the gear up or you didn't put in enough wind correction and you and your aircraft ended up off the runway. Well, if the FAA finds out, you will quite possibly receive a letter demanding that you appear for the dreaded "709 ride" (formerly known as the "609 ride" under the Federal Aviation Act of 1958).

What Is The 709 Ride?

The 709 ride refers to the FAA's authority to re-examine an airman holding a certificate (pilot, flight instructor, airframe and powerplant etc.) at any time pursuant to 49 U.S.C. 44709(a). The FAA issues a request for re-examination to an airman after it discovers evidence that leads it to question an airman's qualifications to exercise the privileges of the airman's certificate. Incidents such as the two examples above involve circumstances that very well may lead the FAA to question an airman's qualifications.

But what if the accident or incident was not the airman's fault. What if the accident or incident was caused by a mechanical failure? Unfortunately, unless the mechanical failure is obvious to the FAA as the sole cause of the incident, a request for re-examination is likely to be considered reasonable. Why? Because the FAA only has to show that a lack of competence "could have been a factor" and, if it was, the re-examination request is considered reasonable, without regard to the likelihood that a lack of competence had actually played a role in the event.

According to FAA Order 8700.1, Volume 2, Chapter 26, "there must be ample or probable cause for requesting the reexamination" including reliable reports, personal knowledge, or evidence obtained through an accident, incident, or enforcement investigation. Thus, the "lack of competence" has to be supported by the facts and circumstances in the case. However, as long as a basis for questioning an airman's competence has been implicated, rather than actually demonstrated, the request is considered reasonable.

The Re-Examination Request

The procedures for the 709 ride are set out in Order 8700.1. The Flight Standards District Office ("FSDO") responsible for the area within which the accident or incident occurred will send the airman a letter requesting re-examination, via certified mail, return receipt requested. The letter will include (1) the reasons for the re-examination; (2) the specific certificate and/or rating for which the re-examination is necessary; (3) the type of re-examination; (4) the category and class of aircraft required (if applicable); (5) the location of the re-examination; and (6) a time limit for accomplishing the re-examination.

After the airman receives the letter, the airman usually has 15 days within which to complete the re-examination, although this is not always the case. If an airman was injured in an accident and his or her physical condition precludes completion of the re-examination or if the airman needs more than 15 days within which to practice/prepare for the ride, the re-examination may be postponed. Under these circumstances the FAA will require that the airman surrender his or her airman certificate and the FAA will issue a 30-day temporary certificate for the airman to operate under until the re-examination.

If the FAA believes the airman will be operating commercially while carrying passengers, the FAA may demand that the re-examination occur within less than 15 days. In this situation, if the airman is unable or refuses to submit to the re-examination within the time specified, the airman may surrender his or her certificate and obtain dual instruction from a certificated flight instructor in preparation for the ride or, if the airman finds it necessary to conduct solo practice, the FAA may issue a temporary airman certificate, valid for 30 days instead of 120 days bearing all ratings previously held by the airman. However, in the latter situation, the ratings for which the airman is to be re-examined will have the limitation "For Student Pilot Purposes Only-Passenger Carrying Prohibited".

It is important to note that an airman who wants to surrender his or her certificate should not simply show up at the FSDO and hand it over. If the certificate is to be surrendered, it should be accompanied by a letter in which the airman confirms that the certificate is only be surrendered on a temporary basis and that the airman reserves all privileges, rights and remedies with respect to the certificate and any potential adverse action the FAA may decide to take. An aviation attorney can help to draft this letter and/or assist with the logistics of the surrender.

The 709 ride does not necessarily have to be scheduled with the FSDO that issues the request. If the accident or incident occurred somewhere other than the airman's home area, the airman can request that the re-examination be administered by the airman's home FSDO. In this situation, the airman's home FSDO would contact the FSDO issuing the letter requesting the re-examination and coordinate with that FSDO on the tasks to be re-examined and if any further enforcement action is necessary after the actual ride.

If the airman fails or refuses to submit to a reexamination within a reasonable period of time, the FAA will initiate emergency enforcement action to suspend the airman's certificate. Although the airman has the ability to respond to or appeal the emergency suspension, if the FAA has a reasonable basis for the request and the airman has no other defenses, the airman will likely end up with a suspension of his or her airman certificate pending submission to and successful completion of the re-examination.

What Happens During The 709 Ride?

The re-examination is similar to a check-ride, except that the airman is not typically subject to examination on all of the required tasks in the practical test standards ("PTS") for the certificate upon which the airman is being re-examined. Rather, the re-examination involves the tasks that were called into question by the occurrence of the accident or incident and it is conducted in accordance with the PTS for the certificate or rating involved. The tasks may include components of the knowledge test, the skill or flight test, or both.

The inspector can fail the airman for any maneuver, procedure or knowledge deficiency in which the airman is found to be unqualified. This includes any of the specific task upon which the airman is being re-examined. Additionally, if the inspector observes any deficient areas other than those that are the subject of the re-examination at any time during the re-examination, those deficiencies could also be the basis for failure of the test.

If the airman successfully completes the re-examination, one of two things will happen: (1) if the airman's certificate was suspended pending completion of the re-examination, the inspector will issue a letter of results and may issue a temporary certificate that bears all ratings and limitations from the original certificate; or (2) if the airman's certificate was not suspended pending completion of the re-examination, the inspector will simply issue a letter of results and the airman may then continue to exercise the privileges of his or her certificate and/or ratings.

If the airman fails to successfully complete the re-examination, the inspector will inform the airman in detail of each deficiency. Additionally, if the airman's original certificate was surrendered in exchange for a temporary certificate and the term of the temporary certificate has time left on it, the inspector will decide whether to suspend the certificate or to extend the temporary certificate for an additional 30 days. In the latter instance, if the inspector believes the airman could successfully complete another re-examination if he or she obtained additional instruction, another 30-day temporary certificate will be issued with a limitation against carrying passengers. The airman will then have to submit to an additional re-examination within that 30-day period. In the first instance, when the inspector determines the airman is not qualified to hold the certificate or rating, the airman can expect to be the subject of enforcement action seeking revocation of his or her certificate and/or ratings.


If you are involved in an accident or incident in which pilot error is a possible cause of the accident or incident and the FAA finds out, don't be surprised if you receive a certified letter requesting that you submit to re-examination. The first thing you need to do is review the scope of the re-examination request and objectively determine whether the FAA has a reasonable basis for making the request. Often, it will.

Next, you need to decide how you want to respond. Although the request for re-examination can be intimidating and frustrating, especially if it follows an accident or incident in which your aircraft and/or your pride has been damaged, it is possible to treat it as a positive experience and use it as an opportunity to improve your skills as an aviator. This is especially true if you take the ride with an inspector who approaches the situation from a similar perspective.

However, if you find yourself facing a 709 ride with an inspector who does not approach the ride from this perspective or if you have questions regarding the basis for the request or the procedures that should be followed, an aviation attorney can certainly assist you in the process. After all, you worked hard to obtain your certificate(s) and/or rating(s). Make sure you protect your ability to exercise those privileges and to fly safely. Have you ever had this experience? Comment on this article. Our readers and myself would like to learn more from those who have had to go through it.


If you have had the "709 Ride" please offer us your experiences.  We all learn from each other and knowing the do and don'ts to an at best "bad" situation will help all.  To submit you experiences or question please click on the "Reply to this Article" link below

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Greg Reigel

Return on Aircraft Investment

by David Wyndham 1. February 2007 00:00
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When working with our clients on fleet-planning, we almost always look at several forms of ownership and at several ways to pay for the aircraft. Often, we compare a loan with cash purchase. On the surface, the loan should cost more, right? After all, you pay interest on the amount borrowed. That's not quite the full story.

Whether your company is a sole-proprietorship or a Fortune 500, there is always a limited amount of money. Successful companies keep a close control on their cash and look at something called "return on investment" or ROI. Depending on the context used, this term can also be called the "hurdle rate" or even "cost of capital."

One way a large company uses its cash to invest in items that generate income. Unless the aircraft is used for hire it does not directly generate income any more than the computer I am using to write this article directly generates income for our company.  If a company buys an aircraft for cash, it is cash that they cannot put into something that directly generates income.

As an example, Widgets International Inc. needs an aircraft to better manage their far-flung widget manufacturing plants. They can buy a business jet for $13 million, or they can upgrade a widget plant for $13 million, increasing their net profits at that plant by 15%. The widget company will evaluate whether to put their money into the aircraft, or the plant. That 15% increased profit can be called their Return On Investment.

Let's assume that the bank is willing to loan the widget company money at 8%.  The widget company can use their cash to generate income at fifteen cents for each dollar and it will "cost" them only 8 cents on each dollar loaned. In an over-simplification, the company will make 15 cents at the expense of eight cents in interest for a net of seven cents.

If our fictitious Widgets International Inc. were acquiring an aircraft, they most likely would not pay cash, but instead take out a loan and "invest" the cash somewhere within the company where it could earn returns greater than the cost of the loan.

Large companies typically try to generate fifteen cents or more (on average) for each dollar spent.  That amount is their ROI.  When evaluating a large purchase, a company applies ROI to the purchase to see if that is the best use of their capital. Using this sort of calculation enable them to spend their money in the most productive ways. This is not done for every acquisition, but is usually required of large capital acquisitions.

Of course, there in never a guaranteed return in business. So the company has to access the risk of being able to get the return along with the magnitude of the return. Acquiring an aircraft for business use involves a careful consideration of the expenses, and whether it is better to pay by cash, a loan, or even to lease.

The calculations can be complex. Along with the tax implications, there is the impact on the balance sheet (see your CPA on that one). However, for many large companies, it does not pay to buy for cash.

Since there are many ways and forms to handle the ROI on an aircraft or cash investment what are some of the ways your company has handled this.  This is an interactive article so we would like to have your suggestions or comments on this article.  Please click on the link below "Reply to this Article"


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