Saturday, December 22, 2007


Aircraft wings and tails have forever been the collectors of enough ice to make them quit working like wings and tails. All it really takes is visible moisture, a cloud for example, and temperatures that approach freezing. The movement of the metal surfaces through the air is often enough to lower the temperature below freezing so even outside air temperatures above freezing will allow enough ice to form to give plenty of aerodynamic trouble.

Aircraft manufacturers have historically used de-ice devices to deal with ice, at least enough of it to satisfy the FAA’s paltry requirements to certify an aircraft for flight into “known icing conditions”. De-ice devices concede that the manufacturer will allow the aircraft to accumulate ice before activation is supposed to shed the ice, hence the term de-ice.

De-icing devices are typically rubber boots that inflate to break the ice off. The inflation pressures are supplied by an engine driven vacuum pump, bleed air taken from the compressor section of turbine engines or separate pumps electrically driven. Engine driven vacuum pumps have proven to be prone to failure just when they are needed most because of heat, sudden demands that fail their internal carbon blades, general deterioration or contamination just to name a few of the many reasons for un-annunciated sudden failure. Bleed air drawn from the compressors of little turbine engines is often not enough to completely inflate the boots, the air can often becomes contaminated with moisture and causes ice to form in the inflation tubes, and bleed air drawn from the compressor means less air for the engine to develop the necessary power to climb out of icing conditions or even to provide cabin heat.

Electrically driven air pumps is clearly the better idea because the pumps are single purpose and can supply full inflation pressures regardless of aircraft altitude, cabin heat requirements or moisture.

All of these systems share the same problem. They are designed to remove ice allowed to accumulate rather than preventing its accumulation. It is the accumulation of ice that has proven to be the undoing of many pilots and their aircraft because the manufacturers have hidden a very important fact. They don’t work effectively in the icing conditions that these airplanes regularly fly in and that most pilots think are safe to fly in. None of the federal agencies have taken strong action but there has been talk for decades about the problem. Nonetheless people continue to die each icing season.

Most deicing boots cover less of the airfoil than is required to remove dangerous accumulations of ice. Most deicing boots are impacted by the lack of adequate inflation pressure especially at altitude or with cabin heat on, and many deicing boots will accumulate moisture that will affect the amount of inflation. Couple this with some very unforgiving airfoils that have sharp stall characteristics and the use of deicing boots for known icing certification can be disastrous.

Federal authorities have been uniform in blaming pilots for icing accidents. Clearly these blame merchants are either not pilots, or have never flown in the clouds in the winter. Icing is unpredictable and even when forecast occurs only forty percent of the time. To blame a pilot for a crash because he didn’t predict weather even the National Weather Service can’t get right seems unfair since for the most part pilots are unaware of the limitations of their deicing equipment as manufacturers have not been honest about the limitations.


Neither the testing nor the equipment was ever designed to permit continuous flight in moderate icing conditions. The regulations require it but the manufacturers do not test for it and the aircraft will not handle it. Not a believer, look at the accident reports. They are replete with pilots who cannot believe their multimillion dollar aircraft can’t handle continuous moderate icing, a question they no doubt carry to their deaths.

Even the manufacturers can’t agree with either each other or the Government about when to de-ice. Some say wait until three quarters to one inch of rime ice accumulates before activating the boots. Others say, no, activate boots at the first sign of ice. Some say wait for less clear ice to accumulate before activation and others say activate the boots when such ice is anticipated. Some say don’t activate the boots on approach because it will slow the aircraft by ten knots or so and other say use the boots continuously. Some say ice bridging occurs if you use the boots too soon and too frequently and others say that’s an old pilot’s tale, dead old pilot no doubt.

Some NACA five digit airfoils, widely used in general aviation and some smaller turboprop commuter aircraft grow ice aft of the boots just because of their angle of attack in flight. Some will accumulate ice aft of the boots at the highest point of lift at twelve percent cord and others will react violently especially when the ice accumulates on the horizontal tail. Some airplanes will suffer an ice-induced tail stall for which recovery virtually no pilots have been trained. It is opposite normal stall recovery and may not be recoverable at all.
The manufacturers of big airplanes, transport category airplanes, have long recognized that the use of deicing boots is not a safe solution for the demands of air carriers who may have to fly in ice for a long time. Years ago they abandoned de-icing boots in favor of anti-ice systems. As one famous aeronautical engineer from a well known manufacturer has said: “You could not expect de-icing boots to effectively remove ice from an aircraft that had to fly from Paris to New York much of it in icing conditions so we heated the leading edges of the surfaces instead so ice wouldn’t accumulate.”

Anti-ice as it is called is the only safe way to keep modern aircraft safe in icing conditions. Heating the leading edges of the aerodynamic surfaces is the best way. In turbine aircraft, bleed air from the compressor of the engine is routed though the leading edges. It heats stainless steel strips and they will not allow the accumulation of ice. This requires lots of bleed air and that robs the engines of power and increases fuel consumption. It requires much more power than is necessary for the flight itself and typically is found in larger more powerful aircraft although it is also used in regional jets and many executive jet aircraft but sadly not all. Requiring more power means more expense to buy, greater expense to operate but greater safety is the prize. Other anti-icing options include, weeping wings which bleed glycol or other anti-icing fluids through tiny holes in a mesh leading edge, and electrically heated leading edge devices. The electrically heated leading edge devices will become more and more prolific once low weight high power electrical generators are introduced currently being developed for the newest transport category airliners.

Fortunately for jet operators, much of their flying time is above the weather including icing conditions but as many of the very light jets compete for scarce airspace and air traffic delays due to bad weather become more common, these low powered mostly de-icing equipped jets will suffer from accidents due to the limitations of this equipment. The propeller driven piston powered airplanes are simply doomed to suffer accidents in icing conditions because “certified for flight into known icing conditions” is a cruel hoax for which they are clearly ill-equipped. Small turbine propeller driven aircraft are equally hexed because their tiny engines just don’t have sufficient bleed air to do the job to inflate the boots under the most demanding of flight conditions.

The answer is straightforward. First, the Federal authorities must get their acts together and make a sensible realistic definition of “known icing conditions”. Second, the Federal authorities must ensure that manufacturers comply not only with the letter of the law but also the spirit of the law. If a manufacturer anticipates as it should that a “known icing” certified aircraft will be flown in lots of different icing conditions then it must ensure the aircraft will do it safely. Today that is not so. Third, the Federal authorities must mandate that all aircraft with a “known icing” certification be equipped with anti-icing equipment sufficient to prevent the accumulation of ice and that all power plants have sufficient reserve power to effectively operate this equipment. Fourth, the Federal authorities must carefully review prior known icing certifications and monitor new ones to ensure not that the aircraft meets the letter of the law but that it will be safe to fly in all reasonably anticipatable icing conditions. Under no circumstances should Federal authorities be allowing manufacturers to rewrite their flight manuals after certification to accommodate the reality of accidents in airplanes that never met the requirements in the first place.

Safe flight in icing conditions can’t be the luck of the draw, it must be totally predictable, repeatable and without chance. The only thing manufacturers have control over is to design and build in the capability of an aircraft to safely fly in icing conditions. A higher authority has control over the existence of and the severity of icing conditions that are likely to be experienced. Given man’s control over the former and his lack of control over the latter it is incumbent upon him, and well within the technology, to ensure that emergence safely from the latter is guaranteed.

Icing season 2007
Arthur Alan Wolk

Monday, October 22, 2007

NASA Deep Sixes Important Aviation Safety Information

NASA spent $8,500,000 of our money to study aviation safety the right way: interview pilots in strict confidence so they could disclose what they see as critical safety failures in our aviation transportation system. Now NASA, instead of releasing the information which shows that the FAA is totally inept at gathering safety information, has ordered the contractor to destroy it because it would be embarrassing to government and the airlines.

This stonewalling of public information obtained in the ordinary course of its duties is unforgivable and a disgrace. The data shows that the FAA is totally in the dark about aviation safety and could benefit from this NASA data because it would demonstrate how and why the FAA doesn't have a clue what's going on in the National Airspace System.

The reason no one talks to the FAA is obvious. The FAA will prosecute anyone from whom it receives information that relates to safety of flight even if the purpose of the disclosure is to improve safety. Moreover the FAA totally discounts information from the field about safety defects in aircraft so mechanics and pilots are loathe to report troubling problems as no action is ever taken. In addition, the FAA rats out the whistleblowers and gives them no protection, hanging them out to dry, to lose their jobs and to go it alone. Therefore, there is no incentive whatsoever to help the FAA.

NASA, on the other hand, gives a "get out of jail free card" with the report of sensitive safety information so there is an incentive to provide timely and helpful information that can be useful in preventing accidents. What is troubling about this revelation, however, is that a serious effort was made by NASA due to a perceived aviation safety need to get up close and personal so it could acquire the most useful data and now it will “deep six” it because it would embarrass another agency of government – the FAA – that agency being solely responsible for the safety of flight. In short, instead of using this information as a tool to improve the FAA, the most ineffective agency of government, NASA sees fit to destroy the information instead. Hide critical information that might be embarrassing to the government? Never!

Arthur Alan Wolk
October 2007

Thursday, August 23, 2007

Air China Boeing 737 Exploding Center Fuel Tank – It’s Déjà vu of TWA 800

An Air China Boeing 737 Next Generation airliner recently pulled up to the gate, caught fire, and moments after the passengers deplaned through emergency exits, the center fuel tank exploded and destroyed the aircraft.

Had the explosion occurred just minutes before, all 152 passengers would most likely have been killed. The TWA 800 explosion brought home a well-known fatal flaw in transport category aircraft – large fuel tanks harbor fuel vapors that can explode and kill people. The problem has been well known for 45 years. The military long ago addressed it by putting fire suppression safeguards in large aircraft fuel tanks. Nitrogen inerting of the fuel tank is the preferred method and is effective, although passing cabin air through the tanks to lean the air and purge fuel molecules is another method.

Nitrogen inerting systems are supposed to be installed in new aircraft but either the system didn’t work, the aircraft didn’t have one, or other factors that need further investigation allowed an explosion to occur. The bottom line is simple. FAA predictions that center fuel tank explosions would be unlikely, with only four predicted over the next fifty years are obviously bogus, like all other FAA predictions. Inerting the fuel tanks of all transport category airplanes is vital unless we are prepared to assume the human and economic costs of hundreds dead.

Today, new fuel tank inerting systems that manufacture their own nitrogen from air weigh only a few hundred pounds. They can be retrofitted and eliminate this problem that has already taken a thousand lives. When technology is available to prevent death in aviation, it is immoral to allow bureaucratic inaction and industry stonewalling to assume this risk flight after flight. The FAA needs to act now!

Arthur Alan Wolk
August 2007

Tuesday, August 14, 2007

NASA - Do Not Risk the Crew Again - Fix the Shuttle!

NASA still doesn't get it. After spending a billion dollars on fuel tanks for the space shuttle it still doesn't accept that the foam that insulates the tank must not be permitted to peel away during lift off. Light as it is, the foam travels at such high velocities that it causes damage as if it were an artillery shell. In spite of the Columbia disaster that took seven lives and a stand down of a year for modifications to the tank, foam still peels off at every launch, does damage to the shuttle and risks the crew on re-entry,” said Wolk.

Now, the damage is very severe and try as it can to put a happy face on it, the damage to the shuttle's thermal tiles goes right to the structure and the risk to the astronauts is serious. The debate going on publicly at NASA is whether to have a spacewalk to repair the damaged tile. JUST DO IT!!!

It's one thing to let bad engineering create a risk of death time after time, it is another to fail to exhaust every possible remedy before the searing heat and turbulence of re-entry. The astronauts should be given every opportunity to survive but the people at NASA responsible for this continuing debacle need to go.

August 14, 2007

Sunday, July 22, 2007


Gus Fossum was a simple guy on a mission.
Raised on a farm in Minnesota, he never attended high school – while still a teenager in 1924 he went to the city to study automobile engines. He wanted to become an Army pilot, but obeyed his father and instead moved to Los Angeles in 1927. He studied aircraft mechanics in 1929-30 while owning and operating an auto garage (1928-1942). He owned several planes and flew often, including over the 1932 Olympic Games. In 1943 he joined the Navy and spent the war in Hawaii preparing planes for battle.

After WWII he spent the next 25 years working for aircraft companies, including Northrop and General Electric, as an inspector. Over the years he constantly was thinking of ways to improve on the things he knew. He wanted to forever end the dreaded killer of so many in aviation – carburetor ice.

Carburetor ice has been a problem since airplanes were first invented, and even today is the most frequent cause of unexplained engine failure. It has been studied for generations, and some innovative fixes by some brilliant engineers have been proposed, but none implemented by General Aviation manufacturers. Teflon coating of the throttle plate and venturi was proposed by the Canadians after their tests showed virtually ice free operation. The Teflon simply won’t allow ice to stick. The cost to implement this was $1.50 per carburetor. It never happened. Others have proposed fuel additives to prevent ice formation, and still others have recommended that all carburetors be equipped with ice detectors so a pilot won’t have to guess if his loss of power is due to carburetor ice or some other cause.

But only one invention, Gus Fossum’s invention, puts an end forever to carburetor ice and all the injuries and deaths that have come from it. Gus designed, built, and installed in his airplane a prototype small updraft carburetor, the kind that Marvel Schebler and now Precision have built since the 1940s. He carefully machined oil channels in the casting, throttle plate and throttle plate shaft so hot engine oil would constantly warm the carburetor and prevent the formation of any ice. At his own great expense of time and money, he obtained patents for the device in 1975 (3,916,859) and in 1979 (4,169,442). Manufacturing costs would have risen slightly, but in production this remarkable innovation would have resulted in a negligible increase in cost. Gus tested his amazing invention, and then tried desperately to sell the concept to aircraft and engine manufacturers. While none denied his invention was not the cure that Gus proudly proclaimed it to be, not one manufacturer would entertain the idea of using it. Gus Fossum’s invention is still not being manufactured for any aircraft – and carburetor ice deaths and injuries continue unabated.

Gus Fossum died in 1999 before his dream of improving aviation safety by eliminating carburetor ice from the litany of causes of aircraft accidents was realized, but he should not be forgotten. It takes a courageous man to put his reputation and skill on the line, face off multi-billion dollar aircraft and engine manufacturers and show them the way to save lives and them from their own product liability exposure. They didn’t listen, but we should. The Gus Fossums of this world make it a better place. His widow Helen, now 94, and family savor the memory of the simple man who just wanted to help keep everyone safe in the aviation field he loved so much.
Rest in peace, Gus.

Arthur Alan Wolk
July 2007

Friday, June 22, 2007

New Airworthiness Directive on Cessna Caravan Vindicates The Wolk Law Firm's Warnings on Known Icing

In a stunning reversal the Federal Aviation Administration has issued AD 2007-10-15 on the Cessna Caravan.
Icing wind tunnel research commissioned by The Wolk Law Firm in connection with the case of Randolph vs.Cessna revealed serious flaws in the design and operation of the deicing system of that aircraft. Experts hired by Arthur Alan Wolk confirmed that the problems ranged from the choice of wing airfoil, design of the deicing boots, flaws in the design of the inflation hardware, inadequate stall warning, underpowered engine, and complete inadequacy of the pilot's operating handbook for safe flight into known icing conditions.

After a spate of icing accidents Cessna Aircraft Company, encouraged by the FAA and the NTSB revised the Pilot's Operating Handbook to prohibit the use of flaps when airspeed reductions occurred due to unshed ice accumulations.

One of the experts working for the Wolk Law Firm, Harry Riblet, a noted designer of general aviation airfoils openly criticized the Cessna, FAA, and NTSB action and wrote to them repeatedly warning that use of the flaps could help but not cure the controllability problems with the airplane when flying in icing conditions. Riblet was ridiculed by the Government and Cessna even though his airfoils adopted for use by homebuilders around the world had proven themselves stall spin proof.

This Airworthiness Directive, with the full force and effect of law, now removes any restriction for the use of flaps in icing conditions and instead requires their use when the aircraft airspeed is reduced to 110 knots or less. It also prohibits the flight of the aircraft in moderate icing conditions for which the aircraft was originally certificated and removes the words "certified for flight into known icing conditions" from the handbook without revoking the certification entirely.

The AD requires installation of a low speed warning in all Cessna Caravans and cautions pilots that the stall warning may be completely unreliable in icing conditions.

What is remarkable about the Airworthiness Directive is what it doesn't do.
  1. It does not revoke the "known icing certification" of the Caravan which means it may still be dispatched into conditions where ice is reported or forecast.
  2. It ignores the fact that moderate icing is unpredictable so it may still not be possible for pilots to safely exit those conditions.
  3. It ignores the bad design of the deicing boots and does not require the introduction of a water separator into the system to prevent ice boot inflation line icing.
  4. It does not require that all Caravan pilots be taught how to recognize and recover from a tail stall.
  5. It does not require the installation of vortex generators on the boots of the wing and the horizontal stabilizer to delay the onset of ice induced stall.
  6. It does not require Cessna to install a stall warning indicator that is impervious to ice induced errors.
  7. It defines moderate icing encounters as a reduction in airspeed to 120 knots in cruise flight which is already in most instances a state beyond which the aircraft will be recoverable once control is lost.
  8. It further defines moderate icing as an accumulation of 1/4 inch on the wing strut which is the amount of ice accumulation Cessna requires before operation of the deicing boots in the first place even in light icing conditions.
What this AD demonstrates once again is the FAA does not understand yet the aerodynamics of the Cessna Caravan but had to do something to stem the constant series of ice related accidents with these aircraft. Instead of doing what's right and what's needed, it granted Cessna yet another reprieve at the expense of safety. More will die or be maimed next winter but hopefully this is a start to the end of this battle.
View wind tunnel test.

Tuesday, May 22, 2007

Change to Advisory Frequency Approved

These few words mean so much and are so misunderstood. When Air Traffic Control utters these words while a pilot is conducting an instrument approach to an uncontrolled airport or one where the tower is closed what it means is that it's okay for the pilot to change to the airport advisory frequency to announce his intentions to land and to caution other aircraft that might be in the traffic pattern or waiting to take off that an aircraft is on the instrument approach.

The idea behind this phrase is great. In this fashion other aircraft that might be operating under visual flight rules (VFR) should be on the lookout for an aircraft emerging from the clouds on final and give way. They might also announce their presence on the frequency so the pilot on the instrument approach will be aware of their presence and look carefully to avoid them when and if he breaks out of the clouds during the approach.
Therein lies the rub. It is possible that the pilot on the approach will fly his aircraft to minimums, like 200 feet above the ground before he looks out to see the runway environment. At that point it's too late to see and avoid the other aircraft and the hazard of a collision with an airplane operating under technically legal VFR is possible.

But that isn't the only risk and this one is the worst. Often when the controller approves a change to advisory frequency, all too often the pilot switches his primary radio to the advisory frequency without tuning in approach control on the second radio and turning up the volume so he can listen on both radios. Why does this happen so often? Because the pilot is concerned that he won't be able to hear aircraft on the advisory frequency responding to his call in the blind or that he will not hear their calls in the blind confused instead by the chatter on the approach control frequency.

What some pilots don't understand is that approach control radars have a low altitude alerting feature that is customized to instrument approaches at that airport. In short, it flashes the data block and sounds an aural alarm to the controller should the aircraft on the approach deviate from the establish approach parameters of safety. This occurs even after the frequency change and until the instrument flight plan is closed. The controller is then obligated to give a low altitude alert that goes something like: "November (AIRCRAFT NUMBER) low altitude alert, check your altitude immediately!" Now this is one great safety feature because if the pilot is concentrating on the approach and perhaps misses an "off" flag on his instruments, follows a false glideslope, has a sticking or lagging altimeter, or just loses his concentration, that nagging controllers' voice can be a wake-up call that saves lives. If given timely, the proper response is to check ones' descent, execute a missed approach if necessary and sort things out instead of crashing into the terrain below.
The pilot can't do this if he has either failed to insert approach control's frequency in his second radio or doesn't have the volume up loud enough to hear the alert. This simple oversight has prevented the avoidance of many accidents.

When on an instrument approach lots of stuff is going on. With the advent of GPS, WAAS and who knows what next, the pilot workload has been increased not decreased. This alert feature which has been around for years and ignored too often by controllers and missed by pilots can make a huge difference. In most accidents we have investigated, the controller gives the low altitude alert and only talks to himself because the frequency has already been changed in the primary radio by the pilot. Sometimes the alert is given too late because controllers ignore them due to too many false alerts. The result is often a crash. Everyone makes mistakes so tuning the other radio to approach while monitoring the advisory frequency can save your life. DO IT !!!!!

Arthur Alan Wolk
May 2007

Note: The term VFR means the operation of an aircraft under "visual flight rules" ie. the FAR's. Some time ago the FAA began to use the acronym VMC, "visual flight conditions" to describe what we pilots knew for an eternity as VFR. Those of us pilots old enough know that VMC is the FAA's acronym for "velocity minimum control" and has to do with the velocity below which a twin engine aircraft will no longer maintain directional control if the critical engine fails on takeoff. The constant changing of well known acronyms by the FAA brings to mind one that most pilots would like to have implemented with regard to the FAA's continued existence. Its known as DOA.

Thursday, February 22, 2007


On January 18, 2000, the Chairman of the National Transportation Safety Board, decried the publishing on Dateline ABC of portions of the audiotape from the cockpit voice recorder of the Cali, Colombia American Airlines crash in 1995. On that audiotape were communications among the flight crew that clearly show that they had violated the requirements of any sensible operation of the aircraft, and demonstrated further that they had no situational awareness certainly necessary for flying in mountainous terrain.

The Chairman said that Congress put restrictions on the use of CVRs for the "advancement of air safety." Nothing could be further from the truth, and the Chairman should investigate further before making such statements, which mislead the public.

The reason Congress restricted the release of the cockpit voice recorder tapes was because it was lobbied by the pilots' union after the release of cockpit voice recorder tapes from other accidents showed that supposedly professional flight crews were violating all of the rules of common sense in the operation of aircraft at critical times during the flight and immediately preceding accidents. Cockpit voice recorder tapes that were publicized revealed that pilots were talking about women, cars, sex acts, and the like at critical moments of the flight and not paying attention to their flying duties, which resulted in tragic accidents and loss of life. This was extremely embarrassing to the airline industry, to pilots who were members of the pilots' union, and to the Federal government because no one was enforcing the sterile cockpit rule which precludes any non-pertinent conversation when the aircraft is at 10,000 or below.

The enactment of the cockpit voice recorder restriction statute had nothing to do with safety, the enhancement of safety, or anything related to safety. It had to do with embarrassment, and depriving the public of the right to know what was going on in the cockpits of airliners which they thought was strictly business.

Rather than enhancing safety, or being designed to enhance safety, the Bill to which the Chairman of the NTSB refers has worked exactly the other way. Exposing non-pertinent conversation and the ineptitude of pilots causes public awareness, public discussion (among pilots, too), and will result long-term in the enhancement of safety, rather than keeping it secret and having nobody know what really happened in the cockpit.

The law should be changed and the NTSB should be better informed as to what lobbyist it was who got the law passed in the first place.

Friday, January 26, 2007


In a bizarre twist the NTSB, never at a loss for confusing the causes of accidents with how much it can do for aircraft manufacturers, has suggested that pilot training needs improvement to handle double engine failures at altitude.

First, double engine failures on multi-engine airplanes are illegal if a common cause can result in failure of more than one engine. In short, the airplane should never have been certified as airworthy if this could happen.

It turns out that some jet engines at high altitude, high power settings and cold temperatures can lock up and refuse to restart. This is not only a violation of the certification regulations for the engines, but also of the airplane if both of them in a two engine airplane can do the same thing at the same time.

Instead of coming down like it should have on the manufacturers of the engines and airplanes, the NTSB has instead recommended that a multi-disciplinary panel of experts be convened to discuss improving pilot training. That training already exists! It's called glider training because when two engines quit in a two engine airplane, the pilots are flying a glider!

What airplanes and engines are the NTSB referring to? The regional jets that increasingly carry more passengers to their destinations than the "real airplanes" that we used to fly in.

This NTSB recommendation, which ignores the seriousness of this life threatening problem and does not address its cause, is irresponsible.

My recommendation is that when both engines quit and you can't restart, the crew should thank the NTSB and the FAA for failing to exercise their legal obligations to protect those who fly in aircraft.