Cessna 208 Caravan Needs Critical "Known Icing" Improvements
Airplane not suitable to fly in any icing conditions
The Cessna 208 is a marvelous airplane for carrying lots of people and heavy cargo, but only in good weather. Flown in icing conditions the airplane is dangerous and has crashed thirty times, and nearly crashed many more. The NTSB has designated curing its dangerous history of accidents Public Enemy Number One. Nine people have been killed this icing season so far, and it’s only half over.
We have represented several families whose lives have forever been changed because of the Caravan’s poor performance in even light icing conditions, conditions for which Cessna Aircraft Company (the plane’s maker), and BF Goodrich (the designer and maker of the deicing boots) have said the airplane is suitable. In fact, it is not. The Caravan should not be flown in any icing conditions, and some of the operators refuse to dispatch it into any known icing weather.
The problems with the Caravan are simple. It is underpowered and, in fact, it appears to have the lowest power to weight of any turboprop single. That means it cannot climb above the ice and thus avoid it before its aerodynamics are so compromised it suffers a drastic loss of performance and control.
It has too much parasite drag, meaning there are so many unprotected surfaces that when ice collects, it seriously and quickly degrades performance to dangerously inadequate levels.
It has deicing boots that are simply inadequate to protect the wings and tail so dangerous ice accumulations even when the boots are used properly, quickly and dangerously compromise control and thus safe flight. Often there is insufficient margins to exit icing conditions safely and climbing may be impossible due to low power.
The Caravan uses engine bleed air to operate the cabin heat and the boots. It has no separate pump to operate boots like some other turboprop airplanes and has no water separator to keep moisture that collects in the boot inflation tubes from freezing and compromising the boot inflation. The bleed air extraction, together with the loss of power from deployment of the inertial separator designed to keep ice from damaging the engine compressor, drastically reduces the already underpowered airplane’s ability to exit icing conditions.
The aerodynamics of the Caravan also play a role in its inability to safely handle ice. Its horizontal stabilizer does not have ice protection to the tip and the elevator balance horn is entirely unprotected. The tail provides an up force, unlike most others that provide a down force. Thus, the top surface of the horizontal stabilizer is critical. Ice on this surface causes a pitch up, loss of airspeed, wing stall, tail stall, and drives the center of lift on the wing so far aft that regaining control at any airspeed is questionable.
The failure of the FAA to understand the aerodynamics of this airplane is unforgivable given the repeated concerns expressed by the NTSB and its own knowledge of the problems reported by pilots in Caravan winter operations.
Recent Safety Recommendations by the NTSB about the Caravan bring credit on that agency’s understanding that “something is wrong here” and that previous blame on pilots for accidents beyond their control is unfounded.
The Caravan is fundamentally a good design for fair weather flying. It should have had anti-icing equipment, not deicing boots that by design allow dangerous amounts of ice to collect before shedding and leave lots of ice as a residual of their operation. The Caravan should have had a cantilevered wing, instead of drag producing struts and, if cargo pod equipped it desperately needed, pod anti-ice protection. The powerplant is in need of twice the horsepower for this mission, and elevator balance horn anti-ice protection is vital.
The Caravan can be fixed and, if it had been fixed when the FAA first started to investigate icing incidents and accidents shortly after the aircraft was introduced, the airplane might have been well suited today for the all weather operations it is touted by Cessna to be capable. It is not, and the Randolph, Fry and Silvey families have suffered horribly, as have then ten little girls who have been left fatherless.
The FAA and the NTSB must do better. Twenty years have gone by since the first investigations and still no positive and effective efforts to fix the airplane. It is clear that at least the FAA lacks the technical expertise or will to understand the aerodynamics of the Caravan. At this late date, after three separate safety investigations, the FAA still thinks the bottom surface of the horizontal stabilizer is the critical lifting surface. It isn’t!
It is also unfortunate for Cessna, who has had ample opportunity to fix the airplane, yet still denies it has a problem. This is litigation driven no doubt so, instead of fixing it and avoiding other accidents, other tragedies for the victims’ families and other lawsuits for wrongful death, it denies the problem that everyone, including the federal authorities, knows about, and allows more accidents and more claims. Aside from the moral bankruptcy of such a position, from a purely economic standpoint, it is inexplicable.
There is hope, however. Others recognizing the problem have started addressing it themselves. Weeping wing TKS retrofits are now available to provide anti-ice protection. Larger and more capable powerplants are being STC’d by others for the aircraft and even a hot wing anti-ice system is being tested. Hopefully these non-Cessna designed and built modifications will save lives, but must be purchased at substantial cost by operators of these aircraft.
The icing accidents and incidents involving the Caravan have reached intolerable levels. Something must be done and done quickly if others are to be saved. After nearly forty years litigating airplane crashes, it never ceases to amaze me that aircraft manufacturers won’t listen. Airplanes always telegraph their intention to fail long before they suffer a fatal accident. Fixing the airplane before the first accident is the least expensive means to reduce the cost of air crash litigation liability, and fixing it after the first accident will guarantee that there will never be a claim for the same defect after the payment of the first one.
- Arthur Alan Wolk