| | Salina, KS based CAV Aerospace, Inc. has announced the company will begin retrofits of Cessna 208B Caravan in early April. New production Cessna Caravans began receiving TKS upgrades in 2008, when Cessna Aircraft Company made the switch from pneumatic boots to CAV Aerospace’s proprietary TKS system. The retrofits in Salina will bring the existing fleet up to current ice protection standards.
The CAV Aerospace hangar in Salina, KS (KSLN)
“Caravan operators need safety and dispatch reliability. TKS provides both,” explains CAV Aerospace President, Kevin Hawley. He went on to say “The TKS system on the Cessna Caravan has set a new, much higher standard for ice protection. It’s easy for an already burdened flight crew to use and is the only ice protection system that provides runback ice protection aft of the leading edges.”
The runback protection Mr. Hawley referred to is the product of the TKS system’s unique design. The TKS system provides ice protection by pumping a freezing point depressant fluid from thousands of laser drilled holes in titanium panels on the leading edges of the aircraft’s wings, struts, horizontal stabilizers and vertical stabilizer. The fluid then streams along both the bottom and top of the airframe until it is carried off the trail edge.
TKS fluid runback on the Beech A36
The TKS system for the Cessna 208B holds 20.8 US gallons of TKS fluid which provide a maximum endurance of 3 hours 25 minutes. The system has 3 modes of operation, Normal, High and Maximum as well as a separate on-demand pump dedicated to clearing the windshield. A Backup mode provides an added layer of protection.
Operators of Caravans other than the 208B model are not without their own TKS option. CAV Aerospace President, Kevin Hawley, explains that “If it’s a Cessna Caravan, there’s a very good probability that we can provide a TKS system for it.” He goes on to say, “CAV Aerospace has delivered TKS systems for over 6,000 aircraft, from single engine pistons, like the Cirrus SR22, to business jets and even UAV flying in military environments. There is a great pride and no small amount of humility in providing the most effective ice protection for the aviation community.”
For more information on the ice protection systems offered by CAV Aerospace call 1-888-865-5511 or email tkssales@weepingwings.com
TKS Porous Panel Dripping - Why This is Normal
A common occurrence with all TKS porous ice protection panels is “dripping” when not in use. Specifically, panels will stream very small quantities in flight or drip while parked. This is a normal characteristic of a TKS system because of the porous panel design. This characteristic, and the following discussions are applicable to all TKS-equipped aircraft.
The included figure presents a typical cross section of a porous panel. Every panel contains a reservoir for fluid and a porous membrane. The reservoir and membrane work together to provide an even distribution of fluid over the entire porous area of a panel. The membrane is the key element, but it does not work properly unless fluid is supplied and distributed evenly to it. The reservoir provides that supply.
Figure 1: Typical TKS panel cross section.
The porosity of the membrane is designed and tuned to create a 3-4 psi pressure drop at 32 °F when ice protection fluid is forced through it. For general aviation class aircraft, the 3-4 psi value is far higher than any aerodynamic pressures encountered on the aircraft leading edges. The input pressure assures that a uniform distribution of fluid will pass through the porous panel regardless of airspeed and air flow angle (angle of attack).
The reservoir also assures that, when properly prepared, a relatively instantaneous supply of fluid is available at the panels for delivery. The combination of the reservoir and membrane are designed to retain the internal fluid volume as long as possible so startup time is kept to a minimum. In an inactive state, the panel is able to retain the fluid when the temperature is 32 °F or colder, due to the fluid’s viscosity.
As the temperature of the fluid warms beyond 32 °F, the viscosity drops. As an example, the viscosity of ice protection fluid at 70°F has roughly 1/3 the viscosity of 32°F fluid. With much thinner fluid, the membrane cannot resist and fluid will start to pass through.
This characteristic will be seen on the lower edge of the drilled active area of a panel, typically near the inboard end of the panel. The wing dihedral creates a small pressure head in the panel, the highest value being at this point. Fluid will slowly flow downhill in the panel reservoir, then weep from the lowest point. The effect is much more apparent on vertical stabilizer or lift strut porous panels.
This type of fluid loss from the panel is very low volume, but it can be deceptive to the user. In flight, the weeping can look very similar to normal operation on the inboard section of a panel. The thing to remember, however, is that the fluid loss is only from the panel reservoir, and it happens in warmer conditions, far above temperatures associated with icing conditions. It is difficult to quantify exact ranges, but temperatures above 60 °F is typically where this type of weeping occurs.
This is a normal characteristic for a TKS system. It is not a maintenance issue or a concern for normal operation. It does, however, point out the need to observe proper preparation of the system prior to flights where icing conditions may occur. If the panels have drained their fluid, it can take up to 5 to 10 minutes to fill the entire porous panel system. Proper observation of TKS preflight steps assure that the system will be ready and available when needed.
April Shows
Show season is starting and CAV Aerospace will be attending more events in 2010 than we have in years. The shows are an excellent opportunity to meet each other face to face and share our mutual enthusiasm for aviation. We look forward to seeing all of our long time friends and meeting new ones.
 March 29 - April 1
The use of the TKS system on UAV flying in military environments around the world, has always been a great source of pride for CAV Aerospace. We will exhibit at the Military Air Assets Exhibition & Conference from March 29th through April 1st in Jacksonville, FL. We can be found in booth 812.
 April 8-11
Kicking off the European season is Aero Friedrichshafen. We'll be showing a newly installed T182T inside hall A3 from April 8th through the 11th.
 April 13-18
We'll then be at Sun 'n Fun in Lakeland, FL. Our plan at this time is to show a TKS equipped Cessna Caravan 208B. You'll be able to find us in the manufacturer exhibit section, site MD-1.
See you there!
| | |
