Anti-ice campaign heats up

As winter tightens its frigid grip, the National Transportation Safety Board (NTSB) wants the Federal Aviation Administration (FAA) to launch an icing awareness program for operators and pilots of the Cessna 208 Caravan aircraft. The single turbine engine high-wing airplane is used by small charter operators and by overnight freight, parcel and document-delivery companies.

The board raised potential problems with inadequate certification standards, to which the airplane was designed, but seemed to save its concerns on the design front for a later day. The NTSB is seeking seasonally expedited action to raise awareness among C208 operators and pilots. In its Dec. 15 letter to the FAA, the NTSB cited 26 icing-related Caravan accidents from 1987 to 2003, killing 36. Most occurred within the parameters of the icing envelope used for certification purposes (the well-known Appendix C). Ten of the 26 events involved inadequate removal of ice before takeoff. The NTSB noted that both visual and tactile checks for any ice on the upper surface of the high-wing airplane is difficult, but it is essential that such checks be done to make sure the wing is absolutely clear of ice.

The NTSB stopped short of suggesting that pilots add a few knots airspeed to account for the increased stall speed of ice-contaminated wings (see ASW, Nov. 8, and Nov. 15).

We asked John Dow, former FAA small transport department official and an expert on icing, to comment on this development:

"All the recommendations are procedural with no equipment recommendations, and all but the last reaffirm that the ultimate responsibility rests upon the shoulders of the pilot aided by the operator.

"In the event count listed, the on-ground icing accidents are sadly a smaller reflection of the hundreds of lives lost with larger transport category airplanes because of the failure to depart with a 'clean wing.'

"The transport airplane segment of the industry got the message on ground deicing and the record has improved. Now it is time for the small airplane pilots and operators to get the same message and apply the same level of care. Deicing equipment is available and the only thing needed to get up to the hands-on level of the wing and the tail of the Cessna 208 is a ladder or work stand. Yes it is cold and, yes, it takes time to run a hand over the airfoils and, yes, it costs money to deice. Accidents cost more in misery and money.

"Cessna 208 pilot information is well detailed with a minimum speed in icing. The dilemma facing the pilot is what happens when the airplane gets to that speed and cannot remain in level flight. It gets down to whether the pilot is ready to trade altitude to maintain airspeed and, in the worst case, make an off-airport landing. Landing right side up on a road or field with the potential for some damage, and even more paperwork, seems a better choice than dying upside down in a deep hole. This is a mindset issue. We need to think outside the airport at times! Pilots seem to be able to make the off-airport landing if the engine quits. Why not the wing?

"The Cessna 208 is popular because of its capabilities, but it is still a large single engine airplane and even with its 600-675 hp engine does not have the excess thrust of a twinjet and must be flown with care. This means the drag from even a little ice can reduce the service ceiling and ice or roughness above the stagnation line can reduce the stalling angle of attack.

"History has shown that the airfoil and pilot are not always in agreement on the amount of ice contamination. What looks good to the pilot may be deadly to the airfoil. The only thing that works is to be absolutely certain there is no ice on the critical surfaces before departure - period."

Dow's position reflects precisely the guidance, "Recommendations for De-Icing/Anti-Icing of Aircraft on the Ground," 19^th edition, issued September 2004 by the Association of European Airlines (AEA) - check by touch to make sure the wing is clean.

>> Dow, e-mail jdowsr@earthlink.net <<

Clean and Free of Frost

7.5 Final Check

A tactile check (by touch) of the treated areas and a visual check of the untreated areas of both wings shall be performed immediately before the aircraft leaves the parking position. These checks are conducted to insure that both wings are clean and free of frost. The applied de-icing/anti-icing fluid shall be liquid and shall show no indication of failure, such as colour turning to white, loss of gloss, getting viscous, showing ice crystals, etc.

Source: http://www.aea.be/aeawebsite/datafiles/deicing19-final.pdf