Icing Training & Options

Aviation International News » December 2006
December 7, 2006, 9:15 AM

Part 25 aircraft likely to get more stringent icing rules

Next year, the FAA hopes to release a new rule that closes a gap between flight-in-known-icing certification requirements for Part 23 and Part 25 aircraft. Part 25 aircraft weigh more than 12,500 pounds, and more stringent requirements apply to their certification. In the case of icing, however, Part 23 has stricter requirements, that they be “capable of operating safely in continuous maximum and intermittent maximum icing conditions, as described in Appendix C of Part 25.”

Part 25 airplanes “must be able to safely operate” in the same conditions, but there is no definition of what “to safely operate” means. Part 23 regulations provide a clear definition: “‘Capable of operating safely,’ means that airplane performance, controllability, maneuverability and stability must not be less than that required in Part 23, Subpart B.”

“Generally, there are no big differences other than what it means to operate safely in icing,” said Gene Hill, FAA chief scientific and technical advisor for icing. The new regulations are the result of work done by the Aviation Rulemaking Advisory Committee Flight Test Harmonization Working Group.

Another committee–the Ice Protection Harmonization Working Group–sent draft proposed rule changes to update the Part 25 Appendix C icing envelope to the FAA in November last year, according to Hill. These changes would finally address types of icing that have been implicated in several accidents but which were not covered by certification rules, including freezing rain and drizzle in the form of super-cooled large droplet icing. It could take years for a new Appendix C icing envelope to be published.

In practical terms, pilots should not notice much difference in the handling characteristics of Part 23 versus Part 25 business jets in icing conditions. Manufacturers don’t use the rule difference to achieve easier known-ice certification for Part 25 airplanes, for example.

AIN searched NTSB and other accident database records from 1990 to the present for fatal turbine airplane accidents in which icing was blamed or was a factor or possible factor. Records show three fatal accidents involving in-flight airframe icing in Part 25 jets (13 fatalities). One was a Falcon 20 and the other two Citation 560s. (One of the Citation accidents involved a Circuit City Citation at Pueblo, Colo., in February 2005, but the NTSB has not yet classified this as an icing accident; icing is suspected because it was reported by a sister airplane’s flight crew that arrived at the same time.)

Six Part 25 jets suffered ground-icing-related fatal accidents (122 fatalities), although a Citation 560 crash in Zurich, Switzerland, is questionable; NTSB records report the possibility of ground icing before takeoff but there is no conclusive report from the Swiss authorities. Total fatalities in Part 25 jet ground and in-flight icing accidents during this period were 135, which includes 27 in a Flushing, N.Y. Fokker F-28 takeoff accident and 83 in a Fokker F-100 takeoff accident in Macedonia. AIN could find no Part 23 jets that suffered icing-related fatal accidents during this period.

Turboprops didn’t do as well, killing 344 people in in-flight and takeoff icing-related accidents since 1990. Six of these accidents (32 fatalities) involved ground icing before  takeoff, and five of these occurred to Cessna 208 Caravans. Three airline turboprop accidents accounted for 119 fatalities, an ATR-72 in Roselawn, Ind.; EMB-120 in Monroe, Mich.; and Shorts 360 in Libya. Of the remainder, Cessna’s 208 had 12 in-flight icing-related fatal accidents. (One of these accidents also involved ground icing and one was not conclusive but raised the possibility of in-flight icing.) The Mitsubishi MU-2 suffered four fatal in-flight icing accidents, although a fifth accident in Pittsfield, Mass., on March 25, 2004, could have been icing-related.

Part of the reason for updating the Part 25 icing regulations is to conform to European regulations, but there does not appear to be a serious safety issue that lends urgency to the effort. Part 25 jets are not falling out of the sky encased in ice, and neither are Part 23 jets. The majority of Part 25 jet icing accidents occur during takeoff with contaminated wings, yet the proposed Part 25 regulations don’t address this area. Records show that turboprops continue to suffer the greatest number of turbine-airplane icing-related accidents, and there are many more piston-airplane icing accidents in the NTSB records than turboprops, yet there is little in the way of regulatory effort related to reducing the flight-in-known-icing hazard for non-turbine airplanes.

Which training course offers users the most information and the best value?

Two new icing-awareness training programs are available to pilots this winter, one offered by Cessna aimed at Caravan pilots and the other for all pilots by training and consulting firm Iviation of Memphis, Tenn. Both courses are offered only online so pilots can study at their own pace at home or at an FBO equipped with Internet access.

Cessna’s and Iviation’s courses have different approaches to delivering training and choosing the type of information covered. Cessna’s icing course is focused heavily on Caravan-specific knowledge, and includes many references to AFM data, while Iviation’s is more a summary of universal icing information.

NASA is offering another set of icing courses, the most recent of which is a ground-icing course released late last year. NASA’s courses, which include one on in-flight icing, are also delivered online.

The bottom line for icing training is that most pilots never get enough of it. Icing accidents kill an average of 30 people a year in the U.S. and 50 in Canada, according to the Cessna course. The majority of those accidents occur in small general aviation airplanes, not business jets, but no airplane is certified to fly in conditions outside the FAA’s Part 25, Appendix C icing envelope.

Any information that can help pilots recognize conditions outside that envelope–such as freezing rain and supercooled large droplets–and how important it is to exit those conditions immediately will help reduce the accident rate.

The benefits of icing training are quantifiable. The Mitsubishi MU-2 has suffered a relatively large number of accidents in which icing was a factor. To combat this trend, in 2003 the FAA issued an Airworthiness Directive–AD 2003-22-07–mandating that pilots obtain icing training before flying into known or forecast icing conditions. There is a recurrent training requirement, too. Since that AD became effective, there have been no ice-related MU-2 accidents, a remarkable achievement.

Cessna’s Caravan has its own icing-accident record to contend with, and from what Cessna has said about the subject, it appears likely that the FAA is planning to mandate the Cessna icing course for all Caravan pilots, possibly via an AD like the one that applies to the MU-2.

Given the high number of icing fatalities that continue to occur each year, one can’t help wondering why the FAA hasn’t made this kind of training mandatory for all IFR pilots. It seems logical that requiring a pilot to sit through one of these courses, especially the NASA in-flight icing course, instead of completing a flight review of questionable merit every two years would do more to reduce icing accidents than any other mandate the FAA could devise.

Cessna E-Learning: Caravan Cold-weather Operations

Cessna’s course is open to anyone who is interested in learning more about icing and Caravan icing safety. The Aerospace Network crew at the University of North Dakota developed the course with Cessna.

The Cessna course costs $50 ($20 for an unspecified introductory period). To sign up for the Cessna course, I had to fill out an online form at www.cessnaelearning.com. Cessna’s sign-up process lacks instant gratification, because the user has to sign up and then wait a few days for a call from a Cessna employee who will take a credit card number and issue a password to log on to Cessna E-Learning.

I signed up on a Thursday and didn’t get my password until the following Wednesday. This is too long to wait for something as simple as purchasing an online training product, and Cessna needs to simplify the process so buyers can pay and log on right away.

The Cessna icing course is delivered in five modules, each including practice quizzes and a module exam. The user has to pass each module with a score of at least 80 percent to complete the course. Fortunately, as I discovered after getting 60 percent on the first module, failing one module didn’t prevent me from continuing with subsequent modules. I had to wait at least an hour before retaking the Module 1 test; the system is designed to encourage the user to re-study the material before retaking the test.

Each module consists of a set of slides that show information about icing while a narrator summarizes the slide. The user has to click on a “next” button to move to the next slide in the series. Some slides are just a nice picture, while others are full of information. Slides with pages from the Caravan AFM or icing supplement were hard to read on my computer, but a “notes” button on the bottom of each slide allows the user to see what the narrator is supposed to say.

I use the phrase “supposed to say” because the narrator occasionally misread his script or reread a script from a previous slide. In Module 3 on Slide 19, for example, “Slide 66, Module 3, take four…” belonged on the cutting-room floor but somehow made it past the UND team’s quality-control process.

A more critical example of quality slippage was found on this Module 3 slide: the script reads (the grammar is from the script): “In any case your escape options, depends on the type of moisture, type of clouds, the severity of the icing conditions and your airplane performance.” The narrator misread that script as follows: “But in any case, it just depends on the type of moisture, type of clouds, the severity of the icing conditions, and your airplane performance, which will depend on your escape options.” This is an example of how poor script-reading can change the entire meaning of the lesson.

The Cessna/UND course makes some use of the graphics capability of modern computers. A video of stall characteristics using tufts attached to a Caravan wing is instructive, as is the discussion of coefficient of lift and how it can change with ice accumulation, along with a graph showing various lift coefficients. An animation of the lift-destroying contamination bubble moving aft on a wing was also well done.

To illustrate icing severity levels, the program shows photos of different icing accumulations. These are on the test, so pay attention. The photos showing a boot with a good buildup of ice and then a photo of the ice broken off the boot are also useful.

One big surprise in the Caravan course is that apparently Cessna still recommends that pilots wait for ice to build to one-quarter to three-quarters of an inch before cycling the boots. In Module 4, this is the advice for Caravan pilots: “The de-ice boots should generally be cycled with ice accretions from one-quarter and three-quarters of an inch of ice on the wing leading edge. Now, these are for conditions where airspeed is not a concern. The de-ice boot cycle may be delayed until three-quarters of an inch of ice is accreted on the airframe. For high rates of airspeed decay, or when airspeed approaches the minimum airspeed for icing (120 kias), the boots may be cycled with as little as one-quarter inch of ice accretion.”

FAA Icing Advice
This advice conflicts with recent FAA recommendations and NASA research, which found that there is no need to wait for ice to build to any depth before cycling de-ice boots. According to FAA Advisory Circular 23.1419-2C, which covers icing certification for Part 23 airplanes such as the Caravan, the belief that ice will freeze and form a “bridge” over the boot if boots are cycled too early, also known as “ice-bridging,” is not supported by any evidence.

“Many AFMs specify a minimum ice accumulation thickness prior to activation of the de-icer boot system,” the AC states. “This practice has been in existence due to the belief that a bridge of ice could form if the boots are operated prematurely. Flight testing and icing tunnel testing of several “modern” boot designs have not shown evidence of “ice bridging,” and no degradation in ice-shedding performance, when the boots were activated at the first sign of ice accretion. Although the ice may not shed completely with one cycle of the boots, this residual ice will be removed during subsequent boot cycles.”

An issue with ice-bridging is that no one has yet devised a method of accurately measuring the depth of ice accumulations. Presumably, this measurement is done by the notoriously unreliable eyeball method, but the Caravan training never mentions how a pilot is supposed to assess the ice depth before inflating the boots.

Each module in the Caravan course includes practice quizzes, which helped prepare me for the final module exams. The final exams consist of 10 multiple-choice questions, and they are graded instantly so that I could quickly see my score. One feature that is lacking is any feedback on which questions I got wrong, so there wasn’t any opportunity to learn from my incorrect choices.

The Cessna slide/narration delivery is OK, but the Cessna/UND team does need to fix one thing, besides the aforementioned narration mistakes, and that is the length of time that the student is forced to watch each slide.

The slides all have a time that they “play,” and once the student clicks the play button, he is forced to keep watching it for whatever length of time is assigned to the slide. Many slides are displayed seemingly interminably, when a two- or three-second glance would be plenty. These include answers to practice quiz questions and even some slides that have little to do with the course material. All that the designers need to do is make it so that when the student clicks the next button, the slide moves to the next slide without delay.

The Caravan course delivers a lot of information in the three hours that it takes to complete. Much of the information comes from the Caravan AFM and icing supplement, and the course makes good use of the Cessna material, with plenty of examples of real flights for the student to evaluate the effects of icing on Caravan performance.

One glaring absence in the Cessna course is icing-related accidents. Given the Caravan’s history of icing accidents, there is no shortage of material, and the student could learn even more by having the experts at Cessna analyze and summarize some of the type’s icing experiences. [It seems reasonable to suppose that this omission was driven by the specter of liability litigation.–Ed.]

Iviation: Aircraft Icing

David Perdue, an ATP and graduate of the U.S. Air Force Academic Instructor School who has flown corporate jets and freighters, has a great background for teaching about icing and no doubt has experienced much of what this training covers. Unfortunately, the Iviation course is somewhat generic and tedious, essentially a PowerPoint presentation narrated by Perdue. There are 71 slides in the Iviation course, and it takes about 1.5 hours to complete.

The information in the Iviation course is useful and for the most part conforms to current icing knowledge, although Perdue also teaches the discredited ice-bridging information. On Slide 62, Perdue explains that “The current rule of thumb for the use of the pneumatic boots as anti-ice equipment suggests that pilots allow one-quarter to one-half of an inch of ice to accumulate on the wing leading edge prior to activating the de-ice system.” There is no explanation for this advice or any exploration of more current NASA and FAA research.

The Iviation course mentions two accidents, the Challenger crash at Montrose, Colo., which was the result of a combination of errors including taking off with a contaminated wing; and the Southwest Airlines contaminated runway overrun at Chicago Midway, which had nothing to do with aircraft icing.

What made the Iviation course tedious is the lack of graphics. Almost every one of the 71 slides used the same background with just text to impart information. A discussion of carburetor ice, for example, could easily have included the colorful carb ice chart that shows exactly what conditions favor that type of icing.

Also lacking is any list of resources available on icing. When discussing the recent frost Safety Alert for Operators that the FAA published, why not include a link to it? There are plenty of exciting developments in the forecasting of icing conditions, yet the Iviation course doesn’t mention these or offer links to NOAA icing products that are easily available online.

Many words in the slides are misspelled. Like Cessna, Iviation’s course needs a little more work in the quality-control department. The Iviation course also has no quizzes or exams.

The Iviation course is somewhat useful and offers good advice regarding icing.
It’s not as easy to learn from as the Cessna/UND course, and it does not address any specific airplane types. But for those willing to endure a narrated text-based presentation without much in the way of interactive material or eye-pleasing graphics, there are nuggets of wisdom such as this one: “There is no such thing as an insignificant amount of ice accumulation.”

Iviation is targeting large companies for the online icing course and will negotiate pricing for multiple users. The plan is to offer bundles of courses on a variety of subjects that companies can pay to access for all their employees, according to Perdue. For more information, see www.iviation.com.

NASA: A Pilot’s Guide to In-flight Icing

The NASA in-flight icing course is the best of this bunch, and it’s free. NASA also offers a ground icing course. Both can be found at http://aircrafticing.grc.nasa.gov/courses.html.

Perhaps it’s because NASA has a bigger training-development budget and spends a lot of money on icing research, but this icing course is engaging, full of videos, animated graphics, compelling photos, accident analyses and practical exercises. Any pilot could benefit from these courses, and if the FAA makes any icing course mandatory, this is the one the agency should choose.

Examples of the NASA content include an illuminating animation of the collision- coalescence process, where smaller freezing drizzle drops join together to form more dangerous larger drops. The animation shows the drops falling then merging together, a terrific example of pictures’ ability to replace many words. The same segment includes this useful warning, which brings home the lesson and emphasizes that the collision-coalescence animation is not just a pretty picture: “Warning: If you encounter freezing drizzle, do not assume that there is a layer of warmer air above. The freezing drizzle may have formed by collision-coalescence.”

The NASA course also makes plentiful use of icing accidents to teach the importance of icing knowledge.

There are many video segments. One shows a supercooled large droplet encounter, with ice accumulating on the side window and on the propeller spinner. Another animation shows how cool air rises when blowing toward a mountain and producing rain, something that is easier to understand in an animated format than trying to study in an FAA weather book.

The NASA course also gets into a detailed discussion of weather and geography that is conducive to icing, a topic that was missing in the Cessna course and addressed to some degree in the Iviation course. Animations show cold and warm and occluded and weak cold fronts forming, again, an effective teaching method compared to lackluster FAA advisory circulars.

The most useful part of the NASA course is the practical examples, which pose challenges to the student in the form of flight-planning and in-flight exercises. These are not lightweight quiz questions but truly test the student’s knowledge while teaching new information.

In one in-flight exercise, for example, the student is flying a twin-engine boot-equipped turboprop from Denver to Grand Junction, Colo., and has entered a hold at 17,000 feet on the GJT 232 radial, awaiting approach clearance. A warm front is in the area, and there is a possibility of moderate to severe icing from the freezing level to cloud tops at 18,000 feet. A King Air 300 reported moderate to severe mixed icing on descent into Grand Junction through 15,000 feet, and the airport is reporting light winds, visibility two miles in light rain, temperature 1 degree C and ceiling 900 feet broken, 1,200 feet overcast.

At this point, most tests would simply list some multiple-choice answers and that would be that. The next step in this exercise is for the student to assess the situation, using five different cues by clicking on one image per cue. The first shows the view of the wing and the de-ice boot with ice accumulating aft of the protected area.

The next shows temperature at -5 degrees C. Airspeed has dropped 10 knots. Ice is accumulating on the unheated side window. And the last image shows ice sticking aft of the normal area on the spinner. Now the student has to assess the ice severity, the risk level and decide what to do (climb, descend, continue to hold, vector to another fix).

The final segment of this exercise asks the student to choose from various options about what to tell ATC. (The answer: “request lower, immediately, in severe icing.”) The exercise concludes when the student clicks the “transmit” button to send that message to ATC, followed by ATC’s instant response acknowledging and honoring the request.

The NASA exercises are much more engaging than the Cessna and Iviation training techniques. Clearly, the developers of the NASA course know a lot about teaching and effective transfer of knowledge. They obviously recognize that each person absorbs new information from a variety of sources. Some people learn from audio-visual content, others from reading and still others from person-to-person instruction. The NASA course makes use of all these methods, and it is thus content-rich, easy to use and a pleasurable learning experience. The NASA course is of a far higher level of quality than the other courses, and the price is right, too.

Share this...

Please Register

In order to leave comments you will now need to be a registered user. This change in policy is to protect our site from an increased number of spam comments. Additionally, in the near future you will be able to better manage your AIN subscriptions via this registration system. If you already have an account, click here to log in. Otherwise, click here to register.