The Silliness of Icing Certification

Of all the FAA’s aircraft certification standards the one for flight into icing conditions is the most ridiculous. We pilots usually call the approval flight into known icing conditions, or FIKI, but the FAA regs don’t actually use the word “known.” As far as the rules go, icing is icing whether you knew it was there or not.

The technology to remove ice from airplanes dates back at least to the 1930s when Goodrich pioneered development of the pneumatic deice boot. Some airline airplanes in the piston era had heating systems to melt ice. Even the anti-ice fluid TKS system technology traces its roots to England in World War II. The battle against airframe ice is as old as flying in cold clouds.

But the idea of granting approval to fly into icing conditions, and to certify that the airplane’s systems can handle the ice, is relatively recent. The rules for flight into icing certification were developed for transport airplanes, those that weigh more than 12,500 pounds for takeoff, and those same rules intended for large, powerful airplanes, have been adapted, sort of, to fit piston singles and twins.

Piston airplane makers have offered ice protection systems for many decades, particularly on twins. Deice boots were glued to the leading edges, the props were protected either by a spray of alcohol or by electric heaters on the blade roots, and that was it. As the pilot of one of these airplanes you knew that the ice protection system would give you extra time to escape icing if you flew into it, but the idea that the airplane was now capable of intentionally flying into ice, and continuing in icing conditions, was absurd.

An airplane with boots was no more “approved” for flight in icing than one with weather radar was approved for flight into a thunderstorm. The radar gave the pilot a tool to avoid thunderstorms, and the boots gave the pilot a way to escape icing.

The turbine engine was probably most responsible for development of ice protection certification standards because a turbine engine just won’t continue to operate if much ice forms on its air inlet. The ice will either choke off the essential air supply or break off and damage the compressor blades of the engine, or both.

The turbine engine with its supply of very hot air that could be siphoned off from the compressor also makes it possible to provide true ice protection that other systems simply cannot. The hot air can heat the leading edges to hundreds of degrees, so hot that water is vaporized on contact so that ice can’t form, nor can the water run back and refreeze on the wing. Because it was possible to truly protect a jet from ice, the FAA wrote rules that were intended to make sure those airplanes were protected.

But it took time for the rules to catch up with the jets. The Saberliner, for example, had no ice protection for its wing leading edges. The first Learjet, the Model 23, had heated wing leading edges, but was not approved for flight in icing. And that was true of some other airplanes early in the jet age.

Because icing – like turbulence, rain, hail, or snow – is a weather phenomenon that can range from light to extreme, how do you define what icing is in order to certify an airplane to fly in it? The FAA’s own definition of severe icing for pilot reports says that severe icing is building so rapidly that normally functioning – and certified – ice protection systems can’t keep up. So in one place, the AIM, the FAA says icing that can overwhelm an airplane certified for flight into icing can exist, but then certifies the airplane for flight into icing anyway. Does that make sense?

The really difficult and expensive part of icing certification is not to demonstrate that a system prevents or removes ice, but to find icing that meets the certification standard. The rules require specific amounts of total moisture, a specific size of droplet, and – of course – specific air temperatures. All of these conditions do exist in nature, but to find all of them at once in the same parcel of air is difficult. Manufacturers spend untold hours flying to where icing is forecast and then use laser-based instruments to measure the conditions to make sure they match the FAA standards. It takes more luck than skill to find and fly into the “natural” ice the rules require, and a certification program can be held up for weeks or months looking for those conditions.

The useful ice testing is done using “ice shapes.” Sections of a wing or tail are put into an icing tunnel that can duplicate the certification standards for all conditions. The tunnel “grows” ice on the leading edge and that shape is then duplicated in some lightweight material which is then glued to the airplane wings and tail. Computer software can also predict the shape ice accretion will form and that may be acceptable. In any case, test pilots have to take off with these horrendous rough, horn-shaped globs on the leading edge and go out and see how the airplane performs, particularly near stalling speed. If the airplane handles okay with the shapes on a pilot can have confidence he can get the iced up airplane down to a runway.

But I worry that these tests that are really designed around the huge reserve of power in a jet don’t really apply to piston airplanes. I fear a FIKI approval sends the wrong message. Don’t get me wrong, I want to see ice protection on any airplane that flies IFR because at some altitude any time of the year there are clouds that can contain icing conditions. But I don’t believe that a piston airplane with icing certification is necessarily more capable than one that has ice protection that has not been certified. Maybe the FIKI airplane can handle more ice, but I do know there are conditions that it can’t handle.

Icing certification adds big bucks to the cost of an ice protection system on a GA airplane and buys the pilot little or nothing, and may even mislead him into a situation he would have avoided without the approval. I like the old system better. The ice protection is there, and it works and will handle some ice; use it to get out of icing immediately. Leave the “known” out. If you know ice is there, don’t fly into it in a piston airplane.

This entry was posted in Industry & Government, Safety, Technology. Bookmark the permalink.

14 Responses to The Silliness of Icing Certification

  1. dogbreath423@comcast.net says:

    Amen brother!

  2. jdm says:

    Oh it’s just a little ice – how bad can it be? (famous last words….)

  3. Dr. Kenneth Nolde says:

    Almost half a century ago, I can still hear my instructor giving ice advice: at 32 degrees you are vulnerable! Avoid all visible moisture! Ice forming is an invitation to land as soon as practical! Losing an aircraft to icing is like getting lost–there are resons, nut no excuses. He was a sorta weird free-spirit kinda guy and was the best instructor I ever had. Really good article, avoid icing and you do not have to test the FIKI.

  4. Michael Sheridan says:

    I wonder just how effective the “weeping wing” system is Cirrus, and how much false confidence has lead to crashes.

    • Todd Lesley says:

      I wonder just how effective the “weeping wing” system is Cirrus, and how much false confidence has lead to crashes.

      Forgive me if it’s not your intent Mr. Sheridan but your comment gives me the impression that you would hold Cirrus accountable for any icing induced crashes on TKS equipped SR-22 where the pilot placed him or herself in a bad position due to overconfidence in their ice protection system.

      If that is where you were going, I wonder if you would also hold GM accountable for any high speed crashes on air bag equipped vehicles? How about in-home blackwidow bites received by a homeowner who reached into a dark area without looking after using Ortho Home Defense? I guess feeling confident in my all weather tires makes Michelin responsible for me hydroplaning if I drive kind of fast in wet conditions?

      FYI, TKS weeping wings is an extremely effective ice protection system. However, just as Kristin points out below…….
      The most important anti-icing piece of equipment is a pilot who has studied the phenomenom of icing and the current weather and has a plan.

      Cirrus may be responsible if there is a fault with the ice protection system, but not if there is a fault with the aircraft planning, operating and decision making system we call the pilot.

      @Mr. McClellan:

      Icing certification adds big bucks to the cost of an ice protection system on a GA airplane and buys the pilot little or nothing,

      Not true. FIKI certification means that the aircraft has redundancies for critical system components. This may not be a requirement for non-FIKI aircraft. Additionally, FIKI certified aircraft have been tested for performance in icing conditions. Non-FIKI ice protection systems need only demonstrate that they do not interfere with the aircraft’s airworthiness. Many of those ice protection systems may have been tested further, if not by the manufacturer or STC holder then by the GA pilots who have owned them over the years, but it’s not a requirement.

      Those are two very important distinctions and something an aircraft owner should research when comparing ice protection systems for his/her aircraft.

      • Steve Mayer says:

        I work for a deice boot manufacturer. I’m also an instrument and commercial rated pilot both SEL and MEL. I’ve been in the aviation industry for 36 years, as a pilot, parts supplier, and parts manufacturer. Relative to your statement: “Cirrus may be responsible if there is a fault with the ice protection system, but not if there is a fault with the aircraft planning, operating and decision making system we call the pilot.” Rest assured “at fault or not” Cirrus will be sued even if the pilot is negligent to the point of failing to put fuel in the aircraft. (And so will every other manufacturer that has a part on that aircraft. Yes, even the tire manufacturer). I’ve got plenty of first hand stories to tell that will make your head spin.

        To your second point: “Not true. FIKI certification means that the aircraft has redundancies for critical system components” and: “Many of those ice protection systems may have been tested further, if not by the manufacturer or STC holder then by the GA pilots who have owned them over the years, but it’s not a requirement.” My answer: Bless your little naive heart, but sooner or later Mother Nature always wins regardless of your “test pilot” theory. There are many factors beyond the aircraft and its systems that can lead up to disaster and it always begins with the pilot. We (like Mac) do not encourage flight into known icing willingly based upon the misconception that you are protected by a deice or anti-ice system. A false sense of security is exactly that. As Mac states, icing severity is never the same even though testing has occurred. The test was good in those conditions and ONLY those conditions. Tomorrow it will be different. You have no way of knowing until you’re in it the conditions. Hope is NOT a strategy.

  5. Ron Lamb says:

    Hi, Mac. I again got two copies of your blog. I called my ISP and they advised me that based on the two different send times it is not a case of my ISP rejecting and then accepting the message. They tell me you are sending it twice. I do enjoy the blog, but getting it twice is, well, redundant.

    • Administrator4800 says:

      Left Seat tries twice to send subscribers an email. Please make sure leftseat@eaa.org is listed as a “safe sender” in your email. The reason we may be sending it twice is that your ISP is rejecting the email the first time. By the time your ISP allows it through a second email has been sent.

  6. Mark Laskow says:

    I fly my Mooney 252 a lot in the upper-teens to FL 190. At those altitudes, I can expect some ice year-round. I have a non-FIKI TKS in which I have much more confidence than the pneumatic boots on prior aircraft (C310, C340, MU-2). I think these systems have two practical benefits. First, TKS let’s me dispatch in conditions where I’m suspicious of icing, but have good alternatives if ice actually materializes. Second, when I run into unexpected ice, it buys me time to get out. In “suspicious” departure circumstances, I start the TKS during taxi to avoid any delay in employment if I need it. I also have a takeoff alternate when I leave my home base at LBE. If I encounter ice on departure, a return there is unattractive – 28 miles out to the IAF and back! That could be a long way low, slow and in ice.

  7. Kristin Winter says:

    Fortunately, the FAA hasn’t issued a Pt. 91 reg which prohibits flying in ice. The most important anti-icing piece of equipment is a pilot who has studied the phenomenom of icing and the current weather and has a plan. The next most important thing is a plane with a good rate of climb. I have had hundreds of icing encounters and have not had problems because I operated well within the capabilities of the aircraft or I did go.

    Kristin

  8. Peter STEEGER says:

    I like Marks comment because it is based on facts and experience. I look forward to more factual reporting from EAA to help us with the go/no go decision! Mac’s statements are too general.

    regards
    Peter

  9. Borneo Pilot says:

    The FAA’s own definition of severe icing for pilot reports says that severe icing is building so rapidly that normally functioning – and certified – ice protection systems can’t keep up. So in one place, the AIM, the FAA says icing that can overwhelm an airplane certified for flight into icing can exist, but then certifies the airplane for flight into icing anyway. Does that make sense?

    This makes sense to me, just like extreme turbulence may cause structural damage to the airplane. So, just as all Part 23 airplanes can handle light, moderate, and even severe turbulence (at least by the definition of it) without a problem and you could say they’re “certified” for it, we all know you can’t penetrate thunderstorms and get away with it. Same with ice: just because it’s certified for icing doesn’t mean it can handle any icing you throw at it!

  10. Simons says:

    Interesting analysis and thought about icing certification and FIKI tests. Many efforts avec been jointly done by FAA and EASA regarding FAR 25 application and definition but as it as been pointed out in this article the very origin of many misunderstandings gets us back to the basis considered for such regulation: jets. Recently the FAA has (hopefully) refused a proposal according to which “big” aircrafts (above 30 000 lbs) would not be concerned the same way than lighter ones about new FAR 25 (App O and D). This is a clue that more and more experts are now considering all airplanes and not simply “big”(commercial) ones.
    Still, even jets that are “certified” may face issues with icing, and only naïve (or not well trained) pilots would dare thinking that they are flying a safe plane… Certification process always rely on a “realistic” perimeter for all parameters, whatever the subject. So that you will always be able to meet conditions exceeding that of certification tests… and even if there are existing margins (for example stall limits for large aircraft) you can always get into trouble with unusual conditions.
    All this gets back to the real key driver: the pilot ! Recent crashes (like the A330 from Rio) have given us evidences about some lacks in pilots training program: bad reaction in bad circumstances = crash !
    Ice protection systems should always include ice detection in the loop. It is usually forgotten but it is probably more safe to follow a “detect and exit” rule (with ice protection as backup) than a “fly with protection” one… It is true in many domains: even the best protection is not 100% (in fact it may be 100%…of what you have considered or defined !). Modern trends are going more and more against since simple idea…we then pay the price.

    PS: Sorry for my english, I am a french engineer.

  11. Jay says:

    There is only one really good way to deal with ice and that is to have overwhelming power to climb out of it and to do so as soon as possible whether the aircraft is certified or not. Most large and transport category airplanes that have that kind of power also have certification for icing conditions.

    If you do choose to fly a piston powered airplane anyway, be aware that the power you need to climb out of icing conditions is not there. You are now dependent on your deice or anti-ice gear for your survival in every way until you can land, sometimes on a runway that is slick with the wind blowing the wrong direction to help you stop and the ILS aligned from the wrong way. If you have boots that worked on the ground, they might not work when you try to use them in the air and even if they do work as advertised, they must be used with the right timing and ice accumulations which many pilots die attempting to learn. Very often, boots will fail on a piston powered airplane in colder air.

    Then you have TKS systems. Let’s assume for a moment that none of the tiny holes that squirt TKS fluid out on the leading edges are blocked and that both TKS pumps are working correctly with no electrical failures. First you must turn it on and start using up your precious fluid before you get into the ice. There goes a gallon or two right there. How big is your tank and can you get more at your destination? Second, does it keep ice from forming in all the little control surface hinge points so they won’t lock up on you like a frozen treat on a stick. Is the whole airplane covered with alcohol or will there be portions that begin to whine and buzz as they change shape and size with ice development? Antenna’s, struts, gear etc… And last of all, when you get done shooting the approach down to 200 and a half or even severe clear, will you be able to see the runway through all that alcohol on the windshield?

    If the answers to these questions don’t trouble you in any way, then sooner or later you will likely have an ice encounter on a cross country flight that will be a real eye opener. And I hope you live to tell about it. From personal experience I can tell you that the most dangerous situations I have ever been in in aviation were ice related. No, your passengers won’t understand if there is no snow or ice at the airport you took off from, but you are the one with the airman certificate and you are the only one that can save the day with your knowledge and understanding.

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>