FAA Advice on Icing: Incomplete At Best
From the doesn't-everyone-know-this-#$%$ file comes this nugget this week: The FAA says icing may affect stall warning systems on older aircraft. Well, duh. Unfortunately, the reality is that everyone doesn't know this stuff, so the point is, sadly, well made and well taken. I'll get to what people don't know in a moment, but first some observations on icing accidents.
I don't think there are as many as there used to be. Back in the early to mid-1990s, we could reliably mow a lot of editorial hay out of icing accidents. A sweep of the NTSB data would reveal about 20 to 25 each year, half of which were fatal and most of which resulted from naked stupidity not necessarily related to the decision to launch into ice in the first place. Now, when sweeping accidents, a honest-to-goodness structural icing prang is harder to find. My guess is there are several reasons for this.
First, there's less flying activity and less of that flying is done in challenging winter weather. Second, there are more de-icing systems out there, especially TKS. And third, icing forecast and reporting has gotten better and although it's not as significant a direct help with ice as it is with thunderstorms, datalinked weather to the cockpit has proven a real benefit to weather awareness. So, that's my theory. I'm open to other ideas.
So, the FAA says the stall warning system might not work right, so watch it. Fine. On the other hand, if you're iced up and thinking the stall warning system has anything to do with your survival prospects, you may be too stupid to have tied your shoes on the way to the airport. Which is another way of saying there a bunch of things you need to be thinking about to survive and the stall warning is the least of them.
Now, the don't-know part. Some years ago, I was an instructor in a flying club and one of the club's pilots got into a spring icing event in upstate New York. Prudently, he diverted into the closest airport and flew an approach under high ceilings and good visibility, although with a lot of ice on the airframe. A little gentle probing revealed that he flew a normal approach, at the normal airspeed and with flaps. He was not aware that icing would alter the airfoil enough to likely raise the stall speed by some significant margin and that he should avoid use of flaps. But he learned the lesson the hard way. The airplane stalled above the runway and hit hard enough to damage gear components and bend the prop. It was an expensive repair.
I don't know why he didn't know to fly a faster approach. Or maybe he did know but in a state of mild panic, he just forgot. (He wasn't the first; the accident record reveals many examples of the same scenario.) The FAA's Special Airworthiness Information Bulletin (PDF) this week sort of addresses this.
But I'm not impressed with its advice, frankly, for a couple of reasons. One, it says that the POH should be consulted for "limitations and procedures" for flight in icing. For airplanes not approved for icing, that will be to simply say "flight in icing not approved" and if you get into it, good luck. Even the flight supplement for the TKS-equipped Cirrus SR22 doesn't go into great detail on this subject, although it does advise against the use of flaps in icing conditions, although this isn't much of a worry if the airplane is clean.
I find several things troubling about the shallowness of the FAA SAIB. It only mentions the flap issue in passing and refers to POH guidance which probably doesn't exist. Second, it completely ignores the tailplane icing and stall issue, something that has been well documented in flight tests if not in accident histories. (The flying club accident mentioned above could have been a tail stall.)
The SAIB recommends increasing airspeed by 25 percent in all phases of flight while in icing. Further, it argues treating a perceived buffet as an impending stall and immediately lowering the angle of attack. This would be precisely the wrong response to a tailplane stall. Yet the SAIB doesn't address this. It should.
Here's a far more complete and, in my opinion, well-reasoned approach to surviving with an iced up airframe. I think the best advice is to land a little faster, on the longest runway you can find and with no flaps. You will haveóor should haveódone no-flap landings in your training.
This is one place to put that training to work.