Tailplane Stall Detection:

Tailplane stalls most often, but not always occur when flaps are being extended, or power is being added. One should also note, that if wings are picking up ice, the tail is likely to do so as well, in fact perhaps 2-3X as much as the wing… and sadly, its not visible to the pilot. In any case, if the potential exists for tail icing, one should be hand flying, rather than relying on the autopilot. Yoke forces are key.

Symptoms include

• Lightening loads.
• Difficulty trimming.
• Pilot-induced (pitch) oscillations.
• Buffets in yoke, not airframe. (The yoke pulls forward, sometimes smashing to the stop and can’t be pulled back; forces of more than 100 lbs. can occur.)
• Very sudden pitch-down, which can be unrecoverable on approach.

Do note, that stall warning systems can also end up iced over, and as such may not function.

Tailplane Stall Recovery

• If you just added flaps, and symptons of a tail stall occur, retract the flaps.
• If the yoke slams forward, it may be necessary to apply significant force to pull it back. In either case, as contrasted with a wing stall, the recovery action is the reverse, ie pull back.

In General

• pull back
• reduce power
• reduce flaps

Being tail stall recovery is the reverse of everything one is taught, its imperative to that one detects the yoke forces, rather than the airframe going mushy.

Additional Resources:

Actual Tail Stall Event
http://aircrafticing.grc.nasa.gov/courses/inflight_icing/related/3_2_3f_RI.html

Useful videos and data from Nasa
http://aircrafticing.grc.nasa.gov/resources/related.html

AC No: 23.143-1 “Ice Contaminated Tailplane Stall”

Aircraft Accidents where tail stall occurred

http://www.flightsafety.org/fsd/fsd_jun-sep97.pdf

10mar64 DC4 Slick Airways,.Boston-”Loss of balancing forces on stabalizer, due ice accretion,causing aircraft to pitch nose down too low to effect recovery…

15jan’77 Viscount,Skyline sweden,”ice on leading edge of Stabalizer causing flow seperation and Stabalizer…

06Apr58 Viscount,Capital airlines,Michigan,Undetected ice accretion on stabalizer,in conjunction with specific speed and configuration,caused loss of pitch control…

In the 70’s, service was what sold, regulated ticket prices were multifold higher than what they are today. However, the process controls and such to improve safety were still in development. Instead, the airlines relied on highly skilled people in nearly all areas of their operation. And despite that, the accident rates were much higher than today. Case in point, the crew coordination on theEastern Air Lines 401 crash. A highly experienced crew, albeit new in type, focused all their attention on a landing gear annunciator, while their plane slowly descended into a swamp.

747 Piano Bar

Today, with a high degree of automation, process controls in design, manufacturing, operations, and service insuring high reliability, the high levels of skill needed in years past, as long as nothing goes wrong, is not really needed, at least not all the time. There in lies the problem, as long as nothing goes wrong. And the problem is exacerbated, by the temptation for the airlines, the government, and the employees, to rely more and more on process, and less so on skill, in order to minimize labor costs, and thereby maximize the revenue stream.

Over the next few blog entries, I’m going to take a look at these different groups, and changes over the years which have created potentially more broken links which can lead to an accident, despite vast improvements in process control. These issues are prevalent, not only in the airline world, but also in general aviation. They are systemic problems, and sadly short of returning to the days of regulation, are unlikely to be solved. The feedback provided by the free market system, while it can work, has such huge time lags, far too many people would die, or be seriously injured, before the constraints of the free market system could kick in, if they would at all due to secondary consequences.

I often wondered why private and commercial pilots had to jump hoops in order to fly a specific aircraft with insurance whereas the CFI would only need a cursory checkout to teach in such a plane. This excludes of course multi-engine aircraft where we need 5 hours in type. I think its the judgement issue.

As a CFI, we capture a lot of experience very quickly, much faster than just earning a rating, or flying from A to B. As quoted from cut to cure, which they quoted from Training.

“Good judgment comes from experience, experience comes from bad judgment”

And what does a CFI do. We teach judgement, and skill. Skill is pretty easy, we know the PTS, we know the manuevers, we understand rudimentary educational psych, and we can tailor our teaching to the student. It is a rare student indeed that cannot be taught the skills to fly, at least to the level called out by the private pilot PTS. But judgement is the tough one.

As far as teaching judgement goes, we use textbooks, sims, and scenarios to try and demonstrate proper and improper judgement. Our students put us in situations that prior to that, we never would have experience. The net result, is we have a ton of bad experiences due to our students lack of skill, which serves to increase our own personal judgement. We also take students out into MVFR, high density altitudes, and high crosswinds routinely, in other words, we fly with them when we personally would not choose to if it were just a personal flight. Its one of the ways of teaching them judgement, but it also serves to keep our skill and build our judgement. It is however critical, that, we ourselves down grade what we know that we can safely handle, such that if the student puts us in trouble, we still have a good safety margin to recover. This is known as CFI judgement, and for some amazing fact, at that point in time, it seems to come very quickly, just like the first time you solo a student. Every mentor will tell you; “you will know when the time is right”. Every newbie CFI can’t believe it, until it happens.

I guess judgement is the same deal that surgeons have to work with. They are finally getting decent simulators, (a rad friend from many years back had to build his own, some type of funky borescope deal back in the early 80’s). And with them, they can improve skills, but sims although safer than an airplane, still don’t cut it when it comes to judgement, just as cut to cure alluded to when they compare lectures and texts with actual experience.

Sure, in a sim, I can fail a students instruments, I can throw unexpected weather their way. I can fail an engine and create a host of troubles that would be way to dangerous to do with a live aircraft. I’ve experieneced getting soaking wet with sweat in a sim. It seems realistic, but its pretty hard to preload a pilots emotional and physical status. In the sim, there are no deadlines, no passengers that have to get to a meeting, no air ambulance patient that is in trouble enroute (one of the reasons, that its common practice not to let the pilot know whats going on back there). We also can’t we emotionally burden the pilot with family, work, or personal trouble that can impair their judgement, nor can we sleep deprive them, or make them sicker than a dog after eating a proverbial pilots vending machine lunch.

In a nutshell, about the only thing long term we really can do is to have our students set absolute limits, and then let judgement build on its own with in those limits. At least during IFR flight, the FAA’s limits are pretty cut and dried. Eg at DH, its go or no go, but the bigger issue is, what is the appropriate adder to DH for a newbie. What is the limit on fuel, what are the limits on sleep, what are the limits on forecast and enroute weather. And what happens when the young pilot just looks at DH, or VFR fuel minimums, or encounters ice, or rapidly deteriorating weather. Thats where experience enters in, and from that, is where judgment is born.

Gee, I sure wish if was as easy as the graphic in my first FOI, where they had a pitcher of judgement, and all one had to do was pour it into a hole in the students head.