Embraer 120 Horizontal Stabilizer Stall

[FlyLawyer]

A friend of mine is interviewing at Skywest in the upcoming weeks and posed the following question:

If the Aircraft accretes ice on the horizontal stabilizer to the degree the stabilizer cannot produce sufficient downforce to prevent the aircraft from pitching down violently, what is the suggested recovery technique?

Thanks for the help.

 

[checkessential]

Exacltly opposite of the wing stall recovery. EMB-120 does not have documented problem with tailplane stall. It aslo wouldn't be wise to ask the interviewer that. Is it a known question of the interview, or what? Seems a little strange to me...

 

[~~~^~~~]

Generally, just like any aircraft, you have to reduce the angle of attack on the horizontal stabilizer to re attach the airflow.

However, if asked in an interview I would mention the general aerodynamic principles, the advise I would do exactly as taught in training for the specific aircraft. A candidate is not expected to know specific airline procedures at an interview and having too strong an opinion might lead the interviewer to believe that the candidate would be resistant to learning to perform the manuever in the fashion determined best by the airline.

In order to accrete that much ice, several things have already gone wrong. First, the aircraft should be designed such that the horizontal stabilizer is less likely to stall than the wing. Second, the aircraft would have to be outside its operational envelope for flight in icing conditions. Third the crew would have to have missed a bunch of signs that ice had accumulated on the airframe and some how decided it was appropriate to remain in those conditions.

But... The NTSB has some real concerns about E120 certification in icing conditions. Here is there finding of probable cause on one loss that I have to admit could sneak up on most of us when we are stuck behind slower aircraft on approach and our attention is diverted to the approach and landing phas of flight. Bottom line, you have to be much more careful in turboprops than you do jets. The slower speeds and altitudes make icing much more of an issue.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

The Federal Aviation Adminstration's (FAA) failure to establish adequate aircraft certification standards for flight in icing conditions, the FAA's failure to ensure that at Centro Tecnico Aeroespacial/FAA-approved procedure for the accident airplane's deice system operation was implemented by U.S.-based air carriers, and the FAA's failure to require the establishment of adequate minimum airspeeds for icing conditions, which led to the loss of control when the airplane accumulated a thin, rough, accretion of ice on its lifting surfaces. Contributing to the accident were the flightcrew's decision to operate in icing conditions near the lower margin of the operating airspeed envelope (with flaps retracted) and Comair's failure to establish and adequately disseminate unambiguous minimum airspeed values for flap configurations and for flight in icing conditions. http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001208X07277&key=1

 

[embdrvr]

The problem is pilots that fly too slow in icing conditions. I know of no ice related EMB incidents or accidents where the crew was doing their job and keeping the speed up where it should have been. Whether you're flying the mighty TurboTaco or a 777 someone has to be minding the store. Sadly some of our EMB drivers had to learn that the hard way.

If you're interested in learning more use the search function on the NTSB site to look at all accidents involving the Brasilia.

 

[~~~^~~~]

The problem is pilots that fly too slow in icing conditions. I know of no ice related EMB incidents or accidents where the crew was doing their job and keeping the speed up where it should have been.

Isn't that just a little harsh? Those pilots were told by controllers to slow their approach as much as possible and evryone was focused on the slower traffic ahead. Embraer had not considered torque in their flight model for the E120 certification and when the power was applied to recover from the stall the thing pretty much snap rolled. At the time, those pilots were above VREF for the aircraft configuration. Maybe you are a whole lot better E120 driver than I was when I had 1,500 hours in the thing, but, I could see myself falling into the situation those pilots found themselves in. The difference now is that I have had the benefit of learning by their tragic loss. Since then, speed cards have been revised and now don't you guys have some sort of idiot box on the glareshield to provide additional notification of conditions / configuration?

 

[embdrvr]

Isn't that just a little harsh? Those pilots were told by controllers to slow their approach as much as possible and evryone was focused on the slower traffic ahead. Embraer had not considered torque in their flight model for the E120 certification and when the power was applied to recover from the stall the thing pretty much snap rolled. At the time, those pilots were above VREF for the aircraft configuration. Maybe you are a whole lot better E120 driver than I was when I had 1,500 hours in the thing, but, I could see myself falling into the situation those pilots found themselves in. The difference now is that I have had the benefit of learning by their tragic loss. Since then, speed cards have been revised and now don't you guys have some sort of idiot box on the glareshield to provide additional notification of conditions / configuration?

My bad!
That criticism was aimed more at guys that got slow in the climb because they were busy chatting with the FA as well as the Nassau event that had absolutely nothing to do with ATC.
I admit I forgot to consider the upset you're referring to. I get tired of ridiculous ATC requests and nowadays am more likely to respond "unable" and let them figure out how to deal with my speed. It's the old saw about "lack of plannng on your part does not constitute an emergency on my part." Part of all 121 training should be practicing to tell ATC to pound sand. I'm amazed at the number of times where I'm throwing out the anchor to keep from getting too close to heavy traffic and ATC is telling me to speed up for the guys behind me. Sorry, I'm not putting my pax thru a wake induced roll recovery demo just to compensate for poorly trained controllers.(been there done that, got the soiled underwear;-)

I'm not sure about hiring practices these days but when a friend of mine took the ATC controller hiring test he was told that the cutoff for women and minorities was something like 70% whereas he would have to score 85% to be considered. That might explain some the ineptitude we see on a daily basis. Some career fields are just not the place to allow less qualified personnel. Before anyone jumps on me for that statement let me say that I do support affirmative action. ATC simply isn't a place for it. There's plenty of good admin jobs in OKC where they can't kill me quite as easily.

 

[trip]

tail stall

tail stall with loss of pitch control

1. immediately raise flaps to previous setting.
2. full aft on controls- this will take a lot of force.

E-120/t-tail aircraft not conducive to tail stalls, more of a problem on cruciform tails. jetstreams/metro etc.

 

[embdrvr]

Re: tail stall

tail stall with loss of pitch control

1. immediately raise flaps to previous setting.
2. full aft on controls- this will take a lot of force.

E-120/t-tail aircraft not conducive to tail stalls, more of a problem on cruciform tails. jetstreams/metro etc.

To add to Trip's comments:

Buffet will be felt in control column not airframe. A lightening sensation may also be felt just prior to tail stall. SLD will give clues in terms of runback of ice into unprotected areas. You will see ice further aft on the spinner and DV windows.
Usually an altitude change of 2000-4000 feet will get you out of these conditions. No standard response such as to climb or descend. Be aware of inversions and make the decsion based on all available info at the time of encounter.
Demonstrating knowledge of tailplane stall could be a good thing in interview. Keep conversation generic, not related to specific airframe unless you have experience in it. Sporty's has copies of the NASA videos on icing for 5 bucks. Thanks Hal for making at least one thing in the catalog reasonable! I don't know anything specific about the SKy West interview process so the interview advice is generic. Knowledge of icing should be a good thing in any interview especially at an airline like Sky West which still operates a whole bunch of T-props. T-props spend a lot more time in the prime icing areas than the RJ does.

 

[FlyLawyer]

Recovery Procedure for EMB 120

Thanks for the quick response. Particular thanks to TRIP and EMBDRVR. It's been so long since I flew the ATR 42 and ATR 72 and I had forgotten the correct icing stall recovery procedure and thus didn't want to state any unsure or inaccurate info. And, as I now recall, the training aid was a video - probably the aforementioned.

As far as this being a question for Skywest, someone told my friend that it had been asked. Nonetheless, the info is valuable indeed.

Again, thanks to everyone

Irv

 

[cmrflyer]

The "nassau event" and the event were you refer to the crew chatting to the FA, are the same.

 

[ifly4food]

JUST SAY NO!

Isn't that just a little harsh? Those pilots were told by controllers to slow their approach as much as possible and evryone was focused on the slower traffic ahead. Embraer had not considered torque in their flight model for the E120 certification and when the power was applied to recover from the stall the thing pretty much snap rolled. At the time, those pilots were above VREF for the aircraft configuration. Maybe you are a whole lot better E120 driver than I was when I had 1,500 hours in the thing, but, I could see myself falling into the situation those pilots found themselves in. The difference now is that I have had the benefit of learning by their tragic loss. Since then, speed cards have been revised and now don't you guys have some sort of idiot box on the glareshield to provide additional notification of conditions / configuration?

All those pilots had to do was tell DTW approach no. They let ATC slow them to 130KT in ice accretion for crying out loud! To make matters worse, they had zero flaps selected. Yes, we can learn something here, but these pilots made several critical errors.

I applaud your 1500 hours in the EMB. In light of this you should understand it well. I have about 2000 hours in the 120 through two airlines, one of them up north. Let me leave no doubt... the E120 will carry a LOAD of ice if you fly it right. Keep the speed and power up all the way to the ground and mind the configuration.

Yes, as you're well aware, we do now have an "idiot box" [your words]. We affectionately refer to it as the "Comair Box". It emits an ear piercing wail whenever you get below 160Kt either in ice accretion or when the LE boots are on. It's disabled with flaps 15. It's very annoying, and has gotten my attention several times when that airspeed dipped.

Getting back to the tail stall, while the E120 doesn't have a record of this, it is prone to some pretty heavy tail icing. It seems to accumulate a lot more than the wings, maybe due to it's thinness. Also, since it's so high, the rampers occacionally "miss" ice on it and it's hard to check, especially at night.
One must be very careful with this airplane and be ready for anything while flying it. It's one of the last airliners that will quickly kill a complacent pilot, very unlike today's digital jets that take care of themselves.