Jammed Elevator Event.

F

Firebird2XC

Well-Known Member
Found this rummaging around on the net. Good job to the crew.


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An American Eagle Aerospatiale ATR-72-500, registration N494AE performing flight MQ-4756 from Midland,TX to Dallas Ft. Worth,TX (USA) with 41 passengers and 4 crew, was in level flight with the autopilot engaged, when the crew noticed a pitch mistrim message, disconnected the autopilot and found both control columns restricted in their fore and aft movements with a maximum movement of about one inch foreward and one inch backward. The crew attempted the jammed elevator checklist procedure twice, but was unable to uncouple the elevators (break the link between the two control columns). After slowing to 180 KIAS the crew found better control of the elevator. When the airplane lined up for the final approach, the elevator again seemed to have jammed. The crew went around and conducted a second, shallow approach to a safe touch down. While taxiing to the gate the elevators became unjammed and the crew regained full control of the elevators.

The NTSB released their preliminary report stating, that maintenance personnel found the brackets holding the left hand elevator down limit stop had fractured and separated from the elevator, so that the down limit stop restricted the movement of the left hand elevator.

The cockpit voice and flight data recorder were secured, several damaged parts in the area of the left hand stabilizer area and the left elevator were removed for further investigation. The NTSB concluded: "The rest of the airplane was released to the operator."
 
An airplane with a control surface jamed is every bit as scary (Alaskan and Colgan come to mind) as sully and his geese.
 
Yeah that's bad bad news. Wasn't there also an ERJ out of ORD that had some pretty severe pitch problems? If you miss your morning coffee, reading that ntsb report would certainly wake you up!
 
Gotta be careful this time of year also. I see people putting their snow laden airplane in the hangar for a couple hours to warm up, then pull it right out and fly it, never thinking how when the snow melts in the hangar and pools in the crevasses of the airplane, when they take it out in 5 degree weather and take off that water is going to freeze. Ice chunks limiting control surface movement is kind of a big deal.
 
"I said to myself, God please let me land this airplane." :eek:

So what is the 160kt thing? Just hit the trim switch before you go too fast, and everything's gonna be A-Okay?
 
Eek, to both of them.

E_Dawg said:
And here it is:

http://ntsb.gov/ntsb/brief.asp?ev_id=20010105X00017&key=1
Click to expand...

You know what bothers me about this one? And perhaps I'd need a couple of you AE guys who were flying this machine before this incident to explain your craft's limitations during take-off. . .but. . .the following gets under my skin a little bit.

Following the incident, the airplane's manufacturer revealed that the horizontal stab actuator was determined to be inadequate to move the horizontal stabilizer in all flight conditions. "The incidents are most likely caused when the flight crew fails to trim the airplane after takeoff before reaching a certain airspeed where the air loads on the stabilizer may overpower the trim actuator, resulting in the horizontal stabilizer not responding to the pitch trim command from the flight crew." The manufacturer issued an alert service bulletin mandating the installation of a cockpit placard and revisions to the airplane flight manual establishing a maximum speed of 160 knots to pitch-trim after takeoff. The FAA issued an emergency AD mandating the installation of the cockpit placard and revisions to the airplane flight manual. The FAA has also tasked the manufacturer to make design changes that will enable the trim actuator to handle increased load limits. The FAA has also mandated changes that will provide improved pitch trim failure indications and ergonomic improvements of the yoke trim switches.
Click to expand...

Gee, thanks EMB. s.

At least the NTSB didn't indicate the cause was due to crew failure - but I sure do like how EMB tried to distance themselves from a faulty design.

The National Transportation Safety Board determines the probable cause(s) of this incident as follows:
The jammed horizontal stabilizer trim that occurred during the airplane's initial climb after takeoff. Factors relating to the incident were the inadequate capability of the horizontal stabilizer trim actuator to move the stabilizer during all flight phases, and the inadequate design of the system by the manufacturer.
Click to expand...
 
Not that it is really that similar but Eagle had some sort of a jammed rudder event up here in Bangor a few years back. I'll have to look for that one in the database.


....Hmmm not in the database for some reason but the crew did get one of those ALPA awards and was in the magizine.
 
E_Dawg said:
"I said to myself, God please let me land this airplane." :eek:

So what is the 160kt thing? Just hit the trim switch before you go too fast, and everything's gonna be A-Okay?
Click to expand...

Yeah if you try to muscle the thing you can bust the trim when you finally try to engage it at, oh, say 240 knots like the Beagle guy did.

Personally I have no idea HOW you could muscle an EMB-145 after takeoff. As soon as your mains are off the ground you're trimming the thing down about as fast as you can.
 
A typical ERJ takeoff has the nose trimmed up about 80% of the way. Then during rotation you really muscle the nose off pulling back about 80% to the stop. You ride the mains for a second or two as you continue pitching up to 14deg Nose up. Pretty much once you're off the ground your start trimming the nose back down.

I can't think of a time where I had to remind myself to trim prior to reaching 160kts, it would occur to any pilot normally through the control pressures.
 
Same here. The impression I got was TRIM NOW. How anyone would miss that is beyond me.
 
jtrain609 said:
Personally I have no idea HOW you could muscle an EMB-145 after takeoff. As soon as your mains are off the ground you're trimming the thing down about as fast as you can.
Click to expand...
Ditto...kind of curious what airspeed it would pitch for at 8 up if you left it alone...probably below death speed...
 
Re: E145

We had several E145 jammed stabilizer events at CHQ.

It was true that no aircraft had a 160kt limitation on it.

Most were found to occur at various airspeeds. However, Embraer's fix was first, the 160kt limitation. Second, and I don't know how well publicized this was, the trim motors were either enlarged, or had a different winding to give them more power.

One was a guy I know, and heard the story from him as well. He was giving OE out of LGA and had the stab lock up. He tried various speeds, and controlled the pitch through banking.

The scary thing is that these really seemed to start cropping up right after the Alaskan MD80 accident.
 
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