MD10PLT

I've been reading a little about this system and the manuals aren't real clear. I know the system will cause a nose down command if you are in a stall, but will it do it if you are in windshear.

FR8Hauler

I was thinking the same thing...

jonnyjetprop

The answer is yes and no. "LSAS stall protection engages if windshear command guidance is on. If
windshear command guidance is off, LSAS stall protection should have
engaged earlier (amber PLI)" There would still have to be stick shaker first. If your looking at possible factors, I'd look at PNL. Keep in mind, you're only looking at 10-15 lbs. of force.

Shaggy1970

LSAS Does many things for the MD! I will break out the manual and spell them out once I have free minute.

brownwhalerider

LSAS does command a lower pitch on landing, ie lowers the nose, when the aircraft is on the ground and the spoilers are deployed. It is to help prevent tail strikes. It is also off when airborne less than 100 ft AGL. So you could have a scenario with a bounce where it could get interesting.

FR8Hauler

Not so sure about that. A lot of inputs going into that system in this situation. I am not saying it was the cause but I think it could have been a factor in prohibiting a recovery.

Shaggy1970

Here you go! Number six is what people are concerned with!

Longitudinal Stability Augmentation System (LSAS)
LSAS provides:
1) Pitch Attitude Hold and Automatic Pitch Trim – With no force
on the control column, and bank angle less than 30 degrees,
LSAS holds the current pitch attitude. LSAS holds this attitude
by deflecting the elevators as much as 5 degrees. The
horizontal stabilizer is automatically adjusted to relieve the
sustained elevator deflection and maintain a full 5 degree
elevator authority.
2) Pitch Attitude Limiting – LSAS maintains pitch attitude to less
than 10 degrees of dive, or less than 30 degrees of climb.
3) Pitch Rate Damping – Increases the apparent static stability to
reduce the chance of over-control in pitch. It is active
throughout the flight envelope. 100% of max damping is
available above 20,000ft, decreasing linearly to 30% below
16,500 ft.
4) Speed Protection – If the autopilot is not engaged and the
autothrottle is not available (or able to maintain a safe speed),
LSAS Speed Limiting will engage to provide overspeed or
stall protection. LSAS overspeed protection is accomplished
by changing pitch. LSAS does not provide flap, slat or gear
overspeed protection.
5) Stall Protection – At 75-85 pct of the angle of attack required
to activate the stick shaker, the LSAS stall protection engages.
LSAS reduces pitch until the AOA is sufficiently reduced.
6) Pitch Attitude Protection and Positive Nose Lowering - During
takeoff rotation, LSAS provides Pitch Attitude Protection
(PAP) to reduce the possibility of a tail strike. During landing,
after spoiler deployment is commanded, LSAS initiates
Positive Nose Lowering (PNL) to assist in transitioning the
nose wheel to the runway after main gear touchdown.
LSAS is off when:
1) The autopilot is engaged
2) Below 100 ft RA, except active for pitch attitude protection
during takeoff and positive nose lowering during landing.
3) Bank angle exceeds 30 degrees
4) During manual trim operation
5) Pilot can override LSAS if, when below 1500 ft., more than
appx 2 lbs. of pressure is applied to the control column; or,
when 10-15 lbs of force is applied while PAP or PNL is active.
The pilot may counteract the LSAS overspeed or stall protection
by using enough manual force on the control column (appx 50
lbs) to defeat the LSAS inputs.
LSAS Switches
FAIL (illuminated)
-Control channel has failed, and has shut off
OFF (illuminated)
-Respective LSAS switch has been pressed, and the
corresponding control channel has been turned off.

Sleepyflyer

Fedex MD11 software program load will be different than say UPS MD11, because of the adjustment to make it fly somewhat like the MD10. (Not!!!)

LivingInMEM

Just a couple of signs that others are thinking along these lines:

FedEx Jet Has Control Issues - WSJ.com

"U.S. and most foreign carriers phased out MD-11s from passenger operations partly because of their high fuel consumption and relatively short range. But some carriers, including Delta Air Lines Inc., became disenchanted with the plane's often touchy handling.

At one point, Delta's management took the unusual precaution of instructing all MD-11 pilots to manually fly the planes up to cruise altitude -- in order to better understand their handling characteristics. But with some software and other modifications, FedEx and other cargo carriers have come to depend heavily on MD-11 aircraft."

-and-

"Monte Thames, a retired FedEx pilot, said MD-11s were so notoriously "squirrely" to land that pilots routinely spent extra time in flight simulators practicing how to control the plane. "The MD-11 is one of those planes that can bite you real quick," said Mr. Thames, 62, of Germantown, Tenn."

then:

That Tragic MD-11 Safety Record

AN excerpt from a 2000 WSJ article (partially posted at above site)

"Yet sometimes, at low altitude, the opposite occurs: Pilots tell of pulling with all their might and finding the plane hardly responded. That can be a problem during landing. In several instances where pilots brought down their MD-11s too rapidly and tried to compensate at the last minute, they smacked the aircraft's tail on the runway or caused other damage.

That's what NTSB investigators reckoned took place in 1997 when FedEx pilots tried to land an MD-11 at Newark. The plane touched down too hard, bounced, rolled right, broke its right wing, flipped over and was destroyed by fire. The two pilots, who escaped, took most of the blame. But the safety board also raised questions about the plane's "stability and control characteristics," the design of its landing gear and why its wing broke off, a rare occurrence in similar hard-landing accidents."

Unofficial they all are, but I have been able to find numerous sources dating to before 2000 that were questioning of the MD-11 flight control system.

What's the saying - When there is smoke, there is usually fire.

jonnyjetprop

I was editing my post as you posted this. Windshear+stick shaker would give a pitch down, but not windshear alone. At least this is listed in load 908.