Md-11 Lsas
03-26-2009, 12:27 PM
#11
On Reserve
Joined APC: Dec 2007
Posts: 19
I'm just speculating here, but what are the chances of the FAA finally making us split our fleet? MD-10s and MD-11s (two different bid packs).
03-26-2009, 01:28 PM
#12
Gets Weekends Off
Joined APC: Oct 2008
Position: Heavily Involved
Posts: 473
Yeah but.........
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.
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.
Think about Dale Earnhardt at Daytona. It took very little G-loads but delivered in the right fashion to kill one of the greatest Nascar drivers ever. The initial nose-gear touchdown was nothing short of violent. I think my bud may have a point, and if the FDR shows no pilot input after they became airborne again, I'll be he's right.
03-26-2009, 01:35 PM
#13
Gets Weekends Off
Joined APC: Jan 2006
Position: ANC-Based MD-11 FO
Posts: 328
Reference item 6 on that long list: PAP engages only if the spoilers are deployed. I don't see spoilers deployed in the video. That means the throttles were above the threshold for auto spoiler deployment (60% I think?). Maybe they were attempting a go-around...?
03-26-2009, 02:19 PM
#14
Gets Weekends Off
Joined APC: Sep 2006
Position: B-777 Captain
Posts: 943
Talked to a bud last night and he has an interesting twist on this. If you watch the video on the "initial" nose-gear touchdown, take notice how utterly violent that nose touches down. In fact, in reports from witnesses at the airport it blew "both" nose gear tires from the aircraft. By bud surmises this violent touchdown may have knocked both pilots unconscious, therefore you see the jet recoil back into the air, most likely due to the recoiling of the nose-gear strut on what was most likely a very lightly loaded MD-11 in a very strong headwind. With no conscious pilots to add power and administer a go-around, the jet continued a mini-phugoid and simply pitched back over to 4-6 degrees, impacting the runway again in tragic form.
Think about Dale Earnhardt at Daytona. It took very little G-loads but delivered in the right fashion to kill one of the greatest Nascar drivers ever. The initial nose-gear touchdown was nothing short of violent. I think my bud may have a point, and if the FDR shows no pilot input after they became airborne again, I'll be he's right.
Think about Dale Earnhardt at Daytona. It took very little G-loads but delivered in the right fashion to kill one of the greatest Nascar drivers ever. The initial nose-gear touchdown was nothing short of violent. I think my bud may have a point, and if the FDR shows no pilot input after they became airborne again, I'll be he's right.
03-26-2009, 02:31 PM
#15
Gets Weekends Off
Joined APC: Feb 2006
Position: Mayor of Awesometown
Posts: 137
Talked to a bud last night and he has an interesting twist on this. If you watch the video on the "initial" nose-gear touchdown, take notice how utterly violent that nose touches down. In fact, in reports from witnesses at the airport it blew "both" nose gear tires from the aircraft. By bud surmises this violent touchdown may have knocked both pilots unconscious, therefore you see the jet recoil back into the air, most likely due to the recoiling of the nose-gear strut on what was most likely a very lightly loaded MD-11 in a very strong headwind. With no conscious pilots to add power and administer a go-around, the jet continued a mini-phugoid and simply pitched back over to 4-6 degrees, impacting the runway again in tragic form.
Think about Dale Earnhardt at Daytona. It took very little G-loads but delivered in the right fashion to kill one of the greatest Nascar drivers ever. The initial nose-gear touchdown was nothing short of violent. I think my bud may have a point, and if the FDR shows no pilot input after they became airborne again, I'll be he's right.
Think about Dale Earnhardt at Daytona. It took very little G-loads but delivered in the right fashion to kill one of the greatest Nascar drivers ever. The initial nose-gear touchdown was nothing short of violent. I think my bud may have a point, and if the FDR shows no pilot input after they became airborne again, I'll be he's right.
03-26-2009, 03:11 PM
#16
Line Holder
Joined APC: Nov 2005
Posts: 62
The PNL function of the LSAS applies 3 degrees of nose down elevator upon initial spoiler deployment (to assist in the nose-lowering task), increasing to 4 degrees once spoilers have deployed beyond 10 degrees.
03-26-2009, 03:58 PM
#17
Gets Weekends Off
Joined APC: Feb 2007
Posts: 397
J
"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."
"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."
03-27-2009, 04:45 AM
#18
On Reserve
Joined APC: Apr 2008
Posts: 24
Take a look at this link. Its another FX MD11 landing in NRT in what appears to be similar wind conditions (nice job btw). Look at the touchdown. Its a nose high attitude but as the nose is being lowered the mains are not yet firmly on the ground. It appears that its almost at a 3 (4 point?) point attitude when the mains are finally firmly on the ground and then it almost looks like a bit of porpoising after that.
YouTube - Crosswind Landing - by FedEx Express McDonnell Douglas MD-11(F) ?N587FE?
YouTube - Crosswind Landing - by FedEx Express McDonnell Douglas MD-11(F) ?N587FE?
03-27-2009, 05:31 AM
#19
Gets Weekends Off
Joined APC: Dec 2007
Posts: 112
Yes, it's true that he while he never flew the airplane, is there anything in Monte's statement that is untrue or inaccurate? In fact, no. It's an accurate observation from someone who has been around Fedex, and, I believe, the training department, for a long time.
03-27-2009, 05:45 AM
#20
Line Holder
Joined APC: Jan 2007
Position: MD11 CA
Posts: 31
Just a little info about LSAS and WAGS. They are two separate animals.
LSAS works when the autopilot is off and you have less than 2 pounds of pressure on the yoke. It uses 5 degrees of elevator authority to command or hold pitch changes when there is no input from the pilot.
You do get positive nose lowering when the spoilers deploy on landing. That assumes that you are not holding the nose off the ground with positive back pressure during actual touchdown. That's why when we land you are suppose to release back pressure at 10 ft. to essentially a neutral stick. You can always override LSAS.
With regards to stall protection it will use it's 5 degrees of elevator authority to lower the nose to get away from the Pitch Limit Indicator (indicator of Vss/Vso). It will not, however, dump the nose to do this. Demos I've done in the sim show this to be a very slow process. I do not believe the nose down pitch you see on the video was caused by LSAS.
WAGS tells you when you are in windshear and provides you guidance on how to get out of it. If the autopilot is on (LSAS not working) it will follow the guidance, if the autopilot is off you have to follow the guidance, ie follow the Flight Director (again more than 2lbs of pressure on the yoke, LSAS not working). That simple.
Hope this helps.
Disco
LSAS works when the autopilot is off and you have less than 2 pounds of pressure on the yoke. It uses 5 degrees of elevator authority to command or hold pitch changes when there is no input from the pilot.
You do get positive nose lowering when the spoilers deploy on landing. That assumes that you are not holding the nose off the ground with positive back pressure during actual touchdown. That's why when we land you are suppose to release back pressure at 10 ft. to essentially a neutral stick. You can always override LSAS.
With regards to stall protection it will use it's 5 degrees of elevator authority to lower the nose to get away from the Pitch Limit Indicator (indicator of Vss/Vso). It will not, however, dump the nose to do this. Demos I've done in the sim show this to be a very slow process. I do not believe the nose down pitch you see on the video was caused by LSAS.
WAGS tells you when you are in windshear and provides you guidance on how to get out of it. If the autopilot is on (LSAS not working) it will follow the guidance, if the autopilot is off you have to follow the guidance, ie follow the Flight Director (again more than 2lbs of pressure on the yoke, LSAS not working). That simple.
Hope this helps.
Disco
