Pilot account: How I Saved A 747 From Crashing
Thread Starter
Join Date: Jan 2005
Location: USA
Posts: 43
Likes: 0
Received 0 Likes
on
0 Posts
Pilot account: How I Saved A 747 From Crashing
An old incident, but a good tale, retold:
The webpage <http://jalopnik.com/5629528/how-i-saved-a-747-from-crashing?skyline=true&s=i> recounts (via an edited 2006 court hearing transcript) a 2002 incident in which a NW 744 had a hard-over-stuck lower-rudder incident, and what the captain did to pull the rabbit out of the hat:
"Former Northwest Airlines Capt. John Hansen flew the airline's Boeing 747 route from Detroit to Toyko for years. In 2002, the plane tried to kill him and 400 passengers. This is the never-before published story of how he saved them.
"Hansen told the story in a 2006 court hearing, and the version below is his own words edited from the transcript. After taking off from Detroit in October 2002 and reaching the halfway point over the Bering Sea, Hansen and his co-pilot were retiring to the crew bunk while the other two officers took over for the remainder of the trip:
"'I was just settling down with my book and I felt the airplane do a very odd maneuver. We could feel the airplane doing something very significant and abnormal. And, after about eight or ten seconds after they recovered from it, I knew this was not right. I got up and began putting my uniform on. (First Officer) Dave (Smith) did the same thing. And just then, we got the emergency crew call from the cockpit. There's a chime that they can ring. And when the chime goes off, it means we need you right away.
"'And we heard the chime and Dave and I proceeded to the cockpit. When we got in the cockpit we saw Frank, the other captain — Capt. Gibe, fighting the controls. And he had the control wheel over about halfway, which is really odd at cruise. You never see that. And you could see his leg was straining on the rudder pedals.
"'Now one thing that's important to point out: the 747 is built with an upper rudder and a lower rudder. They're designed with two hydraulic systems powering each one. Normally, they operate together and, to an observer looking at that airplane from a distance, you couldn't tell that it's a split rudder.
"'Well, Capt. Gibe was holding full rudder pressure with his right leg; normally putting both of the rudders completely out to the right. On the lower computer screen in front of the pilots, we have a what we call a control position indicator which shows the position of all the primary controls on the airplane. The lower rudder had gone unexplainedly and quite suddenly out to the left. It was normally limited by the airplane to six degrees of rudder throw at altitude, and the rudder had gone from zero to almost eighteen degrees in less than one second. We were at approximately 35,000 feet.
"'He was explaining this while he was fighting the controls and trying to fly the airplane. And he said that with the auto pilot on, the airplane had suddenly begun an uncommanded roll to the left. And it was about almost halfway to wings vertical before he realized that the auto pilot was not going to handle this, and snapped the auto pilot off.
"'The four of us proceeded to take the cockpit operating manual, which is a red manual that we have in the cockpit designed to cover all of the emergencies that you would think that you might expect to encounter. This was not in the manual.
"'We at this point had declared an emergency and we were proceeding back to Anchorage. We had done a left turn because that was the only direction the airplane would turn. I was sitting behind Frank thinking to myself that the outcome of this is most definitely in doubt.
"'I would have given a thousand dollars for a rearview mirror. The self-diagnostics of the airplane which normally are pretty good, in this case basically told us nothing. And the control position indicator was really the only indication that we had had that the rudder was malfunctioning. The tail could be coming apart for all we knew. And if it came apart, we probably would lose the airplane...We were just going to have to figure this out.
"'I was thinking to myself, I'm the senior captain and I'm uncomfortable with the thought that when we get to Anchorage, if we're lucky enough to get to Anchorage, that it's very possible that we may have to bend this thing up, putting it back on the ground. Being the senior captain, bearing the responsibility, if anyone is going to scratch my airplane I want it to be me.
"'And I told Frank that he did a fabulous job with the initial recovery, was doing a fine job flying it, but that I was going to exercise my right to get back in the seat. Frank's reaction was, I have no problems with that.
"'Mike Fagan, the co-pilot, was handling the airplane. When I got in the (left) seat, he says, OK, are you ready? He gradually took the force off the controls as I gradually came in with the force. And I was pretty appalled at how poorly the airplane was handling. It was flying really lousy. But the point is it was flying. We didn't want to touch too many things right then because it may have been in a very delicate balance situation.
"'It took as much force as you could put into the rudder pedal to keep that upper rudder out to the right as far as it would go. And all that did was give you straight ahead. So you'd push as hard as you could with your leg, you could only do it for about ten minutes and then you'd have to switch with the co-pilot. So Mike and I took turns. We were about an hour and forty minutes west of Anchorage, about 500 miles.
"'The exchange of information among the four of us was really good. It's like the old phrase, "Love finds a way." And when you know you've got to communicate about something it's amazing how quickly those ideas flow back and forth, and I encouraged it. I said, if anyone has any ideas about anything, please speak up. It was obvious that the two things that were going to get this airplane on the ground were teamwork and good old-fashioned hand-flying, seat-of-the-pants flying.
"'Now we had some time to do some very important tasks. We had to communicate with the cabin and with the flight attendants and with the company, with air traffic control.
"'So we got the purser, which is the lead flight attendants, and the interpreter up to the cockpit and we had a meeting. And we told them exactly what the problem was, we were having trouble controlling the airplane and we were going to do our very best to get back and get it on the ground at Anchorage.
"'And we talked about how much we should tell the passengers. And we decided that this is not the time for warm, fuzzy announcements that we're going to be late in Tokyo. We decided to tell them this is exactly the problem we're having, it's a problem with the controls on the airplane, please give the flight attendants your full and undivided attention, the case being your life may depend on it. We didn't say those exact words, but we wanted them to give the flight attendants their complete attention.
"'We also had a conference call with the company and we had to do this with a primitive radio called HF, which is like you saw Clark Gable doing in the movies in the 1940s. It's a very primitive radio. But it was the only thing that would work out over the Bering Sea.
"'And our main questions were does anyone know what could be wrong with this rudder? And the second question was, we see nothing in the book about how to get this airplane back on the ground.
"'And the answers that we got back . . . no, nobody has any idea what's wrong with your rudder, sorry, and, no, there's nothing in the literature, you're basically on your own. The one suggestion that we got from the training manager was add some extra speed on final.
"'Anchorage is kind of an odd airport in that every runway has something wrong with it as far as a situation like this. It's either got a complicated approach or, like Runway 32, has a cliff at one end, so if you go too long on the landing roll, you get to the end and it's game over.
"'Runways 6, 6 Left and 6 Right, were the best ones. Six Right is the one we chose. The only disadvantage to it was if you get down close to the runway and decide it doesn't look good and you're going to go around, you're headed right at a mountain range. And it's about — only about seven or eight miles off the end of the runway.
"'So the answer to that was, do it right the first time. Don't go around.
"'The airplane is designed to cruise at 500 or 600 miles an hour; it's designed to land at about 150 or 160 mph. We didn't know what was physically wrong with the airplane. And we were afraid that once we departed this delicate balance that we were operating in that we may lose control of the airplane again.
"'So the plan was to fly past that Alaska range of mountains and then descend to 14,000 feet, which is a nice intermediate altitude. It's low enough that the air is nice and thick, and it's high enough that if you do lose control you can make one good honest attempt at recovery before the water.
"'So one other thing we talked about: The rudder on the 747-400 sends electronic signals to the nose wheel; it's designed to do that so that you can steer the airplane on the ground with the rudder pedal. So if you're taxiing and you want to take your hand off of what's called the tiller — very much like the steering wheel on your car, it's mounted over on the side wall — if you want to take your hand off the tiller and pick something up, papers or something, you can continue keeping the airplane on the taxiway with your feet through the rudder pedals.
"'However, we were afraid that those signals might be being sent to the nose wheel from a hard-over rudder, which means we might be touching down not just with a cocked rudder, but a fully cocked nose wheel, and once we lowered the nose to the runway, the airplane would head for the weeds.
"'We briefed that, and the point was well taken that the tiller mounted on the left cockpit wall, that steering wheel overrides those signals from the rudder to the nose wheel. So if I touched down on the touchdown spot and then lower the nose to the runway and the airplane tries to swerve, I was immediately going to let go of the control wheel and grab the tiller to steer the nose wheel, and Mike was going to grab the control lever.
"'I got it as stabilized as I possibly could, flew it down. We came across the fence at about 200 mph. And I put the airplane right on the touchdown spot, lowered the nose to the runway, and it tried to swerve.
"'I let go of the wheel, I said, Mike, you got it, I grabbed the tiller, and then I used reverse and braking. We had the brakes set at a very high auto-brake setting, because the airplane was still trying to swerve. The airplane was going to swerve all the way down to the point where we were slow enough where the rudder was no longer in effect.
"'We got it down to taxi speed, and you could hear all four pilots exhale at the same time.
"'The tower said that must have been quite a ride, when you get to the gate you're going to want to go back and look at that rudder.
"'As I parked the airplane, I looked down and here was Sterling Benson, the Anchorage chief pilot. He told me later that as we taxied up, it was a very impressive sight because the wheels and brakes were all cherry red they were so hot.
"'I said to Sterling, I'd like to go down and see that rudder. And he said, oh, sure, come on, I'll take you.
"'It's hard to envision how big that lower rudder really is. But when you consider that the wing span of this airplane is a couple hundred feet, you can imagine that's a huge rudder. And it was impressive.
"'It was hard over to the left thirty-one and a half degrees by the time we landed. And there was hydraulic fluid running down the bottom of the airplane and pooling on the ramp beneath it.
"'We went up in the jetway afterward, and a group of 20 passengers was getting off. This one woman saw me there with my uniform on and she said, are you the pilot who landed this plane? And I said, yes, ma'am. And she said, oh, I could just kiss you. And I said, well, you can kiss me. And she threw her arms around me and gave me a great big kiss on the cheek and thanked me.
"'As pilots, we tend to think of the responsibility as just a general thing. We know that there's passengers down there and we think, yes, we're responsible, but inside we're just thinking of flying the airplane and this is what we do. We know the responsibility is there, but it never has a personal face. But on this day, it did. And there were 400 people on that airplane that were just like her.'
"Hansen's incident led to repairs on other Boeing 747s to prevent similar incidents.
"The author of this post can be contacted at [email protected]"
=======================
A Seattle PI Nov. 8 2002 story on this incident is at <http://www.seattlepi.com/business/94360_air06.shtml>. It mentions the cause.
According to the article:
"In his report of the incident, a safety board investigator said a preliminary inspection found that the cast metal housing of the lower rudder control module was broken.
"The end portion of the control module housing that houses the yaw damper actuator had completely broken away from the main portion of the housing," the NTSB report said. Boeing said it is investigating to determine what happened and to make sure it doesn't happen again."
The webpage <http://jalopnik.com/5629528/how-i-saved-a-747-from-crashing?skyline=true&s=i> recounts (via an edited 2006 court hearing transcript) a 2002 incident in which a NW 744 had a hard-over-stuck lower-rudder incident, and what the captain did to pull the rabbit out of the hat:
"Former Northwest Airlines Capt. John Hansen flew the airline's Boeing 747 route from Detroit to Toyko for years. In 2002, the plane tried to kill him and 400 passengers. This is the never-before published story of how he saved them.
"Hansen told the story in a 2006 court hearing, and the version below is his own words edited from the transcript. After taking off from Detroit in October 2002 and reaching the halfway point over the Bering Sea, Hansen and his co-pilot were retiring to the crew bunk while the other two officers took over for the remainder of the trip:
"'I was just settling down with my book and I felt the airplane do a very odd maneuver. We could feel the airplane doing something very significant and abnormal. And, after about eight or ten seconds after they recovered from it, I knew this was not right. I got up and began putting my uniform on. (First Officer) Dave (Smith) did the same thing. And just then, we got the emergency crew call from the cockpit. There's a chime that they can ring. And when the chime goes off, it means we need you right away.
"'And we heard the chime and Dave and I proceeded to the cockpit. When we got in the cockpit we saw Frank, the other captain — Capt. Gibe, fighting the controls. And he had the control wheel over about halfway, which is really odd at cruise. You never see that. And you could see his leg was straining on the rudder pedals.
"'Now one thing that's important to point out: the 747 is built with an upper rudder and a lower rudder. They're designed with two hydraulic systems powering each one. Normally, they operate together and, to an observer looking at that airplane from a distance, you couldn't tell that it's a split rudder.
"'Well, Capt. Gibe was holding full rudder pressure with his right leg; normally putting both of the rudders completely out to the right. On the lower computer screen in front of the pilots, we have a what we call a control position indicator which shows the position of all the primary controls on the airplane. The lower rudder had gone unexplainedly and quite suddenly out to the left. It was normally limited by the airplane to six degrees of rudder throw at altitude, and the rudder had gone from zero to almost eighteen degrees in less than one second. We were at approximately 35,000 feet.
"'He was explaining this while he was fighting the controls and trying to fly the airplane. And he said that with the auto pilot on, the airplane had suddenly begun an uncommanded roll to the left. And it was about almost halfway to wings vertical before he realized that the auto pilot was not going to handle this, and snapped the auto pilot off.
"'The four of us proceeded to take the cockpit operating manual, which is a red manual that we have in the cockpit designed to cover all of the emergencies that you would think that you might expect to encounter. This was not in the manual.
"'We at this point had declared an emergency and we were proceeding back to Anchorage. We had done a left turn because that was the only direction the airplane would turn. I was sitting behind Frank thinking to myself that the outcome of this is most definitely in doubt.
"'I would have given a thousand dollars for a rearview mirror. The self-diagnostics of the airplane which normally are pretty good, in this case basically told us nothing. And the control position indicator was really the only indication that we had had that the rudder was malfunctioning. The tail could be coming apart for all we knew. And if it came apart, we probably would lose the airplane...We were just going to have to figure this out.
"'I was thinking to myself, I'm the senior captain and I'm uncomfortable with the thought that when we get to Anchorage, if we're lucky enough to get to Anchorage, that it's very possible that we may have to bend this thing up, putting it back on the ground. Being the senior captain, bearing the responsibility, if anyone is going to scratch my airplane I want it to be me.
"'And I told Frank that he did a fabulous job with the initial recovery, was doing a fine job flying it, but that I was going to exercise my right to get back in the seat. Frank's reaction was, I have no problems with that.
"'Mike Fagan, the co-pilot, was handling the airplane. When I got in the (left) seat, he says, OK, are you ready? He gradually took the force off the controls as I gradually came in with the force. And I was pretty appalled at how poorly the airplane was handling. It was flying really lousy. But the point is it was flying. We didn't want to touch too many things right then because it may have been in a very delicate balance situation.
"'It took as much force as you could put into the rudder pedal to keep that upper rudder out to the right as far as it would go. And all that did was give you straight ahead. So you'd push as hard as you could with your leg, you could only do it for about ten minutes and then you'd have to switch with the co-pilot. So Mike and I took turns. We were about an hour and forty minutes west of Anchorage, about 500 miles.
"'The exchange of information among the four of us was really good. It's like the old phrase, "Love finds a way." And when you know you've got to communicate about something it's amazing how quickly those ideas flow back and forth, and I encouraged it. I said, if anyone has any ideas about anything, please speak up. It was obvious that the two things that were going to get this airplane on the ground were teamwork and good old-fashioned hand-flying, seat-of-the-pants flying.
"'Now we had some time to do some very important tasks. We had to communicate with the cabin and with the flight attendants and with the company, with air traffic control.
"'So we got the purser, which is the lead flight attendants, and the interpreter up to the cockpit and we had a meeting. And we told them exactly what the problem was, we were having trouble controlling the airplane and we were going to do our very best to get back and get it on the ground at Anchorage.
"'And we talked about how much we should tell the passengers. And we decided that this is not the time for warm, fuzzy announcements that we're going to be late in Tokyo. We decided to tell them this is exactly the problem we're having, it's a problem with the controls on the airplane, please give the flight attendants your full and undivided attention, the case being your life may depend on it. We didn't say those exact words, but we wanted them to give the flight attendants their complete attention.
"'We also had a conference call with the company and we had to do this with a primitive radio called HF, which is like you saw Clark Gable doing in the movies in the 1940s. It's a very primitive radio. But it was the only thing that would work out over the Bering Sea.
"'And our main questions were does anyone know what could be wrong with this rudder? And the second question was, we see nothing in the book about how to get this airplane back on the ground.
"'And the answers that we got back . . . no, nobody has any idea what's wrong with your rudder, sorry, and, no, there's nothing in the literature, you're basically on your own. The one suggestion that we got from the training manager was add some extra speed on final.
"'Anchorage is kind of an odd airport in that every runway has something wrong with it as far as a situation like this. It's either got a complicated approach or, like Runway 32, has a cliff at one end, so if you go too long on the landing roll, you get to the end and it's game over.
"'Runways 6, 6 Left and 6 Right, were the best ones. Six Right is the one we chose. The only disadvantage to it was if you get down close to the runway and decide it doesn't look good and you're going to go around, you're headed right at a mountain range. And it's about — only about seven or eight miles off the end of the runway.
"'So the answer to that was, do it right the first time. Don't go around.
"'The airplane is designed to cruise at 500 or 600 miles an hour; it's designed to land at about 150 or 160 mph. We didn't know what was physically wrong with the airplane. And we were afraid that once we departed this delicate balance that we were operating in that we may lose control of the airplane again.
"'So the plan was to fly past that Alaska range of mountains and then descend to 14,000 feet, which is a nice intermediate altitude. It's low enough that the air is nice and thick, and it's high enough that if you do lose control you can make one good honest attempt at recovery before the water.
"'So one other thing we talked about: The rudder on the 747-400 sends electronic signals to the nose wheel; it's designed to do that so that you can steer the airplane on the ground with the rudder pedal. So if you're taxiing and you want to take your hand off of what's called the tiller — very much like the steering wheel on your car, it's mounted over on the side wall — if you want to take your hand off the tiller and pick something up, papers or something, you can continue keeping the airplane on the taxiway with your feet through the rudder pedals.
"'However, we were afraid that those signals might be being sent to the nose wheel from a hard-over rudder, which means we might be touching down not just with a cocked rudder, but a fully cocked nose wheel, and once we lowered the nose to the runway, the airplane would head for the weeds.
"'We briefed that, and the point was well taken that the tiller mounted on the left cockpit wall, that steering wheel overrides those signals from the rudder to the nose wheel. So if I touched down on the touchdown spot and then lower the nose to the runway and the airplane tries to swerve, I was immediately going to let go of the control wheel and grab the tiller to steer the nose wheel, and Mike was going to grab the control lever.
"'I got it as stabilized as I possibly could, flew it down. We came across the fence at about 200 mph. And I put the airplane right on the touchdown spot, lowered the nose to the runway, and it tried to swerve.
"'I let go of the wheel, I said, Mike, you got it, I grabbed the tiller, and then I used reverse and braking. We had the brakes set at a very high auto-brake setting, because the airplane was still trying to swerve. The airplane was going to swerve all the way down to the point where we were slow enough where the rudder was no longer in effect.
"'We got it down to taxi speed, and you could hear all four pilots exhale at the same time.
"'The tower said that must have been quite a ride, when you get to the gate you're going to want to go back and look at that rudder.
"'As I parked the airplane, I looked down and here was Sterling Benson, the Anchorage chief pilot. He told me later that as we taxied up, it was a very impressive sight because the wheels and brakes were all cherry red they were so hot.
"'I said to Sterling, I'd like to go down and see that rudder. And he said, oh, sure, come on, I'll take you.
"'It's hard to envision how big that lower rudder really is. But when you consider that the wing span of this airplane is a couple hundred feet, you can imagine that's a huge rudder. And it was impressive.
"'It was hard over to the left thirty-one and a half degrees by the time we landed. And there was hydraulic fluid running down the bottom of the airplane and pooling on the ramp beneath it.
"'We went up in the jetway afterward, and a group of 20 passengers was getting off. This one woman saw me there with my uniform on and she said, are you the pilot who landed this plane? And I said, yes, ma'am. And she said, oh, I could just kiss you. And I said, well, you can kiss me. And she threw her arms around me and gave me a great big kiss on the cheek and thanked me.
"'As pilots, we tend to think of the responsibility as just a general thing. We know that there's passengers down there and we think, yes, we're responsible, but inside we're just thinking of flying the airplane and this is what we do. We know the responsibility is there, but it never has a personal face. But on this day, it did. And there were 400 people on that airplane that were just like her.'
"Hansen's incident led to repairs on other Boeing 747s to prevent similar incidents.
"The author of this post can be contacted at [email protected]"
=======================
A Seattle PI Nov. 8 2002 story on this incident is at <http://www.seattlepi.com/business/94360_air06.shtml>. It mentions the cause.
According to the article:
"In his report of the incident, a safety board investigator said a preliminary inspection found that the cast metal housing of the lower rudder control module was broken.
"The end portion of the control module housing that houses the yaw damper actuator had completely broken away from the main portion of the housing," the NTSB report said. Boeing said it is investigating to determine what happened and to make sure it doesn't happen again."
Only to the extent of curing the problem. Every individual control surface on the B74 can be de-powered while retaining control to the balance of controls. Some configurations will result in an asymmetry, such as depowering either of the inboard ailerons in cruise, where the depowered aileron will float up and cause a roll that then needs to be countered. The rudder is fairly straight forward.
Still, the guys had a major stressful event and landed OK.
event report:
Event Details
Still, the guys had a major stressful event and landed OK.
event report:
Event Details
Join Date: Mar 2000
Location: Arizona USA
Posts: 8,571
Likes: 0
Received 0 Likes
on
0 Posts
Only to the extent of curing the problem.
Both the 707 and the L1011 have a rudder power switch (L1011, switchlight), once selected, all hydraulic power to the rudder is canceled.
Having had (only one time) a rudder hard over (B707) it is no pleasant experience, make no mistake.
Seems to me the crew did well....if as reported, it was factual.
Note.
Rudder pedal steering is selectable to OFF on the L1011 (some aircraft, otherwise a C/B is available to do the same action)....is the B747 not the same?
Join Date: Jan 2009
Location: alameda
Posts: 1,053
Likes: 0
Received 0 Likes
on
0 Posts
these guys have my respect
but I really have to ask, why didn't they , with the plane trying to turn left, reduce power on numbers 3 and 4?
for all pilots...think about maneuvering your plane with assymetric thrust, as if you had a hardover...we practiced that in the POS 737 with its well known rudder problem
but I really have to ask, why didn't they , with the plane trying to turn left, reduce power on numbers 3 and 4?
for all pilots...think about maneuvering your plane with assymetric thrust, as if you had a hardover...we practiced that in the POS 737 with its well known rudder problem
NWS..
B744 shows it's lineage, it's FBW,
1/8" cables to the hydraulic servo on the steering actuator... all the way back to the pedals... via pulleys, turnbuckles etc. So, if you stop the hard over of the rudder (if the pedals have followed by backdrive... not always the case) then the NWS is not going to be affected.
B744 shows it's lineage, it's FBW,
1/8" cables to the hydraulic servo on the steering actuator... all the way back to the pedals... via pulleys, turnbuckles etc. So, if you stop the hard over of the rudder (if the pedals have followed by backdrive... not always the case) then the NWS is not going to be affected.
Join Date: Oct 1999
Location: LHR
Posts: 556
Likes: 0
Received 0 Likes
on
0 Posts
There are dozens of airline managers out there right now putting together a case for their regulatory authorities to justify removing heavy crews from as many longhaul flights as they can. Accountants don't make good pilots!
As for Mr O'Dreary's idea about 1 pilot and a stewardess.... The man is an arrogant moron.
As for Mr O'Dreary's idea about 1 pilot and a stewardess.... The man is an arrogant moron.
stick to your QRH
I guess this event would call for the unannunciated QRH procedure Jammed Or Restricted Flight Controls
Which is pretty much what the crew did, according to the story. And it worked - good show guys.
That procedure does not call for depressurizing hydraulic systems 2 & 4, which would have depowered the lower rudder. Which would have also affected all the other flight controls, i.e.; now you're left with only 2 out of 4 hydraulic systems.
Out of the frying pan and into the fire...
Bottom line; as long as a QRH procedure works, stay away from playing test pilot.
Which is pretty much what the crew did, according to the story. And it worked - good show guys.
That procedure does not call for depressurizing hydraulic systems 2 & 4, which would have depowered the lower rudder. Which would have also affected all the other flight controls, i.e.; now you're left with only 2 out of 4 hydraulic systems.
Out of the frying pan and into the fire...
Bottom line; as long as a QRH procedure works, stay away from playing test pilot.
Bottom line; as long as a QRH procedure works, stay away from playing test pilot.
Checkboard, I agree with you that you should know your airplane.
But:
The last part of the Jammed Or Restricted Flight Controls QRH procedure is:
- 4 Choose one:
Faulty system can not be overpowered:
Use operative flight controls, trim
(including alternate trim), and thrust as
needed for airplane control.
END
- Faulty system can be overpowered:
END
They used the first option; operative flight controls and asymmetric thrust, to keep the airplane controllable. Which did work. Completing the QRH procedure.
Now when the airplane would not have remained controllable, 'extracurricular' actions could be considered, for which thorough systems knowledge would certainly be required.
You cannot always restore a broken system in flight, sometimes you leave it as is, as long as you can get the airplane on the ground safely.
Boeing's disclaimer: "The flight crew must be aware that checklists cannot be created for all conceivable situations and are not intended to replace good judgment. In some situations, at the captain’s discretion, deviation from a checklist may be needed".
But I wouldn't do any deviating as long as the QRH appeared to work.
But:
The last part of the Jammed Or Restricted Flight Controls QRH procedure is:
- 4 Choose one:
Faulty system can not be overpowered:
Use operative flight controls, trim
(including alternate trim), and thrust as
needed for airplane control.
END
- Faulty system can be overpowered:
END
They used the first option; operative flight controls and asymmetric thrust, to keep the airplane controllable. Which did work. Completing the QRH procedure.
Now when the airplane would not have remained controllable, 'extracurricular' actions could be considered, for which thorough systems knowledge would certainly be required.
You cannot always restore a broken system in flight, sometimes you leave it as is, as long as you can get the airplane on the ground safely.
Boeing's disclaimer: "The flight crew must be aware that checklists cannot be created for all conceivable situations and are not intended to replace good judgment. In some situations, at the captain’s discretion, deviation from a checklist may be needed".
But I wouldn't do any deviating as long as the QRH appeared to work.
Last edited by Mariner; 9th Sep 2010 at 10:05.
Join Date: Dec 2001
Location: London
Posts: 186
Likes: 0
Received 0 Likes
on
0 Posts
Is this the same PCU implicated in the catastrophic 737 hardovers (Pittsburgh and Colorado Springs, others too, arguably)?
Can engineers say whether the failure mode could be devised to be less risky? The NTSB response (from the link above) to the incident seems uncharacteristically relaxed.
Can engineers say whether the failure mode could be devised to be less risky? The NTSB response (from the link above) to the incident seems uncharacteristically relaxed.
Tankengine,
That was my first thought on reading of the situation. Would that have worked? No idea!
The aircraft was controllable (just) so there was time to look at what would be lost.
(Now, without going up to the attic and getting out a 744 Tech Manual) HOWEVER, if the lower rudder had stayed over, you'd have lost some aileron authority and, if control was lost, you'd need to get those systems pressurised again pronto.
Anyway, well done the lads - tea and medals in the boss's office.
Would de-pressurizing the Hydraulic System for the lower rudder have helped?
The aircraft was controllable (just) so there was time to look at what would be lost.
(Now, without going up to the attic and getting out a 744 Tech Manual) HOWEVER, if the lower rudder had stayed over, you'd have lost some aileron authority and, if control was lost, you'd need to get those systems pressurised again pronto.
Anyway, well done the lads - tea and medals in the boss's office.
Not from the Flight Deck Dani.
There are 8 Flight Control Shutoff Switches on the Overhead Maintenance Panel, but they are for maintenance use only, on the ground. They can shut off each hydraulic system for the entire tail or wing. So if you would close the one for the tail you would also lose that hydraulic system for the elevator in addition to the rudder. Not a great idea.
Boeing would have put it in their QRH if it were that easy
If you have a split rudder hard over, you could reduce power on the opposite outboard engine. And stand on that remaining rudder, of course. Just like the NWA crew did.
There are 8 Flight Control Shutoff Switches on the Overhead Maintenance Panel, but they are for maintenance use only, on the ground. They can shut off each hydraulic system for the entire tail or wing. So if you would close the one for the tail you would also lose that hydraulic system for the elevator in addition to the rudder. Not a great idea.
Boeing would have put it in their QRH if it were that easy
If you have a split rudder hard over, you could reduce power on the opposite outboard engine. And stand on that remaining rudder, of course. Just like the NWA crew did.
