Black box data is the ne plus ultra of aircraft accident investigation. But it is not the only kind of physical evidence. Pieces of debris—in particular, their dents and fractures — can tell a vivid story by themselves.
There are five basic ways that an object can break. The two most important for our present discussion are tension and compression. A tension failure occurs when something is pulled apart—think of pulling the ends of a piece of string until it snaps. Compression is the opposite; it’s what happens when something is crushed by a weight or smashed in an impact.
When a plane crashes, it’s common for all different parts to exhibit different kinds of failure. Imagine a plane whose wingtip hits a tree. The impact would crush the leading edge of the wingtip—compression failure—and then wrench the wing backwards from the body of the plane, causing a tension failure at the forward wing root and compression failure at the aft end.
By collecting many pieces of debris after a crash, investigators can place the mechanical failures in a chronological order to tell a story that makes sense, much as you might arrange magnetic words on a refrigerator. This is how the mystery of TWA 800 was solved. When the fuel tank exploded, the pressure pushed the fuselage skin outward so that it came apart like a balloon popping. The plane broke into two major parts that smashed apart when they hit the ocean. Thus tension failures predominated in the first phase of the catastrophe and compression failures predominated later.
So now let’s turn to the issue at hand. What story do the pieces of MH370 debris tell?
In April of this year the Malaysian government published a “Debris Examination Report” describing the 20 pieces of debris that were deemed either confirmed, highly likely or likely to have come from the plane. For 12 of them, investigators were able to discern the nature of the mechanical failure. Some key excerpts:
Item 6 (right engine fan cowl): “The fracture on the laminate appears to be more likely a tension failure. The honeycomb core was intact and there was no significant crush on the honeycomb core.”
Item 7 (wing-to-body fairing): “The fibres appeared to have been pulled away and there were no visible kink on the fibres. The core was not crushed; it had fractured along the skin fracture line.”
Item 8 (flap support fairing tail cone): “The fracture line on the part showed the fibers to be ‘pulled out’ showing tension failure. Most of the core was intact and there was no sign of excessive crush.”
Item 9 (Upper Fixed Panel forward of the flaperon, left side): “The fracture lines showed that the fibres were pulled but there were no signs they were kinked. The core was intact and had not crushed”
Item 12 (poss. wing or horizontal stabilizer panel): “The carbon fibre laminate had fractured and appeared to have pulled out but there was no crush on the core.”
Item 15 (Upper Fixed Panel forward of the flaperon, right side): “The outboard section had the fasteners torn out with some of the fastener holes still recognizable. The inboard section was observed to have signs of ‘net tension’ failure as it had fractured along the fastener holes.
Item 18 (Right Hand Nose Gear Forward Door): “Close visual examination of the fracture lines showed the fibers were pulled and there was no sign of kink.”
Item 20 (right aft wing to body fairing): “This part was fractured on all sides. Visual examination of the fracture lines indicated that the fibers appeared to have pulled away with no sign of kink on the fibers.”
Item 22 (right vertical stabilizer panel): “The outer skin had slightly buckled and dented but the inner skin was fractured in several places…. The internal laminate seems to be squashed.”
Item 23 (aircraft interior): “The fractured fibres on the item indicated the fibres were pulled out which could indicate tension failure on its structure.”
Item 26 (right aileron): “The fitting on the debris appeared to have suffered a tension overload fracture.”
Item 27 (fixed, forward No. 7 flap support fairing): “One of the frames was completely detached from the skin. It may be due to fasteners pull through as the fasteners’ holes appeared to be torn off with diameters larger than the fasteners.”
Note that all of these but one failed under tension. The exception is item 22, which came from the tail—specifically, from near the leading edge of the vertical stabilizer.
It’s particularly remarkable that Item 18, the nose gear door, failed under tension. (Image at top) If, as the Australian authorities believe, the plane hit the sea surface after a high-speed descent, this part of the plane would have felt the full brunt of impact.
Bill Waldock, a professor at Embry Riddle University who teaches accident-scene investigation, says that if MH370 hit the water in a high-speed dive, you would expect to see a lot of compression, “particularly up toward the front part. The frontal areas on the airplane, like the nose, front fuselage, leading edge of the wings, that’s where you’d find it most.”
I spoke to a person who is involved in the MH370 investigation, and was told that officials believe that that observed patterns of debris damage “don’t tell a story… we don’t have any information that suggests how the airplane may have impacted the water.” Asked what kind of impact scenario might cause the nose-gear door to fail under tension, it was suggested that if the gear was deployed at high speed, this could cause the door to be ripped off.
This explanation is problematic, however. According to 777 documentation, the landing gear doors are designed to open safely at speeds as high at Mach 0.82 — a normal cruise speed. The plane would have to have been traveling very fast for the door to have been ripped off. And to be deployed at the end of the flight would require a deliberate act in the cockpit shortly before (or during) the terminal plunge.
The experts I’ve talked to are puzzled by the debris damage and unable to articulate a scenario that explains it. “The evidence is ambiguous,” Waldock says.
In a blog post earlier this month, Ben Sandilands wrote, “Don Thompson, who has taken part in various Independent Group studies of the mystery of the loss of the Malaysia Airlines in 2014, says some of these findings support a mid-air failure of parts of the jet rather than an impact with the surface of the south Indian Ocean.”
A mid-air failure, of course, is inconsistent with the analysis of the Inmarsat data carried out by Australian investigators. So once again, new evidence creates more questions than answers.
UPDATE 5/24/17: Via @ALSM, here’s a diagram of the front landing gear and doors:
UPDATE 5/25/17: In the comments, we discussed the possibility that the front gear door could have come off in the process of a high-speed dive. @ALSM speculated that the loss of engine power upon fuel exhaustion could have led to loss of hydraulic pressure, which could have allowed the gear doors to open spontaneously, and then be ripped off in the high-speed airstream. But he reported that Don Thompson had dug into the documentation and confirmed that following a loss of hydraulic power the gear would remain stowed and locked. Thus it seems unlikely that the gear door could have spontaneously detached in flight, even during a high-speed descent.
UPDATE 5/25/17: There’s been some discussion in the comments about flutter as a potential cause of inflight breakup, so I thought it would be apropos to add a bit more of my conversation with the accident investigator involved in the MH370 inquiry.
Q: Does the MH370 flaperon look like flutter to you?
A: In a classic sense, no, but where you would be looking for flutter would be on the stops, on the mechanical stops that are up on the wing, so the part of that piece that came out. And in looking at that piece, you’ve got different types of failures of the composite skin that don’t appear to be flutter.
Q: What does it look like?
It just looks like kind of an impact-type separation. So it looks like you’ve drug that thing either in the water or on the ground or something. But it’s a little hard with that one because you don’t have any other wreckage, so, one of the keys — you don’t base anything on one small piece, you’re trying to look at kind of the macroscopic view of all the wreckage to make sure that, “Oh, if I think this is flutter do I see the signatures elsewhere on the airplane?” Typically we won’t base it on one piece like the flaperon.
To provide some context, we had earlier talked about the phenomenon of flutter in general:
Q: I can think of a couple of cases where there was flutter, where the plane got into a high speed descent and stuff got ripped off.
A: Yup.
Q: Where would that fall in the bestiary of failures that we talked about earlier?
A: So flutter’s kind of a unique thing, and it’s based on aircraft speed and structural stiffness. So, you know, when those two things meet you get this excitation, an aerodynamic excitation of a control surface which will become dynamically unstable and start going full deflection. So for a flutter case you generally look at the control stops—so there’s mechanical stops on all the flight controls—and you look for a hammering effect on the stops. So repeated impacts on the stop will tell you that, hey, maybe you’ve got a flutter event.
Q: But if you see the piece—there was a China Airlines incident, the elevator was shredded, or part of it was ripped off. What would that look like?
A: Mm-hmm. You know, it’s going to be different for every single case. Sometimes that flutter will generate the load in the attachment points, break the attachment points, and other times it will tear the skin of the control surface, and so you’ll see this tearing of the skin and the separation of rivet lines, and everything. I’ve seen both. I’ve seen a control surface that comes apart at the rivets, and flutters that way, and I’ve seen them where it generates loads to break the attachment points. It depends on the loads that are created and how they’re distributed throughout the structure.
For his part, Bill Waldock told me that the tensional failure of the collected debris implies a shallow-angle impact. Both experts, in other words, believe the debris is most consistent with a more or less horizontal (rather than high-speed vertical) entry into the water.
This is not consistent with the ATSB’s interpretation of the BFO data unless we posit some kind of end-of-flight struggle, à la Egyptair 990, or last-minute change-of-heart by a suicidal pilot. Either seems like a stretch to me.
As a side note, with respect to the ATSB.
Some of you may be aware of the Norfolk Island ditching of a PelAir Westwind during an air ambuance mission.
The initial ATSB investigation was roundly castigated by all, including the Austalian Senate. As a result, the case was “re-opened”.
The new report “Mk-2”, is due soon.
In the video linked below, a “new” Commisioner Chris Manning (NOT the Chief Commisioner – that is Greg Hood (ex RAAF and ex CASA) – ex Chief Pilot of Qantas, was called before the Senate to advise on the current status of the “Mk-2” report. It is very “illuminating”.
https://www.youtube.com/watch?v=I0_qAUNo2pA
Re the “LIDO SLIDE”, did anyone ever digitise the positions of all of the little yellow radar points with their times and publish them ?
@Jeff
Back on track. Excellent article about a crucial piece and the overall damage that is mentioned.
I mentioned it early on (about the nose gear door). This just could not have been a high speed nose dive impact any way.
I’ll copy your topic to Victor’s site. It’s essential we all share information imo.
Reading all high speed and flutter arguments again (@ASLM) on the general debris and the nose gear door too it makes me wonder about denying the much more obvious.
Why? Hang on to your believes?
No way all those trailing edge wing/control surface/engine related pieces and this nose gear door seperated that way.
It’s obvious as can be. No other high speed dive crash compares to this. No SilkAir or ChinaAir or any other Air.
Those pieces seperated during a ditch-like event under relatively low speed and low AoA.
The nose gear door imo most probably even got seperated while the nose (landing) gear was down on impact.
I see no other way in which the inside edge of the piece could have stayed so clean and the whole piece without compression damage.
Just impossible in any other way imo.
Briefly, another interesting bit of news (or not…)
SOS mystery in remote Western Australia stumps police
An SOS signal made of rocks in a remote part of Western Australia has prompted fears that someone, or more than one person, could be missing.
The distress signal was spotted by a helicopter pilot. It led to a ground search by police who had to reach the area by air because of tough terrain.
Authorities have now appealed for public help after failing to find “any indication of recent human activity.”
Senior Sgt Peter Reeves told the Australian Broadcasting Corp that the message may have been there for years.
Hmmmm….
http://www.bbc.co.uk/news/world-australia-40024824
http://www.smh.com.au/national/mystery-sos-sign-found-in-a-remote-part-of-western-australias-kimberley-20170526-gwebne.html
@Ge Rijn
RE:”Those pieces seperated during a ditch-like event under relatively low speed and low AoA.
The nose gear door imo most probably even got seperated while the nose (landing) gear was down on impact.”
completely in agreement. the debris found so far has alway made me wonder if it crashed according the official story.
@Ge Rijn
Ditching can be firmly ruled out because of assessments like these:
“there was no significant crush on the honeycomb core”
Even a *relatively* low speed impact would have resulted in crush rathern than tension damage.
Perhaps the landing gear door needs a better explanation (although in two out of three casses of high speed dive/in flight breakup) a landing gear door came off or, at least, nearly so.
The landing gear door could be a good clue, perhaps the best clue, that there was “someone” at the controls at the end.
In the “old days”, standard procedure when executing an emergency descent was to go:
1. throttles idle,
2. depoly speed brake,
3. reduce IAS to gear limit speed,
4. dump the gear (to act as additional airbrakes)
5. push over into rapid descent, controlling speed with pitch.
Procedures (SOP’s) have changed over the years, for a number of reasons, most of them structural, ie, grear doors are not as strong as they used to be (previously robust and aluminium – today mostly composite and far less robust) and it is not done that way today in modern airliners.
However, if I was faced with a rapid descent happening, with the IAS going up alarmingly, and having already pulled power and speed brakes, and it was obvious that the IAS was likely to pass Mmo or Vmo in seconds, and I could not control the speed increase, indeed if the rate of speed increase was itself increasing (ie, the aircraft was accelerating), and I could not stop that trend, or lift the nose without risk of exceeding limit loads and tearing the wings off (assuming one did not grey out in the process), I certainly would, and I think a lot of pilots, (depending on their training (possibly not an airliner pilot ?)) would dump the gear anyway, as the “lesser of two evils” if you will.
Perhaps whoever was at the controls when the second engine flame out occured, and the autopilot diconnected, was not a “sufficiently skilled” pilot, and at some point soon after, he/she simply “lost control”, and it got away from them. They may have “dumped the gear” as their final act ?
Who says the doors were opened at the end of flight ?
And for what purpose ? (I see none).
The landing gear could have been deployed hours earlier in Malaysian airspace.
That would make much more sense.
logical deduction:
If the gear doors were not opened by force (because it’s “unlikely that the gear door could have spontaneously detached in flight, even during a high-speed descent”)
–> then the gear doors must have been opened manually.
–> If the gear doors have been opened manually,
–> the purpose must have been preparation for landing on dry land,
–> since that is the only purpose for deploying the landing gear.
–> If a dry landing was deliberately prepared for,
–> then the (alleged) hour-long flight to an area sans dry landing places (Southern Indian Ocean) cannot have been deliberate,
–> or did not occur.
–> If an undeliberate action (SIO flight) followed a deliberate one (landing attempt),
–> an event must have occurred therebetween preventing the crew from taking deliberate action.
types of such event:
A) unresponsive flight instruments
B) incapacitation
C) loss of consciousness / death
triggers for such event:
A) software malfunction, cyber-hijacking
B) pilot(s) locked out of the cockpit, handcuffed
C) pressure drop, smoke/fire, poison gas, physical attack, murder, dual medical emergency (freak event or both pilots poisoned before take-off)
The onset of this event or a separate, prior event must have prompted the dry landing attempt.
.
Conclusion:
If the debris was not planted but belongs to MH370, and if item#18 (nose gear door) failed under tension (and not impact compression), item#18 can be directly* traced back to a landing attempt on dry land.
*(since the the doors must have been opened to fail under tension and their opening can only have occurred manually)
@Peter
…presumably flying with gear down would be lower speed than observed and fuel consumption would have been too high to hit the inmarsat Arcs as measured.
However, I am not saying nose gear was deployed…that’s just a theory
The fact that there seems to little evidence of compression damage in the debris surely points to a conclusion the plane as a whole did not suddenly decelerate as it would in a high speed vertical dive into water.
In a successful ditch whole body decelerations are relatively low so that compression forces come from things breaking off and hitting something else or from a surface that is acting like a drag brake to slow the plane down and thus experience high face forces.
How would a engine cowling fail in tension … by having the lower circumference in the water and being torn away from the “dry” structure. tension failure at the highest stress point that might not yet be in the water and subject to any face loading.
In a ditch there is water spray and so some parts of the aircraft are subject to a very high pressure hose pipe effect – not at the nose but toward the tail and aft of the wing.
A good ditch has a medium AOA .. high AOA breaks the fuselage and crushes the nose wheel doors as the plane pitches violently down … medium AOA the nose comes down after most of the whole body deceleration has ended. Very low AOA drives the nose of the aircraft into any sea wave and violent deceleration than occurs.
I suggest the evidence best supports a reasonable effective ditch. Left hand side damage because that side happened to touch first …could have been right hand side too if the plane had gone in right wing low.
Ghost flight? how, to an external observer, do you distinguish between a plane on auto-pilot from one flown by an incommunicative, by choice, pilot? You cannot until the plane lands.
Mike G
@ ventus45 “The landing gear door could be a good clue, perhaps the best clue, that there was “someone” at the controls at the end”
It has been suggested that based on the motive previously posted that MH370 ditched in an area between 8°S and 10°S near the 7th arc after an attempt at a landing on Christmas Island which is less than 120nm from the 7th arc.
Could the landing gear still be down after the attempted landing.
This would be consistent with a low AoA ditching and could explain the landing gear door.
@Freddie
“Could the landing gear still be down after the attempted landing.
This would be consistent with a low AoA ditching and could explain the landing gear door.”
Agree in principle.
However, no “sane” pilot, (airline or not), ditches “gear down” unless he had to, ie, could “not” retract the gear.
If the gear was still down after an attempt at CI, then depart CI, he either “forgot” to raise gear (unlikely) or “could not” due no hydraulics.
Therefore, we need an explanation for that.
(1) Which hydraulic system(s) can retract the gear ?
(2) Which engine(s) are “required” to be operating to drive the pumps ?
@ ventus45 “However, no “sane” pilot, (airline or not), ditches “gear down” unless he had to, ie, could “not” retract the gear”
As already mentioned, to fit the 7th arc accurately, the plane had to be “deflected … due to something happening on the flight deck for whatever reason”
If while attempting a landing on CI passenger disruption had taken place it is possible the plane erratically ended up near the 7th arc without retracting the gear.
@ TBill “I always liked your path, and feel it might make a good paper to show 2 flight paths coming off the same root path: one path diverting to Jakarta and a different path diverting to SIO from the same root path, both meeting BFO/BTO.”
I went bush for a few days and have returned to the digitally connected world and just read one of your older posts.
While I much prefer the proposal that the plane turned up towards CI if we are to assume there was some disruption on the flight deck on the way down to Cocos Islands and if constant power settings were maintained til very late in the flight the plane could be between 18°S to 21°S near the 7th arc.
All the BTO’s from 19:41 onwards fit except in some locations there was a need for some slowing in the last hour or so and depending on altitude change towards the end of flight the BFO’s also fit.
Two of the three independent drift analyses with unbiased calculations previously mentioned also fit.
For information, the FWD nose gear doors close after the nose gear is down and locked, opening only for a short period while the gear is in transit. Same goes with the mains.
Manual opening can only be done from the ground for maintenance purposes…
@Russell, That’s extremely interesting.
Thanks @Ge Rijn
How can the doors be closed while the landing gear is deployed ?
Do you have any pictures of that ?
Following up on my posting above, here is the behaviour of the landing gear doors on an Airbus A350. I assume similar behaviour on a B777.
Also interesting:
19 July 2015: “Landing gear panel falls off Boeing 777 into Chinese suburb”
http://bit.ly/2qvkNN2
@Russel M
Your comment:
“For information, the FWD nose gear doors close after the nose gear is down and locked, opening only for a short period while the gear is in transit. Same goes with the mains.”
This is not the case. Look at the @ASLM graphic Jeff incorparated in this topic.
The rear nose gear doors close but the forward doors stay open when the nose gear is deployed.
@ventus45
On your comment:
@ ventus45 “However, no “sane” pilot, (airline or not), ditches “gear down” unless he had to, ie, could “not” retract the gear”
If the goal was to let sink the plane as soon as possible after a ditch it could make sence imo.
The landing gear is designed to shear off first in such a case (crash landing).
The pilot could have known this.
It would cause ruptures in the fuselage and wings but not necessarally break-up of the plane.
An example is Asiane 214. The complete landing gear sheared off during the crash landing but the hull remained mainly structurally intact.
@Russel M
I have to take that statement back. Confused by the ‘fwd’ sign in the graphic pointing to the rear part of the nose gear.
You are right; the FWD doors close after deployment and the rear doors stay open.
This makes it more complicated..
To illustrate:
https://www.flickr.com/photos/timdegroot/sets/72157627502443306/
Looking for a way the forward doors to open after deployement before a ditch/crash landing I see a solution when looking at the @ASLM diagram more closely.
When an extended nose gear would hit the surface during a ditch/crash landing the gear would be pushed backwards and shear off backwards causing the crank and forward door links to push the forward doors open.
I did some further searching.
First the diagram @ASLM provided placed in this topic is the nose gear assembly of a MD11. Not a B777.
Scroll to the bottom of the following page:
http://www.airliners.net/forum/viewtopic.php?t=774103
Here you see a B777 nose gear video when retracting:
https://www.youtube.com/watch?v=AxjEsmVzI_c
And here you see one deployed while on the ground:
http://www.panoramio.com/photo/7296111
Should add the gear doors will remain open after an alternate extension. The system can be reset two ways, not that it matters.
I don’t believe the operation of the gear will help find the aeroplane.
Ge Rijn: Thank you for finding my nose gear illustration error. Sorry for that error. Checking the source, it was labeled B777, but clearly that was wrong.
Here are a few more videos that show the nose gear door operation. The forward doors are only open during the raising or lowering of the gear. They are closed with the gear up and down.
https://youtu.be/AxjEsmVzI_c
https://youtu.be/AHrg4JGHxNI
https://www.youtube.com/watch?v=LRiDTkaJX44 (model of 777)
@Russel M
So the fwd-doors could be also be open with deployed nose gear which is shown in this picture too:
http://marcgeuzinge.photoshelter.com/image/I0000K9KFDtEJqtE
The B777 fwd-doors are not mechanically linked to the rwd-doors like the @ALSM-diagram MD11 nose gear shows.
And I agree the operation of the gear would probably not help to find the plane but it sure would help to find out what happened if it could be proven the plane made a ditch-like impact instead of a high speed impact.
Imo it’s the difference between a pilot controlled impact and an uncontrolled impact.
Further info on nose gear doors and operation…Here are some clips from the B777-200 manuals:
https://goo.gl/B8Lly2
https://goo.gl/ccr0YJ
The fwd doors are closed at all times, except during the brief extension and retraction times.
The fwd doors have hydraulic actuators that operate independently from the read doors, which are mechanically linked to the gear extension actuators.
@ALSM
That’s what a constructive discussion is about isn’t it. Stand corrected when a contribution clearly is not correct, admit it (like you do), and then move on.
I know your point of view on the debris regarding high speed impact.
And you’re not a man scating on one night ice (Dutch saying, hope it rings).
Looking forward to an unbiased as possible report from you on this issue soon.
Ge Rijn: TNX
I have about 35 medium resolution #18 photos to work with. Some are close-up shots that show some random cracks and dents in the material. About half of the grey surface material is “peeled off” from both sides, exposing the mostly carbon fiber layers. There is only one edge intact…about 21″ of the hinged edge. The other 3 edges are all broken. The Debris Examination Report (Updated 30 April 20917) shows the location of the debris relative to a complete gear door. The debris appears to be roughly 25% of a complete rt-fwd door.
I don’t see any conclusive proof, one way or the other, that the gear door separated due to impact or in-flight separation. The only thing that is reasonably certain is that there was no explosion or fire involved with this piece. If the gear door separated in-flight, I would expect it to be more intact, like the flaperon and flap segment. Here we have a piece that is only a small piece of the complete door (~25%). However, there is no indication of compression damage to the honeycomb. There are many places where failure in tension is evident. Tough call.
@ALSM
Any way those photos can be shared? i am a mechanical engineer and i am familiar with the failure mechanism of composite materials. The published photo resolution is clearly low. The more i look at the debris the more it looks like a shallow impact. Was it really at sea? Some debris show force exerced from the top and some significant peel off?
Note that the damage on reunion flaperon really indicate it was retracted. It was a hasty conclusion from the investigators to conclude on that damage that it was a deep dive. And this was used as an evidence to rule out any other possibilities. It was simply retracted. Perhaps this was due to hydraulics failure, perhaps same cause also impacting the landing gear? It would be good for a pilot to explain the emergency steps in case of hydraulics failure.
I am still stunned that there was not a formal forensic examination on the debris.
HB: The photos are for restricted use only. I cannot share them here.
Re: “Note that the damage on reunion flaperon really indicate it was retracted.”. No, it shows that it separated in-flight, before impact. If it was still attached at impact, regardless of attitude, retracted or not, there would have been substantial leading edge compression damage. There was almost none.
@HB, @ALSM, From what I gathered in talking to a source within the investigation, they did do a detailed forensic examination of the debris. However, what they found did not lend itself to any particularly comprehensible scenario. In particular, they did not see evidence that any of the debris separated in-flight.
on what grounds are they restricted ?
@jeff. It would be useful to see what has been done. In principle we only find what we are looking for. Regardless of mid air or not, each debris has its own story and all the storries put together we have a scenario. Has that study tried to determine the angle of impact? With support from modelling simulations? Or was this just a high level qualitative review?
Any link to that study if available would be useful.
@ALSM. Before impact is hard to imagine given the damage to the flaperon mechanism. The impact energy does not look great though i concur
@ALSM
Forgive me if I have missed something here in the above comments. But are we saying the fwd doors of front gear will not retract into a closed position (without hydraulic power) if the gear is manually dropped by gravitational force?
Mick Rooney: Re NLG…I don’t know if there is an alternative way for the front gear doors to be opened/closed in the event of a manual gear extension. The front doors are opened and closed using hydraulic pressure. Once they are in the opened or closed position, they latch and no longer depend on the hydraulic pressure to keep them open or closed. Don T. may know the answer.
Mick you are correct.
From the AMM. I will not post the page image as I have already been issued a telling off for posting to this blog! I apologise it will be long…
Keep in mind the alternate extension system still requires a hydraulic source, which is provided by a power pack operated by 28V from the hot battery bus.
Landing Gear Alternate Uplock Release Actuator
The landing gear alternate uplock release actuator extends to unlock the landing gear uplock. This permits gravity and airloads to extend the gear. The tires may contact the door during alternate extension.
After all doors and gear are unlocked, hydraulic pressure in the alternate extension system increases. When the pressure gets to 2100 psi, the alternate extend hydraulic pressure switch opens. This removes electrical power from the alternate extend control relays. The relays de-energize and remove electrical power from the alternate extend power pack.
Reset
When the alternate extend power pack stops, the alternate uplock release actuator and the door release actuator in the door release/safety valve reset. The springs in the actuators push the hydraulic fluid through the alternate extend power pack and into the oversize supply tube.
The door safety valve in the door release/safety valve module remains in the SAFE position until it is reset. This prevents the door from closing. The door safety valve is reset by an electric signal to the solenoid operated valve. Switches on the P40 and P56 panels, or a switch within the landing gear control lever module provide the reset signal. When the solenoid energizes, the valve permits hydraulic pressure to release the safety valve latch. The reset signal must be made while door close hydraulic pressure is available. When the valve moves to the NORMAL position, the door closes.
General
You can close the landing gear doors with the door close switches or with the landing gear lever. The center hydraulic system supplies the pressure to close the landing gear doors.
MLG and NLG gear door close operation is almost the same.
Door Close Operation
You close the two main landing gear doors at the same time with switches on the P56 wheel well electrical service panel.
You close the nose landing gear doors with switches on the P40 service and APU shutdown panel.
The landing gear lever closes all the landing gear doors only after the gear have retracted. The landing gear door close signal from the landing gear lever goes through a five second time delay relay in the P320 ground handling/service distribution panel. When you move the landing gear lever to the UP position, the solenoids in the door release/safety valve modules get power five seconds later. This delay gives the selector valves time to move to the UP position. This prevents the safety valve from accidental movement to the NORMAL position before the selector valve has time to move. The delay makes sure the door release/safety valve modules are reset by the lever only after the gear retract.
For any door close signal, power from the 28v dc left main bus goes to the solenoid valves in the landing gear door release/safety valve modules.
To close the doors, the door close signal must be made at the same time door close hydraulic pressure is available.
When you use the switches on the P56 panel, the main landing gear doors close in approximately 10 seconds.
When you use the switches on the P40 panel, the nose landing gear doors close in approximately 5 seconds.
Once the door close operation starts, you can not stop the operation with the switches on the remote panels.
@Jeff Wise
“what they found did not lend itself to any particularly comprehensible scenario”
The abscence of a comprehensible scenario tells us, that there was a chaotic and maybe not crash-related situation.
I do not understand a bit about procedures in scrapyards and about the engineering aspects of the debris, but from logic, if i cannot tell a comprehensible scenario from the debris analysis, i would ask myself if the ambigous aspects could happen to take place not in an accident or crash landing, but in the chaotic situation of a scrapping?
Agreed.
On a global scale I still struggle with the “coincidence” (there is no such thing) of an airline losing two of the same aircraft within such a short time frame.
@ Russel M, @Cosmic
… surely Authorities have doubly ensured ALL the identified debris items from MH370 have confirmed, sighted corresponding separate items from downed MH17 – have they not?
@Peter Norton
Does the Nose Gear Forward Door remain open once the landing gear is deployed?
@Nederland
To shime in. The forward nose gear doors only stay open if the landing gear was manualy deployed it seems. For there was no hydraulics left to close them after.
on what grounds are they restricted ?
thank you
It’s sad that the help of qualified people like HB is declined.
It’s not as if help was not needed …
@perfect storm
Nevermind. If malaysia government was interested in finding the plane they will do a robiust anaysis of every clue and evidences. Obviously they have tried to analyse things only fron the point of view to confirm all match with their scenario. What would they have done without Inmarsat data? That is what they should do now.
Regarding MH17, the investigation has been similar, pick one scenario, and make all clues to match that scenario without analysis of other clues. Search for the common cause. Anyway a debris matching could be done with the correct kept data to disprove that same plane scenario, or i hope not to prove it.
I am sure mh370 can be found in KL amongst all the data kept secrets. Given all the elements of possible common causes, The mh370 event should have triggered an indepenent public enquiry to examine all the flaws in the military, investigation, aircraft operation systems but it did not.
That plane will be found and most likely in KL.
@HB: I am with you on some points.
I just don’t understand, for what specific reasons the photographs cannot be shared ?
@Nederland: Since Ge Rijn has answered your question, I prefer not to, as I think he is more qualified.