787 First Flight - Signs of Trouble Ahead?
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Can we get this straight? Are we talking about aileron 'droop' or 'upfloat'? Upfloat I can understand. But I do find it extraordinary that a correspondent thinks he has spotted design flaws from a company like Boeing on a maiden flight. Arrogance in misplaced self-confidence! He could have asked rather than approach the issue so negatively (and make a plonker of himself!).
Note that I am not suggesting that this deflection is an inadvertant result of a design flaw - quite the opposite. In modern aircraft it is possible to intentionally use ailerons, flaps spoilers in various combinations to alter spanwise loading. I was simply observing that it looks like they are doing that to reduce the load envelope for early testing. My question was why they need to protect the envelope to that extent.
If making an observation and bothering to question 'why?' with a few fairly rational supporting statements makes me a 'Plonker' as you so eloquently state, then I will wear that badge with pride.
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Rumor Merchant,
I believe the point Rainboe was trying to make, was that your original post seemed to focus on the negative, rather than the positive. Your own post title reaffirms this; "787 First Flight - Signs of Trouble Ahead?"
Plonker....
I believe the point Rainboe was trying to make, was that your original post seemed to focus on the negative, rather than the positive. Your own post title reaffirms this; "787 First Flight - Signs of Trouble Ahead?"
Plonker....
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It is still not clear what you mean, what does 'deflected negative' mean? Deflected down? That would not be right at all. I assume it means 'upfloat'? The reasons for that are well documented. Your first post was full of innuendo that Boeing had made some design error with wing and aileron design. Anyone famliar with later 737s, 747s and 777s will be familiar with the new wing design preference and the reasons for wing bending. Inflight, the 737 wingtips are looking at each other over the top of the fuselage. A simple question would have extracted an answer for you instead of 2 paragraphs devoted to a possible Boeing design disaster area, which is utter nonsense.
A magnificent looking plane with real technical innovation. It will make a fitting partner to the A380 for the heavy stuff for the next generation.
A magnificent looking plane with real technical innovation. It will make a fitting partner to the A380 for the heavy stuff for the next generation.
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Signs of trouble ahead! .. I saw a Clio with a fat exhaust that converts petrol to noise.. maybe Renault should recall them all...Whilst the debate on flight controls and aerodynamic forces is worthy of a thread, I agree with Rainboe, let's not descend into nonsense and speculation
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Refering to your original post, RumourMerchant69:
Correct me if I am wrong, but your suggested load alleviation would not change anything on the bending moment on the wing root!
If you deflect the ailerons upward, the loss of lift on the outer wing has to be compensated by the inner part - the resulting bending moment on the root is exactly the same! With your suggestion you can only change the bending moment over the wing spar(s).
If Boeing had planned to ease the load on the wing-fuselage connection, a reduction in takeoff weight would have helped them - instead they reportedly took 10 tons of water ballast on board.
Correct me if I am wrong, but your suggested load alleviation would not change anything on the bending moment on the wing root!
If you deflect the ailerons upward, the loss of lift on the outer wing has to be compensated by the inner part - the resulting bending moment on the root is exactly the same! With your suggestion you can only change the bending moment over the wing spar(s).
If Boeing had planned to ease the load on the wing-fuselage connection, a reduction in takeoff weight would have helped them - instead they reportedly took 10 tons of water ballast on board.
Originally Posted by BarbiesBoyfriend
Might just have been the camera angle but to me it looked like the wings were really curved, almost as if they were a bit too flexible.
Yep, the wing flexes as designed.
What else did you expect?
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Where do you get these ideas RumourMerchant?
I'd think that Boeing probably have a better idea of how to design a wing than you, unless of course there is something you're not telling us (are you about to roll out a new intercontinental passenger jet from your garden shed?)
Regardless, as the saying goes, if it looks right it'll fly right, and it sure looks right! I'm a little dissapointed they changed the tail from the original concept, but the aircraft as a whole looks great - it reminds me of a glider, which I suppose is the point!
BHDH.
I'd think that Boeing probably have a better idea of how to design a wing than you, unless of course there is something you're not telling us (are you about to roll out a new intercontinental passenger jet from your garden shed?)
Regardless, as the saying goes, if it looks right it'll fly right, and it sure looks right! I'm a little dissapointed they changed the tail from the original concept, but the aircraft as a whole looks great - it reminds me of a glider, which I suppose is the point!
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the wings are designed to flex.
At max load (around 4 G's) they will deflect 26 feet.
The first flight was all about testing controls and check
for flutter which one can imagine can be a risk
with such an extreme bending wing.
At max load (around 4 G's) they will deflect 26 feet.
The first flight was all about testing controls and check
for flutter which one can imagine can be a risk
with such an extreme bending wing.
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Am surprised 411A hasn't joined the fray....the good old Tristar 500 had ailerons that I believe were offset upwards for take off? Also had a Load Allieviation Function like the A320 etc. But 787 looks great in flight was good to see the landing on the web cast.....a winner worth waiting for?
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Correct me if I am wrong, but your suggested load alleviation would not change anything on the bending moment on the wing root!
If you deflect the ailerons upward, the loss of lift on the outer wing has to be compensated by the inner part - the resulting bending moment on the root is exactly the same!
If you deflect the ailerons upward, the loss of lift on the outer wing has to be compensated by the inner part - the resulting bending moment on the root is exactly the same!
s centre of lift inwards and reduces the bending moment, and reduces the wing flexing moment allowing a lighter structure. The VC10 used to take it off at 24,000'- I don't know if the 787 does the same. It also helps prevent adverse aileron drag in a roll as the downgoing aileron initially moves into the general wing shape whilst the upgoing aileron initiates a downforce immediately. So no adverse yaw in a turn if you design it right.
Rather than aerodynamics, a more interesting discussion would be on the technical aspects of this aeroplane. Presumably 2 (BIG!)alternators per engine plus ELRAT? Has everything ended up being electric- no hydraulics? Obviously all planned, but single engine raising of the gear with aircon packs, and maybe flaps being raised AND tailplane being trimmed? Quite an immense demand! I expect ALL the lights would go out, and galleys load shed! And how do the brakes work? I have never seen electrical wheel brakes. Feel must be totally artificial. I just can't see how the electrical demand can all be handled at high workload times. All you need is those fancy pants screens suddenly going 'blue screen of death' on you! But I know Mr. Boeing knows his planes!
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They don't address your electrical questions, Rainboe, but these nuggets from the Rockwell Collins news release do give some insight:
Rockwell Collins serves as the systems supplier for the Boeing 787 flight deck display system, crew alerting system, pilot controls, communication and surveillance systems, and the core network cabinet. Rockwell Collins also provides the common data network for the airplane's Common Core System..
Rockwell Collins serves as the systems supplier for the Boeing 787 flight deck display system, crew alerting system, pilot controls, communication and surveillance systems, and the core network cabinet. Rockwell Collins also provides the common data network for the airplane's Common Core System..
- An integrated display system featuring five 15.1-inch diagonal LCD displays, as well as dual LCD head-up displays (HUD). The Rockwell Collins Head-up Guidance System (HGSTM) provides the most advanced display capabilities available in the air transport market, including primary flight, advanced navigation and complete crew alerting functionality. The system utilizes cursor control devices and a multi-function key pad for data entry and retrieval.
- The latest generation of pilot controls with a control stand that includes auto throttles, and pitch, roll, yaw and primary flight controls, as well as their interfaces to the aircraft's fly-by-wire systems. The modular design of the pilot controls will simplify installation and maintenance. This new system meets Boeing's objective of providing operators with a look and feel similar to the Boeing 777, while achieving significant weight savings.
- The Core Network, offered as standard on the 787, which plays a key role in Boeing's objective to 'e-enable' the entire aircraft. Utilizing commercial open standard computing servers and networks, the Core Network hosts a wide range of third-party applications and manages onboard information flow to improve airline operational efficiency.
- The Common Data Network (CDN), which advances Rockwell Collins' leadership as a supplier of advanced networking technologies. As a key component of the 787 Common Core System, the CDN is a high integrity, bi-directional fiber optic and copper network that uses ARINC 664 protocols and standards to manage the information flow between the aircraft's onboard systems. Based on commercial Ethernet technology adapted to the avionics environment, the integrity and deterministic characteristics of Rockwell Collins' CDN allows systems integrators to utilize this network for systems requiring a high level of data criticality. The CDN offers significant improvements over current generation data buses including expanded connectivity, higher data rates and significant reductions in aircraft weight when compared with point to point topologies...
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Rainboe is right, for a given total lift the bending moment at the root is reduced if the lift distribution is moved inboard.
The 787 has a 2E/3H architecture. It has three hydraulic networks (Left - engine-driven pump and electric (demand?) pumps, same for Right, Centre driven by two electric pumps). Each engine has two 250 (!) kVa starter/generators, the APU has two 220 kVa starter/generators. The RAT provides both hydraulic (to Centre system) and electric power.
Because of all the various electrical loads it has a 230Vac network, a 270Vdc network, a 115Vdc network and a 28Vdc network.
Spoilers and stabilizer actuator can be electrically driven following a full hydraulic loss, making the 787 controllable in the event of losing all ship-wide hydraulics (like the A380). The brakes are electrically driven.
A potential issue for airlines, because the engines are started using the electrical starter/generators you need a lot of power to get them going. If the APU is u/s you need three good GPUs to start an engine.
The 787 has a 2E/3H architecture. It has three hydraulic networks (Left - engine-driven pump and electric (demand?) pumps, same for Right, Centre driven by two electric pumps). Each engine has two 250 (!) kVa starter/generators, the APU has two 220 kVa starter/generators. The RAT provides both hydraulic (to Centre system) and electric power.
Because of all the various electrical loads it has a 230Vac network, a 270Vdc network, a 115Vdc network and a 28Vdc network.
Spoilers and stabilizer actuator can be electrically driven following a full hydraulic loss, making the 787 controllable in the event of losing all ship-wide hydraulics (like the A380). The brakes are electrically driven.
A potential issue for airlines, because the engines are started using the electrical starter/generators you need a lot of power to get them going. If the APU is u/s you need three good GPUs to start an engine.
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Ok I will try and clear things up a bit (again). My 'outrageous speculation' of structural problems is not speculation at all - it is in the public domain.
News article about repairs work prior to first flight, this was due to de-lamination observed during the static testing performed in 2008:
No verdict yet on completed tests to 787 wing repairs - SmartPlanet
Note the quote "The aircraft did go to limit load as intended" however at that point analysis was still ongoing. I certainly haven't found anything more recent about the results of the test. It is possible to perform the first test flight even if the results were not that favourable (after all you are not going to come anywhere near limit load on your first test flight), but the authorities will almost certainly ask you to demonstrate that the flight envelope is being limited to mitigate the risk.
Flying at reduced weight and limiting the types of manoeuvres performed can help limit the envelope, particularly for structure where the critical load cases are the manoeuvre load cases, but for areas driven by gust cases it can be much more difficult to protect in this way. In fact adding ballast in the wings can help mitigate for this by increasing inertia and providing some bending relief. Another way to protect for the gust cases is to keep the wing inboard loaded to reduce the bending moment.
Now maybe you can understand why my observation that negative aileron deflection (yes negative means up - thats the convention) may have been employed to inboard load the wing. This would reduce the bending moment at the root joint and hence the load at the crown fittings (these are effectively transferring the bending moment into the centre wingbox structure as a couple of two running loads - compressive at the top skin joint and tensile at the bottom skin joint.) If you reduce the bending moment you reduce the load on these fittings.
I am not suggesting there is any new problem, just that the use of load alleviation may be a symptom of a well known existing problem, and was wondering if anyone had any 'information' that might better explain the aileron position at takeoff. You will note my post title was "signs of trouble ahead?" not "signs of trouble ahead!" There is a very big difference.
I am in no way trying to belittle the achievement - the 787 is a beautiful aircraft, and a revolution in systems and structure design and manufacture, and will certainly be a great success. My question was really around whether the use of alleviation suggests that there may be further delays before first delivery, or if there is another explanation.
Note that I do not think the wing deflection is a design flaw - it is a design feature, and a beautiful one at that.
News article about repairs work prior to first flight, this was due to de-lamination observed during the static testing performed in 2008:
No verdict yet on completed tests to 787 wing repairs - SmartPlanet
Note the quote "The aircraft did go to limit load as intended" however at that point analysis was still ongoing. I certainly haven't found anything more recent about the results of the test. It is possible to perform the first test flight even if the results were not that favourable (after all you are not going to come anywhere near limit load on your first test flight), but the authorities will almost certainly ask you to demonstrate that the flight envelope is being limited to mitigate the risk.
Flying at reduced weight and limiting the types of manoeuvres performed can help limit the envelope, particularly for structure where the critical load cases are the manoeuvre load cases, but for areas driven by gust cases it can be much more difficult to protect in this way. In fact adding ballast in the wings can help mitigate for this by increasing inertia and providing some bending relief. Another way to protect for the gust cases is to keep the wing inboard loaded to reduce the bending moment.
Now maybe you can understand why my observation that negative aileron deflection (yes negative means up - thats the convention) may have been employed to inboard load the wing. This would reduce the bending moment at the root joint and hence the load at the crown fittings (these are effectively transferring the bending moment into the centre wingbox structure as a couple of two running loads - compressive at the top skin joint and tensile at the bottom skin joint.) If you reduce the bending moment you reduce the load on these fittings.
I am not suggesting there is any new problem, just that the use of load alleviation may be a symptom of a well known existing problem, and was wondering if anyone had any 'information' that might better explain the aileron position at takeoff. You will note my post title was "signs of trouble ahead?" not "signs of trouble ahead!" There is a very big difference.
I am in no way trying to belittle the achievement - the 787 is a beautiful aircraft, and a revolution in systems and structure design and manufacture, and will certainly be a great success. My question was really around whether the use of alleviation suggests that there may be further delays before first delivery, or if there is another explanation.
Note that I do not think the wing deflection is a design flaw - it is a design feature, and a beautiful one at that.
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Issues
I can only see one real issue with this aircraft - lightning protection. Seems the FAA have relaxed their criteria for lightning resistance in line with the expected performance of the composite structure of this aircraft. I wonder if this might come back to haunt them?
I am not suggesting there is any new problem, just that the use of load alleviation may be a symptom of a well known existing problem, and was wondering if anyone had any 'information' that might better explain the aileron position at takeoff. You will note my post title was "signs of trouble ahead?" not "signs of trouble ahead!" There is a very big difference.
RumourMerchant69, are these signs he is a dishonest coward?
See how it works? I'm just asking an innocent question.
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It is possible to perform the first test flight even if the results were not that favourable (after all you are not going to come anywhere near limit load on your first test flight), but the authorities will almost certainly ask you to demonstrate that the flight envelope is being limited to mitigate the risk.
the new wingbox design. The "2C test" exceeded the 100% load (2,5G) which
is required by the FAA for first flight.
They recreated the conditions that led to the delamination this summer.
The ultimate 150% load test is expected spring 2010.
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When they did the same test on the B727 the wings nearly met over the hull before they snapped, then it could be heard all over the airfield!
Did the A380 pass this test first time round?
We are in danger of being somewhat blinkered here, new material, a different picture altogether, not at all reasonable to compare the visual image of the 787 wing stress test with wings not constructed from the same material or to the same design.
Did the A380 pass this test first time round?
We are in danger of being somewhat blinkered here, new material, a different picture altogether, not at all reasonable to compare the visual image of the 787 wing stress test with wings not constructed from the same material or to the same design.