Airbus Invents Turning By Fuel?
 

I was looking at the New Scientist magazine and saw this. For me, it's nonsense. You'd need to be lucky enough to not run out of fuel before you find a place far away enough to land, needing miles and miles to line up the aircraft. Not forgetting pitching down during a bank, and pitching up upon roll-out. How on earth could such a system be conceived?

PILOTS are trained how to fly their aircraft if an engine or other flight systems fail, but what if they lose control of the steering?

Now Airbus has come up with a way for pilots to fly a plane to the nearest runway in even these extreme circumstances.

In a US patent filed last week, Airbus says damaged aircraft could be controlled by moving fuel quickly between fuel tanks in the wing, fuselage and tail, shifting the centre of gravity to provide rudimentary steering.

This could easily be achieved, Airbus says, by programming flight management software to include fuel-based steering among its emergency options. If the pilot needed to roll to the left, the system would pump fuel to the left wing's tank. To pitch the nose up, fuel could be pumped to the tank in the tail.

Link: Airbus invents steer-by-fuel emergency system - 08 April 2009 - New Scientist

(It's not April fools, like I thought it was).

It's not as farfetched as it sounds. A similar system has been used for trim -- in Concorde for example -- and pilots have used differential engine thrust to steer a plane with no hydraulics. Sure the response isn't going to be quick but when it is all you have you'll try it.

I read this in Flight International I think it was and they said that it could even be used instead of the flight control surfaces during normal operations as it would reduce aerodynamic drag due to sticking bits of aileron and the like into the airstream - and thanks to fly by wire it could be all done using the normal systems.

Whether or not it is implemented, it will certainly take quite some time - interesting idea though!!

FF

I think New Scientist must have got their dates mixed up. The same issue had an article about human echo-location which I am convinced is an April 1st story...

Is cg movement not how one steers a hang glider?

Patent??
 

That's how for God's sake ORVILLE maneuvered.

PRIOR ART!!!!!

And the fundamental principles of flight have been in place for how long ? Not to mention the millions (billions) of [insert favourite currency] that have been pumped into aerodynamic R&D over the same period of time !

If such a fundamental change were possible, it would have happened by now ! Sure as a trim / emergency / whatever thing .... but for everyday use, I'll keep my ailerons thanks ! For those doubters .... one word .... BA38.


When were you last on a longhaul flight as pax Cosmos2 ? :cool:

I saw this guy on a news show who did echo-location. Unless they were lying about his blindness, I'm not sure how he could fly down a city street on a skate board. Yes the US Navy was interested.

I looked him up: Ben Underwood. There's also a wiki article.

Moving fuel would have to be done extremely quickly and in the right amounts for sufficient effect. The issue is the fugoids that inevitably emerge in any aircraft without the use of flight controls, especially swept wing configurations. Most Airbus pilots have done the "complete loss of hydraulics" drill and had to land the simulator using engine and mechanical horizontal stab trim alone. I spoke with someone at Airbus (former FAA) and he said he'd done it in the airplane and it wasn't that hard, (although the landing was, he said). We practised it in the 330/340 but not to the landing. The Sioux City DC10 crew had a very difficult time with the fugoid oscillations and learned quite quickly how much lead/lag they needed in terms of engine thrust. The whole point is, one must do exactly that...lead and lag the controlling inputs. If it's too early, too much, too late or not enough, the fugoids slowly become unstable and loss of control will eventually result. With computer control and such factors built-into the algorithms, it may work but shifting fuel manually to control the airplane would be, I think, damn near impossible to accomplish and execute to a safe landing. I call April Fool, but the idea may only be ahead of it's time and the joke will be on us!

Is it any nuttier than landing an a/c without any flight controls?

THAT has saved a big Scarebus out in Iraq (or similar- no loss of life).

And The guys who lived through the Sioux City crash
NASA came up with a scheme (widely shown on TV) where 'NO CONTOL' landings in a MD-11 became routine.

Trust Airbus to come up with their own 'FBW' version of it!:8

Kind of, but because the wing is flexible it's more to do with altering wing loading and "billow shift" than actual C of G. :ok:

PJ2;

Do you mean phugoid?
In the DC-10 SIM it is controllable to a landing. And it is a very realistic SIM.

In the DC-10 SIM it is controllable to a landing.

(a) I don't think that we are fussed too much as to how anyone might wish to spell things ..

(b) sim fidelity will be very much a case of how the box is modelled, set up, and tweaked

(c) Al Haynes made no secret of the fact that the boys didn't have much of an idea of what was going on in the beginning .. without knowing the jargon, they figured out how to get some control over the phugoid

(d) if it hadn't been for the phugoid oscillation's catching them coming in over the fence .. they might have just got away with a landing rather than rolling themselves into a ball. As Haynes observed in the Dryden presentation -

We were starting a down phugoid, and starting a right bank, 300' in the air. And we just, that's where our luck ran out.

An intelligent directional and vertical profile flight control mechanism using differential thrust was officially in the works after a famous accident involving loss of hydrualics (not Sioux City incidently). FAA ran trials and this system was tested successfully, however it all got brushed under the carpet after the true cost came to light.

This would be a far better bet than moving fuel around IMO.

I have tried several times in the A320 SIM, to fly overhead the airport at 10.000`/ speed 250 kts and then remove all hydraulic power (= no flightcontrols and no stab trim)

It is a very good learning experience and a "confidient builder" to see that the aircraft is quite easy to control and steer only using asymmetric engine thrust. The trick to learn is the lead/lack of thrust.

On the first try, I landed the aircraft on the center of the runway, and one dot low on the localizer. Quite hard landing though, but suviveable. Try it next time you have time to spare in the sim.

It would though be a very scary thing to do real life, and it reminds me that e.g. Sioux City and Bagdad A300 "No flight controls landing" both were MUCH MUCH more of an extraordinary performance when compared to the Hudson River landing, which I think most 40 hour PPL could have pulled of just as good.

Greetings
PJ2 Phugoids are oscillations, most like to occur around 15 17 deg pitch, so I dont see the point related to turning with fuel :}

Entirely feasable idea.

I like it.

We used to have lots of fun on the nimrod getting the back end crew to all run to the front or the back together while new FO's were hand flying close to max height to weight.

kijangnim;
First, the assumption here is loss-of-all-flight-controls, usually due to loss of all hydraulics. I can't really conceive of a situation where control in pitch is available but not in roll. And if that's the case there are other, perhaps less elegant or at least imaginative ways of turning an airplane - a small, momentary deflection of rudder (same amount as yaw-damping, roughly), particularly in a swept-wing aircraft, will do nicely.

Next, I understand your point and phugoid oscillations quite clearly. The point was made in the first post by the thread-starter - turning affects pitch; this is also acknowledged in the NS article. It was this problem, not turning, (by whatever means), that I was considering. This is precisely the problem that Sioux City illustrated. All pilots know that turning will cause the nose to drop - my thought was, how is that to be controlled through fuel movement? The article mentions pumping fuel to and from the tail. Obviously not at present rate capabilities!

I don't think it's that simple, having flown the sim using only stab trim and engines. While such a fuel transfer system is common in transport aircraft, it would have to be done with a great deal of flexibility in terms of rate, timing and amount, and, I submit, it would have to be computer-controlled but those are details - it is the idea I'm interested in. I am assuming by your comments that you know phugoid oscillations can destabilize if one is not careful with the airplane. Despite what some say about it being a piece of cake, the success rate is not stellar. It was to the notion of how to keep it stable that I was directing my comments. Clearly there are other issues such as design, testing, manufacture, certification, maintenance which are yet to be addressed.

Greetings,
I see your point, and what I know about phugoid oscillation, is that it takes place at high pitch angle (during windshear recovery for example) and to give an image, it is as if the airplane was suspended to a huge spring, the oscillation will induce unwanted load factors.
As you said technology is easy to visualize, but dam hard to implement, how ever the idea is great, and needs to be investigated in depth :ok:

As deltayankee already said, the basic notion is at least 40 years old - see Concorde, where it was used to minimise trim drag when the CofL moves aft significantly during the transition from subsonic to supersonic.

Do subsonic airliners have fwd and aft (tail) trim tanks?
Can existing fuel pumps move fuel fast enough to obtain any kind of long and lat control? (IIRC a typical fuel pump moves about 2t/min.)

If the answer to either question is 'no', I would suggest the idea is stillborn: nobody is going to carry the additional weight of tanks, pipes, and beefed-up pumps, for a one-in-a-million + occurrence, i.e., totally loss of any other form of control.

CJ

Perhaps Airbus are thinking not in terms of current configs but in terms of less conventional future configurations where fuel shift for trim may be more usual and thus the capability may be more available than on a standard "tube with wings"?

ChristianJ;
The Airbus A330 and A340, all series, (and I suspect the A380) all have fuel tanks in the horizontal stabilizer for the same purposes - trim in cruise. The tanks are empty at takeoff and landing, (IOW, not used for storage). The smaller A320-type do not have such a system.

The B777 (the versions I have data on) do not have such trim tanks, nor does the B767 series.

Your second question re transfer rates was the point I was trying to make - present systems could not transfer fuel at rates which would be required to turn the airplane and control the other forces inherent in such maneuvers. I think it is wholly impractical. Perhaps the Mad Scientist is onto something though...

From what I know, super sonic aircrafts eg. fighters use the movement of fuel for maneuvering during supersonic flight.

I think your missing the novelty
 

Why pump a small amount of Fuel a long way to increase the Moment Arm? Why not move the entire Tank a few centimeters instead? Adding rails and tractor jacks would solve the "Rate" problem by moving all the Fuel in the Tank instantly, a short distance.

I have to agree however with Christiaan who questions the attention paid to a small chance risk. There was that -10 that lost its exhaust cone from #2 last month, however. No interruptions in that one, but a stage or two forward.......?

Following on from that, why not add a device, maybe somewhere at the back where it would be most effective, which could be moved by remote control from the flight deck (or by autonomous command from the flight computers) producing an aerodynamic force which could counterbalance any tendency towards instability?

Pedant head on.

The Stab trim tanks often contain fuel when it leaves the gate. I can't see 2tonne (plus) of JetA1 being used before takeoff. I may be wrong though.

and what I know about phugoid oscillation

.. with respect, kijangnim, I think that you need to revisit a basic undergrad engineering text in Mechanics of Flight and review what the phugoid solution represents.

I suspect that you are a tad wide of the mark in your comments.

PJ2: The Airbus A330 and A340, all series, (and I suspect the A380) all have fuel tanks in the horizontal stabilizer for the same purposes - trim in cruise.

Thanks! I presume that translates to: "On long-range a/c, the reduction in fuel burn due to reduced trim drag, more than compensates for the added weight of tanks and pumps" ?

9v-SKA: From what I know, super sonic aircrafts eg. fighters use the movement of fuel for maneuvering during supersonic flight.

No, they don't. Movement of fuel is used for trim, not manoeuvering. You cannot move fuel fast enough to get an adequate response to control inputs.

airfoilmod and FullWings,
Thanks... ROFLMAO :D

TURIN,
Concorde typically used about 1.3t from gate to line-up, so the much heavier 'biggies' may well use 2t (I've got no figures either).
On Concorde we could "overfill" the tanks (i.e., above MTOW) and hence arrive at th line-up at exactly MTOW.

john_tullamarine ...the phugoid solution...

I have the impression most people are not really aware of what the phugoid is, because under normal circustances the amplitude is so small and the period so large, that either small control inputs or autopilot tend to mask its existence.

CJ

I've been trying to work out how much weight you can shift in a few seconds using normal plumbing and I can't help feeling that a little fat guy running up and down the aisles might be faster.

cg movement
 

To Mad (Flt) Scientist.

All right then, I will bite! Yes indeed, cg movement is how you steer a hang glider. But Turin is right also. Load up left wing by moving to that side, increase billow and the drag on the left wing, therefore turn left.

AND you can land a hang glider (but no other fixed wing non VTOL aircraft) with zero kinetic energy.

Excuse me while I polish my tinfoil helmet!

Nice one....
100kg fat guy running from tail to centre of cabin (assuming no trolley dolleys or trolleys in the way) is 100kg over about 25m in 10 seconds.
2t/min from tail tank to centre tank is 330kg in 10 seconds. Slightly better.
You'll have to get the fat lady to run as well.

CJ

The NS article has very little information (online, haven't seen the latest edn in the shops here yet)...does anyone have a link to the actual patent application?

There is an art to patents and the use "controlling aircraft by pumping fuel around" is not the core of the patent application but rather the way you express the ideas that make up the claims of the patent. Therefore I guess that Airbus have some clever techniques linking fuel pump operation with the control systems for much more sophisticated and subtle trim than is achievable by the pilots controlling the fuel flow between tanks. In addition to that this patent might really come down to some novel device that sits between the fuel pumps and the FBW system...

Looks interesting and would love to see more of the details

fc101
E145 Driver

TURIN;

I took a look at a fuel sheet I kept, (134,000kgs) and indeed the Trim Tank was loaded with 5050kgs of juice so my recollection is incorrect - fuel is in the TTs at takeoff. If I recall correctly, the TT is empty (or supposed to be) by the time descent begins. Amazing the details one forgets after a year and a bit of retirement!

ChristianJ;
Fully agree. I think most people don't comprehend the nature of phugoid oscillations in transport category aircraft; the mass is substantial (ranging from 50,000 to 400,000kgs approx) therefore the "stasis" (inertia) in cruise flight (700 to 1000fps or so) is significant - the cycle takes time to develop, it takes great anticipation (lead/lag of control input) and careful control handling to stop. Otherwise, one's input is liable to exacerbate the cycle, not stop it. In terms of Dutch Roll, one firm opposite aileron into the roll usually works, but that's not a phugoid. The entire cycle is, as you observe, subtle to begin with.

Having seen large fuel imbalances across the wing in different types and the relative insigificance of such weight differences in terms of controllability, I think any fuel redistribution to intentionally roll the aircraft has marginal aerodynamic and mechanical viability. I can imagine the aircraft beginning to roll "as commanded" and a rapidly-developing need to transfer fuel back to stop the developing roll - again, it would have to be very subtlely done and certainly not by the crew - the airplane would likely simply roll on it's back under manual control unless one is extremely good, careful and experienced at handling these aircraft.

Greetings everyone
I am leaving PPRUNE, good luke everyone.

Why?????:confused:

that either small control inputs or autopilot tend to mask its existence.

.. can recall some Argosy pilots years ago who couldn't work out why the aircraft had speed oscillations on autopilot during cruise .. a short brief on phugoids sorted that out.

Trim
 

To me the phugoid is similar to a natural tendency for the a/c to roll. The cure for uncommanded roll is Dihedral. There is no similar solution for pitch linked excursions. Except for constant inputs balancing Center of lift and cg. There is no natural tendency for an aircraft to seek stable pitch in flight without a designed interruption of deviation. So many of the current crop of accidents involve Pitch, the design arena is so far inadequate to taming this most important characteristic.

An Idea
 

First thought about turning with fuel was ahh B.S. The trim tanks on several aircraft have a long time to transfer fuel and it could never be accomplished for sucessful flight.

Reasoning.

1. the obvious fuel transfer is slow
2. quantity changes depending on phase of flight, how do you calculate it to a specific quantity when a pilot would probable prefer to land heavy with plenty of missed approach fuel... many variables here.
3. we have spent years creating bafflels and fuel schedules to prevent fuel from effecting the aircraft's flight chararistics.

The last problem may be the solution, what if the plan is not to pump fuel from tank to tank but to simply allow gravity to do it's job within that tank when desired and pump it in the opposite direction when not. Complex, probably never know when it is broken until you need it (like a dump valve) but completely possible.

How about them "phugoid oscillations"?

Wing Loading
 

And then there's wing loading. The wings lift most of the mass of the a/c, including fuel load. The largest stress on the wings is at T/O, when heavy.
Assumably, Wing tanks will be carrying fuel on T/O. With less than full fuel at T/O, the wings should still contain fuel, as the portion of TOW represented by fuel is better managed when its weight is directly borne above the Lift.
An empty wing stresses (bends more) when asked to leverage all weight when it is empty of fuel. Cruise, same. Splitting the mass (Fuel) at the fulcrum, the wing root, reduces stress and adds life to the wing structure.
But this hasn't anything to do with turning. An increase aft in cg allows the tail to support more mass also, reducing AoA at cruise, reducing drag, increasing fuel efficiency, also nothing to do with turning with Fuel apportionment.


AF

My endeavour to question the need for such a patent. The whole thing seems counter intuitive. Why move the Fuel inboard after landing, outboard after T/O? In any case, nowhere did I infer an asymmetric Fuel storage in my post.