JetBlue plane's mechanical meltdown sends it 'careering wildly through the skies'

[phoneman]

Probably a dumb question but... How is it that they can't dump fuel?

I can understand with implications noted above that they wouldn't necessarily want to land w/out certain functions, but to stay up in the air 4 hours?

With hydro systems being flaky, I'd think they'd want to address what they could, dump fuel and land as soon as practical.

EDIT: Google, as usual is my friend. I see that a320's cannot dump fuel so I guess that renders my question rather moot.

Why was the plane designed not to be able to dump fuel?

[snydersnapshots]

Why was the plane designed not to be able to dump fuel?

The requirement to dump fuel is related to the climb performance of the aircraft if it should lose an engine. Here it is in a nutshell in this excerpt from the AERO magazine referenced in my earlier post:

"FAR 25.1001 — Requires a fuel jettison system unless it can be shown that the airplane meets the climb requirements of FAR 25.119 and 25.121(d) at maximum takeoff weight, less the actual or computed weight of fuel necessary for a 15-minute flight comprising a takeoff, go-around, and landing at the airport of departure."

If you have a bad case of insomnia or are just so bored that you want to read it sometime, here is a link to FAR Part 25 (aka 14 CFR Part 25). You have the chapter numbers listed above for reference: 25.1001 gives the requirements for the fuel jettison system and 25.119 and 25.121 (and those around them) discuss required performance...climb gradients and such. I don't suggest reading them while in the john (WC/blue-room/bathroom/crapateria or whatever slang term you prefer) because I'd hate to see you hurt when you fell asleep and thus fell off the commode.

[Evan]

"FAR 25.1001 — Requires a fuel jettison system unless it can be shown that the airplane meets the climb requirements of FAR 25.119 and 25.121(d) at maximum takeoff weight, less the actual or computed weight of fuel necessary for a 15-minute flight comprising a takeoff, go-around, and landing at the airport of departure."

Is this to ensure that the plane can execute a missed approach at MTOW-15mins fuel?

[Gabriel]

Is this to ensure that the plane can execute a missed approach at MTOW-15mins fuel?

Yes.

[Evan]

Yes.

So it is structurally safe to land at MTOW-15mins fuel, but not procedurally safe. So if everything is stable you burn off fuel, but if, for instance, a fire breaks out, you take it in knowing you might have to get in down in one.

Question in my head is: for an A320 with four hours of FOB, does it really take three hours to burn off enough fuel to meet the conditions of the FARs?

[Gabriel]

So it is structurally safe to land at MTOW-15mins fuel, but not procedurally safe.

In airplanes that ARE REQUIRED to have a fuel dump system, yes (some airplanes do have the system while they have the performance required to get away without one). Airplanes that are required to have a fuel dump system are also required that such system must be able to bring the plane's weight below the weight needed for the go-around required performance within 15 minutes.

In airplanes NOT REQUIRED to have a fuel dump system, it is both structurally safe to land at MTOW and "go around" safe to do it at MTOW -15 minutes.

So if everything is stable you burn off fuel, but if, for instance, a fire breaks out, you take it in knowing you might have to get in down in one.

In an airplane with fuel dump system, if you badly need to land, you dump system while you return to land. You land at whatever low weight you have managed to get.

In an airplane without a fuel system, you return and land period.

In bot cases, a point can be made that the pilot should check whether the weight is "MTOW-15" before going too low during the approach, or he might be unable to go-around if needed.

However, if the emergency is very severe (like a fire), I personally would risk having to go around with less than 100% of the the minimum required climb performance (that will still be a positive climb).

Question in my head is: for an A320 with four hours of FOB, does it really take three hours to burn off enough fuel to meet the conditions of the FARs?

Even taking-off at MTOW, any plane meets the FAR requirements for landing weight as soon as it initiates the take-off run and the FAR requirements for go-around performance at most 15 minutes after that (in planes that require fuel dump system, that includes dumping fuel during those 15 minutes).

[Evan]

In airplanes that ARE REQUIRED to have a fuel dump system, yes (some airplanes do have the system while they have the performance required to get away without one). Airplanes that are required to have a fuel dump system are also required that such system must be able to bring the plane's weight below the weight needed for the go-around required performance within 15 minutes.

In airplanes NOT REQUIRED to have a fuel dump system, it is both structurally safe to land at MTOW and "go around" safe to do it at MTOW -15 minutes.



In an airplane with fuel dump system, if you badly need to land, you dump system while you return to land. You land at whatever low weight you have managed to get.

In an airplane without a fuel system, you return and land period.

In bot cases, a point can be made that the pilot should check whether the weight is "MTOW-15" before going too low during the approach, or he might be unable to go-around if needed.

However, if the emergency is very severe (like a fire), I personally would risk having to go around with less than 100% of the the minimum required climb performance (that will still be a positive climb).


Even taking-off at MTOW, any plane meets the FAR requirements for landing weight as soon as it initiates the take-off run and the FAR requirements for go-around performance at most 15 minutes after that (in planes that require fuel dump system, that includes dumping fuel during those 15 minutes).

So... why did they circle here for three hours? Not to meet landing weight requirements. To work the problem? I assume they could get through the checklists and prepare everything in under one. The green system was lost, but it is not needed. The yellow system seems to have simply been a transient overheat due to the PTU and I expect that it would have been restored by then. I'm sure there are other complications. It will be interesting to read the report of this one.

[Gabriel]

Ok, maybe I oversimplified.
There are TWO maximum landing weights required by the FAR.
The MLW and the MTOW.

The FAR requires for a landing MLW that the plane "survives" a harder landing that at MTOW (which is still more than your usual hard landing), so there is more "regulatory"(*) margin when landing at MLW than at MTOW.

Additionally, a landing above MLW:
- Can overheat the brakes
- Requires an overweight landing inspection (that could be as simple as plugging a laptop in a port and checking the landing Gs)
- There is more fuel to feed a fire in case of an accident
- Landing 8and crashing) speeds are higher
- Loads on the tyres/landing gear are higher
- More runway is needed

Because of all that, a balance is made between advantages/disadvantages of an overweight landing, depending on the type of emergency. When there is urgency to land, you land at whatever weight with the peace of mind of knowing that the plane is designed to do so (but maybe with a tad more of caution than usual to avoid a too hard landing).

Fire is an obvious case. Double hydro failure too. And so is engine failure in a twin.

At the other extreme of the spectrum, you have landings for which you would probably not only burn enough fuel to be below the MLW, but you'd probably want to land with minimum weight fuel. An example could be a gear-up landing.

In the middle, you have an assortment of problems for which the situation is not that severe that you feel the need (or the procedures call) to land ASAP but you also don't feel like crossing the Atlantic ocean (or getting far from the airport) in that condition. In those cases you burn or dump fuel to get to the MLW. A single hydro failure seems to fall in this group.

(*) Believe or not, sometimes a landing at MLW can put higher loads on parts of the structure than an MTOW landing, so you'd have more margin at MTOW than at MLW, although both would be more than the margin required by the MLW landing.

[JJR]

I probably missed it 5 or 6 times, but what was the tail # for JBU194 that day?

[UncleFire]

Here it is:

http://www.youtube.com/watch?v=RftOD_O7Taw

http://www.youtube.com/watch?v=9ffJgk1-tCA

Flying out of Phoenix I hear the 2nd version pretty much every flight (on Air Bus A/C). Upon landing not as often IIRC.

I rarely hear it in flight and that 1st one didn't sound good at all.

I compare it to the sound of a hand-saw being used on wood.

[MCM]

Question in my head is: for an A320 with four hours of FOB, does it really take three hours to burn off enough fuel to meet the conditions of the FARs?

Thats a very interesting question. More interesting is "does it take 3 hours to get below maximum landing weight".

Gabriel has summarised it quite well.

At the end of the day, there is a weight at which you can land the aircraft, and a normal maximum landing weight. Obviously very different things.

For a start, I'd suggest there are very few aeroplanes around these days which *require* a fuel dump system. Many have them - but don't necessarily require them.

Its also a case of balancing risk. Back to what pilots are paid to do. What is the greater emergency/risk? If you are on fire, down to your last electrical generator etc, then the risk associated with not landing is greater than the structural risk to the aeroplane.

Loss of one hydraulic system? Not a reason to land overweight (unless other considerations apply). In many cases you would continue your flight. However, having probably been startled by the problem with the second hyd system in this case, the crew made the decision that while they still had two hyd systems (no reason to land immediately), it was probably a good idea to remain near an airport where they could put it on the ground immediately if they got any signs they were losing the second system again. Pretty smart really.

Again, it depends on the aeroplane. The A380 has specific provision for overweight landings in certain circumstances. Other aeroplanes really don't like it. At the end of the day, as long as it is a "normal" landing very little will usually have to be done to clear the aircraft for further flight. In some cases, nothing. Max landing weights are usually about maintenence inspection times and longevity of the parts. Case in point: you can often "buy" higher max takeoff and landing weights from manufacturers.

[Gabriel]

Gabriel has summarised

Gabriel and summarized in the same sentence. Right.

Case in point: you can often "buy" higher max takeoff and landing weights from manufacturers.

Please explain that:
"Hello, Boeing? How much the 767's extra MTOW pound?"
"$ 9.99 each"
"Ok, I want 3,000 of them"
"Would you like to side your extra miles with a combo of updated manuals and software for just $ 4,999?
"Yes, please"
"Here you have, and that would be, hmmm, $ 34,969. Enjoy!"

[MCM]

Gabriel and summarized in the same sentence. Right.

Well, this time it was a pretty good effort at a "summary" .

I don't think any of us around here are ever particularly concise . At least we've all been floating around here for long enough to basically know what each other is going to reply before we even write our own post

I would suggest that the "sides" of completion of certain mods, increased engineering inspections etc would be the expensive part.

But I wasn't joking - thats why you'll find different airlines with different maximum take off weights. Operate a lower MTOW, get approval for lower maintenance costs etc etc. You'll even find different takeoff weight variants within the same airline. Hell, you can even find the same actual aeroplane with different MTOWs approved based on an engineering decision on the day!

[Evan]

"Here you have, and that would be, hmmm, $ 34,969. Enjoy!"

I don't think Boeing will even sell you a wing-nut for that price.