Hey JB, I was reading this article about a Jetblue flight that had hydraulic troubles and this caught my eyes "Because the A320 is incapable of dumping excess fuel, the pilots circled the area south of the Vegas Strip until they’d burned enough to allow the crippled plane to land safely."
Am I correct in thinking that not being able to dump excess fuel when needed is a limitation that shouldn't exist?
There isn't very much in the A320 article to really let me know what happened. The loss of two hydraulic systems is extremely unusual, and historically has been the result of something nastier. Passenger comments are so inaccurate as to be pretty much worthless, so it's pretty difficult to read much into what they said. Yaw damper issues could lead to some quite uncomfortable, but not dangerous, motion, which is possibly what they felt.
Looking through various forums on this incident, it seems they actually lost one system, and had an overheat on the other; a dramatically different position to losing two.
I think you'd be surprised at just how few aircraft have fuel dumping systems. In most cases it is not a regulatory requirement, and the vast majority of the narrow bodied aircraft are not so fitted. Even if you have a dump system, it doesn't mean you can dump all of the fuel. Whilst a 747 will let you dump down to about 6 tonnes remaining, on the A380, you'll still have about 80 tonnes of fuel at the end of the dump (and so would be about 30-40 tonnes above max landing weight). The 767s that I've flown had about a 50% fit of a dump system.
The thing you have to remember is that 'max landing weight' IS NOT the maximum landing weight. It is simply the maximum for normal operations, at a defined impact rate (basically an unflared landing at 700 fpm). Believe me, that would be the hardest landing you've ever felt...even VERY HARD landings rarely exceed about 400 fpm. In the A380 you can land at up to max take off weight, as long as the impact rate is less than 360 fpm (most landings are in the 50-100 fpm area). So, the landing itself is not really an issue. In the A380, the vast majority of medical diversions would also include an overweight landing.
The problem comes up when you need to couple a heavy weight landing with other problems. For instance, issues with slats/flaps, brakes, or spoilers, would all lead you to desire the minimum weight possible. But, the regulations that aircraft are built to, don't normally include compounding emergencies (otherwise you could make it so hard that nothing would ever fly). My personal position is that all aircraft should be able to dump all of their fuel. The reality is that that isn't how they are built.
Flying around for a few hours, whilst getting the aircraft to a lighter weight isn't really an issue. If anything, it slows things down in the coughpit, which is probably a good thing. Even if you are in an aircraft that can dump fuel, you're probably still looking at 60-90 minutes for the dump to occur. Even at dump rates it takes a long time to get rid of the very large loads carried by some aircraft. In this particular case, the A320 could have been landed at any time during that 3 hours...