It’s possible, but best not to if you can avoid it; doing so means a higher speed at touchdown (due to higher stall speed because of high weight) and a longer decel (due to higher speed and higher mass), and also means that a mistake when flaring is more likely to overload the landing gear.
In the case you mentioned (hadn’t heard of it), apparently they apparently didn’t need to land Right This Minute, so it was safer to burn off a bunch of fuel and lighten their load before touchdown.
**Machine Elf **nailed it.
Here’s some more detail / background …
There is a regulated max landing weight for normal day to day use. And it’s significantly less than max regulated takeoff weight.
But we can physically safely land at regulated full-up max takeoff weight. And there’s a regulatory special case for doing so when you have a darn good reason as Steve Martin might have said.
So-called “overweight landings” then require a maintenance inspection to ensure nothing was overstressed. And we need not to prang it on, lest something be overstressed & perhaps break. Autoland systems aren’t certified for those weights, so it has to be done manually.
Brakes and tires (and runways really) are sized for landing at the normal landing weights. Since Kinetic Energy goes up at the square of the speed, an extra 20% of landing speed to offset the extra weight means dissipating an extra 44% of KE. That excess eats into the margins that give brakes and tires their economic lifespans.
Each flap setting has a maximum speed limit that if exceeded may cause overstress. Exceeding a limit also requires a maintenance inspection and perhaps parts replacement, or something may even bend or break in flight which would be Very Bad.
The slowest you can fly at each flap setting before stalling goes up as you get heavier. For very heavyweight situations you can get into a near Catch-22 where your max safe speed for a particular flap setting is only a couple knots above your min speed for the same configuration. In gusty conditions you’re essentially assured of violating one limit or the other.
So landing overweight is *not *a white-knuckle, “Gosh Jim I hope she holds together” scenario. But it *is *operating in the area where we can spend a lot of employer money and create a multi-hour delay or flight cancellation with less than near-perfect handling. So it’s something to be entered into soberly with some respect.
Any time you’re considering landing overweight, the situation is already non-standard. Something has gone wrong. If that something also affects stopping capability adversely, but doesn’t much interfere with flying, and is unlikely to deteriorate further over time, you may have a good reason to circle to burn or dump fuel rather than land overweight *and *with degraded stopping.
Much to many folks’ surprise, reducing the supply of fuel for a potential post-landing fire has just about zero to do with the decision tree. It’s all about weight & stopping distance & not burning up brakes or ending up off the far end of the available runway.
Looking at p. 11 of the report on Air Transat 236 (PDF), it was in fact the emergency brake accumulators that saved them:
Total stopping distance after the second touchdown, with the wheels locked and rapidly eroding away, was about 4800 feet.
Thanks LSLGuy, and Machine Elf.
Sweet photo of main gear: see Figure 2, page 11 at your link. :eek: