So what's a slam-dunk?

[llondel]

In the Asiana thread over in rumours, there's mention of the SFO slam-dunk.

Any chance of a description of what exactly this is? I assume it's basically an instruction to get from A to B in a hurry and requiring a bit of skill.

[Guest 112233]

A description for a relatively high altitude (for the circumstances) close in (track mile limited, edit perhaps) visual approach while maintaining continuous visual contact with the runway.

An additional factor being the kinetic and potential energy of the aeroplane i.e. the combination of velocity and height.

No doubt the experts will elucidate us on the exact points.

It requires a lot of skill (one time PA28 student) - Especially for modern airliners.

[wiggy]

It's a case of having to get down from A to B in a hurry....

Basically it's where ATC keep you high until very close in to the runway ( well above the ideal 300 feet per mile rule of thumb), and then release you for the approach..usually then involves you throwing the gear and landing flap out, idle power, some /all speedbrake and hoping you can get back down onto the ideal profile before you need to have the power spooled up (normally 1000' agl)..think of how a basketball slam dunk looks and you'll get the idea.

Fairly standard at SFO, especially flying up the bay for a right hand pattern for a landing to the west, where adjacent airfields force a tight traffic pattern.

P.S Sorry CAT III, I think our posts crossed...

[Guest 112233]

Well put - Oakland International Airport is in the general vicinity.

I neglected the configuration changes required in a hurry - this adds a lot to the air crew's workload. Sorry.

[ceeb]

I'm only a PPL so wouldn't know this but can the heavy jets side slip to lose height quickly?

[llondel]

I'm only a PPL so wouldn't know this but can the heavy jets side slip to lose height quickly?

It has been done - the Gimli Glider had to do that when it arrived too high to land, too low to orbit and lose height. I don't think it's a recommended procedure in something that size though, but in the absence of any other solution, better than nothing.

[llondel]

Thanks to wiggy and CATIII-NDB for the clarification of slam-dunk. I see someone's asked the same question on the R&N thread now :)

[Armchairflyer]

I'm only a PPL so wouldn't know this but can the heavy jets side slip to lose height quickly? As already stated, it has been successfully done in one instance, but this was an emergency with a loss not only of engine power but of hydraulics for extending the flaps or speed brakes, too. Some arguments against "regular" side-slipping that immediately come to my armchairflyer mind (ready to stand corrected/amended as always):
- passenger discomfort!
- potential for compressor stall
- stress on airframe (from airflow side load and/or very rapid pressure change)
- precise navigation during the sideslip(?)

[BBK]

It's not an unreasonable question and the answer, at least regarding the 744, is that it's not recommended. The concern is over causing structural damage. That taken from the FCOM ie "flight manual". I suppose in an emergency if losing height is essential then maybe it is warranted.

As Wiggy points out, the "slam dunk" at SFO refers to being kept high on a downwind right hand pattern and then turned in well above the normal glideslope. It makes for a challenging manoeuvre especially at the end of a long flight. Also, you often have to fly an offset if you are landing 28R to avoid conflicting with any traffic approaching 28L. Still, the compensation is having a layover in lovely San Francisco. :)